Generation of Chiral Carbanions by Chirality Transfer

这个项目是为了确定手性从环氧化物转移到碳负离子的可行性。转移的关键特征包括我们先前开发的环氧硅烷重排，其中γ-金属化的α，β-环氧硅烷经历了阴离子诱导的开环，然后Brook重排得到β-硅氧基烯丙基阴离子。为了实现手性转移，我们进行了以下实验：1.通过Brook重排反应生成八元碳环和杂环化合物.2.环氧硅烷重排反应的机理研究.3.环氧硅烷重排反应的级联成环反应.4.五配位硅酸盐中间体的形成和稳定性研究.5.通过[2，3]-Wittig重排反应捕获环氧硅烷重排生成的手性碳负离子.通过这些实验，我们得到了以下结果.1.我们论证了在Brook重排反应中，手性从环氧化物转移到远程位置的可能性.2.α，Wittig含有β-甲苯基的γ-环氧基硅烷可以作为丙烯醛β-阴离子的等价物。3.由环氧化物手性转移生成的手性碳负离子可以被[2，3]-Wittig重排捕获而无需消旋。4.我们发现手性非外消旋α-丙烯腈基碳负离子可以通过Brook重排从环氧基硅烷手性转移而生成，并且它们具有构型稳定性，在双分子过程中通过氨基甲酰基的螯合作用使其能够在完全消旋之前被捕获。

This project was conducted to establish the feasibility of chirality transfer from epoxide to a carbanion. The key feature of the transfer involves our previously-developed epoxysilane rearrangement in which γ-metalated α,β-epoxysilane undergoes anion-induced ring opening followed by Brook rearrangement to give β-siloxy allyl anion. To realize the chirality transfer, we have conducted the following experiments.1.Development of eight-membered carbocycles and heterocycles by Brook rearrangement-mediated [3 + 4] annulation.2.Mechanistic studies of the epoxysilane rearrangement.3.Development of cascade-type ring-forming reactions using the epoxysilane rearrangement.4.Studies on the formation and stability of five-coordinated silicate intermediates.5.Trap of a chiral carbanion generated via the epoxysilane rearrangement by [2,3]-Wittig rearrangement.From these experiments, we obtained the following results.1.We demonstrated the possibility of chirality transfer from epoxide to remote positions in Brook rearrangement-mediated [3+4] annulation2.α,β-Epoxysilanes bearing a γ-tolyl group can function as an acrolein β-anion equivalent.3.Chiral carbanions generated by chiral transfer from epoxide can be trapped by [2,3]-Wittig rearrangement without racemization.4.We have found that chiral nonracemic α-nitrile allylic carbanions can be generated by chirality transfer from epoxysilanes via Brook rearrangement, and they have configurational stability with the aid of chelation by a carbamoyl group to allow trapping before a complete racemization by bimolecular processes.