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PART 2: INVESTIGATION OF GENERATION AND THE FATE OF 2- PYRROLYLMETHYLENES

DISSERTATION

Presented in Partial Fulfillment of the Requirements for the Degree Doctor of

Philosophy in the Graduate School of The Ohio State University

Christopher J. Woltermann

The Ohio State University 1996

Dissertation Committee: Approved by

Professor Harold Shechter, Adviser

Professor David Hart

Professor John Swenton Department of Chemistry UMI Number: 9631007

This microform edition is protected against unauthorized copying under Title 17, United States Code.

UMI 300 North Zeeb Road Ann Arbor, MI 48103 ABSTRACT

Nitration of acetylides (I) with various nitrating agents (N 02BF4, N20 5, N20 4>

Me3Si0N 02, n-PrON02) typically results in efficient single electron transfer to yield the corresponding acetylene radicals (2). The acetylene radicals (2) couple with the parent acetylides (1) to give butadiynes upon further electron transfer and loss of metal ion or abstract hydrogen from solvents to afford the parent acetylenes. Attempts to trap acetylene radicals 2 with nitrogen dioxide to yield 1-nitroacetylenes (1) are described.

Dinitroacetylene (3) is an unknown but potentially important compound because of its expected high energy and density. Attempts at synthesis of dinitroacetylene (3) by dinitration of 1,2-disubstituted acetylenes at various temperatures and with varied nitrating agents have been investigated.

Nucleophilic addition-elimination and rearrangement of phenylethynyl(phenyl)iodonium tosylate (4) by nitrite ion does not yield 1- nitroacetylenes but does give phenylethynyl nitrite (5) which tautomerizes to nitroso(phenyl)ketene (6). Ethynyl nitrites are previously unknown and their behavior is investigated. Study of nitrosoketenes proves that they undergo novel intramolecular

[2+2] cycloadditions with subsequent loss of carbon dioxide to yield nitriles. Preparation of dinitroacetylene (3) by Retro Diels-Alder reactions was investigated. Temperatures greater than 250 °C are needed for cycloreversion of 9,10- dihydro- 1 l,12-dinitro-9,10-ethenoanthracene(7). At such high temperatures, 3 does not survive but decomposes to nitrogen and carbon dioxide. A study of more electron-rich anthracene adducts for the retro Diels-Alder reaction to give dinitroacetylene (3) at lower temperatures is described. Synthesis of anthracene adducts related to 7 with electron-donating groups in the 9 and 10 positions by reaction of tetranitroethylene with 9,10-disubstituted anthracenes followed by removal of N20 4 was unsuccessful.

Oxidations of cyanogen-N,N’-dioxide (10) to nitro(nitroso)acetylene (11) and dinitroacetylene (3) were investigated. Various oxidants (03, bis-

(trimethylsilyl)peroxide, KMn04, M n02, Cr03, Ag20, PDC and H20 2) were employed for this study but none were successful.

Utilization of the known nitro(trimethylsilyl)acetylene (8) to prepare new 1- nitroacetylenes by substitution of the trimethylsilyl group is discussed. Removal of the trimethylsilyl group by fluoride ion in an attempt to synthesize nitroacetylene anion (9) results in resinous material even when in the presence of excess electrophiles.

Electrophilic addition-elimination on 8 with N 02BF4 does not yield dinitroacetylene

(3).

in Study has been made of the behavior of l-methyl-2-pyrrolylmethyIene (12) at

high temperatures (250-350 °C). The sodium salt of l-methyl-2-pyrrolecarboxaldehyde tosylhydrazone (13) was pyrolized to produce [2-(l -methyl)pyrrolyl]diazomethane (14) as an intermediate with subsequent loss of nitrogen to yield l-methyl-2- pyrrolylmethylene (12). Sodium salt 13 was pyrolyzed to determine whether or not 12 would ring open to E/Z-ynenoneimines (15). In all instances, methylene 12 dimerizes to E/Z-l,2-di(l-methyl-2-methylpyrrolyl)ethylenes (16) and/or reacts with 14 to yield bis-(l-methylpyrrolyl)ketazine (17). 2-Pyrrolylmethylene (18) does not form its dimer but gives a high molecular weight compound which may result from polymerization of cyclopentadienoneimine (19) or 2-methylene-2H-pyrrole (20).

IV Dedicated to my wife and daughter

v ACKNOWLEDGMENTS

I wish to thank those whose friendship and support made the Ph.D. program at

Ohio State enjoyable; especially Paul Boxrud, Peter Dalidowitz, Dan Repicz, Tony

Skufca, Eric Vendel and Michael Waterman. I would also like to thank those who helped me to become oriented when first joining the Shechter group: Nash Mathur,

Larry Yet and Stephan Klump,

Professor Shechter has been particularly helpful to me as a graduate student.

He has taught me much about chemistry, writing and public speaking. I have truly enjoyed the many conversations we have shared.

I would not have been able to complete the Ph.D. program without the support from my parents and especially from my wife, Kathy, and daughter, Angela.

VI VITA

September 24, 1968 ...... Bom - Cincinnati, Ohio

1990...... B.S. Chemistry - University of Dayton

1988-1990 Production Chemist - Exciton Inc.

1990-1993...... Graduate Teaching Associate, The Ohio State University

1993-1996...... Research Associate, The Ohio State University

FIELD OF STUDY

Major Field; Chemistry

Studies in Organic Chemistry TABLE OF CONTENTS

Abstract...... ii

Dedication ...... v

Acknowledgments ...... vi

Vita...... vii

List of Figures ...... x

PART 1 Statement of Problem ...... 1

Chapters:

1. Historical Information ...... 4

Preparation of 1-Nitroacetylenes ...... 4

Reactions of 1-Nitroacetylenes ...... 13

2, Results and Discussion ...... 18

Introduction ...... 18

Nitration of Acetylides ...... 19

Nucleophilic Addition-Elimination ...... 40

Retro Diels-Alder Reactions ...... 51

Oxidation of Cyanogen-N,N'-dioxide ...... 58 Reactions of Nitro(trimethylsi!yl)acetylene ...... 60

Summary: Part 1...... 63

3. Experimental Section ...... 70

PART 2 Statement of Problem ...... 122

Chapters:

4. Historical Information ...... 124

5. Results and Discussion ...... 131

6. Experimental Section ...... 140

List of References ...... 147

Appendices:

A: Part 1: Miscellaneous Reactions ...... 154

B: Part 1: FTIR, 'Hand ,3C NMR Spectra ...... 158

C: Part 2: lH and nC NMR Spectra ...... 164

IX LIST OF FIGURES

FIGURE PAGE

1. Horizontal Pyrolysis Apparatus ...... 110

2. FTIR of 1-Nitro-l,4,6-triphenyl-1,2,3-hexatrien-5-yne (42)...... 159

3. 'HNMR(200MHz) of l-Nitro-l,4,6-triphenyl-l,2,3-hexatrien-5-yne (42) .. 160

4. ,JCNMR(50MHz) of 1-Nitro-l,4,6-triphenyl- 1,2,3-hexatrien-5-yne(42).. ..161

5. FTIR of 9,10-Dihydro-9,10-dimethoxy-l 1,11,12,12-tetranitro- 9,10-ethanoanthracene (97d) ...... 162

6. lH NMR (200 MHz) of 9,10-Dihydro-9,10-dimethoxy -11,11,12,12-tetranitro-9,10-ethanoanthracene (97d)...... 163

7. ’H NMR (200 MFlz) of 2-Pyrrolecarboxaldehyde Tosylhydrazone (36, R - H)...... 165

8. I3C NMR (50 MHz) of 2-Pyrrolecarboxaldehyde Tosylhydrazone (36, R = H )...... 166

9. 'H NMR Spectrum of 7-[[(l-Methyl-2-pyrrol-2-yl)methylene]amino-7- azabicyc!o[4.1 .OJheptane (40)...... 167 PART 1

STATEMENT OF PROBLEM

1-Nitroacetylenes (1) have been sought by chemists for use in synthesis because of the strong electronegativity of their nitro groups and their abilities to be easily converted to other functional derivatives. 1-Nitroacetylenes are excellent Michael acceptors and dienophiles and therefore are of special interest for preparing explosives and propellants of high energies and densities.

R—C = C —N 0 2 1

R = n-Pr, i-Pr, t-Bu, Ph, R'^Si, R'3Sn

Only a few 1-nitroacetylenes (1) have been synthesized. The methods for their preparation include elimination, electrophilic addition-elimination and nucleophilic addition-elimination. These methods are limited because they work for just a few acetylenes. Only alkyl (R = n-Pr, i-Pr, t-Bu), phenyl (R = Ph), silyl (R = RaSi) and stannyl (R = R3Sn) nitroacetylenes have been reported and will be discussed in the

Historical Information Section. None of the known synthetic methods can be used to prepare all of the above 1-nitroacetylenes.

1 A general method for preparing 1-nitroacetylenes will be valuable. A convenient, mild synthesis could provide new 1-nitroacetylenes (2) with important uses

z —c = c —n o 2 2

Z = O 2 N, ON, F 2 N, R2 N, ArS02, RO, NC, OCN, NCO, RCO, Halide in synthesis and as high-energy materials. Of special interest is dinitroacetylene (3).

Dinitroacetylene balances perfectly to give two equivalents of carbon dioxide and one equivalent of nitrogen on decomposition (Equation 1). This balance makes

0 2N—C=C—N02 ------► 2 CO2 + N2 (1) 3 dinitroacetylene of great interest as a high-energy, high-density explosive. The stability of dinitroacetylene is uncertain and could therefore limit its usefulness.

Dinitroacetylene may also be valuable as a synthetic intermediate for other sought-after high-energy materials such as hexanitrobenzene (4, Equation 2), octanitrocyclooctatetraene (5) and octanitrocubane (6, Equation 3).

2 o2n ^ L , (2) * ^ 0 2N—Cs=C—n o 2 n o 2 4

o 2n o 2n

(3) n o 2 n o 2

The purpose of the present research is to investigate new methods for synthesis of 1-nitroacetylenes. Special emphasis is placed on dinitroacetylene (3). The results of these studies will be discussed.

3 PART 1

CHAPTER 1

HISTORICAL INFORMATION

Preparation of 1-Nitroacetylenes

The earliest reported synthesis of a 1-nitroacetylene dates to 1903 when

Wieland treated cinnimaldehyde with oxides of nitrogen to obtain a yellow crystalline

solid in low yield. Elemental analysis and molecular weight determination showed the

molecular formula of this solid to be CgH4N20 4. Wieland postulated that the compound

is nitro(p-nitrophenyl)acetylene.' This structural assignment was later found to be

erroneous.

Novikov et. al. also reported synthesis of nitro(p-nitrophenyl)acetylene in 1960

from 2-nitrostyrene (7) and dinitrogen tetroxide.2 Efforts to reproduce Novikov’s experiments failed. Further study showed the product to be is l-nitro-2-

1 Wieland, H. Ann. Chem. 1903, 328t 154.

2 Novikov, S.S.; Belikov, V.M.; Den'yanenko, V.F.; Lapshina, L.V. Izv. Akad. Nauk SSSR, Otd. Khim. Nauk, 1960, 1295

4 azachromone(3-nitro-4H-l,2-benzoxazin-4-one) (8) (Equation 4).3 Benzoxazin-4-one

8 is also believed to be the compound isolated by Wieland.

N°2 + N20 4 (4)

7 8

An early report of synthesis of a 1-nitroacetylene came from Loevenich et. al. in 1930.4 Their method involves simple dehydrobromination of 1-bromo-l-nitroalkenes

(9) with diethylamine in refluxing ether (Equation 5). The 1-nitroacetylenes thus obtained are red, pungent, thick oils that could not be purified due to deflagration upon attempted vacuum distillation. The validities of these syntheses were later questioned by Viehe and Jager3 because the results could not be reproduced.

3 a) Jager, V. Nitroacetylenes. Synthesis and Reactions of a New Class of Compounds. Das Doktorgrad Naturwiss, Fak. Friedrich-Alexander-Univ. Erlangen- Numberg, 1970. (b) Bishop, E.G., Brady, O L. J. Chem. Soc., 1926, 810. (c) Liegler, E.; Nolken, E. M onatsh ., 1962, 92, 1062.

4 a) Loevenich, J.; Koch, J.; Puchnat, U. Chem. Ber., 1930, 63, 636, (b) Loevenich, J.; Gerber, H. Chem. Ber., 1930, 63, 1707.

5 H I r ^ c ^ c ^ N ° 2 + Et2NH ------► R—C^C-N()2 (5)

Br i

R = Et (la), Pr (lb), Ph (lc)

Viehe and Jaeger reported the first generally accepted syntheses of 1-

nitroacetylenes in 1969.3 Their syntheses of 1-nitroacetylenes involve treatment of a

terminal acetylene (10) with dinitrogen tetroxide and iodine in E^O to yield E/Z-2-

iodo-l-nitroalkenes (11). The product isomers were then dehydroiodinated as gases

over hot potassium hydroxide (Equation 6).

H N20 4 r Distill, 0.1 mm Hg R—C = C —H — -— ► '"'C %NOi R—C = C —NO? (6) i2 y 2 k o h 100 oc 2 10 I ,

R = t-Bu (Id, 94%), i-Pr (lc, 74%), n-Pr (If, 28%)

Iodides work better than chlorides in these eliminations. Potassium hydroxide is superior to tertiary amines, sodium acetate in DMF, silver oxide in ether, and potassium t-butoxide for the dehydrohalogenations. t-Butyl(nitro)acetylene (Id) is a pale yellow-green lachrymatory liquid melting at -3 °C and boiling at 55 °C @ 15 torr.

6 The product, Id, is one o f the most stable 1-nitroacetylenes known with a half life of

2-3 days at room temperature and does not detonate by shock or glowing wire.

In 1963, Robson and Tedder5 synthesized the first t-nitrosoacetylenes (12) as

part of a route to alkynyldiazonium salts. These nitrosoacetylenes were prepared by

reactions of metal acetylides (13) with nitrosyl chloride (Equation 7). Mercury

-78 oc R—C=C-M + NOC1 -—-*• R-CsC-NO + MCI (7) CH2 CI2 13 12

R = l-Bu (12a), n-Bu (12b)

acetylides are far superior to lithium or magnesium acetylides for nitrosation. Metal

phenylacetylides (13, R = Ph) do not give nitrosoacetylenes. Nitrosoacetylenes are

much less stable than their nitro counterparts and are detected chemically and spectroscopically in solution at low temperatures. Upon warming to room temperature, the nitrosoacetylenes rearrange to acyl cyanides (14) (Equation 8).

5 a) Robson, E.; Tedder, J.M. Proc. Chem. Soc., 1963, 13; (b) Robson, E.; Tedder, J.M.; Woodcock, D.J. J Chem. Soc. (C), 1968, 1324.

7 1-Nitrosoacetylenes can be oxidized to 1-nitroacetylenes.6 The first step of these

syntheses involves modification of Robson and Tedder's method for preparing 1-

nitrosoacetylenes. They found that trialkylstannylacetylenes (15), when treated with

dinitrogen tetroxide, form 1-nitrosoacetylenes (12a, Equation 9) that are oxidized at

low temperature to 1-nitroacetylenes. The best oxidant for conversion of the nitroso group to a nitro group is 40% hydrogen peroxide (Equation 10).

N2 O4 R—C = C —Sn(CH3)3 ------► R—C = C —NO (9) - (CH3)3S n 0 N 0 2 15 12a

H2 O2 (40%) — ----- ► R—C=C—N02 (10) -60 °C Id

Petrov and co-workers used a similar method to prepare nitro(phenyl)acetylene

(lc) and nitro(trimethylsilyl)acetylene (16).7 Apparently, this method involves an electrophilic addition-elimination mechanism (Equation 11) and not a radical mechanism leading directly to nitroacetylenes.

6 Jager, V.; Motte, J.B.; Viehe, H.G. Chimia 1975, 29, 516.

7 Petrov, A.A.; Zavgorodnii, V S.; Rail', K.B.; Vil’davskaya, A.I.; Bogoradovskii, E.T. Inventor’s Certificate 401,136, 1971; Zhumal Obshchei Khimii, 1978, 48, 943 (Eng. trans. p. 865),

8 Rv ^NO R —c - c Sn(CH3 )3 + NO@N o f - ►

15 N0 3 6 V ^

- (C H 3)3Sn0N 02 H20 2 — -----— ------► R—C = C —NO — R—C=C—N02 (11)

12 1

Subsequently, it was discovered that trialkylstannylacetylenes (15) react with dinitrogen pentoxide in ether or nitronium tetrafluoroborate in methylene chloride to give 1-nitroacetylenes in yields up to 40 and 70%, respectively (Equation 12).6

A one-step synthesis of 1-nitroacetylenes from readily available starting materials was reported in 1986.8 This method also involves electrophilic addition- elimination of acetylenes with nitronium ions. Nitronium tetrafluoroborate and various nitronium salts are purchasable and stable solids unlike dinitrogen pentoxide and nitronium fluoride. Trialkylsilylacetylenes (16) are used in place of trialkylstannylacetylenes because of their lower costs and toxicities and because

8 a) Schmitt, R.J.; Bedford, C D. Synthesis, 1986, 493; (b) Schmitt, R.J.; Bottaro, J.C.; Malhotra, R.; Bedford, C D. J. Org. Chem., 1987, 52, 2294.

9 formation of strong Si-F bonds (130 kcal/mol)9 facilitates the reactions (Equation 13).

The electrophilic addition-elimination mechanism in Equation 12 is substantiated by stabilization of carbocations beta to silicon atoms. Like alkyl(nitro)acetylenes, nitro(silyl)acetylenes are more stable when they are sterically hindered. Of the silylacetylenes studied, only bis-(trialkylsilyl)acetylenes provide 1-nitroacetylenes in appreciable yields. Nitro(triisopropylsilyl)acetylene (lh) is the most stable nitro(silyl)acetylene known in that it can be kept solution at room temperature for weeks with no decomposition

9 McMillen, D.F.; Golden, D.M. Annu. Rev. Phys. Chem. 1982, 493.

10 R N 0 2 R - C ^ C - S i M e , + N 0 2Y ------► S ^ S s i M e , 16 ^

R ,N 0 2 R C=C N02 + Me3SiF + BF3 + C=C (13) %SiMe3 1 ,(m * inor) i

Y = BF4, PF6, A sF6

R % YIELD R % YIELD

(CH^Si (Ig) 70 CFLj (Ik) trace i-Pi^CHj^Si (Ih) 34 t-Bu (Id) 0 t-Bu(CIL) Si (li) 59 Ph (lc) Jj (i-Pr)3Si (lj) 57 (cH3>)Si-(CH 2)j—C=C— (..) 0

Yamabe and Yasutake report preparation of nitro(phenyl)acetylene (lc) by treatment of chloro(pheny!)acetylene (17) with sodium nitrite in DMSO (Equation

14).10 Nitro(phenyl)acety)ene (lc) was isolated by column chromatography and then gas chromatography. The structure of lc was determined by infrared and lH NMR spectroscopy. However, the infrared data reported for lc differ significantly from those

10 Yamabe, K,; Yasutake, A. Sasebo Kogyo Koto Senmon Gakko Kenkyu Hokoku, 1979, 16 , 63; Chem. Abstr. 1980, 93, 185856,

11 claimed by Petrov. Petrov states stretches for the nitro group to be 1528, 1354, and

1341 cm'1 and a peak for the carbon-carbon triple bond at 2215 cm'1. Yamabe reports the nitro stretch at 1300 and 560 cm'1 and the carbon-carbon triple bond stretch at 2240 cm '1,

DMSO Ph— C s C - C l + NaN02 -■- » Ph—C = C _ N0 2 + NaCI (14) 70 5d 17 lc

12 Reactions of 1-Nitroacetylenes

1-Nitroacetylenes are extremely reactive. Most decompose on storage and are thermally unstable. Upon standing or heating, 1-nitroacetylenes decompose to complex products. For t-butyl(nitro)acetylene (Id), greater than twenty decomposition products are formed in one month.11

The great reactivities of 1-nitroacetylenes are due to the strong electronegative effects of the nitro groups. Reactions of 1-nitroacetylenes with hydrogen and platinum oxide or lithium aluminum hydride result in reduction of the triple bonds and the nitro groups to give saturated amines (18) (Equation 15). Bromine adds to 1-nitroacetylenes

R—C^C—N02 RCH2CH2NH2 (15)

1 18 to yield 1,2-dibromo-l-nitroalkenes (19, Equation 16) almost quantitatively. Similarly,

1-nitroacetylenes are hydrochlorinated under anhydrous conditions to cis-2-chloro-l- nitroalkenes (20, Equation 17). Hydrolysis of the acetylenes by water and THF gives a-nitroketones (21) (Equation 18). In contrast to most acetylenes, halogenation, hydrohalogenation and hydration of 1-nitroacetylenes are believed to begin with nucleophilic attack rather than electrophilic attack.

” Rail', K B , Vil’davskaya, A.I.; Petrov, A.A. Uspekhi Khimii , 1975, 44, 744; English Translation: Russian Chemical Reviews, 1975, 44 (4), 373.

13 ■V NO (16) CHC1

HC1 (17) n o 2 20

R—C—CH2N 0 2 (18) THF

Due to the polarizing effects of their nitro groups, 1-nitroacetylenes undergo

Michael additions of nucleophiles. Additions of alcohols and secondary amines to t- butyl(nitro)acetylene (Id) thus result in rapid formation of the corresponding cis- nitrovinylethers (22) and cis-nitroenamines (23), respectively (Equation 19).

n o 2 I t-Bu— C = C —N 0 2 + Z—H ------► Z ^ c ^ C- h ( I9) I D Id t-Bu 22,23

Z = MeO- (22a), E tO -(22b), Et2N - (23a), piperidine- (23b), P hN H -(23c)

14 Additions of enamines to 1-nitroacetylenes are of particular interest.12 An initial

Michael adduct (24) undergoes ring expansion which, upon hydrolysis, forms Ot- nitroketone 25 (Equation 20). Ynamines also add to 1-nitroacetylenes to yield

t-Bu t-Bu ,n o 2 QN' 76% (20)

“ ' 6 24 25 intermediate nitrile oxides (26) which react with another equivalent of the nitroacetylene via 3+2 dipolar cycloaddition resulting in isoxazoles 27 (Equation 21).

26 27

Electron-deficient alkenes and alkynes undergo Diels Alder reactions more readily than their unsubstituted counterparts. 1-Nitroacetylenes are no exceptions. Jager and Viehe showed that Id forms the Diels Alder adduct 28 with cyclopentadiene

u Jager, V.; Viehe, H.G. Angew. Chem. Int. Ed. Engl., 1970, 9, 795.

15 quantitatively in two hours (Equation 22).13 Nitro(silyl)acetylenes also undergo Diels

Alder reactions with cyclopentadiene as well as with 1,3-cyclohexadiene.14

t-Bu, 20 °C | Id + (22) O 2 h

1-Nitroacetylenes have also beep studied as dienophiles for 1,3-dipolar

cycloadditions. Such 3+2 cycloaddition reactions have been carried out with

diazomethane and with trimethylsilyl azide to yield 3-nitro-4-trialkylsilylpyrazoles (29,

Equation 23) and 4-nitro-5-trialkylsilyltriazoles (30, Equation 24), respectively.15

13 Jager, V.; Viehe, H G Angew. Chem. Int. Ed Engl., 1969, 8, 273.

14 Schmitt, R.J.; Bottaro, J.C.; Malhotra, R.; Bedford, C.D. J. Org. Chem., 1987, 52, 2294.

15 Schmitt, R.J.; Bottaro, J.C. Chem. Abstr. 1989, v.IIl, 97148a.

16 Me3Si n o 2 c h 2n 2 (23)

& I H Me3Si— C=C—N 02 29

lg 0 2N M e3SiN3 (24) Me3Si N I SiMe3

While the chemistry of 1-nitroacetylenes is fairly well established, there are still relatively few 1-nitroacetylenes. This is somewhat surprising in light of the fact that acetylenes with most other functional groups can be prepared readily by general methods. There are many examples of acetylenes with cyano, amino, halide, ester, aldehyde, ether, sulphone and other functional groups directly attached to the sp hybridized carbons of acetylenes.'6

16 Viehe, H.G. Chemistry of Acetylenes , Marce/Dekker Inc., New York, 1969.

17 PART 1

CHAPTER 2

RESULTS AND DISCUSSION

The limited knowledge about 1-nitroacetylenes (1) has been summarized in the section on Historical Information. There are no general methods for preparing 1- nitroacetylenes (1) and thus only a few are known. An effective, mild synthesis of 1- nitroacetylenes (1) will be valuable. The present research focuses on discovery of new methods for generating known (1) and unknown (2) l-nitroacetylenes. Special emphasis is placed on synthesis of dinitroacetytene (3). Dmitroacetylene (3) is expected to be one of the most difficult nitroacetylenes to prepare and one of the most interesting.

Various synthetic approaches to 1-nitroacetylenes (I) and dinitroacetylene (3) and their results are discussed in the following section.

