Organocatalytic Stereoselective Epoxidation of Trisubstituted Acrylonitriles
摘要:
The first diastereospecific and enantioselective epoxidation of trans-2-aroyl-3-arylacrylonitriles by means of the commercially available diaryl L-prolinol/tert-butyl hydroperoxide system has been developed. These diversely functionalized epoxides were obtained in excellent yield (up to 99%), complete diastereoselectivity for the transisomer, and good enantioselectivity (up to 84% ee). Highly enantioenriched epoxides can be easily obtained after a single crystallization (ee > 90%).
Asymmetric Synthesis of Trisubstituted Tetrahydrothiophenes Bearing a Quaternary Stereocenter via Double Michael Reaction Involving Dynamic Kinetic Resolution
The stereoselective synthesis of highly functionalized tetrahydrothiophenes bearing threecontiguousstereocenters, one of them quaternary, can be achieved by reacting trans-α-cyano-α,β-unsaturated ketones and trans-tert-butyl 4-mercapto-2-butenoate in the presence of a readily available amine thiourea. The products are obtained in high yield, good diastereoselectivity, and excellent enantioselectivity