Flash vacuum pyrolysis of 2-(2-vinylstyryl)furan derivatives via electrocyclization followed by dehydrogenation will give 2-(2-naphthalen-2-yl)furan analogues, on the other hand, FVP of 2-(2-vinylstyryl)furan derivatives via electrocyclization followed by [1,5]-H shift will give 3-(2-furyl)-1,2-dihydronaphthalene analogues. FVP of 2-[2-(4-methoxyphenyl)vinyl]benzo[b]thiophene gave three products: trans-4-(2-benzo[b]thiophen-2-ylvinyl)phenol, benzo[b]naphtha[1,2-d]thiophen-2-ol and 1H-6-thiacyclopenta[c]fluorene.

The first chapter describe the pyrolytic and photolytic studies of substituted styrylarenes. Flash vacuum pyrolysis (FVP) of (2-(4-methoxystyryl)-N-methylindole) (18) gave (4-vinylphenol) (81)¡B (7-methyl-7H-benzo[c]carbazole) (82)¡B (benzo[c]carbazole) (83)¡B (1,6-dihydrocyclopenta[c]carbazole) (84) and (3,6-dihydrocyclopenta- [c]carbazole) (84'). FVP of 2',3,5-trimethoxystilbene (31) gave 2-(3,5-dihydroxyphenyl)benzo[b]furan) (26) and 2-(3,5-dimethoxy- phenyl)benzo[b]furan (95). FVP of 2-methoxy-4-(methoxymethyl)-1- [2-(4-methoxyphenyl)-1-methylvinyl]benzene (33) gave [2-(4- methoxyphenyl)-3-methylbenzofuran-5-yl]methanol (104)¡B4-(3,5- dimethylbenzofuran-2-yl)phenol (105) and 2-(4-hydroxyphenyl)-3- methylbenzofuran-5-carbaldehyde (106). FVP of 2-(2-chlorostyryl)- benzo[b]furan (44) ¡B2-(2-chlorostyryl)benzo[b]thiophene (45) and 2-(2-chlorostyryl)-N-methylindole (46) gave benzo[b]naphtha[1,2-d]- furan (116)¡Bbenzo[b]naphtho[1,2-d]thiophene (117)¡B7-methyl-7H- benzo[c] carbazole (82) and benzo[c]carbazole (83). FVP of 2-chloro-N-(N-methylindol-2-ylmethylene)aniline (71) gave N-methylindole-2-carbonitrile (124)¡B 7H-indolo[2,3-c]quinoline (125) and indolo[1,2-a]quinoxaline (126). FVP of 2-methoxy -N-(N-methyl- indol-2-ylmethylene)aniline (72) gave N-methylindole-2-carbonitrile (124) ¡B 2-(N-methylindol- 2-yl)benzoxazole (132) and 2-hydroxy- benzonitrile (133). FVP of 2-methylthio-N-(phenylmethylene)aniline (73)¡B2-methylthio-N-(furylmethylene)aniline (74)¡B2-methylthio-N- (benzo[b]thiophen-2-ylmethylene)aniline (75) and 2-methylthio-N- (N-methylindol-2-ylmethylene)aniline (76) gave 2-phenylbenzothiazole (143)¡B2-furylbenzothiazole (144)¡B2-benzo[b]thiophen-2-ylbenzo- thiazole (145)¡B2-(N-methylindol-2-yl)benzothiazole (146)¡B2-(1H- indol-2-yl)benzothiazole (147) and benzothiazole (148).Such a method, via oxygen-carbon bond disconnecting, can synthesize efficiently a nature product, stemofuran A 26. Photolytic study of 2',3,5-trimethoxystilbene (31) gave 1,5,7- trimethoxyphenanthrene) (101). Photolytic studies of 2-(2-chloro- styryl)benzo[b]furan (44) ¡B2-(2-chlorostyryl)benzo[b]thiophene (45) and 2-(2-chlorostyryl)-N-methylindole (46) gave benzo[b]naphtha- [1,2-d]furan (116) and 4-chlorobenzo[b]naphtha[1,2-d]furan (120)¡Bbenzo[b]naphtho[1,2-d]thiophene (117) and 4-chlorobenzo[b]naphtha- [1,2-d]thiophene (120) ¡B7-methyl-7H- benzo[c]carbazole (82) and 4-chloro-7-methyl-7H-benzo[c]carbazole (121). Photolytic studies of 2-methylthio-N-(phenylmethylene)aniline (73)¡B2-methylthio- -N-(furylmethylene)aniline (74)¡B2-methylthio-N-(benzo[b]thiophen-2- ylmethylene)aniline (75) and 2-methylthio-N-(N-methylindol-2- ylmethylene)aniline (76) gave 2-phenylbenzothiazole (143)¡B2-furyl- benzothiazole (144)¡B2-benzo[b]thiophen-2-ylbenzo- thiazole (145)¡B2-(N-methylindol-2-yl)benzothiazole (146)¡B2-(1H-indol-2-yl)benzo- thiazole (147) and 2-(2,4-dimethoxyphenyl)benzothiazole) (60f). Such a method has the potential for preparing drugs and application on material science. (¤G)FVP of 2-inden-1-ylidenemethylthiophene (24) and 2-inden-1-ylidene- methylfuran (25) gave the cyclized products 2-(2'-thienyl)naphthalene (29) and 2-(2'-furyl)naphthalene (32).