18 NITRATION OF ACETYLIPES

A straightforward, simple approach for preparing 1-nitroacetylenes is to deprotonate a terminal acetylene ( 10) with a strong metallic base and treat the resulting metal acetylide (13) with a source of nitronium ion or an effective nitrating agent

(Equation 25). By this method, virtually any terminal acetylene that forms a

RH i^IO R—C=C—H + M-B - ■ »» R—C=C—M R—C=C—N02 (25) -M® 10 13 1

nucleophilic reagent might be nitrated at low temperature and in dilute solution. Under such conditions, a large variety of 1-nitroacetylenes could easily be produced. Such a mild approach would be especially advantageous for preparing relatively unstable 1- nitroacetylenes. In theory, dinitroacetylene (3) could be produced by dinitration of readily prepared dimetalloacetylenes and appropriate diderivatized acetylenes (Equation

26).

19 M - C ^ c - M + 2 Ncfy° ~2MY» 0 2N —C ^ € —N0 2 (26)

M = MejSi, n-BuHg, BrMg, Ca, Ag, Li, n-Bu,N

Y°= NOj, N 03, Cl, I, BF4, Me^SiO

The first attempts at nitrations of terminal acetylenes were performed on 1,2-

disubstituted acetylenes. Possible dinitration of bis-(trimethylsilyl)acetylene with 2

equivalents of nitronium tetrafluoroborate (N 0 2BF4) results only in resinous material.

Upon use of 1 equivalent of N 0 2BF4, nitro(trimethyIsilyl)acetylene could be prepared

as has been previously reported .17 Reactions of bis-(n-butylmercuric)acetylene with

N 0 2BF4 or a mixture of dinitrogen tetroxide and iodine (N 20 4/I2) afford unidentified

high molecular weight organomercury compounds. Attempted nitrations of bis-(n-

butylmercuric)acetylene with N20 4/I2 give diiodoacetylene in lowyield and unidentified

organomercurials. Disilver acetylide and N 0 2BF4 result only in polar, unidentifiable

products. Reaction of bis-(bromomagnesium)acetylide with N 0 2BF4 gives gaseous

products whereas nitration with nitryl chloride N0 2C1 followed by addition of

cyclopentadiene or 1,7-diphenylisobenzofuran in an attempt to trap dinitroacetylene (3)

affords an intractable residue. Calcium carbide (CaC2) does not react with N 20 4/12 or

N2Os. When bis-(tetrabutylammonium)acetylide is treated with N 0 2BF4 in dioxane ai

17 Schmitt, R.J.; Bottaro, J.-C.; Malhotra, R.; Bedford, C D. J. Org. Chem. 1987, 52, 2294.

20 0 °C, reaction occurs but neither dinitroacetylene nor mononitroacetylene could be

isolated, detected or trapped by anthracene. Dilithium acetylide and N 0 2BF4 in dioxane

yield LiBF 4 and products that FTIR shows that nitro and acetylene compounds are not

present.

As has been summarized, different acetyl ides, nitrating agents, solvents and

temperatures were employed in attempts to synthesize dinitroacetylene (3), In most

experiments, no identifiable organic products could be isolated. In attempts to nitrate

terminal acetylenes, a study was initiated of nitration of various phenylacetylides (32).

The advantages of investigating phenylacetylides are twofold. First, nitro(phenyl)acetylene (lc), a known 1-nitroacetylene, would be obtained rather than

3 which may be formed and subsequently destroyed. The second advantage is, if the reactions do not produce 1-nitroacetylenes, products will be obtained which should be identifiable.

A thorough study was then made of possible nitration of phenylacetylides (32) under a broad range of conditions (Equation 27). A series of phenylacetylides was investigated ranging from lithium phenylacetylide (32, M = Li), a strong nucleophile, to much less reactive and more covalent reagents such as mercury (32, M = Hg) and stannyl (32, M = R 3Sn) phenylacetylenes. The nitrating agents ranged from N 0 2BF4 and N 2Os to N 20 4 and then various covalent nitrates (Equation 27). Reaction temperatures between -100 - 0 °C, various addition methods, concentrations, reaction

21 times, equivalents of reagents and solvents were investigated. None of the experiments produced nitro(phenyl)acetylene (lc) in significant yields.

Ph—c^c—m + NO2®Y0 ~ M Y » Ph— C = C —N 02 (27)

32 lc

M = Li, Na, Cu, MgBr, ZnX, R 3Sn, Hg, CuLi 2

N 0 2Y = N 0 2BF4, N2Os, N204, p-To1S03N02, Me 3Si0 N0 2, n-PrON0 2

Solvent = Et 20, THF, 1,4-Dioxane, CH 3CN, CCI4, C6H 14

Of all reactions studied, addition of N 20 4 (1 equiv.) to lithium phenylacetyIide gives the cleanest reaction. At -78 °C in Et 20, diphenylbutadiene (33) is obtained in up to 80% yield after short reaction times. Longer reaction times lead to lower yields and cruder products. There are no products formed from Michael additions of phenylacetylides to nitro(phenyl)acety!ene. Inverse addition, higher temperatures and excess reagents also result in 33 although in lower yield and purity.

The mechanism for formation of diyne 33 is believed to be an electron transfer, oxidative coupling process. Rather than the expected nitration of the phenylacetylide anion (34), an electron is transferred from 34 to the nitronium cation. This single electron transfer results in a stable nitrogen dioxide radical and phenyl acetylene radical

(35) (Equation 28). Another equivalent of anion 34 Michael adds to radical 35 to afford radical anion 36 (Equation 29). Radical anion 36 is resonance stablized.

2 2 Nitrogen dioxide radical or nitronium cation can then oxidize radical anion 36 to give

diyne 33 and nitrite anion (Equation 30). Nitrite ion is, in fact, co-product in these reactions.

Ph—cs=ce + ©N02 ------*■ Ph— C ^ C ■ ♦ -N 02 (28) 54 35

36 - *N02 ------► Ph— C = C —C ^ C —Ph ♦ © N 02 (30) 33

Oxidative coupling of acetylenes is certainly not new. Conversions of copper acetylides to butadiynes by air was first reported in 1869. 18 Since then there has been much discussion about the mechanism of these oxidations .19 Of general agreement is that electron transfer to oxygen takes place to give acetylene radicals. Many authors postulate that the acetylene radicals then dimerize to butadiynes. Dimerization of two radicals in solution, however, seems improbable to this author. Much more likely is that an acetylide (34) adds to an acetylene radical (35) to give a radical anion (36) as in Equation 29. As will be discussed later, this mechanism is supported in the present

18 Glaser, C. Chem. Ber. 1869, 2, 422

19 For a review of acetylene coupling mechanisms see: Eglinton, G.; McCrae, W. Adv. Org. Chem. 1963, 4, 225.

23 research by the observations that poorly nucleophilic metal acetylides (32, M = ZnCl,

ZnBr, MgBr, Hg, R 3Sn) give little (20% when M = ZnCl or ZnBr) or no butadiynes.

In attempted nitrations of 32 (M = ZnCl, ZnBr, MgBr, Hg, R 3Sn), phenylacetylene (37) is produced in up to 100% yield.

Apparently, 37 arises by abstraction of hydrogen from the organic solvent by radical 35 (Equation 31). Hydrogen abstractions from C-H bonds by alkyl radicals are well known. Such reactions are even more prevalent with vinyl radicals .20 An acetylene radical is sp hybridized and therefore highly electron deficient and thus expected to abstract hydrogen better than its sp 3 or sp 2 counterparts.

Ph—C=C* + H—Sol ------► Ph—C = C —H +■ -Sot (31)

35 37

In the present experiments with phenylacetylides, the phenyl group might have greatly facilitated electron transfer. In efforts to test the generality of such electron transfer reactions, the behaviors of other lithium acetylides were studied. Addition of

N20 4 (1 equiv.) to lithium trimethylsilylacetylide (13, M = Li, R = Me3Si) in Et20 at

-78 °C yields bis-(trimethylsilyl)butadiyne (38, 38%) and trimethylsilylacetylene (39,

25%) (Equation 32). Similarly, reactions of N 20 4 with 1 -lithium-1 -pentyne (13, M =

Li, R = C3H7) give 4,6-decadiyne (40, 30%) and 1-pentyne (41, 57%) (Equation 33).

20Capetla, L,; Montevecchi, PC.; Navacchia, M.L. J, Org. Chem. 1995, 60, 7424.

24 Me3Si—C=C—Li V MejSi—C ^!—CsC—SiMej +■ Me3Si—CsC—H (32) -70 13 (M = Li, R = Me3Si) 38 (38%) 39 <25%>

n-Pr—C=C—Li 78 oc n_Pr—C=C-CsC-Pr-n ♦ n-Pr—C^C—H (33)

13 (M = Li, R = C3H7) 40 (30%) 41 (57%)

Under these same conditions, lithium phenylacetylide is converted to diphenylbutadiyne

(33) in 80% yield. The lower yields for diynes 38 and 40 as compared to 33 may be due to the greater selectivity of phenyl acetylene radical as compared to trimethylsilylethynyl and 1-pentynyl radicals. Addition of phenylacetylide to phenyl acetylene radical is favored. Of further note is that lithium ethynyl(phenyl)sulphone and lithium ethoxyacetylene do not yield butadiynes upon addition of N 20 4 in Et20 at -78 °C. Lithium ethynyl(phenyl)sulphone and N 20 4 give ethynyl(phenyl)sulphone in 95% yield. Lithium ethynyl(phenyl)acetylene is insoluble in Et 20, possibly making the coupling reaction impossible. Lithium ethynyl(phenyl)sulphone decomposes readily in THF even at -78 °C (See Appendix A).

A further result while attempting nitration of lithium phenylacetylide by N 20 4 in THF is of interest. Addition of N 20 4 to lithium phenylacetylide at -78 °C in THF affords butadiyne 33 in 61% yield along with 1-nitro-l ,4,6-triphenyl-l,2,3-hexatrien-5- yne (42, 26%). Hexatriene 42 is not produced under other conditions. The structure of

42 is assigned by ‘H NMR, l3C NMR, FTIR and mass specrtroscopy (high resolution).

25 The novel product is only the second example of a nitrocumulene .21 Cumulene 42

presumably results from 1,4-addition of phenylacetylene radical (35) to

diphenylbutadiyne (33) and trapping of 43 by N 0 2 (Equation 34).

z Ph THF C=C— C=C ► Ph

*N0 2 ° 2n v ^ C = C = C = C (34)

Ph 42 (26%) Ph

As summarized earlier, attempted nitrations of phenylethynylzinc chloride and bromide yield phenylacetylene along with diphenylbutadiyne (33). Phenylethynylzinc iodide gives a different result. Reaction of phenylethynylzinc iodide (32, M = Znl) in

THF with N20 4 yields iodo(phenyl)acetylene (44, 74%) and 33 (17%) (Equation 35),

THF Ph— C = C —Znl + N20 4 » Ph—C^C'—I + 33 (35) -78 32 (M - Znl) 44(74%) (17%)

Apparently in 32 (M = Znl), iodide ion is oxidized more readily by N 20 4 than is the phenylacetylide moiety. Indeed, the reaction solution is colored initially by iodine. The

2' Schlubach, H.H.; Rott, W. Ann. Chem. 1955, 594, 59,

26 iodine then reacts with 13 (M = ZnONO) as in Equation 36 or with 32 (M = Znl) to give 44. Phenylacetylene (33) is presumably produced as proposed previously after generation of the phenylacetylene radical (35).

2 Ph—C=C—Zn-I + N20 4 - r 2 Ph—C=C—Zn-ONO + U

► 44 * Zn(ONO)I (36)

A notable difference in the attempted nitration of copper (I) phenylacetylide

(32, M = Cu) with N20 4 is the absence of 37 as a product. Phenylacetylene (37) might not be formed because 32 (M = Cu) may exist as a tight complex (45) or related polymer in which copper is bonded to two phenylacetylene moieties. Removal of an electron from anionic copper by the nitronium reagent will yield N0 2 and di(phenylacetylene)copper radical (46) which loses cuprous ion and then rearranges intramolecularly to copper diphenylbutadiyne radical (47). Radical 47 is then oxidized by N 02 to diphenylbutadiyne (33) and nitrite ion (Equation 37). The intramolecular reorganization of 46 to 47 is equivalent to addition of phenylacetylide ion (34) to phenylacetylene radical (35) as postulated previously.

27 45 46 (37)

NO, * u Ph—C=C—C=C—Ph Ph— C = C —C = C —Ph * I Cu 33 47

Study was then made of possible nitration of sodium phenylacetylide (32, M

= Na), an acetylide presumably more anionic than those studied previously. Reaction

of sodium phenylacetylide gives different results than for lithium or copper

phenylacetylide. Diphenylbutadiyne (33) is not found. TLC shows the product to be

complicated; GC/MS/IR reveals that the principle component is 3-benzoyl-5-

phenylisoxazole (48). There is spectroscopic (FTIR) evidence for dinitrostyrene (49)

in the crude product but it cannot be isolated because of decomposition.

Chromatography results in isolation of phenylacetylene (37, 16% yield) and isoxazole

48 (23% yield). Isoxazole 48 is assigned by 'H NMR, nC NMR, FTIR, mass

spectroscopy (high resolution) and comparison of melting point to that reported in the

literature.12 There is loss, upon chromatography, of a large percentage of the crude mixture.

22 a) Hassner, A.; L'abbe, G.; Miller, M.J. J Am . Chem . Soc. 1971, 93, 981. (b) Tamura, Y.; Sumoto, K.; Matsushima, H.; Taniguchi, H.; Ikeda, M. J. Org. Chem. 1973, 38, 4324.

28 Formation of phenylacetylene 37 presumably arises by electron transfer from

32 (M = Na) and then hydrogen abstraction by the phenylacetylene radical (35).

Production of isoxazole 48 is complicated, possibly by the extensive sequence in

Equations 38-42. Isoxazole 48 might thus be formed by addition of N 20 4 to

phenylacetylene (37) to give l-nitrito-2-nitrostyrene (50) which then rearranges to 51

and then to ketonitrooxime 52. Loss of nitrous acid (HN02) from 52 yields benzoyl

nitrile oxide 53 which then undergoes [3+2] dipolar cycloaddition with phenylacetylene

(37) to form 48. 1,2-Dinitrostyrene also arises from addition of N 20 4 to phenylacetylene (37). The sequence is predicated, in part, by the fact that sodium phenylacetylide is quite insoluble in the nitrating reaction medium and thus the phenylacetylene (37) generated undergoes preferential addition of N 20 4. Initial experiments failed to show 1,2-dinitrostyrene (49) because it does not survive column or gas chromatography (thus explaining the loss of weight during purification).

29 Ph—C=C-Na + N20 4 ------► 35 Ph—C ^ C - H (38) - *bol 32 (M = Na) 37

N 0 2 n o 2 Ph Ph ,c. N2^4, ,0 I H CX H I (39) n o 2 ONO

49 50

-OH n o 2 N Ph. J —H 50 Ph. J ! . (40) X n o 2 1 * > II o 51 52

Ph' (42)

O Ph

30 Effort has been made to confirm some of the mechanisms proposed in

Equations 38-42. Wieland and Bluemich have reported previously that reaction of N 20 4 and phenylacetylene (37) yields 1,2-dinitrostyrene (49) as a singular product .23 The stereochemistry of 49 is unassigned. In the present experiments, reactions of N 20 4 with phenylacetylene in Et20/ltgroin at -78 °C give 1,2-dinitrostyrene (49, 42%) and isoxazole 48 (25%). 1,2-Dinitrostyrene (49) could not be isolated but was identified as a reaction product by FTIR analysis. Isoxazole 48 is identical with that described previously from reactions of sodium phenylacetylide and N 20 4. The gross behavior of

N20 4 and phenylacetylene (37) is thus similar to that of Equation 39.

Reaction of potassium phenylacetylide (32, M = K) with N 20 4 in Et,0 at -78

°C gives similar results to those for reaction of sodium phenylacetylide and N 20 4.

Initially, phenylacetylene (32) is formed with subsequent partial conversion to isoxazole 48. A noticeable difference between reactions of potassium rather than sodium acetylides is formation of benzonitrile (55) and benzoyl cyanide (54) as minor products. Possible mechanisms for formation of these products will be discussed later.

All attempts at nitration of lithium, copper, magnesium, zinc or sodium acetylides by reaction with one equivalent of N 20 4 have resulted in electron transfer to yield the phenylacetylene radical (35), Effort was then made to take advantage of formation of radical 35 by trapping with excess N 0 2 to yield nitro(phenyl)acetylene

23 Wieland, H.; Bluemich, E. Ann. Chem. 1921, 424, 100.

31 (lc) (Equation 43). To trap 35 with N02, nucleophilic coupling with the metal phenylacetylide (32) to give diphenylbutadiyne (33) must be avoided.

* n o 2 ^ Ph—c ~ c —N0 2 (43)

32 (M = Li) lc

A possible way to prepare nitro(phenyl)acetylene (lc) is thus to add lithium phenylacetylide (32, M = Li) slowly to a large excess of N 20 4 (a source of N 02). The result of this experiment, however, is similar to that for reactions of sodium phenylacetylide (32, M = Na) in that 3-benzoyl-5-phenylisoxazoIe (48) is obtained in

15% yield along with diphenylbutadiyne (33, 25%), benzoyl cyanide (54, 5%) and benzonitrile (55, 2%) (Equation 44). The mechanism for formation of isoxazole 48 in the above experiment is presumably similar to that for reaction of N 20 4 and sodium phenylacetylide (Equations 39-42). Thus phenylacetylene radical (35) abstracts hydrogen from the solvent before being trapped by N 02. The resulting phenylacetylene

(37) is then attacked by excess N 0 2 as in Equation 39. Benzoyl cyanide (54) might result from formation and rearrangement of nitroso(phenyl)acetylene as will be discussed shortly. Benzonitrile (55) may be the decomposition product of phenylacetylene nitrite as will be explained in detail in the section about Nucleophilic

Addition-Elimination.

32 o

Ph—C=C—Li — Ph—CM—C=C—Ph + Ph

33 (25%)

4 8 ( 15%)

(44) Ph PhCN 55 (2%) 54 (5%)

Attempts to trap radical 35 with NO-, radical always led to abstraction of hydrogen from the solvent to generate phenylacetylene and subsequent products. Use of a perfluoroalkane solvent (Fluorinert 48) yielded only diphenylbutadiyne (33) and resinous material.

In efforts to avoid electron-transfer reactions as previously deescribed, the behaviors of highly covalent, heavy metal phenylacetylides with varied nitrating agents were investigated. Bis-(phenylethynyl)mercury (32, M - HgCCPh) and trimethylstannyl(phenyl)acetylene (32, M = Me3Sn), when treated with N20 4 at -78 °C in Et 20 , have thus been found to give benzoyl cyanide (54) in yields of 76-100%. Use of covalent mercury and tin results in changes in the reaction pathways of metal phenylacetylides. Rather than electron transfer, electrophilic addition-elimination occurs. As an electrophile, N 20 4 ionizes to nitrosonium (NO+) and nitrate (NOj ) ions and functions as a nitrosating agent. Nitrosonium ion apparently adds directly to the

33 metal phenylacetylides to yield vinyl carbocation 56. Nitrate then displaces the metal

to form nitroso(phenyl)acetylene (57) (Equation 45). 1-Nitrosoacetylenes (12) are

known to dimerize and convert to acyl cyanides (14) (see Historical Section, Equation

8). In the present examples, nitroso(phenyl)acetylene (57) yields benzoyl cyanide (54,

Equation 46).

a © Ph—C=C-M — C-^M Ph—C=C-NO (45)

32 Ph/ NO 57

(M = Hg—C = C —Ph Me 3Sn)

Ph )C = C = N o 2 Ph—C = C —NO ------► O O ► 2 li (46) N = C = C Ph"" '"'CN 57 V Ph 54

Reactions of bis-(phenylethynyl)mercury (32, M = Hg-CCPh) with possible nitrating agents were then studied in other solvents. Use of CHClj with bis-

(phenylethynyl)mercury and N20 4 at -40 °C gives a different result than when Et20 is the solvent. An unidentified organomercury compound of high molecular weight is formed which decomposes on column chromatography on silica gel to give

34 acetophenone (58, 76%), On effecting the above reaction in CDCI3, the acetophenone

(58) obtained contains no deuterium. Use of N0 2BF4 in CH 2C12 with bis-

(phenylethynyl)mercury and subsequent chromatography yields acetophenone (58) quantitatively. The mechanistic aspects of the reactions of N 20 4 and N 0 2BF4 with bis-

(phenylethynyl)mercury and chromatography are as yet unclear. Mercuric ion catalyzed hydration of acetylenic derivatives of 32 (M = Hg-CCPh) during chromatography on silica gel is speculated to result in formation of 58 (Equation 47). Of further interest is that N 02BF4 and bis-(phenylethynyi)mercury in 1,4-dioxane gives a mixture of 58 and 54 in a 1.6:1 ratio. Whatever be the details of reactions of nitrating agents with bis-(phenylethynyl)mercury, the carbon-mercury bonds of the intermediate appear strong and none of the various reactions lead to nitro(phenyl)acetylene (lc).

O II (4 7 ) '"CH 3 32 58 (M = Hg—C =C—Phi

Earlier reactions of 1-trimethylstannylaikynes (15) with N 0 2BF4 in CH 2C12 at

20 °C to give 1-nitroacetylenes (1) have been described (see Historical Section,

Equation 11). Of particular interest is that Petrov et. al. have reported that phenyl(trimethylstannyl)acetylene (32, M = SnMe3) and N 0 2BF4 in CH3CN at 25 °C followed by chromatography yield nitro(phenyl)acetylene (lc) and a compound claimed

35 to be 3-cyano-2,2-dinitro-l-phenyl-l-propanone (59) (Equation 48). The assignment of

59 was based on its mass (249) and IR absorptions for nitrile (2200 cm'1) and nitro

groups (1535 and 1355 cm'1). Efforts have been presently made to duplicate the results

by Petrov el. a}24

Ph—C ^ C —SnMe3 CH3CN* Ph—C=C-N0 2 + Ph^^^CN (48)

32 (M = SnMej) lc °2N N°2 59

Treatment of phenyl(trimethylstannyl)acetylene (32, M = SnMe3) with N 02BF4

(1 equiv.) in CH3CN at 25 °C has now been found to yield phenylacetylene (37) as the

principal product. Nitro(phenyl)acetylene (lc), benzoyl cyanide (54) and 3-benzoyl-5-

phenylisoxazole (48) are produced in low yields (Equation 49). The fact that phenylacetylene (37) is produced in quantity clearly indicates that oxidation-reduction

(electron transfer) to give the phenylacetylene radical (35) is a major process. Of further note is that isoxazole 48 has a mass of 249 and thus identical to that for 60.

It is therefore likely that isoxazole 48 was produced in the experiments by the Petrov group. It is not yet clear whether lc is formed by reaction of the phenylacetylene radical (35) and N 0 2 or by electrophilic addition-elimination of 59 by nitronium ion

(N03*). Benzoyl cyanide (54) apparently arises by isomerization of

24 Petrov, A.A.; Zavgorodnii, V.S.; Rail’, K.B.; Vil'davskaya, A.I.; Bogoradovskii, E.T. Inventor's Certificate 401,136, 1971; Zhumal Obshchei Khimii, 1978, 48, 943 (Eng. trans. p. 865).

36 nitroso(phenyl)acetylene (57) as previously discussed (Equation 46). Formation of

isoxazole 48 is rationalized by the sequence proposed earlier in Equations 39-42.

NO BF Ph—C m : — SnMe 3 CH3C N * * Ph—C=C—H + Ph—C=C-N02

32 (M = SnMe3) 37 l c

O O II Ph (49) Ph CN Ph 54 48

In an attempt to generate N-iminoacetylenes (60) from N-chloroimines (61) and

lithium phenylacetylide (32, M = Li), Wurthwein and co-workers also encountered

oxidation and subsequent formation of diphenylbutadiyne (33 ).25 By using lithium

phenylacetylide cuprate (62), they were able to overcome this oxidation and prepare

N-iminoacetylenes (60) (Equation 50). Lithium phenylacetylide cuprate (62), prepared

from lithium phenylacetylide (32, M = Li) and copper phenylacetylide (32, M = Cu)

in Ei20 (Equation 51) is found however to react with N 20„ at -78 °C to give

diphenylbutadiyne (33) in 71% yield. The behavior of 62 with NzO^ is thus similar to that of copper (I) phenylacetylide (32, M = Cu). The present result is also of interest

25 Wurthwein, R.-U.; Weigmann, R. Angew. Chem. Int. Ed. Engl. 1987, 26, 923.

37 C l \ (P h—C=C~^CuLh 4 W ph— C = C —N (5°) R- % y ~ H 32 (M = Li) r 61 60

in that it is readily explained by electron-transfer from copper in 62, rearrangement

resulting in acetylene-acetylene bonding loss of an electron and Cu+(I), and loss of

copper phenylacetylide with subsequent oxidation of radical anion 36 as in Equation

52.

