Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations
2000 The tuds y of reactive intermediates: p- Quinodimethanes and 3-methylene-1,4-pentadiene Steven Paul Lorimor Iowa State University
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Bell & Howell Information and Learning 300 North Zeeb Road, Ann ArtX}r, Ml 48106-1346 USA 800-521-0600
The study of reactive intermediates:
p-Quinodimethanes and 3-methylene-l,4-pentadiene.
by
Steven Paul Lorimor
A dissertation submitted to the graduate faculty in partial flilfilhnent of the requirements for the degree of
DOCTOR OF PHILOSOPHY
Major: Organic Chemistry
Major Professor: Walter S. Trahanovsky
Iowa State University
Ames, Iowa
2000 UMl Number 9990474
UMI^
UMl Microfomfi9990474 Copyright 2001 by Bell & Howell Information and Learning Company. Ail rights reserved. This microform edition is protected against unauthorized copying under Title 17, United States Code.
Bell & Howell Infomnation and Learning Company 300 North Zeeb Road P.O. 80x1346 Ann Arbor, Ml 48106-1346 11
Graduate College Iowa State University
This is to certify that the Doctoral dissertation of
Steven Paul Lorimor has met the thesis requirements of Iowa State University
Signature was redacted for privacy.
Signature was redacted for privacy.
Signature was redacted for privacy.
For tne-Qraduate College iii
I dedicate this dissertation to my wife, Jeanette, and my son, Nicholas. Their continual love, sacrificial support, and constant encouragement made this work possible and meaningful. I thank them for all that they have done. IV
TABLE OF CONTENTS
LIST OF FIGURES x
LIST OF TABLE xxiii
LIST OF ABBREVL\TIONS AND EXPLANATIONS xxiv
GENERAL INTRODUCTION 1
Dissertation Organization 2
CHAPTER L REGIOSELECTIVITY OF DIELS-ALDER REACTION 3 OF 3-iVIETHYLENE-l,4-PENTADIENE, THE SIMPLEST CROSS-CONJUGATED TRIENE
Abstract 3
Introduction 3
Results 7
Discussion 10
Conclusion 12
Experimental Section 13
Methods and Materials 13
l,5-Diacetoxy-3-(acetoxyniethyl)pentane (4) 13
3-Methylene-1,4-pentadiene (1) 13
Methyl 4-Vinyl-3-cyclohexenecarboxylate (5), Methyl 15 3-Vinyl-3-cyclohexenecarboxyIate (6), and 4-VinyI-3-cyclohexenecarboxylic Acid (7)
References 17
Appendix 19
CHAPTER 2. LITERATURE REVIEW OF SIMPLE BENZENE-BASED 40 /7-QUINODIMETHANE'S V
Introduction 40
Pyrolytic Preparation 44
Non-Pyro lytic Preparation 52
Direct Observation 54
Summary 55
References 55
CHAPTERS. ROOM TEMPERATURE OBSERVATION OF 62 /;-XYLYLENES BY 'H NMR AND EVIDENCE FOR DIRADICAL INTERMEDL\TES IN THEIR OLIGOMERIZATION
Abstract 62
Introduction 62
Results 68
p-Xylylene (1) Oligomerization Studies 68
a-Methyl-/7-xylylene (11) Oligomerization Studies 71
2,6-DimethyI-p-xylylene (12) Oligomerization Studies 78
p-Xylylene (1) and 2,6-Dimethyl-p-xyIyiene (12) 81 Co-oligomerization Studies
Discussion 83
p-Xylylene (1) Oligomerization Studies 83
Zwitterionic Intermediates 84
a-Methyl-p-xylylene (11) Oligomerization Studies 85
2,6-Dimethyl-/?-xyIyIene (12) Oligomerization Studies 85
/7-Xylylene (1) and 2,6-Dimethyl-p-xylyIene (12) 87 Co-oligomerization Studies vi
Conclusion 87
Experimental Section 89
Methods and Materials 89
4-[(Trimethylsilyl)methiyl]benzoic Acid 89
4-[fTrimethylsilyl')methyl]benzyl Alcohol 89
[p-((Trimethylsilyl)methyl)phenyl]methyl Acetate (13) 90
Drying and Initial Degassing of CD3CN 90
/7-Xylylene (1) in Degassed CD3CN 90
'•"C NMR Spectrum of 1 at -40°C 91
p-Xylylene (1) in Deoxygenated CD3CN 92
/7-Xylylene (1) in Oxygenated CD3CN 92
4-[(Trimethylsilyl)methyl]benzaldehyde 93
1 -[p-((T rimethylsily l)methy Opheny1] ethano1 9 3
l-[p-((Trimethylsilyl)methyl)phenyl]ethyl Acetate (15) 93
a-Methyl-;7-xylylene (11) in Degassed CD3CN 93
a-Methyl-/7-xylylene (11) in Deoxygenated CH3CN 94
Isophorone Oxime 95
3',4',5'-Trimethylacetanilide 95
3,4,5-Trimethylamline 95
3,4,5-Trimethylbenzonitrile 95
3,4,5-Trimethylbenzoic Acid 95
3,5-DimethyI-4-[(trimethylsilyl)methyI]benzoic Acid 96 vii
3.5-DimethyI-4-[(trimethyIsilyl)methyl]benzyI Alcohol 96
[3,5-Dimethyl-4-((trimethylsilyl)methyl)phenyl]methyl Acetate 96 (19)
2.6-Dimethyl-/7-xylylene (12) in Degassed CD3CN 97
p-Xylylene (1) and 2.6-Dimethyl-p-xvlylene (12) in Degassed 97 CD.CN
References 98
Appendix 102
CHAPTER 4. EFFECTS OF a-PHENYL AND a-METHYL SUBSTITU- 172 TION ON THE STABH^ITY OF p-XYLYLENES
Abstract 172
Introduction 172
Results 175
p-Xylylene (1) Long-term Kinetics Studies 175
a-Methyl-/7-xylylene (4) Long-term Kinetics Studies 178
p-Xylylene (1) Short-term Kinetics Studies 181
Generation and Oligomerization of a-Phenyl-p-xylylene (8) 183
Generation and Oligomerization of a,a-Diphenyl-p-xylylene (6) 186
p-Xylyiene (1) with Air Kinetics Studies 192
Determination of Rate Constants 195
Discussion 196
Conclusion 199
Experimental Section 200
Methods and Materials 200 viii
Drying and Initial Degassing of Acetonitrile-^/i and Methylene 200 Chioride-J?
/7-XyIylene (1) Long-term Kinetics 201
a-Methyl-/7-xylylene (4) Long-term Kinetics 201
p-Xylylene (1) Short-term BCinetics 202
4-[(TrimethyIsilyI)methyl]benzhydroI (17) 202
(4-[.(Trimethylsilyl)methyl]phenyl)phenylmethyl Acetate (15) 203
a-Phenyl-p-xylylene (8) Kinetics 203
a-Phenyl-p-xylylene (8) Oligomers 204
Methyl 4-[(Trimethylsilyl)methyI]benzoate (21) 205
(4-[(Trimethylsilyl)methyl]phenyl)diphenylmethanol (22) 205
(4-[(Trimethylsilyl)methyl]phenyl)diphenylmethyI Benzoate (19) 205
a,a-DiphenyI-p-xylylene (6) Kinetics 206
a,a-Diphenyl-/7-xyIyIene (6) Oligomers 206
/j-Xyiylene (1) with Oxygen Kinetics 207
References 208
Appendix 210
CHAPTER 5. EVIDENCE FOR THE GENERATION OF 243 /7-DIPHENOQUINODIMETHANE
Abstract 243
Introduction 243
Results 246
Preparation of Precursor to p-Diphenoquinodimethane (5) 246 Lx
Reaction ofp-Diphenoquinodimethane (5) with Oxygen. 247
Oligomerization of/j-Diphenoquinodimethane (5) 249
Discussion 251
Conclusion 254
Experimental Section 254
Methods and Materials. 254
p-Tolylboronic Acid (14) 255
Methyl 4'-Methyl-4-biphenylcarboxylate (10) 255
iV,iV-Diisopropyl-4-[4'-((trimethylsilyl)methyl)phenyl]ben2- 255 amide (11)
iV,A^-Diisopropyl-4-[4'-((trimethylsiIyl)methyl)phenyl]benzyl- 256 amine (16).
(4-[4'-((Trimethylsilyl)methyl)phenyl]benzyl)diisopropylmethyl 256 ammonium Iodide (13)
Oxygen Trapping ofp-Diphenoquinodimethane (5). 257
Oligomerization ofp-Diphenoqiunodimethane (5). 257
References 258
Appendix 261
GENERAL CONCLUSION 285
ACKNOWLEDGEMENTS 287 X
LIST OF HGURES
'H NIvIR spectrum (300 MHz, CDCl,) of l,5-diacetoxy-3-(ace- 20 toxymethyOpentane (4).
NMR spectrum (75.47 MHz, CDCL) of 1,5-diace- 21 toxy-3-(acetoxymethyl)pentane (4).
'H NMR spectrum (300 MHz, CD,C1, and CCIJ of 3-methyl- 22 ene-l,4-pentadiene (1)
'H NMR spectrum (300 MHz, benzene-JJ of 3-methyl- 23 ene-l,4-pentadiene (1).
'^C NMR spectrum (75.47 MHz, CD,C1, and CCIJ of 3-methyI- 24 ene-l,4-pentadiene (1).
'^C NMR spectrum (75.47 MHz, benzene-JJ of 3-methyI- 25 ene-l,4-pentadiene (1).
HETCOR spectrum (benzene-t/J of 3-methylene-l,4-pentadiene 26 (1).
Expansion of Figure A-7. HETCOR spectrum (benzene-tfj of 27 3-methyIene-l,4-pentadiene (1).
'H NMR spectrum (300 MHz, CDCL) of methyl 4-vinyI-3-cyclo- 28 hexenecarboxylate (5) and methyl 3-vinyl-3-cyclohexenecar- boxylate (6).
'^C NMR spectrum (75.47 MHz, CDCL) of methyl 4-vin- 29 yl-3-cyclohexenecarboxylate (5) and methyl 3-vinyl-3-cyclo- hexenecarboxylate (6).
'H NMR spectrum (400 MHz, CDCLj) of 4-vinyl-3-cyclohex- 30 enecarboxylic acid (7).
Expansion of Figure A-11. 'H NMR spectrum (400 MHz, CDCL) 31 of 4-vinyl-3-cyclohexenecarboxylic acid (7). xi
Figure A-13. '^C NMR spectrum (100 MHz, CDCL) of 4-vinyl-3-cycIohex- 32 enecarboxylic acid (7).
Figure A-14. HETCOR spectrum (CDCL) of 4-vinyl-3-cyclohexenecarboxylic acid (7).
Figure A-15. Expansion of Figure A-14. HETCOR spectrum (CDCL) of 34 4-vinyl-3-cyclohexenecarboxylic acid (7).
Figure A-16. COSY spectrum (CDCL) of 4-vinyl-3-cyclohexenecarboxylic 35 acid (7) with H'-* & H'"" interaction with H^and interaction with H^ & H-" highUghted.
Figure A-17. COSY spectrum (CDCL) of 4-vinyl-3-cyclohexenecarboxylic 36 acid (7) with H^ & H-*" interaction with H' highlighted.
Figure A-18. COSY spectrum (CDCL) of 4-vinyl-3-cyclohexenecarboxylic 37 acid (7) with H' interaction with H"and H' interaction with H^'' highlighted.
Figure A-19. COSY spectrum (CDCL) of 4-\inyl-3-cyclohexenecarboxylic 38 acid (7) with H® interaction with H- highlighted.
Figure A-20. 'H NMR spectrum (400 MHz, CD,CL) of methyl 4-\inyl-3-cyclo- 39 hexenecarboxylate (5).
CHAPTERS
Figure 1. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress of 69 p-xylylene (1) in degassed CD3CN.
Figure 2. 'H NMR spectrum (400 MHz, CD.CN) of /7-xylylene (1) and 72 oligomerization products in oxygenated CD.CN.
Figure 3. 'H NMR spectrum (400 MHz, CD3CN) of/?-xylylene (1) products 73 in deoxygenated CD3CN.
Figure 4. 'H NMR spectrum (400 MHz, CD3CN) of a-methyI-/7-xyIylene 75 (11) in degassed CD3CN. a-Methyl not shown.
Figure 5. 'H NMR spectrum (400 MHz, CD3CN) of product mixture of 76 a-methyl-p-xylylene (11) in degassed CD3CN. xii
Figure 6. NMR spectrum (400 MHz, CD3CN) of product mixture of 77 a-methyl-p-xylylene (11) in deoxygenated CD3CN.
Figure 7. NMR spectrum (400 MHz, CD3CN) of 2,6-dimethyl-p-xyl- 80 ylene (12) in degassed CD3CN.
Figure 8. ^H NMR spectrum (400 MHz, CD3CN) of product mixture of 81 2,6-dimethyl- /?-xylylene (12) in degassed CD3CN.
Figure 9. 'H NMR spectrum (400 MHz, CD3CN) of p-xylylene (1) and 82 2,6-dimethyl- /?-xylylene (12) in degassed CD3CN.
Figure 10. 'H NMR spectrum (400 MHz, CD3CN) of product mixture of 83 p-xylylene (1) and 2,6-dimethyl- /j-xylylene (12) in degassed CD3CN.
Figure A-1. 'H NMR spectrum (400 MHz, CD.CN) of 4-[(trimethylsilyl)meth- 109 yl]ben2oic acid.
Figure A-2. 'H NMR spectrum (400 MHz, CDCL) of 4-[(trimethylsilyl)meih- 110 yljbenzoic acid.
Figure A-3. '^C NMR spectrum (100 MHz, CD.CN) of 4-[(trimethyIsil- 111 yl)methyl]benzoic acid.
Figure .A-4. 'H NMR spectrum (400 MHz, CD.CN) of 4-[(trimethylsilyI)meth- 112 yl]benzyl alcohol.
Figure .A-5. 'H NMR spectrum (400 MHz, CDCL) of 4-[(trimethylsilyl)meth- 113 yljbenzyl alcohol.
Figure .A-6. '^C NMR spectrum (100 MHz, CD.CN) of 4-[(trimethylsil- 114 yl)methyl]benzyl alcohol.
Figure .A-7. 'H NMR spectrum (400 MHz, CD.CN) of [p-((trimethylsil- 115 yl)methyl)phenyl]methyl acetate (13).
Figure A-8. '^C NMR spectrum (100 MHz, CD.CN) of [p-((trimethylsil- 116 yl)methyl)phenyl]methyl acetate (13).
Figure A-9. HETCOR spectrum (CD.CN) of [j7-((trimethylsilyl)methyl)phen- 117 yl]methyl acetate (13). xiii
'H NMR spectrum (400 MHz. CD.CN) ofp-xylylene (1) in 118
degassed^ CD.CN.J
Enlargement of Figure A-10 from 12 to -0.7 ppm. 'H NMR 119 spectrum (400 MHz, CD.CN) ofp-xylylene (1) in degassed CD.CN.
'H NMR spectrum (400 MHz, CD.CN) of reaction progress of 120 /j-xylylene (1) in degassed CD.CN.
'H NMR spectrum (400 MHz, CD.CN) of [2.2]paracyclophane 121 (3) and [2.2.2]paracyclophane (14).
'^C NMR spectrum (100 MHz, CD.CN) of/j-xylylene (1) with 122 Cr(acac)..
Enlargement of Figure A-14 from 230 to -10 ppm. '^C NMR 123 spectrum (100 MHz, CD.CN) of p-xylylene (1) with Cr(acac)..
Enlargement of Figure A-14 from 145-110 ppm. ''C NMR 124 spectnmi (100 MHz, CD.CN) of/j-xylylene (1) with Cr(acac)..
'H NMR spectrum (400 MHz, CD.CN) of/?-xylylene (1) and 125 oligomerization products in oxygenated CD.CN.
Enlargemeni of Figure A-17 from 11.5 to -1.8 ppm. 'H NMR 126 spectrum (400 MHz, CDjCN) of/7-xylylene (1) and oligomerization products in oxygenated CD.CN.
'H NMR spectrum (400 MHz, CD.CN) of products ofp-xylylene 127 (1) and oxygen.
Enlargement of Figure A-19 from 12 to -0.7 ppm. 'H NMR 128 spectrum (400 MHz, CD.CN) of products of /?-xyIyIene (1) and oxygen.
'H NMR spectrum (400 MHz, CD.CN) ofp-xylylene (1) products 129 in deoxygenated CD3CN. xiv
Enlargement of Figure A-21 from 12 to -0.7 ppm. 'H NMR 130 spectrum (400 MHz, CD.CK) of/)-xylylene (1) products in deoxygenated CD.CN.
'H NMR spectrum (400 MHz, CD.CN) of 4-[(trimethyIsilyl)meth- 131 yljbenzaldehyde.
'H NMR spectrum (400 MHz, CDCl.) of 4-[(trimethylsilyl)meth- 132 yijbenzaldehyde.
'C NMR spectrum (100 MHz, CD.CN) of 4-[(trimethyIsil- 133 yl)methyl]benzaldehyde.
'H NMR spectrum (400 MHz, CD.CN) of l-[/?-((trimethyIsil- 134 yl)methyl)pheny1] ethano I.
'C NMR spectrum (100 MHz, CD.CN) of l-[p-((trimethylsil- 135 yl)methyl)phenyl]ethano 1.
'H NMR spectrum (400 MHz, CD.CN) of l-[/7-((irimethylsil- 136 yl)methyl)phenyl]ethyl acetate (15).
'C NMR spectrum (100 MHz, CD.CN) of l-[/7-((trimethylsil- 137 yl)methyl)phenyl]ethyl acetate (15).
'H NMR spectrum (400 MHz, CD.CN) of a-methyl-p-xylylene 138 (11) in degassed CD.CN.
Enlargement of Figure A-30 from 12 to -0.7 ppm. 'H NMR 139 spectrum (400 MHz, CD.CN) of a-methyl-/j-xylylene (11) in degassed CD.CN.
Enlargement of Figure A-30 from 8-6 ppm. 'H NMR spectrum 140 (400 MHz, CD.CN) of a-methyl-p-xylylene (11) in degassed
CD.CN.J
Enlargement of Figure A-30 from 6-4 ppm. 'H NMR spectrum 141 (400 MHz, CD.CN) of a-methyl-p-xylylene (11) in degassed CD.CN. XV
Figure A-34. Enlargement of Figure A-30 from 4 to -0.5 ppm. 'H NMR 142 spectrum (400 MHz, CD.CN) of a-methyl-/7-xylylene (11) in
degassedO CD.CN.J
Figure A-35. 'H NMR spectrum (400 MHz, CD.CN) of reaction progress of 143 a-methyl-p-xylylene (11) in degassed CD3CN.
Figure A-36. Enlargement of Figure A-35 from 8^ ppm. 'H NMR spectrum 144 (400 MHz, CD.CN) of reaction progress of a-methyl-p-xylylene (11) in degassed CD.CN.
Figure A-37. 'H NMR spectrum (400 MHz, CD.CN) of pentane extraction of 145 product mixture of a-methyl-p-xylylene (11) in deoxygenated
CD.CN.J
Figure A-38. Enlargement of Figure A-37 from 7.5-6.0 ppm. 'H NMR 146 spectrum (400 MHz, CD.CN) of pentane extraction of product mixture of a-methyI-/7-xylylene (11) in deoxygenated CD.CN.
Figure A-39. Enlargement of Figure A-37 from 4-0 ppm. 'H NlvIR spectrum 147 (400 MHz, CD.CN) of pentane extraction of product mixture of a-methyl-p-xylylene (11) in deoxygenated CD.CN.
Figure A-40. 'H NTVIR spectrum (300 MHz, CDCI3) of isophorone oxime. 148
Figure A-41. 'H NMR spectrum (300 MHz, CDCI3) of 3',4',5'-trimethyIacet- 149 anilide.
Figure A-42. •'^C NMR spectrum (75.4 MHz, CDCI3) of 3',4^5'-t^imethylacet- 150 anilide.
Figure A-43. Infrared spectrum of 3',4',5'-trimethylacetanilide. 151
Figure A-44. 'H NMR spectrum (300 MHz, CDCI3) of 3,4,5-trimethylaniline. 152
Figure A-45. '^C NMR spectrum (75.4 MHz, CDCI3) of 3,4,5-trimethylaniline. 153
Figure A-46. Infrared spectrum of 3,4,5-trimediylaniline. 154
Figure A-47. Infrared spectrum of 3,4,5-iriniethyIbenzonitrile. 155 xvi
'H NMR spectrum (400 MHz, CDCL) of 3,4,5-trimethyIbenzoic 156 acid.
'^C NMR spectrum (100 MHz, CD.CN) of 3,4,5-trimethylbenzoic 157 acid.
'H NMR spectrum (300 MHz, CDCI3) of 158 3,5-dimethyl-4-[(trimethyIsilyI)methyl]benzoic acid.
'H NMR spectrum (300 MHz, CDCI3) of 159 3.5-dimethyl-4-[(trimethylsilyl)methyl]benzyI alcohol.
'H NMR spectrum (400 MHz, CD.CN) of [3,5-dimethyl-4-((tri- 160 methylsilyl)methyl)phenyl]methyl acetate (19).
'^C NMR spectrum (100 MHz, CD.CN) of [3,5-dimethyI-4-((tri- 161 methylsilyl)methyl)phenyl]methyl acetate (19).
'H N'MR spectrum (400 MHz, CD.CN) of reaction progress of 162 2.6-dimethyI-p-xylylene (12) in degassed CD.CN.
Enlargement of Figtire A-54 from 9-4 ppm. 'H NMR spectrum 163 (400 MHz, CD.CN) of reaction progress of 2,6-dimethyI-/7-xyl- ylene (12) in degassed CD.CN.
Enlargement of Figure A-54 from 4-1 ppm. 'H NMR spectrum 164 (400 MHz, CD.CN) of reaction progress of 2,6-dimethyl-/j-xyl- ylene (12) in degassed CD.CN.
Enlargement of Figure A-54 from 6.75-6 ppm (After 4 Days 165 only). 'H NMR spectrum (400 MHz, CD.CN) of reaction progress of 2,6-dimethyl- p-xylylene (12) in degassed CD.CN.
GC chromatogram of the pentane extraction of product mixture of 166 2,6-dimethyl- /7-xyIylene (12) in degassed CD.CN.
'H NMR spectrum (400 MHz, CD.CN) of pentane extraction of 167 product mixture of 2,6-dimethyl-/7-xyIylene (12) in degassed CD3CN. xvii
Figure A-60. Enlargement of Figure A-59 from 4—0 ppm. 'H NMR spectrum 168 (400 MHz, CDjCN) of pentane extraction of product mixture of 2,6-dimethyl-/7-xylyIene (12) in degassed CD.CN.
Figure A-61. 'H NMR spectrum (400 MHz, CDjCN) of reaction progress of 169 p-xylylene (1) and 2,6-dimethyl-p-xylylene (12) in degassed CD3CN.
Figure A-62. Enlargement of Figure A-61 from 9-4 ppm. 'H NMR spectrum 170 (400 MHz, CD3CN) of reaction progress of /?-xylylene (1) and 2,6-dimethyl-/?-xylylene (12) in degassed CD3CN.
Figure A-63. 'H NMR spectrum (400 MHz, CD3CN) of pentane extraction of 171 product mixture of/7-xylylene (1) and 2,6-dimethyl-p-xylylene (12) in degassed CDjCN.
CHAPTER 4
Figure I. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for 176 long-term kinetics experiment of />-xylylene (1) in deoxygenated CD3CN.
Figure 2. Plot of In [1] vs time for long-term kinetics experiment. 177
Figure 3. Plot of [1]-' vs time for long-term kinetics experiment. 177
Figure 4. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for 179 long-term kinetics experiment of a-methyl-/J-xylylene (4) in deoxygenated CD.CN.
Figure S. Plot of In [4] vs time for long-term kinetics experiment 180
Figure 6. Plot of [4]-' vs time for long-term kinetics experiment. 180
Figure 7. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for 181 short-term kinetics experiment ofp-xylylene (1) in degased CD3CN.
Figure 8. Plot of In [1] vs time for short-term kinetics experiment. 182
Figure 9. Plot of [1]-' vs time for short-term kinetics experiment. 182 xviii
Figure 10. NMR spectmm (400 MHz, CD3CN) of reaction progress for 184 kinetics experiment of a-phenyI-/?-xylyiene (8) in degased CD3CN.
Figure 11. Plot of In [8] vs time for kinetics experiment. 185
Figure 12. Plot of [8]-' vs time for kinetics experiment. 185
Figure 13. NMR spectrum (400 MHz, CD;C!;) of ethyl acetate extracted 187 TLC spot of a-phenyl-p-xylylene (8) products.
Figure 14. Mass spectrum (EI) of ethyl acetate extracted TLC spot of 188 a-phenyl-p-xylylene (8) products.
Figure 15. NMR spectrum (400 MHz, CD2CI2) of reaction progress for 189 kinetics of a,a-diphenyl-/>-xyIylene (6).
Figure 16. Plot of In [6] vs time for kinetics experiment. 190
Figure 17. Plot of [6]-' vs time for kinetics experiment. 190
Figure 18. 'H NMR spectrum (400 MHz, CD2CI2) of methylene chloride 191 extracted TLC spot of a,a-diphenyl-/p-xylylene (6) products.
Figure 19. Mass spectrum (EI) of ethyl acetate extracted TLC spot of 192 a,a-diphenyl-p-xylylene (6) products.
Figure 20. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for 193 short-term kinetics experiment of p-xylylene (1) with oxygen in CD3CN.
Figure 21. Plot of In [1] with oxygen vs time for kinetics experiment. 194
Figure 22. Plot of [1]-' with oxygen vs time for kinetics experiment. 194
Figure A-1. 'H NMR spectrum (400 MHz, CD3CN) of 4-[(trimethyisilyl)meth- 211 yl]benzhydrol (17).
Figure A-2. '^C NMR spectrum (100 MHz, CDjCN) of 4-[(trimethylsil- 212 yl)methyl]benzhydrol (17). XLX
'H NMR spectrum (400 MHz, CD.G^ of (4-[(trimethylsil- 213 yl)methyl]phenyl)phenylmethyl acetate (15).
'^C NMR spectrum (100 MHz, CD.CN) of (4-[(triinethyIsil- 214 yl)methyl]phenyl)phenylmethyl acetate (15).
'H NMR spectrum (400 MHz, CD.CN) of a-phenyl-p-xylylene 215 (8) products with TBAF.
Enlargement of Figure A-5. 'H NMR spectrum (400 MHz, 216 CD.CN) of a-phenyl-p-xylylene (8) products with TBAF.
'H NMR spectrum (400 MHz, CD,C1,) of methylene chloride 217 e.xtract of a-phenyl-/?-xyIyIene (8) products.
Enlargement of Figure A-7 from 8-6 ppm. 'H NMR spectrum 218 (400 MHz, CD,CU) of methylene chloride extract of a-phenyl-/j-xylylene (8) products.
'H NMR spectrum (400 MHz. CD,C1,) of ethyl acetate extracted 219 TLC spot of a-phenyl-/?-xylylene (8) products.
Enlargement of Figure A-9 from 8-6 ppm. 'H NMR spectrum 220 (400 MHz, CD,CU) of ethyl acetate extracted TLC spot of a-phenyl-p-xylylene (8) products.
'H NMR spectrum (300 MHz, CDCL) of methyl 4-[(trimethyl- 221 silyl)methyl]benzoate (21).
'^C NMR spectrum (75 MHz, CDCL) of methyl 4-[(trimethyl- 222 silyl)methyI]benzoate (21).
'H NMR spectrum (400 MHz, CD.CN) of (4-[(trimethylsil- 223 yl)methyl]phenyl)diphenylmethanol (22).
'^C NMR spectnmi (100 MHz, CDjCN) of (4-[(trimethyIsil- 224 yl)methyI]phenyl)diphenylmethanoI (22).
'H NMR spectrum (300 MHz, CD,Cy of (4-[(trimethyIsil- 225 yl)methyl]phenyl)diphenylmethyl benzoate (19). XX
'C NMR spectrum (75 MHz, CD,C1,) of (4-[(trimethyIsil- 226 yl)methyl]phenyl)diphenylmethyl benzoate (19).
'H NMR spectrum (400 MHz, CD,CU) of a,a-diphen- 227 yl-/7-xyIylene (6) products with TBAF.
Enlargement of Figure A-17 from 12 to -1 ppm. 'H NMR 228 spectrum (400 MHz, CD,C1,) of a,a-diphenyl-p-xylylene (6) products with TBAF.
Enlargement of Figure A-17 from 8.5- 4.5 ppm. 'H NIvER. 229 spectrum (400 MHz, CD,C1,) of a,a-diphenyl-p-xylylene (6) products with TBAF.
'C NMR spectrum (75 MHz, CD,C1,) of a,a-diphenyl-/?-xylylene 230 (6) products with TBAF.
Enlargement of Figure A-20 from 230 to -10 ppm. NMR 231 spectnmi (75 MHz, CD,CU) of a,a-diphenyl-p-.xylylene (6) products with TBAF.
'H NMR spectrum (400 MHz, CD,C1,) of methylene chloride 232 extracted TLC spot of a,a-diphenyl-p-xylylene (6) products.
Enlargement of Figure A-22 from 7.6- 6 ppm. 'H N^'IR spectrum 233 (400 MHz, CDjCl,) of methylene chloride extracted TLC spot of a,a-diphenyl-/?-xylylene (6) products.
'^C NMR spectrum (75 MHz, CD,CL,) of methylene chloride 234 extracted TLC spot of a,a-diphenyl-/7-xylylene (6) products.
HETCOR spectrum (CD,CL) of methylene chloride extracted 235 TLC spot of a,a-diphenyl-p-xylylene (6) products.
Enlargement of Figure A-25. HETCOR spectrum (CD,CU) of 236 methylene chloride extracted TLC spot of a,a-diphenyl-p-xyl- ylene (6) products. xxi
CHAPTERS
Figure 1. 'H NMR spectrum (400 MHz, CD.CN) of reaction progress of 249 p-diphenoquinodimethane (5) in non-deoxygenated acetonitrile-i/^.
Figure 2. 'H NMR spectrum (400 MHz, CD.CN) of reaction progress of 252 p-diphenoquinodimethane (5) in deoxygenated acetonitrile-t/j.
Figure 3. 'H NMR spectrum (400 MHz, CD.CN) of methylene chloride 253 extract of p-diphenoquinodimethane (5) products in deoxygenated acetonitrile-c/j.
Figure A-1. 'H NMR spectrum (300 MHz, CDCL) ofp-tolylboronic acid (14). 265
Figure A-2. 'H NMR spectrum (400 MHz, CDCL) of methyl 4'-meth- 266 yI-4-biphenylcarboxylate (10).
Figure A-3. '^C NMR spectrum (100 MHz, CDClj) of methyl 4'-meth- 267 yl-4-biphenylcarboxylate (10).
Figure A-4. 'H NMR spectrum (400 MHz. CDCLJ of A^'jV-diisoprop- 268 yl-4-[4'-((trimethylsilyI)methyl)phenyl]benzamide (11).
Figure A-5. Infrared spectrum of iV;iV-diisopropyl-4-[4'-((trimethylsilyl)meth- 269 yl)phenyl]benzamide (11).
Figure A-6. Mass spectrum (EI) of iV,A-diisopropyl-4-[4'-((trimethyIsil- 270 yl)methyl)phenyl]benzamide (11).
Figure A-7. 'H NMR spectrum (400 MHz. CD.Cl,) of ACA^-diisoprop- 271 yl-4-[4'-((trimethylsilyl)methyl)phenyl]benzyIamine (16).
Figure .A.-8. '^C NMR spectrum (100 MHz, CD,C1,) of iV,iV-diisoprop- 272 yl-4-[4'-((trimethylsilyI)methyl)phenyl]benzylamine (16).
Figure A-9. 'H NMR spectrum (400 MHz, CD.CN) of (4-[4'-((trimeth- 273 yIsiIyl)methyl)phenyI]benzyl)diisopropylmethyIammonixim iodide (13). xxii
Figure A-10. '^C NMR spectrum (100 MHz, CD.CN) of 4-[4'-((tximeth- 274 ylsilyl)methyl)phenyl]benzyl)diisopropylmethylammonium iodide (13).
Figure A-11. 'H NMR spectrum (400 MHz, CD.CN) of p-dibenzoquinodi- 275 methane (5) products in non-deoxygenated acetonitrile after 20 min.
Figure A-12. EnlargementofFigure A-11 from 10.5-4 ppm. 'HNMR 276 spectrum (400 MHz, CD.CN) of p-dibenzoquinodimethane (5) products in non-deoxygenated acetonitrile after 20 min.
Figure A-13. Enlargement of Figure A-11 from 8.5-7 ppm. 'H NMR spectrum 277 (400 MHz, CD.CN) of /7-dibenzoquinodimethane (5) products in non-deoxygenated acetonitrile after 20 min.
Figure A-14. 'H NMR spectnmi (400 MHz, CD.CN) ofp-dibenzoquinodi- 278 methane (5) products in deoxygenated acetonitrile after 2 h.
Figure A-15. Enlargement of Figure A-13 from 8- 6 ppm. 'H NMR spectrum 279 (400 MHz, CD.CN) ofp-dibenzoquinodimethane (5) products in deoxygenated acetonitrile after 2 h.
Figure A-16. 'H NMR spectrum (400 MHz, CDjCN") of reaction progress of 280 /?-dibenzoquinodimethane (5) in deoxygenated acetonitrile.
Figure A-17. Enlargement of Figure A-16 from 8-6.5 ppm. 'HNMR 281 spectrum (400 MHz, CD.CN) of reaction progress of p-dibenzoquinodimethane (5) in deoxygenated acetonitrile.
Figure A-18. 'H NMR spectrum (400 MHz, CDjCN) of methylene chloride 282 extract of/?-dibenzoquinodimethane (5) products in deoxygenated acetonitrile.
Figure A-19. Enlargement of Figure A-18. 'H NMR spectrum (400 MHz, 283 CD.CN) of methylene chloride extract of p-dibenzoquinodi- methane (5) products in deoxygenated acetonitrile.
Figure A-20. Enlargement of Figure A-18 from 8.5 - 6 ppm. 'H NMR 284 spectrum (400 MHz, CD.CN) of methylene chloride extract of p-dibenzoquinodimethane (5) products in deoxygenated acetonitrile. xxiii
LIST OF TABLES
CHAPTER 1
Table 1. NIVIR Data for Triene 1. 8
Table 2. NiVIR Data for 4-Vinyl-3-cyclohexenecarboxylic Acid (7), 10
CHAPTER 3
Table L Yields of [2.21Paracyclophane (3) and [2.2.2]Paracycloptiane 70 (14) from /7-XylyIene (1). CHAPTER 4
Table 1. Estimated First- and Second-order Rate Constants. 195
Table A-1. 'H NIVIR and Kinetic Data for /7-XylyIene (1). 23 7
Table A-2. 'H NMR and Kinetic Data for a-Methyl-/7-xylyIene (4). 238
Table A-3. 'H NMR and Kinetic Data for/7-Xylylene (1). 239
Table A-4. 'H NMR and Kinetic Data for a-Phenyi-/;-xyIylene (8). 240
Table A-5. 'H NMR and Kinetic Data for a,a-Diphenyl-/;-xylylene (6). 241
Table A-6. 'H NMR and Kinetic Data for;7-XyIyiene (1) with oxygen. 242 xxiv
LIST OF ABBREVLA.TIONS AND EXPLANATIONS Ac acetyl acac acetylacetonate Bn benzyl bp boiling point br broad (spectral) Bu butyl °C degrees Celsius calcd calculated CI chemical ionization (in mass spectrometry) COSY correlation spectroscopy 5 chemical shift in parts per million downfield from tetramethylsilane d day(s); doublet (spectral") DEPT distortionless enhancement by polarization transfer DMSO dimethyl sulfoxide EI electron impact (in mass spectrometry) ESR electron spin resonance Et ethyl FID flame ionization detection FVP flash vacuum pyrolysis g gram(s) GC gas chromatography h hour(s) HETCOR heteronuclear chemical shift correlation HMPA hexamethylphosphoric triamide HOMO highest occupied molecular orbital Hz hertz EPA isopropyl alcohol IR infiared J coupling constant (in NMR) XXV
L liter(s) LDA lithium diisopropylamide LUMO lowest unoccupied molecular orbital u micro m multiplet (spectral), meter(s), milli M moles per liter Me methyl MHz megahertz min minute(s) tnM millimoles per liter mol mole(s) mp melting point MS mass spectrometry mJz mass to charge ratio (in mass spectrometry) NMR nuclear magnetic resonance PCC pyridinium chlorochromate Ph phenyl ppm parts per million (in NMR) q quartet (spectral) s singlet (NMR); second(s) t triplet (spectra) TBAF tetrabutylammonium fluoride THF tetrahydrofliran TLC thin layer chromatography TMS trimethylsilyl, tetramethylsilane I
GENERAL INTRODUCTION
For many years, the Trahanovsky research group has been involved with the investigation of reactive species. The goal of this research has been to characterize and explore the chemistry of these reactive molecules. A considerable amount of work has been done investigating o-quinodimethanes and p-quinodimethanes (p-QDM's) derived from benzene, fiiran, and thiophene. These compounds have been of general interest to organic chemists from a theoretic standpoint and for their application in synthetic chemistry. The five chapters of this dissertation cover work involving regioselectivity of the Diels-Alder reaction of 3-methylene-1,4-pentadiene, characterization of simple /7-QDM's by NJ^IR spectroscopy, analysis of oligomerization of simple /j-QDM's, and attempts at characterization ofp-diphenoquinodimethane by 'H NMR spectroscopy.
Chapter one describes the preparation of a cross-conjugated triene,
3-methylene-1,4-pentadiene, by flash vacuum pyrolysis (FVP) and it characterization by 'H and I "C^ NMR spectroscopy. It also describes the Diels-Alder reaction of triene and methyl acrylate. Chapter two is a literature review covering stability, formation by pyrolylic and non-pyrolylic methods, and spectroscopy of simple ;?-QDM's. Chapter three describes the preparation and characterization by Nlv®. spectroscopy of three p-QDM's. The chapter also describes the analysis of the /j-QDM's oligomerization products. Chapter four describes the preparation and characterization of four reactive p-QDM's by 'H NMR spectroscopy. Rate constants were determined for their decomposition. Chapter five discusses the attempted observation ofp-diphenoquinodimethane, a biphenyl-based/?-QDM, by 'H NMR spectroscopy. Evidence of the p-QDM's formation was found in the products, both from its reaction with oxygen and its oligomerization. 2
Dissertatioa Organization
This dissertation is composed of five separate papers. Chapters 1, 3,4 and 5 are written in the style suitable for publication in the professional journals published by the
American Chemical Society. Each paper has its own numbering system, detailed experimental section, reference section and appendi.x. .A. general conclusion follows the last paper of this dissertation. j
CHAPTER 1. REGIOSELECTIVITY OF DIELS-ALDER
REACTION OF 3-METHYLENE-l,4-PENTADIENE, THE SIMPLEST
CROSS-CONJUGATED TRIENE
A paper accepted by Journal of Organic Chemistry
Walter S. Trahanovsky and Steven P. Lorimor
Abstract
The smallest possible cross-conjugated polyene, 3-raethylene-1,4-pentadiene (1), was prepared by flash vacuum pyrolysis (FVP). Analysis of the '"C NMR spectrum of triene 1 was clarified with the use of HETCOR NTvIR spectroscopy. The Diels-Alder reaction of triene 1 and methyl acr\'late produces methyl 4-vinyl-3-cyclohexenecarboxylate (5), the
'para" 1:1 adduct, and methyl 3-vinyl-3-cyclohexenecarboxylate (6), the "meta' 1:1 adduct.
COSY and HETCOR NVIR spectroscopy was used to determine that the yields of the 'para'
1:1 adduct 5 and the 'meta' 1:1 adduct 6 are 79% and 6%, respectively.
