Enantioselective, Organocatalytic Reduction of Ketones using Bifunctional Thiourea-Amine Catalysts
摘要:
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.
Discovery of Bifunctional Thiourea/Secondary-Amine Organocatalysts for the Highly Stereoselective Nitro-Mannich Reaction of α-Substituted Nitroacetates