A Ph—€=C—U 4 Cu—C=C—Ph ------► (Ph—C=C-^Oi—C=C—Ph (51)

32 (M = Li) 32 (M = Cu) 62

2 ^ i & Ph—C^C—Si L* N° i - (Ph—C s C ^ U " 1C55C— Ph Ll - Ph—C = C —C = C —Ph -NO2

Ph—C^C—Cu ♦ Ph—C^C—C=C—Ph ■ 2> Ph—C^C—C^C—Ph (52>

In the present research, all metal phenylacetylides other than bis-

(phenylethynyl)mercury react primarily with potential nitrating agents by electron

38 transfer to give phenylacetylene radical (35). Highly covalent metal phenylacetylides thus appear to offer the best possibilities for preparing nitro(phenyl)acetylene (lc) by nitration processes involving addition to the triple bond followed by elimination of the initial covalent bonded metal moiety.

39 POSSIBLE SYNTHESES OF 1-NITROACETYLENES BY NIJCLEOPHILIC

APPmON-ELIMINAllON METHODS

Preparation of 1-nitroacetylenes by reactions of nitrite ion (N 02) with terminal

acetylenes (63) having appropriate leaving groups (Equation 53) then became of

R—C = C —LG + N o f ------► R—C ^ C —N 0 2 + LG (53)

63 1

interest. Stang et al and others have studied the behaviors of various nucleophiles with

iodonium salts of varied acetylenes .26 In particular, reactions of

phenyfethynyl(phenyI)iodonium tosylate (64) with nucleophiles give the corresponding

substituted pheny(acetylenes (Equations 54-55 ).26 The mechanism of these reactions

begin with nucleophilic attack on the carbon beta to the iodonium group to yield ylides

65 (Equation 54). Loss of iodobenzene from 65 gives the subsequent vinyl carbenes

(66 ). Such unsaturated carbenes can be trapped with triethylsilane .26 If not captured,

66 rearrange to the corresponding substituted acetylenes 67 (Equation 55). Various nitrogen, oxygen, sulpher, selenium and phosphorus nucleophiles have been used to prepare the corresponding substituted acetylenes (67, Equation 55). The behavior of nitrite ion with an ethynyliodonium reagent has not been reported. Addition-elimination and rearrangement in reactions of acetylenic iodonium salts with nitrite ion could lead

36 For a recent review see: Stang, P. Russ. Chem. Rev. 1993, 42, 12.

40 © Nu I— Ph © © \ / Ph—C^C—I—PhOTos + Nu (54)

64 65

Nu -Phi *- Ph—C^C—Nu (55) Ph 67 66

to a general synthesis of 1-nitroacetylenes ( 1) or their isomeric 1-acetylene nitrites

(68 ).

R—C = C - N 0 2 R—C = C —O—N = 0

1 68

Reaction of sodium nitrite (10 equiv.) with 64 at room temperature under phase transfer conditions with water and CHCl, has been found to occur smoothly with loss of carbon dioxide and formation of benzonitrile (55, >45%) and iodobenzene. The behavior of 64 with sodium nitrite is peculiarly spectacular. A possible mechanism for this complex reaction is summarized in Equations 56-5 S. On the assumption that the mechanism of reaction of 64 with nitrite ion is the same as with previously studied nucleophiles ,26 nitrite ion attacks carbon beta to the iodonium group to give nitrovinyl

41 a ONO I— Ph ° 'N=;9 c = c s 64 + ^ 0 2 C=C ~Phl » / (56) / © Ph Ph

69 70

( ° ? *■ Ph—C = C —0 —N —O (57) jri -Y> P . / O ’ 72

Ph\ PK y ° C“f-° r= = c—o _____ C^C'c -^ c c°2> Ph—C=N (58) — % 55 74 73

ylide 69. Nitrite, an ambident nucleophile, reacts on oxygen rather than on nitrogen.

Ylide 69 then loses iodobenzene to form nitritovinyl carbene 70 (Equation 56) which

then rearranges to phenylethynyl nitrite (72) upon cyclization to 71 and then ring- opening (Equation 57). Phenylethynyl nitrite (72) could also be formed by migration of the phenyl group in 70, Ethynyl nitrites are as yet unknown. As discussed previously, NO groups frequently migrate as do protons. Thus, 72 rearranges to nitroso(phenyl)ketene (73). Intramolecular [2+2] cycloaddition of nitrosoketene 73 yields P-lactol 74 which then loses carbon dioxide to give benzonitrile (55, Equation

42 58). Intermediate 72 and 73 are members of classes of compounds unknown at the time of the present observations.

Treatment of diiodoacetylene with silver nitrite in CH3CN results in a vigorous reaction with evolution of gases. The products have not been completely identified. For more details see Appendix A.

To test the mechanism sequence in Equation 58, study of synthesis of phenylethynyl nitrite (72) and/or nitroso(phenyl)ketene (73) and/or of their decomposition products was initiated. Kowalski and Fields have prepared lithium phenylethynolate (75, Equation 59) by treatment of the lithium enolate of l',T- dibromoacetophenone (76) with tert-butyllithium (3.3 equiv.) in THF followed by elimination of LiBr .27 In the present study, reaction of NOCI at -78 °C with lithium phenylethynolate (75), prepared as above, is found to yield benzonitrile (55) and carbon dioxide as major products (Equation 60). Although nitrite 72 and/or ketene 73 have not been detected, the overall result is in agreement with the sequence in

Equation 60 as detailed in Equation 58.

27 Kowalski, C.J.; Fields, K.W. J. Am. Chem. Soc. 1982, 104, 321

43 OLi OLi t-BuLi U -78 °C Ph Ph— C = C —O—Li (59) I THF Br Br 75 76

N O C l 72 *■ 73 *• 74 *■ PhCN + C02 (60) -LiCl 55

Shortly after the present observations for reaction of ynolate 75 with NOC1, synthesis of nitrosoketene (77) was reported.2* Decomposition of 2,2-dimethyl-5- hydroxyimino-l,3-dioxane-4,6-dione (78) in toluene at 110 °C results in fragmentation to nitrosoketene (77), acetone and carbon dioxide .28 Nitrosoketene (77) is not isolable because of its instability and its decomposition products were not identified.

Nitrosoketene (77) was trapped, however, by [4+2] cycloaddition to high-boiling aldehydes to give adducts 79 (Equation 61 ).28 Because of the present observations in reactions of ynolate 75 with NOC1 (Equations 59-60), decomposition of 78 in refluxing toluene was investigated in the absence of a trapping agent. Decomposition occurs to give HCN and carbon dioxide (Equation 62); the HCN was identified as KCN upon absorption into aqueous KOH. Rearrangement of 77 thus appears to occur by the scheme illustrated in Equation 58. The intramolecular behavior of 77 is thus similar

28 Katagiri, N.; Kurimoto, A.; Yamada, A.; Sato, H.; Katsuhara, T.; Takagi, K.; Kaneko, C. J. Chem. Soc., Chem. Commun. 1994, 281.

44 to that proposed previously for nitroso(phenyl)ketene (73, Equation 58). As yet, however, ethynyl nitrites (68 , 72) are unknown.

,OH o IJ H N 0 = N 110 ° y ^ y ° c = c = o -acetone 0 0 VV 5 H ° 5> ° - c o 2 h 3c c h3 h 3c c h3 77

O H RCHO (61) R

77 79

HO C—C -► HCN * C0 2 (62) II i N —O

Investigation of the behavior of nitrosoketenes 73 and 77 has been presently extended to nitroketenes 80. Nitroketenes 80 may be preparable even though such compounds have never been isolated ,29 If nitroketenes 80 are highly unstable and

29 Zavlin, P.M.; Efremov, D.A. Zh Nauchno Prikl. Fotogrqfii 1992, 37, 128.

45 behave as do nitrosoketenes 73 and 77 (Equation 58), intermolecular decomposition will give carbon dioxide and nitrite oxides 81 (Equation 63).

RRO \ C—c —o c —c II I - c o 2 0 © N —O R—C=N—O (63) ' © © 81

There is a relevant study, however, of dehydrochlorination of chloro(nitro)acety I chloride (82).30 Treatment of 82 with triethylamine at 0 °C in the presence of phenylacetylene (37) yields 3-chloro-5-phenylisoxazole (83, 30%) (Equation 64). No

(64)

n o 2 37

82 83 explanation has been given for formation of 81 (R = Cl) but it is possible that the initially formed nitronate anion, 84, undergoes beta-elimi nation to give chloro(nitro)ketene (80, R = Cl). Ketene 80 might then cyclize to 86 with loss of carbon dioxide to yield chloronitrile oxide (81, R = Cl) which then reacts with phenylacetylene to form isoxazole 83 by [3+2] dipolar cycloaddition (Equation 65).

30 Kovalenko, S.V.; Gorin, V I.; Martynov, I V. Izv, Akad. Nauk. SSSR, Sen Khim. 1989, 6, 1454 (Eng. Trans. 1335).

46 There is an important alternate mechanism for formation of 81 (R = Cl) which avoids chloro(nitro)ketene (80, R = Cl) as a discrete intermediate, that is ring-closure of 84 with loss of chloride to give 85 and then conversion to 81 (R = Cl) and 83 (Equation

66 ).

O II Cl C k ^ (65) C = C = 0 82 • EtiN ^ C 1 (65) II ^ ® N ^ t N ©O^®NO 0 /V

84 80 (R = Cl)

(66 )

Cl O -CO ® © Cl— C = N - 0 (66 ) N —O O'' © © 81 (R = Cl)

In the present research, attempts have been made to trap ketene 80 (R = Cl) before carbon dioxide is lost. Acetyl chloride 82 was reacted with triethylamine in

Et20 at -78 °C in the presence of ethyl vinyl ether in an attempt to trap ketene 80 (R

= Cl) via [2+2] cycloaddition. Instead, nitrile oxide 81 (R = Cl) was trapped as isoxazole 86 by [3+2] dipolar cycloaddition with ethyl vinyl ether (Equation 67).

47 Solutions of acetyl chloride 82 and triethylamine in CHClj analyzed by FTIR at -78

DC showed no evidence for presence of nitroketene 80 (R = Cl).

Cl O

+ (67) EtO -78 o c O OEt N 0 2 86 82

There are many attractive routes to be explored for synthesis of nitroketenes

(80) and characterization of the behaviors of such compounds is challenging. Because of the prior study of nitrosation of lithium phenylethynolate (75) for preparation of phenylethynyl nitrite (72), nitroso(phenyl)ketene (73) and products thereof (see

Equation 60), synthesis and determination of the chemistry of 1-alkynyl nitrates (87) have also become of interest. Such nitrates are unknown and thus rearrangements to nitroketenes (80, Equation 68 ) and products thereof are logical. Reactions of lithium

R\ R — C ^ C —O N 0 2 C = C = 0 (68 ) o 2n 87 80 phenylethynolate (75) with excess acetone cyanohydrin nitrate ( 88) in THF at -78 °C have therefore been investigated. Phenylethynyl nitrate (87, R = Ph), nitro(phenyl)ketene (80, R = Ph) and products thereof, as summarized in Equation 69,

48 are not detected. Attempts to isolate phenylnitrile oxide (81, R = Ph) as its dimer (89) have not been successful.

-(CH3)2C 0 ^ Ph—C = C —0 N 02 -LiCN 87 (R = Ph)

( 6 9 )

Ph Ph Ph © e - c o 2 ^ Ph— C = N —O 0 2N 81 (R = Ph) 80 (R = Ph) 89

Additional studies of preparation of phenylethynyl nitrate (87, R = Ph) and/or nitro(phenyl)acetylene (80, R = Ph) have been initiated by addition-elimination with nitronium ion on phenyl(trimethylsilyl)ketene (90).31 Nitration of 90 with N 0 2BF4 is expected to attack initially on oxygen to give vinyl carbocation 91. Fluoride then displaces the silyl group to yield phenylethynyl nitrate (87, R = Ph). Much like NO,

N 0 2 might migrate to afford nitro(phenyl)ketene (80, R - Ph) which cyclizes and loses carbon dioxide (see Equation 63) to give phenylnitrile oxide (81, R = Ph). In the absence of a trapping agent, 81 (R = Ph) will dimerize to diphenylfuroxan (89,

Equation 70). Unfortunately, treatment of ketene 90 with N 0 2BF4 in CH3CN at 25 °C does not afford ketene 80 (R = Ph), nitrile oxide 81 (R - Ph) or furoxan 89.

31 Hoppe, I.; SchOllkopf, U, Liebigs Ann. Chem. 1979, 219.

49 Preparation and characterization of alkynyl nitrates and nitroketenes remain an important problem.

Phv wn Dc Ph ON02 q —C = o N02BF4» ' ' ------Ph—C ^ C —O N 02 , / j f © 3 ‘ Me3S h K 0BH4 87 (R - Ph) 90 91

(70)

Ph. Ph Ph v -CO, © © C = C = 0 ------Ph— C = N —O — ► V< N . N 02N ' ''o"©"0 81 (R = Ph) © 80 (R = Ph) 89

50 ATTEMPTED SYNTHESES OF DIN1TROACETYLENE BY RETRO DIELS-ALDER

REACTIONS

As has been discussed in the Statement of Problem and in the initial

Discussion, dinitroacetylene (3) is of great interest but is yet unknown. Synthesis of

3 by reactions of acetylides with various nitrating agents has failed. For possible preparation of 3, development of retro Diels-Alder methodology as in Equation 71 has

n o 2

(71)

been initiated. Of relevance is that dicyanoacetylene (92) is obtained by cycloreversion o f adduct 93 at 175 °C (Equation 72).32

32 a) Diels, O ; Alder, K. Ber. Deut. Chem, Ges. 1929, 62, 2337; b) Weis, CD. J. Org. Chem . 1962, 27, 3520; c) ibid, 3693; d) Wittig, G.; Mayer, U. Chem. B er 1963, 96, 342; e) Finnegan, R.A.; McNees, R.S. Tetrahedron. Lett. 1962, 755.

51 o c h 3o 2c c o 2c h 3 c h 3o 2c 175 °C NC—CsC-CN - ► H (72> o c h 3o 2c ■CN 92

Baum and Tzeng report that tetranitroethylene (94) is produced by thermal elimination of hexanitroethane (95, Equation 73) under proper conditions .13

Tetranitroethylene (94) is highly electron-deficient and therefore an extremely reactive dienophile. Tetranitroethylene is at least "one order of magnitude" more reactive in

Diels-Alder reactions than is tetracyanoethylene. Tetranitroethylene ( 86 ) is, however, also a strong oxidizing and nitrating agent which often causes complications in cycloaddition reactions. Tetranitroethylene (94) does undergo fairly clean Diels-Alder reactions with anthracene (96a) to give 9,10-dihydro-11,1 l,12,12-tetranitro-9,10- ethanoanthracene (97a, Equation 74). As does hexanitroethane (95), adduct 97a loses

N20< when properly heated (Equation 75). The product, 9,10-dihydro-11,12-dinitro-

9,10-ethenoanthracene (98a) is, in principle, a Diels-Alder adduct of anthracene (96a) and dinitroacetylene (3) .

33 Baum, K ; Tzeng, D.J. J Org. Chem. 1985, 50, 2736.

52 o 2n n o 2 270 OC \ / (OaNfcC—C3 » . C —c (73) 1 mm Hg o 2n n o 2 95 94

(74)

96a-e 97a-e

250 o c (75) 0.05 mm Hg

98a-e

Z = H (a), Me,SiO (b), Me^N (c), MeO (d), Me (e)

Dinitroethenoanthracene 98a has now been prepared for study of its posssible

Retro Diels-AJder conversion (Equation 76) to dinitroacetylene (3) and anthracene

53 OjN

H o 2n —ce=c ~ n o 2 + (76)

(96a). Tetranitrocycloadduct 97a is obtained in 60-100% yield by (1) vacuum decomposition (1 mm Hg) of hexanitroethane (95) to "clean" tetranitroethylene (94) and cycloaddition with anthracene (96a) or (2) heating mixtures of hexanitroethane (95) and anthracene (96a) to give 97a upon generation of tetranitroethylene (94) in situ. At

260 °C, 97a loses N 20 4 to form dinitroethenoanthracene (98a, 60%), a handleable crystalline compound.

Adduct 98a is a remarkable, stable compound and requires surprisingly high temperature for its presumed Retro Diels-Alder reaction. When 98a is sublimed through a heated (430 °C) horizontal pyrolysis apparatus packed with quartz chips

(0.25 mm Hg), anthracene (>99%), CO: and N 2 are produced as major products. Study of decomposition of 98a in a heated GC injector at various lower temperatures and analysis of the products by MS and 1R show that decomposition does not occur below

250 °C and, along with anthracene (96a), the gaseous products include C 03. There is no evidence for dinitroacetylene (3) in any of these experiments. Because of the high

54 temperature necessary for decomposition of 98a, 3 does not survive, decomposing to nitrogen and carbon dioxide before being isolated or trapped (Equation 77).

4 3 0 OC 98a o 2n —c ^ c —n o 2 2 C 0 2 + N2 (77) 0.05 m m H g

Czamik el a/34 have studied the effects of anthracene substituents on the rates of Retro Diels-Alder reactions of 9,10-ethanoanthracenes (99, Equation 78). Such

200-250 QC

99 reverse Diels-Alder reactions give olefins and 9,10-disubstituted anthracenes (96) at much lower temperatures when the 9,10-substituents in 96 are electron-donating. Study has been presently made of cycloadditions of tetranitroethylene (94) to electron-rich

9.10-disubstituted anthracenes (96b-e, Z = Me3SiO, M e2N, MeO, Me), subsequent eliminations o f N 2(X, from 97b-e, and thermolyses of 98b*e to dinitroacetylene (3) and

9.10-disubstituted anthracenes (96b-e) as summarized in Equations 73-76. The various

9.10-disubstituted anthracenes (96b-e, Z = Me3SiO, Me2N, MeO, Me) were prepared

34 Chung, Y.; Duerr, B.F., McKelvey, T.A.; Nanjappan, P.; Czamik, A.W. J Org Chem. 1989, 54, 1018.

55 by literature procedures as described in the Experimental Section. Synthesis of 96b (Z

= Me^SiO) is of particular interest because removal of the trimethylsilyl groups, possibly by fluoride ion, would give the very electron-rich adduct 100 which might

cyclorevert to dinitroacetylene (3) upon limited heating (Equation 79).

2 F® ,o e

98b 100

o 2n —c = c —n o 2 (79)

Synthesis of adduct 97b by Diels-Alder cycloaddition of anthracene 96b with tetranitroethylene (94) as prepared discretely is not successful. Extensive oxidation of

96b occurs to yield 9,10-anthraquinone (101, 83-100%). 9,10-Diamino-N,N,N'N’- tetramethylanthracene (96c) and 94 also form 9,10-anthraquinone (101). However,

9,10-Dimethoxyanthracene (96d) reacts cleanly with hexanitroethane (95) at room

56 temperature in CHCl 3 with loss of N20 4 to give cycloadduct 97d (62%). All attempts to remove N20 4 from 97d to prepare 98d give 9,10-anthraquinone (101). In fact, simply dissolving 98d in a solvent (CHC13, acetone, 1,2-dimethoxyethane, THF) causes decomposition to 101. 9,10-Dimethylanthracene(96e) and 94 also yield a cycloadduct

(97e). Adduct 97e then converts to 101 upon attempted elimination of N20 4 by thermolysis. Reaction of 9-methoxyanthracene and 9,10-diphenoxyanthracene with 94 also give 9,10-anthraquinone (101). 9,10-Dinitroanthracene does not react with 94 and

9,10-dibromoanthracene and 2,3,6,7-tetramethoxy-9,10-dimethylanthracene do not give stable Diels-Alder adducts with 94. The causes of the reactions of most 9,10- disubstituted anthracenes (96) with 94 to give 101 are not known. Tetranitroethylene

(94) readily loses N 0 2 (Equation 80). The N 0 2 thus produced might cause conversion of anthracenes 96 to anthraquinone 101 as illustrated in Equation 81.

o 2n^ n o 2 n o 2 / i n o 2 + c = c (80)

Z ONO o

2 N 02 -2 ZNO 96b-e ------► ► (81)

ONO Z

101

57 OXIDATION OF CYANOGEN-N.N-D1QXIDE 11031

An attractive approach to synthesis of dinitroacetylene (3) is oxidation of an

acetylene containing two nitrogen functional groups. Various methods for oxidizing

nitrosoacetylenes (12) to nitroacetylenes (1) are discussed in the Historical Section.

Dinitrosoacetylene (102) should, in principle, be oxidizable to nitro(nitroso)acetyiene

(104) and then dinitroacetylene (3). Acetylene 102 is not a discrete compound; it is a resonance form of cyanogen-N,N'-dioxide (103). If 102 is a strong enough resonance contributor, oxidation to 3 appears feasible (Equation 82).

0=N —C=C—N—O ------► O —N = C —C = N — O

102 103 (82)

[Ol [Ol 1 1 » o = n —c = c —n o 2 » o 2n —c = c —n o 2

104 3

Cyanogen-N,N'-dioxide may be prepared by classical methods .35 Chlorination of glyoxime (105) in hydrochloric acid yields dichloroglyoxime (106).36 A two phase dehydrochlorination of 106 with N a jC O ^ in H:0/CHC1 3 at 0 °C gives cyanogen-N,N'- dioxide (103, Equation 83). Cyanogen-N,N’-dioxide (103) must be handled at low

35 Grundmann, C. Angew. Chem. Int. Ed. Engl. 1963, 2, 260.

36 Ponzio, G.; Baldracco, F. Gaz Chim. Ital 1930, 60, 434,

58 temperatures and in solution. Neat 103 is pyrophoric and explosive. Even when kept at -25 °C in solution, 103 must be used within a few hours because it polymerizes to explosive materials.

HO ^OH ct2 1 JP N.jCO, (.

Solutions of dioxide 103 in CH 2C12 were treated with various oxidizing agents in attempts to prepare nitro(nitroso)acetylene (104) and/or dinitroacetylene (3). Metal oxides: Ag 20, KMn04, Mn0 2 and Cr03, convert 103 at 0 °C to intractable materials presumed to be polymers of 103 and their derivatives. Neither dinitroacetylene (3) nor nitro(nitroso)acetylene (104) was detected in the products by FTIR. Bis-

(trimethylsilyl)peroxide, m-chloro perbenzoic acid, H 20 2, dimethyldioxirane and ozone react with 104 in CH2C12 at -78 to 0 °C but do not give 3 or 104. The various products from these reactionswere not identified because of their complexities and the danger.

Oxidizing of 103 should be studied further. In addition to 103, other acetylenes containing two nitrogen functionalities should be investigated. REACTIONS OF N ITROfTRIME1HY LSILY Li A CETY LEN E

Preparation of nitro(trimethylsilyi)acetylene (lg) from commercially available starting materials is discussed in the Historical Section. Acetylene lg is a 1- nitroacetylene that is functionalized in the 2-position. Functional group interconversion of the silyl group will lead to new 1-nitroacetylenes. The silyl group is a common protecting group in organic synthesis and therefore many methods for its removal exist.

Removal of the silyl group from lg under basic or neutral conditions would provide nitroacetylene anion (107). Anion 107 will be a valuable reagent for making a host of

1-nitroacetylenes (1) by reaction with electrophiles (Equation 84).

Me3Si— C s C - N 0 2 ~Me3Si£ e C= C —N02 E » E—C=C-N02 (M)

lg 107 1

The most convenient method for removal of a silyl group is displacement by fluoride ion. When lg is treated with a source fluoride ion (n-Bu 4NF, KF, CsF) at a temperature range from -100 °C to room temperature, an immediate darkening of the solution occurs. Only very polar material remains in the reaction mixture. Even in the presence of electrophiles (H 20, MejSiCl, acetone, benzoyl chloride, N 0 2BF4), no 1- nitroacetylenes are obtained. Treatment of lg with N 0 2BF4 in an attempt to produce dinitroacetylene (3) results in no reaction under mild conditions. Forcing conditions destroy the starting material and yield only intractable material.

60 An additional method of removing a silyl group from an acetylene is by

treatment with aqueous silver nitrate. Silver acetyhdes (109) form just as is known for

terminal acetylenes. Such silver acetylides (109) are converted to terminal acetylenes

(10) by treatment with aqueous KCN (Equation 85).37 When lg is reacted with an

R-_C= C_ S iMe3 EtOH^qT R—C^C-Ag R C^C H (85) 108 109 10 aqueous solution of silver nitrate, a colorless or black (possibly containing colloidal silver) precipitate forms. The insoluble solid explodes when heated or when in contact with bromine. The amorphous solid reacts with halogen compounds such as HCI,

M e3SiCl, acid chlorides, bromine and iodine. Silver halide always precipitates from such reactions but no organic compounds can be identified Protonation of this solid with acids or in KCN (aq) does not afford nitroacetylene. The structure of this compound has not been elucidated. Equation 84 suggests the compound might be silver nitroacetylide (109, R = N 02) but such an assignment has not been confirmed by spectroscopy or chemical tests.