Introduction
The Diels-Alder reaction of a 2-substimed butadiene and an electron-deficient dienophile can occur to yield two regioisomers, the 'meta' and the 'para\ With electron-rich substituents on the butadiene, the favored product is the 'para' isomer. The ratio of the
'para' to the 'meta' isomer can vary firom nearly 1: 1 to the point where only the 'para' product is observed.'
• ^ fc. i • i!
meta para
3-Methylene-l,4-pentadiene (1)is the smallest possible member of the family of cross-conjugated polyenes. These polyenes have been called ''dendralenes"." Our research group has developed a convenient preparative route to triene 1 and has found that 1 dimerizes at a moderate rate to 1,4,4-tri'vinylcycIohexene, a [4-i-2] dimer.""^ It was proposed tliat tliis dimerization proceeds by a two-step mechanism involving a resonance-stabilized diradical intermediate.'"^
The Diels-Alder reaction of triene 1 with symmetric dienophiles has received modest attention. Blomquist and Verdol in 1955 reported the first Diels-Alder reaction of triene 1, the reaction of 1 with maleic anhydride to form the 2:1 adduct, AH9)-octalin-3.4,6,7-tetra- carboxylic anhydride.' Later that same year Bailey and Economy reported, in addition to the same 2:1 adduct with maleic anhydride, 2:1 adducts with p-benzoquinone. naphthaquinone,
o
and A-'^^(^®^)decahydroanthracene-l,4-dione.^ These earliest examples were studied under conditions that yield only 2:1 adducts.
Cadogan and coworkers have found that triene 1 reacts with certain dienophiles to produce 1:1 adducts that still have a diene unit which is available to react wdth a different second dienophile to produce a mixed adduct.' When a single equivalent ofp-benzoquinone is added to triene 1, a 1:1 adduct is formed which can in turn react with a second equivalent 5 of/?-benzoquinone or an equivalent of A'-phenyl-l,2,4-azolme-3,5-dione to form a mixed adduct. Generally, dienophiles tetracyanoethylene (TCNE) and dimethyl
o oI-
acetylenedicarboxylate (DMAD) add to triene 1 to form only 1:1 adducts but under extreme conditions, a second equivalent of DMAD will add to form the 2:1 adduct.
Several researchers, seeking a less reactive synthetic equivalent of triene 1, have produced 3-methylene-5-phenylsulfinyl-I-pentene (2)® and 2-trimethyIsilyIethyl-1.3-buta diene (3).^ In general, the synthetic equivalent is allowed to react with a dienophile to produce a 1:1 adduct which is then converted to a conjugated diene that can react with a second dienophile. Specifically, diene 2 is allowed to react with a dienophile in the presence of a Lewis acid to produce a 1:1 adduct. Benzenesulfinic acid is thermally eliminated from this adduct to form a diene which can react with a second dienophile such as either dimethyl acetylenedicarboxylate or JV-phenylmaleimide. Ph •^n
N-Ph
,ph -PhSOH R Lewis Add
CO-,Me coame ime CO-,Me
Overall yields are 70-80% and unsymmetrical olefins such as 3-buten-2-one, methyl acrylate, and acrolein gave only limited regioselectivit\' with para to meta ratios of 70:30, 69:31, and
70:30, respectively.
.cojme
Ph * meoac ,Ph eUiylaluminum T dictiloride 0
For the other synthetic equivalent of tiiene 1,2-trimethyl-silylethyI-1,3-butadiene (3), after the addition of the first dienophile, the second diene is generated by treating the 1:1 adduct with Ph3C~BF4". Unsymmetrical dienophiles, such as methyl acrylate and
phjc^bfi" -22 £2 ! —z' mejsr measi' -2'
3-buten-2-one, have only limited regioselectivity in either the first or second Diels-Alder reaction. 7
002^6 85% me^si""^^—me3si'''^^"~''''^^^^c02me (73:27) 3
In order to determine the regioselectivity of the first Diels-Alder reaction of triene 1, we have studied its reaction with methyl acrylate. The results of this study are reported herein.
Results
l,5-Diacetoxy-3-(acetoxymethyl)pentane (4) was prepared fi"om triethyl tricarballate by the procedure of Bailey and Economy.'' Flash vacuum pyrolysis (FVP) of triacetate 4 yields triene 1 with side products of acetic acid, acetic anhydride, and benzene. The amount
H H-C-CH2OAC FVP H-C-CH2OAC 1 K-C-CH2OAC -HOAC H
4 of triacetate 4 that was pyrolyzed varied firom 0.5 to 5.0 g. The yields ranged from 95% for the smaller amounts to 65% for the larger amounts. The acetic acid and acetic anhydride were removed by extraction with aqueous base.
Our research group's previously reported^'^ '"'C NMR spectrum assignments for triene
1 were in error. The peak at 5166.14 is now reassigned to acetic anhydride, an impurity. The two up-field signals were overlapping to give the appearance of a single peak at 5115.77. To confirm the '"'C peak assignments of triene 1, a HETCOR spectrum in benzene-i/e was acquired. The results appear in Table 1. Our present '"C NMR data are consistent with the other reported data.^''° Cadogan's NMR data' show only three peaks but the signal of the quaternary carbon will be absent in the DEPT spectrum. Our present '""C NMR spectrum 8
Table 1. iNMR Data for Triene 1.
Carbon 'H,5 '^C,5 atom'' 1 5.03 115.64
2 145.08
J 6.36 136.16
4 5.32 115.70
4.98
The carbon atom label of triene 1 are as follows:
agrees most closely to the data of Hopf,"^ although the relative assignments of the two up- field signals are reversed. Solvent and temperature changes could explain this reversal of assignments.
Under mild conditions, 40°C in CCU, methyl acrylate and 1 react to yield methyl
4-vinyl-3-cyclohexenecarboxylate (5), the 'para' 1:1 adduct, and methyl
3-vinyl-3-cyclohexenecarboxylate (6), the 'meta' 1:1 adduct, with small amounts of 2:1 adducts (ca. 2%) and dimer (ca. 6%). The ''para' to ''meta' regioselectivity of the addition was in a ratio of 93:7 as determined by GC analysis of the reaction products with biphenyl as an internal standard to be use later to in determining the yield. A mixture of the two 9 regioisomers could be isolated from the 2:1 adducts and dimer by columm chromatography but attempts to isolate the individual two isomers by column chromatography failed. A 'H
NMR, '^C NMR, and mass spectra were obtained of the mixture of esters 5 and 6.
^cojme
The mixture of esters 5 and 6 was converted to the corresponding acids 7 and 8 by basic hydrolysis. Acid 7 was isolated from the mixttire of acids by selective recrystallization from acetic acid/water and was further purified by vacuum sublimation. 'H, '"C, HETCOR, and COSY NMR spectra of acid 7 were obtained. The results appear in Table 2.
Assignment of acid 7 as the 'para' 1:1 adduct was confirmed by the analysis of the COSY spectrum. The hydrogen on carbon three is coupled to the hydrogen on carbon two. The hydrogen on carbon two is also coupled to the hydrogen on carbon one. The chemical shift of carbon one is shifted down field because it is a to the carboxylic acid.
Acid 7 was treated with methanol to yield ester 5. A GC correction factor for the ester relative to biphenyl was determined. With this GC correction factor and the GC analysis of the crude reaction mixture, the yield of 5 and 6 was determined to be 79% and
6%, respectively. A NMR spectrum of ester 5 was obtained to verify the regio assignments made to the esters 5 and 6.
H* 7 5 MEOH 10
Table 2. NMR Data for 4-VinyI-3-cycIohexenecarboxylic Acid (7). Carbon atom" 'H,5 '^C,5 1 2.59 39.14 2 2.4 27.79 2.4 j 5.72 127.04 4 135.69 5 2.33 23.03 2.13" 6 2.19-2.09'' 24.75 1.75 7 6.33 139.27 S 5.06 110.83 4.98 9 181.58 " The carbon atom label of acid 7 are as follows:
V H H
H I \/Cl H
I H 3 h ^Cl
H H
The 'H NMR assignment may be reversed due to the overlap of their signals.
Discussion
The improved preparation by FVP of acetate 4 provides triene 1 in good to high yields for quantities of up to 5 g. For preparations of one gram or less, the overall yields are very high (95%). As larger quantities are prepared, yields are more modest (65%) as triene 1 is lost to the formation of carbon deposits on the pyrolysis mbe and slightly larger amounts of 11 dimer in the product mixture. The improved preparation also provides triene 1 with fewer by-products such as acetic acid, acetic anhydride, benzene, dimer, and oligomers.
The Diels-Alder reaction of triene 1 and methyl acrylate proceeds under mild conditions in high yield (car. 85%) and with high regioselectivity (93/7) in favor of the 'para'
1:1 adduct. The mildness of the reaction allows for very little side-product formation such as dimer, oligomers, and 2:1 adducts. Formation of 2:1 adducts with methyl acrylate requires higher reaction temperatures or extended reactions times.
Direct use of triene 1 with unsymmetrical dieneophile yielded products with greater regioselectivity compared to the two synthetic equivalents: 3-methylene-5-phenylsuIfinyl-l- pentane (2) and 2-trimethylsilylethyl-l,3-butadiene (3). The Diels-Alder reaction of triene synthetic equivalent 2 with methyl acrylate yielded only moderate regioselectivity for the
'para' 1:1 adduct (69:31).^ Triene synthetic equivalent 3 yielded only slightly better regoiselectivity for the 'para' 1:1 adduct (73:27).^
This high regioselectivity is consistent with the analysis based on frontier molecular orbital theory.'"'This Diels-Alder reaction involves a "normal electron demand" because the vinyl group on the diene is a donating group and the methyl carboxylate on the dieneophile is an accepting group. By bringing together the largest coefficients of the
HOMO of the diene and LUMO of the dieneophile, the "para" regio-isomer is predicted.
^cojue ^^cojme
Kahn and Hehre have proposed an alternative method for predicting the regioselectivity of cycloaddition reactions, based on matching complementary (electrophilic and nucleophilic) reactivity surfaces calculated at the Hartree-Fock level (3-21G/3-21G^'^ 12 and obtained independently for each of the two reactants.^" This chemical reactivity modeling procedure uses a "test" electrophile, H', to probe the diene and a "test" nucleophile,
H", to probe the dienophile. In the case of the hydride probe, reactivity surfaces are constructed by treating the hydride as a nondeformable "ball" which then "rolls around" on the top of the electron-density surface of the dienophile and the potential energy of interaction is evaluated at each point of contact.'" The preferred regiochemistry of the Diels-
Alder reaction is one in which the diene terminus with the larger reactivity towards electrophiles aligns with the ethylene carbon of the dienophile with the larger reactivity towards nucleophiles. Using this method, the "meta" 1:1 adduct is predicted to be favored.'"
Consideration of a dipolar resonance structure of the transition states also leads to the conclusion that the 'para' 1:1 adduct is favored. Triene 1 is analogous to 2-phenylbutadiene
"'^c02me and the reaction of this diene and methyl acrylate also produces more of the 'para' adduct
{'para'!'meta' = 82/18).'^
coame ph.^^,,-v^c02me f' ^ ^-^COaMe •
CoDcIusion
3-Methylene-I,4-pentadiene (1) can be prepared with few impurities by flash vacuum pyrolysis (FVP) in good to high yields (65-95%). The '""C NMR spectrum of triene 1 was clarified with the use of HETCOR NMR spectroscopy. The Diels-Alder reaction of triene 1 and methyl acrylate produces 1:1 adducts in 85% yield with dimer and 2:1 adducts as the 13 primary impurities. The reaction is regioselective favoring methyl
4-vinyl-3-cyclohexenecarboxylate (5), the 'para' 1:1 adduct, over methyl
3-vinyl-3-cyclohexenecarboxylate (6), the ^meta' 1:1 adduct by 93/7. This selectivity is consistent with frontier molecular orbital theory and dipole resonance structures of the transition states. The "para" selectivity is inconsistent with Kahn-Hehre reactivity modeling procedure.
Experimental Section
Methods and Materials. Some general methods have been described previously.'"
All materials were commercially available and used as received, except where indicated.
'H NMR spectra were 300 MHz unless noted otherwise. '""C NMR spectra were recorded at
75.47 MHz unless noted otherwise.. For bodi the GC and the GCMS analysis, a DB-5 column (30m, I.D. 0.32 mm, 0.25 ji film thickness) was used. Elemental analyses were performed at Galbraith Laboratories, Knoxville, TN.
l,5-Diacetoxy-3-(acetoxymethyl)pentane (4) was prepared by a procedure similar to the procedure of Bailey and Economy." The crude product was distilled twice (short-path) to give a Hght yellow distillate, bp 120 °C (0.07 mm) (ht."' 120 °C (0.5 mm)). Analysis of the material by capillary GC indicated it was > 99 % pure. '""C NMR (75.47 MHz, CDCI3) 5
(multiplicity when off-resonance decoupled) 170.36 (s), 170.28 (s), 65.74 (t), 61.62 (t), 31.50
(d), 29.64 (t), 20.34 (q), 20.27 (q).
3-MethyIene-l,4-pentadiene (1) was prepared by FVP'"* of 5.00g (19.2 mmol) of
L5-diacetoxy-3-(acetoxymethyI)pentane (4) by a procedure similar to that reported^" ® with the follovving changes: a) No quartz chips were used in the pyro lysis tube, b) 15 mL of CCU 14 was added to the trap instead of benzene, c) Pyrolysis oven was heated to 850 °C. d) Sample chamber was heated to 90 °C.
A significantly different workup was used. The product solution was transferred to a separatory funnel with an additional 5 mL of CCI4 as rinse. The CCI4 solution was washed with saturated NaHCO: (4 x 10 mL). The basic wash layers were combined and back extracted with an additional 5 mL of CCU. The CCU layers were combined, washed with saturated NaCl (10 mL), and dried (MgS04). Known volumes of the product solution were transferred into vials for storage at -80°C.
.A. vial of triene 1 solution was allowed to warm to room temperature. The concentration of the triene 1 solution was determined by N\IR spectroscopy (1.1,2.2- tetrachlororethane, internal standard) to be 0.54 M. The yield was 61%. GC and NMR analyses indicates little or no acetic acid and acetic anhydride. NMR (benzene-^/e) 5 6.36
(dd, J=17.4 Hz, y'=10.8 Hz, 2H), 5.32 (dd,y=17.1 Hz, J'=\.l Hz, 2H), 5.03 (s. 2H), 4.98
(dd, y=10.9 Hz, J'=\.\ Hz. 2H); lit.^ ^H NMR (benzene-Js, 298 K) 5 6.33 (dd, /=17.4 Hz, y'=10.8 Hz, 2H), 5.30 (dd,/=17.5 Hz, J'=1.5 Hz, 2H), 4.99 (s, 2H), 4.95 (dd, 7=10.9 Hz, y'=1.6 Hz,2H)); '"C NMR (75.47 MHz, CD2CI2 and CCU) 6 144.74,135.93, 115.63,
115.44; '^C NMR (75.47 MHz, benzene-t/g) 5 (multiplicity when off resonance decoupled)
145.08 (s), 136.16 (d), 115.70 (dd), 115.64 (t); lit.'° '^C NMR (CD2CI2, 203 K) 5
144.55,136.09, 116.27, 116.17; lit.' ^'CNMR(CDCl3, DEPT) 5 135.62, 115.38, 115.35; lit.®
^^C NMR (75.47 MHz, benzene-t/e 298 K) 5 (multiplicity when off resonance decoupled)
166.14 (s, (low intensity)), 145.18 (t), 136.26 (d), 115.77 (t). 15
Methyl 4-Vinyl-3-cyclohexenecarboxjiate (5), Methyl 3-Vinyl-3-cyclohexenecar- boxylate (6), and 4-ViiiyI-3-cyclohexenecarboxyIic Acid (7). To a 10-mL round-bottom
flask was added 0.0197g (1.277 x 10~* mol) of biphenyl. A vial containing one mL of 0.49 M solution of triene 1 (4.9 x 10~^ mol) in CCU was warmed from storage at -80°C to room temperature. The triene 1 solution, one mL of CCL. and uvo mL of methyl acrvlate (1.9g,
2.2 X 10'" mol) were added to the flask. A water-cooled condenser was placed on the flask.
The flask was healed to 40°C. The reaction was followed by GC and after 18 h, the triene 1 was consimied. Analysis of the crude product mixture by GC and GC/MS revealed two major products, methyl 4-vinyl-3-cyclohexenecarboxylate (5) and methyl 3-vinyl-3-cyclo- hexenecarboxylate (6), and several minor products, dimer {ca. 6%) and 2:1 adducts {ca. 2%).
From the GC analysis the 'para' to 'meta' regioselectivity (the ratio of 5 to 6) was determined to be 93:7. The product mixture was concentrated under reduced pressure to yield viscous oil (0.082g). Isolation of esters 5 and 6 was attempted by column chromatography on silica gel (toluene) but failed to resolve the two regioisomers although the dimer and 2:1 adducts were removed. With this mixture of the two regioisomers 5 and 6,
'H and '"C NMR spectra were obtained.
5: 'H NMR (CDCb) 5 6.34 (dd, /=17.4 Hz, ^'=10.5 Hz, 1 H), 5.74 (broad s, 1 H),
5.08 (d, /=17.4 Hz, IH), 4.94 (d, 7=10.8, 1 H), 3.70 (s, 3 H), 2.56 (m, 1 H), 2.38 (m. 2 H),
2.30 (m, 1 H), 2.11 (m. 2H), 1.73 (m, IH); ^"C NMR (75.47 MHz, CDCL) 5 176.03, 139.27,
135.55, 127.28, 110.60, 51.66, 39.29,28.03, 24.95, 23.12; MS (70 eV) 166 (M^ (17), 137
(2), 135 (2), 107 (30), 106 (87), 105 (41), 92 (15), 91 (100), 80 (14), 79 (75), 78 (50), 77
(39), 65 (10), 51 (12). 16
6: MS (70 eV) 166 OO (<1), 137 (2), 107 (18), 106 (14), 105 (13), 91 (63), 79
(100), 78 (28), 77(22), 65 (11), 51 (10), 50 (5).
To the crude mixture of esters 5 and 6 (114mg, 0.69 mmol) was added 3 mL of 1 M
NaOH and 10 mL of HiO. The mixture was stirred rapidly and warmed to near boiling for
about 1 h. The solution was washed with hexanes (3 x 10 mL). The aqueous layer was slowly acidified with 1 M HCl to a pH of less than one. The solid was recr>'stallized in
Ac0H/'H20. Acid 7 was sublimed at 50°C (0.01 mm) to yield 51 mg (0.34 mmol) of a finely
divided, white solid: mp 75.5-76.2°C; 'H NMR (CDCI3) 6 6.33 (dd, 7=17.4 Hz, J'=10.8 Hz,
1 H), 5.72 (broad s, 1 H), 5.07 (d, J=17.7 Hz, IH), 4.93 (d, /=10.8, 1 H), 2.59 (m, 1 H), 2.40
(m, 2 H), 2.30 (m, 1 H), 2.15 (m, 2H), 1.74 (m. IH); '"C NMR (75.47 MHz, CDCI3) 5
181.32, 139.21, 135.63,129.98, 110.78. 39.07, 27.75, 24.72. 23.00; Anal. Cald for CqHuO:".
C, 71.03; H,7.94. Found: C, 71.20; H, 7.94.
Forty mg (0.26 mmol) of acid 7 was dissolved in methanol with a trace of H2SOJ.
The solution was heated to reflux for about 10 h. Solid NaHCOs was added and then the
methanol was evaporated under reduced pressure. The product was dissolved in 10 mL of
ether and the solution was washed successively with of H2O (3 x 10 mL), satxirated NaCl
solution, and then dried (MgS04). Ester 5 was found to be 98% pure (GC) and concentrated
to give 38 mg of an oil (0.23 mmol, 87% yield). Three solutions of purified ester 5 (Ix 10~*
mol) and biphenyl (2.65 x 10'^ mol, internal standard) in 0.600 mL of CCU and 0.400 mL of
CD2CI2 were prepared. By comparison of NMR quantification (10 s pulse delay) of ester 5
in the three samples and GC peak area (biphenyl, internal standard), a GC correction factor
of 1.68 gester %biphenyi gbiphenyf' %ester*^ was calculated.'^ With this GC correction factor and
the data collected from the above preparation of esters 5 and 6, the yields can be calculated to be 79% and 6%, respectively. A 'H NMR spectrum of purified ester 5 was obtained and was consistent with the major component of the 'H N^-ER spectrum of the mixture of esters 5 and
6.
References
(1) For reviews, see (a) Camithers, W. Some Modem Methods of Organic Synrhesis,
Cambridge University Press: New York. 1986; pp 183-244. (b) Oppolzer, W.
"Intermolecular Diels-Alder Reactions." In Comprehensive Organic Synthesis; Trost.
B. M., Fleming, I., Paquette, L. E., Eds.; Pergamon Press: New York, 1991; Vol. 5,
pp 315-399.
(2) Bloomquist, A.T.; Verdol, J.A. J. Am. Chem. Soc. 1955, 77, 81.
(3) Bailey, W.J.; Economy, J. J. Am. Chem. Soc. 1955, 77, 1133.
(4) For review, see Hopf H. Angew. Chem. Int. Ed. Engl. 1984. 23, 948.
(5) Koeplinger, K.A. M.S. Thesis, Iowa State University of Science and Technology
1987.
(6) Trahanovsky, W.S.; Koeplinger, K.A. J. Org. Chem. 1992, 57, 4711.
(7) Cadogan, J.I.G.; Cradock, S.; Gillam, S.; Gosney, I. J. Chem. Soc., Chem. Commun.
1991, 114.
(8) Wada, E., Nagasaki, N.; Kanemasa, S.; Tsuge, O. Chem Lett. 1986, 1491.
(9) Hosomi, A.; Masunari, T.; Tominaga, Y.; Yanagi, T.; Hojo, M. Tetrahedron Lett.
199^,21(43), 6201.
(10) Almeimingen, A.; Gatial, A.; Grace, D.S.B.; Hopf, H.; Klaeboc, P.; Lehrich, F.;
Nielsen, C.J.; Powell, D.L.; Traetteberg, M. Acta Chem. Scand. 1988, A42, 634. IS
(11) (a) Fleming, I. Frontier Orbitals and Organic Chemical Reactions, John Wiley &
Sons: New York, 1976; 121-142. (b) LOWT>', T. H.; Richardson, K. S. Mechanism
and Theory in Organic Chemistry, Harper Collins: New York, 1987. (c) Epiotis, N.
D. J. Am. Chem. Sac. 1973, 95(17), 5624.
(12) Kahn, S.D.; Pan, C.F.; Overman, L.E.; Hehre, \V.J. J. Am. Chem. See. 1986, 103(23),
7381.
(13) Nazarov, I. N.; Titov, Yu. A.; Kuznetsova, A. I. Izv. Akad. NaukSSSR. Otd. Khim.
Nauk 1959, 1270.
(14) (a) Trahanovsky, W.S.; Ong, C.C.; Pataky, J.G.; Weitl, F.L.; Mullen, P.W.; Clardy,
J.C.; Hansen, R.S. J. Org. Chem. 1971, 26, 3575. The FVP apparatus is available
from Kontes Scientific Glassware, (b) For review, see Brown, R.C.F. Pyrolysis
Methods in Organic Chemistry, Academic: New York, 1980, Chapter 2.
(15) Dietz, W. A. y. Gas. Chromatogr. 1967, 68-71. 19
Appendix A Z X Z.2. axaaai2aaiX2.3.2>z>3> 3 » 3 ciaoaa Anaaanaaaaaaaaaaano n aa aaaaa uoaaftDaaiianooaaonaa n aa fsinmirui r\i*o ... *r^OOC«lwJ»0»tJ»0»r''r» f-i-r-rv t/jin ooo
I- axiio OJfWIV r UlJJiJJiJ
o
n r'l > f i r in 111 n i TrrjTT I |T f F fyrn Ijrr T T »1 l'» f ••1" fTrTfM /a 7 K.S 6 fi 5 4 b 0 ti PPM
Figure A-1. 'H NMR spectrum (300 MH/, Cl)C:i,) of l,5-(liaccloxy-3-(acetoxymelliyl)pciilanc (4). (S: chloroform, T: TMS) lo
s
1— 200 150 100 50 PPM
Figure A-2. '^C NMR spectrum (75.47 MHz. ClDCl,) of 1,5-diacctoxy-3-(acctoxymcthyl)pcnlanc (4). (S; chloroform) zzxzxa: a&xxxzx a T> ass XX Aaaaac^ aaatiAao. Q nu aaa aa aaaaacL aaaaaaa aaa aaa aa rw>cntfMn^iO •-cnp» --0 r<.trVAjr^^NO* iTtOfXlv«i«a inokcn ^.o ^«ivr*nri VIMAiCM a^TkOi ootm oo lOuitouKOu} tfwitOtrw^wi
aKf»o»- u^ m , j l— »»> n»» ryiTf 1 rri i mM l f n i» n i n » ri i n| nn ? i n n 111 > M »i n m i n »I i pin 111»r| IT>t ?I >T Ip Imin H I T Iri rtrrpTT Tttttt JL ;I » I I HIt I 7 5 7 6.5 6 s.5 s 4.s 4 3.9 i 25 2 1.51 o.s PPM igure A-3. 'H NMR spcclrum (300 MHz, CD^CI, and CCI^) of 3-mclhylcnc-l,4-pcnlatlicnc (1). (S: incthylenc chloridc, 1 TMS) za zxxx a a a a a. xx a rx a-a:a aa- aaaoaa aaad aaa aaa aaaaa aaaaSn. aoaa aaa aaa an a oa iOv-^n u>nu> r.r>tT» rs»-»a*iWT> iTHOovm rwoin muwD o>ma)*^ui ^moimnru rxnrvKvj ooa> Kir»n mcninaKn lOlAUMbDlU irv)*04n tntn^ /F T lo OJ n"r| t»»»»• 111 j i im n i i i |i i i > m i ir vovp'rn f ITT rryrr i -.rjTT yvri'i>'(minm|iiii 7.5 7 6.5 6 !}.& s 3.5 2.5 l.S 0.& n 'PM Figure A-4. '11 NMR spcctruin (300 MH/, bcn/.cnc-J^) or3-mclhylcnc-l,4-pcnlailicnc (1). (S: licn/.cne) XZ7XZ7ZZZZ zxx Q.U. Q. d-Q.Q. Ci-IV uaaana 0.0. a 0.0.0.0 OO.Q. cn'wiA Ajno ID1ruArvomnovinmn» "^o>c7>oy^^ en rvmmowxxnwyu) // I uijpj S 1^ 4^ rTTTir Figure A-5. '^C NMR speclrum (75.47 MHz, C'DjCI, and CCl^) of 3-mcthylene-l,4-pentadiene (1). (S: methylene chloridc) xz zz aa aa &g: rxioin »-Oi ruoo) trim mom UHO ro r>'sir> / I F V to iBO IBO >70 160 150 140 130 120 110 100 90 00 70 60 SO 40 30 10 10 0 PPM Figure A-6. '^C NMR spcclrum (75.47 MHz, benzcnc- ie« ch in- "t" ^T" —J— —.—' r- 7.5 7.» 6.S fl ttfmt Ml Figure A-7. HliTCOR spectrum (benzene-^/, ) of 3-mclhylcnc-l ,4-pcnladienc (1). "C « fppal US.51 Jr^~^ US.6S co v""'/' us.Id- US.ss -w-j-y 5.3S S.3I s.es S.20 S.IS S.lt s.es s.es 4.»s fl Figure A-8. Bxpansion of Figure A-7. HIZ TCOR spectrum (bcii/.cne- mkJM lo 00 5 5 lUJlriyit'iY*'! wW^Vyifi»»T 111fj J1 fi b 1 Z ft O *) 0 (I PPM figure A-9. '11 NMR spectrum (300 MHz, CDCl,) of methyl 4-vinyI-3-cyclohcxcnccarboxylate (5) and inctliyl 3-vinyl-3-cyciohexenecarboxylate (6). (S: chloroform, T: TMS) X a a « A a X a z a a a a a a a X 1t aaaxa;»ax Aon Aa A A ona ona A A AA t1. Aonaattua A u u n n iSSAAA UA AAA. Dua aa tin tt naaaauaa i-in I U)«*aw*iat ^UlO) 0>f OMVt inut cD rurwtxuii pKUt\«*>k/> tits *>UJ* NCtn u»'< ru inofU'*oi»o<»< »-»•««> WHM »*a) in ou>iiMt«ni.ivr U>U3 Ul'^ f (ui>»Nin>A r-aKii <««i luni f/ IP i//r f /I /I lovo S T mTTTT^rmTriii|TTfTrTTn|TTmTm|iTrTlmTiTTmtTii^rnn'r»ri|T»in^riT|»/>»iTTtT^TntnTiTpitntfTi|tTiTtnTyj^t»»tiTf»|trrrlrTT^pfiTnnTyiTtn»fn^ttTniif|TTTmnfpTtitrifTprnittit|Tii* lao iQo i;o ir»o tao ho i3o t2o no lOb bo do (>D tiU PPM Figure A-IO. '^C NMR spcctriim (75.47 MHz, CDCl,) ormelhyl 4-vinyl-3-cyclohexenccaiboxylatc (5) and methyl 3-vinyl-3-cyclohcxcnccarboxyiate (6). (S: chloroform, T: TMS) o» rs i/i ^ o uj lu • r-4 to O lo ^ r« v- CN O to m TO ^ O ^ O lO Id Ot CU IN t» O tO lO €•»< O •o r* o» «N oy •^ >* — oo{nco(ur^iou>c:ii/i^c3eor^ui«r»n«-'r-c->cnr-»io«ou>*«^K>cNrNr »o »n »0 rs| C3 O l4 , ' r*f*i"i'»~|Ti~n I'll T I I I » r j-n-r-r-fn~r V j-T-rr-t-fi-r 1 11.0 10.0 9.0 B.O 1.0 0.0 PPM Figure A-11. 'H NMR spcctnim (400 MHz, CDC'l,) or4-vinyl-3-cyclohcxcnccarboxylic acid (7). (S; clilorolbrm) r>. •- fN* »r> o ro "• r-s «•>« o to i/» to ct •«# to c» »0 k> r-« oicor-(Nf>>o^i(Ar40^«« oootcocorx^ioin Ui —. o CO r- i/> ro O Ol oi r-.i0i0in-*v»orjf>jo I 2.5 2.3 2 . 1 PPM Figure A-12. Expansion of Figure A-11. 'H NMR speclrum (400 MHz, CDCl,) of 4-vinyl-3-cyclolicxcnecarboxylic acid (7). — u-i itj rn o o> r-- u3 loOJ I t—i—i—'—r -i—[— -i—i—i—i—r —i—'—i—'—i— -t—i—t" "1—'—r ->—r 220 200 180 160 140 120 100 80 60 40 20 0 PPM Figure A-I3. '^C NMR spectrum (100 MHz, CM^Clj) or4-vinyl-3-cyclohexenccarboxylic iicid (7). (S: chloroform) "C PPM 10 20 30H 4 SO 60 70 80- 90- 100-: 110^ n—•— 120- 130- 140- 150- 0 PPM Figure A-14. llhlCOR spcctmm (CDCI^) of4-vinyl-3-cyclohcxenccaiboxylic acid (7). 22 24 26 28 30 32 34 36 38 40 "39 5f" 42 »f tfthtr^ttt n|ri| ttttttiitpt »^tt|f-f-jr ttttttttj ptttttttt prrrrfT? t vjit -rrrri i 7 2>.6 2.5 214 2.3 2.2 2?1 2.0 1.9 1.8 ' 1.7 1.6 1.5PP1V I lMgureA-14. HHTCOR spuotmin (CDClj) or4-vinyl-3-cyclohcxcnccarboxyl 0 1 2 3 4 H'i8a 5 oj 6 7 8 9 ppin f!l re A-16. COSY spcctriim (CDCIj) of 4-vinyl-3-cyclohcxeiiccarhoxylic acid (7) with H"- & 11"'' interaction with H'aiui 11^ interaction with & I P'' highlighted. 1.6- 1.7h - ;b 'sjSI'' 1.8- fflcavo* • 1.9- 2.0- 2.1- .. • tpui ;ss:je 2.2- oj ON 2.3H j i o**v I co2h 2.4- ..^0 2.5- 2.6- 2.7- Figure A-I7. COSY spectrum (CDCI3) of 4-vinyl-3-cyclohcxcncciuboxyIic iicici (7) willi H-- & 11-'' interaction witli H' higii- ligiited. / -joj a. 2.8 2.7 2.6 2.5 2.4 2.3 2.2 2.1 2.0 1.9 1.8 1.7 1.6 ppm Figure A-18. COSY spectrum (CDCIj) of 4-vinyl-3-cyclohexcnccarboxylic acid (7) with H' interaction with H**''and H' interaction with H'''' highlighted. iB 115 ffistssa •»« flc to* • 1.9-J 2.0- 2.1- .. • ^fQta 38!^ i'ir •• 7f 2.2- OJ 00 < 0« • co2h 2.3- tr o.»to go II 2.4- fo 2.5- ° li 2.6- ;st 2.7- Figure A-I9. COSY spectrum (CDCl,) of 4-vinyl-3-cyclohcxeiiccarhoxylic acid (7) with I !*' interaction with 11'' highlighted. 1 y ojvo LL - ill J 1 jIL. J. o c3 o I t"v ' I ^ 1 ' 7 5 7 0 6 fi 6 0 5 5 5 0 4 5 d 0 1 5 JO 2 b 20 lb 10 O'J PPM Figure A-20. 'H NMR spectrum (400 Mil/, CD^Clj) ofmethyl 4-vinyl-3-cyclohexenecarboxylate (5). (I: intcral standard, biphcnyl, S: methylene chloridc) 40 CHAPTER 2. LITERATURE REVIEW OF SIMPLE BENZENE-BASED ;;-QUINODLMETHANE'S Introduction /j-Quinodimethanes (/i-QDM's) are reactive, cross-conjugated cyclic molecules that have been invoked as transient intermediates in a number of reactions.'"" p-Xylylene (1), the parent benzenoid p-QDM. is considerably less reactive than its isomeric counterpart o-.xylylene (2),' "' the simplest o-quinodimethanes (o-QDM's)." p-QDM and o-QDM are structurally related to two other classes of cross-conjugated cyclic molecules, p- and o-quinone methides^ (3 and 4) and p- and o-quinones' (5 and 6). 0 l| I p-QDM's are important monomers for the vapor-coating polymerization of poly-p-QDM's which was originally developed by Union Carbide Corporation and now is used by dozens of specialized companies.^ Poly-p-QDM's are sold under the trade names "Parylene" and "Galxyl"; Parylene N refers to unsubstituted poly-/?-xylylene (7), Parylene C to poIy-2-chloro-/7-xyIyIene (8) and Parylene D to poly-2,5-dichloro-/7-xylylene (9).® The physical properties of low-gas and moisture permeability, high dielectric strength, high 41 - CI - — CH2^;^ !;-CH2 —CHj-^v, >CH2— - n - ' n 7 8 9 dielectric constants and the method of vapor-coating makes Parylene suitable for the surface coating of critical electrical assemblies.^ The film deposited on the surface can be adjusted to a thickness of several submicrons to several millimeters.^ The solvent-free, pinhole-free, and stress-free vapor coating process of Parylene is also ideal for the protective coating of biomedical implants and restoration of paper docimients by encapsulation of individual fibers to prevent them from fracturing.^ .Another area of current interest in poIy-p-QDM's is their use as precursor polymers for poly(p-phenylenevinylene) (PPV's)."^ PPV's display a variety of interesting properties, such as electrical conductivity upon doping, nonlinear opucal response, electro- and photoluminescence." Although p-quinodimethanes have been identified as an intermediate product in the formation of poly-p-QDM's, the mechanism of initiation and chain propagation is still open to discussion.'" Many ;?-QDM's polymerizes spontaneously at room temperature upon condensation on a solid surface. Thiele and Balhom attempted to prepare p-QDM 1 by debromination of 7,8-dibromo-p-xylene but instead obtained an insoluble white powder which they described as poly-p-QDM 7.'" Thiele'" and Staudinger'"* were able to isolate a relatively stable tetraphenyl derivative ofp-QDM 1, 7,7,8,8-tetraphenyl-p-xylylene (10). This research was motivated by Gomberg's discovery of the stable triphenylmethyl radical (11) which led to the question does /j-QDM 10 exist in the quinoid form or as a biradical 12. Early investigations 42 indicated that 10 consisted of less than 0.2 % biradical 12, but Chichibabin's hydrocarbon, 13, was 5-10% biradical 14 based on ESR.'"* ph^ph ph^ph Ffh Ph— • i • Ph ph-^ph ph-^ph 10 12 11 ph^ph ph^ph r I ph'^ph ph'^ph 13 14 p-Xylylene (1) was first isolated as a solution and properly characterized by Szwarc who obtained it by the pyrolysis of/?-xylene.'" Aldiough the monomer is stable in the vapor phase, in the condensed phase at low temperature it polymerizes spontaneously to poly-/j-xylylene (7) as well as the cyclic dimer ([2.2]paracyclophane) (15) and other side-products. Subsequently this material has been extensively studied on account of its Pyrolysis ; ^ 1 •- 7 15 unusual chemical and physical properties.'^'^ The energy difference of the /?-QDM molecule between the singlet ground state, 1, and the triplet excited state, 16, has been 43 calculated to be as small as 8-9 kcal mol"' (33-38 kJ/mol) by Coulson and coworkers"^ and as large as 0.93 eV (90 kJ/mol) by Dohnert". The corresponding value for ethylene was CH, , X CH, 16 determined by Waser"' to be 82 kcal mol"' (343 kJ/mol). This unusually low energy difference ofp-QDM 1 is responsible for the very high reactivity and thusly, p-QDM 1 is so reactive that, when prepared, it polymerizes spontaneously even at -78°C and it cannot be isolated pure under normal conditions/""' Coppinger and Bauer have defined the relative stability of quinonoid systems as the energy difference between the quinonoid ground state and the benzenoid excited state; they pointed out that the stabiUty increases witla increasing electronegativity of the exocycUc groups. That is, an increase in electronegativity of the exocyclic atom results in a decrease of die highest occupied bonding energy level and in an increase of the lowest unoccupied antibonding energy level. This leads to an increase in energy difference between ground and transition states and the large stability of the compound. /j-Benzoquinone (5) is a typical example of quinonoid compounds isolable at room temperature. WTien electron-withdrawing substituents such as the cyano group are introduced at the 7 and 8 positions of the unsubstituted quinodimethane, the electronegativity of its exocyclic positions increase, leading to stablilization of quinodimethanes. Therefore, substituted quinodimethanes become more stable and more easily obtained as crystals at room temperature. Many substituted quinodimethanes like 7,7,8,8-tetracyano-/7-quino- 44 dimethane have been prepared as isolable crystalline compounds. Consequently, substituted quinodimethanes, isolable as pure crystalline and highly conjugated (reactive) monomers, are expected to exhibit novel and unique polymerization behavior beyond the scope of conventional polymer chemistry estabhshed on the basis of vinyl polymerizations of ethylenes. Pyrolytic Preparation In 1947 Szwarc prepared a white polymeric material by a rapid flow (flash) pyrolysis ofp-xylene under reduced pressure.'