Thiourea-Catalyzed Enantioselective Cyanosilylation of Ketones
摘要:
The new chiral amino thiourea catalyst 3d promotes the highly enantioselective cyanosilylation of a wide variety of ketones. The hindered tertiary amine substituent plays a crucial role with regard to both stereoinduction and reactivity, suggesting a cooperative mechanism involving electrophile activation by thiourea and nucleophile activation by the amine.
Enantioselective, Organocatalytic Reduction of Ketones using Bifunctional Thiourea-Amine Catalysts
作者:De Run Li、Anyu He、J. R. Falck
DOI:10.1021/ol100365c
日期:2010.4.16
Prochiral ketones are reduced to enantioenriched, secondary alcohols using catecholborane and a family of air-stable, bifunctional thiourea amine organocatalysts. Asymmetric induction is proposed to arise from the in situ complexation between the borane and chiral thiourea amine organocatalyst resulting in a stereochemically biased boronate amine complex. The hydride in the complex is endowed with enhanced nucleophilicity while the thiourea concomitantly embraces and activates the carbonyl.