Functional group interconversion of nitro(trimethylsilyl)acetylene is a logical approach to new 1-nitroacetylenes. Such a method has yet to yield any 1- nitroacetylenes, probably because of the extreme reactivity of the nitroacetylene anion

(107). A further problem is the sensitivity of 1-nitroacetylenes to acids and

37 a) Schmidt, H.M.; Arens, J.F. Reel. Trav. Chim. Pqys-Bas Belg. 1967, 86, 1138. b) Corey, E.J.; Ruden, R.A. Tetrahedron Lett. 1968, 5041.

61 anion (107). A further problem is the sensitivity of 1-nitroacetylenes to acids and

nucleophiles.

62 SUMMARY: PART 1

Methods for preparing 1-nitroacetylenes (1) and dinitroacetylene (3) have been studied. Attempts to provide general syntheses for 1-nitroacetylenes by nitration of acetylides are described. Retro Diels-Alder reactions and nucleophilic addition- eliminations of phenylethynyl(phenyl)iodonium tosylate were investigated. Oxidations of cyanogen-N,N'-dioxide were studied in attempts to prepare dinitroacetylene.

Investigation has also been made of possible syntheses of mononitroacetylide ion.

These studies are summarized as follows.

Nitration of Phenylacetylides

Various metal phenylacetylides (32, M = Li, ZnCl, ZnBr, Cu, MgBr, K, Na) react with N 02BF„, N20 5, N20,«, p-TosO N 02, Me3S i0 N 0 2 or n-PrON0 2 at -100 to 25

°C to give diphenylbutadiyne (33) and phenylacetylene (37). The reactions are initiated by electron transfer from the acetylide to yield phenylacetylene radical (35).

Presumably, radical 35 undergoes addition by soluble nucleophilic metal phenylacetylides (32, M = Li, Cu) followed by electron transfer to give diphenylbutadiyne (33, Equation 86 ). For non-nucleophilic or insoluble phenylacetylides (32, M = ZnCl, ZnBr, Na, K), radical abstraction of hydrogen from solvent yields the phenylacetylene (37, Equation 87). Treatment of lithium phenylacetylide (32, M = Li) with N20,, (1 equiv.) in THF at -78 °C yields

63 Ph— C s C —M + ® N 02 ------► Ph—C=C ■ + -N02

32 3 5

■ NO, ► Ph— C==C—C isC —Ph + © N 02 (8 6 ) 33

Ph—C=C- + H—Sol ------► Ph—C=C—H + -Sol (87)

35 37 diphenylbutadiyne (33) along with the products of 1,4-addition of 35 to 33 and then reaction with N 0 2 to give nitrocumulene 42 (Equation 88).

, Ph c = c = c = c Ph— C = C —C = C —Ph ♦ -C = C —Ph ♦ Ph C v

33 35 Ph

•N 02 ° 2Nk , ph ^ C = C = C = C (88) P h ' V

42 Ph

64 Exceptions to the electron-transfer processes occur with covalent, heavy metal phenyl acetyl ides (32, M = Hg (II), Me 3Sn). Bis-(phenylethynyl)mercury (32, M = Hg-

CCR) reacts with N2Os or N 0 2BF4 to yield organomercury compounds while phenyl(trimethylstannyl)acetylene (32, M - Me3Sn) reacts with N 02BF4 mostly by electron transfer to afford acetylenes 37. Addition-elimination also occurs to yield nitro(phenyl)acetylene (lc, Equation 89).

FtK0 Ph—C=C—SnMe3 * N02BF4 ------► 4^_c/SnMe3 ' ph—c=C—N02 (89)

P / ' N° 2

Nucleophilic Addition-Elimination Reactions

Reactions of sodium nitrite and phenylethynyl(phenyl)iodonium tosylate (64) do not yield nitro(phenyl)acetylene (lc); benzonitrile (55) and carbon dioxide are obtained. A possible mechanism is nitrite ion attack on 64 to yield ylide 69 which loses iodobenzene to give vinylcarbene 70 (Equation 90). Carbene 70 rearranges to phenylethynyl nitrite (72) (Equation 91) which then quickly isomerizes to nitroso(phenyl)ketene (73). Intramolecular (2+2] cyclization of 73 gives 74 which loses carbon dioxide to yield benzonitrile (55, Equation 92). Independent synthesis of 72 and/or 73 from nitrosation of lithium phenylethynolate (75) also produces 55 (Equation

93). The parent nitrosoketene (77), prepared by thermolysis of oxime 78, loses carbon dioxide and gives HCN (Equation 94).

65 0n-r ® OTos ONO .1— Ph O J ©, NaNO, V J -Phi Ph—C=C—IPh 1 ------,c = g c = c f <

69 70

<&KVT\ y ► Ph—C^C—0-N=0 (91) P h ' ^ 72 71

Ph. Ph. O C-^C COi N*r° Ik^tw Ph—C=N (92) o 55 74 73

OLi OU /■ Rr t-BuLi 1 , . -78 c>C P h ^ c ' ------^ Ph^^C" , » Ph—C=C-0-Li rn y x h F ™ | -LiBr Br Br 75

72 ► 73 ► 74 ► PhCN - C 0 2 (93) 55

66 „OH O N II II (V >C .O iinnr1I0°C ~^ N 'c=€=o °vM ^ ^ ° -acetone / Ov^O °^>° -C°2 H H3c / V CH „ 3 .H3c . _ x CH3 77

H O xc-c * -► HCN * CO, (94) N—OII I

Retro Diels-Alder Reactions

Attempts to produce dinitroacetylene (3) by a retro Diels-Alder reaction of 9,10- dihydro-ll,12-dinitro-9,10-ethenoanthracene (98a) at 250-430 °C and 0,05 mm Hg result in formation of anthracene (96, Z = H), carbon dioxide and nitrogen (Equation

95). Apparently, conditions for cycloreversion of 98 (Z = H) are too harsh for dinitroacetylene (3) to survive. Attempts to prepare 1 l,12-dinitTo-9,10- ethenoanthracenes (98, Z = Me3SiO, Me2N, MeO, Me) with electron-donating groups in the 9 and 10 positions, in hopes that cycloreversions to 3 and 96a would proceed at much lower temperatures, always led to formation of 9,10-anthraquinone (US) possibly because of oxidation of the 9,10-disubstituted anthracenes 96 by N 0 2 as generated from tetranitroethylene (Equations 96, 97),

67 o 2n ^ o 2 /J0 2 c = c -N02 ♦ C=C (96) 0 2 ^ n o 2 o 2n n o 2

L ONO 2 NO; -2ZNO (97)

ONO Z

Oxidation of Cyanogen-N,N-dioxide (103)

Oxidation of cyanogen-N,N'-dioxide (103) with ozone, oxygen, bis-

(trimethylsilyl)peroxide, dimethyldioxirane, KMn04, M n02, CrOj and Ag30 fail to give nitro(nitroso)acetylene (104) or dinitroacetylene (3) (Equation 98).

102 103 (98)

[O] [O] 0=N — C=C—N0 2 / / * o 2n — c = c —n o 2 - t 104 3

Reaction of Nitn>(trimetfiylsilyl)acetylene (lg) with Fluoride Ion

Removal of the trimethylsilyl group from nitro(trimethylsilyl)acetylene (lg) with fluoride ion (n-Bu 4NF, KF, CsF) results in decomposition of the nitroacetylene

68 even in the presence of an electrophile (Me 3SiCl, HCI, benzoyl chloride, acetone) and at -100 °C. No nitroacetylene anion or products thereof were found (Equation 99).

-Me3SiF E® Mc3Si— C = C —N 02 $ » ©C=C-N02 // - E—C=C-N02 (")

lg 107 1

69 PART 1

CHAPTER 3

EXPERIMENTAL SECTION

General Procedures

Melting points of solids melting below 200 °C were determined in capillary tubes in a Thomas Hoover melting point apparatus and are uncorrected. Melting points of solids melting above 200 °C were obtained using glass plates on a Fisher-Johns melting point apparatus.

Infrared spectra (IR, bands reported in cm'1) were produced with a Perkin Elmer

(Model 1600) Fourier Transform single-beam infrared spectrophotometer. Liquid samples were analyzed as neat, thin films between sodium chloride (NaCI) plates. Solid samples were analyzed as dispersions in pressed potassium bromide (KBr) pellets.

Nuclear magnetic resonance spectra (NMR, peaks reported in ppm downfield from tetramethylsilane at 8 0.00) were determined on a AM-200 Fourier Transform

Nuclear magnetic resonance spectrometer. The spectrometer ran at an operating frequency of 200.133 MHz for lH spectra and 50.323 MHz for nC spectra.

Ultraviolet/visible spectra were obtained with a Hewlett Packard (Model 8452A)

Diode Array Spectrophotometer. Samples were analyzed in quartz cuvets using

70 spectroscopy-grade solvents. Reference spectra were taken for the same solvent as used for the sample and were scanned immediately prior to scanning the samples.

High resolution mass spectra were obtained from The Ohio State University

Chemical Instrument Center using either a VG 70-250S or a Kratos MS-30 mass spectrometer.

The reaction mixtures were analyzed in a Hewlett-Packard gas chromatograph

(Model 5890, Series II) equipped with a mass spectrometer detector (Model 5970B) and a Fourier Transform infrared detector (Model 5968A) (GC/MS/IR). Infrared spectra from this instrument are reported as "gas phase". Mass spectra are low resolution.

Relative amounts of components in a mixture were determined by integration of peaks areas in the total ion chromatograph obtained by the mass spectrometer. Quantitative measurements of yields were made by comparison of peak areas to that of an internal standard. The internal standard used was diphenylacetylene unless otherwise noted. The instrument was standardized for each product by comparing peak sizes for mixtures of known ratios of product and internal standard.

GLC separations were made on a Varian Aerograph (Model 920) using a 10' x 0.25" Gas Chrom Q column ( 100-120 mesh, GE SE 30 15%).

Reaction solvents were dried and purified prior to use. Diethyl ether (Et 20 ) and tetrahydrofuran (THF) were distilled from sodium or sodium/potassium alloy with benzophenone as an indicator. Benzene and acetonitrile (CH 3CN) were distilled from calcium hydride. Methylene chloride (CH 2C12), chloroform (CHClj) and carbon tetrachloride (CC14) were distilled from phosphorus pentoxide (P 2Os). Other solvents

71 were distilled from appropriate desiccants prior to use. Commercial solvents were used

for recrystallization, extraction and chromatography. Solvents were typically removed

from reaction products in vacuo on a rotary evaporator at pressures ranging from 40

to 60 mm Hg,

Reagents were distilled or recrystallized prior to use. Butyllithium (BuLi) bases

were titrated periodically using diphenyl acetic acid as indicator Nitronium

tetrafluoroborate (N0 2BF4), obtained from Aldrich, Strem or Pfaltz and Bauer, was

triturated with clean nitromethane several times and dried at 1 mm Hg immediately

prior to use.

Throughout the experimental, the following abbreviations are used: PE

(petroleum ether, bp 35-60 °C), CH3OH (methanol), EtOH (ethanol), EtOAc (ethyl

acetate), DMSO (dimethyl sulfoxide), SG (silica gel) and TLC (thin layer

chromatography).

NITRATION OF METAL ACETYLIDES

Preparation of N20 4 Solutions in EtjO

Commercial N 20 4 from a steel cylinder was condensed through Tygon tubing into a round bottom flask equipped for distillation and cooled to 0 °C. The N20 4 was distilled upon gentle heating by steam into a tared receiver cooled to 0 °C. The distillations removed any plasticizers leeched from the Tygon tubing. The receivers were removed and weighed. A carefully measured volume of dry EtjO, cooled to 0 °C,

72 was added to the N 20 4. A solution of known molarity could then be obtained by

dividing the number of moles of N 20 4 by the total volume of EtjO and N 20 4. Dry

oxygen was bubbled through the cold solution until the mixture became amber. These

solutions were kept at -25 °C and treated with oxygen before each use Solutions were

replaced after 1 week.

Preparation of NzOs Solutions in CC14

The procedure used is essentially that reported by Dailey .38 Approximately 50

mL o f N 20 4 was condensed into a 3-neck 500 mL round bottom flask equipped with

stopper, gas inlet and distillation head. A vacuum adapter and receiver were placed on

the distillation head A drying tube filled with CaCl 2 was placed on the vacuum outlet.

All joints were wrapped with Teflon tape (grease is attacked by oxides of nitrogen

causing freezing of the joints). A stream of ozone (1.1 mmol/min in 0 2) produced by

an ozone generator was added through the gas inlet. The receiver was cooled to -78

°C and the N20 4 warmed gently with a water bath. While being distilled, the N 20 4 was

oxidized by the ozone to N 20 5 which collected in the receiver as a white solid. After

3.5 h, brown fumes of N 20 4 were no longer seen and a small amount of liquid

remained in the reactor. The receiver was removed and equipped with a distillation head, a vacuum adapter and a tared receiver. The receiver was cooled to -78 °C with acetone/C02. The N 2Os was sublimed at 5 mm Hg by gentle warming with a water

38 Dailey, W.F. Tetrahedron 1990, 46, 7341-7358.

73 bath. The white N2Os crystals were weighed and dry, cold CC1 4 (50 mL) was added.

These solutions were kept at -25 °C.

Addition of N20 4 to Lithium Phenylacetylide

Phenyl acetylene (0.50 g, 4.9 mmol) was dissolved in Et20 (10 mL) and cooled to -78 °C under argon. n-Buty I lithium (3.7 mL, 1.31 M in hexanes) was added with stirring and then N 20 4 (1.72 mL, 2.85 M in Et 20) was added dropwise via syringe. A suspension immediately formed. The cooling bath was removed after the addition was complete. Analysis by GC/MS/IR showed almost exclusively diphenylbutadiyne (33,

80% GC yield). The mixture was allowed to come to room temperature, poured into

5% NaXOj (aq, 50 mL) and extracted with Et20 (3 x 35 mL). The Et20 extracts were combined, dried over M gS04, filtered and concentrated in vacuo. The resulting residue was chromatographed (SG, 4; 1 hexanes/EtOAc), Diphenylbutadiyne (33) was obtained as slightly yellow crystals (0.27 g, 55% yield). Recrystallization from EtOH/H20 gave white needles: mp 85-87 °C (lit .39 86-87 °C); FTIR (NaCl, melt) 3049 (m), 2149.3 (w),

1592.0 (m), 1484.9 (m), 1439.1 (m), 1024.3 (m), 915.7 (m), 756.8 (s), 687.6 (s) cm 1;

’H NMR (CDC13) 6 7.49-7.55 (m, 2H), 7.31-7.35 (m, 3H). The aqueous layer was tested for nitrite ion by acidification with 50% H 3P 0 4 (aq) and application to Kl/Starch paper.40 The test for nitrite was positive as indicated by instant formation of a dark

39 Brandsma, L. Preparative A cetyienic Chemistry, Elsevier, New York, 1976, 156.

40 Schonbein, H. J Prakt. Chem, 1847, 41, 227.

74 blue color. There was no evidence for nitro(phenyl)acetylene but phenyl acetylene was often detected by GC/MS/IR in small amounts.

Addition of Lithium Phenylacetylide to N20 4

Lithium phenylacetylide in Et20 (previously prepared from phenylacetylene

(0.50 g, 4.9 mmol) and n-BuLi (3.74 mL, 1.31 M in hexanes)) was transferred dropwise via cannula (-10 min.) to N 20 4 (1.72 mL, 2.85 M in E^O) at -78 °C under argon. The mixture was warmed to room temperature. Diphenylacetylene was added as an internal standard and the reaction solution was analyzed by GC/MS/IR. The only reaction products found were phenylacetylene (37, 60%) and diphenylbutadiyne (33,

13%).

Preparation o f Copper Phenylacetylide

Copper phenylacetylide was prepared by a literature method as follows .41 In a

2 L Erlenmeyer flask was placed a magnetic stirbar and a solution of copper sulfate pentahydrate (25.0 g, 0.100 mol) in concentrated NH4OH (aq, 100 mL). upon addition of water (400 mL), the reaction mixture was cooled in an ice bath. Solid hydroxylamine hydrochloride (13.9 g, 0.200 mol) was added over 10 min with cooling.

Phenylacetylene (10.25 g, 0.100 mol) in 95% EtOH (500 mL) was then introduced rapidly to the bright blue solution. A yellow precipitate formed immediately. Stirring

41 Owsley, D C ; Castro, C.E. Org. Synth. 1972, 52, 128-131.

75 became difficult and the mixture was then swirled. Water (500 mL) was added and the

mixture was allowed to sit 5 min. The yellow precipitate obtained was filtered off in

a large, coarse, sintered glass funnel. The fluffy yellow solid was washed with water

(5 x 100 mL), EtOH (5 x 100 mL) and Et20 (5 x 100 mL). The last few washings

were hastened by scraping the glass frit. The resulting pasty, yellow solid was dried

in a vacuum oven at 65 °C and 50 mm Hg overnight. The copper phenylacetylide

(14.94 g, 91%) obtained was powdered by mortar and pestle and stored in an amber

bottle under argon.

Addition of N20 4 to Copper Phenylacetylide

Copper phenylacetylide (0.30 g, 1.8 mmol) was suspended in dry Et20 (10 mL)

and cooled under argon to -78 °C. Dinitrogen tetroxide (1.5 mL, 1.24 M in Et 20 , 1.8

mmol) was added dropwise with stirring. Reaction began almost immediately and the

suspension changed from yellow to green After addition was complete, the mixture

was dark green. The heterogenous solution was slowly warmed to room temperature

and filtered through Celite to remove the green precipitate. The filtrate was washed

with 5% NaiCOj (aq), washed with brine, dried over MgS0 4 and concentrated to dryness. After the product had dried at 1 mm Hg, diphenylbutadiyne (33) (0.13 g,

72%) remained as yellow crystals: mp 75-81 °C. Crude diyne 33 was chromatographed

(SG, 4 :1 hexanes/EtOAc) (0.11 g, 61%) and then recrystallized from EtOH/H:0. White crystals of 33 (0.09 g, 50%) were obtained: mp 85-87 UC (lit .39 86-87 °C). No traces of nitro(phenyl)acetylene (lc) or phenylacetylene (37) were seen. The above green

76 precipitate tested positive for nitrite. The solid was then heated for 0.5 h in 20% H 2S 0 4

(aq) and the organic components were extracted with Et20 The E^O extracts were washed with water and 5% NajCOj (aq) and dried over M gS04. Removal of the Et20 left acetophenone (0.008 g) thus indicating that very little unreacted copper phenylacetylide or phenylacetylene remained after the reactions were stopped.

Addition of Copper Phenylacetylide to N20 4

A solution o f N 20 4 (0.35 mL, 8.56 M in Et 20) was cooled to -78 °C under argon. Finely powdered copper phenylacetylide (0.50 g, 3,0 mmol) was added to the

N20 4 solution via solid addition funnel in 1 h. The mixture was warmed to room temperature and filtered through Celite. TLC showed mostly one product and polar material. The filtrate was analyzed by GC/MS/IR showing almost exclusively diphenylbutadiyne (0.0715 g, 24%) with a trace of benzonitrile (0.0013 g, 0.4%). The remainder of the product mixture was intractable.

Slow Addition of Lithium Phenylacetylide to Excess N20 4

n-Butyllithium (0.86 mL, 2.27 M in hexanes) was added to phenylacetylene

(0.20 g, 1.96 mmol) in Et20 (10 mL) at 0 °C. This mixture was cannulated in 50 min into a freshly prepared solution of N 20 4 (6.6 mL, 2.99 M in Et20 ) at -78 °C.

GC/MS/IR showed diphenylbutadiyne (33) (0.0487 g, 24.6%), 3-benzoyl-5- phenylisoxazole (48) (0.0373 g, 15.3%), benzoyl cyanide (54) (0.0123 g, 4.8%), and benzonitrile (55) (0.0049 g, 2.4%) to be present. Diyne 33 and phenylisoxazole 48

77 were isolated by column chromatography (SG, 4:1 hexanes/EtOAc). Phenylisoxazole

48 was isolated as yellow crystals (7%). Analytical samples of 48 were obtained by recrystallization from hexanes or EtOH/H 20; mp 81-82 °C (lit.42 89 °C); FTIR (KBr)

3147.5 (w), 3061.0 (w), 1655.2 (s), 1596.5 (m), 1572.0 (m), 1449.0 (m), 1243.6 (m),

893,7 (m), 769.6 (m), 726.0 (m), 683.0 (m) cm 1; 'H NMR 5 (CDC13) 8.3 (m, 2H), 7.8

(m, 2H), 7.5 (m, 6 H), 7.0 (s, 1H) ppm, nC NMR (CDC13) 185.8, 170.8, 162.4, 135.8,

134.1, 130.73, 130.695, 129.2, 128.6, 126.7, 126.0, 100.2 ppm.; MS (High Res) m/e

249.0792 (M+) (calc. 249.0790), 105, 77, 51; calcd for C 16HnN 02: C, 77.10; H, 4.45; found: C, 76.99; H, 4.50. The other products (33, 54 and 55) were identified by their

IRs, MSs (Low Res) and GC retention times as compared to authentic samples.

Slow Addition of Copper Phenylacetylide to Excess Nz0 4

A solution of N 20 4 (8.2 mL, 2.99 M in Et20) was cooled to -78 °C under argon. Copper phenylacetylide (0.20 g, 1.22 mmol) was added via a tared solid addition funnel in 50 min. At the half-way point of the addition, TLC showed only diphenylbutadiyne (Rf= 0.52, 4:1 hexanes/EtOAc) to be formed. After the addition was complete, TLC still only showed diphenylbutadiyne (33) and polar material The tared solid addition funnel contained residual copper phenylacetylide (0.01 g). The cold reaction mixture was poured into 10% Na^O^ (aq, 100 mL). The organic layer was separated, dried over MgS0 4 and concentrated to dryness to leave yellow crystals (0.14

42 Hassner, A.; L'abbe, G ; Miller, M.J. J Am. Chem. Soc. 1971, 93, 981.

78 g). Column chromatography (SG, 4 :1 hexanes:EtOAc) of the product afforded nearly

white crystals of diphenylbutadiyne (33, 0.07 g, 60% based on 0.19 g of copper

phenylacetylide): mp 86-87 °C (lit .39 86-87 °C). Allowing the reaction mixture to warm

to room temperature before neutralization resulted in a complex mixture of products.

Reaction of Sodium Phenylacetylide with N20 4

Phenylacetylene (1.00 g, 9.8 mmol) was dissolved in Et20 (40 mL). Small

pieces of sodium metal (0.24 g, 10.3 mmol) were added and the mixture was stirred

under argon for 12 h. The resulting white suspension of sodium phenylacetylide was

cooled to -78 °C and N 20 4 (11.4 mL, 1.72 M in Et 20, 19.6 mmol) was added in one

portion. The mixture was slowly warmed to room temperature. The bright yellow

suspension was poured into saturated NaHCOj (aq, 50 mL) and extracted with EtjO

(3 x 35 mL). The extracts were combined, dried over MgSO„ and concentrated via

rotary evaporator. The residue was chromatographed (SG, gradient elution with hexanes/EtOAc). Phenylacetylene (0.16 g, 16%) was isolated from the non-polar fractions and 3-benzoyl-5-phenylisoxazole (48) was isolated as a yellow solid (0.28 g,

23%). Analytically pure samples of 48 were obtained by recrystallization twice from hexanes as wispy, white needles: mp 80-81.5 °C (lit.40 89 °C); MS (Low Res) m/e 249

(M+), 105, 77, 51. A large percentage of the product did not survive column or gas

79 chromatography and could not be isolated by crystallization. FTIR from the crude

product showed peaks identical to those seen for 1,2-dinitrostyrene .43

Reaction of Lithium Phenylacetylide with N20 4 in THF

A solution of phenylacetylene (0.20 g, 1.96 mmol) in THF (10 mL) was purged

with argon and cooled to -78 °C. n-Butyllithium ( 0.86 mL, 2.27 M in hexanes, 1.96

mmol) was added followed by dropwise addition of N 20 4 (0.51 mL, 3.86 M in

hexanes, 1.96 mmol). The reaction mixture became dark immediately. The solution was

stirred at -78 °C for 10 min and the cold bath was removed. After reaching room

temperature, the mixture was poured into 10% N aX 0 3 (aq, 50 mL) and extracted with

Et20 (3 x 35 mL). The extracts were combined and dried over NajS0 4 (prolonged

storage over MgS0 4 causes decomposition of the minor product). GC/MS/IR analysis

showed only diphenylbutadiyne (33). Removal of the solvent afforded a dark red solid

(0.25 g) which was chromatographed (SG, 4:1 hexanes/EtOAc) Two products were

isolated. The less polar fraction contained 33 (0.12 g, 61%); MS (Low Res) m/e 202.