^ Since p-xylylene diiodide (17) was detected among the pyrolysis products when iodine gas"^ was mixed with the pyrolysis gas, he proposed the formation of/7-xylylene (1) in this pyrolysis.He claimed the polymeric material to be poly-p-xylylene'^ (7) and proposed a mechanism for its formation'^ which involves thermal 7 1000''C 4 mm Hg 1 '2(3) CH,I CHjl 17 cleavage of carbon-hydrogen bonds of /^-xylene to yield p-xylyl radicals 18, which in turn collide with each other to give /?-xylene and p-QDM 1 through disproportionation. p-QDM 1 condenses and polymerizes to produce poly-p-QDM 7, a high melting point substance 45 CH, ' v CH3 18 which is inert to organic and inorganic reagents. Further side reactions causing crosslinking are indicated by the insolubility in high boiling solvents at high temperatures of poly-p-xylylene prepared from the pyrolysis of/?-QDM 1.''"'® The rapid flow pyrolysis of /?-xylene was carried out under reduced pressure of 4 mm Hg at 1000°C and the pyrolysis products were condensed at -78°C to obtain solutions of monomeric p-QDM up to 0.12 M concentration.'' In addition to /7-QDM 1, benzene, toluene, styrene, p-ethylstyrene, l,2-di(p-tolyl)ethane, a diarylmethane, anthracene, cyclophane 15, [2.2.2]paracyclophane (cyclic trimer, 19), and 4,4'-dimethylstilbene were produced as by-products.''" Even when kept at -78°C the solution of the pyrolysis product polymerizes very slowly. When an aUquot is drawn up into a warm pipet and allowed to flow back into the solution, the polymerization rate is significantly increased, presumably due to formation of diradicals with n-mers. The polymerization of/?-QDM 1 is believed to take place by successive additions of p-QDM monomer until all the monomer is consumed or the polymeric free radical ends are entrapped in the polymer mesh. Errede and coworkers'^ have found that solutions which polymerize with apparent first-order rate constants of 9+1 x 10"^ s"' could be reproduced fairly consistently if the solution of the 46 19 pyrolysis was filtered through a bed of crystalline p-xylene using an apparatus that was prechilled to -78°C. Such solutions were used to determine ±e rate of polymerization at various temperatures above -78°C. The rates were found to obey a first-order law with respect to monomer. The kinetic plot of the apparent first-order rate constants was linear for the first 10 h but the deviation from the first-order kinetics become appreciable at longer reaction times, corresponding to the slow but steady decrease in apparent rate constants. A plot of the reciprocal of the apparent rate constant against time is linear, indicating that the disappearance of the polymerization active sites is second-order with respect to the sites.'® This treatment gives the ratio of apparent rate constant of disappearance of the polymerization active site to that of the polymerization to be 0.45, in sharp contrast to the conventional free radical vinyl polymerization in which termination is about -10"* - 10^ times faster than propagation. One interesting characteristic ofp-QDM 1 polymerization is that the propagation, a radical addition reaction between a very stable polymer radical and a very reactive monomer, takes place with a rate similar to that of the termination. This is a radical coupling reaction between very stable polymer radicals. When a solution of p-QDM 1 is heated to a temperature higher than -78°C, in addition to the insoluble high molecular weight polymer, some soluble low molecular weight products such as a cyclophane 15, cyclic trimer 19, cvclic tetramer, 1.4-bis(2'-p-toIylethyl)benzene and olisoniers are obtained."^ Furthermore, when a solution ofp-QDM 1 at -78°C is added dropwise to a hot inert solvent such as toluene at 100°C a cyclophane 15 is obtained in a good yield."' p-QDM 1 does not copolymerize with conventional olefinic monomers at -78°C in the usual way that both monomers are mi.xed, but the homopolymers of p-QDM 1 and the •» 1 conventional monomer are obtained.' However, when a solution of p-QDM 1 at -78°C is added to copolymer can be produced.""' When oxygen or air is bubbled through a solution of p-QDM 1, p-QDM 1 is copolymerized with oxygen to yield poly-p-QDM peroxide 20 with an oxygen content ranging from 1 to 23% molar ratio of p-QDM to oxygen from 31:1 up to 1:1).'" The r ' ' 1 1 »• "! —CH2—O-O-j - n - - n 20 polymerization of p-QDM 1 is not influenced by conventional chain transfer agents such as carbon tetrachloride, chloroform, p-cumene, nitrobenzene, and hydroquinone.^^ When a three-fold excess of thiophenol, a highly reactive chain transfer agent, is added to a solution ofp-QDM 1, a telomer with a 21:1 ratio ofp-QDM 1 to thiophenol units is obtained."' 48 It was pointed out that the flash pyrolysis method ofp-xylene has several limitations"'^, i.e. (I) at most 25% yields of/7-QDM 1 are obtained the extreme pyrolysis temperature of 1150°C'°; (2) the polymers obtained are loosely cross-linked/ and (3) the vapor-deposited polymeric products formed by this method are contaminated with 10-20% of low molecular weight bv-products.'^ ''^ As an alternative to the pyrolysis of p-xylene, Fawcett found that degradation of p-xylyltrimethylammonium hydroxide (21) can take place at temperatures as low as 100°C, and the immediate and concurrent polymerization of the monomer affords linear, soluble ^nmesoh I 'lOO'C ^ 7 21 poly-/?-QDM 7 in high yields.""^ This method was successfully applied to 5-me±yl-2furfluyltrimethylammonium hydroxide (22a) and 5-methyl-2-thienyltrimeth- ylammonium hydroxide (22b) to obtain 2,5-dimethylene-2,5-dihydroflu:an (23a) and 2,5-dimethylene-2,5-dihydrothiophene (23b), respectively.'"^ Both monomers are very X X 22a: X=0 23a: X=0 22b: X=S 23b: X=S reactive and they either polymerized or form a heterocyclophane, crystalline cyclic dimer." This method is widely applicable to the synthesis of other /7-QDM polymers substituted with groups which are insensitive to the strongly basic medium, e.g. poly-2,5-dimethoxy-/7-xyl- ylene, which can be hydrolyzed to poly-2,5-dihydroxy-/7-xylylene.''^ An alternative 49 preparation of both the fliran monomer 23a and the thiophene monomer 23b by flash vacuum pyrolysis (F\T) from their corresponding benzoates was developed by Trahanovsky and workers'" . Both the furan monomer 23a and the thiophene monomer 23b'" can be isolated at -78°C. q c\/o V ^o Ph ^ * benzoic acid 23a: X=0 23b: X=S A much better method for preparing poly-p-xylylene (7) was subsequently developed by Gorham in which [2.2]paracyclophane (15) is pyrolyzed in a vacuum (-0.1 torr) at 600°C and the pyrolyzed gas is condensed on a glass or metal surface maintained below 30°C to 600°C 0.1 ton- is 7 yield a tough, transparent polymeric film.""® This pyrolysis of cyclophane 15 under milder and more readily controlled conditions, was described by Szwarc and Errede which resulted in almost a quantitative preparation of the polymer containing less than 1% carbon tetrachloride extractable material, most of which is unreacted dimer 15. The polymer film obtained is readily soluble in chlorinated biphenyls and benzyl benzoate at temperatures above 200°C, indicating that it is linear and free from cross-linking. This process has much greater advantages than the Szwarc-Errede pyrolysis of/7-xylene. Due to the milder pyrolysis temperature the vapor-coating process may be applied to the preparation of a variety of substituted /?-QDM polymers. The best laboratory preparation for cyclophane 15 is probably the pyrolysis of p-xylyltrimethylammonium hydroxide (21) as described by Weinberg and Fawcett.^' Pollart 50 had developed a solvent quenching technique for the synthesis of cyclophane 15."'° The condensation ofp-QDM 1 vapor directly into an organic solvent at a temperature of 50-200°C results in the formation of cyclophane 15 in a yield higher than 90%. Commercially, Union Carbide makes cyclophane 15 by the 900°C rapid pyrolysis of y \j Lit cilw Ox ocCJXix lUixUA^ci. Oj^ ^-OliUwixoaciUii ui uiw vapOi ui Jiii Oi^uiu^ .suivwiiL such as /^-xylene at 50°C to produce cyclophane 15 in 8-10% yield with only 0.1% polymeric material."®' Gorham prepared about 30 types of substituted paracyclophanes including the dichloro, dibromo, dicyano, dimethyl, diethyl, and tetrachloro derivatives for the preparation of polymers of the respective substimted /?-QDM's.'' The various substimted p-QDM monomers condense and polymerize on the surface at temperatures lower than the threshold condensation temperature which is related to the molecular weight and volatility of the respective monomer. The threshold condensation temperature is defined as the highest temperature of the surface on which the p-QDM monomers condense and polymerize at an appreciable rate. At normal pressure (about 0.1 mm Hg) the threshold temperatures are 30°C forp-QDM 1, 60°C for 2-methyl-/?-xylylene, 90°C for2-ethyl- and 2-chloro-p-xylylene and 130°C for 2-cyano-, 2-bromo-, and dichloro-/7-xylylene. The mechanism of the vapor-coating process of unsymmetrical cyclophane has been studied."• *3 The pyrolysis gas from mono-acetyl-cyclophane 24 is initially led through a glass tube maintained at 90®C and subsequently through another glass tube kept at 20°C. The polymer deposited at 90°C has been identified as poly-acetyl-;j-xylylene 25 and the polymer deposited at 20°C has been identified as poly-/?-QDM 7 on the basis of its elemental analysis 51 Ac Ac ' yCHz— f 24 25 and IR spectrum and by properties such as their melting point and solubility in organic solvents. The enhanced reactivity of paracyclophane can be seen as the result of its ring strain. However, the ringstrain is released as soon as the bond on one side is broken. Gorham acknowledges that this does not answer the question as to whether both bonds in the cyclophane are broken simultaneously or sequentially. In fact, it should be pointed out that by pyrolyzing cyclophane 15 at 200-250°C, Cram has estabUshed unequivocal evidence for the breakage of only one bond."*" It should also be pointed out that the concerted cleavage .coame 200 - 250°C —; .CO-,Me 15 MeOiC coome of cyclophane 15 to the p-quinodimethane is a [tt^s -i-ti^s] process which is orbital symmetry forbidden."*^ These results reasonably suggest that the acetyl-cyclophane 24 is cleaved to a ring-open biradical then to /?-QDM 1 and acetyl-p-QDM 26. The subsequent Sectional polymerization which then take place depends upon the threshold condensation temperatxires of these fragments. 20°C 1 7 ac Ac ! ! 90°C • 25 26 The polymerization has a "living" character, which does not mean that this polymerization is truly a living polymer but the growing polymer chains are terminated by radical species with lifetimes of days, depending on the monomer structure, as proved by ESR spectroscopy. For example, the apparent half-life of poly-/7-xylylene (7) radical is 20 min and of poly-2.5-dichloro-p-xylylene (9) radical is 21 h."^ Immediately after its preparation by the vapor-coating process, the poly-p-xylylene was found to be paramagnetic (radical concentration of 5-10 x lO" mol g"').'"' The mechanical properties of poly-p-xylylenes, such as tensile strength and tensile modulus, can be improved by termination of radical chain ends by chain transfer agents or annealing before contact with oxygen.^-"'^'-"'® Non-Pyrolytic Preparation p-[(TrimethylsiIyI)methyl]benzyltrimethylammonium iodide (27) can be decomposed at room temperature with tetrabutylammonium fluoride (TBAF) in acetonitrile to give poly-p-QDM 7 (51% yield) and cyclophane 15 (6% yield), or at refluxing temperature to give 50% cyclophane 15.'*' 33 ^ CH3CN I • 7 + 15 ^tms 27 Amorphous, low molecular weight (-3000) poly-p-QDM (7) was synthesized by Wurtz-type coupling reaction of l,4-bis(halomethyl)benzenes 28 and different coupling reagents in solution. Zinc'", magnesium"^^, .^odium"^'^°'^\ phenyllithium". iron or nickel or cobalt or zinc suspended in water or Urushibara Nickel^', chromium(II) chloride'', or naphthalene alkali^' was used as the coupling reagent. Molecular weights of poly-p-QDM's chjx ^ ^ ^ ch2x 28 obtained by this route are limited by the insolubility of poly-/?-QDM 7 at moderate temperatures. This reaction was improved in various ways to give satisfactory yields of the crystalline polymer."°"^^ The role of/j-QDM 1 as an intermediate in these coupling reactions was already recognized by Thiele and Balhom.'" Interestingly, poly-m-xylylene (29) was obtained by reaction of l,3-bis(bromometh- yl)benzene (30) with CrCli as well as copol>'mers by reaction with l,4-bis(bromomethyl)ben- zene, which indicates that the reaction does not essentially proceed via a quinoid species as CrCl2 j ^ ' I —i—clv^^ch2-p CH^Br [ . ^ 30 29 54 intermediate since m-xylylene (31) can not form a quinodimethane.^"^ This would implicate a stepwise growth mechanism via poly-recombination of benzylic radical species. Further • ch2 31 evidence was obtained by previous reactions of 30 in the presence of sodium and the formation of poly-m-QDM 29." Similarly, poly-m-QDM 29 was obtained by reaction of 30 in the presence of reduced iron suspended in water. Small amounts of [2.2]metacyclophane (32) were obtained as side product.'' 30 ^ 29 - 32 Direct Observation More recently the question of biradical 16 verses quinoid 1 structure was examined with regard to p-xylylene. Low temperattu-e (-80°C) solution spectra^® (IR, UV, NMR) indicate that the quinoid structure is predominant and that the biradical, if formed, is very short-lived. No ESR signals were obtained and the NMR signals were not broadened. In addition the sohd state photoelectron spectrum of /7-QDM 1 were consistent with the quinoid structure.'^' ^ Other reactive/j-QDM's have been spectroscopically observed. 1,4-Naphthaquino- dimethane and 9,10-anthraquinodimethane were observed by 'H NMR, UV, and IR spectroscopy using methods similar to the one used for /?-QDM 1.'^ Photoelectron spectra 55 were obtained of 2,3-dimethyl-/?-xylylene^' and 2,5-dimethyl-/7-xyl-ylene.^''^' The ER spectrum of 7,8-dichloro-p-xylylene was acquired by trapping the p-QDM on a N: matrix.^^ Both the IR and UV spectra were obtained for 7,7,8,8-tetra-chloro-p-xyI-ylene.^ 7,7-DiphenyI-/i-xyIylene was prepared by basic elimination of hydrogen chloride or hydrogen bromide using pyridine. As a dilute solution, an UV,^is spectrum was obtained.^* Summary p-Quinodimethanes, in particularly p-xylylene (1), have received considerable attention in the literature concerning its reactivity and their use as a monomers for the commercial polymer Parylene. p-QDM's have been prepared by pyrolysis or by elimination reactions. The most common method of preparing/?-QDM's is the pyrolysis of [2.2]paracyclophanes. Many p-QDM's are reactive and form polymers upon condensation of a surface. Although the mechanism of polymerization is uncertain, it is believe to involve a dimeric diradical. /7-QDM 1 and several other reactive/j-QDM's have been directly observed by IR, UV, and 'H NMR spectroscopy. References (1) For reviews on p-quinodimethanes see: (a) Errede, L. A.; Szwarc, M. Quart. Rev. 1958, /2, 301. (b) Luzanov, A.V.; Vysotski, Y. B. Journal of Structural Chemistry 1976,17(6), 945. (c) Luzanov, A. V.; Pedash, Y. F. Tear. Eksp. Khim 1977,13(5), 661. (Russian); Chem. Abstr. 1977,55,21921. (d) Iwatsuki, S. Adv. Polym. Sci. 1984, 58 (Polym. React.), 93. (e) Mulvaney, J. E. Poly. Sci. Technol. 1984,25 (New Monomers Polym.), 311. (f) Iwatsuki, S. "Polymerization and Polymers of Quinonoid Compounds" in The Chemistry of Qiiinoniod Compounds, Patai, S., Rappoport, Z., Eds.; John Wiley and Sons: New York; Vol. 2,1988; pp 1067-1111. (g) Yongjun, Y.; Matai, D.; Huixong, L.; Haiping, X.; Xumin, H. Gongneng Gaofenzi Xuebaii 1994, 7(2), 195. (Cliinese); Chem. Abstr. 1994,122, 215228. (h) Itoh, T.; Iwatsuki, S. Macromol Chem. Phys. 1997,198(7), 1997. (i) Greiner, A; Mang, S.; Schafer, 0.; Simon, P. Acta Polymer. 1997, 48, 1. (2) This review is not comprehensive, but is intended to give the reader a general introduction to p-quinodimethanes. (3) Based on dimerization and oligimerization. See (a) Trahanovsky, W. S.; Chou, C.-H.; Fischer, D. R.; Gerstein, B. C. J. .4m. Chem Soc. 1988,110, 6579. (b) Lorimor, S. P.; Trahanovosky, W. S. "Evidence for the Diradical Intermediates in the Oligomerization of/?-Quinodimethanes" 214''' ACS National Meeting, Las Vegas, NV, September 7-1,1997, ORGN-143; .American Chemical Society, Washington D.C. (c) Chapter three of this dissertation. (4) Skancke, A.; Skancke, P. N. in "General and Theoretical .A.spects of Quinones" in The Chemistry of Quinoniod Compounds, Patai, S., Rappoport, Z., Eds.; John Wiley and Sons: New York; Vol. 2,1988; pp 1-28. (5) For a review on o-quinodimethanes see; Segura, J. L.; Martin, N. Chem. Rev. 1999, 99,3199. (6) For a review on quinone methides see; Arvidson, K. B. Ph.D. Dissertation, Iowa State University, .Ames, 1998. (7) As of July 2000 over 1000 review articles were retrieved from the CAS database on the subject of "quinone". For the five most recent reviews see: (a) Patil, A. 0. Chem. Innovation 2000,20,19. (b) Mannervik, B.; Etahadieh, M.; Fernandez, E.; Gustafsson, A.; Hansson, L. O.; Hubatsch, L; Jemth, P.; Johansson, A.-S.; Larsson, A.-K.; Nilsson, L. O.; Olin, B.; Ridderstrom, M.; Stenberg, G.; Tronstad, L.; Widersten. M. Clin. Chem. Enzymol. Commim. 2000, 5, 189. (c) Oppermann, U. C. T.; Maser, E. Toxicology 2000,144, 71. (d) Lash, T. D. Synleti 2000, 279. (e) Harvey, R. G.; Penning, T. M.; Jarabak, J.; Zhang, F.-J. Polycyclic Aromat. Compd. 1999.16. 13. For a general review see: The Chemistry of Quinoid Compounds, Vol. I and n. Patai, S.; Rappoport, Z., Eds. John Wiley and Sons: New York, 19S8. (8) (a) Gorham, W. F. In Encyclopedia of Polymer Science and Technology, Gaylord, N. G., Bikales, N. Eds.;\Viley-Interscience: New York, 1971; Vol 15, pp 98-113. (b) Niegish, W. D. In Encyclopedia of Polymer Science and Technology, Gaylord. N. G., Bikales, N. Eds.;Wiley-Interscience; New York, 1971; Vol 15. ppl 13-124. (c) Lee, S. M. in Kirk-Othmer Encyclopedia of Chemical Technology,3^ ed.; Wiley: New York 1983, Vol 24, pp 744-771. (d) Beach W. F.; Lee. 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(62) Koenig, T.; Southworth, S. J. Am. Chem. Soc. 1977, 99, 2807. (63) Zuev, P.; Sheridan. R. S. J. Am. Chem. Soc. 1993. 115. 3788. (64) (a) Pebalk, A.V.; Kardash, I. Ye.: Kozlova, N. .A..; Pravednikov, .A.. N. Polymer Sci. USSR 1980, 21, 824. (b) Gilch, H. Angew. Chem. Int. Ed. 1965, 4, 598. (65) Braun, D.; Platzek, U.; Hefter, H. J. Chem. Ber. 1971,104, 2581. 62 CHAPTERS. ROOM TEMPERATURE OBSERVATION OF /;-XYLYLENES BY NMR AND EVIDENCE FOR DIRADICAL INTERMEDIATES IN THEIR OLIGOMERIZATION' A paper to be submitted to the Journal of Organic Chemistry Steven P. Lorimor and Walter S. Trahanovsky Abstract p-Quinodimethanes (/7-QDM's) are reactive molecules that have been invoked as transient intermediates in a number of reactions. Dilute solutions of benzene-based p-QDM's,/7-xylylene (1), a-methyl-p-xylylene (11), and 2,5-dimethyl-p-xylylene (12), can be prepared by fluoride-induced elimination of trimethylsilyl acetate from the appropriate precursor. It has been found that these solutions are stable enough to allow these reactive /?-QDM's to be observed by 'H NMR spectroscopy at room temperature. For the first time, the '•'C N^IR spectrum of/7-QDM 1 was observed. After several hours at room temperature, these p-QDM's form dimers, trimers, and insoluble ohgomers. Formation of trimers provides evidence that /j-QDM's 1,11. and 12 dimerize by a stepwise mechanism involving dimeric diradicals as intermediates. Introduction p-Quinodimethanes (p-QDM's) are reactive molecules that have been invoked as transient intermediates in a number of reactions. p-Xylylene (1), the parent benzene-based p-QDM, was first proposed as an intermediate in the pyrolysis of p-xylene that yielded poly-/?-xylylene." Errede was able to prepare solutions ofp-QDM 1 at -78°C by 63 1000 °c ^ -h, ——ch2-«\ ,>-ch2—i— dissolving thep-xylene pyrolyzate in a cold, well-stirred solvent." Errede and Szwarc" suggested that the polymenzation of p-QDM 1 occurs via the initially tbrmed diradical 2. i: ^ •- —- il Gorham found that heating [2.2]paracyclophane, dimer 3, in the gas phase formed what he suspected to be p-QDM 1 and when this vapor was allowed to condense on a cool surface, it formed polymer." 500 °c I <1 mm Hg Over the past several decades our group has studied the mechanism of oligomerization of other o- and p-QDM's including ones based on ftiran and ones based on thiophene. Furan-based o-QDM 4a can be prepared by flash vacuum pyrolysis (FVP) of 2-methyl-3-furylmethyl benzoate.^ Upon standing, fiiran-based o-QDM 4a dimerizes nearly quantitatively to the head-to-head, [4 -r- 4] dimer 5a.^ Chou and Trahanovsky probed the mechanism of dimerization with deuterium labeling of the a-positions and found that 64 o „ ^ ^o -PhCOjH 0^\^-^0 4a 5a [4+4] dimer a significant inverse isotope effect at the 3-methylene position which supports a step wise mechanism involving diradicals at the 2-methylene. By substitution of a bulky rerr-butyl group at either of the a-positions, Trahanovsky was able to demonstrate that the 3-methylene is more reactive than the 2-methylene.® The 2-substituted o-QDM 4b has a similar rate of dimerization to the unsubstimted o-QDM 4a. The 3-substituted o-QDM 4c does not form dimers and is stable for days at room temperature. (HaChC 4b 4c Although triplet oxygen is normally slow to react with olefins, thiophene-based p-QDM 6a' and fliran-based o-QDM 4a'° have been shown to react rapidly with "Oz to give cyclic products. 9 3/^ 1 S 2 O2 0 O 2 ^ s 0 0 6a .7 / ^0, y~~o 4a 65 Leung and Trahanovsky" reported that 2-ethyIidene-3-methylene-2,3-dihydrofliran (4d) dimerizes to give rise to two [4+4] dimers 5b, four [4+2] dimers 5c, and one intramolecular disproportionation dimer 5d. Identification of the intramolecular disproportionation product 5d provides additional suppon for the diradical intermediate. .^6 - ^o-^v<"'o ' .^0 chs / ,/ 4d 5b 5c 5d -30% -67% -2% Furan-based/?-QDM 7 can be prepared by FVP of 5-methylfurfiuyl benzoate.''" Upon standing fiiran-based p-QDM 7 forms dimer 5e, polymer, and only a trace amount of trimer 8a.One proposed explanation for the low yield of trimer 8a is that once the dimeric 0 n I dimer Se polymer •• ^ "ZmrT-phcoah '• '' only a trace of trimer 8a diradical is formed, it rapidly closes to dimer 5e rather than reacting with a third molecule of /j-QDM 7 to form a trimeric diradical (Scheme 1). Another explanation is the trimeric Scheme 1 66 diradical reacts with another molecule of monomer to form polymer faster than closing to trimer 8a (Scheme 2).'" Scheme 2 Fast A '! L J n 2.5-Dimethylene-2. 3-dihydrothiophene, thiophene-based /?-QDM 6a, can be prepared from the flash vacuum pyrolysis (F\T) of 5-methyl-2-thiophenemethyl benzoate.'" Upon standing thiophene-based /j-QDM 6a forms dimer (14.7%), trimer 8b (44.3%), tetramer (0.68%), and oligomers. It has been proposed that trimer formation provides firm evidence for the existence of dimeric diradicals.'" 8b Further evidence for a dimeric diradical was found in trapping with the furan-based p-QDM 7 to form a mixed trimer 8c. 67 dimer 6a trimer tetramer oligomers 6a S- 8c From the methyl derivative 6b, prepared by FVP of 5-ethyl-2-thiophenemethyl benzoate, acyclic dimers 5f and 5g were observed.'' Their formation is reasonably explained by intramolecular disproportionation of dimeric diradicals. This provides additional evidence for the dimeric diradicals. a ./ w ,/ "2 6b 5f. R,= Me. R, = H 5g. R,= H. R2'=Me Ito used a fluoride induce 1,6-elimination of trimethylsilyl iodide and trimethylamine from [p-[(trimethylsilyl)methyl]benzyl]trimethylammonium iodide (9a) to yield dimer 3 and polymer.'"* o-Xylylene (10) can be generated also by a fluoride induced 1, 4-eliniination of -n(ch3)3 i CH3CN. 25 °C "TMS 9a trimethylsilyl iodide and trimethylamine from [ o-[(trimethylsilyl)methyl]benzyl]trimethyl ammonium iodide (9b).o-QDM 10 rapidly dimerizes to [4 + 2] dimer 5h and [4 -i- 4] dimer 5i in a ratio of 11:1.'^® 68 N(CH3)2 I x p' , rh-rwch3cn.25°c r)^°r. "-' TMS 9b 10 5h Si In order to more fully investigate the possibility of a dimeric diradical intermediate in the oligomerization of benzene-based p-QDM's, dilute solutions ofp-QDM 1, a-methyl-/7-xylylene (11), and 2,6-dimethyl-/7-xylylene (12) were prepared and their oligomerization was studied. 1 11 12 Results p-Xylylene (1) Oligomerization Studies. [p-((Trimethylsilyl)methyl)phenyl]methyl acetate (13) was prepared fromp-tolulic acid by reactions shown in Scheme 3. Sctieme 3 CO2H 1)LDA AcCI ^ 2)TMSC1 ^ . O ^ i ^ ref23 ref24 ^ ^tms 13 ;?-Xylylene (1) was prepared as a dilute solution in CD3CN (ca. 10"^ M) by the fluoride induced elimination''* of trimethylsilyl acetate from acetate 13. Due to the stability of this dilute solution, we were able to obtain the NMR spectrum (Figure 1) at room 69 AFTER 19 HOURS AFTER 6 HOURS AFTER IS MINUTES 1 13 13 I before adomon -i - PPM Figure 1. H NMR spectrum (400 MHz, CD3CN) of reaction progress of /j-xylylene (1) in degassed CD3CN. (3,13, and 14 are compound numbers given in the text, I: internal standard, naphthalene, M: methylene chloride, O: oligomers) 70 I 0 TBAF.CD3CN f| I ^ L i! Room lemperature ^tms 13 1 temperature'^ whereas the previous reports were obtained at about -80 °C.'' By studying the 'H NMR spectrum over time, we were able to estimate the first half-life to be approximately 4 h. With a more concentrated solutions ofp-QDM 1 (—IC'' M) and reduced temperature (-40°C), an '^C NMR spectrum of p-QDM 1 was obtained for the first time. The product mixture that forms from the solution of p-QDM 1 varies based on the care taken to exclude oxygen (Table 1). Under standard fireeze-pump-thaw degassing conditions, dimer 3, [2.2.2]paracyclophane, trimer 14, products that appear Table 1. Yields of [2.21Paracyclophane (3) and [2.2.2]Paracyclophane (14) from /7-XyIylene (1). |imol 1 umol 3 % yield [imol 14 % yield Oxygen adducts 1.1^ 0.077 7 0.00015 0.4 Present 1.5=* 0.11 15 0.025 5 Present 1.3" 0.23 35 0.031 7 Trace ^Results of/>-xylylene 1 in degassed CD3CN. ''Result of p-xylylene 1 in deoxygenated CD3CN. 71 Degassed (' ;• !j CDsCN^ ^ ^ Insoluble ^ Oxygen " -=\ Oligomers " Adducts 1 3 14 to be oxygen adducts, and insoluble oligomers were observed. The 'H NTVIR spectrum of the oxygen adducts (Figure 2) was compared to the products prepared in an oxygenated solvent. 'H NMR spectra of both products mixtures showed signals near 54.5. j Oxygenated CDjCN^ Oxygen ^ Adducts When /7-QDM 1 is prepared in a solution that was rigorously freed of oxygen, its product mixture contained dimer 3, trimer 14, and what appear to be insoluble oligomers of p-QDM 1 (Table 1). The 'H NMR spectrum (Figure 3) of this mixture did not contain signals at 5 4.5. il Deoxygenated ^ !| CD3CN j V—/ ^ ^ Insoluble ^ \ "^5^ * Oligomers vj' i 14 a-Methyl-/7-xylylene (11) Oligomerization Studies. In an attempt to obtain additional evidence for dimeric diradical intermediates, the methyl derivative, a-methyl-p-xylylene (11) was studied. l-[p-((TrimethyisilyI)methyl)phenyl]ethyl acetate (15) was prepared from 4-[(trimethylsilyl)methyl]benzyl alcohol by reactions shown in Scheme 4. 72 I I . I . 1 1 * ' • • 1 • • • • I r j 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 Figure 2. 'H NMR spectrum (400 MHz, CD.CN) ofp-xylylene (1) and oligomerization products in oxygenated CD.GST. (A: oxygen adducts, I: internal standard, naphthalene, M: methylene chloride) 73 m I I 14 , 1 jllu. ! O j I ; OO I I I "O I o fsl I o ' : — • I o I I o o 8.0 7.0 6.0 5.0 4.0 Figure 3. 'H NNIR spectrum (400 MHz. CD3CN) ofp-xylylene (1) products in deoxygenated CD;,CN. (3 and 14 are compound numbers given in the text, I: internal standard, naphthalene, M: methylene chloride) 74 Scheme 4 HO. ho^ PCC AcCI ^ ch2ci2 MeMgBr pyridine ref33 0 I ^tms ~TMS TMS TMS 15 A dilute solution (10'"' M) ofp-QDM 11 was prepared by a similar fluoride-induced elimination from acetate 15. The 'H NMR spectrum ofp-QDM 10 was also obtained at TBAF. CD3CN Room Temperature TMS 15 11 room temperature (Figure 4). Similar to the parent system, the presence of oxygen in the sample has a notable effect. When solutions of/7-QDM 11 are prepared in the degassed CD3CN and analyzed by 'H NMR spectroscopy (Figure 5), cyclic dimers, cyclic trimers, and oxygen containing products are observed. When samples ofp-QDM 11 were prepared with careful exclusion of oxygen (Figure 6), the products are cycUc dimers 16 (14.9 % yield), cyclic trimers 17 (14.9 % yield), and insoluble oligomers (Scheme 5). We did not observe any evidence of an acyclic dimers 18 by NMR spectroscopy or GC/MS. 75 Figure 4. 'H NMR spectrum (400 MHz, CD3CN) of a-methyl-p-xylylene (11) in degassed CD3CN. a-Methyl not shown. (I: internal standard, naphthalene, M: methylene chloride, O: oligomers) 76 mi • 1 — 1^ •• i ^ o i cn >n co c>< in 1 lo —I o I 1-^ i "v j D 8.0 7.0 6.0 5.0 4.0 Figure 5. NMR spectrum (400 MHz, CD3CN) of product mixture of a-methyl-/?-xyIylene (11) in degassed CD3CN. (A: oxygen adducts, I: internal standard, naphthalene, M: methylene chloride) 77 M 16& 17 0.0 9.0 8.0 7.0 6.0 5.0 4.0 Figure 6. 'H NMR spectrum (400 MHz, CD3CN) of product mixture of a-methyl-p-xylylene (11) in deoxygenated CD3CN. (1 and 14 are compound numbers given in the text, I: internal standard, naphthalene, M: methylene chloride) 78 Scheme 5 24a. R,= Me, R, = H 24b. R,= H, R2 = Me X 11 R^'^-' 'R, 16a. R,= Me. R2 = H 18a. R.= Me. R-, = H 17a. R,=R-i= Me. R'5=R4 = H 16b. R.= H. R7 = Me 18b. R.= H. R7 = Me 17b. R.=r5=H. r2=r4 = Me 2,6-Dimethyl-p-x>'IyIene (12) Oligomerizatioa Studies. [3,5-Dimethyl-4-((trimeth- ylsilyl)methyl)phenyl]methyl acetate (19) was prepared from isophorone by reactions shown in Scheme 6. A fluoride induced elimination of trimethylsilyl acetate from acetate 19 yielded 2,6-dimethyl-p-xylylene (12). The 'H NMR spectrum ofp-QDM 12 wa^ obtained in CHjOAc TBAF. CD3CN Room Temperature ^tms 19 12 79 Scheme 6 HO HONHsCI AcCl, AC2O H.^.AC Pyridine Pyridine h3o' ref35 ref35 ref 35 1)NaN02. HCI 2)Na2C03 CN 1)lda H2SO4. HjO / 2)TMSC1 ref 38 \ ch^oh CHjOAc AcCI LAH Pyridine ref 24 ~TMS 'tms "TMS 19 degassed acetonitrile-c/i at room temperature (Figure 7). Upon standing, nearly equal amounts of head-to-head dimer 20 (7.7 % yield) and head-to-tail dimer 21 (7.3 % yield) were formed along with insoluble oligomers and a trace (1.3 % yield) of trimer 22a (Figure 8). / • •gassed CD3CN \ Insoluble Oligomers if A If 12 20 21 22ar R^—Me. R2—H 22b: ri=h. r2=me 80 20 :i :\ ^'lrt.xnoxw' i*»^f^^>^ "^v' "^1 i o i Figure 7. 'H NMR spectrum (400 MHz, CD3CN) of 2.6-dimethyl- p-xylylene (12) in degassed CDjCN. (20 and 21 are compound numbers given in the text, I; internal standard, naphthalene, M: methylene chloride, X: impurity) 81 >1 :u i2» 12a a '. a I' i o o I o o i 9 .= I o i 2 a li 6 ! o ' { e ' o i o s e I C I C t = I 3.0 :.o 5.0 Figure 8. 'H NMR spectrum (400 MHz, CD3CN) of product mixture of 2,6-dimeth- yl-/?-xyIylene (12) in degassed CD3CN. (20, 21 and 22a are compound numbers given in the text, I: internal standard, naphthalene, M: methylene chloride, X: impurity) Only one trimer was found in die GC\MS of the product mixture. Based on the 'H NMR spectrum, which shows three signals for aromatic hydrogens rather than just one, it can be concluded that trimer 22a, was formed. p-Xylylene (1) and 2,6-Dimethyl-p-xylyIene (12) Co-oiigomerization Studies. A mixture of ;7-QDM's 1 and 12 were prepared by fluoride induced eliminations from their respective acetates 13 and 19. The 'H NMR spectrum (Figure 9) of the mixture clearly shows the ratio ofp-QDM's 1 to 12 as being nearly 1 to 4. Upon standing. 