Asymmetric direct vinylogous carbon–carbon bond formation catalyzed by bifunctional organocatalysts

Abstract

The bifunctional chiral thiourea-tertiary amine organocatalysts have been applied to a direct asymmetric vinylogous Michael addition of α,α-dicyanoolefins to nitroolefins with 2–10 mol % catalyst loadings. The electronic properties of the thiourea-based catalysts have significant influences on this reaction. Moderate to excellent enantioselectivities (57–95% ee) have been achieved with low to good isolated yields through fine tuning the structures of the bifunctional organocatalysts. Much better ees were obtained for some α,α-dicyanoolefinic substrates compared with that catalyzed by modified cinchona alkaloids.