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Durham E-Theses Durham E-Theses The synthesis and reactions of some uorinated polycyclic polyenes Preston, William Edward How to cite: Preston, William Edward (1972) The synthesis and reactions of some uorinated polycyclic polyenes, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/8872/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk THE SYNTHESIS AND REACTIONS OF SOME FLUORBTATED FOLYCYCLIC POLYENES A thesis submitted for the degree of Doctor of Philosophy by WILLIAM EDWARD PRESTON, B.Sc. (Van Mildert College) UNIVERSITY OF DURHAM 1972 2 2 NOV SECTION USRA ABSTRACT The Synthesis and Reactions of Some Fluorinated Polycyclic Polyenes Perfluorocyclohexa-l,3-diene gave the expected 1,4-adducts with cyclo- hexene, cyclopentene, 1H,2H-octafluorocyclohexene, 1H,2H-hexafluorocyclopentene and lH,2H-tetrafluorocyclobutene; reaction with 1H,2H-tetrafluorocyclobutene also yielded two 2,2-difluorovinyldecafluorobicyclo[4,2,0]oct-2-enes and the 2 4 dimer 3,3,4,4,7,7,8,8-octafluorotricyclo[3,3,0,0 ' ]octane. Dehydrofluorination of the adducts from 1H,2H-octafluorocyclohexene and 1H,2H-hexafluorocyclopentene 2 7 gave the trienes, perfluorotricyclo[6,2,2,0 ' ]dodeca-2,6,9-triene and 2 6 perfluorotricyclo[5,2,2,0 ' ]undeca-2,5,8-triene respectively. 2 6 Perfluorotricyclo[5j2j2,0 ' ]undeca-2,5,8-triene reacted as a diene in Diels-Alder reactions with ethylene, propyne and but-2-yne. The 1,4-adducts with alkynes could be pyrolysed selectively to either polyfluorobenzobicyclo- [2,2,2]octa-2,5-dienes or 2,3-disubstituted hexafluoronaphthalenes. 2 7 Irradiation of perfluorotricyclo[6,2,2,0 ' ]dodeca-2,6,9-triene and 2 6 perfluorotricyclo[5,2,2,0 ' ]undeca-2,5,8-triene in the vapour phase with UV 2 7 5 7 radiation resulted in their isomerisation to perfluorotetracyclo[6,2,2,0 5 0 ' ]- 2 6 dodeca-2,9-dienes and perfluorotricyclo[5,2,2,0 ' ]undeca-2,3,8-triene respectively. Arguments presented support the latter isomerisation being a photochemical 1,5-sigmatropic migration of a fluorine atom. Vacuum pyrolysis of 2 6 perfluorotricyclo[5,2,2,0 ' ]undeca-2,5,8-triene provides perfluoroindene in good yield. Irradiation of 2H-heptafluorocyclohexa-1,3-diene in the vapour phase with UV radiation yielded 2H-heptafluorobicyclo[2,2,0]hex-2-ene, the isomerisation proceeding in the reverse direction on pyrolysis; the photo- isomer was of the same order of dienophilicity as perfluorobicyclo[2,2,0]- hex-2-ene towards furan. r 2 2 NOV 1972 SECTION Perfluoroindene reacted readily with the nucleophiles sodium borohydride, sodium methoxide and lithium methyl replacing initially one of the vinylic fluorines in the five-membered ring. Its olefinic character was evident from the formation of a mixture of hydrazones on reaction with hydrazine hydrate and the isolation of l,l,3,4j5,6,7-heptafluoroindan-2-one from its reaction with oleum; intermediate unstable compounds formed in the latter transformation suggest that the initial