82 mwh< Vmw i~l i°! Figure 9. 'H KVIR spectrum (400 MHz. CD3CN) ofp-xylylene (1) and 2.6-dimethyl- p-xylylene (12) in degassed CD3CN. (I: internal standard, naphthalene, M: methylene chloride) ch2oac R- TBAF. CDjCN Room Temperature 'MS IMS 13 19 12 p-xylylene dimer 3, mixed dimer 23, head-to-head dimer 20, head-to-tail dimer 21, and insoluble oUgomers were formed. We did not observe any evidence of trimers by 'H NMR spectrum (Figure 10) or GC/MS. 83 2u 21 10tf ..11 •• I ———»—^ ••! !•"•». ^ ^ , O (9 •OI— 'OO — OOJO—>0. ^•- >•> 0L0:0<~ — • !— |o'<9oee'oaot.j9|a, aio a • ee.so 3.C *.0 6.C 5.C ppa Figure 10. 'H NMR spectrum (400 MHz, CD3CN) of product mixture of /j-xylylene (1) and 2,6-dimethyl-/7-xylyIene (12) in degassed CD3CN. (3, 20, 21. and 23 are compound numbers given in the text, I: internal standard, naphthalene, M: methylene chloride) Ogassed CD3CN Discussioa /7-Xylylene (1) OUgomerization Studies. The fluoride induced elimination of trimethylsilyl acetate has proven to be an effective and mild means of preparing /j-QDM's. 84 Under these mild conditions, ;?-xylyIene (1) can be prepared as a dilute solution that persists for several hours at room temperature. With relatively stable solutions of/7-QDM's at room temperature, other reactions could be studied that might be unfavorable at reduce temperatures. In contrast to the pyrolysis preparations, reaction products are free of side products resulting from the pyrolysis of oligomers. Two pathways could form dimer 3: a concerted [6 - 6] cycloaddition of two molecules of/j-QDM 1 or formation of an initial dimeric diradical 2 followed by closure of the diradical. Formation of trimer 14 at room temperature is consistent with the trapping of diradical 2 byp-QDM 1. Since dimer 3 does not open to diradical 2 at room temperature,'® formation of dimer 2 must be stepwise, not concerted (Scheme 7). Scheme 7 i l Diradical 2 i ^ 25'C Concerted I // 14 Zwitterionic Intermediates. An alternative to the stepwise diradical mechanism is a stepwise mechanism invoKong zwitterionic intermediate 24.'^ It is known that reactions 1 1 24 involving zwitterionic intermediate are sensitive to changes in solvent polarity.Although acetomtnle-d:, was the only solvent used m this study, solutions of/>-QDM 1 m hexane, prepared from the pyrolysis of p-xylene, is known to form a trace amount of duner 3.'^ There is no evidence of products resulting from the zwitterionic intermediates reacting with the solvent. Furan-based o-QDM 4a is thought to dimerize by a diradical intermediate rather than a zwitterionic intermediate because it exhibited no change in rate of dimerization when the polarity of solvent was changed.' Further evidence against a zwitterionic intermediate is that unsymmetrical p-QDM 11 forms both head-to-head 16a and head-to-tail 16b dimers. Unsymmetrical molecules that dimerize by a zwitterionic intermediates often form head-to-tail dimers. It has been proposed that this occurs because the positive end of one molecule would be expected to attack die negative end of the other." a-Methyl-p-xylylene (11) Oligomerization Studies. a-Methyl-/?-xylylene (11) has a half-life similar or slightly longer than that of p-xylylene (1). Observation of trimers 17 again support the existence of a dimeric diradical 25. Due to the large number of isomers, it is difficult to determine if the reaction is regioselective. 2,6-Dimethyi-/;-xyIylene (12) Oligomerization Studies. Dimers 20 and 21 were formed in near equal amounts. Dimer 20 can arise from either dimeric diradical 26a or 26b whereas dimer 21 can only be formed from dimeric diradical 26c (Scheme 8). With its two 86 Scheme 8 flanking methyl groups, 2,6-dimethyl-p-xylylene (12) has one exocyclic methylene that is sterically hindered. This could have limited the possible dimeric diradicals that could form to the tail-to-tail diradical 26a because head-to-head diradical 26b and head-to-tail diradical 26c would have too much steric hinderance to form. Since dimers 20 and 21 were formed in nearly equal amounts, the steric hinderance of the two methyl groups must be minimal. Trimer 22a was observed by 'H NMR spectroscopy and GOMS but e\idence for trimer 22b was not found. Trimer 22b can only be formed from dimeric diradical 26c, were as trimer 22a can form from either dimeric diradical 26a , 26b or 26c (Scheme 9). Dimeric diradical 26c must close to dimer 21 faster than being trapped as nimers 22a or 22b. p-Xylylene (1) and 2,6-Dimethyl-^-xyIyIene (12) Co-oligomerization Studies. Bothp-QDM's 1 and 12 oligomerized at a similar rate and produced a mixed dimer 23. This suppons the theory that the flanking methyl groups ofp-QDM 12 are having little effect on its reactivity. It is unclear why trimers were not obser\-ed from the mixed p-QDM's smdies. where as trimers were observed in both of the isolated studies of/j-QDM's 1 and 12. Conclusion 'H NMR spectra of/7-xylylene (1), a-methyl-p-xylylene (11), and 2,6-dimethyl-/)-xylylene (12) have been observed at room temperature, which will possibly allow a more detailed smdy of their chemistry. For the first time, '""C NMR spectrum of /j-QDM 1 has been observed. The trapping of diradicals 2, 25, and 26 as their respective trimers is strong evidence thatp-QDM's 1,11, and 12 dimerize by a stepwise mechanism. The absence of acyclic dimer 18, which was present in the thiophene-based p-QDM 6b and fliran-based o-QDM 4d, can be explained by the conformational limitations found in the benzene-based/>-QDM's. Reactivity of/7-QDM's 1 and 12 are similar. The flanking methyl groups do not appear to reduce the reactivity of the /?-QDM 12. 88 Scheme 9 12 26a 27a 27b 22b 89 Experimental Section Methods and Materials. All materials were commercially available and used as received, except where indicated. 'H NMR spectra were recorded at 400 MHz unless noted otherwise. '""C NMR spectra were recorded at 100 MHz unless noted otherwise. The residual CHDiCN was used as the internal reference for all 'H NMR spectra unless noted otherwise. Both the GC and the GCMS analysis were done using a DB-5 column (30m, I.D. 0.32 mm. 0.25u film thickness). Elemental analyses were performed by Iowa State University Instrumental Services, Ames, LA.. 4-[(TrimethyIsilyl)methyl]benzoic Acid was prepared in a 25% yield from/7-toluic acid (29 mmol) as described by Stem and Swenton.""' 'H NN'IR (400 MHz, CDjCN) 6 9.293 (br s), 7.833 and 7.115 (AABB'q, y=8.4Hz), 2.207 (s), -0.032 (s); 'H NTvIR (400 MHz. CDCh) 5 7.95 and 7.07 (AA'BB'q, y=12Hz, 4H), 2.17 (s, 2H), -0.02 (s, 9H); '"'C NMR (100 MHz, CDjCN) 5 168.0. 148.4, 130.5, 129.0, 126.5. 28.0, -2.0. 4-[(TrimethylsiIyi)methylIbenzyI Alcohol was prepared in a 94% yield by lithium aluminum hydride (4 mmol) reduction of 4-[(trimethylsilyl)methyl]benzoic acid (1.8 mmol)with a procedure similar to the procedure outlined by Nystrom and Brown'"^ for the reduction of phenylacetic acid to p-phenylethanol. 'H NMR (400 MHz, CD3CN) 6 7.191 and 7.009 (AA'BB'q, J=1.6Rz), 4.507 (s), 3.320 (br s),2.107 (s), 0.001 (s); 'H NMR (400 MHZ, CDCI3) 5 7.20 and 6.97 (AA'BB'q, /=8Hz, 4H), 4.61 (s, 2H), 2.06 (s, 2H), 1.56 (br s, IH), -0.03 (s, 9H).[lit^' 'H NMR (CDCI3) 5 7.22 and 7.00 (ABq, /=8.0Hz, 4H, arom), 4.6 (s, 2H, CH2), 2.12 (s, 2H, CHi), 0.02 (s, 9H, SiMej)]; NMR (100 MHz, CD3CN) 6 140.3, 90 138.4, 128.8, 127.8, 64.7, 26.9, -1.8. .Ajial. Calcd for CuHigOSi: C, 67.98; H, 9.34. Found: C. 68.14; H,9.47. [/3-((TrimetliylsilyI)inethyl)phenyl]methyl Acetate (13). A solution of 109 mg of 4-[(triniethylsilyl)methyl]ben2yl alcohol (0.56 mmol) and 0.3 mL of pyridine (3.7 mmol) in 2 mL dry THF was prepared in a 10-mL flask. An argon atmosphere was placed over the solution. The solution was cooled to 0°C and stirred. A solution of 0.125 mL acetyl chloride (1.76 mmol) in 1 mL of dry THF was added dropwise to the alcohol solution by a syringe. The reaction mixture was allowed to warm to room temperature and was stirred for 2 h. The reaction mixture was added to 10 mL of ether. The ether solution was washed with brine twice then with a saturated solution of NaHCOs and finally with brine again. The ether solution was dried with MgS04 and concentrated under reduced pressure to get 115 mg (87%) of viscous oil. 'H NMR (400 MHz, cd3cn) 6 7.193 and 7.012 (AA'BB'q, y=8Hz. 4H), 4.985 (s, 2H), 2.160 (s, 2H), 2.006 (s, 3H), -0.047 (s, 9H); '"C NMR (100 MHz, cd3cn) 5 171.6, 141.8, 132.9, 129.2, 129.1,66.8,22.4,21.1,-2.0. Drying and Initial Degassing of cd3cn. Prior to use as a solvent in the preparation of p-QDM's, the cd3cn was distilled firom p2o5 under argon then degassed by repeated fireeze-pump-thaw cycles, except where indicated."® />-XyIyIene (1) in Degassed CD3CN. To a tear-shaped flask was added 7.6 mg of TBAF (24 ^mol). To a second tear-shaped flask was added 9.5 ^L of a 5.0 x 10"" M solution of naphthalene in ch2ci2 (0.48 jimol) and 9 (iL of an approximately 0.1 M solution of 13 in ch2ci2 (~1 ^mol). The ch2ci2 was removed at reduced pressures. The two flasks were placed into a nitrogen-filled glove bag. To the acetate flask was added about 0.8 mL of degassed cd3cn. The acetate solution was transferred to an NMR tube and the acetate was 91 quantified by 'H NMR. The NMR tube was returned to the glove bag. To the TBAF flask was added about 0.2 mL of degassed cd3cn. The TB.Af solution was added to the NMR tube. The sample was protected from light. The NMR tube was periodically removed from the glove bag for analysis by 'H NMR spectroscopy. 'H NMR (400 MHz, cd3cn, 20°C) 5 6.452 (s, 4H), 5.007 (s, 4H). [lit'" 'H N^,1R (60 MHz, THF-d^, -SO°C) 5 6.49, 5.10]. As the solution is allowed to stand, the p-xylylene (1) was consumed and [2.2]paracyclophane (3) (7 % yield), [2.2.2]paracyclophane (14) (0.4% yield) and insoluble oligomers were formed. 3: "H NMR (400 MHz, cd3cn) 5 6.484 (s, 8H), 3.046 (s, 8H).). [lit"' 'H NMR (300 MHz, cdci3) 5 6.48, 3.08]; GCMS mJz (relative intensity) 209 (5), 208 (35), M~), 105 (5), 104 (100), 78 (8), 77 (4). [lit"® GGMS mJz (relative intensity) 208 (16), 104 (100), 103 (100)]. 14: 'H NMR (400 MHz, cd3cn, 20°C) 5 6.678 (s, 12H), 2.903 (s, 12H). [lit"' 'H NMR (100 MHz, cdci3) 5 6.68 (Ar), 2.92 (CH.), 'H NMR (100 MHz, cd3od) 5 6.23 (Ar), 2.47 (ch2)]; GCMS xnJZ (relative intensity) 313 (15), 312 (77). 207 (14), 195 (12), 193 (31), 104 (100). [Ut'° GC/MS m/z (relative intensity) 312 (44), 118 (32). 117 (100), 115 (59), 105 (90), 104 (83), 91 (54), 77(35)]. NIVIR Spectrum of 1 at -40°C. The sample was prepared in a manner similar to the one reported above for the degassed CD3CN preparation of 1 except: (A) No naphthalene was added; (B) 7mg of Cr(acac)3 was added"'; (C) 35 mg of TBAF (111 jimol) was used; (D) 100 tiL of 0.1 M solution of 13 (-10 fimol) was used; (E) 30 s after the TBAF solution was added, the NMR tube was placed into a CH3CN/dry ice bath. '"C NMR (100 MHz, cd3cn, -40=C) 5 140.3, 129.8, 115.5. 92 /7-Xylylene (1) in Deoxygenated CD3CN. To a tear-shaped flask was added 7 mg of tetrabutylammonium fluoride trihydrate (TBAF) (22.2 umol). To a second tear-shaped flask was added 10 of a 4.7 x 10"" M solution of naphthalene in CH2CI2 and 10 jiL of an approximately 0.1 M solution of 13 in ch2ci2. The ch2ci2 was removed at reduced pressure. The two flasks were placed into a nitrogen filled glove bag. To the acetate flask was added about 0.8 mL of degassed CDjCN and to the TBAF was added about 0.2 mL of degassed cd3cn. The acetate solution was transferred to an NMR tube and the acetate was quantified by NMR. The NMR tube was returned to the glove bag. The acetate solution was poured into one tube of a two-tube reaction cell"'". The TBAF solution was added to the other tube of the cell. The cell was connected to a valved vacuum adapter. The two solutions were deoxygenated by two series of argon purging followed by three freeze-pump-thaw cycles. Once the cell had returned to room temperature, the cell was tipped to allow the TBAF solution to be added to die acetate solution. While still under a vacuum, the cell was wrapped in foil and placed into the glove bag. After 18 h, the reaction mixtiure, that contained some precipitate, was transferred to an NMR tube. The soluble products, 3 (35% yield) and 14 (7% yield), were quantified by NMR. ;7-XyIylene (1) in Oxj'genated CD3CN. The cd3cn was distilled from P2O5 under dry air then oxygen was bubbled through the cd3cn for 30 s. To a tear-shaped flask was added 7 mg of TBAF (22 [.imol). To a second tear-shaped flask was added 10 uL of an approximately 0.1 M solution of 11 in CH2CI2. The ch2ci2 was removed at reduced pressure. The dried cd3cn was added to the acetate flask and the TBAF flask, 0.8 mL and 0.2 mL, respectively. Both solutions were transferred to an NMR tube. 93 4-[(TrimethylsiIyI)methyI]benzaldehyde was prepared in a 96% yield from 4-[(triniethylsilyl)methyl]benzyl alcohol (3.93 mmol) with a procedure similar to the procedure outlined by Corey and Suggs.'"" 'H NMR (400 MHz, cd3cn) 5 9.889 (s), 7.727 and 7.198 (AA'BB'q, J^SUz), 2.238 (s), -0.017 (s). 'H NMR in cdci3 data are in good accord with publisxhedvalues.'-" '"C NMR (100 MHz, CD5CN) 5 192.9, 150.2, 134.1, 130.5, 129.5, 28.4, -2.0. l-[p-((TrimethyIsilyl)methyI)phenyI]ethaiioI. To a solution of 209 mg of 4-[(trimethylsilyl)methyl]benzaldehyde (1.09 mmol) in 3 mL of dry ether was added 0.4 mL of 3 M MeMgBr (1.2 mmol), dropwise. The reaction mixture was heated to reflux for 30 min. The reaction mixture was worked up in the normal manner to yield 197 mg (95%). 'H N'MR (400 MHZ. CD.CN) 5 7.186 and 6.975 (AA'BB'q, Y=8Hz). 4.727 (q, J=6.4Hz). 2.073 (s), 1.353 (d,/=6.4Hz),-0.034(5); '"C NMR (100 MHz, cd3cn) 5 143.3, 140.1. 128.7, 126.2,69.9,26.7,25.9.-1.9. Anal. Calcd for CizH^oOSi: C, 69.17; H, 9.67. Found: C, 69.29; H, 9.95. l-[f>-((TrimethylsilyI)methyI)phenyI]ethyI Acetate (15) was prepared in an 87% yield from l-|j?-((trimethylsilyI)methyl)phenyl]ethanol (50 mg, 0.24 mmol) with the procedure used for the above preparation of [p-((trimethylsilyl)methyl)phenyl]methyl acetate. ^H NMR (400 MHz, CDsCN) 5 7.196 and 7.002 (AA'BB'q, J=8Hz, 4H), 5.763 (q, /=6.8Hz, IH), 2.085 (s, 2H), 1.991 (s, 3H),1.456 (d,/=6.8Hz, 3H), -0.038 (s, 9H); NMR (100 MHz, cd3cn) 5 171.0, 141.3, 138.5, 129.0,126.8, 72.8, 26.9, 22.4,21.5, -1.9. a-MethyI-p-x\'lyIene (11) in Degassed CD3CN was prepared from acetate 15 (1.2 ^imol), TBAF (25 ^unol), and naphthalene (0.30 |xmol) with the procedure used for the above preparation of/?-xylyIene (1) in degassed cd3cn. 'H NMR (400 MHz, cd3cn) 5 6.713 (br d, y=9.6H2, IH), 6.466 (br d, y=9.6H2, IH), 6.314 (br s, 2H) 5.619 (q, J=8Hz, IH), 4.963 (br s, 2H), 1.848 (d, /=8H2, 3H). a-Methyl-/;-.xylylene (11) in Deoxygenated ch3cn was prepared from acetate 15 (20 umol), TB.\F (45 iimol) in 20 mL of CH;CN with the procedure used for the above preparation of/»-xylylene (1) in deoxygenated cd3cn. As the solution is allowed to stand, the a-methyl-/7-xylyIene (11) was consumed and three dimers 16, four trimers 17, and insoluble oligomers were formed. Dimer A 16 (7.3 % yield): GCMS m/z (relative intensity) 237 (6), 236 (31) M' 119 (29), 118 (100), 117 (66), 115 (24), 113 (3), 105 (2), 103 (3), 102 (3), 89 (7), 88 (6). Dimer B 16 (2.6 % yield): GCMS m/z (relative intensity) 237 (2), 236 (3) 119 (58), 118 (100), 117 (93), 115 (26), 103 (3), 90 (6), 89 (9), 88 (8). Dimer C 16 (5.0% yield): GCMS m'z (relative intensity) 236 (9) M~, 120 (3), 119 (36), 118 (97), 117 (100), 115 (24), 103 (3), 89 (12), 88 (7), 86 (6). Trimer A 17 (1.3 % yield): GC/MS m/z (relative intensity) 354 (2) M', 238 (16), 237 (100), 236 (60), 189 (2), 131 (2). 129 (2), 128 (3), 119 (42), 118 (56), 117(99), 115 (34), 107 (2), 103 (3), 90 (6), 89 (10), 88 (10), 86 (4). Trimer B 17 (2.2 % yield): GCMS m/z (relative intensity) 354 (6) M', 238 (15), 237 (100), 236 (51), 232 (2), 189 (2), 131 (2), 129 (2), 128 (2), 122 (4), 118(60), 117 (89), 115 (35), 106 (2), 105 (2), 103 (3), 89 (9), 87 (4), 86 (3), 77 (3), 75 (2), 74 (3). Trimer C 17 (1.1 % yield): GC/MS m/z (relative intensity) 354 (2) M', 238 (15), 237 (92), 236 (57), 131 (2), 128(3), 119(41), 118(56), 117(100), 115(37), 103 (2), 91 (4), 89(12), 88(10), 87 (5), 86 (4). Trimer D 17 (2.4 % yield): GC/MS m/z (relative intensity) 355 (2), 354 (7) M^, 353 (2), 239(2), 238 (15), 237 (97), 236 (36), 233(4), 232 (3), 189 (2), 131 (2), 128 (3), 119 95 (38), 118 (569), 117 (100), 115 (39), 112 (2), 108 (2), 105 (2), 103 (2), 91 (6), 90 (7), 89 (10), 88 (9), 86 (3), 77 (4), 76 (3), 74 (2). Isophorone Oxime was prepared in a 98% yield from isophorone (200 mmol) as described by Beringer and Ugelow.^^ 'H NMR (300 MHz, cdci3) 5 6.601 (s, IH), 2.103 (s, 2H), 1.996 (s, 2H) 1,855 (s, 3H), 0.960 (s, 6H). "H NN'IR (300 MHz, cdci3) 5 5.906 (s, IH), 2.363 (s, 2H), 1.945 (s, 2H) 1.807 (s, 3H), 0.971 (s, 6H). [\if^ 'HKMR (300 MHz, cdci3) £ isomer 5 5.92,2.38, 1.94, 1.81,0.98; Z isomer 5 6.63, 2.09, 1.98, 1.85, 0.97] 3',4',5'-TrimethyIacetanilide was prepared in a 20% yield from isophorone oxime (200 mmol) as described by Beringer and Ugelow.'"' 'H N^IR (300 MHz, cdci3) 5 7.112 (s, 2H), 2.235 (s, 6H), 2.123 (s, 3H) 2.099 (s. 3H); '"C NMR (75.4 MHz, cdci3) 5 168.2. 137.0, 134.9, 131.2,119.3,24.4, 20.6, 14.9. 3,4,5-Trimethylanilme was prepared in a 91% yield from 3',4',5'-trimethylacetanilide (34 mmol) as described by Beringer and Ugelow.'^ 'H NMR (300 MHz, cdci3) 6 6.383 (s. 2H), 3.434 (brs), 2.182 (s, 6H) 2.048 (s, 3H); -'C NMR (75.4 MHz, cdci3) 5 143.5, 137.3. 125.0, 114.7, 20.6, 14.4. [lit"' 'H NMR (90 MHz, cdci3) 5 6.4 (s. 2H), 3.5 (s, 2H), 2.2 (s, 6H) 2.15(s, 3H)]. 3,4,5-TrimeUiylbeiizonitrile was prepared in 66 % yield by the Sandmeyer reaction from 3,4,5-trimethylamline (13.6 mmol) with a procedure similar to the procedure outlined by Clarke and Read''® for the reaction of o-toluidine to o-tolunitrile. IR (neat) 2930, 2210,1610,1560 cm"'. 3,4^-TrimethyIbeiizoic Acid was prepared in a 61 % yield by acid-catalyzed hydrolysis of 3,4,5-trimethylbenzonitriIe (8.56 mmol) following a procedure similar to that 96 outlined by Clarke and Taylor' for the acid-catalyzed hydrolysis of o-tolunitrile acid to o-toluic acid. 'H NMR (400 MHz. cdci3) 5 7.726 (s, 2H), 2.319 (s, 6H), 2.218 (s, 3H) [lit"'' 'H NMR (90 MHz, cdci3) 5 9.2 (s, IH), 7.6 (s, 2H), 2.33 (s, 6H), 2.25 (s, 3H) ]; NMR (100 MHz, cdci3) 5 172.6, 142.0, 136.7, 129.2, 126.0, 20.6, 16.0. [lit^ '"C N'MR(25 MHz, CDCUj aromatic carbons only 6 141.9, 136.8, 129.2, 126.1] 3,5-Dimethyl-4-[(trimethylsiIyl)methyl]benzoic Acid was prepared in a 60 % yield from 3,4,5-trimethyibenzoic acid (2.01 mmol) as described by Stem and Swenton."" 'H NMR (300 MHz, cdci3) 5 7.707 (s, 2H), 2.266 (s, 6H), 2.233 (s, 2H) 0.015 (s, 9H) [lit^" 'H NMR (80 MHz, cdci3) 5 7.74 (s, 2H), 2.29 (s, 6H), 2.26 (s, 2H) 0.04 (s, 9H)] 3,5-Dimethyl-4-((trimethylsilyl)methyl]benz\'l Alcohol was prepared in a 92% yield by lithium aluminum hydride (1.23 mmol) reduction of 3,5-dimethyl-4-[(trimethylsilyl)methyl]benzoic acid (0.5 mmol) following a procedure similar to that outlined by Nystrom and Brown""* for the reduction of phenylacetic acid to P-phenylethanol that was used above for 4-[(trimethylsilyl)methyl]benzyl alcohol. 'H NTVIR (300 MHz, cdci3) 5 6.967 (s, 2H), 4.538 (s, 2H), 2.224 (s, 6H), 2.138 (s, 2H) 0.014 (s, 9H) [3,5-Dimethyl-4-((trimethyisUyI)methyl)phenyI]methyl Acetate (19) was prepared in an 85% yield from 3,5-dimethyl-4-[(trimethylsilyl)methyI]benzyl alcohol (0.4 mmol) following the procedure used for the above preparation of [p-((trimethylsilyl)methyl)phenyl]methyl acetate. 'H NMR (400 MHz, cdci3) 5 6.954 (s, 2H), 4.925 (s, 2H), 2.209 (s, 6H), 2.170 (s, 2H) ), 2.008 (s, 3H) -0.003 (s, 9H); '"C NMR (100 MHz, cdci3) 5 170.7,138.5,131.4,127.8, 117.4, 66.0, 20.4,20.2, 19.4,-1.1. GC/MS m/z (relative intensity) 264 (2) M", 249 (5), 207(5), 206 (14), 205 (100), 202 (9), 201 (6), 97 197 (3), 195 (2), 135 (3), 132(20), 130(15), 128 (13), 125 (7), 117(2), 115 (4), 113 (2), 112 (2). 2,6-DimethyI-/7-Y\'IyIene (12) in Degassed cd3cn was prepared from [3,5-dimethyI-4-((trimethylsilyI)methyl)phenyl]methyl acetate (19) (1.6 umol), TBAF (25 jimoi) and riaphthaiene (0.47 jimol) following the procedure used for the above preparation ofp-xylylene (1) in degassed cd3cn. 'H NMR (400 MHz, cdci3) 5 6.331 (s, 2H), 5.262 (s, 2H), 5.007 (s, 2H), 1.997 (s, 6H). As the solution is allowed to stand, the 2,6-dimethyl-/7ara-xylylene (12) was consumed and head-to-head dimer 20 (7.7 % yield), head-to-tail dimer 21 (7.3% yield), trimer 22a (1.3% yield), and insoluble oligomers were formed. Dimer 20: 'H NMR (400 MHz, cdci3) 5 6.166 (s, 4H), 3.292 (s. 4H), 2.850 (s, 4H), 2.020 (s, 12H); GC'MS m'z (relative intensity) 264 (13) M', 249 (10), 133 (19), 132 (100), 129(19), 128 (13), 117 (18), 115 (26), 114(12). Dimer 21: 'H NMR (400 MHz. cdci3) 5 6.348 (s, 4H), 2.97-2.93 (m, 4H), 2.85-2.80 (m, 4H), 2.210 (s, 12H); GC/MS m/'z (relative intensity) 264 (18) M", 249 (5), 133 (23), 132 (100), 129 (12), 128 (10), 117 (47), 115 (44). Trimer 22a: 'H NMR""^ (400 MHz, cdci3) 5 6.630 (s, 2H), 6.489 (s, 2H), 6.278(s, 2H); GC/MS m/z (relative intensity) 397 (2), 396 (6) M", 147 (4), 146 (2), 145 (2), 143 (2), 134 (3), 133 (26), 132 (100), 129 (9), 128 (6), 127 (3), 126 (2), 117 (19), 115 (21), 111 (2), 103 (2), 89 (5), 88 (10), 86 (2), 85 (2), 53 (2). />-XylyIene (1) and 2,6-Dimethyl-p-xyIyIene (12) in Degassed cd3cn was prepared from |>-((Trimethylsilyl)methyl)phenyl]methyl acetate (13) (0.67 |imoI), [3,5-dimeth- yl-4-((trimethyIsilyl)methyl)phenyI]methyl acetate (19) (1.5 jimol), TBAF (50 |imol) and naphthalene (0.47 jimol) following the procedure used for the above preparation of 98 p-xylylene (1) in degassed cd3cn. As the solution is allowed to stand, the p-xylylene and 2,6-dimethyl-para-xylylene (12) was consumed and/7-xylyIene dimer 3 (2.8 x 10"® mol), head-to-head dimers 20 (1.1 x 10" mol), head-to-tail dimer 21 (9.1 x 10'^ mol), mixed dimer 23 (1.6 X 10" mol), and insoluble oligomers were formed. Mixed dimer 23: 'H NMR (400 MHz. cdci3) 6 6.811 (d. ./=8Hz. 2H), 6.433 (d, ./=8Hz, 2H), 6.348 (s, 2H), 3.005 (s, 4H), 2.97-2.93 (m, 2H), 2.85-2.80 (m, 2H), 2.053 (s, 6H); GC/MS m/z (relative intensity) 236 (64) J^r, 233 (5), 132(100), 131 (30), 129 (24), 126 (7), 117(17), 115 (23), 114 (17), 113 (13), 112(9), 111 (5). References (1) Lorimor, S. P.; Trahanovsky, W. S. Book of Abstracts, 214''' National Meeting of the .Ajnerican Chemical Society, Las Vegas, NV, Sept 7-11, 1997; American Chemical Society: Washington, DC, 1997; ORGN-142. (2) a) Szware, M. Nature 1947,160,403. b) Szware, M. J. Chem. Phys. 1951. 16, 319. (3) a) Errede, L. A.; Landrum, B. F. J. Am. Chem. Soc. 1957, 79, 4952. b) Errede, L. A.; Hoyt, J. M. J. Am. Chem. Soc. 1960, 82, 436. (4) Errede, L. A.; Szware, M. Quarterly Review (London) 1958,12. 301. (5) Gorham, W. F. J. Polymer Sci., A-1 1966, 4, 3027. (6) Trahanovsky, W. S.; Cassady, T. J.; Woods, T. L.. J. Am. Chem. Soc. 1981,103, 6691. (7) Chou, C.-H.; Trahanovsky, W. S.. J. Am. Chem. Soc. 1986,108, 4138. (8) Trahanovsky, W. S.; Huang, Y.-c. J.; Leung, M.-k. J. Org. Chem. 1994,59, 2594. (9) Trahanovsky, W. S.; Chou, C.-H.; Cassady, T. J. J. Org. Chem. 1994,59,2613. (10) Huang, C.-S.; Peng, C.-C.; Chou, C.-H. Tetrahedron Lett. 1994, 35,4175. 99 (11) Chou, C.-H.; Trahanovsky, W. S. J. Org. Chem. 1995, 60, 5449. (12) Leimg, M.-k.; Trahanovsky, W. S.. J. .Am. Chem. Soc. 1995,117, 841. (13) Trahanovsky, W. S.; Park, M.-G. J. Org. Chem. 1974, 39, 1449. (14) a) Trahanovsky, W. S.; Miller, D.L.; Wang, L. J. Org. Chem. 1997,d2, 8980. b) Wang, L., M.S. Thesis. Iowa State University, Ames. 1994. (15) a) Ito, Y,; Miyata, S.; Nakatsuka, M.; Saegusa, T. J. Org. Chem. 1989, 54, 2953. b) Leung, M.-k. Ph.D. Dissertation, Iowa State University, Ames, 1991. c) Leung M.-k.; Trahanovsky, W. S. J. Am. Chem. Soc. 1995,117. 841. (16) (a) Errede, L.A.. J. Am. Chem. Soc. 1961, 83, 949. (b) Trahanovsky, W. S.; Macias, J. R. J. Am. Chem. Soc. 1986,108, 6820. (17) The UV spectrum was reported at room temperatiu-e. See: Kaupp, G. .4ngew. Chem. Int. Ed. Engl. 1976,15,442. (18) Williams,D. J.; Pearson, J. M.; Levy, M. J. Am. Chem. Soc. 1970, 92, 1436. (19) Cram found that at 200°C, dimer 3 opens to diradical 2 which could be in turn trapped with dimethyl maleate or dimethyl flraiarate. The formation of diradical 2 was supported by the loss of the stereochemistry of the original diesters in their adducts. See: Reich, H. J.; Cram, D. J. J. Am. Chem. Soc. 1969, 91, 3517. (20) Gompper,. Angew. Chem. Int. Ed. Engl. 1969, 8, 312. (21) Errede, L. A.; Gregorian, R. S.; Hoyt, J. M. J. Am. Chem. Soc. 1960, 82, 5218. (22) (a) Sauer, J.; Sustmann, R. Angew. Chem. Int. Ed. Engl. 1980,19, 779. (b) Proskow, S.; Simmons, H.E.; Caims, T. L. J. Am. Chem. Soc. 1966,88,5254. (23) Johnston, 1. J.; Scaiano, J. C. Chem. Rev. 1989, 89, 521. (24) Roberts, D. W. Tetrahedron 1985, ¥7,4183. 100 (25) Stem, A. J.; Swenton, J. S. J. Org. Chem. 1989, 54, 2953. (26) Nystrom, R. F.; Brown, W. G. J. .Am. Chem. Soc. 1947, 59, 2548. (27) d'Alessando, N.; Albini, A.; Mariano, P. S. J. Org. Chem. 1993, 55, 937. (28) (a) Fischer, D. R. Ph.D. Dissertation, Iowa State University, Ames, la, 1990, pp 91-121. (b) Trahanovsky. W. S.; Arvidson, K. B. J Org Chem. 1996, 61, 9528 (29) The Aldrich Library of '"C and 'H FT NIvIR Spectra; Vol. 2, p 16; Pouchert, C. J., Behnke, J., Eds.; Ed. 1, Aldrich Chemical Company, jVIilwaukee, 1993. (30) Hefelfinger, D. T.; Cram, D. J. J. Am. Chem. Soc. 1971, 93, 4754. (31) Pierre, J.-L.; Baret, P.; Chautemps. P.; Armand, M. J. Am. Chem. Soc. 1981,103, 2986. (32) Tabushi, L; Yamada, H.; Yoshida, Z.; Oda, R. Terahedron 1971. 27, 4845. (33) Wehrli. F. W.; Marchand, A. P.; Wehrli, S. Interpretation of Carbon-13 NMR Spectra, 2nd ed.; John Wiey and Sons: New York, 1988; pp 223-226. (34) Reaction cell resembles a cow-type distillation receiver. For a complete description ofthe cell, see: refTb. (35) Corey, E. J.; Suggs, J. W. Tetrahedron Lett. 1975, 31, 2647. (36) Xu, Y.-C.; Wulff, W. D. J. Org. Chem. 1987, 52, 3263. (37) Beringer, F. M.; Ugelow, L J. Am. Chem. Soc. 1953, 75, 2635. (38) Underwood, G. R.; Bayoumy, K. E. J. Am. Chem. Soc. 1982,104, 3007. (39) Rouillard, M.; Girault, Y.; Decouzon, M.; Azzaro, M. Org. Magn. Reson. 1983, 21, 357. (40) Clarke, H. T.; Read, R. R. Organic Sysnthesis, Collective Vol I, 1941, 514. 101 (41) Clarke, H. T.; Taylor, E. R. Organic Sysnthesis, Collective Vol 2, Blatt, A. H. Ed., 1943, 588. (42) Guilleme, J.; Diz, E.; Bermejo, F.J. Magn. Reson Chem 1985, 23,442. (43) Benzylic hydrogens masked by other signals and were not observed. 102 Appendix 103 4-[(Trimethylsilyl)methyl]benzoic Acid was prepared from ;?-toluic acid as described by Stem and Swenton.-^ All equipment was dried in a vacuimi oven prior to use. To a dry 250 mL 3-necked round-bottomed flask was added 80 mL of dry THF and 12 mL of diisopropylamine (84 mmol). To one neck was added an addition fxmnel, to another a glass stopper, and to the last a rubber septum. The flask and its contents were cooled to -78 °C with an IPA;'CO, bath. Thirty-two milliliters of 2.5 M /i-butyl lithium in hexanes (80 mmol) was placed into the addition funnel. The n-butyl lithium was added dropwise while the solution was being stirred. The dark yellow LDA solution was stored at -78 ^C. To a dry 500-mL round-bottomed flask was added 4.032g of/j-toluic acid (29 mmol). A stirbar and 100 mL of dry THF was added to the flask dien a rubber septum was placed over the mouth. HMPA (11 mL) was added to the flask via a syringe. The flask was cooled to -78 °C with an EPA/'CO, bath. After the flask had cooled for approximately 20 min, a canula was placed between the 500-mL flask and the flask that contained the LDA solution. The LDA solution was slowly transferred. After the LDA solution was added, the reaction mbcture was stirred for 20 min. Freshly distilled chlorotrimethylsilane (8 mL, 60 mmol) was added slowly by syringe. The EPA/CO, bath was removed and the solution was allowed to warm to room temperature. As the solution warmed, it changed from an orange to a light yellow color. The solution was poured into 150 mL of water. The two layers were separated. The water layer was acidified with 6 M HCl and then extracted with 50 mL of ether three times. The combined ether layers was extracted three times with 50 mL of 5% Na,C03. The basic extract was acidified with 6 M HCl and then extracted with three portions of 50 mL of ether. The ether extract was washed with a saturated NaCl solution then dried with anhydrous MgSO^. The ether was removed imder reduced pressures to yield 4.65g of crude product. The product was repeatedly recrystalized from methanol/H,0 to yield l.273g of white product (25% yield; 99% pure by GC). Addition product was recovered from the mother Uquor 'H NMR (400 MHz, CD.CN) 5 9.293 (bs), 7.833 and 7.115 (AA-BB-q, /=8.4Hz), 104 2.207 (s), -0.032 (s); 'H NMR (400 MHz, CDCl.) 5 7.95 and 7.07 (AA'BB'q,y=12Hz, 4H), 2.17 (s,2H),-0.02 (s, 9H); '^C NMR (100 MHz, CD.CN) 5 168.0, 148.4,130.5,129.0, 126.5,28.0, -2.0. 4-[(Trimethylsilyl)methyI]benzyl Alcohol was prepared by lithium aluminum hydride reduction of 4-[(trimethylsilyl)methyl]benzoic acid with a procedure similar to ±e procedure outlined by N'ystrom and Brown--' for the reduction of phenylacetic acid to P-phenylethanol. LAH (150 mg, 4 mmol) was weighed into a 50-niL three-necked flask. About 4 mL of dry ether was added to the dropping funnel. The flask was cooled with an ice bath. The ether was added to the flask. The 4-[(trimethylsilyl)methyl]benzoic acid was weighed into a flask (40lmg, 1.8 mmol) and dissolved in about 8 mL of dry ether. The acid solution was transferred to the dropping funnel. The acidic solution was added dropwise to the LAH mixture. After the addition was complete, the reaction mixtiure was heated to reflux for 15 min. The flask was cooled with an ice-water bath. One milliliter of water was added dropwise to neutralize the remaining LAH. Three milliliters of 10% H,SO^ was added to the reaction mixture. The ether layer was separated, washed with water, and then dried with anhydrous MgSO^. The ether was removed tmder reduced pressure to yield 335mg of the desired alcohol. (1.7 mmol, 94% yield). 'H NMR (400 MHz, CD.CN) 5 7.191 and 7.009 (AA'BB'q, J=7.6H2), 4.507 (s), 3.320 (bs),2.107 (s), 0.001 (s); >H NMR (400 MHz, CDCL) 6 7.20 and 6.97 (AA'BB'q, /=8Hz, 4H), 4.61 (s, 2H), 2.06 (s, 2H), 1.56 (bs, IH), -0.03 (s, 9H).[lit^ 'H NMR (CDCI3) 5 7.22 and 7.00 (ABq, y=8.0Hz, 4H, arom), 4.6 (s, 2H, CHJ, 2.12 (s, 2H, CH,), 0.02 (s, 9H, SiMe,)]; '^C NMR (100 MHz, CD3CN) 5 140.3,138.4, 128.8, 127.8,64.7,26.9, -1.8. Anal. Calcd for C^Hj^OSi: C, 67.98; H, 9.34. Found: C, 68.14; H, 9.47. 4-[(TrimetIiylsiIyl)methyl]benzaldehyde was prepared from 4-[(trimethylsilyl)meth- yl]benzyl alcohol with a procedure similar to the procedure outlined by Corey and Suggs.^^ To a 100-mL rovmd-bottomed flask was added 1.307 g of PCC (6 mmol) and 8 mL of dry 105 CH,CI,. The reaction mixture was place beneath a nitrogen atomosphere. A solution of 0.763 g of 4-[(trimethyIsilyl)methyl]benzyl alcohol (3.93 mmol) in 4 mL of CH,C1, was added to the PCC solution. After the mi.xture was stirred for 2 h, 20 mL of ether was added to the flask. The liquid was removed from the flask. The flask and the solid were rinsed twice with additional ether. The ether solution was filtered through diatomaous earth. The solvent was removed under reduced pressures to yield 0.726 g of an oil (3.76 mmol, 96% yield) 'H NMR (400 MHz, CD3CN) 5 9.889 (s), 7.727 and 7.198 (AA'BB'q, >=8Hz), 2.238 (s), -0.017 (s). •H NMR in CDCl. data are in good accord with published values.