Generation of Chiral Carbanions by Chirality Transfer

该项目的目的是建立从环氧化物到碳负离子的手性转移的可行性。转移的关键特征涉及我们先前开发的环氧硅烷重排，其中γ-金属化的α，β-环氧硅烷经历阴离子诱导的开环，然后Brook重排得到β-甲硅烷氧基烯丙基阴离子。为了实现手性转移，我们进行了以下实验：1.通过Brook重排反应合成八元碳环和杂环; 2.环氧硅烷重排反应的机理研究; 3.环氧硅烷重排级联成环反应的研究; 4.五元碳环和杂环的形成和稳定性研究; 5.环氧硅烷重排反应的机理研究; 6.环氧硅烷重排反应的机理研究; 7.环氧硅烷重排反应的机理研究; 8.环氧硅烷重排反应的机理研究; 8.环氧硅烷重排反应的机理研究; 8.环氧硅烷重排反应的机理研究; 9.环氧硅烷重排反应的机理研究; 10.环氧硅烷重排反应的机理研究; 11.环氧硅烷重排反应的机理研究; 12.环氧硅烷重排反应的机理研究; 13.环氧硅烷重排反应的机理研究; 14.环氧硅烷重排反应的机理研究; 15.环氧硅烷重排反应的机理研究; 15.环氧硅烷重排反应的机理研究; 16.环氧硅烷重排反应的机理研究; 17.环氧硅烷重排反应的机理研究; 18.环氧硅烷重排反应的机理研究; 18.环氧硅烷重排反应的机理研究配位硅酸盐中间体5.通过[2，3]-Wittig重排的环氧硅烷重排产生的手性碳负离子的捕获从这些实验中，我们得到了以下结果：1.我们证明了在Brook重排介导下，手性从环氧化物转移到远程位置的可能性。3 + 4]环化2.带有γ-甲苯基的α，β-环氧硅烷可以作为丙烯醛β-阴离子的等价物3.由环氧化合物手性转移生成的手性碳负离子可以通过[2，3]-Wittig重排而不发生外消旋化而被捕获4.我们发现由环氧硅烷通过Brook重排手性转移可以生成手性非外消旋的α-腈烯丙基碳负离子，并且它们借助于氨基甲酰基的螯合作用而具有构型稳定性，以允许在通过双分子过程完全外消旋化之前进行捕获。

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.