Michael additions in water of ketones to nitroolefins catalyzed by readily tunable and bifunctional pyrrolidine-thiourea organocatalysts

摘要

An operationally trivial and environmentally benign procedure for direct Michael addition has been developed.The reaction of various ketones with nitroolefins can be performed in water to afford the corresponding nitro compounds in high yields in the presence of a pyrrolidine-thiourea organocatalyst at 35 deg C.The reaction exhibits a high stereoselectivity,with high enantioselectiv-ities (up to 99%) as well as diastereoselectivities (up to 99:1) being achieved under the optimal conditions.