^'' '^C NMR (100 MHz, CD.CK) 5 192.9,150.2, 134.1, 130.5, 129.5, 28.4, -2.0. Isophorone Oxime was prepared from isophorone as described by Beringer and Ugelow." To a 250-niL round-bottomed flask was added 30.0 mL of isophone (27.7 g, 0.200 mol), 17.0 g of hydroxylamine hydrochloride (0.24 mol), 17 mL of dry pyridine and 20 ml of methanol. The mixture was stirred until homogeneous and then stirred for 24 h. The reaction solution was then slowly poured into a beaker with approximately 50 mL of water, which was being stirred. .About 50 g of crushed ice was added to die mixture. After the ice had melted, the precipitate was filtered and rinsed with approximately 150 mL of water. The wet solid was dissolved in ether and then placed in a separatory funnel. The water layer was removed and back extracted with additional ether. The ether layers were combined and dried with anhydrous sodium sulfate. The dried ether solution was placed into a 500-mL round-bottomed flask and the edier was remove under reduce pressures. A mixed of the £ and Z isomers of isophone oxime (1.93 : 1) was with a final mass of29.970 g (0.196,98%). 'H N-MR (300 MHz, CDCy 5 6.601 (s, IH), 2.103 (s, 2H), 1.996 (s, 2H) 1.855 (s, 3H), 0.960 (s, 6H). 'H NMR (300 MHz, CDCy 5 5.906 (s, IH), 2.363 (s, 2H), 1.945 (s, 2H) 1.807 (s, 3H), 0.971 (s, 6H). []iv^ >H NMR (300 MHz, CDCU) E isomer 5 5.92, 2.38, 1.94,1.81,0.98; Z isomer 5 6.63,2.09, 1.98, 1.85, 0.97] 3',4',5'-TrimethyIacetanilide was prepared from isophorone oxime as described by 106 Beringer and Ugelow.-' A chilled solution of 29.554 g of isophorone oxime (0.192 mol) in 100 mL of acetic anhydride and 16.1 mL of pyridine (0.20 mol) was prepared in a 500-mL round-bottomed flask. A solution of 14.2 mL of acetyl chloride (0.2 mol) in 10 mL of acetic anhydride was added to the flask and resulted in the formation of a solid. A condenser was added to the flask. A water bath was placed around the flask and the mixture was stirred. The water bath was heated to approximately 65°C and held there until the mixture became homogeneous. The temperature of the water bath was then increased until the water boiled. As the reaction progressed the mixture changed from a light orange to a nearly black. After 1 h at 100°C, the hot water bath was removed and 125 mL of water was slowly added to the reaction mixture though the condenser. The dark reaction mixture was transfered to an Erlenmeyer flask and the round-bottomed flask was rinsed with an additional 50 mL of water, which was added to the Erlenmeyer flask. At this point some crystals were beginning to form. The flask containing the crude product mixture was place in the refrigerator overnight. The cold mixture was then filtered and then recrystalized from methanol to produce 6.679 g of 3',4',5'-trimethylacetanilide (0.038 mol, 20%). Additional product was obtained by extracting the aqueous mother liquor with ether and then removing the ether under reduced pressures. The product obtain from extraction was a sohd suspended in a thick oil. 'H NMR (300 MHz, CDCy 5 7.112 (s, 2H), 2.235 (s, 6H), 2.123 (s, 3H) 2.099 (s, 3H); '-C NMR (75.4 MH2,CDCU) 6 168.2, 137.0, 134.9, 131.2, 119.3,24.4,20.6, 14.9. 3,4,5-TrimethyIaniline was prepared from 3',4',5'-trimethylacetanilide as described by Beringer and Ugelow.^^ A mixture of 6.001 g of 3',4',5'-trimethylacetanilide (0.034 mol) in 10 mL of 20% H,SOj was heated to reflux for 2 h. The mixture was allowed to cool to room temperature and then made basic with sodium hydroxide solution. After the mixed was chilled m an ice bath, it was filtered. The product was recrystalized from hexanes to yield 4.243 g of 3,4,5-trimethyIaniline (0.031 mol, 91 %). 'H NMR (300 MHz, CDCy 5 6.383 (s, 2H), 3.434 (bs), 2.182 (s, 6H) 2.048 (s, 3H); NMR (75.4 MHz, CDCy 5 143.5, 137.3, 107 125.0, 114.7, 20.6, 14.4. [lit- 'H NMR (90 MHz, CDCl.) 5 6.4 (s, 2H), 3.5 (s, 2H), 2.2 (s, 6H) 2.15(s, 3H)]. 3,4,5-TrimethyIbeiizonitrile was prepared by the Sandmeyer reaction from 3,4,5-trimethylamline with a procedure similar to the procedure outlined by Clarke and Read^® for the reaction of o-toluidine to o-toliuiitrile. In a lOO-mL round-bottomed flask, a cuprous cyanide solution was prepared from cuprous chloride (1.75 g, 17.7 mmol), sodium cyanide (2.2 g, 45 mmol), and 12 mL of water. The solution was chilled in an ice-water bath then 10 mL of toluene was added to the flask. While the cuprous cyanide solution was cooling, to another 100-mL round-bottomed flask was added 1.85 g of 3,4,5-trimethylaniline (13.6 mmol), 18 mL of water, and 3.5 mL of concentrated hydrochloric acid. The mixture was chilled in an ice-water bath until its temperattore was below 5°C. A solution of sodium nitrite (960 mg, 13.9 mmol) in 3 mL of water was added slowly over 10 min to the stirred mixture of 3,4.5-trimethyIaniline hydrochloride. The mixture was tested with starch-iodide paper to ensure that enough sodium nitrite was added. Solid carbonate was slowly added to the mixture until neutral with litmus paper. The cold diazonium solution was slowly added to the rapidly stirred cuprous cyanide solution. The mixture was stirred for an additional 30 min while maintaining the temperature below 5°C. The stirring was continued as the mixture was allowed to slowly warm to room temperatures over a period of 5 h. The mixture was warmed with a 50°C-water bath for 20 min. The mixture was allowed to cool to room temperature and then placed into a separatory funnel. The organic layer was separated, washed with water, and then dried with sodium sulfate. The toluene was removed under reduced pressures. The mass of the crude oil product was 1.267 g (8.72 mmol, 66 %). IR (neat) 2930,2210,1610,1560 cm '. 3,4,5-TrimethyIbenzoic Acid was prepared by acid-catalyzed hydrolysis of 3,4,5-trimethylbenzonitrile following a procedure similar to that outlined by Clarke and Taylor^' for the acid-catalyzed hydrolysis of o-tolunitrile acid to o-toluic acid. In a 10-mL 108 round-bottomed flask, equipped with a stir bar and condenser, are placed 1 mL of water and 3 mL of concentrated sulfuric acid. The 75% sulfuric acid solution was heated to 150°C by an oil bath. The oily 3,4,5-trimethylbenzonitrile (1.243 g, 8.56 mmol) from above was slowly added dropwise into the reaction mixture through the condenser. The temperature of the oil bath was raised to 190°C and stirring was continued for 150 min. The oil bath was then removed and the mixture was allowed to cool. The mixture was then poured into a beaker containing ice chips. The crude product was filtered and then dissolved in IM sodium hydroxide solution. The aqueous layer was washed with hexanes and then acidified with dilute hydrochloric acid. The resulting solid was filtered, dried, and recrystallized (methanol-water) to yield 858 mg of 3,4,5-trimethylbenzoic acid (5.23 mmol, 61 %). 'H NMR (400 MHz, CDCI3) 5 7.726 (s, 2H), 2.319 (s, 6H), 2.218 (s, 3H) [lit^' 'H NMR (90 MHz, CDCl.) 5 9.2 (s, IH), 7.6 (s, 2H), 2.33 (s, 6H), 2.25 (s, 3H) ]; '^C NMR (100 MHz, CDCI3) 5 172.6, 142.0. 136.7, 129.2, 126.0, 20.6, 16.0. [Uf^- 'H NMR ( MHz, CDCy 5.] 3,5-Dimethyl-4-((trimethylsilyl)methyl]benzoic Acid was prepared from 3,4,5-trimethylbenzoic acid as described by Stem and Swenton.^ A solution of 3,4,5-trimethylbenzoic acid (330 mg, 2.01 mmol) in 14 mL of dry THF and 0.70 mL of HMPA was prepared in a 50-mL round-bottomed flask then chilled to -78°C in a IPA/CO, bath. :er:-Butyllithium (2.4 mL, 1.7 M in pentane, 4.08 mmol) was slowly added to the reaction mixture and then the mixture was stirred for 2 min. Freshly distilled chlorotrimethylsilane (0.5 mL, 3.94 mmol) was rapidly added. The mixture was allowed to warm to room temperature and then stirred for 2 h. The THF was removed under reduced pressures and then worked up in the same manor as that described above for 4-[(trimethylsilyl)methyl]benzoic acid to yield 284 mg of 3,5-dimethyl-4-[(trimethylsilyl)methyl]benzoic acid (1.2 mmol, 60% yield) 'H NMR (300 MHz, CDCL) 6 7.707 (s, 2H), 2.266 (s, 6H), 2.233 (s, 2H) 0.015 (s, 9H) [lit^ 'H NMR (80 MHz, CDCg 6 7.74 (s, 2H), 2.29 (s, 6H), 2.26 (s, 2H) 0.04 (s, 9H)] CO CO o VO Ul.. I I I I I M I I T I ri I'T r 1" ? [ I I I I |-?T-ni r i rri I I I Tr|- rri I I I I f I rri [ I i |-rpi rr|TT- 11.0 10.0 9.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-1. 'II NMR spcctnim (400 MHz, CD^CN) of 4-|(liiinetliylsilyl)inclliyl|bcnzoic acid. (S: acctonitrilc) o •> o c> o o c:> o r> c> Ci r> i IJ j\ J I. uiO V 0 u> ai o» 0 - - - ay TTT'-^ITTI-I I M I I [ > I I iTr-T-rrp-i n i-rrH P riT] 1 iH n ? 1 r n-|m i-j-ri-T i-pr i-rtTT'n |iti rp' ffri t rji -rr ^•1 i*T 1 pm-r-|-T-r-rfpm rf-ryT'i'i rriTff1 t r n.O 10.0 9.0 8 .0 7.0 6.0 5.0 4.0 3.0 2 .0 1.0 0.0 -1.0 ppm Figure A-2. 'H NMR specliuni (400 MHz, CDCI3) of 4-[(trimcthylsilyl)melhyl]bcnzoic acid. (S: chloroforni) tn c>t tu r'l r- ot f<4 «rt o> ut r>< c.i Ml S - |-_ I -1 • |— -1-7— " 1 i-l- i 220 200 180 160 140 120 100 80 60 40 20 0 piJin Figure A-3. '^C NMR spcctnini (100 MM/., C^D,CN) of 4-[(lrinictliylsilyl)nictliyl]bcnzoic acid. (S; acciuni(rilc) JUl _ J -w- •ititfrr-tti ivri'f f rrri'itr -r-rrttr-| t tt-i i-rrrt j i iff i i it ti~f-i-tri| itr-i-]t rti-ji 11.0 10.0 9,0 8.0 7.0 6.0 5.0 4.0 Figure A-4. 'II NMR spcctrum (400 MHz, CDjCN) of 4-f(lrinicthylsilyl)iucthyllbcnzyl alcohol. (S: acutonilrilc) I I I, n •SI P-' r I'T-rTTj i*i"TrfTrrT^*nn 1 rrrTji ITr ]*r- i ri^ti i-i i it-i i i n'l i f i i rr|-i r I f-T-] rn ix*'' 11.0 10.0 9.0 B.O 7.0 6.0 5.0 4.0 3.0 2.0 1 . 0 0.0 ppm Figure A-5. 'H NMR spectrum (400 MHz, CDClj) of 4-[(trimcthylsilyl)mclliylJbenzyl alcohol. (S: chloroform) •p V *0 •«* o lO vTi ' o) m r- fNj r-> aa r-> rs< r-- • »4 — \ 1/ I mtf u „l_ I _i_- "T~ ' I -1—' 1— I r --l--->—t- T" "1 ~ —1_- ~r~ n '—I 220 200 180 160 140 120 100 BO 60 40 20 0 ppm Figure A-6. '•'C NMR speclrum (100 MHz, CD^CN) of 4-l(trimclhylsilyl)mcthyl]bcnzyl alcohol. (S: acetonitrilc) cu (o rt> (u u» (I) CO (^4 (v< u» ot f'l I o 00 o i*» o» »— v r^4 '• r- o ci a c-t at o> oi ui o* o c* ta o o O i-.i-1 IJ-J u/l li ftti i-prrt-i-j-i-tr rf-n~n-| r 1 pj n-i 1 i i t tr"m * i 11 I-r| I'l ri-j n 11.0 10.0 9.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-7. 'H NMR spectrum (400 MHz, CD,CN) of |/;-((triincthyIsilyl)mctliyl)piicnyl]methyI acetate (13). (S: acetonitrile) a u> r-t u> o (xi u> ^ cl u) ui o> »o r<4 o w> •- r>4 rm V-l 1/ s JU ~r- 1 1 __l _ ~r' ~r" I— 220 200 180 160 140 120 100 80 60 40 20 0 ppin Figure A-8. '^C NMR spcctriini (100 MHz, CD,CN) of f/>((triine(hylsilyl)niethyl)phenyl]methyl acetate (13). (S: acclonitrilc) ppm 20 40 60 t > 80 100 120 p' 140 ' I ' ' I ' I ' I I i i i i i i i i i i I I ' i i i i i i i 7.0 6.0 S.O 4.0 3.0 2.0 ppm Figure A-9. HRTCOR spcctnim (CD,CN) of (/;-((tnnicthylsilyl)nic(liyl)phenyl]mcthyl acetalc (13). ^ (U c» •" r»> ^ r *-• ^ o o» o ^ *0 *• »- t/» co oo r»r»»-o0«®0 wi m •# fn< r«< •— t-» iugo(ou3a3»/tt/>«»«r «* •|' 00 M , JUUL L._ r*rj S Ui lO CJ CJ ai o (D - - • CJ o - -1 J ~I IT^l- j -r rpn-f-f - j-i • rt*i -pr itt p Trrrpn"T ryrrn i ri-T r] 1 i TT-fvm j ri i 1 1 rinrr 1 ' "T '' 1 IT ' 1 r i~ TT-] T"l T |-]-| • 11.0 10.0 9.0 8 0 7.0 6.0 5. 0 4.0 3.0 2.0 1.0 0.0 ppin Figure A-10. 'H NMR spectrum (400 MHz, CD^CN) of/j-xylylcnc (1) in degassed CD,CN. (M: methylene chloridc, S; acelo- nilrile.T; TBAF) ^ it> »f» fu f,t ^ fn ui 0> !•« o xj »•"! v t-* O) lO oj rv. r>- —• o Oi ai ^ V rN* r- on (O CO CO (O ^ V i» t/t ut u» Wi w» t/t M vo lllww ll -r-f fTyi-rT-|-f-r-r-|-?i-r-ft-r}-i'>'i-|-pT I'l i [ i r|-m'>-|-nt-t i*i •|-ri-i t pi t rrpn T'lfT 11,0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-11. Enlargement of Figure A-10 from 12 to -0.7 ppm. 'H NMR spectrum (400 MHz., CD^CN) of/)-xylylcnc (1) in degassed CDjCN. (I: internal standard, naphthalencIVI: methylene chloridc, S: acctonitrilc, T: TBAF) after 19»i0urs inw >#[*<»i|>hrrw w ml VL.i.mnUrik'jf*'i'fyw''i III after 6 hours oto i aftefl 15 minutss *11 BEFORE ADOmON Figure A-12. 'H NMR spcclruni (400 MHz, CD^CN) of reaction progress of/^-xylylene (1) in degassed C'D^CN. (1, 3, 13 and 14 are compound ninnbers given in the text, I: internal standard, naphthalene M: methylene chloride, O: oligomers, T: TBA!') (o iM ui CD lO «r o r>« V — O (7» •- cn (r* II w lo 14 14 fff*''"!"!"!'i~rT|'i I I I j'rr r t'| tti'T]"!-? i i f n-ri"| I pr^»*T~^ ?-rTi~|"i I'l-f j-T-fi f jT I' iT|-i-»-r I'pi I i-i I i-i-n-p ri-i ]' ri 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppni Figure A-13. 'H NMR spectrum (400 MHz, CD^CN) of [2.2]paracyclophaiic (3) and [2.2.2]paracyclophanc (14). (S: acctoni- trilc, W: water) Oi to O ll I i vr v i ^ s lo to r 1 1 _iu l. ~r' '^"i" " t t— ~1" "t"'—I 220 200 180 160 140 120 100 80 GO 40 20 0 ppm Kigiii'C A-14. '^C NMR spectrum (100 MHz, CDjCN) of/j-xylylcne (1) with Cr(acac)j. (S: acelonitrile, T: TBAF) «u • I J J,-U Ir i" r 1 lo OJ 220 200 180 ICO 0 ppm Figure A-I5. Rnlargcmcnt of iMgure A-I4 from 230 to -10 ppm. "C NMR spectrum (100 MHz, CDjCN) of/j-xylylcnc (1) with Cr(acac)j. (S; acctonitrilc, T: TBAF, X; acctatc) 130 120 ppm Figure A-16. Enlargcmcnl of rigurc A-14 from 145 10 ppm. NMR spcctrum (100 MHz, CD,CN) of/;-xyiylcnc (1) with Cr(acac),. (S: iicctonitrile) rN ^ o ^ cr> to k/1 fn €*t m vo t" r>- t- r-^ r» »>• r*. r- f~. t- . i-. »-. f. r- i'. »•« t - i- u* utuiut •t ^4 ^ • • " " ' ^' " " ' I " '"'i '||\'r-Hf' ' ',L-' " 'V r s lo u% |TTrT-pT-n*prrTT j-f ri r-j-m-rrTTrT|n-rrp-n 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 ppm Figure A-17. 'H NMR spectrum (400 MHz, CDjCN) of/>-xylylenc (1) and oligomcrization products in oxygenated CDjCN. (S: acctonitrilc, T: TBAF) o »•» •* «»>•/••<»>/> i/tf t/t '• • * rofNiO«0tO^ r-^ r« o (7t Oi r~ f*- u»oo»/>ioa*«*'»»o — -- cuiotwu^ut'' o> ot (f* oso SQ (O(U to (u f*- r- to tu ^ w> kf> ^ <• • "I "'MM I I I I I 1, '^" " V lo ON V[wyifffvwuma ti1-m-r|"**r? rjt t-n |-n-r-t |-m rpi i-ri~i"n i-r| ri n |-i i 11 j i n*rtt-n"r( ni r |'m i-| i vr?-ff r i* 11.0 10.0 9.0 6.0 b.O 4.0 3.0 2.0 1.0 0.0 -1.0 ppm Figure A-18. Enlargement of Figure A-17 from 11.5 to -1.8 ppm. 'II NMR spectrum (400 MMz, CDjCN) of/^-xylylenc (1) and oligomeri/.ation products in oxygenated CD^CN. (A: oxygen adducts, I: internal standard, naphthalene, IM: methylene chloridc, S: acetonitrile,'I': TBAF) pju» — -- •- •-»• luvuniv ir»«» c««c ir> >1 r ut r- u> u I r-4 •- lit »/) O to ^ »ni o iji f*- ko r> »•* ui oo »/> *0 f^ o ^*» t r^« i •« i>» o> »• u» »/i •• »o i • O • • u» »n u» »o »-i »- •- cn - Oi cr> m oo ir- no to r>> r< ui •«» m ai vn -v »o m '-i »-»»'•»*> rv« r-« <•-« «•< r-« «-« — ^ ^ , i:» o< u» ui <*i to m uj >o «* «* ^ o» €7> oi f" f" r*» f- f- J"' r-v »«. »-• »-v r>. r-" r-. r- I' i- f - i- >•• t- t- i - i- i f- f m • ' i ' ' i ' i i i i i i 1 ' lit.iL!.l.,l " I . . ) . . I I I -jto ^A... L r i i » i m 1 i i i i i i i i i ? i p i » » y i < ' i i i i t-r-]'rtt-t |-r t » ?-i-fi pr»-n~| it t i-| i t n-pr rrrj mn j t n i-prn i-i-rTTi-|-i t-f-ii ri n j ri i i-| itj 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-I9. 'H NMR spcctniin (400 MHz, CDjCN) ofproducts of/J-xylylcnc (1) and oxygen. (S: acclonitrilc, T: TBAF) r- »nr» — — . iu<««mo o>'nr adr-.««i/«r^« a> * r«« »<» «» c» oi »o » - ^ «f» «a t/1 »*» »- c* ^ • ijt ot (9< ad m 'm3 « lo ta %ft t » r••».- » • o i ' ' i lif ' ' ' ' ' r r M A |nJ CX) JJl iihl-^ rr|*T-n~i"j'm'i TmT| i-m"i"ri T m r"| r» i i-pf-f •|-?1-TT n I T-r-| i-|-rf ri^^f ti'tti-tt-i-| t-r f-T-r-f i-|-f TTTi-n* 11.0 10.0 9.0 B.O 7.0 6.0 b.O 4.0 3.0 2.0 1.0 0.0 ppjn Figure A-20. Eiilargemenl of Figure A-19 froiu 12 to -0.7 ppm. '11 NMR spcclruni (400 MHz, CD,CN) of products of/;- xylylene (1) and oxygen. (A: oxygen adducts, I: internal standard, naphthalene, M: methylene chloride, S: acetonitrile, T: TBAF) to oa c:' — u> «u to ^ r • o o> (D oo r~- — oooioor» I Ir' \r I s •'• lo v£> m •| IJju. l. -""srn *n- o c> •fi I I I I I rri'lii j'n-f-rf-i-rrTjTi rTi'i l-pf-I-I T-^-T I'll •] -|Tl TTTT TT pT-TT1-| T Tl » pi l~n n"T~ 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0,0 ppm Figure A-21. 'H NMR spectrum (400 MHz, CD^CN) of/;-xylylcne (1) products in deoxygenated CD,CN. (IM: methylene chlo ride, S: acctonitrilc, T: TBAF) <« !&• ai cj ''t ft u (O r> ui rs« c> c/> t" — r> tneo BOfu *^-m tii 'ut - o c» o> ta«« r^ f^ ui-- ir» to'• «>#ui (-J o o r-^ f . r . f-. r-. »-• f «f-' *•• !•> » « r • r> «> *t* «• ^V-'W 1/-^ r m 14 J— xjw IW 4-1^- r"^ CJ o •- 1 o» o - CJ 0 o 1 o o o o 0 7-T-rn"('ri ri"| I'i'i i ( ' i r > | i t i f jtt i -TT l-r* -T-r^ U-. (. rrV\-r-T •i-|-n 1 1 I . ri I I I I T T I I iiT]- fi- 11.0 10,0 9.0 8.0 1.0 6.0 b.O 2.0 1 . f) 0. D ppm Figure A-22. Hnlargcmcnl of Figure A-21 from 12 to -0.7 ppm. 'II NMR spcctrum (400 MHz. CD^CN) of/;-xylylciic (1) prod ucts in dcoxygcnatcd CD,CN. (3 and 14 are compound numbers given in the text, I: internal standard, naphthalene M: methylene chloride, S: acctonitrile, T: TBAF) m S _JL rrrT|-T~rn -|- ri I I f i-n-rr-n 11.0 10.0 9.0 8.0 7.0 G.O 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-23. 'H NMR spcclruin (400 Mllz, CD^CN) of 4-[(li"imclhylsilyl)inclhyl]beir/.alclchyde. (M: inelliylcne chloride, S: acctonilrilc) . »-• «N • . I'. » o o o o o 1.11.•y M 1 Tixri |'frf-r|"?-n-i l l'ITj I TTI"] i-» I fi "J I mT j-r-» -i-| t-i t f-jn i-rrpn^? I t TT-rim ri i-m-T-|-rri rj 1 i 11 | r r ri t(l-t 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4 . 0 3.0 2.0 1.0 0.(1 -1.0 ppm Figure A-24. 'H NMR spcctruni (400 MH/., CDCl,) or4-[(lrimelhylsilyl)methyl]bcnzaIcieliyclc. {K: ethyl cllicr, IM; methylene chloridc, S; acetonitrilc) V r>< CTt CO at OJuj llfWllHM ni^ii r T '-| -- ~t" ^i~ I—T—1 220 200 3 BO 160 140 120 100 80 60 40 20 0 ppm Figure A-25. '^C NMR spectrum (100 MHz, C'D^CN) of 4-|(lnmetliylsilyl)iiiethylJbcnzalclcliydc. (S: acctonitrilc) «o ir» o r- a» U- t- lO *# »•» r- O u< '-,1. 1 N yp' OJ 4^ _ Jl_. A':. J »yi I 1 I |"rT-rT]~ri I I pfn l"( i m ri rn~p in iflTi n.o 10.0 9.0 B.O 7.0 6.0 0.0 ppm re A-26. 'H NMR spcctrum (400 Mllz, C1),CN) of l-[/;-((tiiincthylsilyl)n)ethyl)plicnyl]cllianol. (E: clhyl clhcr, S: acclo- nitrilc) to rn c« •* • o» r-. a» t"! a% ra • cj a f>« u) to tn • ci M k -i—• —r- T-T—I—I—.—f- "i 220 200 180 160 140 120 100 80 60 40 20 0 ppm Figure A-27. '^C NMR spcclrum (100 MHz, CDjCN) of l-[/;-((triniclhylsilyl)niethyl)plicnyl]cthanol. (E: ethyl ether, S: acetoni- Irile) «/> cf m o> a> rv. (U - >/ I (U r-4 o t/> — a) u a* tocnoi/i— OK> *» r- co o o cri CD — o oi o» o> r-- i/) r*! ci to v et> m fi m u> m •— fO - •- Ct> O O* tn »•- I- t- to to u> u> u» M> to o 0« 1-1 4jI. LU OJ On .l I 1,- i-r'^rrryi-m-i" m-r |-n n") i i n |~|-T r"1. 1.1 ii-i-j-i r 11.0 10 . 0 b.O 4.0 3.0 2.0 1.0 0.0 ppm Figure A-28. 'II NMR spcctruni (400 MHz, CD,CN) of l-l/.»-((trinjclhylsilyl)mcthyl)phcnyIJcthyl acetate (15). (F: 'I MF, IVI; methylene cliloi idc, S: acelonilrilc) m «M (o i(t to 1"^ fO ir i|l iw —1—t—1- I -1—r—r- r—'—r —r 1' -i— —1 r—I- t— T" '- -T r—, . —, 220 200 leo 160 140 120 100 80 60 40 :!0 0 ppm Figure A-29. '^C NMR specliiim (100 MHz, CD,CN) of l-|/>-((trimclhylsilyl)niethyl)plienyl]cthyl acctatc (15). (F; THl acetonitiilc) ui Kf» Ot • - ^ lO ttJ oi ^ *0 o -• ^ «r. oi to rx a> f t oi I o< u Oi o ot o •- «o • cd cn m iu C4i o lo 40 fn uj f>. r-. ^ u» oi m r- I'* r~ r • lO r«* r»4 O CI »r» »/> ui — r»lo * rv« ^ o oi «n ^ •- i/> u> ui U3 IX) tn r- f*- n m »n ui ivi «o <0 ir» ^ ^ cNt r«i r>« r-^ «# «• m ^ r-> Ut iO K* U> UJ «£• tO tr> ^ *^4 0< Ol (F) o» Ot o> V ^ ui co «o f-. r<- r-« t • t •• t' r> i-- r* f*- f* **• i - **' •!>«(# tn «o u* ui iO *r «/ «# V 1 I MJL ' " m.' iiuiiai,^; ^ y 1 m ' i ' • j OJ CO M UI [ trn'j-rn'i-|-r rrff m i-i'm it-| tm ji-r r rrr|"i it t-itt-i-t-|-i-i-rTTi ittti i i ! i t-iiti rr|-n-|'i | i i i-i |n-r-rci-t" 11.0 10.0 9.0 5,0 4.0 3.0 2.0 1,0 0.0 ppm Figure A-30. 'II NMR spcclmm (400 MHz, CD,CN) of a-mcthyl-/J-xylylenc (11) in degassed CD,CN. (IM: methylene chlo ride, S: acelonilrile, T: TBAF) »/•» »n o« . - • n» ^ Ci ^ r- «*• »'n >« «• c»> cj u> o o> <-3 r- uj »/> -• cj r (rt «} r-~ »— Ct iJ> CO r~~ cn ii> iv o cj to •#"> u i — •%» •- CD o> on •«» • ko ko tX) to ui "till l,iwy.i,ln>l^k| r OJ vo Ji . —J VI ^ 1. o» (U 0 o< c» ** 0 0 ai .4 T"r-r7T-nrrj-i T ri-rrTTT|-ri*?i-] TT rp -m I t pi r-rj -rti I I I ri'l I i"i i-|-|-fTrr |TT"i I I t I T *~l-rT"i t , i i i i | r m"| i ["i i 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 10 0.0 ppm Figure A-31. Knlargenient oflMgurc A-30 Irom 12 lo -0.7 ppm. '11 NMR spcclriim (400 MHz, C:D,C:N) or(x-mclhyl-/;-xylylcnc (II) ill degassed CDjCN. (I: internal slaiidard, naphthalene, M; methylene chloride, O: oligomers, S: acetoni- trilc,T: TBAF) •fl ««* (fl «- • H «• u) cn o> ^ <7l to f-' (-N — o 0» eo CO CO a> CO v/\ r- f- r* r- r **i tu yti to »0 »C> M* »<« vO i-l ii l-l l l-h-' pr^-' II II II () JUmWW^^ 7.9 7.4 6.9 6.4 ppm Figure A-32. Enlargement of Figure A-3() from 8-6 ppm. 'H NMR spcctrum (400 MHz, CDjCN) of (x-mctiiyl-/j-xylylene (11) in degassed CD^CN. (I: interna! standard, naphthalene, O: oligomers) m II 5.9 5.4 ppm Figure A-33, Hnlargcnient ofFiguie A-3() from 6 4 ppm. 'II NMR spcclriim (400 MHz, CDjCN) of(j(-mcthyl-/>-xylylcnc (11) iiulcgasscci CDjCN. (IM: methylene chloride) i— I "~r~ I ~r~ 3.0 2.5 2.0 1.5 1.0 0.5 0.0 ppm Figure A-34. Enlargement of Figure A-30 from 4 to -0.5 ppm. 'H NMR spcctrum (400 MH/, CD,CN) of (t-mcthyl-/)-xylylcnc (11) in degassed CDjCN. (S: acctonitrile, I": I'BAF) ini 1 r •i r I I After 23 Hours JLIUL l,, lju. JJ JL uv t r I I After 5.5 Hours r JL-hLAl. j l jljl jla,ci, joy lil 1 I After 1.5 Hours •a. JLjLjil. .xju/v. h II r I 1 11 llll 11 After 10 Minutes y\i ju 4, JtlliL-ju lil 15 15 r 15 15 15 I I Before Addition jj. ju jjL JL riT I I I t »"i"|"i"n~r |'i i ii]"! it ? ri-fi i ri i| i fi |i i i i i| i i « i| r i i i i |-i i i i 11 i-i-frpT r i i 11 r 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 .0 1.0 0.0 jipin Figure A-35. 'H NMR spectrum (400 MHz, CD,CN) of reaction progress of (x-methyl-/j-xylylene (11) in degassed CD^CN. (15 is a compound number given in the text, I: internal standard, naphthalene M: methylene chloride, S; acclonitrile, T: TBAl') M o After 23 Hours After 5.5 Hours _jlli J ^—•—ijw*^ After 1.5 Hours i 11 11 11 After 10 Minutes _jl_jlj urjmww-i jl iiKtf 15 15 15 i h Before Addition T—' - ' ' -t—|— - i --|"" i » i —i t -J - I —1 - I I I " ' ' ' • I ' 7.0 6.0 5.0 ppm Figure A-36. Enlargement of Figure A-35 from 8- 4 ppm. 'H NMR spectrum (400 MHz, CD^CN) of reaction progress of (x-methyl-/>xylylene (11) in degassed CD^CN. (15 is a compound number given in the text, 1: internal standard, naphthalene M: methylene chloride, O; oligomers) r-^ r>« ^ ro •— o v r) f.'> •#) «« •- «»»f •» «#> r-^ r-^ «o un «- ».j ai a*»'» *i> *i» «-> •*» mj »•» «o •— «* «n tr» o» i«» •» i »n »- m i.j «< i m »»« i- »- •- » > *i» «o »i > •* •— «t» nr» fo» v »•» .- ra • - »'i <>» •- • lj «!•"* o< in o o w .J ki '1 ? ri'|-|Tn ^ t i i ) | •prn-r"|m "i r |"i i i 1 | i it' Til I'I I IT I |T I I I ^ I I I I I I I I I I'l I I I I I I I ^ n I I J IT'I lT'1*rTlTTT-|TTT I | I I I H.O 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-37. 'H NMR spectrum (400 MHz, CD^CN) of pcntanc extraction of product mixture of (x-mcthyl-/J-xyiylcnc (11) deoxygenated CDjCN. (P: pcntanc, S: acctonitrilc, W: water) »n M »*> 'O ri ut ^ M V tu o at u< t/i • » ' »>* r * f < ^ »'» •- o M o o Ml •« • m »- •« i •« i - i*j t-. r . »-« r. r- r- »•« r- r- I— u» •<» to •£»«<» m »*»»<• •o a> w» Ui •<> ui *A »/>•/>»/> uw» KW» "4 i *• v "• «• } tu ut u3 tu lo >a .» t4> •£» «u u> tu »4i ta » to X) «0 at iO U> M> to >0 tU Ui »- r- »•« I II I I I I I SH 16 Figure A-38. Bnlaigement of Figure A-37 from 7.5 6.0 ppm. 'H NMR spcclrum (400 Mil/., CD,CN) of pcnlanc extraction of product mixture of a-metiiyl'/j-xylylcne (11) in deoxygenated CD^CIN. (16 and 17 are compound numbers given in the text, O: oligomers) t tu V oi t I » r- r- »r» • • •- o »:* cj o» »- •/» i •» »•» «*» i j nn u» iA f I c» vT III J""- »•« a» i« «o »o »- u» '•> ^ v >0 r-i »n • • a) •* r< w 16 or 17 16 01 17 -ju a. • "'~i T-p' I ' I ' I ' I ' I ' I •'• I ' r t-|-i-| 1 I -111 , 1 ] 1-1 1 I I I I I 1- |-i |-1 I . I 1 I" • (1 I . |-r-i • I I I ' 1' r' I ' I ' I ' I ' I ' I ' 3.8 3,6 3.4 3.2 3.0 2.B 2.6 2.4 2.2 2.0 l.« 1.6 1.4 1.2 1.0 0.6 0.6 0.4 0.2 ppm Figure A-39. Enlargement of Figure A-37 from 4 () ppm. 'H NMR spectrum (400 MHz, CDjCN) of pc ntane extraction of product mixture of a-methyl-/)-xylylene (11) in deoxygenatcd CD,CN. (16 and 17 are compound numbers given in Ihe text, I*: pcntane, S: acctonitrilc, W; water) *•1 - t Ut Ut Ut I »• to oat ^io o 'O cn c7i (O oo Wll/ p 4^ 00 0.S ppm Figure A-40. 'H NMR speclruni (300 MHz, CDCI3) isophoronc oxinie. (K: E isomer, S: chloroform, Z: Z isomer) < > «• I r - •»» . <*» ' LLLLi A I -I J vo4^ S „ , ..jJI/Ll L._.. "j'l n I I I I I T [ I ri*T"|'r-»-i I I I I I I I I I t I I I I I I I I I I I f r in I I I I I I I rf-r| I I i I I I I T I I I I I I I I 1 [ I I I • I I I I I I I ri I r t I I I I r 11.0 10,0 3.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 1,0 ppin Figure A-41. 'H NMR spcctnim (300 MM/., C'DCll^) of.!',4',S'-trimctliylacclaiiilidc. (S; chloroform) 220 200 lao 160 140 120 100 80 60 40 20 0 -20 ppm Figure A-42. '^C NMR spectrum (75.4 MHz, CIDCI3) of 3',4',5'-triincthylacclaiiilidc. (S: cliloiofonn) mlsii SO: liU "wjo iwiu mt WAVfNUMBiP IC.M ') vi^avenumb^x (cm 'i Figure A-43. Infrared spectrum of 3',4',5'-trimelhylacctanilidc. 14 13 12 It 10 9 8 7 6 5 4 3 2 1 -0 ppm >22 61 Figure A-44. 'H NMR spectrum (300 MHz, of 3,4,5-(riniethylaiiilinc. (S: chloroform) ui UJ 11 .-I., I. I 220 200 180 160 140 120 100 00 60 10 20 -20 ppm Figure A-45. '^C NMR spectrum (75.4 MM/,, CIX:i3) or3,4.5-trimctliyIaniline. (S: chloroform) MICKONS 60 ' ' ' ' ' • I t I • I t I 3000 V.'AVtNUMBcFICM'l WAVfNUMBEHICW.'l Figure A-46. Infrared speclruni of 3,4,5-trimclhyhinilinc. r 3500 3000 2500 2000 1500 1000 500 Wavenumbers Figure A-47. Infrai ed spectrum of 3,4,5-trimcthylbcn/onitrile. u> r-. OQ (N m cu cn pn oo rs oo ^ oi ro oj uj »- o ^ r^- r'l r-^ u> •«r 'O 'n rs r-^ r-^. f>. hv »o »o f>j «N IP Vr' U\ ON E ljoL ju [-rT t I I I I I I I 1 I I I I I I I I I I'l ' I'l I I I I I ' ' I ' I ' ' ' ' I ' ' ' ' I ' ' * ' I ' ' ' ' I ' ' ' 'friTTfTTTTJTT tf 1-l-r I I I I I I I I I I I I I 11 .0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1. 0 0.0 Figure A-48. M l NMR spectrum (400 MHz, CDC!!,) of 3,4,5-trimctliyllieiizoic acid. (K: etliyl ctlier, S; cliloroform) lO *<» ' »<» u") OJ CNI "J CO (O ^ OO Jt »n o f- tD C7) i7> ^ r>< i a -1 ^ 1 1 1 1 1 1 r—I 1 1 1 1 1 1 1 1 1 1 1 p—1 1 ' [—1 1 r—I I I 1 I I I I 1 I— T I 1 1 1 I I I I 220 200 180 160 140 120 100 iiO &0 40 20 0 ppm Figure A-49. '^C NMR spcclruni (lOO MH/, CDjCN) or3,4,5-triniclliylbcn/.oic acid. (S; chloroform) Oa U> Il » 1/1 V Mt I* I r > nt I' 4 — tr> C« Ci U2 o o •'» « •< « I I I 'VW 1/^' Oi CO A jl . 1 •|-T ri I I m rp r» i | i ri r| i I pi I I I I I I ri I" I I I I I t I I I I I I I I I I I I 1 I I I I I I I I I I I I t I j-i r » I > 11111 11 I I I 11 11 I I 1*1 I I II )"I I 11 n .0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1 .0 0.0 -1.0 ppiii Figure A-50. 'H NMR spectrum (300 MH/., CI^Cl^) of 3,5-dimethyl-4-|(liimethylsilyl)melhyl]benzoic acid. (S; clilorofomi) fn uj » ««* •• I I • «r I *1 (c« t»« i7i t-~ Ui "t •I ••»••» « J I -*««•< •- ... <> t J c> «J O «*> O <••* fa I k| i ..| m,;| i . l/i o K J I .. .L I 1 » ri 'i 1 11 I pi I I I pi t rt f I I I I I ri I I I I I I t I I I I t I t I I r rT"i"pi I I 1 pi I I I j I • • I I I • < n" > It IJ1111 ii«11 111 rr [ I l-» I ] 11 t I I t < < ' I < I I 1 I I 1 pI I ri I IT 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 ppin Figure A-51. 'H NMR spectnmi (300 MHz. CDCI3) or3.5-dimclhyl-4-|(liimclhylsilyl)inclliyl!bcnzyl alcohol. (E: cUiyl clhcr, S: chloioforni) 0> O IN 0« I ^ CO IN cn r*) oo rn too i>4 «•> •- o o o CT) a> o) Of o* Ci o CN fN rN 1/ o\ o s l_. I I I I I I' I t I [ I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I I r I I I I I I I I I I I I I 1-1 I I I I I I I rrr-| I i i i ] i 11.0 10.0 9.0 8.0 V.O 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppin Figure A-52. 'H NMR spcclrum (400 MH/, CD^CN) or[3,5-dimcthyl-4-((trimcthylsilyl)mclhyl)phcnyl]niethyl acetate (19). (S: acctonitrilc) ON 1 1 1 r~-| 1 1 1 1 r—I 1'—I 1 1 i 1 1 1 1 1 1 r —1—»—i—•—r- -i—i— 1—«—r »"r" -f—-t—I 220 200 160 160 140 120 100 60 60 40 20 0 ppm Figure A-53. '^C NMR spectrum (100 MHz, CD,CN) of [3,5-climcthyl-4-((trimelhyIsilyl)mcthyl)phenyl]nicthyl acetate (19), (S: acetonitrilc) m I IT 19 I 1 19 Before Addition 12 12 12 12 After 10 Minutes r JUL u. J UjJ vjv After 20 Minutes r I I . I 11 J Li ill After 85 Minutes r 1 I . I JUL J After 155 Minutes r JU JUL J U After 205 Minutes U J) r J JUL ul 21 20 After 4 Days Jm - I ..|)1 fj r TTT-T i-pT-* I"! ri 1 IJ ririi TT rt | f ii ri m i-j-i i i i | i i i i | r ri i i ? i i i | i i | i i i i j i irr[ i n i | r i i i j r-ri i*] i i i i |-i i v i-)Tr ri) i in j rn 11.0 10.0 9,0 B.O 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-54. 'H NMR spectrum (400 MHz, CD^CN) of rciiction progress of 2,6-dimethyl- />-xylylcne (12) in degassed CD^CN. (19,20,21 , and 22a are compound numbers given in the text, 1: inlernal standard, naphthalene, M: methylene chloride, S: acctonitrile, T: TBAF) !•> m 19 Before Addition JL_JL i u 12 12 12 After 10 Minutes 11 i V \Nvwri After 20 Minutes JLi After 85 Minutes JUL 1 i 1 After 155 Minutes 1_L After 205 Minutes JUL •m»A^ JUl 21 I 20 After 4 Days wimvytyniw' r —I" r »" * I —• -1 f * 8.0 7.0 6.0 5.0 PPiTi Figure A-55. Enlargement of Figure A-54 from 9 4 ppm. 'U NMR spcctrum (400 MHz, CD^CN) of reaction progress of 2,6-dimethyl-/;-xylylene (12) in degassed CD^CN. (19, 20, 21, and 22a are compound numbers given in the text, I; internal standard, naphthalene, M: methylene chloride) Before Addition Afler 10 Minnies I .->^aaaia Afler 20 Minutes After 85 Minutes - -v . After 155 Minutes - After 205 Minutes AI., L\9 1 After 4 Days n ^ I" —, - 3.9 3.4 2.9 J.4 1,9 1.4 ppin Figure A-S6. Enlargcmcnl of Figure A-54 from 4-1 ppin. *H NMR spcclniin (400 MHz, CD^CN) of reaction progress ol' 2,6-dimelhyl-/;-xylylcnc (12) in degassed CD^CN. (19, 20, and 21 are compound numbers given in ihe lexl, S: acclonitrile, T: TBAP) 21 20 22ii 22a 22i» OS Ui 6 . V . b l>rjif» Figure A-57. Enlargement of Figure A-54 from 6.75 6 ppm (After 4 Days only). 'H NMR spectrinii (400 MHji, CD^CN) of reaction progress of 2,6-dimetliyl-/j-xyiylcne (12) in degassed CD,C!N. (20, 21, and 22a arc compound numbers given in the text) :i . o es &- q , o o Q . O e: 4- T . O e -4^ 20 S . O ei -4- 21 €5 . OiS'?!^ -4 . O 3 . O e -4^ i2 00 10m « m < k « H o 10 10 5 1 CO s o«" 22a m A N N 1 n N m n N o S) ,1 I 1 .oe^ JlU i- _JLEI— 2III) P 11 1. 1, i, 1 O S CD 3 O 4 O Figure A-58 GC chromalogram of the penlane extraction of product mixture ol'2,6-dimcthyl- /j-xylylene (12) in degassed CDjCN. (20, 21, and 22a> arc compound numbers given in the text, I: internal standard, naphthalene) r-* r* I ftxft *Kt CJ >00 o< ^ r-« t/t i'^« o ^ > ««a r-« «« ('<4 0< U> U) U3 tt) U3 • *- o o u< M) rv •*« rs< »*< c>< I i-i-U. w 21 o> 20 20 21 20 21 21 I I mImImnJ IIaJ « I (iu>m i-i 1 t I I t rr-|Ti I rprr rf-| r-i-| T I I I I I I I" |-T I I I I I J r-l'l I f I I 'I I f I 11 I f I 11 I I' I r I I I I I I I I I ry-T-i I I I I I I I I I ri 11.0 10.0 9.0 8.0 7.0 6.0 <1.0 3.0 2.0 1.0 0.0 ppm Figure A-59. 'H NMR spectrum (400 MHz, CID^CN) orpcntanc extraction of product mixture of 2,6-dimcthyl-/>xylylene (12) in degassed CD^CN. (20 and 21 are compound numbers given in the text, I: internal standard, naplithalcne, P: pcntanc, S: acetonitrile, W: water) cr> •o «7> Figure A-60. Enlargement of Figure A-59 from 4 0 ppm. 