The more polar fraction contained a yellow solid (0.06 g) that, upon recrystallization, gave small yellow needles of 1-nitro-1,4, 6 -triphenyl-1,2,3-hexatrien-5-yne (42, 0.06 g,

26%): mp 145-146 °C, FTIR (KBr) 3072.0 (w), 2850.0 (w), 2210.0 (s), 2182.0 (m),

1636.0 (m), 1618.0 (m), 1596.0 (m), 1580.0 (m), 1558.0 (m). 1520.0 (m), 1490.0 (m),

1440.0 (m), 1320.0 (m), 1304.0 (m), 1098.0 (m), 1070.0 (m), 1028.0 (m), 996.0 (m),

43 Wieland, H.; Bluemich, E. Ann.Chem. 1921, 424, 100-107.

80 928.0 (m), 894.0 (m), 780.0 (m), 758.0 (s), 690.0 (s), 638.0 (m) cm 1, ‘H NMR

(CDCl3) 5 7.9 (m, 2H), 7.4 (m, 13H) ppm; ,3C NMR (CDC13) 6 135.0, 132.4, 131.5,

130.8, 130.5, 130.2, 129.7, 129.4, 128.55, 128.50, 128.3, 128.1, 121.9, 121.3, 109.3,

103.3, 87.2, 81.3 ppm; MS (High Res) m/e 349.1105 (M+) (calc. 349.1104), 335, 319,

303, 291, 276, 226, 202, 150, 105, 77; calcd for C 24H l5N 02: C, 82.51; H, 4.33; found:

C, 82.59; H, 4.36; UV max (CH 3CN) 200 (e 69880), 294 (20609), 382 nm (16760).

Reaction of Copper Phenylacetylide with N20 ,

Finely ground copper phenylacetylide (0.30 g, 1.8 mmol) was suspended in

CCI4 (10 mL) under argon. The mixture was cooled to -15 °C in an ethylene glycol/C 0 2 bath. Dinitrogen pentoxide (0.65 mL, 2.75 M in CC14, 1.8 mmol) was added dropwise. The suspension dark green immediately. After stirring for 20 min, the reaction mixture was poured into 5% NajCOj (aq, 50 mL) the mixture was filtered through Celite. The organic layer was separated and the aqueous phase was extracted with CH2C12 (2 x 25 mL). The organic extracts were combined and dried over Na^O,,.

Concentration to dryness left a yellow-brown solid (0.14 g, 77% (81% conversion)).

Purification of the product by column chromatography (SG, 4:1 hexanes/EtOAc) yielded diphenylbutadiyne (33, 0.10 g, 55%): mp 85-86 °C (lit .39 86-87 °C). The insoluble material from the reaction was heated in 20% H 2S 0 4 (aq) for 0.5 h. The acid was extracted with Et20 (3 x 20 mL). The Et20 layers were combined, washed with

81 saturated NaHCOj (aq) and concentrated in vacuo. Acetophenone ( 0.01 g) was obtained corresponding to 5% of the initial copper phenylacetylide.

Reaction of Copper Phenylacetylide with Trimethylsilyl Nitrate

Chlorotrimethylsilane (0.20 g, 1.8 mmol) was added to silver nitrate (0.34 g,

2.0 mmol) with Et30 (10 mL) under argon. The mixture was stirred overnight and then added to a suspension of finely powered copper phenylacetylide (0.30 g, 1.8 mmol) in Et20 (10 mL) at -78 “C. The reaction mixture quickly became green. The mixture was brought to room temperature, stirred for 1 h and filtered through Celite.

The filtrate was dried over NajS0 4 and concentrated by rotory evaporation to a green liquid. Column chromatography (SG, 4:1 hexanes/EtOAc) gave diphenylbutadiyne (33,

0.13 g, 43%): mp 81-83 °C (lit.3y 86-87 °C). The product was identical to an authentic sample.

Reaction of Copper Phenylacetylide with n-Propyl Nitrate

A suspension of copper phenylacetylide (0.30 g, 1.8 mmol) in dry CC1 4 (10 mL) was cooled under argon to 0 °C. n-Propyl nitrate (0.19 g, 1.8 mmol) in CC1 4 (5 mL) was added dropwise. There was no immediate reaction and thus the mixture was brought to room temperature and stirred overnight. Because there still was no reaction, pyridine (2 mL) was added to increase the solubility of the copper acetylide. The mixture quickly became dark. After stirring 1 h, the mixture was poured into water (50

82 mL) and CH 2C12 (15 mL), The organic layer was separated and washed with 10% HCt

(aq, 50 mL) and 5% NaX0 3 (aq, 50 mL), dried over Na^SO^, concentrated and chromatographed (SG, 4:1 hexanes/EtOAc) to give diphenylbutadiyne (33, 0.02 g,

11%).

Reaction of Phenylethynyl Zinc Chloride with N20 4

Phenylacetylene (0.20g, 2.0 mmol) was dissolved in THF (5 mL) and placed in a flame dried flask under argon. The solution was cooled to -78 °C, n-BuLi (1.7 mL,

1.18 M in hexanes) added and then anhydrous ZnCl 2 (0.28 g, 2.0 mmol) in THF (3 mL) was added. The mixture was briefly warmed to room temperature and then recooled to -78 °C. After addition of N 20 4 (0.82 mL, 2,4 M in Et20) dropwise and warming to room temperature in 1 h, the reaction mixture was poured into 5% N a^O j

(aq, 50 mL) and extracted with Et30 (3 x 25 mL). The Et20 layers were combined, washed with brine and concentrated in vacuo to leave a yellow liquid (0.19 g) which was separated by column chromatography (16 g SG, 3% EtOAc in hexanes). Two products were isolated: diphenylbutadiyne (33, 0.04 g, 20%) and phenylacetylene (37,

0,15 g, 76%). GC/MS/IR analysis of the reaction mixture before aqueous workup also shows phenylacetylene (37) indicating that phenylacetylene radical (35) abstracted a hydrogen from the solvent.

83 Reaction of Phenylethynyl Zinc Bromide with N20 4

Phenylacetylene (0.20 g, 2.0 mmol) in THF (10 mL) was cooled to -78 °C

under argon and n-BuLi (1.7 mL, 1.2 M in hexanes) was added followed by anhydrous

ZnBr 2 (0.44 g, 2.0 mmol). After warming the above solution to 0 °C for 10 min and

recooling, N 20 4 (0.82 mL, 2.4 M in Et20) was added dropwise. The mixture was

brought to room temperature, poured into 5% Na 2C 0 3 (aq, 50 mL) and then extracted

with Et20 (3 x 25 mL). The combined extracts were washed with brine, dried over

M gS0 4 and concentrated to an orange liquid ( 0.22 g). Column chromatography (16 g

SG, 5% EtOAc in hexanes) resulted in separation of diphenylbutadiyne (33, 0.04 g,

20%) and phenylacetylene (37, 0.15 g, 76%).

Reaction of Phenylethynyl Zinc Iodide with N20 4

A solution of phenylacetylene (0.20 g, 2.0 mmol) in Et20 (10 mL) was flushed with argon. The mixture was cooled to -78 °C, n-BuLi (1.7 mL, 1.2 M in hexanes) and then anhydrous Znl 2 (0.63 g, 2.0 mmol) in THF (2 mL) were added. The solution was briefly warmed to room temperature and then recooled to -78 °C. One equivalent of

N20 4 (0.63 mL, 3.1 M in Et 20) was added dropwise. The solution turned yellow-green immediately. The reaction mixture was warmed to room temperature in 15 min and filtered through a short plug of SG. The solution became purple colored from iodine.

The iodine was removed by reaction with 10% NaHSOj (aq, 50 mL). Drying and concentrating the organic layer yielded an orange liquid (0.44 g). The products were

84 determined by GC/MS/IR: diphenylbutadiyne (33,17%) and iodo(phenyl)acetylene (44,

74%): products were identical to authentic samples.

Reaction of Lithium Trimethylsilylacetylide and Nj0 4

A solution of Et20 (10 mL) and trimethyl si lylacetylene (0.20 g, 2.0 mmol) was flushed with argon and cooled to -78 °C. n-Butyllithium (0.90 mL, 2.27 M in hexanes,

2.0 mmol) was added followed by N 20 4 ( 1.6 mL, 1.24 M in Et 20 , 2.0 mmol), the solution was stirred for 1 h at -78 °C and then poured cold into 5% NajC0 3 (aq, 50 mL). The only product detected by GC/MS/IR was bis-(trimethylsilyl)butadiyne (38,

44%, GC yield) The organic layer was separated and the Et20 was removed by distillation (the remaining trimethylsilylacetylene (39) generated would have distilled along with the E^O). The distillate was treated with AgNOj in EtOH/H 20. The white precipitate of disilver acetylide obtained was filtered and washed with H 20, EtOH and

Et20. After drying, the silver acetylide weighed 0.12 g and thus corresponds to 0.05 g of trimethylsilylacetylene (39, 25%). Bis-(trimethylsilyl)butadiyne (38) was isolated by preparative GLC: FTIR (gas phase): 2967 (w), 2907 (w), 2064 (m), 1261 (w), 850

(s), 648 (w) cm'1; ‘H NMR (200 MHz, CDC13) 5 0.16 (s, 18H) ppm; MS (Low Res) m/e 194 (M+), 179, 163, 149, 121, 97, 73, 67, 32.44

44 Spectra identical to those in the literature: (a) Nakovich, J.; Shook, S.D.; Miller, F A. Spectrvchem. Acta 1979 , 35A, 495. (b) Walton, D.R.M.; Waugh, F.J. J. Organometal. Chem. 1972 , 37, 45.

85 Reaction of Lithium* 1-Pentyne with N20 4

1-Pentyne (0.50 g, 7.4 mmol) was dissolved in EtjO (10 mL) and cooled under

argon to -78 °C. n-Butyilithium (5.6 mL, 1.31 M in hexanes, 7.4 mmol) was added

followed by N 20 4 (2.6 mL, 2.85 M in Et 20, 7.4 mmol). After stirring at -78 °C for 10

min, chlorotrimethylsilane (1 mL) was added to quench any remaining lithium-1-

pentyne. After warming to room temperature over 1 h, the reaction mixture was poured

into 5% NajCOj (aq, 50 mL) and extracted with Et20 (2 x 30 mL). The extracts were

combined, dried over MgS0 4 and analyzed by GC/MS/IR. The sole product was 4,6-

decadiyne (40, 0.151 g, 30.4%). No trace of 1-trimethylsilyl-1-pentyne was seen

indicating that all of the lithium-1-pentyne had been consumed. The reaction mixture

was treated with AgNOj in EtOH/H20 to precipitate out any 1-pentyne (41) as silver-1-

pentynide. The white precipitate was filtered, washed with H20, EtOH and Et 20 . After

drying, the solid weighed 0.73 g corresponding to 0.28 g of 1-pentyne (41, 57%). 4,6-

Decadiyne (40) was isolated by preparative GLC: 'H NMR (200 MHz, CDCIj) 5 2.20

(t, J = 7 Hz, 4H), 1.52 (q, J = 7 Hz, 4H), 0.96 (t, J = 7 Hz, 6 H); MS (Low Res) m/e

134, 117, 105, 91, 77, 63, 51, 32.45

45 Spectra were identical to those in the literature: Hannah, D.J.; Smith, R.A.J.; Teoh, I.; Weavers, R.T, Aust. J. Chem. 1981, 34, 181

86 Preparation of Phenyl((trimethylsilyl)ethynyl)sulfone

Phenyl-2-(trimethylsilyl)ethynyl sulfone was prepared by a literature procedure .46 In an Erlenmeyer flask was mixed aluminum trichloride (9.12 g, 68.4 mmol) and CH 2C13 (60 mL). Benzene sulfonyl chloride (12.09 g, 68.4 mmol) was added and the mixture maintained at room temperature for 15 min. The yellow solution was filtered through glass wool, under argon into an addition funnel. The addition funnel was placed on a round bottom flask charged with bis-(trimethylsilyl)acetylene

(10.60 g, 62.2 mmol). The flask was cooled to 0 °C and the solution in the addition funnel was added dropwise. After the addition was complete, the mixture was stirred at room temperature for 12 h and then was poured into a slurry of dilute HC1 and crushed ice. The organic layer was separated and washed with H20 (2 x 100 mL), dried over Na^O* and concentrated in vacuo to leave a dark liquid (15.01 g). The residue was fractionally vacuum distilled (94-145 °C @ 0.85 mm Hg). The highest boiling fraction was crystallized from PE at -25 °C to give white needles of phenyl((trimethylsilyl)ethynyl)sulfone (5.18 g): mp 55-58 °C. Two further recrystallizations gave white needles (4.59 g): mp 65-67 °C (lit, 65-66 °C).

Preparation of Ethynyl(phenyl)sulfone (109)

The following literature procedure for preparing ethynyl(phenyl)sulfone was followed .1 An aqueous buffer solution (10.6 mL) of K 2C 0 3 (6.2 x 10 "3 M) and KHCOj

46 Bhattacharya, S.N.; Josiah, B.M.; Walton, D.R.M. Organometal. Chem. Syn. 1970 / 1971 , 7 , 145-149.

87 (6.2 x 10 3 M) was added to a solution of phenyl((trimethylsilyl)ethynyl)sulfone (2.42

g, 10 mmol) in MeOH (30 mL) at 0 °C. After 20 min, the reaction was acidified with

10% HC1 (aq) and extracted with CHC1 3 (3 x 25 mL). The extracts were combined,

dried over Na 2SO< and distilled. The product, ethynyl(phenyl)sulfone (109) came over

cleanly at 104 °C @ 0.4 mm Hg. FTIR (NaCl) 3247.6 (m), 2918.4 (w), 2068.3 (m),

1448.0 (m), 1336.0 (s), 1164.9 (s), 1087.6 (m), 738.5 (s), 684,9 (s), 574.8 (m) cm 1.

Reaction of Lithium Ethynyl(phenyl)sulphone with N20 4 in THF

Ethynyl(phenyl)sulphone (0.20 g, 1.2 mmol) in THF 47 (10 mL) was cooled

under argon to -78 °C and n-BuLi (0.53 mL, 2.27 M in hexanes, 1.2 mmol) was added dropwise. Dinitrogen tetroxide (5.7 mL, 0.21 M in Et 20 , 1.2 mmol) was added to the suspension. The reaction mixture quickly became dark. The cold bath was removed and the mixture brought to room temperature. TLC showed only very polar material. The flask was emptied into 10% HC1 (aq, 50 mL). The mixture was filtered, washed with

H20 and acetone and dried at 250 °C to leave a black amorphous solid (0.021 g). The filtrate was extracted with Et20 (3 x 20 mL). The Et20 extracts were combined, washed with brine and dried over MgS04. Concentration of the solution gave a partially crystallized orange oil (0.045 g). GC/MS/IR analysis shows three products: diphenyl sulphoxide (113, 84%), diphenyl disulphide (114, 7%) and S-phenyl benzenesulphonothiolate (115, 7%). No nitroacetylenes or butadiynes were detected.

47 Using Et20 as solvent results in phenyl(ethynyl)sulfone in 95% yield.

88 Reaction of Lithium Methyl Propiolate and N20 4

n-Butyllithium (4.6 mL, 1.31 M in hexanes, 6.0 mmol) was added to methyl

propiolate in Et20 (5 mL) and THF (10 mL) at -100 °C under argon. After a few

minutes, N 20 4 (2.1 mL, 2.85 M in Et20, 6.0 mmol) was added dropwise. The solution

changed from yellow to orange. After 5 min, the reaction mixture was warmed to room temperature, poured into 5% NaHCOj (aq, 50 mL) and extracted with EtjO (2 x 50

mL). The product mixture contained mostly methyl propiolate (0.10 g, 20%).

Preparation of Bis-(Phenylethynyl)mereury

A procedure by Johnson and McEwen was used for preparation of bis-

(phenylethyny!)mercury.48 Mercuric chloride (5.10 g, 19 mmol) was dissolved in a solution of potassium iodide (12.6 g, 76 mmol) in H20 (13 mL) Addition of sodium hydroxide (10% aqueous, 9,6 mL) caused an orange precipitate to form. After the mixture was stirred for 20 min, all solids dissolved and a yellow solution remained.

Phenylacetylene (1.93 g, 19 mmol) in EtOH (25 mL) was added in one portion. A colorless solid immediately precipitated. The precipitate was filtered, recrystallized from EtOH (40 mL) and filtered hot. Brilliant white crystals of bis-

(phenylethynyl)mercury (0,90 g) were filtered and washed with a small amount of

EtOH. A second crop was obtained from the mother liquor by concentration and

48 Johnson, J.R.; McEwen, W.L. J Chem. Soc. 1926, 48, 469-476.

89 recrystallization from EtOH. The combined yield of all crops was 3.5 g (92%): mp

118-120 °C (lit. 124.5-125 °C).

Reaction of Bis-(PhenylethynyI)mercury with N20 4 in EtjO

Dinitrogen tetroxide (0.32 mL, 3.13 M in Et 20) was added dropwise to bis-

(phenylethynyl)mercury (0.20 g, 0.50 mmol) in Et20 (10 mL) stirred at -78°C under argon. Addition of the N 20 4 solution caused immediate formation of a white precipitate. After warming to room temperature over 0.5 h, the heterogenous reaction mixture became yellow. The mixture was quickly filtered through a three inch plug of

SG and the solvent was removed under reduced pressure. The yellow residue (0.13 g,

> 99%) was analyzed by GC/MS/IR and found to be almost exclusively benzoyl cyanide (54): FTIR (gas phase) 3080 (w), 2218 (nitrile, w), 1700 (carbonyl, s), 1598

(w), 1451 (w), 1244 (s), 1180 (w), 980 (m), 699 (m) cm 1; MS (Low Res) m/e 131

(M+), 105 (M+-CN), 77, 51. Spectra are identical to those for a known sample.

Reaction of Bis-(PhenyIethynyl)mercuiy with Nz0 4 in CHCT,

A stirred solution of bis-(phenylethynyl)mercury (0.20 g, 0.50 mmol) in CHC1 3

(10 mL) was cooled under argon to -40 °C and N 20 4 (1.4 mL, 0.70 M in CHC13) was added dropwise. The reaction mixture became bright yellow immediately. The mixture was slowly brought to room temperature by which time the solution had become olive in color. After stirring overnight, the reaction mixture was concentrated onto SG and

90 chromatographed (SG, 4:1 hexanes/EtOAc). Acetophenone (58, 0.09 g, 76%) was

isolated as a slightly yellow liquid identical to a known sample: FTIR (gas phase)

3078, 1720, 1384, 1281 cm 'H NMR (200 MHz, CDC13) 8 7.4 (m, 5H); 2.6 (s, 3H)

ppm; MS (Low Res) m/e 120, 105, 77, 51,

Reaction of Bis-(Phenylethynyl)mercuiy with NOjBF4

Bis-(phenylethynyl)mercury (0.20 g, 0.50 mmol) was dissolved in CH 2Cl2 (10

mL) and cooled under argon to -78 °C. Freshly cleaned and dried N 0 2BF4 (0.13 g, 1.00

mmol) was added in one portion. After a few minutes, the reaction mixture became

orange and then darkened slowly. TLC showed only one product. The dark mixture

was brought to room temperature, filtered through a short plug of SG and washed

through with CHC13 (50 mL). The filtrate and washings on concentration yielded

acetophenone (58, 0.12 g, > 99%). The product was assigned and determined to be

pure by GC/MS/IR.

Reaction of Bis-(Phenyiethynyl)mencuiy with N 02BF4 in 1,4-Dioxane

Bis-(phenylethynyl)mercury (0.27 g, 0.68 mmol) was added all at once to

freshly cleaned N 0 2BF4 (0.18 g, 1.4 mmol) suspended in 1,4-dioxane (10 mL). The

mixture became yellow-green in a few seconds. Minutes later, the mixture became brown and a precipitate formed. The mixture was stirred at room temperature for 1 h and then concentrated at 1 mm Hg. Two products (0.05 g) were found by TLC. The

91 two products did not separate well by column chromatography and therefore the mixture was analyzed by GC/MS/IR. Acetophenone (58) and benzoyl cyanide (54) were found in a 1.6 : 1 ratio.

Reaction of lithium Phenylacetylide Cuprate with N20 4

To phenylacetylene (0.20 g, 2.0 mmol) in Et^O (10 mL) was added n-BuLi

(0.86 mL, 2.27 M in hexanes) at -78 °C. Copper phenylacetylide (0.16 g, 1.0 mmol) was then added in one portion and the mixture was allowed to come to room temperature overnight. The bright yellow color of copper phenylacetylide disappeared and nearly everything went into solution. The solution was cooled to -78 °C and N 20 4

(0.57 mL, 1.73 M in hexanes) was added. The mixture immediately became dark and contained a yellow suspension. After 10 min, the reaction mixture was filtered cold through Celite and washed well with CH2C12. The filtrate was dried over anhydrous

K2COj and on concentration to dryness, afforded diphenylbutadiyne (33, 0.14 g, 71%) as a yellow solid. Recrystallization from EtOH/H20 33 (0.10 g) as colorless needles: mp 83.5-85 °C

92 Preparation of Phenyl(trimethylsilyl)acetylene

n-BuLi (9.1 mL, 2.27 M in hexanes) was added slowly to phenylacetylene (2.0 g, 20 mmol) in THF (15 mL) at 0 °C under argon. After stirring for 15 min, the dark solution was treated with chlorotrimethylsilane (2.6 inL, 21 mmol) and stirred overnight. The light colored solution was poured into aqueous NH4CI (50 mL, 10 %) and extracted with Et20 (3 x 35 mL). The extracts were combined, washed with brine and dried over M gS04. Concentration on the rotary evaporator gave a yellow-brown liquid (3,8 g). Short path distillation (86 °C @ 5 mm Hg) yielded colorless phenyl(trimethylsilyl)acetylene (2.14 g, 61%) Spectra match those reported in the literature:49 FTIR (NaCl) 2159.1 (w), 1249.6 (s) cm 1; lH NMR (200 MHz, CDC13) 8

7,4 (m, 2H), 7.3 (m, 3H), 0.2 (s, 9H) ppm.

Reaction of Phenyl(trimethylsilyl)acetylene and N 02BF4

Clean N 0 2BF4 (0.15 g, 11 mmol) was added in one portion to pheny[(trimethylsilyl)acetylene (0.20 g, 11 mmol) in CH3CN (10 mL) under argon. A water bath was used to control the slightly exothermic reaction. The reaction mixture immediately turned yellow and a slight but steady bubbling occurred. After the bubbling stopped, TLC and GC/MS/IR showed an appreciable amount of unreacted starting material (-19%). GC analysis showed the major component of the mixture to

49 Seyferth, D.; Vaughen, L.G.; Suzuki, R. J. Organomet. Chem. 1964, 1, 437.

93 be the starting acetylene. Several unidentified compounds were also detected - none of which showed -N03.

Preparation o f Phenyl(trimethylstannyl)acetylene

Phenylacetylene (2.0 g, 20 mmol) was added to THF (20 mL). The solvent was flushed with argon, cooled to -78 °C and n-BuLi (8.7 mL, 2.27 M in hexanes) was added dropwise. After the solution had been stirred for 15 min, freshly distilled trimethylstannyl bromide (4,83 g, 20 mmol) in THF (10 mL) was added dropwise. The yellow solution was brought to room temperature slowly and then stirred overnight.

The reaction mixture was poured into 10% NH 4C1 (aq, 100 mL) and extracted with

EtjO (3 x 50 mL). The Et20 layers were combined, washed with brine, dried over

M gS0 4 and concentrated in vacuo to yield a yellow liquid (6.06 g). Short path distillation gave a single fraction of phenyl(trimethylstannyl)acetylene 50 (3.61 g, 70%);

FTIR (NaCl) 2137.4 cm '; 'H NMR (200 MHz, CDC13) 8 7.4 (m, 2H), 7.3 (m, 3H),

0.34 (s, 9H) ppm.

Reaction of Phenyl(trimetfaylstannyl)acetylene with N 03BF4

This experiment is a reinvestigation of a known reaction .51

Phenyl(trimethylstannyl)acetylene (0.46 g, 1.7 mmol) was added at room temperature

50 Jones, K.; Lappert, M.F. Proc. Chem. Soc. 1964, 22.

51 Kashin, A N; Bumagin, N.A.; Bessonova, M.P.; Beletskaya, I P.; Reutov, O.A. Zhumal Obshchei Khimii 1980, 16, 1345 (Eng. trans. p. 1153).

94 to freshly cleaned N 0 2BF4 (0.23 g, 1.7 mmol) in CH3CN (10 mL). The reaction mixture immediately became dark red and warmed slightly. After 0.5 h, TLC showed a complex mixture that was then analyzed by GC/MS/IR. The mixture contained mostly phenylacetylene (37) with 3-benzoyl-5-phenylisoxazole (identical to a known sample) (48, 5%)52 and traces of benzonitrile (55), nitrobenzene and nitro(phenyl)acetylene(lc): FTIR (gas phase) 3080,2219, 1701, 1542, 1353, 1249, 701 cm '; MS (Low Res) m/e 147, 117, 101, 75, 51.

Reaction of Pbenyl(trimethylstannyl)acetylene with N2Os

Phenyl(trimethylstannyl)acetylene (0.50 g, 1.9 mmol) was dissolved in CH 2C12 under argon. The solution was cooled to -60 °C and N 2Os (0.69 mL, 2.75 M in CC14) was added. The solution instantly became dark. TLC of the cold reaction mixture showed mostly one product with traces of several others. After 10 min, the cold bath was removed and the reaction solution was warmed to room temperature. TLC looked the same after warming. GC/MS/IR of the mixture showed mostly 3-benzoy 1-5- phenyl isoxazole (48) along with small amounts of phenylacetylene (37), benzonitrile

(55), benzoyl cyanide (54), benzoic acid and other unidentified trace components to be present. The solution was concentrated onto SG and purified by column chromatography (SG, 4 :1 hexanes EtOAc). 3-Benzoyl-5-phenylisoxazole (48) was isolated (0.09 g, 38%). Spectra and retention times match those of known samples.

