Synthesis Of Silyl Vinylketenes And Their [4+1] Annulation

Silyl vinylketenes have attracted more and more attention due to its novelty and complexity. In the past ten years, silyl vinylketenes have been utilized as versatile four-carbon building blocks in synthesis of highly substituted carbocyclic and heterocyclic compounds via [4+1] and [4+2] annulations.The classical synthetic method to silyl vinylketenes is the Wolff rearrangement ofα'-silyl-α'-diazo-α,β-unsaturated ketones. This approach contains two steps and involves handling of the hazardous diazo compounds. In addition, cyclopentenones are common structural units in bioactive natural products and useful building blocks. While various approaches have been developed for construction of this important ring system, only a few [4+1] annulations to this five-membered carbocycles have been reported to date.My research will focus on new methodology development for synthesis of silyl vinylketenes and discovery of new [4+1] annulation for construction of cyclopentenones.Firstly, various silyl vinylketenes have been prepared via the thermal reaction of Fischer carbene complexes with trialkylsilyl substituted alkynes.Secondly, a new [4+1] annulation strategy based on the reaction of silyl vinylketenes with K(o|¨)brich reagents has been developed. Various highly substituted cyclopentenones have been prepared via this new methodology and the reaction mechanism has also been studied.Thirdly, the reaction of silyl vinylketenes with tert-butyl isocyanide turned out to be another efficient [4+1] annulation procedure for construction of the cyclopentenones with an exocyclic (Z)-imine moiety. The proposed mechanism of this reaction has also been given out.