'H NMR spectrum (400 MHz, CD,CN) of pentane extraction of product mixture of 2,6-dimethyl-/J-xylylenc (12) in degassed CDjCN. (20 and 21 arc compound numbers given in the text, P: pentane, S: acctonilriie, W: water) Before Addition After 10 Minutes After 20 Minutes After 40 Minutes After 165 Minutes After 270 Minutes After 24 Hours -+-n~T-j ri I i-jT i , I r ?-* i-t-t ? ] ri rr| i-i-n i-i-rf-Ti-i 11,0 10.0 9.0 fl.O 7.0 6.0 b.O 4.0 3.0 2.0 1.0 0.0 ppin Figure A-61. 'H NMR spectrum (400 MHz, CD^CN) of reaction progress of/j-xylylene (1) and 2,6-diniethyl-/^-xylylcne (12) in degassed CDjCN. (13 and 19 are compound numbers given in the text, I; internal standard, naphthalene, IM: methylene chloride, S: acetonitrile, T: TBAI-') 19 13 1«) 13 13 im Before Addition LJULl) 1 12 12, 12 After 10 Minutes i_JL JUUL After 20 Minutes JLJl J wl—.j i -JLJL iJii After 40 Minutes JLJL jn- jJLu. After 165 Minutes l JLJ. ' i' • • ii" ^ < ' j—jlu, After 270 Minutes| JLJl J 0. jlwjn l J L jll 3 21 20 23 23 After 24 Hours JUl J U_ iu^iul •r—• 1 » 1—"!"• - I - r 1 .1 I I u.o 7.0 6.0 6.0 ppm Figure A-62. IZnlargcment of I-'igure A-61 from 9-4 ppm. 'II NMR spectrum (400 MM/., CD^CN) of reaction progress of/j- xylylene (1) and 2,6-dimcthyl- /j-xylylene (12) in degassed CD,CN. (3, 13, 19, 20, 21, and 23 arc compound numbers given in the text, I: internal standard, naphthalene, M; methylene chloride) > Ut tit W> 1-4 • L'> o* (1 < UJ «.l O (11 (- ' ' ' ' I ' ' ' ' ' I ' ' I I I I I I I Mill M, "•"i* "i "ni tfnrw 11 ^ 3 21 I 1 23 20 23 M •» I I r I » rri |r» » i j n rr] i i i i j » 11»11 11.0 10.0 9.0 8.0 7.0 6.0 S.O 4.0 3.0 2.0 l.d 0.0 ppin Figure A-63. 'H NMR speclrum (400 MH/., CDjCN) of pcntane extraction of product mixture of/;-xylylcne (1) and 2,6-dim- ethyl-/>xylylene (12) in degassed CDjCN. (3, 20, 21,and 23 are compound numbers given in (he text, I: internal standard, naphthalene, P: pcntane, S: acctonitrilc, W: water) 172 CHAPTER 4. EFFECTS OF a-PHENYL AND a-METHYL SUBSTITUTION ON THE STABILITY OFp-XYLYLENES Written in the style suitable for publication in the professional journals published by the American Chemical Society Steven P. Lorimor and Walter S. Trahanovsky Abstract Four reactive /?-quinodimethanes (/7-QDM's),p-xylylene (1), a-methyl-p-xylylene (4), a-phenyl-/?-xyIylene (8), and a,a-diphenyl-p-xylylene (6), were prepared as dilute solutions by fluoride induced elimination. These p-QDM's are stable enough in solution to be observed by 'H NMR spectroscopy at room temperature. For the first time, 'H NMR spectra ofp-QDM's 6 and 8 were observed. All four /j-QDM's were found to form dimers and insoluble oligomers. Rate constants were determined for their decomposition in order to approximate their relative stabilities. In most of the kinetic smdies, both first- and second-order decompositions were occurring resulting from polymerization and dimerization, respectively. /7-QDM 4 was found to be less reactive than the parent p-QDM 1. p-QDM 6 was found to be the most reactive in the series followed by p-QDM 8. Introduction p-Xylylene (1), the parent benzene-based p-quinodimethane O-QDM)', is a reactive molecule that was first proposed as an intermediate in the pyrolysis of/>-xylene (2) that yielded poly-p-xylylene (3)." Polymers fromp-QDM 1 and other substitutedp-QDM's are 173 I 1000 °c ! 'm-, *" [I commercially useful as protective coatings/ Recently our research group prepared p-xylylene (1), a-methyl-;7-xylylene (4), and 2,5-dimethyl-p-xylylene (5) as dilute solutions by fluoride induced elimination of trimethylsilyl acetate/ Trimers ofp-QDM's 1, 4, and 5 4 5 were observed which is strong evidence that they dimerize and oligomerize via a dimeric diradical intermediate. Although the trimer is good evidence of the existence of the dimeric diradical, no direct evidence was observed in the 'H >rMR spectrum. In an attempt to obtain direct evidence of diradical intermediates, a,a-diphenyl-/7-xylylene (6) was prepared. The stability of the dimeric diradical in the oligomerization of/?-QDM 6 was expected to be similar to that of the trityl radical 7.^ The initial experimental work found no evidence of a stable dimeric diradical intermediate but did find a substantial increased reactivity of p-QDM 6 compared to p-QDM 1. When a-phenyl-/j-xylylene (8) was prepared, it also appeared to be more reactive than /7-QDM 1 but less reactive than/7-QDM 6. These results are contrary to the decreased reactivity of a-methyl-p-xylylene (4) when compared to the parent/>-QDM l."* 174 ph^ph /ph Based on previous product studies, the two major reactions that consume the p- QDM's are polymerization and dimerization. Errede^ reported that solutions ofp-QDM 1 at -78 °C polymerize by an apparent first-order process. IVL* - —• '= • ^CH, —^ ^ Trahanovsky and Macias' reported that o-xylylene dimerizes by a second-order process via a proposed stepwise mechanism involving a diradical intermediate. This dimerization is similar to the p-QDM dimerization. It can be expected that in the para- reaction the formation of dimeric diradical would also occur by a second-order process. Given the complex nature of the oligomerization reactions of ;7-QDM's, a feasible means of comparing their overall reactivity would be to compare their estimated second-order rate constants. In order to study the relationship between a-substituents and stability, the rate constants for the decomposition of /T-QDM'S 1,4, 6, and 8 at 20 °C were determined. The rate constants presented in this paper are approximations and are intended to be a means of estimating the relative reactivity of the four p-xylylenes. 175 "~0~ 10 j Results p-Xylylene (1) Long-term Kinetics Studies. /7-XylyIene (1) was prepared as a dilute solution by the fluoride induced elimination of trimethylsilyl acetate from [p-((trimethyl- silyl)methyl)phenyl]methyl acetate (9) and analyzed by 'H NMR spectroscopy (Figure 1). ^oac TBAF. CD3CN Room Tempefature tms' By comparison with naphthalene's peak integration, an internal standard, and the /^•xyiylene's (1) peak integration, the concentration ofp-QDM 1 was calculated for each NMR spectrum taken over time. The resuhs are presented in Table A-1. Attempts to obtain either a first-order rate constant, by plotting the natural log of the concentration verses time. 176 57ttat 13 (5.^11)198001 " t 1 izodi i (IQmia) I i IScferc rtultfob Figure 1. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for long-term kinetics experiment of/7-xylylene (1) in deoxygenated CD.CN. (9, 10, and 11 are compound numbers given in the text, I: internal standard, naphthalene, M: methylene chloride) or second-order rate constants, by plotting the inverse concentration verses time, are shown in Figures 2 and 3. The 'H NMR spectrum of the oligimerization products are consistent with [2.2]paracyclophane,^ dimer 10, and [2.2.2]paracyclophane,^ trimer 11. Consistent with the observations made earlier, the NMR tube contained precipitate. 177 p -Xylylene y s .7E-05X - 6 9332 R- s 0 333 2qqq0 30000 40000 Time (Seconds) Figure 2. Plot of ln[l] vs time for long-term kinetics experiment. p -Xylylene 45000 40000 yOSSSSx* 480.82 R- s 0.9998 35000 w 30000 C 25000 C c 20000 oo «o o s toooo 5000 0 10000 20000 30000 4QOOO soooo Time (Seconds) Figure 3. Plot of [I]-' vs time for long-term kinetics experiment. 178 Insoluble I /'=\ oligomers 1 10 11 a-MethyU/j-xylylene (4) Long-term Kinetics Studies. a-Methyl-p-xylylene (4) was prepared as a dilute solution by the fluoride induced elimination of trimethylsilylacetate from l-[/7-((trimethylsiIyl)methyl)phenyl]ethyI acetate (12) and analyzed by 'H N\IR ,! •• O TBAF, CDjCN I Room Temperature ^tms 12 4 spectroscopy (Figure 4). The concentration ofp-QDM 4 was calculated using the internal standard naphthalene and the results are presented in Table A-2. First- and second-order kinetic plots were prepared (Figures 5 and 6). The oligomerization products observed in the 'H NMR spectrum are consistent with cyclic dimers 13 and trimers 14 observed in product studies. fC R, 13a. R,= Me. R2 = H 14a. R,=R3= Me. R2=R» = H 13b. R,= H, Rj = Me 14b.Ri=R3=H.R2=R. =Me 179 M • ' 0 m't!' u 1 .O-'-LA _ . I t "»«• lA. jii 1. ... .1 . i ISJD) • — 1 • 1 1 • ' -.1 (Uk) . 4 ( 1 1 •1 i ^*1 Jl I* M V 1 . • ' ' 1 1 1 1 M 1 iddiiMM '' 1 1 1 1 " Wl 1 6•C S . 9 ppn Figure 4. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for long-term kinetics experiment of a-methyl-p-xylylene (4) in deoxygenated CD.CN. (12 is a compound number given in the text. A: oxygen adducts, I; internal standard, naphthalene, M: methylene chloride, O: oligomers) 180 a-Methyl-p -xylylene oC (q oC cu oo c •0 OOOtx • 6 6114 R-s 0 9891 0 SOOO toooo 1S000 :oooo Time (Seconds) Figure 5. Plot of In [4] vs time for long-term kinetics experiment. a-Methyl-p -xylylene / a 0 2777X • 485 86 R- * 0,9873 toooo 1S0Q0 Time (Seconds) Figure 6. Plot of [4]*' vs time for long-term kinetics experiment. 181 ;7-XyIyIene (1) Short-term Kinetics Studies. p-Xylylene (1) was prepared the same way as above and analyzed by 'H NMR spectroscopy (Figure 7). Using the same means of comparison of the naphthalene standard peaks to the /7-xylylene peaks in the 'H NMR spectra, the concentration ofp-QDM 1 was calculated. The results are presented in Table A-3. First- and second-order kinetic plots were prepared (Figures 8 and 9), i i i i 'viwamiii nywiwiiii* wn»iinw»« I » ' . . , . , » 1 • ' • • I ' 3.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 Figure 7. 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for short-term kinetics experiment ofp-xylylene (1) in degassed CD.CN. (I: internal standard, naphthalene) 182 p-Xylylene Co c o0 y = -0 0002*. 5 8493 R- s 0 3252 1000 1500 Time (Seconds) Figure 8. Plot of In [1] vs time for short-term kinetics experiment. p -Xylylene 520 0 W32x •343 76 R? s 0 542 1500 20G0 2SQ0 Time (Seconds) Figure 9. Plot of [1]-' vs time for short-term kinetics experiment. 183 Within the time span of this kinetic experiment only traces of dimer were formed. After standing overnight, the reaction mixture showed NMR peaks for both dimer 10 and trimer 11 contained a precipitate. Generation and Oligomerization of a-PhenyI-/>-xylylene (8). (4-[(Trimethyl- silyi)methyljphenyl)phenyimethyl acetatc (1^) was prepared from •4—[(tnmethylsilyl)mcth- yl]benzaldehyde (16) as shown in Scheme 1. a-Phenyl-/?-xylyIene (8) was prepared as a Scheme 1 o^h ho^ph aco^ph ^ , AcCI • PhMgBr ^ Pyridine ^ I I tms"^ tms^ ^tms 16 17 15 dilute solution by the fluoride induced elimination of trimethylsilylacetate from (4-[(trimethyIsilyl)methyl]phenyl)phenyhnethyI acetate (15). The 'H NMR spectra are aco^ph ^ph ' 1 TBAF. CD3CN Room Temperature i I "^tms 15 8 presented in Figure 10. Using the same means of comparison of the naphthalene standard peaks to p-QDM 8 peaks in the 'H NMR spectra, the concentration ofp-QDM 8 was calculated and the results are presented in Table A-4. First- and second-order kinetic plots were prepared (Figures 11 and 12). a-Phenyl-j3-xylyIene (8) was prepared on a larger scale with non-deuterated solvents. 184 4891 t kjm 4221s 3751 1 J>n/mM^ 3301 k^wpw :45if :46i % 1741 » pwewo 1411* 1141 f 66< t jkuljwh ( 15 15 » » S.5 3 .3 7 .S ~.C S.5 S.O S.: 5.3 ppr. Figure 10. H NMR spectrum (400 MHz, CD3CN) of reaction progress for kinetics experiment of a-phenyl-p-xylylene (8) in degassed CD.CN. (15 and 18 are compound numbers given in the text. A: oxygen adducts, I: internal standard, naphthalene, O: oligomers, X: impurity) 185 a-phenyl-p -xylylene •6.5 •7 5 •9 5 -0.0004*-7 57a: g'sO 7806 0 tooo 2000 3000 4000 sooo 6000 7000 Time (Seconds) Figure 11. Plot of In [8] vs time for kinetics experiment. a-phenyl-p -xylylene ys 1 97531 • t329 t R* a 0.9022 o 2 10000 Q 8000 0) c sooo oo o 2 4000 3000 SOOO 6000 Time (Seconds) Figure 12. Plot of [8]-' vs time for kinetics experiment. 186 The major oligomer, that was isolated and analyzed by 'H NMR spectroscopy (Figure 13) and mass spectroscopy (Figure 14), was consistent with dimers 18. ^ph ^ph \ 'T 8 18a.R,= Ph.R2 = H 18b, R,= H,R2 = Ph Generation and Oiigomerization of a,a-Diphenyl-p-xyiyIene (6). (4-[(Tri- methylsilyl)methyl]phenyl)diphenylmethyl benzoate (19) was prepared from 4-[(trimethyl- silyl)methyl]benzoic acid (20) as shown in Scheme 2. Benzoate 19 was found to be only Scheme 2 °Y°" OH Ph—082 ! MeOH.H* PhMgBr KOH ^ ^ ^ ^ tms'^ ims'' tms-^ tms^ 20 21 22 19 slightly soluble in acetonitrile, therefore the oiigomerization studies were conducted in deuterated methylene chloride. a,a-Diphenyl-p-xylylene (6) was prepared as a dilute solution in CDiCh by a fluoride induced elimination of trimethylsilyl benzoate from benzoate 19 and analyzed by NMR spectroscopy (Figure 15). Due to its higher reactivity, Ph Ph—j-OBz Ph^^Ph ^ tbaf.coaaz Room Temperature tms"^ 19 6 187 w - • 91 9) I V0 I I 90 S.O 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure 13. 'H NMR spectrum (400 MHz, CD2CI2) of ethyl acetate extracted TLC spot of a-phenyl-p-xylylene (8) products. (18 is a compound number given in the text, E: ethyl acetate, S: methylene chloride, W: water) 188 ISO 05 iOO 30 - 70 eV SO - 135 360 77 359 20 - 197 1211 267 315 100 300 400 500 500 Figure 14. Mass spectrum (EI) of ethyl acetate extracted TLC spot of a-phenyl-p-xylylene (8) products. 189 i i •niwwirt Wi. xm*. mmst mrm0^ UQl > 751 liwin^liwih Jm 570 t iai4ii 4S0% •w' 3901 L mUf 300 i 210 < 3.5 8.0 7.5 7.0 S.5 6.0 S.5 5.0 :.5 ppa Figure 15. H NMR spectrum (400 MHz, CD2CI2) of reaction progress for kinetics of a,a-ciiphenyl-p-xylylene (6). (I: internal standard, naphthalene) a higher dilution ofp-QDM 6 had to be used so it could be observed prior to formation of its oligomers. Using the same means of comparison of the naphthalene standard peaks to that of the/T-QDM 6 peaks in the NMR spectra, the concentrations ofp-QDM 6 was calculated and the results are presented in Table A-5. First- and second-order kinetic plots were prepared (Figures 16 and 17). 190 a^,ct-Diphenyl-p -xylylene -9 5 s o 2 s 9cU oo c y = -0.0026x.i396 R- s 0.8936 3 200 400 600 300 1000 Time (Seconds) Figure 16. Plot of In [6] vs time for kinetics experiment. ",a-Diphenyl-p -xylylene y » 163 97X.T6577 o R's 0-T55 s ^ 1-50E>05 o (S 5 : OOE-H3S eu uo Mtt > C 0 200 400 600 aoo 1000 1400 Time (Seconds) Figure 17. Plot of [6]-' vs time for kinetics experiment. 191 a,a-Diphenyl-p-xylylene (6) was prepared on a larger scale with non-deuterated solvents. The major oligomer, that was isolated and analyzed by 'H NMR spectroscopy (Figure 18) and mass spectroscopy (Figure 19), was consistent with any of the three dimers, 23, 24, or 25. Ph Phu 6 23 24 25 I S 23.Mor:5 23.24 or 25 il wx—>v_X Jl ' a>. .0 10.0 9.0 3.C 7.0 6.3 5.0 4.0 2.0 2.0 l.C O.Q Figure 18. 'H NMR spectrum (400 MHz, CDiCU) of methylene chloride extracted TLC spot of a,a-diphenyl-j3-xylylene (6) products. (23,24, and 25 are compound numbers given in the text, S: methylene chloride, W: water) 192 256 .2 70 eV 80 422 .0 sn 165.2 94.2 40 344.S 23 200 400 500 3C0 Figure 19. Mass spectrum (EI) of ethyl acetate extracted TLC spot of a,a-dipheiiyl-p-xylylene (6) products. p-Xylylene (1) with Air Kinetics Studies. /7-Xylylene (1) was prepared the same way as above except that a small amount of air was introduced along with the TBAF solution. The 'H NMR spectra are presented in Figure 20. Using die same means of comparison of the naphthalene standard peaks to that of the p-xylylene peaks in the 'H NMR Air Oxygen ^ Adducts 1 spectra, the concentration ofp-QDM 1 was calculated and summarized in Table A-6. First- and second-order kinetic plots were prepared (Figures 21 and 22). Within the 'H NMR 193 ILL... 1 , ,y 2576 s ,iii II. i. . 1 1,1 23<>4« 1, ,y 1,1 1 1 < 1. AtJ. • 1 1 2112 s -I .11 I n •• I - 2030 s . I [ I • ; I a t - I4.t. tUSt i'TH L ^ ' -lA^ 1666 s I M A , .a.v t j »-l^ uu < ,^1 . -liU. ^ 1 ^ • y ^ - U02 j ^ J ^ • ij * ri I ! f*-*' TZX: 1120s EXIIR: ^ 93Ss ijclt lzx T56s xj ss ^OC 3921 't ^ h r " l_cjljll 210 9 i 19 9 —r—r—T 1 ' ' I ' ' 1 ' ' ' , I i 1 3.5 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 ppm Figure 20, 'H NMR spectrum (400 MHz, CD3CN) of reaction progress for short-term kinetics experiment ofp-xylylene (1) with oxygen in CD.CN. (1 is a compound number given in the text, I: internal standard, naphthalene, O: oligomers) 194 p-Xylylene with Oxygen oC fi e • cu o e y , .n notv .fi nan*; R-s 0 9774 0 soo 1000 tsoc 2000 2500 3000 Time (Seconds) Figure 21. Plot of In [1] with oxygen vs time for kinetics experiment. p-Xylylene with Oxygen 5000 4500 y :1 7962X -436.43 4000 R* » 0,964t I 3500 * g 3000 i e e« 2900 r eu s 2000 ^ e 41 1500 >c 1000 500 0 SQO 2000 2500 Time (Seconds) Figure 22. Plot of [1]-' with oxygen vs time for kinetics experiment. 195 spectra there were peaks consistent with oxygen adducts. The 'H NMR spectra of the final products were fi^ee of peaks that can be associated with the dimer or trimer. Determination of Rate Constants. It is clear fi-om the product mixtures that more than a single reaction is consuming the /T-QDM'S. Two known reactions consuming n-QDM's are dimerization and polymerization. Qven the kinetic data in Figures 2-22, a single, simple first- or second-order process is not responsible for the decomposition of the p-QDM's. Therefore trying to overinterpret the rate constants obtained fi'om the plots is not constructive. However, we can at least use the data to get a qualitative picture of the relative reactivity of the four /;-QD^^s. The results of linear regressions performed on the first- and second-order kinetic plots are summarized in Table 1. Table 1. Estimated First- and Second-order Rate Constants" First-order Second- Rate order Rate Constant Constant p-QDM (s') R- (L mol"' s"^) R- Long -term /7-Xylylene (1) 7.0 X 10"' 0.8329 0.6527 0.998 Long -term a-Methyl-p-xylylene (4) 1.1 X 10"^ 0.989 0.277 0.9874 /7-Xylylene (1) 2.0 X 10"* 0.8251 0.0731 0.842 a-Phenyl-/7-xylylene (8) 3.9 X 10"* 0.8011 1.98 0.9104 ot,a-Diphenyl-/7-xylylene (6) 2.3 X 10"^ 0.8608 137.15 0.7235 /7-Xylylene (1) with oxygen 8.2 X 10"* 0.9845 2.29 0.9687 *Rate constants were determined at 20 °C 196 Discussion Errede'° determined that solutions of/?-QDM 1 at -78°C polymerized with an apparent first-order rate constant of 9+1 x 10"^ s'^ The concentration of p-QDM 1, as a function of time, was determined by removing small aliquots and titrating them with iodine. Other similar solutions ofp-QDM I were used at temperatures above -78°C to determine additional rate constants. With the rate constants for the solutions at different temperatures. Errede was able to determine an energy of activation for this reaction to be 8.7 kcal mol"'. Using Errede's first-order rate constants at -78°C and energy of activation, a first-order rate constant at 20°C can be calculated to be 1.6 x 10"' s"'. The data gathered from our p-QDM I short-term kinetic experiment were unclear as to whether the reaction was following first- or second-order kinetics or some combination thereof From plots of In [1] verses time (Figure 5) and [1]"' verses time (Figure 6), the first-order rate constant was 2.0 x 10"* s"' and the second-order rate constant was 0.0731 L moP' s'V Both plots yielded poor linearity. This first-order rate constant is nearly two orders of magnitude from the room temperature rate constant calculated from Errede's data. The data gathered from p-QDM 1 long-term kinetic experiment appear to show the reaction to be proceding primarily by a second-order process with a rate constant of 0.6527 L moP's"' and was reasonably linear in the plot of [1]"' verses time (Figure 3). A plot In [1] verses time (Figure 2) clearly shows that the reaction is not first-order in nature. The difference between Errede's resuhs and the results presented here can be rationalized by considering the conditions of the reaction and the products formed. Errede's experiments were condurted with solutions of/7-QDM 1 were 40 to 100 times more concentrated than the ones used in this study. Higher concentrations lead to higher relative 197 yields of polymers verses dimer and trimer. The reactions were also done at temperatures near or at -78°C. It has been found that higher temperatures favor the formation of dimer. Given the complex nature of the oligomerization reactions, a feasible means of comparing the overall reactivity of/J-QDM'S is to compare their estimated second-order rate constants as long as the concentrations are approximately the same. This comparison can be justified because both dimerization and polymerization began when two monomers react to form a dimeric diradical. Comparing the second-order rate constants for the long-term experiment for /7-QDM's 1 and 4, we can see evidence that a-methyl-p-QDM 4 is less reactive than the parent, p-QDM 1. The second-order rate constants also show the tread that the oc,a-diphenyl-/7-QDM (6) was found to be the most reactive of the series followed by the a-phenyl-p-QDM (8), and /?-xylylene (1). There appears to be two opposing effects controlling the rate of decomposition of these /7-QDM'S: (a) the steric effea that the groups has of blocking one of the two exocyclic methylenes which has the effect of reducing the reactivity and (b) the stabilizing effects the substituents have on the diradical intermediate which has the effect of increasing the reactivity. a-Methyl-p-xylylene (4) appears to be slightly less reactive than p-xylylene, the parent /?-QDM 1. Although the methyl groups should stabilize the radical sites of the intermediate, the methyl must be slowing the reaction by blocking one of the methylene groups from attack. a-Phenyl-/?-xylylene (8) is more reactive that p-QDM 1. The dimeric diradical produced from /J-QDM 8 is should be significantly more stable than the diradical formed for the parent system. Apparently the steric effect of the phenyl group blocking one of the two exocyclic methylenes is not great enough to offset the increase of reactivity caused 198 by the stabilizing of the diradical. a,a-Diphenyl-;?-xylylene (6) is more reactive than the other p-QDM's studied here. The tvvo phenyl groups will significantly stabilize each radical site of the intermediate. It appears that the increase of reactivity caused by stabilizing the diradical cannot be offset by the steric effect of even two phenyl groups thoroughly blocking one of the methylene groups. .Mthough calculating the rate-constants v.-ith a great amount of certainty for the oligomerization of /j-QDM would be difficult even with additional experimental data, it can be seen that the reactivity ofp-QDM's varies with the different a-substituents. ^il • ^i i ^r ' I R R R As stated above for the rate constants for decomposition of/7-QDM's to be comparable to each other, the conditions of the reaction and the products formed must be similar. p-QDM's 1 and 4 under these conditions form dimers, trimers, and oligomers. The products formed from p-QDM 8 are not completely characterized. Their 'H NMR spectra are similar to the spectra of products formed for p-QDM 4. The major component of the ohgomerization products of ;?-QDM 8 has a 'H NMR spectrum and mass spectrum consistent with a cyclic dimer. The products of;7-QDM 6 appear to be dimers. Cyclophane dimers seem unlikely products because in a head to head dimer, the product would be similar to the proposed hexaphenylethane which is not formed in the coupling of two trityl radicals 7." A head to tail cyclophane dimer would have to overcome the steric effects of the two phenyl 199 groups. A possible product is an olefinic product from a para attack onto one of the phenyl groups. Ph.^.Ph 1 Ph 7 Small amount of oxygen dissolved in die solutions of /j-QDM's can have a dramatic effect on the products observed. When a small amount of air is allowed to leak into a NIvIR tube containing a deoxygenated solution of p-QDM precursor, in many cases oxygenated products form exclusively. By comparing the second-order rate constants for the oligomerization of/7-xylylene (1) and the reaction of;7-QDM 1 with oxygen, it was found that even small concentrations oxygen can consume p-QDM's rapidly. Examination of both the first- and second-order kinetics plot (Figures 21 and 22) finds that this consimunation by oxygen is neither a solely first or second-order process. CoDclusions Four reactive /7-QDM's, p-xylylene (1), a-methyl-p-xylylene (4), a-phenyl-/?-xylylene (8), and a,a-diphenyl-p-xylylene (6), were prepared by fluoride induced elimination and characterized by 'H NMR spectroscopy. This was the first report of the 'H NMR spectra of/7-QDM's 6 and 8. All four/?-QDM's were found to form dimers and insoluble oligomers. 200 First- and second -order rate constants were estimated for the decomposition of the four /7-QDM'S. Using the estimated rate constants, the a,a-diphenyl-p-QDM (6) was found to be the most reactive of the series followed by the a-phenyl-p-QDM (8), p-xylylene (1), and the a-methyl-p-QDM (4). The long-term kinetic study of p-QDM 1 was found to decompose primarily by a second-order process, possibly dimerizarion. This is in contrast to the first-order results observed by Errede for die polymerization of /j-QDM 1.^ The other kinetic smdies, including the short-term study ofp-QDM 1, found that both first- and second-order decomposition was occurring. A probable explanation is that polymerization, a first-order process, and dimerization, a second-order process, are occurring at comparable rate. The reaction ofp-QDM 1 with oxygen was found to be rapid in comparison with its oligomerization. Experimental Section Methods and Materials. All materials were commercially available and used as received, except where indicated. 'H KMR spectra were recorded at 400 MHz and at 20 °C unless noted otherwise. '"C NMR spectra were recorded at 100 MHz unless noted otherwise. The residual CHD^CN was used as the internal reference for all 'H NMR spectra unless noted otherwise. Both the GC and the GC/MS analysis were done using a DB-5 column (30m, LD. 0.32 mm, 0.25^1 fikn thickness). Elemental analyses were performed by Iowa State University Instrumental Services, Ames, lA. Drying and Initial Degassing of Acetonitrile- Prior to use as a solvent in the preparation of p-QDM's, acetonitrile-^/j was distilled from P2O5 under argon and methylene chloride from calcium hydride under argon. The solvents were initially degassed by repeated freeze-pump-thaw cycles, except where indicated. 201 /;-XylyIene (1) Long-term Kinetics. To a 5-mL tear-shaped flask 17 mg of TBAF (54 nmol) was added. To a second tear-shaped flask was added 8.5 u.L of a 5.0 x 10'" M solution of naphthalene in CH2CI2 (0.48 umol) and IS [iL of an approximately 0.1 M solution of [p-((trimethylsilyl)niethyl)phenyl]methyl acetate (9)''^ in CH^Ch (-2.2 umol). The CHiCIt was removed at reduced pressures. The two flasks were placed into a nitrogen filled glove bag. To the acetate flask was added about 0.6 mL of degassed CD3CN. The acetate solution was transferred to an NMR tube and the acetate was quantified by 'H NMR spectroscopy. The NMR tube was returned to the glove bag. To the TBAP flask was added about 0.2 mL of degassed CD3CN. The TBAF solution was added to the NMR tube. The sample was protected firom light. The NMR tube was periodically removed from the glove bag for analysis by NMR spectroscopy. The kinetic data are summarized in Table A-1. 'H NMR (400 MHz, CD3CN, 20°C) 5 6.452 (s, 4H), 5.007 (s, 4H). [lit'" 'H NMR (60 MHz. THF-c/^, -80°C) 5 6.49, 5.10]. As the solution is allowed to stand, thep-xylylene (1) was consumed and [2.2]paracyclophane (10)^, [2.2.2]paracyclophane (11)®, and insoluble oligomers were formed. a-Methyl-/7-xylyIene (4) Long-term Kinetics. a-Methyl-p-xylylene (4) was prepared from l-[p-((trimethylsilyl)methyl)phenyl]ethyl acetate'^ (12,1.2 |imol), TBAF (25 }imol) and naphthalene (0.30 lomol) with the procedure used from the above preparation of /7-xylylene (1) in degassed CD3CN. The kinetic data are summarized in Table A-2. 'H NMR (400 MHz, CD3CN) 5 6.713 (br d, J=9.6Hz, IH), 6.466 (br d, J=9.6Hz, IH), 6.314 (br s, 2H) 5.619 (q, J=8Hz, IH), 4.963 (br s, 2E0, 1.848 (d, w/=8Hz, 3H). As the solution is allowed to 202 stand, the a-methyl-p-xylylene (4) was consumed and dimers 13^, timers 14'\ and insoluble oligomers were formed. p-Xylylene (1) Short-term Kinetics. An NMR lube was charged with 25 jiL of a 0.068 M solution of [/?-((trimethylsilyl)methyl)phenyl]methyl acetate (9) in CD3CN (1.7 Limol), 8.0 jil, of a 0.101 Jvi solution of naphthalene in CD3CN (O.Sl ^xmol), and 0./5 mL of CDsG^. A solution of TBAF (6 mg, 20 |amol) in 0.25 mL of CD3CN was prepared in a tear-shaped flask. Both solutions were degassed by repeated freeze-pump-thaw cycles then stored under argon. A 'H NMR spectrum was taken of the deoxygenated acetate 9 solution. The kinetic experiment began by the addition of the TBAF solution to the NMR tube via a s\Tinge through its rubber septum cap. The kinetic data are summarized in Table A-3. The products after standing are similar to the long-term kinetics experiment. 4-[(TrimethyisiIyi)methyilbenzhydroi (17) was prepared by a Gridnard reaction of 4-[(trimethylsiIyl)methyl]benzaldehyde (16)'' (208 mg, 1.08 mmol) with phenylmagnesium bromide (1.1 mmol). The reaction was quenched with saturated NH4CI. Water and ether were added, and the separated ether layer was washed with saturated NaHCOs then saturated NaCl. The organic phase was dried with anhydrous Na2S04, filtered, fireed of solvent, and chromatographed on silica gel (elution with 4:1 hexanes-ether) to afford alcohol 17 (173 mg, 0.64 mmol, 59%) as a colorless oil: 'H N-MR (400 MHz, CD3CN) 5 7.4-7.2 (m, 5H), 7.182 and 6.952 (AA-BB'q, 4H, J=8.0 Hz), 5.690 (d, IH, J=4.0 Hz), 3.666 (d, IH, J=4.0 Hz), 2.045 (s, 2H), -0.067 (s, 9H); NMR (100 MHz, CD3CN) 5 145.54, 140.75, 139.56, 128.27,127.93, 126.98, 126.25, 75.09,25.88, -2.80. Anal. Calcd for Ci7H220Si: C, 75.50; H, 8.20. Found: C, 75.41; H, 8.45. 203 (4-[(TrimethyIsiIyI)methyllphenyl)phenyImethyl Acetate (15). A lO-mL round-bottomed flask was charged with alcohol 17 (27 mg, O.IO mmol), 1 mL dry THF, and 10 drops of dry pyridine. A solution of 0.2 ml acetyl chloride in 1 mL dry THF was added drop wise to the well stirred alcohol solution. The reaction was stirred to 36 h at room temperature. Ether (10 mL) and brine HO mL^ were added to the reaction mi.xture. The separated organic phase was washed with additional brine, saturated NaHCO:,, brine, and dried (MgS04). The solvent was removed under reduced pressure and the resulting oil was chromatographed on triethylamine treated silica gel (elution with 4:1 hexanes-ether) to afford acetate 15 (24 mg, 0.077 mmol, 77%) as a colorless oil: 'H NMR (400 MHz, CD3CN) 5 7.37-7.25 (m, 5H), 7.190 and 6.990 (AA'BB'q, 4H, /=8.0 Hz), 6.703 (s, IH), 2.088 (s. 3H), 2.065 (s, 2H), -0.062 (s, 9H); "'C NMR (100 MHz, CD3CN) 6 169.91, 141.24, 140.65. 136.27, 128.56. 128.15, 127.72, 126.73, 126.55,76.85, 25.96, 20.44,-2.88. a-Phenyl-/;-xyiylene (8) Kinetics. An NMR mbe was charged with 16 uL of a 0.077 M solution of acetate 15 in CD3CN (1.2 jimol), 8.0 jiL of a 0.101 M solution of naphthalene in CD3CN (0.81 ^mol), and 0.75 mL of CD3CN. .AsolutionofTBAF (6 mg, 20 iimol) in 0.25 mL of CD3CN was prepared in a tear-shaped flask. Both solutions were degassed by repeated freeze-pump-thaw cycles then stored under argon. A 'H NMR spectrum was taken of the deoxygenated acetate 15 solution. The kinetic experiment began by the addition of the TBAF solution to the NMR tube via a syringe through its rubber septum cap. 'H NMR (400 MHz, CD3C:N) 6 7.045 (d, /=14 Hz), 6.586 (d, /=14 Hz), 6.519 (s), 5.102 (d, J=14 Hz). The kinetic data are summarized in Table A-4. 