Universiẗat, Diss., 2003--Münster (Westfalen).

The ability to generate chiral building blocks is of paramount importance to organic chemists. This problem presents itself most notably at the interface of chemistry and biology, where molecules of only a single enantiomer can induce function to many biological systems. In this context, recent developments in the field of organocatalysis, most notably the employment of chiral N-heterocyclic carbenes (NHCs) have shown much promise. Our group has recently shown that one possible chiral NHC catalyzed Stetter cyclization product of a conjugated triene, a highly functionalized cyclopentenone, contains both a chiral center and an adjacent conjugated diene. This structure can be easily elaborated to a bicyclic structural motif present in some biologically active natural products from the ginkgolide family, and is difficult to access by other means. The synthesis of novel vinyl stannanes and other coupling substrates involved in the development of the aforementioned reaction discovery are described in this report.

ABSTRACT This thesis describes an investigation into the role of acetylenic and allenic precursors in the formation of the important aroma compound β-damascenone (1). Chapter 1 provides an introduction to the subject, beginning with a brief history of the Australian wine industry which began with the first fleet’s arrival in 1788. Many of the various volatile compounds found in wine are then discussed, with particular emphasis on β-damascenone (1). Some previous syntheses of 1 are summarised, as well as the in vivo generation of this compound, and also the role of glycoconjugation in nature. The chapter concludes with the aims of the present work. Chapter 2 covers the synthesis of the suspected acetylenic precursor 9-hydroxymegastigma-3,5-dien-7-yne (36), which was prepared by the addition of 3-butyn-2-ol to 2,6,6-trimethylcyclohex-2-en-1-one, followed by a conjugate dehydration reaction. The synthetic sample of 36 was shown to be identical to a compound previously observed in the hydrolysate of 3,5,9-trihydroxymegastigma-6,7-diene (31). Upon acid hydrolysis, 36 produced > 90% β-damascenone (1). Chapter 3 outlines the synthesis and hydrolysis of the C9 glycoside 43, which was prepared by a modified Koenigs-Knorr procedure on aglycone 36. Diastereomerically pure samples of each of the two possible glycosides were synthesised from corresponding enantiomerically pure samples of 36, which in turn were prepared by the use of either (R) or (S) 3-butyn-2-ol. Detailed hydrolytic studies (at 25 ºC) were conducted on both the aglycone and the two glycosides: the half lives of conversion of 36 into 1 were 40 hours and 65 hours at pH 3.0 and pH 3.2 respectively; the (9R) diastereomer of 43 had half-lives of 3 days and 6 days, respectively at the same pH values, whereas the (9S) diastereomer had half lives of 3.5 days and 6.5 days, respectively at the same pH values. The synthesis of the other suspected precursor, megastigma-4,6,7-triene-3,9-diol (35) is covered in Chapter 4. This allene was prepared by addition of 3-butyn-2-ol to phorenol, with the allene function generated by reaction with lithium aluminium hydride. By using (3S)-phorenol and both (R) and (S) 3-butyn-2-ol, four different diastereomers of 35 were prepared and characterised. The (3S, 6R, 9S)-isomer of 35 was also found to be identical to a compound previously observed in the hydrolysate of (31). A detailed hydrolytic study of the four synthetic isomers of 35 is contained within Chapter 5. This study revealed that each of the four isomers underwent rapid epimerisation at 25 ºC and pH 3.0. Careful analysis of the four product mixtures by chiral GC-MS revealed that this epimerisation was occurring exclusively at C3. The complete absence of 3-hydroxydamascone (2) from any of the hydrolysates required a re-appraisal of the mechanism of in vivo formation of β-damascenone (1), which forms the focus of the second half of this chapter. The experimental procedures (materials and methods) for all work covered in chapters 2-5 are located in Chapter 6.