Enantioselective Cyanosilylation of α, α-Dialkoxy Ketones Catalyzed by Proline-Derived in-Situ-Prepared N-Oxide as Bifunctional Organocatalyst

摘要

Bifunctional N, N'-dioxide catalysts have been developed for highly enantioselective cyanosilylation of α,α-dialkoxy ketones. This process, catalyzed by in-situ-prepared proline-derived N, N'-dioxide 2b, produced the corresponding cyanohydrin trimethylsilyl ethers in excellent yields (up to 99%) with high enantioselectivities (up to 93% ee). A reasonable mechanism was proposed according to the observation of the linear effect, ~1H NMR spectra, isolated cyanohydrin, and the roles of the NH and N-oxide moieties of the catalyst.