204 a-Phenyl-/7-xyIyIene (8) Oligomers. Fifteen milliliters of a 1.28 mM solution of acetate 15 (19.2 umol) in CHjCN was added to a 50-mL round-bottomed flask. A solution of TBAF (63 mg, 190 p.mol) was prepared in a 25-niL tear-shaped flask with 5 mL CH3CN. Both solutions were degassed by repeated freeze-pump-thaw cycles then stored under argon. Inside of a nitrogen-SIled glovebag, the TBAF solution was transferred to the acetate solution via a 10-mL syringe. The reaction mLxture was swirled then allowed to stand for 4 h. The CH3CN was removed under reduced pressure and the resulting residue was dissolved in CDjCN. A 'H NMR spectrum was taken and was similar to the NMR spectrum observed for the kinetics experiment. The CD3CN was removed under reduced pressure and the residue was dissolved in 5 mL of CH2CI2. The methylene chloride solution was washed with 5 mL of water twice, dried with NaiSOa, and the solvent was removed under reduced pressure. The residue was dissolved in CD2CI2 and a 'H NMR spectrum was taken. TLC with CH2CI2 as the elutent revealed at least 11 components with the three major occurring at Rf of 0.89,0.36, and 0.21. The three major spots were scraped individually from the plate and extracted with ethyl acetate. The solvent from the filtered ethyl acetate solution was removed from each under reduced pressure. Only the 0.89 Rf spot had any visible residue. CD2CI2 was added to each sample and 'H NMR spectra was taken of each. The 'H NMR spectra of the 0.36 and 0.21 Rf contained only solvent peaks. The 'H NMR spectrum of the 0.89 spot was subset of the peaks observed for the extracted product mixture. 'H NMR (400 MHz, CD2CI2) 6 7.570 (d, J=8.0 Hz), 7.35-6.68 (m), 6.64-6.52 (m), 6.452 (dd, J=8.0 Hz, J'=1.6), 5.884 (s), 5.839 (s), 5.8 (s), 4.772 (s), 4.69-4.60 (m), 4.35-4.15 (m), 3.37-2.62 (m). A mass spectra was taken of the 0.89 Rf residue. MS (EI) m/z (relative intensity) 361 (10), 360 (35), 359 (20), 181 (18), 180 (100), 179 (41), 178 (23), 167 (11), 166 (11), 165 (25). 205 Methyl 4-[(TrimetfaylsilyI)methyl]benzoate (21) was prepared by a Fischer esterification of 4-[(triinethylsiIyI)methyi]benzoic acid'' (20; 2.29 g, 11.0 mmol) with methanol (50 mL) and H2SO4 (1 mL). After refluxing for 4 h, the reaction mixture was worked up in the normal manner to yield ester 21 (2.398 g, 10.8 mmol, 98 %) as a colorless oil: 'H NMR (30n MHz, CDCI3) ^ 7.869 and 7.025 (AVBB'q, 4H, 7=8.4 Hz), 3.867 (s, 3H), 2.141 (s, 2H), -0.028 (s, 9H); 'T NMR (75 MHz, CDCI3) 5 167.34, 146.81, 129.58, 127.85, 125.95,51.83,27.92.-1.96. (4-[(TrimethylsiIyl)methyi]pheiiyl)diphenyImethanoi (22) was prepared by a Grignard reaction of ester 21 (953 mg, 4.5 mmol) with phenyhnagnesiiun bromide (10.3 mmol). After the normal work up, purification was achieved by crystallization from hexanes to give alcohol 22 (486 mg, 1.4 mmol, 3I%): mp 92.4-93.7 °C; 'H NMR (400 MHz, CDjCN) 5 7.3-7.2 (m, lOH), 7.043 and 6.954 (AA'BB'q, 4H, >8.4 Hz), 4.186 (s, IH), 2.080 (s, 2H), -0.042 (s, 9H); ''C NMR (100 MHz, CD3CN) 5 148.65,143.84,140.39, 128.62,128.55, 128.52, 128.17, 127.72, 82.03, 26.60, -2.02. Anal. Calcd for C23H260Si: C, 79.72; H, 7.56. Found: C, 79.99; H, 7.69. (4-[(Trimethylsilyl)methyl]phenyI)diphenylmethyI Benzoate (19).'® To a 25-mL tear-shaped flask was added 120 mg of 35% potassium hydride dispersion in mineral oil. The potassium hydride was washed three times with dry pentane to remove the mineral oil. Dry THF (2 mL) was added to the flask. A solution of alcohol 22 (111 mg, 0.32 mmol) in 2 mL dry THF was added dropwise to the reaction mLxture then stirred for 1 h. A solution of benzoyl chloride (37 uL, 0.32 mmol) in 1 mL dry THF was added slowly to the reaction mixture. After stirring to 2 h, the reaction mixture was filtered though a glass wool plug to remove excess potassium hydride. Methylene chloride (10 mL) and saturated NaHCOs (10 206 mL) solution were added to the reaction solution. The separated organic phase was washed with brine (3x), dried (MgSOj), and concentrated under reduced pressure to yield benzoate 19 as a colorless oil (59 mg, 0.13 mmol, 41%). Neat sample of benzoate 19 was found to quickly decompose. All samples of benzoate 19 were stored as a solution in methylene chloride-t/i (the solubility of the benzoate was poor in acetonitrile-^/j). 'h NT^IR (300 MHz, CD2CI2) 5 8.131 and 6.979 (AA'BB'q, 4H, /=9.0 Hz), 7.63-7.57 (m, IH),), 7.52-7.45 (m, 5H),), 7.36-7.27 (m, 9H), 2.093 (s, 2H), 0.012 (s, 9H); '"C NMR (75 MHz, CD2CI2) 5 164.89, 144.45, 140.62, 139.34,133.55, 131.95, 130.23, 129.02, 128.95, 128.76, 128.38, 128.35, 128.32, 128.09, 127.94, 127.72, 127.58, 27.073,-1.66. a,a-Diphenyl-p-xylylene (6) Kinetics. An NMR tube was charged with 100 uL of a 0.011 M solution of benzoate 19 in CD2CI2 (l.l [omo I), 8.0 |aL of a 0.101 M solution of naphthalene in CD2CI2 (0.81 umol), and 0.65 mL of CD2CI2. A solution of TBAF (6 mg, 20 umol) in 0.25 mL of CD2CI2 was prepared in a tear-shaped flask. Both solutions were degassed by repeated freeze-pump-thaw cycles then stored under argon. A 'H NMR spectrum was taken of the deoxygenated benzoate 19 solution. The kinetic experiment began by at the addition of the TBAF solution to the NMR tube via a syringe through its rubber septum cap. 'H NMR (400 MHz, CD3CN) 5 7.164 (d, y=14 Hz), 6.604 (d, 7=14 Hz), 6.483 (d, J=IA Hz), 5.055 (s). The kinetic data are summarized in Table A-5. a,a-DiphenyI-/;-xyIyIene (6) Oligomers. Fifteen milliUters of a 0.95 mM solution of benzoate 19 (14.2 pmol) in CH2CI2 was added to a 50-mL round-bottomed flask. A solution of TBAF (50 mg, 145 jimol) was prepared in a 25-mL tear-shaped flask with 5 mL CH2CI2. Both solutions were degassed by repeated freeze-pump>-thaw cycles then stored under argon. 207 Inside the nitrogen filled glovebag, the TBAP solution was transferred to the acetate solution via a lO-mL syringe. The reaction mLxture was swirled then allowed to stand for 4 h. The CH2CI2 was removed under reduced pressure and the resulting residue was dissolved in CD2CI2. A 'H NMR spectrum was taken and was similar to the NMR spectrum observed during the kinetics experiment. The CD2CI2 was added to 4 mL of CH2CI2 and the methylene chloride solution was washed with 5 niL of water twice, dried with Na2S04, and the solution was concentrated under reduced pressxu-e. The concentrated solution was analyzed by TLC with CH2CI2 as the elutent revealed at least 8 components with the major product occurring at Rfof 0.86. The major spot was scraped firom the plate and extracted with methylene chloride. The mixture was filtered and the solvent was removed under reduced pressure. The 'H KMR. '""C NMR, and mass spectrum were taken of the residue. 'H NMR (400 MHz, CD2CI2) 5 7.55-7.4 (m, 2.00H), 7.35-6.25 (m, 39.81H), 4.14-4.64 (m. 3.1 IH), 2.97-2.68 (m, 2.84H). '^CNMR(100MHz,CD2Cl2)5 131.44, 131.37, 130.35, 129.60, 128.54, 128.15, 128.06, 126.33,126.26. MS (EI) m/z (relative intensity) 512 (13), 453 (30), 452 (35), 450 (46), 436 (23), 422 (58), 391 (12), 362 (15), 350 (27), 265 (11), 259 (12), 258 (38), 256 (100), 254(11), 252 (21), 244(11), 243 (11), 242 (13), 241 (14), 239(25), 195(12), 180 (19), 178 (42), 167 (34), 165 (44), 107 (14), 105 (18), 94 (37), 91 (10), 77 (11). /;-Xylylene (1) with Oxygen Kinetics. An NMR mbe was charged with 25 |iL of a 0.068 M solution of [p-((trimethylsilyl)methyl)phenyl]methyl acetate (9) in CD3CN (1.7 umol), 8.0 |iL of a O.lOi M solution of naphthalene in CD3CN (0.81 jimol), and 0.75 mL of CD3CN. A solution of TBAF (6 mg, 20 [imol) in 0.25 mL of CD3CN was prepared in a tear-shaped flask. Both solutions were degassed by repeated fireeze-pump-thaw cycles then stored under argon. A NMR spectrum was taken of the deoxygenated acetate 9 solution. 208 The kinetic experiment began by the addition of the TBAF solution and approximately 0.3 mL of air to the N^ER tube xia a syringe through its rubber septum cap. The kinetic data are summarized in Table A-6. The products that formed are consistent with oxygen adducts. References n) For reviews on p-quinodimethanes see: (a) Errede. L. A.; Szwarc, M. Quart Rev 1958,12, 301. (b) Luzanov, A.V.; Vysotski, Y. B. Journal of Structural Chemistry 1976,17(6), 945. (c) Luzanov, A. V.; Pedash, Y. F. Teor. Eksp. Khim 1977,13(5), 661. (Russian); Chem. Abstr. 1977, 55, 21921. (d) Iwatsuki, S.Adv. Polym. Sci. 1984, 55 (Polym. React.), 93. (e) Mulvaney, J. E. Poly. Sci. Technol. 1984, 25 (Tvevv Monomers Polym.), 311. (f) Iwatsuki, S. "Polymerization and Polymers of Quinonoid Compounds" in The Chemistry of Quinoniod Compounds, Patai, S., Rappoport, Z., Eds.; John Wiley and Sons: New York; Vol. 2, 1988; pp 1067-1111. (g) Yongjun, Y.; Matai, D.; Huixong, L.; Haiping, X.; Xumin, H. Gongneng Gaofenzi Xuebau 1994, 7(2), 195. (Chinese); Chem. Abstr. 1994, 122, 215228. (h) Itoh, T.; Iwatsuki, S. Macromol. Chem. Phys. 1997,198(7), 1997. (i) Greiner, A; Mang, S.; Schafer, O.; Simon, P. Acta Polymer. 1997, 48, 1. (2) Szware, M. Nature 1947,160, 403. (3) (a) Gorham, W. F. In Encyclopedia of Polymer Science and Technology, Gaylord, N. G., Bikales, N. Eds.;Wiley-Interscience: New York, 1971; Vol 15, pp 98-113. (b) Niegish, W. D. In Encyclopedia of Polymer Science and Technology, Gaylord, N. G., Bikales, N. Eds.;Wiley-Interscience: New York, 1971; Vol 15, ppl 13-124. (c) Lee, S. M. in Kirk-Othmer Encyclopedia of Chemical Technology, 3"* ed.; Wiley: New York 1983, Vol 24, pp 744-771. (d) Beach W. P.; Lee, C.; Bassett, D. R.; Austin, T. 209 M.; Olson, R. In Encyclopedia of Polmer Science and Engineering, 2"^* ed.; Wiley: New York, 1989; Vol. 17, p 990. (4) See chapter three of this dissertation. (5) McBride, J. M. Tetrahedron 1974, 30, 2009. (6) Errede, L. A.; Gregorian, R. S.; Hoyt, J. M. J. Am. Ckem.. Soc. 1960, 82, 521S. (7) Trahanovsky, W. S.; Macias, J. R.. J. Am. Chem. Soc. 1986,108, 6820. (8) Compound characterized in chapter three of this dissertation as dimer 3. (9) Compound characterized m chapter three of this dissertation as trimer 14. (10) Compounds characterized in chapter three of this dissertation as dimers 16. (11) Compounds characterized in chapter three of this dissertation as trimers 17. (12) (a) Errede, L. A.; Gregorian, R. S.; Hoyt, J. M. J. Am. Chem. Soc. 1960, 82, 5218. (b) Ito, Y.; Miyata, S.; Natatsuka, M.; Saegusa, T.J. Org. Chem. 1981,-^(5,1043. (13) (a) Fischer, D. R. Ph.D. Dissertation, Iowa State University, Ames, la, 1990, pp 91-121. (b) Trahanovsky, W. S.; Arvidson. K. B. J. Org. Chem. 1996, 61. 9528. (14) Compound prepared in chapter three of this dissertation as acetate 13. (15) WilliamsJD. J.; Pearson, J. M.; Levy, M. J. Am. Chem. Soc. 1970, 92, 1436. (16) Compound prepared in chapter three of this dissertation as acetate 15. (17) Compound prepared in chapter three of this dissertation. (18) Pasquini, M. A.; Goaller, R. Le, Pierre, J. L. Tetrahedron 1980, 36, 1223. 210 Appendix ro 1/1 o CN FN (7) in IP m in w- to C>4 r«.ir> 1^ 1^ s .jlaa o Cvj OI o CO o r- OQ CO CO o OI CO r- CNJ - rs o o CN cn 1 1 1 1 1 1 1 1 1 I f 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 I 1 1 1 1 1 1 Wnr 1' 1 1 i-f r| ITT 1 1 r 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 T 1 1 1 I 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 • • • 1 O o 11.0 10.0 9.0 8.0 1 .0 6.0 3.0 2. 0 1.0 0 .0 Figure A-l. 'H NMR speclrum (400 MHz, CD^CN) of 4-[{lnmclhylsilyl)nicthyl]bcnzhydiol (17). (S: acelonilrilu) o* xi (U lO •o iD a> m CN oi ai CV4 K> I-. oo to U) r-4 r-< f\< M '•Sir' s »o lo —I— I I I ' T ~T" "r~ -\ 220 200 180 160 140 120 100 80 60 40 20 0 ppm Figure A-2. '^C NMR spectrum (100 Mllii:, CDjCN) of 4-|(trimcthylsilyl)mcthyl]bcnzhyclrol (17). (S; acctonitrilc) (U (N ^ (S4 iO r-» y* i/l O* r 4 Ml M O O O 'O tt) tn IN > *N O in ^ «rrof*)rN^«—^ajror^to^c^cuococ iO iO 1 u) r*> »0"0»0»0»'>»0»0»'»»*»r«^»NfN«Nr^oj»- owr^ iJ o o> t4< o o »«. »>. r-> f-> f » r--. r> r« r » r-» i"» r» »•» v- «n to ILLULLy^^I, I ' jj lO »—* OJ llL Jil r"*SDO CO -i-i I I I I I I I I I I 1 1-7-1 'I'l I [ t I I t I I T-TT-r-r T' I ' 'I' • •ri --]-ri I I I I I I I I I'l 11 .0 10.0 9.0 8.0 7.0 6.0 S.O 4.0 3.0 2.0 1.0 0.0 ppm Figure A-3. 'H NMR spectrum (400 MHz, CD^CN) of (4-[(lrimctliylsilyl)mcthylJphenyl)phcnylmcthyl acctatc (15). (S: accto- nitrile) • U €.1 V •-» o m lo ui r«- lo in «N *0 ua e>4 id ir> •- r-^ »- if> rn CO »- O ui ui ay r-^ ui m •V *r »o CN r-j r-< fN "i \ ' Hr I l-J 4I —"I—^ i i ~1— —r- n r—T 220 200 180 160 140 120 100 so r>o 40 20 0 pjini Figure A-4. '^C NMR spectrum (100 MHz, CD^CN) of (4-[(lrimcthylsilyI)mclhyI]phcnyl)phenylmetliyl acetatc (15). (S: accto- nitrile) I r L„.iJiL, » m i [ t i i i i 1 i i I i » m i { » m i i i m 1 i m i i i i 1 ri i m i i i i i i i i i i i i i » i i i i i i i i j i i i i i i i » i i i i i i { i i i i [ 1 t i i [ i i i 1 i i i i i p i i 1 [ i m n i i i i } m itp i i i | i i i i | 1 l't~ 11.0 10.0 9.0 a.O 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 -1.0 ppm Figure A-5. 'H NMR spcclrum (400 MI Iz, CD,CN) of (x-phenyI-/;-xylylcne (8) products with TBAF. (S: acetonitrilc, T: TBAF) •—» o\ wjjii«wiw« rt-r|-ri-f-rjTrT-rp ri f-pm-ry-m*T-|- rr|-»TiT|-T IX .0 10 . 0 0.0 7.0 6.0 Ijpm Figure A-6. Enlargement of Figure A-5. 'H NMR spectrum (400 MHz, CDjCN) of «-phcnyl-/>xyiylene (8) products with TBAF. (18 is a compound number given in the text, S: acetonitrile, T: TBAF) o*-fN'omo»ootor^caca ' S Figure A-7. 'H NMR spectrum (400 MHz, CDjCI,) of methylene chloride extract of rt-phenyl-/;-xylyIene (8) products. (18 is a compound number given in the text, S: methylene chloride, W: water) IN oocs4.-r-»co «»»•>. to oioifNj to o rn c^r^r^i^iTt r^l-^ c^r-^ fO o» o> CO m o 18 VJ 7.9 7.4 6.9 6.4 ppm Figure A-8. Enlargement of Figure A-7 from 8-6 ppm. 'H NMR spectrum (400 MHz, CD^Clj) of methylene chloride extract of a-phenyl-/;-xylylenc (8) products. (18 is a compound number given in the text) CQ CO rs CO •— r*« u* o» (o u> cb o iTi *r ' ' ' ' I I ni NV S A 18 •L IJ —A_ 0 r-* O) o> U3 iO oo r- 0 0 10 0 0 •t 0 rsj -- - 0 0 0 0 CTi r> 0 0 * 1 1 J » 1 n 1 1 « » « 1 I 1 » 1 j ' * * * J 1 ' » ' J » » « » 1 ' « * ' 1 » » M » ' t 1 1 . * 1 ' 1 11111»1 11 .0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-9. 'II NMR spcclruni (400 MHz, CD,CI,) of clliyl acctatc cxtracled TLC spot of (x-phenyl-/^-xylylcnc (8) products. (18 is a compound number given in the text. A: ethyl acetate, S: methylene chloride, W: water) •-(B0O*Au>r-a>fi0t0rsA>r>r>0(» r- f . r- f. r'' r I-"- r- r- r- r- f-- r-~ r- f - f • tA lA iO iO iO *0 *0 LO LO to lO i, V/' ly 18 18 18 18 lo to o 7.9 7.4 6.9 6.4 ppm Figure A-10. Enlargement of iMgiirc A-9 from 8-6 ppm. 'H NMR spectrum (400 Ml Iz, CD,C1^) of ethyl acetate extracted TLC spot of a-phcnyl-/;-xylylenc (8) products. (18 is a compound number given in the text) lO lO W ' I ' • I ' 14 13 11 10 -0 ppm I !• II Figure A-11. 'H NMR spectrum (300 MHz, CDClj) of methyl 4-[(trimcthylsilyl)mclhyl]bcn/,oate (21). (S: chloroform, W: water) Figure A-12. '^C NMR spcctriim (75 MH/,, CDCI,) of methyl 4-[(trimcthylsilyl)mcthyl|bcn/oatc (21). (S: chloroform) iT) u» cu u) ** tj> u (u r*) u) rn lo ^ <7» rn a>c}c>40tor^Ut/'»K> r- o M- »N o» c7>«or^r^ui^^O'0 I-J to OJ ._A_.X I I I I I I I I I I I I I I t I I I I I I I I I I I I I I I I I I n I I I I I I I I M I't I I yi rn"!^^-I1 11.0 10 .0 9.0 8.0 7.0 6.0 5.0 4 . 0 3 . 0 2 . 0 1.0 0.0 ppm Figure A-13. 'H NMR spcctrum (400 MHz, CD^CN) of (4-l(trimcthylsilyl)niethyl]phenyl)(liphenylmcthanol (22). (S: acctoni- trilc) ^ r-j ^ f-^ o o» ^ kO ^ c*« ^ c>< to 1 SS'-^I to to J....I ,1, -Ji L .u....,.,..a. 1 ' I ' I ' I ' r "f—I—r- 1 1 1 ' 1 • 1 1 1 1 1 r- l—•—I—'—T""—I—'—I—'—I—'—I—'—T 220 200 180 160 140 120 100 80 60 40 20 0 ppm Figure A-14. '^C NMR spectrum (100 MHz, CD,CN) or(4-[(lrimcthylsilyl)mclhyllphcnyl)diphenylmethanol (22). (S; acetoni- trilc) av/i*—oo»~'«r»-ior^u> iijILLLL I'llj^i I I I I I I ' ' ' \JJU 11111V 'I'l^ i s K K L .aULji, _Jl.. JIlL r*O Sr—( rsj •— o S »•-' 00 o) co o r— — o m C7) rw m " " 1 " '' I " " I' 1111111111 I '' "T 111111111111111 111111111 rn-j-m-i-pT-r 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 - J . 0 ppm iglire A-15. 'H NMR spcctrum (300 MHz, CD,CI,) of (4-[(trimcthylsilyl)mclliyl]phcnyl)diphcnylmcthyl bcnzoiUc (19). (E: ethyl ether, S: methylene eliloride) O *NCJ»»-Or^r^<7) a» o> — r-*. f— •* u} '*u>'0i/ic7)r^0cjir«-o 1/ s "1 I I ' rI • r -~i— 1—•—I—'—I—•—r "T T1 r- _T , p—,—I—,—I , 1_ 1 I I I r 200 IBO 160 140 120 100 80 60 40 20 0 ppm Figure A-16. '^C NMR spectrum (75 MHz, CD^CI,) of (4-[(trimcthylsilyl)methyI]phcnyl)diphenylmelhyl ben/.oate (19). (S: methylene cliloride) r lO l-o 23,24, or 25 .Jl. •r II I I M I I [~rt II I I I rr |i i i i ; i iti [ i i i i| i i ii ) ? i i i ; > i i » | i i » i| i » i i| » > i m i » » rp-r-T-rr i » i i | i i i i | > i i i | i i ii i rfi i| i « i i | i i i -j i i ri |i i i i } i ri r ( f-t-t IX.0 10.0 9,0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 3.0 0,0 ppm Figure A-17. 'H NMR spectrum (400 MHz, CD^Cl,) of cx,(x-diplicnyl-/>xylylene (6) products with TBAF. (23, 24, and 25 are compound numbers given in the text, S: methylene chloride, T: TBAl') ... 23, 24, oi 25 lo to 00 r jS iji 11 —JL ^ rfTT 1 rr rj^TTi 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3. 0 1 . 0 0 . 0 pplU Figure A-18. Riilargemcnt of Figure A-17 from 12 to -1 ppm. '11 NMR spectrum (400 MHz, CD,CIJ of (x,(x-iliphenyl-/^-xylylciic (6) products with TBAK (23, 24, and 25 are compound numbers given in the text, S: methylene chloride, T; TBAF) 23, 24, 01 25 s >o to VO xJ -T 1 1 1- a.o 7.0 6.0 b.O ppm Figure A-19. Enlargement of Figure A-17 from 8.5 4.5 ppm. 'H NMR spectrum (400 MHz, CDjCl,) of a,a-diphenyl-/)-xylylene (6) products with TBAF. (23, 24, and 25 are compound numbers given in the text, S: metliylene chloride) r-> ^ o «o io iO ^^ O lO »*> r>>- lo io o> (Nt tn to r-. rg iO fN o» r-> ^ a> V ^ *o ro »o •«r o kO tA 4/> !/> lO »N SM iiii I "1—'—I—'—I—•—r ~T ' T 1 ' 220 200 180 160 140 120 ICQ 80 60 40 20 0 ppm Figure A-20. '^C NMR spectrum (75 MH/, CD^CIj) of a,a-cliphcnyl-/;-xylylcne (6) products with TBAF. (S: methylene chlo- ridc) 220 200 180 160 140 120 100 80 CO 40 Figure A-21. Enlargement of Figure A-20 from 230 to -10 ppm. "C NMR spectrum (75 MM/., CD,C1,) of a,a-diphcnyl-/;-xylylcnc (6) products with TBAF. (S: methylene chloride) inoiO«7>cu«Oi*'> J.i. J I I I 1 1 I "mi^' 1^' p, ' \V 10OJ 10 UJ UAwJV Ti-n • j-rrrT-jt rrf"|'0'FT'|-iT if|rT'i i |> i i > rr i"ii-|-i T~ 11,0 10.0 9.0 B.O 0.0 ppm Figure A-22. 'H NMR spcclmin (400 MHz, CDjClj) of melhylciie chloride extracted TLC' spot of a,(x-diphcnyl-/>-xylylcnc (6) products. (S: methylene chloride, W: water) •< t- ro o CO (O o m kO 0> O <7« cr» »n «7» ul ti> to •- c^i € i cnI ^ to rO CJ CN r>* W> r-s r>- *0 lu i *0 to *0 *f* u> u> ^ ^ to <0 *0 \l 1^ A>L. AA.. t t 7.4 7.2 7.0 6.0 6.6 6.4 6.2 ppin Figure A-23. Enlargement of Figure A-22 from 7.6 6 ppm. 'H NMR spectrum (400 MHz, CDjC'l,) ofmethylenc chloridc ex tracted TLC spot of s 220 200 180 160 140 120 100 80 60 40 20 0 ppin Figure A-24. '^C NMR spectrum (75 MHz, CD^Clj) of methylene chloride extracted TLC spot of (x,tx-diphenyl-/j-xylylene (6) products. (S; methylene chloride) ppm 10 20 30 40 50 60 70 80 90 100 110 120 130 "b 140 150 ppm riini (CDjClj) ofmcthylene chloride exlractcd TLC spot of u,(x-diphcnyl-/;- ppm 123- 124- 125- 126- 127 128- 129- 130- 131 132- 133- 134 7.7 7.6 7.5 7.4 7.3 7.2 7.1 7.0 6.9 6.8 6.7 6.6 6.5 ppm Figure A-26. Enlargement of Figure A-25. HETCOR spectrum (CD,C1,) of metiiylcne chloride extracted.spot of a,(x-diphenyl-/j-xylylene (6) products. Tabic A-I. 'H NMR and KiiicUc Data for/;-Xylylcnc (1). relative areu of peak inlegralion Time, s fi7.9iMr83' ft 7.53-7.45" ft 7.30-7.16'* ¥7rM-7.(^'' 8 85.10-5.03' |1).M I MH) 0 89 r48 r?6 7).00193 1200 1.00 1.01 1.44 1.93 0.001006 19800 1,00 0.90 0.10 0.13 7.261i-05 57600 1.00 1.05 0.04 0.05 2.63F.-05 " Naphthalene, iiUenial standard. Starling acetate 9. "^/j-QDM I. Tabic A-2. 11 NMK and Kinctic Data for a-Mcthyl-/>-xylylcnc (4). relative area of peak inlegraliun Time, s 67.91-7.83* 6 7.53-7.45* 6 7.30-7.16'' 6 7,14-7.00*' 6 6.47-6.43' 65.99-5.50' L4|. M 0.1 1.01 1.01 2.00 1.91 0.001469 600 1.19 1.46 2.00 2.50 0.001289 5400 2.43 2.59 2.00 2.25 0.000644 19800 8.46 8.40 1.60 2.05 0.000164 Nuplithaluiic, iiilcrnal .standard. '* .Starting acetalc 12. "/^-QDM 4. 239 Table A-3. 'H NIVIR and Kinetic Data for/>-XylyIene (1). relative area of peak integration Time, s 57.93-7.80' 5 7.53-7.44' 5 6.46-6.42'^ 55.10-5.03" [1],M 210 0.048294 0.251352 0.7337 0.906805 0.002968 301 0.001696 0.163426 0.710012 0.893408 0.002901 392 0.020532 0.103578 0.707207 0.89927 0.002907 483 -0.02625 0.22485 0.607098 0.911598 0.002748 574 0.067598 0.170469 0.547379 0.81587 0.002466 665 -0.03523 0.395089 0.616911 0.704518 0.002391 756 -0.02497 0.248015 0.624218 0.843609 0.002656 847 -0.00668 0.265821 0.517171 0.768882 0.002327 938 -0.04449 0.3761 0.417877 0.861698 0.002315 102? 0.010344 0.282544 0.532707 0.738289 0.0023 1120 0.008533 0.272811 0.514482 0.78481 0.002351 1211 0.040049 0.26137 0.433708 0.770473 0.002179 1302 -0.00099 0.374713 0.476467 0.721932 0.002168 1393 0.008024 0.268993 0.47085 0.7883 0.002278 1484 0.022874 0.227467 0.560201 0.71936 0.002315 1575 -0.0862 0.226261 0.47046 0.672973 0.002069 1666 -0.03608 0.258866 0.531499 0.731743 0.002286 1757 0.070908 0.252365 0.512628 0.722891 0.002235 1848 -0.02935 0.33479 0.47993 0.653678 0.002051 1939 -0.15258 0.299196 0.479755 0.607356 0.001967 2030 -0.08805 0.146113 0.401155 0.736442 0.002058 2121 -0.08961 0.158234 0.47838 0.65446 0.00205 2212 0.027896 0.149039 0.500584 0.608838 0.002007 2303 0.143587 0.256084 0.385533 0.734845 0.002027 ^ Naphthalene, internal standard. "p-QDM 1. Table A-4. 'H NMK and Kinctic Data for a-IM»enyl-/»-xylylenc (8). relative area of peak inleBralioii Time, s 87.91-7.83" 8 7.53-7.45" 8 71)8-7,Op' 8 6.62-6.56 5 6,55-6,49'" 65,13-5,07'* 18).M 210 100 99.9998 18.0371 18.0907 48,0001 39,1927 0.000635 301 83.3373 84.6375 23.9578 22,6364 59,1395 44,0005 0.000849 451 95.2146 99.8187 20,1228 18.6057 53.2802 42,4276 0,000705 661 95,0835 99.3803 16,1206 16.7088 40,9705 30,5409 0,000509 871 99.4667 106.241 1 1,9976 13,0714 27,7277 20,9891 0,000331 1 141 94.4742 97.7418 9.99881 1 1,1 183 19,2935 17,1222 0.000289 1411 98.2714 100.989 8,33601 7,62207 15,6353 14,0329 0,000228 1741 91.6172 103.173 7,48672 8.33998 1 1,4426 12,85 0.0002 14 2071 98.0135 105.306 7,25946 9,3233 1 7.88067 7.6391 3 0 000122 2461 99.4872 104.451 5,35352 8.691 19 6,64913 8,86125 0.000141 2851 95.1 114 109.173 4,24915 10.3047 2,8963 7,61 194 0.000121 3301 99.2261 105.859 5.96816 8.52456 2,83161 9.78493 0,000155 3751 95.5595 1 10.601 3.52814 5.74849 1,26516 7.86371 0.000124 4321 98.2964 109.426 7.56926 8.01077 1,64412 6.1071 9.53l':-05 4891 99.79 108.541 5,36589 4,36513 -2.45295 6,9077 0.000107 5881 96.5816 106.442 1,60303 6.60123 -3,82929 4,7301 7 551--05 a Naphthalene, inlernal standard. '•/'-QDM 8. Table A-5. 'H NMR and Kinctic DsUa for a,a-l)iplienyl-/j-xylylcnc (6). relative area oi'peak integration Time, s 87.91-7.83' 8 7.53-7.45" 8 7,08-7.01'' 8 6.62-6.56'' 8 6.55-6.49'' K)|. M 210 20.5049 19.1465 0.835799 0.776624 0.209931 4,961'-05 300.1 20.1638 16.7548 1.09792 1.02767 0.538339 7.79H-05 390,2 19,4372 16.5002 1.2729 1.22946 0.578094 9,26l:-05 480,3 19,2173 16,41 16 1.25765 0.796675 0,226992 6.921'-05 570.4 19,5417 17,1 102 1.04375 0.79158 -0.21302 4.78F.-05 660.5 18.9346 16,6177 0.81566 0.72203 -0.17734 4,13R-05 750.6 18,6361 16,9156 0,861598 0.334138 -0.04333 3,51i-05 840.7 19,0949 16,703 1 0.584589 0.50279 -0.16212 2.791--05 930.8 18.5741 16.2915 0.560523 0,563514 -0,5781 1.69li-05 1020,9 19.1205 16.8079 0.7221 1 -0.011 18 -0.47 119 7.2 Hi-06 1 1 1 1 18,7689 16.2412 0.596938 0.081959 -0.64995 8.931i-07 1201,1 19,3051 17.1376 0,428173 0.62909 -0.42285 1.88li-05 1291.2 19,5347 16.483 0.52933 0.197085 -0.4926 7.01E-06 1381.3 19,6415 16,6144 0.446632 0.173063 -0.36503 7,591i-06 1471.4 18,8405 16,781 0.602632 0.246199 -0.70088 4.491--06 'Naphthalene, internal standard. 242 Table 6. NMR and Kinetic Data for/7-XylyIene (1) with Oxygen. relative area of peak integration Time, s 57.93-7.84^ 5 7.53-7.44^ 5 6.43-6.42" 55.10-5.03" [1],M 210 99.999 99.9989 90.746 102.453 0.001646 301 92.7318 92.7624 112.678 128.989 0.002073 392 89.1111 88.6605 101.155 117.85 0.001894 483 85.8708 85.7835 87.3853 102.327 0.001644 574 84.5299 83.6038 73.2834 87.6173 0.001408 665 81.0243 80.1458 62.4669 76.3488 0.001227 756 79.2797 78.2923 54.0955 66.1386 0.001063 847 78.2583 77.4999 48.7108 58.2442 0.000936 938 77.9478 76.7228 42.9164 53.6728 0.000862 1029 75.6927 74.6874 38.0938 47.9285 0.00077 1120 76.2125 73.8117 34.3869 43.0425 0.000692 1211 73.2002 72.4405 31.1945 38.7838 0.000623 1302 72.7645 72.193 26.9175 35.4559 0.00057 1393 72.8403 71.3073 26.1364 32.8522 0.000528 1484 72.5571 71.0015 22.8624 29.7907 0.000479 1575 71.7064 70.3724 21.8349 28.4492 0.000457 1666 70.6171 70.218 20.6766 25.6753 0.000413 1757 70.8347 70.5084 19.1845 24.3578 0.000391 1848 71.6326 70.4296 17.7603 23.6037 0.000379 1939 71.7427 68.2428 17.0154 21.9963 0.000353 2030 71.3134 68.7554 16.0637 21.092 0.000339 2121 69.7382 68.0428 14.9259 19.6365 0.000316 2212 69.2637 67.8416 14.4181 18.1873 0.000292 2303 69.1268 67.1357 13.3439 15.8301 0.000254 2394 68.5809 65.4466 11.5931 15.7678 0.000253 2485 67.4901 66.6011 10.306 13.1747 0.000212 2576 67.5058 65.3199 10.1765 13.387 0.000215 ^ Napthalene, .internal standard. p-QDM 1. 243 CHAPTER 5. EVTOENCE FOR THE GENERATION OF /?-DIPHENOQUINODI]VIETHANE Written in the style suitable for publication in the professional journals published by the American Chemical Society Steven P. Lorimor and Walter S. Trahanovsky Abstract p-Diphenoquinodimethane (5), a biphenyl-based reactive p-quinodimethane (p-QDM), is a highly reactive, cross-conjugated molecule. (4-[4'-((Trimethylsilyl)meth- yl)phenyl]benzyl)diisopropyhnethylammomum iodide (13) was prepared which yields p-QDM 5 upon fluoride induced elimination of trimethylsilyl iodide and diisopropylmethylamine. Although p-QDM 5 was not directly observed by 'H NMR spectroscopy, evidence of its formation was found in the products formed from its reaction with oxygen or in its oligomerization products. Upon reacting ammonium salt 13 with TBAF in the presence of oxygen, products consistent with aldehydes and peroxides were observed by 'H NMR spectroscopy. With careful exclusion of oxygen, ammonium salt 13 reacts with TBAF to form several products possibly including [2.2]-(4,4')-biphenylophane, cyclophane 7. Introduction p-Quinodimethanes (p-QDM's) are reactive, cross-conjugated cyclic molecules that have been invoked as transient intermediates in a number of reactions and interesting fundamental molecules.' Commercially useful polymers have been developed from p-QDM's." p-Xylylene (1), the parent benzene-basedp-QDM, was first proposed as an intermediate in the pyrolysis of p-xylene that yielded poly-/?-xylylene.' Our research group 244 found that/>-xyIylene and several other simple, reactivep-QDM's can be observed at room temperature by 'H NMR spectroscopy by preparing them as dilute solutions/"^ Trimers of the p-QDM's were observed which is strong evidence that they dimerize via a dimerical diradical in a stepwise mechanism. The first isolable derivative of d-QDM 1 was 7 J,8,8-tetraphenyl-p-xylylene, Thiele's hydrocarbon (2).^ Although p-QDM 2 does react with oxygen, few precautions must be Ph. ^Ph i| T 1 2 taken in its manipulation. In 1907 Chichibabin prepared the more reactive [l,r-biphenyl]-4,4'-diylbis[diphenylmethyl], Chichibabin's hydrocarbon (3), in an attempt to synthesize diradical 4.^ The p-QDM 3 readily yields polymeric peroxides when exposed to Ph^Ph Ph^Ph Ph Ph Ph . Ph 3 4 air.^ The unsubstituted analog ofp-QDM 3 is /7-diphenoquinodimethane (5).' p-QDM 5 is expected to be highly reactive^® and has received a moderate amount of attention by theoretical chemists." 245 /j-QDM 5 has been proposed as an intermediate in several reactions. /j-QDM 5 is a probable intermediate in the pyrolysis of disulfone 6 that yields [2.2]-(4,4')-biphenylophane, cyclophane 7 (Scheme 1).'" Polymers ofp-QDM 5 have been prepared by elimination of hydrogen chloride with potassium r-butoxide from 4-chloromethyl-4'-methylbiphenyl'' and by cathodic elimination of bromine from 4,4'-bis(bromomethyl)biphenyl.''^ Scheme 1 500°C • j — \ 0.1n 1 TnrrTor '/ SO2 To prepare p-QDM 5, a precursor compound with the proper leaving group must be prepared. Ito prepared poly-/7-xylyIene and [2.2]paracycIophane from ammonium salt 8 by a fluoride induced elimination.'^ Our group prepared dilute solutions ofp-QDM 1 by fluoride -N(CH3)3 I - -j _ 1 ' r - TBAF i ^ i —\ , j — CH3CN.25°C I ^TMS induced elimination of trimethylsilyl acetate from [p-((trimethylsilyl)methyl)phenyl]methyl acetate."^ Oncep-QDM 5 has been prepared as a dilute solution, 'H NMR studies can be 246 AcO^ ^ , TBAP. CDJCN Room Temperature ^TMS preformed. By analyzing the products produced in the reaction, a better understanding of p-QDM 5 can be established by comparing it to the products ofp-xylylene (1). In this paper we report the synthesis of a precursor to /?-QDM 5, attempts to observe p-QDM 5 by 'H NMR spectroscopy, and characterization of reaction products. Results Preparation of a Precursor to /7-Diphenoquinodimethane (5). The preparation of acetate 9, a possible precursor of p-QDM 5, was attempted by the sequence of reactions outlined in Scheme 2. When methyl 4'-methyl-4-biphenylcarboxylate (10) was reacted with Scheme 2 C02Me Br 1)'^9 HO^ OH 1 2)B(OMe)3 I methyl p-bromobenzoate ;| 1)LDA ,-j^ 3)10% H-,S04 Pd(0Ac)2. PPri3 2)TMSCI ref20 ref21 ref22 CHj CH3 14 10 COjMe CH2OH CH2OAC AcCI I LAH pyndine y ^ ^ ^ TMS^ TMS^ TMS^ 12 9 247 LDA and trimethylsilyl chloride, A'^V-diisopropyl-4-[4'-((trimethylsilyl)methyl)phen- yl]benzamide (11) was formed instead of the intended product, methyl 4-[4'-((trimeth- ylsilyl)methyl)phenyl]ben20ate (12). The synthesis of acetate 9 was abandoned for the COaMe i COjMe TMS^ 1)LDA 12 2) TMSCI CHj 10 TMS^ 11 synthesis o f (4-[4'-((trimethylsilyl)methyl)phenyl]benzyl)diisopropyImethylammonium iodide (13), an alterative precursor to />-QDM 5. Ammonium salt 13 was prepared from amide 11 by the method outlined in Scheme 3. Reaction of 7;-Diphenoqumodimethane (5) with Oxygen. A dilute solution of ammonium salt 13 was prepared in dry acetonitrile-^/i and was analyzed by 'H NMR spectroscopy. The diluted solution of ammonium salt 13 was reacted with a solution of TBAF (Scheme 4). 248 Scheme 3 ; ! ' ^ r O 5!!!^ . ^ IMS' TMS'^ TMS-^ 11 16 13 Scheme 4 I TBAF, CD3CN I ! Aldehydes *" ^ and Room Temperature j oxygen adducts TM: 13 The solution was then analyzed by 'H NMR spectroscopy. The two spectra are presented in Figure 1. Although there are no peaks assignable to /7-QDM 5, the spectrum of the products show signals for aldehydes (~ 5 10) and benzyhc methylenes adjacent to oxygen atom(-- 5 4.5). All of the aromatic signals are downfield of 5 7.2, which is consistent with peroxide products. 249 Oligomerization of /^-Diphenoquinodimethane (5). A dilute solution of ammonium salt 13 was prepared in dry deoxygenated acetonitrile-tfj and was analyzed by 'H NMR spectroscopy. The solution of ammonium salt 13 was reacted with a solution of TBAF (Scheme 5). The resulting solution was analyzed by 'H NMR spectroscopy after 10 min. 13 13 13 13 13 13 13 Before addition I—'WiX T S Y T : T After 20 min r B.C 4.0 2.0 Figure 1. 