S2 The authors of the original report incorrectly assigned the structure of this product as l-phenyl-2,2-dinitro-3-cyano-l -propanone.

95 Reaction of Phenyl 2-(Trimethylsilyl)ethynyl Sulfone with N 02BF4

Nitronium tetrafluoroborate (0.17 g, 1.3 mmol) was added in one portion to

phenyl 2-(trimethylsilyl)ethynyl sulfone (0,30 g, 1.3 mmol) in CH3CN (10 mL). The

reaction mixture became warm and bubbled. After the bubbling subsided, the mixture

was concentrated and chromatographed (SG, 4:1 hexanes/EtOAc). Two products were

isolated: nitrobenzene (0.03 g, 15%): MS (Low Res) m/e 123, 77; and

ethynyl(phenyl)sulfone (0.15 g, 72%): FTIR (NaCl) 3247.6 (m), 3067.8 (w), 2918.4

(m), 2068.3 (m), 1448.0 (m), 1336.0 (s), 1164.9 (s), 1087.6 (m), 738.5 (m), 684.9 (m),

574.8 (m), lH NMR (200 MHz, CDC13) 6 7.9 (m, 2H), 7.6 (m, 3H), 3.6 (s, 1H) ppm.

Preparation o f Ethyl 3-Trimethylsilylpropiolate

To n-BuLi (32.4 mL, 0.94 M in hexanes) at 0 °C was added

trimethylsilylacetylene (3.0 g, 3.1 mmol) in Et20 (50 mL) under argon. The reaction

mixture was stirred at 0 °C for 15 min and then cooled to -78 °C. Distilled ethyl

chloroformate (3.35 g, 30.9 mmol) was added dropwise. The reaction solution was

slowly brought to room temperature, poured into H20 (100 mL) and extracted with

Et20 (2 x 50 mL). The ether layers were combined, washed with H20 (50 mL) and

brine and then dried over M gS04. The extract was concentrated and the residue was

vacuum distilled (1 mm Hg). The fraction distilling at 90 °C crystallized on cooling.

Recry stall ization from PE at -78 °C afforded white needles of ethyl 3-

96 tnmethylsilylpropiolate (5.2 g, 63%); FTIR (NaCl) 2164.8, 1713.2 cm'1; 'H NMR (200

MHz, CDClj) 5 4.2 (t, 2H); 1.3 (d, 3H); 0.20 (s, 9H) ppm.

Reaction of Ethyl 3-Trimethylsilylpropiolate with NOxBF4

Ethyl 3-trimethylsilylpropiolate (0.263 g, 1.55 mg) was dissolved in dry acetonitrile (10 mL) in a 25 mL round bottom flask. The reaction flask was purged with argon and placed in a water bath. Clean N 0 2BF4 (0.21 g, 1.55 mmol) was added in one portion. The solution immediately became dark red. TLC showed that the starting material was consumed completely and only very polar material remained. The reaction mixture was quickly flushed through a short plug of SG with CHC13, CH 2Cl2 and EtOH. The fractions were combined and concentrated in vacuo to leave a thick red-brown oil (0.374 g): analysis showed no 1-nitroacetyfenes.

Preparation of l-Bromo-2-ethoxyethylene

A literature procedure by Stork and Tomasz was followed .53 A 500 mL 3-neck round bottom flask was charged with freshly distilled N,N-diethylaniline (200 mL) and a stirbar. One neck of the flask was equipped with a 10 cm vigreux column with distillation head, condenser, vacuum adapter and 100 mL receiver. One other neck was equipped with a 250 mL addition funnel. The final neck was stoppered. The flask was heated to 95 °C and evacuated to 20 mm Hg. A solution of 1,2-dibromo-l-

53 Stork, G.; Tomasz, M. J. Chem. Soc. 1964, 86, 475

97 ethoxy ethane was added dropwise from the addition funnel. The l-bromo-2-

ethoxyethylene distilled over as formed. Redistilled (30-50 °C @ 20 mm Hg) yielded

pure l-bromo-2-ethoxyethylene: 28.55 g(30.2%); FTIR(NaCl) 3107.1 (w), 2980.5 (m),

2932.6 (w), 2885.4 (w), 1643.4 (s), 1392.7 (m), 1319.3 (m), 1230.3 (s), 1170.1 (m),

1104.4 (s), 693.5 (m) cm 1,

Synthesis of Ethoxyacetylene^4

l-Bromo-2-ethoxyethylene (10 g, 66 mmol) was added to powdered KOH (20

g). The mixture was heated to 110 °C. Ethoxyacetylene began to distill at 95 °C and

was collected at -78 °C. The product was dried over NaS0 4 and redistilled through a

short column (27.5-28.5 °C @ 300 mm Hg): 2.16 g (47%).

Synthesis of Ethoxy(trimethylsilyl)acetylene

Ethoxyacetylene (1.54 g, 22 mmol) was added dropwise to n-BuLi (21.2 mL,

0.94 M in hexanes) in dry THF (12 mL), keeping the temperature below -20 °C.

Chlorotrimethylsilane (2.17 g, 20 mmol) was then added slowly at -20 °C. The cooling

bath was removed and the reaction was stirred at room temperature for 3.5 h.

Triethylamine (0.25 mL) was added and the reaction mixture was poured into brine (50 mL). The organic layer was separated, and the aqueous layer was extracted with Et20

(2 x 50 mL). The extracts were combined, dried over M gS0 4 and concentrated. The

54 Jacobs, T.L.; Cramer, R.; Hanson, J.E. J. Chem. Soc, 1942, 64, 223-226.

98 residue was distilled through a short vigreux column (50 °C @ 20 mm Hg). The purest fractions were combined to give ethoxy(trimethylsilyl)acetylene 55 (1.26 g, 44%); FTIR

(NaCl) 2958.8 (m), 2934.8 (m), 2874.0 (w), 2176,4 (m), 1249.2 (m), 841.9 (s), 759.5

(m), 639.5 (w) cm'1.

Reaction of Ethoxy(trimethylsilyl)acetylene with NOjBF4

l-Ethoxy-2-trimethylsilylacetylene (0,15 g, 1.1 mmol) was dissolved in CH 2C12

(15 mL) and CH3CN (15 mL). This solution was added dropwise to N 0 2BF4 (0.14 g,

1.1 mmol) in CH3CN (10 mL) at -60 °C under argon. The mixture became yellow and was brought to room temperature slowly. The reaction mixture was then filtered through a short plug of SG and concentrated under reduced pressure to afford a yellow-green oil (0.17 g). TLC showed at least seven products. The mixture was analyzed by GC/MS/IR and found to contain no 1-nitroacetylenes.

NLICLEOPHIL1C APPITION-ELIMINATION APPROACH

Reaction of Diiodoacetylene (119) with Silver Nitrite

Freshly prepared silver nitrite (0.22 g, 1.44 mmol) was added to a 25 mL 3- neck round bottom flask equipped with a gas buret, stopper and an addition funnel

55 Shchukovskaya, L.L.; Pal'chik, R.I.Izv. Akad. Nauk SSSR, Ser. Khim. 1964, 12, 2228 (Engl, trans. 2129).

99 charged with diiodoacetylene (119)5S (0.20 g, 0.72 mmol) in CH3CN (5 mL). The entire

apparatus was flushed with argon. The diiodoacetylene solution was added as quickly as possible causing immediate bubbling and formation of a white precipitate. The evolved gases displaced 9.0 mL of water (corresponding to 0.40 mmol of gas) in the buret, GC/MS/IR analysis of the gases showed COi( N 2 and NO in roughly a 2:5:5 ratio. The white precipitate was filtered off (0.253 g). The light-sensitive solid was insoluble in H 20 , H3P 0 4 (50% aq, does not color KJ/starch paper) and c. NH 4OH.

KCN (aq) causes immediate bubbling and dissolution. FTIR showed very little transmittance. If the white ppt was not filtered off, after several hours the white precipitate converted to silver iodide (0.161 g).

Preparation of [Hydroxy(tosyloxy)iodo] benzene57

p-Toluenesulfonic acid (7.61 g, 40.0 mmol) was dissolved in a minimum amount of CH3CN and added to a suspension of iodobenzene diacetate (6.44 g, 20.0 mmol) in CH3CN (45 mL). The solution turned yellow almost immediately and a white solid precipitated. After 10 min, the precipitate was filtered and washed with acetone and then Et20 to remove any p-toluenesulfonic acid and acetic acid. The fluffy white solid, [hydroxy(tosyloxy)iodo]benzene, was air-dried: 6,02 g (77%); mp 141-143 °C.

56 Dehn, W.H. J. Am. Chem. Soc 1911, 33, 1598.

57 Koser, G.F., Wettach, R.H. J. Org. Chem. 1977, 42, 1476.

100 Preparation of Phenylethynyl(phenyl)iodoiiiiun Tosylate (64)S!

Phenylacetylene (7.98 g, 78.0 mmol) was added to

[hydroxy(tosyloxy)iodolbenzene (5.00 g, 12.7 mmol) dissolved in CHC1 3 (15 mL) and the solution was refluxed for 20 min. The resulting orange-red mixture was dried over

NajSO,, overnight, filtered and concentrated. The residue was taken up in warm Et20

(10 mL) and allowed to crystallize while stirring for 2 h. The yellow paste was filtered and washed with Et^O until a white solid, phenylethynyl(phenyl)iodonium tosylate

(64), remained: 4.17 g (69%), mp 128-130 °C (lit .57 119-122 °C).

Reaction of Phenylethynyl(phenyl)iodoniiim Tosylate (64) with Sodium Nitrite

Phenylethynyl(phenyl)iodonium tosylate (0.30 g, 0.63 mmol) was dissolved in

CHClj (10 mL). A solution of sodium nitrite (0.43 g, 6.3 mmol) in H20 (10 mL) was added in one portion and the two-phase mixture was stirred vigorously for 3 d. TLC showed a streak and two spots. GC/MS/IR showed two major products: iodobenzene

(81%) and benzonitrile (55, 45%). There was no evidence for nitro(phenyl)acetylene

(lc). The iodobenzene was easily separated by column chromatography (SG, 4:1 hexanes/EtOAc) but the benzonitrile (55) was impure compared with an authentic sample: FTIR (gas phase) 3083 (w), 2235 (m), 1492 (m), 738 (s), 889 (s), 543 (s) cm'1;

MS (Low Res) m/e 103, 76, 50.

58 Rebrovic, L.; Koser, G.F. J. Org. Chem. 1984, 491 4700-4702.

101 GENERATION AND FATE OF NITROSOKETENE

Preparation of the Sodium Salt of 5-Hydroxyimino-2,2-dimethyl-1 ,3-dioxane-4,6-dione

Hydrate

The hydroxyiminodione salt was made according to the literature .59 Sodium

nitrite (2.90 g, 42 mmol) in H20 (10 mL) was added to a solution of Meldrum’s acid

(6,00 g, 40 mmol) in MeOH (60 mL). The mixture turned red immediately. The

solution was stirred for 2 h and then concentrated to -30 mL in vacuo at room

temperature. The product was crystallized by cooling in an ice bath and scratching the

flask with a glass rod. The orange solid was filtered, recrystallized from EtOH and

washed with Et20. The sodium 4,6-dione monohydrate obtained was a peach powder:

4.63 g (53%).

Preparation of 5-Hydroxyimino-2,2-dimethyl-lT3-dioxane-4,6-dione (78)59

Nitric acid (12 M) was added dropwise to a solution of the sodium salt of 2,2-

dimethyl-5-hydroxyimino-l,3-dioxane-4,6-dione hydrate (4.5 g, 21 mmol) in H20 (40

mL) at 0 °C until the solution becomes slightly yellow. The aqueous solution was

extracted with Et20 (3 x 100 mL) and iso-amyl alcohol (50 mL). The organic extracts

were combined, dried over MgS0 4 and concentrated on a rotary evaporator at 2,5 mm

Hg. The yellow residue was taken up in Et20 (50 mL) and PE (75 mL) was added.

59 Eistert, B.t Geiss, F. Chem Ber. 1961, 94, 929.

102 The oxime slowly crystallized and was filtered and washed with PE. 2,2-Dimethyl-5- hydroxyimino-l,3-dioxane-4,6-dione (78) was obtained as colorless crystals: 1.14 g

(30%), mp 103-105 °C (lit.59 107-109 °C), FTIR (KBr) 3447.7 (m, br), 2972.8 (m),

2931.8 (w), 1702.2 (s), 1364.0 (m), 1179.9 (m) cm1.

Decomposition of Nitrosoketene (77)

5-Hydroxyimino-2,2-dimethyl-l,3-dioxane-4,6-dione (0.14 g, 0.87 mmol) was placed in a 5 mL round bottom flask equipped with a gas outlet connected by Tygon tubing to a bubbler filled with aqueous KOH (10%). The flask was heated with a heat gun to melt the 4,6-dione. The dione bubbled as it melted (103-105 °C). The alkaline solution in the trap became yellow-brown. After decomposition of the initial dione was complete, the trap was removed. Saturated aqueous ferrous ammonium sulfate (aq, 2 drops) and 30% potassium fluoride (aq, 2 drops) were added to a 1 mL aliquot. The mixture was heated to reflux for 30 s, cooled and treated dropwise with 30% H 2S 0 4

(aq). A dark blue precipitate fell from the black solution after a few drops of the acid were added. The Prussian blue color indicates the presence of cyanide ion .60

60 Shriner, Fuson, Curtin The Systematic Identification of Organic Compounds - A Laboratory Manual, 5th Ed.; 63.

103 ATTEMPTED GENERATION AND STUDY OF PHENYIiNITROlKETENE f80. R

Preparation of trans-P-Pyrrolidinostyrene61

Pyrrolidine (18.96 g, 0.267 moi) was added to a solution of phenylacetaldehyde

(16.00 g, 0.133 mol) in benzene (20 mL), MgS04 was added and the mixture was

stirred for 30 min. The MgS04 was filtered and the solvent removed in vacuo. The

residue was distilled via Kugelrohr (145 °C @ 0.5 mm Hg) to yield trans-p- pyrrolidinostyrene (16.68 g, 72%) as a thick yellow liquid: FTIR (NaCl) 3020 (w),

2968 (w), 2837 (w), 1636 (m), 1597 (m), 1378 (m), 1030 (s) cm 1; lH NMR (CDC13)

5 7.2 (Ar-H, m, 4H), 7.1 (vinyl-H, d, Ja,b = 14 Hz, 1H), 7.0 (Ar-H, m, 1H), 5.1

(vinyl-H, d, Ja,b = 14 Hz, 1H), 3.2 (pyr-H, m, 4H), 1.9 (pyr-H, m, 4H) ppm.

Preparation of Benz aldehyde Oxinte Chloride62

A stirred solution of benzaldehyde oxime (30.00 g, 0.248 mol) in CHC13 (150 mL) was cooled in an ice bath. Chlorine gas was introduced slowly through a fritted glass bubbler. After overnight chlorination, the initial green color disappeared and the solution became yellow. The solvent was removed at reduced pressure to give a yellow oil. Crystallization was effected with pentane at -25 °C. Colorless crystals of

61 Cragg, J.E.; Herbert, R.B.; Jackson, F.B ; Moody, C.J.; Nicolson, I T. J. Chem. Soc. Perkins Treats. I 1982, 2477.

62 Werner, A., Buss, H. Chem Ber. 1894, 27, 2197.

104 benzaldehyde oxime chloride were collected by filtration (17.43 g , 45%): mp 46-48

°C (lit.62 48 °C).

Preparation of 3,4-Diphenylisoxazole63

To benzaldehyde oxime chloride (3.12 g, 20 mmol) in Et20 (50 mL) at 0 °C

was added trans-J3-pyrrolidinostyrene (7.0 mL, 40 mmol) and triethylamine (4.0 mL)

in Et20 (20 mL) over 10 min. After stirring at room temperature for 2 h, the reaction

mixture was diluted with Et20 and washed with H20. The Et20 layer was washed with

brine and dried over MgSO^. Evaporation of the solvent left a wet, yellow solid. The

residue was vacuum distilled (bp 140-160 °C @ 8 mm Hg). Fractions containing product were combined, concentrated and recrystallized twice from EtOH/H20. After

drying, colorless crystals of 3,4-diphenylisoxazole (2.72 g, 47%) were obtained: mp

85.5-86.5 °C (lit.63 88-90 °C); lH NMR 8 8.52 (s, 1H), 7.36 (m, 10H) ppm.

Preparation of Phenyl(trimethylsilyl)ketene (90)64

To a stirred solution of 3,4-diphenylisoxazole (1.50 g, 6.79 mmol) in THF (10 mL) at -60 °C was added n-BuLi (2.85 mL, 2.38 M in hexanes) under argon.

Chlorotrimethylsilane (0.81 g, 7.48 mmol) in THF (3 mL) was then added via syringe.

After 0.5 h, the mixture was warmed to room temperature. The solvent was removed

63 Bast, K,; Christl, M.; Huisgen, R.; Mack, W.; Sustmann, R. Chem. Ber. 1973, 106, 3258.

64 Hoppe, I.; Schijllkopf, U. Liebigs Ann. Chem. 1979, 219-226.

105 by rotary evaporation. Benzene (25 mL) was added to the residue and the mixture was stored at 0 °C for 3 h. After the insoluble material was filtered off, the filtrate was vacuum distilled twice (60 °C @ 2 mm Hg) to give phenyl(trimethylsilyl)ketene (90,

0.173 g, 13%) as a yellow oil; IR stretches were identical to those reported in the literature64: FTTR (NaCl) 2085 (m), 1650 (m) cm'1.

Nitration of Phenyl(drimethylsilyl)ketene (90)

Cleaned N03BF4 (0.121 g, 0.911 mmol) was added in one portion to phenyl(trimethylsilyl)ketene (0.173 g, 0.911 mmol) dissolved in CH3CN (3 mL) under argon. The solution immediately became brown and warmed slightly. TLC showed only very polar material. No nitro(phenyl)ketene, phenylnitrile oxide or other expected products were detected.

106 RETRO D1ELS-ALPER REACTIONS

Preparation of Dipotassium 233-Trinitropropionaldehyde6S

A solution of mucobromic acid (32.3 g, 125 mmol) in 95% EtOH (140 mL) was added to a potassium nitrite (54.3 g, 639 mmol) in 95% EtOH (60 mL) and H20

(90 mL). The mixture was kept below 35 °C while being stirred for 2 h. The solution became dark and an orange precipitate formed. The precipitate was then vacuum filtered and washed with 70% EtOH (50 mL), 95% EtOH (100 mL) and CH2C12 (100 mL). Dipotassium trinitropropionaldehyde was obtained as a bright orange powder

(27.9 g, 83%) and used without further purification.66

Preparation of Hexanitroethane (95)

Hexanitroethane was prepared by the procedure of Gallaghan et al as follows.

A 3-neck 1 L round bottom flask equipped with a mechanical stirrer, a 250 mL addition funnel and a thermometer was charged with dipotassium 2,3,3- trinitropropionaldehyde (27.9 g, 104 mmol) suspended in CH2C12 (210 mL) with stirring. The suspension was cooled in a Dry Ice/acetone bath. Cold, red fuming H N 03

(182 mL) was added over a 15 min period. A cold mixture of H2S04 (18-24% fuming,

65 Gallaghan, J.A.; Lomond, B.; Reed, W.L U.S. Patent 3,101,379 Aug 20, 1963

66 Dipotassium 2,3,3-trinitropropionaldehyde is a shock-sensitive explosive and decomposes on prolonged standing. The salt was always used with caution immediately after preparation. While no problems were experienced in the present work, Gallaghan, et al suggest that the salt be only handled while wet with CH2C12.

107 210 mL) and HN03 (red fuming, 45 mL) was added over 1 h. Halfway through the

addition, the mixture became viscous and stirring was difficult. The cold bath was

removed for the remainder of the addition An ice bath was placed around the reaction

flask to raise the temperature of the reaction to 0 °C, The flask was placed in a

refrigerator for 3 d and then the layers were separated. The CH2C12 layer was carefully

washed with H20 (100 mL portions) until the washings were colorless (-2.5 L H20),

dried over MgSO< for 2 h, filtered and cooled to -80 °C. White crystals of

hexanitroethane (95) formed were filtered: 10.50 g (34%); FTIR (KBr) 1613.3 (s),

1285.3 (m), 883.8 (m), 819.8 (m), 779.3 (m) cm'1.

Preparation of 9,I0-Dihydro-Il,ll,12,12-tetnuiitn»-9,10-ethaiioanthraceiie (97a)67

A solution of hexanitroethane (0.30 g, 1.00 mmol) and anthracene (0.45 g, 2.50

mmol) in benzene (10 mL) was refluxed for 30 min under a slow stream of argon.

Shortly before reaching reflux temperature, the violet solution became orange and a

white solid precipitated. The N20,, produced from the reaction was swept away by the argon. The reaction mixture was cooled to room temperature and filtered. The white precipitate was washed with benzene and air-dried: 0.247 g. The product, initially isolated as its benzene solvate, was desolvated at 1 mm Hg in a drying pistol for 3 h using acetone as the heating liquid (56 °C). The resulting cycloadduct, a white solid,

67 Griffin, T.S.; Baum, K. J. Or%. Chem. 1980, 45, 2880-2883.

108 weighed 0.205 g (53%) and had mp 141-143 °C (lit. 142-143 °C). FTIR (KBr) 1598.9

(m), 1578.6 (s), 1467.6 (w), 1356.1 (w), 1301.9 (w) cm 1; MS (High Res) m/e.

Preparation of 9,10-Dihydro-ll,12-dinitn>-9,10-ethenoanthracene (98a)6*

9,10-Dihydro-11,1 l,12,12-tetranitro-9,10-ethanoanthracene (0.050 g, 0.130 mmol) was flash pyrolyzed in a sublimation apparatus at 1 mm Hg while heating with a flame. The yellow solid that sublimed onto the cold finger contained a small amount of the starting material and was repyrolyzed to give complete conversion to the desired product. The yellow solid was scrapped from the cold finger and recrystallized from benzene/hexanes. After drying in a drying pistol for 3 h at 56 °C and 1 mm Hg, dinitroadduct 98a (0.0 lOg) was obtained as a yellow solid: mp 160-162 °C (lit. 162-164

°C); MS (High Res) m/e 294, 248, 218, 202, 189, 178, 151, 101.

Horizontal Pyrolysis Apparatus

A horizontal pyrolysis apparatus was used in many of the following experiments. The apparatus is similar to one designed by Campbell 69 with a few modifications. The apparatus consists of a sample tube (25 x 200 mm), a quartz pyrolysis tube (25 x 550 mm), and a U-shaped trap with a stopcock on each end and one on the side so that liquid samples can be injected into the trap at reduced pressure

64 Baum, K.; Griffin, T.S. J. Org. Chem. 1981, 46, 4811-4813.

69 Campbell, K.A.; House, H.O.; Surber, B.W.; Trahanovsky, W.S. J. Org . Chem. 1987, 52, 2474.

109 (Figure 1). The sample tube was heated with electric heating coils to cause sublimation of the sample into the pyrolysis tube. The pyrolysis tube was filled with quartz chips

(approx. 1.5 cm 2 pieces) and placed inside an electric tube furnace. One end of the trap was attached to the pyrolysis tube, the other end to a vacuum line. A Dewar flask was used for cooling.

Figure 1: Horizontal Pyrolysis Apparatus

Pyrolysis of 9,10-Dihydro-l l,12-dinitn>-9,10-ethenoanthraccne (98a)

9,10-Dihydro-l 1,12-dinitro-9,10-ethenoanthracene (0.15 g, 0.51 mmol) was thermolyzed at 0.25 mm Hg in the horizontal pyrolysis apparatus by heating the sample tube to 230 “C. The pyrolysis tube was heated to 430 °C. An unwrapped glass tube connected the pyrolysis tube to the trap submerged in a Dewar flask containing

Dry Ice/acetone (-78 °C). A yellow solid collected in the unwrapped connector tube

110 and there was very little material in the trap. After all of the starting material had been sublimed through the pyrolysis tube, the stopcocks on each side of the trap were closed and furan (5 mL) was added to the trap via the septa. The vacuum was broken and the contents were scraped from the connecting tube. TLC showed this solid to be the same as tha* in the trap. The total yield was 0.10 g. The product was almost exclusively anthracene with a small amount of starting material.

Pyrolyses of the adduct were also carried out in a GC/MS/IR by injecting a solution of the adduct into the injector at 250, 300 and 400 DC. In all cases, the major product was anthracene with minor amounts of other anthracene compounds (9- cyanoanthracene, 9, 10-anthraquinone ( 101) and other unidentified products). C 0 2 was always seen by FTIR but no dinitroacetylene was detected by FTIR or MS. Lower injector temperatures were insufficient for pyrolysis.

