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.
Thiourea-Catalyzed Enantioselective Cyanosilylation of Ketones
作者:Douglas E. Fuerst、Eric N. Jacobsen
DOI:10.1021/ja052511x
日期:2005.6.1
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.
Stereoselective nucleophilic addition to imines catalyzed by chiral bifunctional thiourea organocatalysts
such bifunctional chiral molecules, either neutral or protonated species, was investigated in the addition of acetylacetone to β-nitrostyrene as a model reaction. Using the best conditions, high yields and enantioselectivities of up to 85% were obtained. The same metalfreecatalysts were then employed in the addition of activated nucleophiles to imines: in the reaction of 1,3-diketones with N-CBz imines