stage in the reaction is the formation of the p sultone of perfluoroindene. ACKNOWLEDGEMENTS I would like to thank Sr. W.J. Feast for his continued help and advice and Professor W.K.R. Musgrave for his interest and encouragement during the supervision of this work, I an also indebted to Dr. D.T. Clark and co-workers for helpful discussions and for recording the X- ray photoelectron spectra. Assistance from the technical and laboratory staff is greatly appreciated; in particular thanks are due to Mr. D. Hunter for some practical assistance. Finally I am grateful to the Imperial Smelting Corporation for the award of a maintenance grant* MEMORANDUM The work in this thesis was carried out in the Chemistry Laboratories of the University of Durham between September 19^9 and September 1972. This work has not been submitted for any other degree and is the original work of the author except where acknowledged by reference. Part of this v/ork has been the subject of the following publications. 1. Die Is-Alder Reactions of Polyfluorooyclohexa-l,3-dienes. Part V, Addition of Cycloalkenes to Octafluorocyclohexa-1,3-diene and Dehydrofluorination of Some of the Adducts by W.J. Feast, W.K.R. Musgrave and W.E. Preston, J. Chem. Soo. Perkin I. 1972, 1527. 2. Diels-Alder Reactions of Polyfluorocyclohexa-1,3-dienes. Part VI, Reactions of Dodecafluorotricyclo [5,2,2,0 ' Jundeca-2,5,8- triene with Ethylene and Alkynes. A Synthesis of Polyfluoro tricyclo[6,2,2,02,7]dodeoa-2,4,6,9-tetraenes and 2,3-Di- substituted Hexafluoronaphthalenes by W.J. Feast, W.K.R. Musgrave and W.E. Preston, J. Chem. Soo.. Perkin I. 1972, 1830. 3. The Photochemical Isomerization of Some Fluorinated Polycycliopolyenes. A Possible Photochemical 1,5-Sigmatropic Migration of a Fluorine Atom by W.J. Feast and W.E. Preston, Tetrahedron. 1972, 28, 2805. 2 6 4. Charge Distributions in Dodecafluorotricyclo 1.5,2,2,0 ' ]undeca-2,5,8- triene and Tetradecafluorotricyclo[6,2,2,02»^.ldodeca-2,6,9-triene As Determined by ESCA by D.B. Adams, D.T. Clark, W.J. Feast, W.K.R. Musgrave and W.E. Preston, J. Fluorine Chemistry. 1972, 2, 207. Application of ESCA to Structural Problems in Organic Chemistry; the Orientation of Nucleophilic Substitution in Perfluoroindene by D.B. Adams, D.T. Clark, W.J. Peast, W.K.R. Musgrave and W.E. Preston, Nature Physical Science, in the press. CONTENTS Page Abstract Acknowle dgemonts Memorandum CHAPTER 1. Addition of Cycloalkenes to Octafluorocyclohexa-1.5- diene and Dehydrofluorination of Some of the Adduots Introduction - The Die Is-Alder Reaction 1.1 The Stereochemistry and Mechanism of the Diels-Alder Reaction 1 1.2 Factors Governing the Rates of Diels-Alder Reactions 6 1.3 "Electron-poor" Dienes 11 1.4 Fluorinated Acyclic Dienes 13 1.5 Fluorinated Cyclopentadienes 16 1.6 Fluorinated Cyclohexa-l,3-dienes 21 1.7 Cyc-loolefins as Dienophiles 27 Dehydrofluorination of Fluorinated Cyclic Compounds 36 1.8 Methods of Dehydrofluorination 37 1.9 Mechanisms of Dehydrofluorination 39 