Masters Thesis

Conjugate additions and reductive transformations of fulvenes and 6-vinylfulvenes

Fulvenes are a group of cross-conjugated compounds that have been of interest due to their diverse chemical and physical properties. Since the discovery of fulvenes by Thiele in the 1900s, and improved synthetic methods, fulvene chemistry has been explored and applications in organometallic chemistry and natural product synthesis have been unveiled. Herein, we disclose our results on the reactions of fulvenes and 6-vinylfulvenes with carbon nucleophiles and reducing agents. For this study, the carbon nucleophiles selected includes the carbon acids nitromethane and ethyl nitroacetate, furthermore, the reducing agent consists of UAIH4. Moreover, selective diazene reduction of fulvenes has been explored in the hopes o f gaining a convenient access to 1,2-dihydrofulvenes. Nitronate anion additions onto regular fulvenes proved to be highly dependent on the C6-substitution pattern of the fulvene: 6,6-disubstituted fulvenes gave spiro[2.4]hepta-4,6-dienes whereas with 6-monosubstituted fulvenes the cyclopropanation was not completed, giving rise to 1- and 2-substituted cyclopentadienes. Due to the improved preparative methods of 6- vinylfulvenes, their reactivity was examined with three nucleophiles because 6- vinylfulvenes have two electrophilic sites, at the C6 and C8 position. The nucleophilic additions onto 6-vinylfulvenes, for the most part, occurred by a 1,4-conjugate addition with the carbon nucleophiles and UAIH4, however, 1,2-additions were observed with a few 6- vinylfulvene derivatives. In addition, the vinyl cyclopentadiene isomers derived from 6- vinylfulvene with UAIH4 were employed towards the synthesis of 2-vinylsubstituted fulvenes and isolated in moderate to excellent yields. Moreover, fulvene diazene reduction occurred by a mono-selective endocyclic manner and 1,2-dihydrofulvenes were isolated in moderate to excellent yields.

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