Preparation of 9,10-Dihydnoxy anthracene70

A mixture of anthraquinone (2.00 g, 9.60 mmol), sodium dithionite (2.38 g,

13.7 mmol) and IN NaOH (aq, 200 mL) was stirred 2 h under argon. The resulting dark red solution was acidified with concentrated HC1 (—20 mL). The 9,10- dihydroxyanthracene, a yellow solid, was Filtered under argon and washed several times with H20. The air-sensitive product was dried under argon and quickly used in the next procedure.

70 Landucci, L.L.; Ralph, J. J. Org. Chem. 1982, 47, 3490.

Ill Preparation of 9,10-Bis-(trimettiylsiloxy)anthracene (96b)71

Dry 9,10-di hydroxy anthracene was suspended in triethylamine (46 mL) and

DMF (15 mL). Chlorotrimethylsilane (24.6 g, 228 mmol) was added portion-wise. The

mixture was refluxed 12 h, poured into hexanes (700 mL), and washed with 5%

NajCOj (3 x 200 mL), 5% HC1 (2 x 200 mL) and 5% Na^CO^ (3 x 200 mL). The

organic layer was filtered through a cone of CaS0 4 and concentrated to yield wet yellow crystals (2.4 g, mp 100-120 °C). The 9,10-bis-(trimethylsiloxy)anthracene was

sublimed to give yellow crystals (1.44 g, 42% from anthraquinone): mp 118-122 °C.

The spectra of 96b are identical to those reported .59

Attempted Diels-Aider Reaction of 9,10-Bis-(bimetiiylstloxy)anthracene (96b) with

Tetranitniethylene (94) Generated 'In Situ"

Hexanitroethane (0.300 g, 1.00 mmol) was added to 9,10-bis-(trimethylsiloxy)- anthracene (0.885 g, 2.50 mmol) suspended in benzene (15 mL). There was immediate bubbling and evolution of heat. The mixture was refluxed 15 min under argon, cooled to room temperature and filtered. The product (0.43 g of fine yellow crystals) was slightly impure anthraquinone (83%). The reaction was repeated at -20 °C in CH 2C12 with similar results.

71 Ralph, J.; Landucci, L.L. J Org Chem. 1983, 48, 3887.

112 Reaction of 9,10-Bis-(trimethylsiloxy)anthracene with Tetranitroethylene

Tetranitroethylene was prepared according to the Baum-Tzeng procedure .72 in

the horizontal pyrolysis pyrolysis shown previously (Figure 1). Hexanitroethane (0.33

g, 1.1 mmol) was placed in the sample tube of the pyrolysis equipment. The system

was evacuated to 1 mm Hg and the tube furnace was preheated to 260 °C. The trap

was kept at precisely 10 °C with an ice bath. Heating coils that had been preheated to

90 °C were placed around the sample tube. The hexanitroethane slowly sublimed into

the pyrolysis tube. Tetranitroethylene collected as a green-yellow solid on the walls of

the trap. After all of the hexanitroethane sublimed, the trap was isolated from the

system by closing the stopcocks on each end. A solution of 9,10-bis-

(trimethylsiloxy)anthracene (0.20, 0.57 mmol) in benzene (10 mL) was then introduced

quickly through the septa. The solution became orange and then green-yellow. Upon

removal of the benzene in vacuo, anthraquinone was obtained as the only product.

Attempted Diels-Alder Reaction of 9,10-Diainino-N,IN,IV,N’-tetrainethyl-anthr»cene

(96c) with Tetranitroethylene

Tetranitroethylene was generated in the horizontal pyrolysis apparatus as

described above. 9,10-Diamino-N,N,N',N,-tetramethylanthracene 73 (0.18 g, 0.67 mmol)

in benzene (10 mL) was then introduced through a septa via cannula into the trap

72 Baum, K.; Tzeng, D. J Org. Chem. 1985, 50, 2736-2739.

731 should like to thank Dr. A. Czamik for donation of the N,N,N',N'-tetramethyl- 9,10-diaminoanthracene.

113 containing the freshly prepared tetranitroethylene. All of the tetranitroethylene was washed off the walls of the trap. Additional benzene (10 mL) was used to wash down the contents. The solid formed (0.027 g) was filtered: mp 240-270 °C. Evaporation of the filtrate gave yellow crystals (0.060 g): mp 260-280 °C. The two products were shown to be identical by TLC and then combined and purified by column chromatography (SG, 4:1 hexanes/EtOAc). Anthraquinone (101) was the only product isolated (0.010 g, 7%). There were no nitro products present.

Preparation of 9,10-Dimettioxyanthracene (96d)

The procedure of Meek et ai1A was followed with significant modification.

Anthraquinone (10.40 g, 50.0 mmol) and zinc dust (5.00 g, 76.0 mmol) were ground together with a mortar and pestle. The intimately mixed powder was washed into a flask with EtOH (20 mL) and 20% NaOH (aq, 100 mL), and the mixture was stirred at reflux for 1 h. Upon cooling the deep red solution to room temperature, iodomethane

(28.4 g, 200 mmol) was added. The suspension was stirred for 6 d until the red color was completely gone and then filtered. The pale green solid was washed with basic

10% N aH S 03 (aq), partially dried, taken up in benzene (1 L) and filtered. Removal of the benzene in vacuo gave 9,10-dimethoxyanthracene (96d, 8.72 g) as a bright yellow solid, mp 190-198 °C. Recrystallization from CHCl3/EtOH yielded yellow crystals of

96d (6.03 g, 50.1%): mp 199-201 °C (lit. mp 198-199 aC).

74 Meek, J.S.; Monroe, P A ; Bouboulis, C.J. J. Org. Chem. 1963, 28, 2572-2577.

114 Diels-Alder Reaction of 9,10-Dimethoxyanthracene (96d) and Tetranitroethylene

9.10-Dimethoxyanthracene (0.50 g, 2.1 mmol) was dissolved in CHC1 375 (10

mL). Argon was blown slowly over the solution. Hexanitroethane (0.25 g, 0.84 mmol)

was added in one portion. The mixture turned brown immediately. The N 20 4 formed

and was swept away by the argon. After stirring 2 h, the mixture became orange and

a colorless precipitate settled. The precipitate was filtered and washed well with

CHClj. 9,10-Dihydro-9,10-dimethoxy-11,11,12,12-tetranitro-9,1 0-ethanoanthracene

(97d) was obtained as a colorless powder (0.23 g, 62%). mp 132 °C (exp); FTIR (KBr)

3072.2 (w), 3011.9 (w), 2994.3 (w), 2958.1 (w), 2925.8 (w), 2886.8 (w), 2852.3 (w),

1603 7 (s), 1576.3 (s), 1463.1 (m), 1350.6 (m), 1293.5 (m), 1250.0 (m), 1113.8 (m),

1068.6 (m), 748.6 (m) cm'1; 'H NMR (CDC13) 5 8.0 (m, 4H), 7.6 (m, 4H), 4.4 (s, 6 H) ppm (dissolving the product in CDC1 3 for NMR analysis causes immediate formation of anthraquinone); MS (High Res) m/e 400 (M+-N 03), 354, 262, 238, 223, 208, 180,

152, 76, 46.

Pyrolysis of 9,10-Dihydro-9,10-dimethoxy-l 1,11,12,12-tetranitro-9,l0-ethanoanthracene

<97d)

9.10-Dihydro-9,10-dimethoxy-11,11,12,12-tetranitro-9,10-ethanoanthracene

(0.100 g, 0.224 mmol) was quickly sublimed at 0.65 mm Hg in a sublimation

75 Somewhat lower yields (24%) were obtained with CH 3C12 at 0 °C , Using benzene at room temperature affords the Diels-Alder adduct as a benzene solvate in 66 % yield.

115 apparatus by heating with a flame. The solid that collected on the cold finger was found (by FTIR) to be a mixture of anthraquinone and starting material. There was no trace of 9,10-dihydro-9,10-dimethoxy-l l,12-dinitro-9,10-ethenoanthracene (98d).

Heating adduct 97d in the presence of anthracene or furan does not yield 9,10-dihydro-

1 1 ,1 1 ,1 2,12-tetranitro-9,10-ethanoanthracene (97a).

Preparation of 9,10-Dimethylandiracene (96e)

The method developed of Duerr et. al was used as follows .76 9,10-

Dibromoanthracene (2.54 g, 7.56 mmol) was dissolved in Et20 (25 mL) under argon.

To the stirred solution was added n-BuLi (8.33 mL, 2.38 M in hexanes) in 30 min.

Methyliodide (3.86 g, 27.3 mmol) was added dropwise and the mixture was refluxed

3 d. The resulting suspension was diluted with Et20 (50 mL) and washed with H20

(50 mL). The Et20 layer was washed with brine, dried over MgS04, filtered, and concentrated to dryness. A wet, yellow solid remained which was column chromatographed (SG, hexanes). Fractions containing the main product were combined to afford 9,10-dimethy[anthracene (96e, 1.22 g, 78%) as a bright yellow solid.

Recrystallization of the solid from 95% EtOH yielded 96e (0.49, 31%) as bright yellow platelets: mp 167-170 °C (lit.: 182-184 °C), The spectra of 96e are identical to that reported .75

76 Duerr, B.F.; Chung, Y,-S; Czamik, A.W. J Org. Chem. 1988, 5J, 2120.

116 9,lO-Dihydro-9,10-dimethyl-11,11,12,12-tetranitn>-9,10-ethanoanthracene ( 9 7 e)

Baum prepared this compound by the "in situ" method .77 Tetranitroethylene was

prepared in a horizontal pyrolysis apparatus from hexanitroethane (0.71g, 2.4 mmol)

as described earlier. After the pyrolysis was complete, a solution of 9,10-

dimethylanthracene (0.49 g, 2.4 mmol) in benzene (25 mL) was added to the trap. The

solution became slightly orange and a small amount of colorless solid precipitated. The

product was separated from unreacted 9,10-dimethyl anthracene and polar material by

column chromatography (SG, gradient elution with hexanes/CHjClj), All fractions

containing the desired product were combined and concentrated. Recrystallization of

the residue from benzene/hexanes afforded colorless micro crystals of 97e (0,39 g,

39%): mp 149.5-150.5 °C (dec) (lit. 142-143 °C).

Pyrolysisof9,10-Dihydro-9,10-dimethyl-l1,11,12,12-Tetranitro-9,l 0-ethanoanthracene

(97e)

9,10-Dihydro-9,10-dimethyl-11,11,12,12-tetranitro-9,10-ethanoanthracen^97e)

(0.100 g, 0.242 mmol) was pyrolyzed quickly with a flame at 10 mm Hg 78 in a

sublimation apparatus. The product (0,067 g) was scraped from the cold finger. FTIR

analysis showed that 97e remained. The material was pyrolyzed again by the same

procedure. A small amount of anthraquinone (0.007 g) collected on the cold finger.

77 Griffin, T.S.; Baum, K. J Org. Chem 1980, 45, 2880.

78 Lower pressure (0.7 mm Hg) resulted only in sublimation of the starting material.

117 REACTIONS OF NITROf TRIMETHY LSILYL3 ACETYI ENE

Preparation of Nitro(trimethylsilyl)acetylene (Ig)

Nitro(trimethylsilyl)acetylene (lg ) was prepared by modifying literature

methods as follow s .79 Clean N 0 2BF2 (0.420 g, 3.16 mmol) was added in one portion to bis-(trimethylsilyl)acetylene (0,537 g, 3.16 mmol) in CHjCN (10 mL). The solution warmed slightly and became yellow. After stirring at ambient temperature for 2 h, the solution was quickly filtered through a 3" plug of SG. The SG was then washed with

CHClj (25 mL), The CH3C N /C H C l3 solution contained mostly nitro(trimethylsilyl)acetylene (confirmed by GC/MS/IR) and was used in further experiments. Such solutions were kept at -25 °C between uses and replaced after a few days.

Treatment of Nitno(trimethylsilyl)acetylene with Tetrabutylammonium Fluoride

A solution of nitro(trimethylsilyl)acetylene (prepared as described above) was cooled to -78 °C. Acetone (10 mL) was added followed by dropwise addition of n-

Bu4F (2.1 mL, 1.0 M in THF). The first drops of n-Bu4F caused the reaction mixture to immediately become black. The mixture was poured into water and analyzed by

TLC. Only polar material was seen.

79 Schmitt, R.J.; Bedford, C D Synthesis 1986, 493; Schmitt, R.J.; Bottaro, J.-C.; Malhotfa, R ; Bedford, C D. J. Org, Chem. 1987, 52, 2294.

118 Reaction of nitro(trimethylsilyl)acetylene with n-Bu 4NF, KF (anh) or CsF in the presence of other electrophiles (H 20, acetone, Me 3SiCl, benzoyl chloride, N 0 3BF4) also resulted in polar, intractable products. GC/MS/IR and FTIR showed no trace of 1- nitroacetylenes. Since commercial n-Bu4NF solutions contain 5% water, attempts were also made to find nitroacetylene. FTIR analysis and attempts to trap nitroacetylene with cyclopentadiene did not give any evidence for nitroacetylene.

Treatment of Nitro(trimethylsilyl)acetylene with Silver Nitrate

To a freshly prepared solution of trimethylsilyl(nitro)acetylene (containing -0.45 g of nitro(trimethylsilyl)acetylene) was added AgN0 3 (1.07 g, 6.32 mmol) in aqueous

EtOH (60%, 30 mL). A colorless (sometimes black) precipitate formed. Filtration followed by washing with EtOH and drying left an amorphous solid (0.24 g) exploded on heating or when contacted with bromine. Halogen compounds such as HC1, Br 2,1 2, acid chlorides and Me3SiCl react with this solid to leave a precipitate of silver halide.

No identifiable organic products could be isolated. The precipitate is insoluble in organic solvents and c NH4OH (darkens).

119 OXIDATION OF CYANOGEN-N JN'-DIOXIDE (1041

Preparation of Dichloroglyoxime (106)*°

Glyoxime (105, 2.20 g, 25 mmol) was suspended in 10% HC1 (aq, 75 mL).

Chlorine was bubbled into the mixture until the solution became permanently yellow.

The reaction mixture was placed in a refrigerator overnight. The white precipitate was

vacuum filtered and washed with 10% HC1 (aq) and H 20. The solid was dried at 1 mm

Hg for 2 h to afford dichloroglyoxime (1.73 g, 43%): mp 204-205 °C (dec) (lit. mp

204 °C (dec)).6®

Preparation of Cyanogen-NJN -dioxide (104)®1

Cyanogen-N,N'-dioxide must be used immediately after preparation because it

polymerizes extensively to explosive products. The dioxide must also be kept cold and

in solution to be handled safely. A solution of cyanogen-N,N'-dioxide was prepared as

follows: dichloroglyoxime (0.50 g, 3.2 mmol) in CHC1 3 (15 mL) was cooled to 0 X.

An solution of IN NaXOj (aq) cooled to 0°C was added with stirring. After 1 min,

the aqueous layer was removed via pipet The organic solution was cooled to -42 X , dried over Na^SO* for 1 h at -42 QC and decanted from the Na^O,,. The solutions of cyanogen-N,N'-dioxide (104) were used immediately after preparation.

80 Ponzio, G.; Baldracco, F. Gaz. Chim. Itai, 1930, 60, 434.

81 Grundmann, C. Angew. Chem. Int. Ed. Engl 1963, 2, 260-261.

120 Oxidation of Cyanogen-IN,N’-dioxide with Metal Oxides

Solutions of cyanogen-N,N'-dioxide were prepared as described previously. An

oxidant such as KMn04, Mn02, Ag 20, Cr03, or PDC was added at -78 °C. The

reaction was warmed to room temperature and analyzed by FTIR and/or GC/MS/IR.

Polymeric mixtures formed from these reactions and are probably products from

polymerization of cyanogen-N,N'dioxide. In no experiments were any nitro compounds

found.

Oxidation of Cyanogen-NJN-dioxide with Ozone

A solution of cyanogen-N,N'-dioxide (0.637 mmol) in CH 2C12 (15 mL) was

cooled to -78 °C under argon. Ozone (1.27 mmol in oxygen) was bubbled into the

reaction mixture (1 min 9 s / 1.1 mmol/min). The pale yellow solution was brought to

room temperature, washed with water, dried over MgS0 4 and concentrated in vacuo to leave a brown oil (0.01 g). TLC of the oil shows it to be unchanged by the work-up.

The oil would not pass through GC. FTIR analysis showed no nitro groups. Attempted oxidation with hydrogen peroxide (30%), bis-(trimethylsilyl)peroxide and 0 2 were likewise unsuccessful.

121 PART 2

STATEMENT OF PROBLEM

Many aryl methylenes and heterylmethylenes undergo deep-seated

rearrangements and fragmentation reactions at elevated temperatures (250-600 °C). The

present research involves definition of various possible intramolecular reactions of 2-

pyrrolylmethylenes (1) in liquid and in gas phase. The possible rearrangement reactions

(Equation 1-3) of 1 are: (1) ring-opening (Equation 1) to ynenimines 2, (2)

rearrangements (Equation 2) to l,2-dihydro-2-pyridinyiidenes (3) and/or pyridines (4)

and (3) rearrangement to cycloazaallenes 5 with subsequent fragmentation (Equation

3) to propargylaldehyde imines ( 6 ) and acetylene (7). Other possible rearrangement processes of I will also be evaluated.

122 123 PART 2

CHAPTER 4

HISTORICAL INFORMATION

The behaviors of various (2-hetaryl)methylenes have been studied intensely in this laboratory .®2 2-Fury 1 methylenes (7), as generated by decomposition of diazo(2- furyl)methanes (8) prepared in situ from sodium salts of 2-furancarboxatdehyde p- tosylhydrazones (9), ring-open at 250-300 °C to (E/Z)-ynenones (10, Equation 4).

NaTos

®3 Hoffman, R.V.; Shechter, H J. Am. Chem. Soc. 1971, 98, 5940. (b) ibid, 1978, 100, 7927. (c) Hayashi, S.-I.; Nair, M.; Houser, D.J.; Shechter, H. Tetmhedrvn Lett. 1979, 32, 2961.

124 Sodium 2-thiophenecarboxaldehyde p-tosylhydrazones (11) also decompose

(Equation 5) at 250-300 °C to diazo(2-thienyl)methylenes (12) and then 2- thienylmethylenes (13). Ring-openings of carbenes 13 yield ynenthials 14 and their polymers 15 (Equation 6 ). (E/Z)-l,2-Di(2-thienyl)ethylenes (16) are also obtained,

N aTos

presumably by capture of carbenes 13 by their diazo precursors 12 and loss of nitrogen and/or by dimerization of 13 (Equation 7). 2-Thienylmethylenes (13) are apparently more resistant to ring-opening than their 2-furylmethylene counterparts (7).

125 -N- ♦-

R R

1 -(4-Methyl-5-oxazolyl)methylenes (17), as generated from sulphonylhydrazone salts, ring-open (Equation 8) to N-acyl-3-alkyn-2-one imines (18). It is not clear whether 17 isomerize directly to 18 and/or whether 17 rearrange first to 19 which then collapse to 18. Imines 18 are thermally unstable. Hydrogen migration occurs in 20 to yield 3-acylamide-3-buten-l-ynes (21, Equation 9).®2c

126 JX*c h3 H 17 CH 18

(8)

(9) OH H H

20 21

Sodium (3-methyl-5-isoxazolyl)carboxaldehyde p-tosylhydrazones thermolyze

at 275 °C to (3-methyl-5-isoxazolyl)methylenes (22, Equation 10). Rather than

undergoing direct ring-opening, carbenes 22 fragment to nitriles 23 and ynones 24

(Equation 10). Carbenes 7, 17, and 22 can be trapped by cyclooctatetraene in low yield before ring-opening or fragmentation occurs / 2

127 H

O O R' 22

(10) H O -► R—C=N * H—C == C c —lL 'R' 23 24

4-DiazomethyM,5-diphenyl-l,2,3-triazole (25) decomposes thermally with loss of two molecules of nitrogen to yield 3-phenyl-3-phenyliminopropyne (27, 17%;

Equation 11 ).83 Of interest is that 26, the presumed carbene intermediate, loses nitrogen to form 27 (Equation 11),

Ph Ph I P h \ ^N N v Ph. —Ph -N, H—C = C —C ( 11) i f Ph n 2= cX/ i CX I I H H 27

25 26

83 Smith, P.A.S.; Wirth, JG J. Or%. Chem. 1968, 33, 1145.

128 The intermolecular behaviors of [2-(]-methyl)pyrrolyl]diazomethane (29) and

its subsequent carbene, 2-[(l-methyl)pyrrolyl]methylene (30), as generated (Equation

- NaTos

CH3 H ^ , a

12) by decomposition of the sodium salt of l-methyl- 2-pyrrolecarboxaldehyde p-

tosylhydrazone (28) have been investigated .84 Thermolysis of 28 at 110 °C in the

presence of cis-stilbene gives cyclopropanes 31 and 32 stereospecifically in 2.1% total yield along with l-methyl-2-pyrrolecarboxaldehyde azine (33, 7.6%) and other non-

carbenic products .84 Decomposition of 28 at 110 °C in the presence of trans-stilbene

occurs stereospecifically to yield cyclopropane 34 (2.0% yield) along with 33 (12.5%)

and complex products .84 Although its overall behavior is miserable 30, generated as above, appears to react as a singlet when cyclopropanating cis- and trans-stilbenes.

Molecular orbital calculations for 30 reveal that the carbene is a ground state triplet and nucleophilic .84

84 Saito, K.; Ushida, T.; Fushihara, H.; Yamashita, Y.; Tanaka, S.; Takahashi, K. Heterocycles 1990, 37, 115.

129 130 PART 2

CHAPTER 5

RESULTS AND DISCUSSION

The carbenes 7, 13, 17, and 22 discussed in the Historical Information Section were generated from sodium salts of their corresponding p-tosylhydrazones. In order to study their behavior in the present research, 2-pyrrolylmethylenes (30) were also prepared from sodium salts (28, R = CH3) of p-tosylhydrazones. p-Tosylhydrazone salts

28 (R = CH3) can easily be prepared by condensation of 2-pyrrolecarboxaldehydes (35) with p-tosylhydrazine followed by deprotonations of 36 by sodium hydride (Equation

13).

h h 2nnht

35 36 28

Vacuum pyrolysis of the sodium salt of l-methyl-2-pyrrolecarboxaldehyde p- tosylhydrazone (28, R CH3) at 250 °C/0.3 mm Hg, conditions identical with that for ring openings of 7 and 13, gives E (37)- and Z (38)-l,2-di(l-methyl-2-

131 pyrrolyl)ethylenes (Equation 14) in a 3:2 ratio in 33% yield along with bis-(l- methylpyrrolyl)ketazine (33, 14%, Equation 15). Higher temperatures (300 °C) and different techniques for manipulating 28 (R = CH3) as a dry solid did not significantly alter the results of decomposition of 29.

c h 3 h

In an effort to minimize bimolecular reactions of 29, sodium salt 28 (R = CH3) was deposited onto a large excess of silica gel. Thermolysis of the solid mixture at 250

°C yields ethylenes 37 and 38 but little azine 33. Decomposition of sodium salt 28 (R

= CH3) in diglyme at 250 °C in a sealed tube gives a complex mixture resulting from reactions of carbene 30 with the solvent.

Formation of ethylenes 37 and 38 in the above experiments apparently arises from reaction of carbene 30 with 29 with loss of nitrogen and/or by dimerization of

132 carbene 30 (Equation 16). Clearly, thermolysis of sodium salt 28 (R = CH3) on silica

30 37 + 38 gel minimizes bimolecular reactions of 29 to give azine 33. Efforts to decompose 29 as prepared by oxidation of l-methylpyrrole-2-carboxaldehyde hydrazone (39) with silver oxide were unsuccessful because of the rapid conversions of 29 and 39 to azine

33 (Equation 17). In further attempts to generate 30 cleanly, 7-[[(l-methylpyrrol-2-

Ag 2< \ 33 (17) - h20 c h 3 o

35 (R = CH3) 39 yl)methylene]amino]-7-azabicyclo[4.1.0]heptane (40) was prepared as summarized in

Equation 18. Hydrazone 40 is surprisingly stable thermally and does not decompose upon heating at 200 °C for 1 hour Dropping a solution of 40 into a packed vertical

133 pyrolysis tube at 400 °C is not a satisfactory method for effecting the unimolecular intramolecular reactions of 30.

0 ^ > - N H 2 . Q 0 T ^ N - < O ( 18)

O o

n , h 4-h ?o

The above experiments with salts 28 (R - CH3) and other precursors for 30 are significant in that the carbene does not undergo ring-opening as readily as do 7, 13, and 17. Ynenimines 41 and 42 are not formed (Equation 19). Further, 30 does not rearrange (Equation 20) to N-methylcyclopentadienoneimine (43) or 2-methylpyridine

(44) or collapse (Equation 21) to N-methylpropargylaJdehydeimine (45) and acetylene

(7)

134 ,CH,

(19)

CX/H N I c h 3 (20)

(21)

The resistance of 30 to ring-opening, isomerization, and fragmentation appears to be related to the electron-donor capacity of nitrogen in 30 such that there is extensive electronic contribution and nitrogen-carbon double bond character as in 46.