Discussion 1.10 Diels-Alder Reactions of Perfluorocyclohexa-1,3- diene with Cyclic Olefins 43 1.11 Dehydrofluorination of 2H,7H-hexadecafluorotricyclo- [6,2,2,02»7Jdodec-4-ene Cl) and 2H,6H-tetradeca- fluorotricyclo[5,2,2,02»°]undec-8-ene (II) and the attempted dehydrofluorination of 2H,5H-dodecafluoro- tricycloC4,2,2,02»5jdec-7-ene (III) 57 Experimental 1.12 Reagents 62 1.13 Preparation of lH,2H-hexafluorocyclopentene 62 1.14 Cycloadditions of 0ctafluorocyclohexa-l,3-diene (XII) with Cycloalkenes with lH,2H-octafluorocyclohexene 63 with lH,2H-hexafluorocyclopentene 63 with lH,2H-tetrafluorocyclobutene 65 with cyclohexene 69 with cyclopehtene 69 1.15 Dimerisation of lH,2H-tetrafluorocyclobutene 69 1.16 Dehydrofluorination of the Diels-^Alder Adducts (a) Dehydrofluorination of 2H,6H-tetradecafluoro- tricyclo[5,2,2,02»6jundec-8-ene (II) 69 (b) Dehydrofluorination of 2H,7H-hexadecafluoro- tricyclo L'6,-2,2,02»7]dodec-9-ene 71 (c) Attempted dehydrofluorination of 2H,5H-dodeca- fluorotricyclok,2,2,02>5JcLec-7-ene (m) 71 1.17 Retrodiene reactions of the Diels-Alder adducts 72 1.18 Dehydrofluorination of lH,6H-octafluorocyclohexene 73 CHAPTER 2. Diels-Alder Reactions of Dodecafluorotrioyolofe.2.2.0 * Jundeca- 2.5.8-triene with Ethylene and Alkynes. A Synthesis of Poly- fluoroben20bicyclo[2.2.2]octa-2.5-dienes and 2.3-Disubstituted Hexafluoronaphthalenes Introduction 2.1 The Reverse Diels-Alder Reaction 74 2.2 The Synthesis of Polyfluoronaphthalenes 88 Discussion 2.3 Diels-Alder Reactions of Dodecafluorotricyclo 1*5,2,2,0 ' J undeca-2,5,8-triene with Ethylene and Alkynes 99 2.4 Pyrolysis of the Diels-Alder Adducts of Dodecafluoro- tricyclol5,2,2,02,6]unaeoa_2,5,8-triene with alkynes. A. Synthesis of Polyfluorobenzobicyclo t2,2,2locta- 2-5-dienes and 2,3-Disubstituted Hexafluoronaphthalenes 106 Experime ntal 2 6 2.5 Diels-Alder Reactions of Perfluorotricyclo[5,2,2,0 » ] undeca-2,5,8-triene (X) (a) with ethylene 115 Cb) with propyne 115 (c) with but-2-yne 117 2.6 Vacuum Pyrolyses (a) Compound (XDQ 118 (b) Compounds (XV) and (XVl) 119 (c) Compound (XVIIl) 119 (d) Compound (XX) 119 2.7 Attempted reaction of 0H.p-methyldecafluorobenzobicyclo- fc,2.2joct-2-ene (XIX) with tetrafluoroethylene 119 3 g 2 7 2.8 Heating 4H,5-methyl-dodeca£fluo^otetracyclo[6,2,2,l;,, 0 ' J tridec-2,4,9-trienes (XV) and (XVl) 120 CHAPTER 3. The Photochemical Isomerisation of Tetradecafluorotricyolo [6.2.2. Q2 > 7] dp deoa-2.6.9-triene. do decaf luorotricyclo [5.2.2. Q2»6j undeca-2.5y8-triener- and 2H-heptafluorooyclohexa-l.3-diene. Some Reactions of the Photoisomers including a Synthesis of Perfluoroindene Introduction 3.1 Unsensitized Photoisomerisations of CycloaHca-l,3-dienes 121 3.2 Irradiation of Cyclopentadienes 123 3.3 Irradiation of Cyclohexa-l,3-dienes 125 3.4 Irradiation of Cycloalka-1,3-dienes containing Larger Rings 134 3.5 Thermal Stabilities of Bicyclo L"n,2,oJalkenes 137 3.6 Sigmatropic Rearrangements 138 3.7 Selection
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