'h NMR spectrum (400 MHz, CD.CN) of reaction progress of p-diphenoquinodimethane (5) in non-deoxygenated acetonitrile-cfj. (13 is a possible precursor ofp-QDM 5, C: common product that appears in both the non-deoxygenated and deoxygenated experiments, S: acetonitrile, T: TBAF) 250 Scheme 5 r: ^ TBAF. CD3CN 0 Other Room Temperature Products A 1-^ TMS' 13 The solution was stored carefully to exclude oxygen for 2 h then analyzed again by 'H NMR spectroscopy. The spectra obtained in this NMR study are presented in Figure 2. Although the 'H NMR spectra does not show peaks assignable to p-QDM 5, the reaction produces a limited number of products. One product that can be tentatively assigned by 'H NMR spectroscopy, based on its match of known literature values,'" is cyclophane 7. Based on similar peaks in the spectra of oxygenated and deoxygenated samples, the peaks downfield could be unreacted starting material or some other impurity. The remaining peaks have not been assigned. The sample was extracted using methylene chloride and then the extract was concentrated under reduced pressure. The resulting residue was analyzed by 'H NMR spectroscopy (Figure 3). In this spectrum, the downfield peaks seen in Figure 2, possibly assignable to starting material or oligomers, are no longer present. The peaks assignable to the cyclophane products remain along with what appears to be an AA'BB' system. An unusual observation was noted that both the AA'BB' system tentatively assigned to cyclophane 7 and the unknown's AA'BB' system have similar integrations. 251 Discussion It is unclear why iVJV-diisopropyl-4-[4'-((trimethylsilyl)methyl)phenyl]ben2aniide (11) was formed instead of the intended product, methyl 4-[4'-((trimethylsilyl)methyl)phen- yljbenzoate (12) when methyl 4'-methyl-4-biphenylcarboxylate (10) was reacted with LDA and trimethylsilyl chloride. Many methyl esters are not considered to be very reactive towards the conversion lo N, jV-dialkyl amides,'^ but strongly basic conditions have been known to catalyze the reaction.'' Although p-QDM 5 was not observed directly by 'H NMR spectroscopy, there is strong evidence that it was formed by the fluoride induced elimination of trimethylsilyl iodide and diisopropyhnethylamine. p-QDM 5 forms similar products to p-xylylene 1 when it is allowed to react with oxygen. The 'H NMR spectra of both product mixttires contain peaks with similar chemical shifts (~ 5 10,4.5)."' The 'H NMR spectrum of the product mixture produced in the deoxygenated acetonitrile-i/j is consistent with there being four or fewer products. One product is likely to be the cyclophane 7 because of its match with the literature values.'" The downfield peaks (labeled C in figures 1 and 2) which were not extracted into the methylene chloride layer could be polymeric, non-cyclophane addition products, or starting material with its chemical shift altered because of the addition of TBAF. The remaining AA'BB' signals (labeled U in figures 2 and 3) are difficult to interpret because they are shifted up field compared to most aromatic protons. This shift upfield is consistent with a cyclophane product, similar to a cyclic trimer, with a distorted aromatic ring but one that is not as much as distorted as that of cyclophane 7. The fact that the unassigned aromatic signals have similar integrations to 252 13 13 13 13 13 1 Before addition UL y. U 77 C , U After 10 min www JuJ I T j U ^ 7 i u After 2 h I 'AJi WWMM Ju lil>w •^' I ' • " I " " : " ' • • " I " • ' I 10.0 9.0 a.o 7.0 6.0 5.0 4.0 3.0 PPm Figure 2. 'H NMR spectrum (400 MHz, CD.CN) of reaction progress of p-diphenoquinodimethane (5) in deoxygenated acetonitrile-Jj. (7 and 13 are compound numbers given in the text, C: common product that appears in both the non-deoxygenated and deoxygenated experiments, T: TBAF, U: unknown compound) 253 o O) 1 o o csi - i CM 1 ! •T-P" 8.0 7.0 6.0 5.0 4.0 3.0 ppm Figure 3. 'H NMR spectrum (400 MHz, CD.CN) of methylene chloride extract of p-diphenoquinodimethane (5) products in deoxygenated acetonitrile-^/j. (7 is a compound number given in the text, M: methylene chloride, T: TBAF, U: unknown compound) 254 those of the peaks tentatively assigned to cyclophane 7 leads one to question whether or not the assignment of the peaks to cyclophane 7 is correct. A probable next step is to attempt to preparedp-QDM 5 as a similarly dilute solution but on a larger scale. If the reaction was carried out on a larger scale, the products might be less difficulty to isolated and characterized. Once the products are firmly determined, focused efforts could be made in order to observe /^-QDM 5 directly. Because the fluoride induced elimination is both facile and mild, further studies may allow direct observation ofp-QDM 5. High dilution studies similar to the one used for a,a-diphenyl-p-xylylene" could be used to observe /7-QDM 5 by 'H NMR. Flow NMR has 1 ^ been used to observe reactive molecules such as benzocyclobutadiene ', 1,2-dimethyl- ene-I,2-dihydronaphthalene,'' and o-xylylene'^ using a similar fluoride induced elimination as a means of preparation. Conclusion The preparation ofp-diphenoquinodimethane (5) by fluoride induced elimination of trimethylsilyl iodide and diisopropyhnethylamine from ammonium salt 13 is probable based on the products observed. When exposed to oxygen, the product's 'H NMR spectrum was similar to that of/?-xylylene 1 with signals from aldehydes and peroxides. With careful avoidance of oxygen in the solution, evidence for [2.2]-(4,4')-biphenylophane (7), which is analogous to the [2.2]cyclophane found in the oligomerization of/7-xylylene (1), was obtained. Experimental Section Methods and Materials. All materials were commercially available and used as received, except where indicated. Prior to use as a solvent in the preparation of/j-QDM 5, 255 acetonitrile-Jj was distilled from P2O5 under argon and initially degassed by repeated freeze-pump-thaw cycles, except where indicted. 'H NMR spectra were recorded at 400 MHz unless noted otherwise. '•'C NMR spectra were recorded at 100 MHz unless noted otherwise. The residual CHDiCN was used as the internal reference for all 'H NMR spectra unless noted otherwise. Both the GC and the GC'^S analysis were done using a DB-5 column (30m, I.D. 0.32 mm, 0.25^ film thickness). Elemental analyses were performed by Iowa State University Instrumental Services, Ames, lA. /7-Tolylboroiiic Acid (14) was prepared in a 65 % yield by the method of Matsubara'° but on a 0.131 mole scale. 'H NTvER. (300 MHz, CDCI3) 5 8.136 and 7.322 (AA'BB'q, /=7.8Hz, 4H), 2.454 (s, 3H); mp 247.5-250.3 =C (lit.-° mp 245-247 °C). Methyl 4'-MethyI-4-biphenyIcarboxyIate (10) was prepared in a 61% yield on 8.5 mmol scale using a method similar to the method used by Huff^' for the syndiesis of unsymmetrical biaryls using a modified Suzuki cross-coupling: 4-biphenylcarboxaldehyde. 'H NTvIR (400 MHz, CDCI3) 5 8.071 and 7.627 (AA'BB'q, /=8.8 Hz, 4H), 7.510 and 7.256(AA'BB'q, /=8.8 Hz, 4H), 3.918 (s, 3H), 2.389 (s, 3H); NMR (100 MHz, CDCI3) 5 167.1, 145.6, 138.2, 137.1,130.1, 129.7, 128.6, 127.1, 126.8, 52.1 ,21.2. A'iiV-Diisopropyl-4-[4'-((trimethyIsilyl)metfayl)phenyI]benzamide (11) was prepared in a 21% yield from A'',iV-diisopropyl-4-[4'-((trimethylsilyl)methyl)phen- yl]benzlaniine (0.14 mmol) by a method similar to the method used by Leung" to prepare methyl 2-[(trimethylsiIyl)methyl]benzoate. The preparation was intended to prepare methyl 4-[4'-((trimethyIsilyl)methyl)phenyl]benzoate (12). ^H NMR (400 MHz, QDCI3) 5 7.569 and 7.345 (AA'BB'q, >8 Hz, 4H), 7.441 and 7.051 (AA'BB'q, J=8 Hz, 4H), 3.92 (br s), 3.466 (br s), 2.104 (s, 2H), 1.475 (br s), 1.205 (br s), -0.002 (s, 9H); IR (neat, cm'*) 2958, 256 1628,1436,1337; GC/MS m/z (relative intensity) 442 (6), 441 (14), 370 (6), 369 (13), 368 (25), 367 (7) M", 366 (9), 270 (7), 269 (22), 268 (51), 267 (100), 266 (17), 265 (18), 264 (10), 263 (11), 262 (6), 251 (6), 188 (5), 165 (25). AyV-Dusopropyl-4-[4'-((trimethylsilyl)methyl)phenyI]benzylamiiie (16). A 100 mL three-necked round-bottomed flask with a stir bar, condenser, addition funnel, and argon gas inlet was charged with lithium aluminum hydride (80 mg, 2.1 mmol) and 5 mL of dry ether. A solution of.V,iV-diisopropyl-4-[4'-((trimethylsiIyl)methyl)phenyl]benzamide (11, 280 mg, 0.76 mraol) in 15 mL of ether was added dropwise to the LAH mixture. After the addition was complete, the mixture was heated to reflux for 1 h. After the normal workup, amide 11 (210 mg, 0.59 mmol, 78%) was isolated as an oil. 'H NMR (400 MHz, CD2CI2) 5 7.521 and 7.443 (AA'BB'q, 7=8.0 Hz, 4H), 7.477 and 7.085(AA'BB'q, J=8.4 Hz, 4H), 3.690 (s, 2H), 3.040 (sept, /=6.4 Hz, 2H), 2.140 (s, 2H), 1.061 (d, 7=6.4 Hz, 12H), 0.038 (s, 9H); ''CNMR(100MHz,CD2Cl2) 5 142.6, 140.1,139.5, 137.2, 129.0, 128.9,127.1,126.7,49.1, 48.3,27.1,21.1,-1.7. AnahCalcd for C23H35NSi: C, 78.12; H, 9.98; N, 3.96. Found: C, 78.18; H, 9.87; N,3.90. (4-[4'-((Trimethylsilyl)methyI)phenyI]benzyl)diisopropylmethylammoaium Iodide (13) was prepared in a 14 % yield by a method similar to the method used by Ito"^ to prepare [o-[l-(trimethylsilyl)pentyl]benzyl]trimethylammonium iodide from [o-[l-(trimeth- ylsilyl)pentyl]benzyl]dimethylamine. 'H NMR (400 MHz, CD3CN) 5 7.718 and 7.540 (AA'BB'q, J=8.4 Hz, 4H), 7.555 and 7.131(AA'BB'q, /=8.0 Hz, 4H), 3.690 (s, 2H), 4.451 (s, 2H), 3.040 (sept, J=6.8 Hz, 2H), 2.794 (s, 3H), 1.460 (d, J=6.4 Hz, 6H), 1.370 (d, /=6.8 Hz, 6H), -0.017 (s, 9H); '^C NMR (100 MHz, CDsCN) 5 142.7,141.3,134.9, 133.3, 128.8, 127.1, 127.0,126.7, 63.9, 60.9,26.1, 17.5, 17.4, -2.5. 257 Oxygen Trapping of /^-Diphenoquinodimethane (5). An NMR tube was charged with (4-[4'-((trimethylsiIyI)methyl)phenyl]benzyl)diisopropylmethyIammoiiiuin iodide (13, 0.5 mg, 1.0 jimol) and 0.7 mL of CD3CN. A 'H NMR spectrum was taken of the quaternary ammonium salt 13. A solution of TBAF (6 mg, 17 mmol) in 0.2 mL of CD3CN was added to the NMR tube. .Aiter allo\\'ing the reaction solution to stand for 20 min, a 'H was taken. 'H NMR (400 MHz, CD.CN) 5 10.048 (s), 10.007 (s), 8.01 (d), 7.94 (d), 7.90 (d), 7.83 (d), 7.721 (d,>8.0 Hz), 7.64 (d), 7.59-7.52 (m), 7.49 (d), 7.41 (d), 7.29 (d), 4.566 (s), 4.541 (s), 4.481 (s), 2.9-2.8 (m), 2.067 (s). Oligomerization of p-Diphenoquinodimethane (5). An NMR tube was charged with 0.1 mL of a 0.012 M solution of (4-[4'-((trimethylsilyl)methyl)phenyl]benzyl)diiso- propylmethylammonium iodide (13. 1.2 |amol) in CD3CN and 0.60 mL of CD3CN. A solution of TBAF (7 mg, 20 jomol) in 0.3 mL of CD3CN was prepared in a tear-shaped flask. Both solutions were deoxygentated by repeated freeze-pump-diaw cycles then stored under argon. A 'H NIVIR spectrum was taken of the deoxygenated quaternary ammonium salt 13 solution. The NMR tube was returned to the glove bag. The TBAF solution was added to the NMR tube. The sample was protected from light. The NMR tube was periodically removed from the glove bag for analysts by 'H NMR spectroscopy. After 21 h the last 'H NMR spectrum was taken of the reaction solution. 'H NMR (400 MHz, CD3CN) 5 7.735 (d, J=8.0 Hz, 2.0H), 7.571 (d,/=8.0 Hz, 3.9H), 7.296 (d, 7=8.0 Hz, 2.1H), 7.158 (d, /=8.4 Hz, 3 AH), 6.960 (d, J=8.4 Hz, 3.1H), 4.463 (d, 1.6H), 2.38 (s, 2.2), 2.07 (s, 6.8H), 0.06 (s, 14.2H), -0.02 (s, 12.7H). 7: 'H NMR (400 MHz, CD3CN) 5 6.85 and 6.652 (AA-BB'q, J=8.0 Hz, 6.4H), 258 2.96 (s, 3.2H); (lit.'" 'H NMR (60 MHz, CDCl) r 7.04(s), 3.39 and 3.23 (AA'BB'q, 7=8.0 Hz)) The reaction mixture was extracted with methylene chloride and the combined organic layers were dried with Na2SO.:. The organic solvent was removed imder reduced pressure and the resulting residue was dissolved in CD3CN 'H NMR (400 MHz, CDjCN) 6 7.186 (d, y=8.4 Hz, 2.0H), 6.960 (d, 7=8.0 Hz, 1.9H), 6.786 (d, 7=8.4 Hz, 2.0H), 6.653 (d, 7=8.4 Hz, 2.0H), 2.948 (s, 1.9H). The tetrabutylammonium salts were not completely removed by the extraction process. References (1) For reviews on p-quinodimethanes see: (a) Errede, L. A.; Szwarc, M. Quart. Rev. 1958,12, 301. (b) Luzanov, A.V.; Vysotski, Y. B. Journal of Structural Chemistry 1976,17(6), 945. (c) Luzanov, A. V.; Pedash, Y. F. Tear. Eksp. Khim 1977, 12(5), 661. (Russian); Chem. Abstr. 1977, 88,21921. (d) Iwatsuki, S. Adv. Polym. Sci. 1984, 58 (Polym. React.), 93. (e) Mulvaney, J. E. Poly. Sci. Technol. 1984, 25 (New Monomers Polym.), 311. (f) Iwatsuki, S. "Polymerization and Polymers of Quinonoid Compounds" in The Chemistry of Quinoniod Compounds, Patai, S., Rappoport, Z., Eds.; John Wiley and Sons: New York; Vol. 2,1988; pp 1067-1111. (g) Yongjun, Y.; Matai, D.; Huixong, L.; Haiping, X.; Xumin, H. Gongneng Gaofenzi Xuebau 1994, 7(2), 195. (Chinese); Chem. Abstr. 1994,122,215228. (h) Itoh, T.; Iwatsuki, S. Macromol. Chem. Phys. 1997,198(7), 1997. (i) Greiner, A; Mang, S.; Schafer, O.; Simon, ^. Acta Polymer. 1997, 48, 1. (2) (a) Gorham, W. F. In Encyclopedia of Polymer Science and Technology, Gaylord, N. G., Bikales, N. Eds.;Wiley-Interscience: New York, 1971; Vol 15, pp 98-113. (b) 259 Niegish, W. D. In Encyclopedia of Polymer Science and Technology, Gaylord, N. G., Bikales, N. Eds.;Wiley-Interscience: New York, 1971; Vol 15, ppl 13-124. (c) Lee, S. M. in Kirk-Othmer Encyclopedia of Chemical Technology, 3"^ ed.; Wiley: New York 1983, Vol 24, pp 744-771. (d) Beach W. F.; Lee, C.; Bassett, D. R.; Austin, T. M.; Olson, R. In Encyclopedia of Polmer Science and Engineerins. 2"^* ed.; Wiley: New York, 1989; Vol. 17, p 990. (3) Szwarc, M. Nature 1947,160, 403. (4) See chapter three of this dissertation. (5) See chapter four of this dissertation. (6) Thiele, J.; Balhom, H. Ber. 1904, 37, 1463. (7) Montgomery, L. K.; Huffinan, J. C.; Jurczak, E. A.; Grendze, M. P. J. Am. Chem. Soc. 1986,108, 6004. (8) Chichibabin, A. E. Chem. Ber. 1907,40, 1810. (9) /7-Diphenoquinodimethane (5) is also known as 4,4'-dimethylenebicyclohex- ylidene-2,5,2',5'-tetraene. (10) Baudet, J./. Chim. Phys. Chim. Biol. 1911,68, 191. (11) (a) De Santana, O. L.; Da Gama, A. A. S. Chem. Phys. Lett. 1999,314, 508. (b) Guihery, N.; Maynau, D.; Malrieu, J-P. Chem. Phys. Lett. 1996,248, 199. (c) Hall, G. G.; Arimoto, S. Int. J. Quantum Chem. 1993, 45, 303. (12) (a) Haenel, M.; Staab, H. A. Tetrahedron Ierr.1970, 47,3585. (b) Staab, H. A.; Haenel, M. Chem. Ber. 1973,106, 2190. (13) (a) Fujita, T.; Yoshioka, T. J. Polym. Sci. Polym. Lett. Ed. 1980,18,549. (b) Fujita, T.; Yoshioka, T. J. Polym. Sci. Polym. Lett. Ed. 1981,19,1273. 260 (14) Gruber, J.; Li, R. W. C. European Polymer Journal 2000, 36, 923. (15) Ito, Y,; Miyata, S.; Nakatsuka, M.; Saegusa, T. J. Org. Chem. 1989, 54, 2953. (16) March, J. Advanced Organic Chemistry, John Wiley & Sons: New York. 1992, p 423. (17) Matsumoto, K.; Hashimoto, S.; Uchida, T.; Okamoto, T.; Otani, S. Chem. Ber. 1989, 122. 1357. (18) (a) Trahanovsky, W. S.; Fischer, D. R. J. Am. Chem Soc. 1990, 112, 4971. (b) Trahanovsky, W. S.; Arvidson, K. B. J. Org. Chem. 1996, 61, 9528. (19) Trahanovsky, W. S.; Chou, C.-H.; Fischer, D. R.; Gerstein, B. C. J. Am. Chem Soc. 1988,110, 6579. (20) Matsubara, H.; Seto, K.; Tahara, T.; Takahashi, S. Bull. Chem. Soc. Jpn. 1989. 62, 3896. (21) Huff. B, E.; Koenig, T. M.; Mitchell, D.; Staszak, M. A. Organic Sysntheses, Vol 75. Smith, A. B. Ed., 1997, 53. (22) Leung, M.-k. Ph.D. Dissertation, Iowa State University, Ames, 1991,130. (23) Ito, Y.; Nakatsuka, M.; Saegusa, T. J. Am. Chem Soc. 1982, 104, 7609. 261 Appenduc 262 /7-TolyIboronic Acid (14) was prepared by the method of Matsubara-° but on a 13.1 molar scale. A 25-mL tear-shaped flask fitted with a condenser was charged with magnesium (0.342 g, 114 mmol) and 5 mLof dry THF. A solution of p-bromotoluene (2.24 g, 13.1 mmol) in 10 mL of dry THF was added slowly through the condenser to maintain a reflux. The mixture was heated to reflux for an additional 30 min and then allowed to cool to room temperature. In a 50-ml flask, a solution of trimethoxyborane (2.04 g, 2.2 mL, 19.4 mmol) in 10 mL of dry THF was cooled to -78°C. The Grignard reagent solution was transferred slowly to the chilled solution. The reaction mixture was stirred for 1 h at low temperature. While still cool, 10 mL of 10% H,SO^ was added and die mixture was allowed to warm to room temperature. The mixture was filtered and was extracted with ether. The ether com bined layers was washed with water then dried with sodium sulfate. The ether was removed under reduced pressures. The resulting white solid was washed with hexane and water to yield acid 14 (1.15 g, 84.5 mmol, 65 %). 'H NMR (300 MHz, CDCy 5 8.136 and 7.322 (AA'BB'q, y=7.8Hz, 4H), 2.454 (s, 3H); mp 247.5-250.3 °C (lit.-° mp 245-247 =C). Methyl 4'-MethyI-4-biphenyIcarboxylate (10) was prepared on 8.5 mmol scale using a method similar to the method used by HufP' for the synthesis of unsymmetrical biaryls using a modified Suztiki cross-coupling: 4-biphenyIcarboxaldehyde. A 100-mL three-necked round-bottom flask with a stir bar, condenser, and argon gas inlet was charged with 1.150 g of/7-tolylboronic acid (14, 8.46 mmol), 1.91 g of methyl p-bromobenzoate (15, 8.87 mmol) and 20 mL of 1-propanol. The mixture was stirred until the solids dissolved. To the solution was added 6 mg of Pd(OAc), (0.025 mmol), 20 mg of PPh. (0.076 mmol), and 1 g Na,CO, (10.1 mmol) in 8 mL H,0. The mixture was heated to reflux for I h. Water (10 mL) was added to the mixture while it was still hot. The reaction vessel was opened to the air and stirred overnight. Ethyl acetate (20 mL) was added to the reaction mixture and the layers were separated. The aqueous layer was extracted twice with 10 mL of ethyl acetate. The combined ethyl acetate layers was washed with 5% sodium bicarbonate solution then with 263 brine. The organic solution was transferred to an Erlenmeyer flask. Carbon (0.8 g) was added to the flask and the mixture was stirred for 30 min. The mixture was filtered through Florisil on a Celite pad with additional ethyl acetate to rinse the pad. The solvent was re moved under reduced pressure to yield a crude solid product which was recrystallized fi-om hexanes and methanol. (1.180 g, 5.22 mmol, 61%) 'H NMR (400 MHz, CDCl,) S 8.071 and 7.627 (AA'BB'q, /=8.8 Hz, 4H), 7.510 and 7.256(AA'BB'q, /=8.8 Hz, 4H), 3.918 (s, 3H), 2.389 (s, 3H); NMR (100 MHz, CDCl.) 5 167.1, 145.6, 138.2, 137.1, 130.1, 129.7, 128.6,127.1, 126.8, 52.1 ,21.2. iV,iV-Diisopropyl-4-[4'-((trimethylsilyl)methyl)phenyl]benzamide (11) was pre pared by a method similar to the method used by Leung-- to prepare methyl 2-[(trimethylsil- yl)methyl]benzoate. The preparation was intended to prepare methyl 4-[4'-((trimeth- ylsilyl)methyl)phenyl]benzoate (12). A solution of LDA was prepared at -78°C with diisopropylamine (1.5 mL, 10.4 mmol), «-butyllithium in hexanes (4.15 mL, 2.5 M, 10.4 mmol) in 10 mL of THF. A solution of methyl 4'-methyl-4-biphenylcarboxylate (10, 1.18 g, 5.2 mmol) and chlorotrimethylsilane (0.7 mL, 5.5 mmol) in 10 mL of dry THF was added to the cold LDA solution over 10 min. After the solution was stirred for 30 min, the reaction was quenched with die addition of water. Once the reaction mixture had wanned to room temperature, it was extracted with ether. The combined ether extracts was dried with Na,SO^ and die solvent was removed under reduced pressure to yield a crude oily product. Flash colimm chromatography on silica gel (elution with 4:1 hexanes-ether) to afford amide 11 (408 mg, 1.1 mmol, 21%) as a white solid: 'H NMR (400 MHz, CDCy 5 7.569 and 7.345 (AA'BB'q, J=8 Hz, 4H), 7.441 and 7.051 (AA'BB'q, /=8 Hz, 4H), 3.92 (b), 3.466 (b), 2.104 (s, 2H), 1.475 (b), 1.205 (b), -0.002 (s, 9H); IR (neat, cm*') 2958, 1628,1436,1337; GC/MS m/z (relative intensity) 442 (6), 441 (14), 370 (6), 369 (13), 368 (25), 367 (7) M*, 366 (9), 264 270 (7), 269 (22), 268 (51), 267 (100), 266 (17), 265 (18), 264 (10), 263 (11), 262 (6), 251 (6), 188 (5), 165 (25). (4-[4'-((TrimethylsilyI)methyl)phenyl]benzyI)diisopropyImethylammonium Iodide (13) was prepared by a method similar to the method used by Ito^ to prepare [o-[l-(trimethylsilyl)pentyl]benzyI]trimediylammoiiium iodide from [c>-[l-(trimeth- ylsilyl)pentyl]benzyl]dimethylamiiie. A 5-mL tear-shaped flask with a stir bar, condenser, and argon gas inlet was charged with MiV-diisopropyl-4-[4'-((trimediylsilyl)methyl)phen- yl]benzlamine (16, 50 mg, 0.14 mmol), 1 mL of acetonitrile, and methyl iodide (0.2 mL, 0.456 g, 3.2 mmol). The reaction solution was stirred for 1 h, heated to reflux for 1 h, and allowed to cool to room temperature. Pentane was added to the reaction solution, and the precipitate was collected. The crude solid was recrystallized from acetone-pentane to yield the quaternary ammonium salt 13 (10 mg, 20 jimol, 14%). 'H NMR (400 MHz, CD.CN) 5 7.718 and 7.540 (AA'BB'q, >8.4 Hz, 4H), 7.555 and 7.131(AA'BB'q, J=8.0 Hz, 4H), 3.690 (s, 2H), 4.451 (s, 2H), 3.040 (sept, /=6.8 Hz, 2H), 2.794 (s, 3H), 1.460 (d, J=6.4 Hz, 6H), 1.370 (d, J=6.8 Hz, 6H), -0.017 (s, 9H); '^C NMR (100 MHz, CD.CN) 5 142.7, 141.3,134.9. 133.3. 128.8, 127.1,127.0,126.7,63.9, 60.9,26.1, 17.5, 17.4, -2.5. cn CN IT) CN U3 •SJ- CNJ ro o lo ro ro OvI oo oo t~- lO UiON JLJl RO CN| CD CD — >- t.s f.e •.» «.o v.o 1.0 o.i Figure A-1. 'I I NMR spcctmin (300 MHz, CDCI,) of/j-tolylboronic acid (14). (S: chloroform) r>a»moa3»o^iAOtn^oi m i-l I I l-LtakUAl yj to On ON A -A/w_JU_ JL. V' s- f-ri I I I I I I I I I T I I I I I I I'M I 'I I f I I 'I I I I I I I I I I I • I I I I TT-p ' M ' I ' 11.0 10.0 9.0 8.0 7.0 6.0 r.. 0 1.0 0.0 piMn Figure A-2. 'H NMR spectrum (400 MHz, CDClj) of methyl 4'-methyl-4-biphcnylcarboxylatc (10). (A: ethyl acetatc, S: chlo roform) o XJL ii»wWWw'M«»»l»i|>»W*tl»l«H> Figure A-3. "C NMR speclmin (100 MHz, CDCl^) of inclhyl 4'-incthyl-4-biphcnylcarboxylatc (10). (S: chloroform) Ul U> • - > tl I Ul ui •- • r--1/» '•I If I »•> '•» lO 'r nt '» ri f.j c» lO ON OO -.1.^ I I ri I rrri |r f-r-)- rpri-?-i-|-rr i r| rrriiiii(1111(11 I lyri > I( 111 I^T-n-i ("n I I| I I I I (tti Vrf I I I I |i I M I 11,0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-4. 'H NMR spectrum (400 MHz, (UX'lj) of A', A'-cliisopropyl-4-[4'-((triincthylsilyl)metliyl)plieiiyl]benzamide (II). (S: chloroform) 100 \ 98 96 94 92 CO in cn OJ 90 ru cn 88 in ai(O C7>2 m 86 O) •^1 w-i • m rvjtn in CM CM cn rs 84 m ID 82 \sSi's « I I 000 3500 3000 2500 2000 1500 1000 Wavenumbers les=4 Scans=16 •5. [rared spectrum of A',A^-diisopropyl-4-[4'-({trimcthylsilyl)mcthyI)phcnyl]ben/amide (II). Scan No: 1852 Rotentlon Tine: 23:09 RIC: 171384 Hass Range: 45 - 444 ft Peaks: 174 Base Pk: 267 loniz: 1240 us Int: 19012 100.08x - 19012 100X 2G7 INT- 165 368 441 251 86 108 135 324 412 1 11'1»I' •'Vh M11' IW1111114 • pI •' I' n 100 150 200 250 350 400 450 Figure A-6. Mass spectrum (El) of A',A/-diisopropyl-4-[4'-((lrimclhylsilyl)niethyl)phenyl]bcn/,amide (11). •—io»— m o r-. r-c.5r0»^0**-«3c> cn m fo ^ ^ CO iO »/> *0 o» r— CM »— oo>r-.40^rMO^ u> tn oo »0 K» ro v-OOOOOO*- u u ^0»O*O»O»^rO»OCN| L- i-j il 1 ^ ^ «-v ^ k, ^ s J v. to •o u> •V o o o 9) (O Ti"^"i I I I I I r I I I "IT1^1 I I I I I I I I I I I I I I I I I I I I I I I I I I f I I'l'I 11 f 1111111111111 1 1 1 1 f 1 T 1 1 1 1 1 1 1 1 1 1 1 1 1 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3 . 0 2.0 1.0 0 . 0 ppm Figure A-7. '11 NMR spectrum (400 MHz, CD^CIJ of A/,/V-cliisopropyl-4-(4'-((lrimelhylsilyl)melhyl)phcnyl]benzylaminc (16). (S: mclliylenc chloride) in lO r-. Ut CN O ocor^rn cn to ro if> •— lO rN o to o r-« Oi O r^ooif*-> <71 CO r~. lO ^ ^ r«) r«^l <*.J iN 1^# tv SS\I Ir^ s 1 —1 ' T 1 , , , , r- —I—•—I—•—I— —I—•—I—I 1—'—I >—I—'—I ' 1 •—I '—I —I—•—r I ' 220 200 180 160 140 120 100 60 60 40 20 0 ppm Figure A-8. '^C NMR spectrum (100 MHz, CD,Clj) of/V,A'-cliisopropyl-4-f4'-((lrimethylsilyl)methyl)phenyl]ben7,ylaminc (16). (S; methylene chloride) tt>^rNr-rsto--*'>om^cn •- to f-- O r- •«romi->i/iii->crtrsiooa3r>joo»-cocjit--.m «>*fN4»-oou>tOin»n^K>c«* in o» r». io ^ m^ooo»'>r«J«"»^ — •—»ouiP^u»rNO»-fN r>»r«Nr^r*.r^a>*/>*oir>M>»o*o •— »— «r «o CO so (O CO »—•—»— •-»- ljjojLL XU«!sfJ "n] i-o OJ w JUUL A M I I I I i"i I I I I'fi J i"i I r I i f"f "f'l'r'rfi| i r r ff"Iti| i T i r i Tn i i i ]i r"i i pr i i| i i-i i| i i i i| "i i-i i |i i fT-r| i TT-p M I'' ' M ' ' pri I I I I < I 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-9. 'H NMR spectrum (400 MHz, CD^CN) of (4-[4'-((trimethylsilyl)metliyl)phenyl]benzyl)cliisopropylmctliylammon- ium iodide (13). (S: acetonilrile, W: water) r- u>«— ro tO I II I I H I n 1 ~i 1 1 1 1 1 1 1 1 1 1 1 1 I 1 r—' I ' 1 ' 1 1 1 ' 1 ' 1 ' i 1 1~' 1 ' 1 • 1 T 1 [ • 1 r—I 1 ( 220 200 lao 160 140 120 100 80 60 40 20 0 ppm Figure A-10. '^C NMR spectrum (100 MHz, CD^CN) of 4-l4'-((trimethylsilyl)methyl)plienyl]benxyl)diisopropylmcthylammon- ium iodide (13). (S: acclonilrile) »•- r- »•- r * r - f-. r • f - r- r - r- M V' T i-j Ul li r MhkxL i UWl t iTyTTT I J n"f"fprT-rf| i r? i-j i t i i | i rn-f-ri n | i in | i i |-|-pn*T i | i i if]'i rrii i i i »j i n i-v' * ' •n"( I I rri Tf rrTTTi-n-] i-i i i-frri 11,0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 piim Figure A-ll. 'H NMR spectrum (400 MHz, CD^CN) of />-dibenzoquinoclimcthanc (5) products in non-cleoxygenatcd acetonitrilc after 20 niin. (S: acetonitrilc,'I': TBAF) U) f- (J a) uci •- •- »*i a> »•- uj »•) V o cw #v •— V »- o o o> crt o* «a r- L I -'•iSSM 1 l// \ to -J ON 10.0 Figure A-12. Enlargement of Figure A-11 from 10.5- 4 ppm. 'H NMR spcctrum (400 MHz, CDjCN) of /^-clibcnzoquinodi- mctlianc (5) products in non-dcoxygenatcd acctonitriie after 20 min. O lU CJ C.1 Ot r^4 M tf• 0< (O I- !-• I- -4 Figure A-13. EnlargcmciU of Figure A-11 from 8.5- 7 ppin. 'II NMR spectrum (400 MHz, CDjCN) of /i-dibcn/.oquinodi- inethane (5) products in non-deoxygenated acetonitrile after 20 min. (C: common product that appears in both experiments) O9tt/>0<«4 »>.!«. »0 u> »o rs4 ^^ Ot o> r» r^ r-o to •« r-- r-- r~" lO »*"» uj u» a> »f> 14^ 1" I' --J 00 i ^L,—.L— ilJ Lull JL/u. r? r I I I I I I I I I f I r I *1 I r I I I I I I I I I I rnI] 11.0 10.0 9.0 B.O 7.0 6.0 5.0 1. 0 0.0 ppm Figure A-14. 'M NMR speclrum (400 MHz, CDjCN) of/j-dibcnzociuinoclinielhiinc (5) products in dcoxygcnaled acclonitrilc after 2 li. (7 is a compound number given in the text, C: common product that appears in both cx|)criments, S; acetoni- Irile.T: TBAF) Hi cr> «« o ta o« r>. •'» e^4 *t\ a> r- r- «A «0 X* «A >0 \F 1/ C (.' fim VWhJ t/H IIHM 7.9 7.4 6.9 6.4 ppm Figure A-15. Enlargemcnl of Figure A-13 from 8 6 ppm. 'M NMR spcclrum (400 MHz, CD,CN) of/j-dibenzoquinoclimclhanc (5) products in deoxygenated acetonitrilc allcr 2 li. (7 is a compountl niimbcr given in the text, C; common product that appears in both experiments) 13 13 13 13 Before addition iLi X. I r r c (• lO CO After 10 min •J* O l' r • v After 2 h Jill ' WW wij 1 r frf T'i i rr Ii I r|-rr|-rT i f •| i i ri rrrri ?-] rT rrj-rrrrr'^'''' I • | i < ' » | I rr| ( ( i i |i i i i | i i i f | i i i i |• i I'ryi ( I i |i t • • t ( i ' n"|"l t ' •| t'l i i J i i t 11.0 10.0 9.0 8.0 7.0 6.0 5.0 4.0 3.0 2.0 1.0 0.0 ppm Figure A-16. 'H NMR spectrum (400 MHz, CD^CN) of reaction progress of/^-dibcnzoquinodimethanc (5) in deoxygenatcd acetonitrile. (7 and 13 are compound numbers given in tiie text, C: common product that appears in both experi ments, S: acetonitrile, T: TBAl-') 13 13 13 Before addition C C After 10 min Vw4«i»i UL After 2 h J-- ..,—I — 1— r 1 I 1 "T ' I I •" I 7.9 7.7 7.5 7.3 7.1 6.9 6.7 ppm Figure A-17. Enlargement of Figure A-16 from 8 - 6.5 ppm. 'M NMR spectrum (400 Mil/., CDjCN) of reaction progress of /)-dibenzoquinodimethane (5)in deoxygenatcd {icetonitrile. (7 and 13 arc compound numbcns given in the text, C: common product that appears in both experiments) •O O WI O O .O ro ( »- »- r- 0« 0» »- »•>.»•« U» t ui lo io u3 >n lo t ru r- ^ r- • s to oo to •l' r vv M _JiZ ll .^aJL. t •ft 1-m i I" I I r- ri I I I'l f I ] T ri-i [ I I'n j'Ti"1 11.0 10.0 9.0 B.O v.o 6.0 5.0 4.0 i.O 2.0 1.0 0.0 ppm Figure A-18. '11 NMR spectrum (400 MH/., CD^CN) of methylene chloride extract of /;-dibenzoquinodinicthanc (5) products in deoxygeiiated acetonitrile. (7 is a compound number given in the text, M: methylene chloride, S: acetonitrile, T: TBAF, W: water) tooknc»ou>o«/>ror4 CT>oor~>r>»/>oi«r--w>-* oio»r~-r-.f-~«oio <- r> to tA to u> jm r I t'I f• f•> T"! J I I "f'rf pn I I I riTfj I f I I pi T I i |'i I 11.0 10.0 9.0 6.0 6.0 b.O 4.0 3.0 ppm Figure A-19. Enlargement of Figure A-18. 'H NMR spectrum (400 MHz, CD,CN) ofmethylene chloride extract of/;-dibcnzo- quinodimethane (5) products in deoxygenated acetonitrile. (7 is a compound number given in the text, M: methyl ene chloride, S: acetonitrile, T: TBAF, W: water) to Ui to > M M> \l I-J CO 4^ V B.4 7.9 7.4 6.9 6.4 ppm Figure A-20. Enlargement of Figure A-18 from 8.5 - 6 ppm. 'H NMR spectrum (400 MHz, CDjCN) of methylene chloride extract of/j-dibenzoquinodiniethane (5) products in deoxygenated acetonitrile. (7 is a compound number given in the text.) 285 GENERAL CONCLUSION The research presented in this dissertation demonstrates that molecules generally considered highly reactive can be prepared in such a manner that they are relatively stable at room temperature. Once prepared, these compounds can be observed at room temperatiure by spectroscopic means including 'H NMR spectroscopy. Their relative stability also allows their chemistry to be studied and mechanisms to be examined. The first chapter of the dissertation describes the preparation of the smallest possible cross-conjugated polyene, 3-methylene-l,4-pentadiene, by flash vacuum pyrolysis (FVP). The triene was characterized by 'H, '^C, and heteronuclear chemical shift correlation (HETCOR) NMR spectroscopy. The Diels-Alder reaction of the cross-conjugated triene and methyl acrylate under mild conditions produces methyl 4-vinyl-3-cyclohexenecarboxylate, the 'para' 1:1 adduct, as the major product and methyl 3-vinyl-3-cycIohexenecarboxylate. the 'meta' 1:1 adduct, as the minor product. The 'para' regioselectivity observed in this reaction is consistent with frontier molecular orbital theory. Under the mild conditions used for this Diels-Alder reaction, only traces of 2:1 adducts are produced. It can be concluded that there is a large difference in the reactivity toward dienophiles of the initial triene and the 1:1 adducts. An area of further work is the issue of the regioselectivity of the addition of a second dienophile to form the 2:1 adducts. Chapter two is a literature review of simple p-QDM's. It describes the relative reactivity, a number of methods of generating by pyrolylic and non-pyrolylic methods, and spectral observation of simple p-QDM's. Chapters three and four describe the preparation by fluoride induced elimination of trimethylsilyl acetate and the room temperature characterization by 'H NMR spectroscopy of 286 five reactive p-QDM's: p-xylylene, a-methyl-p-xylylene, 2,6-dimethyl-p-xylylene, a-phenyl-p-xylyiene, and a,a-diphenyl-/7-xylylene. The '"C NMR spectrum of/7-xylylene was observed for the first time. Trimers of three /j-QDM's, p-xylylene, a-methyl-/7-xylylene, and 2,6-dimethyl-p-xylylene, were observed which is strong evidence that they dimerize via a diinencal dirauical in a stepwise mechanisni. Rate constants were detennined for the decomposition of/j-xylylene, a-methyl-p-xylylene, a-phenyl-/?-xylylene, and a,a-diphenyI-/7-xylyIene. The long-term kinetic study ofp-xylylene found that it primarily decomposes by a second-order process like dimerization. The other kinetic studies, including the short-term study of p-xylylene, found that both first- and second-order decomposition was occurring. A probable explanation is that polymerization, a first-order process, and dimerization, a second-order process, are occurring at an appreciable rate. The a,a-diphenyl derivative was found to be the most reactive of the series followed by the a-phenyl derivative, p-xylylene, and the a-methyl derivative. Chapter five discusses the attempted preparation ofp-diphenoquinodimethane by fluoride induced elimination. The biphenyl-based /?-QDM is believed to be form based on the similarities of its products and that of other p-QDM. When exposed to oxygen, the product's 'H NMR spectrum with signals firom aldehydes and peroxides was similar to that obtained with p-xylylene. With carefiil avoidance of oxygen in the solution, evidence was obtained for [2.2]-(4,4')-biphenylophane, which is analogous to the [2.2]cyclophane found in the oligomerization of p-xylylene. 287 ACKNOWLEDGEMENTS This work was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Di\'ision of Chemical Sciences, under Contract W-7405-ENG-82.