Enantioselective synthesis of multifunctionalized 4H-pyran derivatives using bifunctional thiourea-tertiary amine catalysts

A series of novel chiral multifunctionalized 4H-pyran derivatives were easily accessed via the one-pot asymmetric Michael addition-cyclization reaction between malononitrile and beta,gamma-unsaturated alpha-keto esters catalyzed by chiral bifunctional thiourea-tertiary amine catalysts. With the optimized reaction conditions, the desired products were obtained with 50-68% yields and 72-88% ees. (c) 2009 Elsevier Ltd. All rights reserved.