Such effects are predicted to be greater in 46 than in 47 or 48 and therefore 46 is less electrophiiic than is 47 or 48

135 PLEASE NOTE

Page(s) missing in number only; text follows. Famed ss received.

UMI CHr11 cWh

4847 46

Decomposition of (2-pyrrolyl)diazomethane (49) as generated by thermolysis of the sodium salt of 2-pyrrolecarboxaldehyde p-tosylhydrazone (28, R = H) was then investigated. Upon conditions identical to those for ring-openings of 2-furylmethylenes

(250 °C, 0.3 mm Hg), as previously described, pyrolysis of 28 (R = H) gives only high molecular weight products. There is no evidence for conversion of ( 2- pyrrolyl)methylene (50) to (1) (E)- and/or (Z)-2-penten-4-ynalimines (51) by ring- openings (Equation 22) or (2) (E)- and/or (Z)-l,2-bis-(2-pyrrolyl)ethylenes (52,

Equation 23) by carbene dimerization or reaction of 50 with the carbene precursor 49

(Equation 24). As does l-methyl-(2-pyrrolyl)methylene (30), 50 resists ring-opening under the conditions studied

137 H (22)

51 -N, H N I H

49 50 (23)

50 52

Of further interest is that pyridine (53), a likely product of rearrangement of 50

(Equation 25), is not detected. Finally, rearrangements of 50 to cyclopentadienoneimine

(54, Equation 26) and to 2-methylene-2H-pyrrole (55, Equation 27) are possible. The

138 55

C5H5N isomers, 54 and 55, are expected to be reactive monomers that polymerize rapidly and have been subject of interest to many theoreticians .85 Preparation of 54 and/or 55 may be possible by proper decomposition of 28 (R = H) and handling of the reaction products.

85 a) Gutman, I.; Milun, M.; Trinajstic, N. J. Am. Chem. Soc. 1977, 99, 1692; (b) Vysotskii, Y.B; Zemskii, B.P. Khim Geterotsikl. Soedirt. 1983, 341 (Russ ); (c) Zhou, Z,; Parr, R.G, J. Am. Chem. Soc. 1989, ///, 7371.; (d) Meyers, F.; Adant, C.; Toussaint, J.M,; Bredas, J.L. Synth. Met. 1991, 43, 3559; (e) Meyers, F.; Adant, C.; Bredas, J.L. J. Am. Chem. Soc. 1991, 113, 3715; (f) Boehm, M.C.; Schuett, J.; Schmitt, U. J Phys. Chem . 1993, 97, 11427.

139 PART 2

CHAPTER 6

EXPERIMENTAL SECTION

Preparation of l-Methyl-2-pyrrolecarboxaldehyde p-Tosylhydrazone (36, R = CH3)

l-Methyl-2-pyrrolecarboxaldehyde (35, R = CH3) (1,00 g, 9.16 mmol) and p- tosylhydrazine (1.79 g, 9.62 mmol) were refluxed in absolute EtOH (10 mL) for 0.5 h. Crystallization occured after cooling and scratching. l-Methyl-2- pyrrolecarboxaldehyde p-tosylhydrazone (36, (1.80 g, 71%) was filtered and washed with EtOH. Recrystallization from EtOH yields pale purple crystals (1.16 g): mp 121-

123 °C; FTIR (KBr) 3165 (m), 1619 (m), 1439 (m), 1352 (m), 1324 (m), 1169 (s),

1042 (m), 939 (m), 746 (m), 709 (m), 692 (m), 572 (m), 546 (m), 518 (m) cm '; 'H

NMR (DMSO 6d) 8 10.9 (br s, 1H), 7.8 (s, 1H), 7.7 (m, 2H), 7.4 (m, 2H), 6.9 (m,

1H), 6.3 (m, 1H), 6.0 (m, 1H), 3.6 (s, 3H), 2.3 (s, 3H) ppm; nC NMR (DMSO 6d) 5

143.5, 141.1, 136.2, 129.7, 128.0, 127.5, 126,5, 115.0, 108.2, 36.4, 21.1 ppm; MS

(High Res) m/e 277.087 (calc. 277.088) 122, 107, 95; calcd for Cl 3H 15N30 2S: C, 56.30;

H, 5.46; found: C, 56.42; H, 5.51.

140 Preparation of the Sodium Salt of 1-Methyl-2-pyrrolecait>oxaldehyde p-Tosylhydrazone

(28, R = CHj)

l-Methyl-2-pyrrolecarboxaldhyde p-tosylhydrazone (36, R = CH 3)(1.00 g, 3.61 mmol) and sodium hydride (0.149 g, 3.72 mmol, 60% in mineral oil) were stirred in

CH2C12 (10 mL) for 0.5 h. The reaction mixture was diluted with Et20 (30 mL) and filtered under argon. Salt 28 (R = CH}) was dried at 1 mm Hg for t h.

Pyrolysis of the Sodium Salt of l-Methyl-2-pyirolecaihoxaldehyde p-Tosylhydrazone

(28, R = CHJ

Salt 28 (R = CHj) (prepared as described previously) was placed in a round bottom flask equipped with a bent glass tube connected to a trap at -78 °C. The apparatus was evacuated to 0.25 mm Hg. The round bottom flask was submersed into a preheated (250 °C) sand bath to effect pyrolysis of 28 (R = CH3). Sodium p-tosylate

(0.51 g, 80%) was recovered from the pot and a brown oil (0.33 g, 97% of theoretical weight for the carbene) was recovered from the receiver and the walls of the apparatus.

Analysis by GC/MS/IR allowed identification of three major products: E- (37, 29%)

Z-(38,22%)l,2-di(l-methyl-2-pyrrolyl)ethylenesandbis-(l-methyl-2-pyrrolyl)ketazine

(33, 25%). Column chromatography (SG) resulted in poor separation and decomposition of the products. Small amounts of 33 were obtained by preparative GLC for 'H NMR analysis. Spectra for ethylenes 37 and 38 were identical to those found

141 in the literature.®6 The structure of azine 33 was also confirmed by comparison to that reported in the literature .87 Pyrolysis of 28 (R = CH3) at 300 °C resulted in formation of the same products but the ratio of ethylenes 37 and 38 to azine 33 was 92:7S:25.

Pyrolysis of Sodium Salt 28 (R = CH3) on Silica Gel

Sodium salt 28 (R = CH3) (1.08 g, 3.6 mmol) was mixed well with silica gel

(5 g) and the mixture was pyrolyzed as described in the previous experiment. The resulting residue from the pyrolysis was rinsed from the apparatus with CH 2C12.

Removal of the CH 2C12 in vacuo yielded a brown residue (0.10 g). Analysis by

GC/MS/IR showed E-(37) and Z-(38) l,2-di(l-methyl-2-pyrrolyl)ethylenes but only a small amount of azine 33.

Pyrolysis of the Lithium Salt of l-Methyl-2-pyrrolecarboxaldehyde p-Tosylhydnizone in Diglyme

l-Methyl-2-pyrrolecarboxaldehyde p-tosylhydrazone (36, R = CH3) (0,50 g, 1.8 mmol) was suspended in diglyme (5 mL) in a screw-top pressure tube. n-Butyllithium

(1.4 mL, 1.31 M in hexanes) was added causing all of the hydrazone to go into solution. The tube was sealed and submerged into a molten salt (KN0 3/NaN02) bath at 250 °C. After heating 1 min, the mixture was brought to room temperature and

86 Hinz, W; Jones, A., Anderson, T. Synthesis 1986, 620.

87 Saito, K.; Ishihara, H. Heterocycles 1987, 26, 1891.

142 washed with E^O (25 mL) and H20 (25 mL). The E^O layer was washed with water

(4 x 75 mL) and brine and dried over MgS04. TLC showed several products.

GC/MS/IR analysis indicated that all products resulted from reaction of the carbene

with diglyme. There was no trace of 37, 38 or 33.

Preparation of 4,7-Phthalimido-7-azabicyclo(4.1.0]heptane88

N-Aminophthalimide (4.000 g, 25 mmol) was suspended in cyclohexene (25

mL) and CH 2CI2 (25 mL). Lead tetraacetate (11.100 g, 25 mmol) was added portionwise at room temperature over 5 min with stirring. After 30 min, the yellow suspension was filtered. The filtrate was filtered through SG and concentrated under reduced pressure below 40 °C. A yellow-green oil was obtained that was crystallized in EtOH to afford 4,7-phthalimido-7-azabicycIo[4.1.0]heptane (3.32 g, 55%): mp 132-

134 °C (lit.88 132-133 °C).

Preparation o f 7-Amino-7-azabicyclo[4.1.0] heptane88

4,7-Phthalimido-7-azabicyclo[4.1 OJheptane (1.254 g, 5.18 mmol) was stirred with hydrazine hydrate (13 mL) for 0.5 h. The solution was extracted with Et20 (3 x

10 mL). The extracts were combined, dried over K 2C 0 3 and concentrated via rotory evaporator. 7-Amino-7-azabicyclo[4.1 .OJheptane (0.51 g, 88%) was obtained as colorless crystals after drying at 1 mm Hg for 1 h.

88 Felix, D.; Muller, R.K.; Horn, U.; Joos, R.; Schreiber, J; Eschenmoser, A. Helv. Chim A cta 1972, 55, 1276.

143 Preparation of 7-[[(l-Methylpynrol-2-yl)methylene]amino]-7-azabicyclo[4.1.0]heptane

(40)

A solution of l-methyl-2-pyrrolecarboxaIdehyde (35, R = CH3) (0.521 g, 4.78 mmol) and 7-amino-7-azabicyclo[4.1, OJheptane in benzene (50 mL) was refluxed for

5 d. The product was isolated by column chromatography (SG, 4:1 EtOAc/Hexanes).

Hydrazone 40 was isolated as an analytically pure orange oil (0.66 g, 71%): FTIR

(NaCl) 2933 (m), 2856 (m), 1614 (m), 1428 (s), 1295 (m), 1089 (m), 1055 (m), 723

(m) cm'1; 'H NMR (CDC13) 5 8.32 (s, 1H), 6.63 (m, 1H), 6.39 (m, 1H), 6.09 (m, 1H),

3.79 (s, 3H), 2,25 (m, 2H), 1.90 (m, 4H), 1.30 (m, 4H) ppm; MS (High Res) m/e

203.143 (cald. 203.142), 121, 107, 92, 66 , 53, 39; calcd for C 12Hl7N3: C, 70.901; H,

8.429; found: C, 70.81; H, 8.40.

Pyrolysis of 7-||(l-m e ihylpyrrol-2-yl)me thy lene]amino|-7-azabicyclo[4.1.0] heptane (40)

A solution of azabicycloheptane 40 in benzene (5 mL) was dropped slowly through a vertical pyrolysis apparatus filled with glass helices. The trap at the bottom of the pyrolysis tube was cooled to -78 °C. Brown insoluble material collected in the trap. The material would not pass through GC and showed no indication of any ring- opening or ring-expansion products by FTIR or 'H NMR.

144 Preparation of 2-PyrroIecarboxaldehyde p-Tosylhydrazone (36, R = H)

2-Pyrrol ecarboxaldehyde (35, R = H) (1.00 g, 11.0 mmol) in MeOH (3 mL) was added to p-tosylhydrazine (1.96 g, 11.0 mmol) in MeOH (5 mL). The solution was refluxed for 0.5 h and then cooled to room temperature. Pale purple crystals of hydrazone 36 (R = H) (2.11 g, 73%) were filtered and washed with MeOH.

Recrystallization from absolute EtOH (75 mL) afforded 2-pyrrolecarboxaldehyde p- tosylhydrazone (36, R = H; 1.47 g, 50.9%) as brown prisms: FTIR (KBr) 3382 (m),

3172 (m), 1615 (m), 1457 (m), 1432 (m), 1332 (m), 1295 (m), 1165 (s), 1092 (m), 922

(m), 816 (m), 746 (s) cm'1; lH NMR (DMSO d6) 5 11.25 (m, 1H), 7.75 (m, 3H), 7.36

(m, 2H), 6.8 (m, 1H), 6.3 (m, 1H), 6.0 (m, 1H), 2.34 (s, 3H) ppm; ,3C NMR (DMSO d6) 6 143.3, 140.7, 136.5, 129.6, 127.4, 126.6, 122.4, 113.1, 109.2, 21.1 ppm; MS

(High Res) m/e 263.0730 (M*) (calc. 263,0728), 108, 91, 81; calcd for C 12H n N 30 2S:

C, 54.74; H, 4.98; found: C, 54.68; H, 4.95.

Preparation of the Sodium Salt of 2-Pyrrol ecarboxaldehyde p-Tosylhydrazone (28, R

= H)

2-Pyrrolecarboxaldehyde p-tosylhydrazone (36, R = H) (1.00 g, 3,8 mmol) was suspended in THF (20 mL) and CH 2C12 (20 mL). Sodium hydride (0,1561 g, 3.9 mmol,

60% in mineral oil) was added and stirred until the purple color from the tosylhydrazone was gone (30 min). The insoluble salt (28, R - H) was filtered off under argon and dried at 1 mm Hg overnight.

145 Pyrolysis of the Sodium Salt of 2-Pyrrolecarboxaldehyde p-Tosylhydrazone (28, R -

The sodium salt of the p-tosylhydrazone prepared above (28, R = H) was

placed in a pear-shaped flask equipped with a bent glass tube leading to a trap at -78

°C. The apparatus was evacuated to 0.25 mm Hg and the pear-shaped flask was

submerged into a sand bath preheated to 250 °C. Salt 28 (R = H) quickly decomposed causing a momentary rise in pressure (evolution of N2). A thick, yellow, foul smelling oil (0.26 g) collected in the receiver and on the flask walls. The oil would not pass through GC. There was no evidence for carbene ring opening, carbene dimerization or azine formation.

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33 Baum, K.; Tzeng, D.J. J Org. Chem. 198S, 50, 2736.

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38 Dailey, W.F. Tetrahedron 1990, 46, 7341.

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Spectra identical to those in the literature: (a) Nakovich, J.; Shook, S.D.; Miller, F.A. Spectrochem. Acta 1979, 35A, 495. (b) Walton, D.R.M.; Waugh, F.J. J. Organometal. Chem. 1972, 37, 45.

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Bhattacharya, S.N.; Josiah, B.M.; Walton, D.R.M. Organometal Chem. Syn. 1970/1971, 1, 145

Using Et,0 as solvent results in phenyl(ethynyl)sulfone in nearly quantitative yield.

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The authors of the original report incorrectly assigned the structure of this product as 1-phenyl-2,2-dinitro-3-cyano-l-propanone.

Stork, G.; Tomasz, M. J. Chem. Soc. 1964, 86, 475.

Jacobs, T.L.; Cramer, R.; Hanson, J.E. J. Chem. Soc. 1942, 64, 223. 55 Schchukovskaya, L.L; Pal’chik, R.I.Jzv. Akad. Nauk SSSR, Ser. Khim. 1964, 12, 2228.

56 Dehn, W.H. J. Am. Chem. Soc. 1911, 33, 1598.

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58 Rebrovic, L.; Koser, G.F. J. Org. Chem. 1984, 49, 4700.

59 Eistert, B.; Geiss, F. Chem. Ber. 1961, 94, 929.

60 Shriner, Fuson, Curtin The Systematic Identification of Organic Compounds - A Laboratory Manual, 5th Ed.; 63.

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66 Dipotassium trinitropropionaldehyde is a potentially shock-sensitive explosive and decomposes on prolonged standing so it was always used with caution immediately after preparation. While no problems were experienced in our work, the authors of the patent suggest only handling the salt while still wet with CH2C12,

67 Griffin, T.S.; Baum, K. J. Org. Chem. 1980, 45, 2880.

68 Baum, K.; Griffin, T.S. J. Org. Chem. 1981, 46, 4811.

69 Campbell, K A ; House, H.O; Surber, B.W.; Trahanovsky, W.S. J. Org. Chem. 1987, 52, 2474.

70 Landucci, L.L.; Ralph, J. J. Org. Chem. 1982, 47, 3490.

151 71 Ralph, J.; Landucci, L.L. J. Org. Chem. 1983, 48, 3887.

72 Baum, K.; Tzeng, D. J. Org. Chem. 1985, 50, 2736.

73 I should like to thank Dr. A. Czamik for donation of the 9,10-Diamino- N,N,N',N'-tetramethylanthracene.

74 Meek, J.S.; Monroe, P.A.; Bouboulis, C.J, J. Org. Chem. 1963, 28, 2572.

75 Somewhat lower yields (24%) were obtained with CH 2C12 at 0 °C . Using benzene at room temperature affords the adduct as a benzene solvate in 66 % yield.

76 Duerr, B.F.; Chung, Y,-S; Czamik, A.W. J. Org. Chem. 1988, 53, 2120.

77 Griffin, T.S.; Baum, K. J. Org. Chem. 1980, 45, 2880.

78 Lower pressure (0.7 mm Hg) resulted only in sublimation of the starting material.

79 Schmitt, R.J.; Bedford, C D Synthesis 1986, 493; Schmitt, R.J.; Bottaro, J.-C., Malhotra, R.; Bedford, C.D. J. Org. Chem. 1987, 52, 2294.

80 Ponzio, G.; Baldracco, F. Gaz. Chim Itai. 1930, 60, 434.

81 Grundmann, C. Angew. Chem. Int. Ed. Engl. 1963, 2, 260.

82 (a) Hoffman, R.V.; Shechter, H. J. Am. Chem. Soc. 1971, 98, 5940. (b) Hoffman, R.V.; Shechter, H. ibid 1978, 100, 7927. (c) Hayashi, S.-I.; Nair, M.; Houser, D.J.; Shechter, H. Tetrahedron Lett. 1979, 32, 2961.

83 Smith, PAS; Wirth, JG J. Org. Chem. 1968, 33, 1145.

84 Saito, K.; Ushida, T.; Fushihara, H,; Yamashita, Y.; Tanaka, S.; Takahashi, K..Heterocycles 1990, 31, 115.

85 a) Gutman, I.; Milun, M.; Trinajstic, N. J. Am. Chem. Soc. 1977, 99, 1692; (b) Vysotskii, Y.B; Zemskii, B.P. Khim. Geterotsikl. Soedin. 1983, 341 (Russ); (c) Zhou, Z., Parr, R.G. J. Am. Chem. Soc. 1989, 111, 7371.; (d) Meyers, F.; Adant, C,; Toussaint, J.M.; Bredas, J.L. Synth. Met. 1991, 43, 3559, (e) Meyers, F.; Adant, C.; Bredas, J.L. J. Am .

152 Chem. Soc. 1991, 113, 3715; (f) Boehm, M.C.; Schuett, J.; Schmitt, U. J Phys. Chem 1993, 97, 11427.

86 Hinz, W; Jones, A.; Anderson, T. Synthesis 1986, 620.

87 Saito, K.; Ishihara, H. Heterocycles 1987, 26, 1891.

88 Felix, D.; Muller, R.K.; Horn, U.; Joos, R.; Schreiber, J; Eschenmoser, A. Helv. Chim. Acta 1972, 55, 1276.

153 APPENDIX A

PART 1: MISCELLANEOUS REACTIONS

Attempted Coupling of lithium Ethynyl(phenyl)sulphone (110):

Reaction of ethynyl(phenyl)sulphone (109) in Et20 with n-BuLi in hexanes at -

78 °C yields a white solid (presumably lithium ethynyl(phenyl)suphone (110)) which, upon treatment with N 20 4, affords the parent acetylene, 109, in 95% yield. Because of the insolubility of the lithium acetylide (110), oxidative coupling does not occur to give butadiyne 111. Instead, ethynyl radical 112 abstracts hydrogen from the solvent

(Equation 86 ). In an attempt to facilitate conversion to 111, THF was used to promote solution of 110. Treatment of ethynyl(phenyl)sulphone (109) with n-BuLi in THF at -

78 °C results in immediate darkening of the solution and precipitation of a black, amorphous solid. Deprotonation of 109 with lithum bis-(trimethylsilyl)amide also causes darkening and precipitation of a carbonaceous material. GC/MS/IR analysis of the reaction solution shows diphenyl sulphoxide (113, 83.5%), diphenyl disulphide

(114, 6.5%), and S-phenyl benzenesulfonothiolate (115, 7.4%) (Equation 87). The present researchers speculate that lithium ethynyI(phenyl)sulphone110 ( ) undergoes 1,2- elimination of lithium phenylsulphinate (116) to give diatomic carbon, "C2". The mechanism for formation of the products is not yet known but the lack of oxygen in

154 PhS02— C ~ C —H PhS02~ C = C —Li - - ° 4- 109 (86) *7o °L 109 n o 95%

-78 oc P1SOC ^ -c = < P -u *c=c- PhSOjLi 110 116

O *■ Ph—S—Ph * Ph—S—S—Ph + Ph— H—S—Ph + Carbonaceous (87) J! materialmaterial 113,84% 114, 7% 115, 7% the products might be a result of reduction by "C2". An additional possible mechanism is homolytic cleavage of the carbon-sulphur bond in 110 to give radical anion 117 and phenylsulphinyl radical 118 (Equation 88).

118 110 117

Reaction of Diiodoacetylene (119) and Silver Nitrite:

Treatment of a concentrated solution of diiodoacetylene (119) in CH3CN with silver nitrite (2 equiv.) at room temperature results in immediate and vigorous evolution of gases and formation of a white precipitate. Upon stirring for several hours, the white precipitate converts to silver iodide (yellow). Approximately 50% of the

155 theoretical amount of silver iodide is consistantly recovered from these reactions by filtration. Analysis of the gaseous mixture by GC/MS/IR reveals three gases: nitrogen, nitric oxide and carbon dioxide in a 5:5:2 ratio. Approximately 50% of the theoretical amount of gas expected from total decomposition of dinitroacetylene (3) and/or acetylene nitrites (120, 121) to gaseous products was observed. No organic products were isolated from these reactions. Concentration of the filtrate always resulted in precipitation of more silver iodide. The white precipitate intermediate from these reactions can be isolated but its structure has not been identified. Chemical tests were performed on the precipitate as discussed in the Experimental section.

A possible mechanism for reaction of diiodoacetylene (119) and silver nitrite is initial coordination of silver ion to the carbon-carbon triple bond of diiodoacetylene

(119) followed by insertion of the silver ion into the carbon-iodine bond. Nitrite ion then displaces silver iodide by oxygen or nitrogen attack to yield dinitroacetylene (3), nitrito(nitro)acetylene (120) and dinitritoacetylene (121). Acetylenes 3, 120 and 121 then decompose to nitrogen, nitric oxide and carbon dioxide (Equation 89).

156 ® n C e N ° 2 I—C=C—I + AgN0 2 ------► Ag I— C = C — I 119

0 2N —C = C —N 0 2 * 0 2N—C^C—ONO + ONO—C=C—ONO

3 120 121

► N2 +■ C 02 + NO (89)

157 APPENDIX B

*H NMR, 13C NMR AND FTIR SPECTRA

OF NEW COMPOUNDS

PART 1

158 Figure 2: FI'IK of l-Nitn>-l,4,6-triphenyl-l,2,3-hexatriene-5-yiie (42) m Figure 3: lH NMR (200 MHz) of l-Nitro-l,4,6'{iiphen}'l-l,2,3-hcxaUicnc-5-yne (42) 3: lH NMR Figure MHz) (200 of l-Nitro-l,4,6'{iiphen}'l-l,2,3-hcxaUicnc-5-yne

160 C NMtt (50 M llz) of t-Ninu- 1.4,6-iri|ilitMiyl-I,2,3-hcxutncn-5-yiie (42) Figure 4:

1000 cm-* 500 1500 2000 2500 3000 ethanoanthracene (97d) 3500 Figure 5: FTIR of 9,10-Dihydro-9,10-dimethox>'-l1,11*12,12-tetranitn>-9,10- 4000 ELMER B5.65 -13,43 PERKIN

162 a-*tfv a ^Ul rwotn OOOOO’D'IMn rnj’ c O 0 0. £3 0 m m noO O j «oorfin

B NI r*

>> W C €OJ E I o I £ ■a

o\ «*- o . o w a e

□os ^ 4J i s a ^ **

s£ ax cZ

163 APPENDIX C

NMR AND I3C NMR SPECTRA

OF NEW COMPOUNDS

PART 2

164 Figure 7: *H NMR (200 MHz) of 2-Pvm)lcc:iit)ox:»lilehyde TosylhydiTizone (36, R c:m;W8 M fA* * sia * %H r4 a A

I !

Figure 8; 1JC NMR (50 MHz) of 2-Pynolcc;iri)oxal(lchydc Tosyllmlnizonc 06, R - H) 120J2 Figure 9: ‘H NMR (200 MHz) of 7-l[(l-Metfayl-2-pynul-2-yl)methylene]amino]-7' 7-l[(l-Metfayl-2-pynul-2-yl)methylene]amino]-7' of MHz) (200 NMR ‘H 9: Figure azabicyclo azabicyclo (40) [4.1.0] heptane