Organocatalysts of tertiary-phosphines and amines catalyzed reactions of α-keto esters with cyclopent-2-enone

The reaction of α-keto esters with cyclopent-2-enone catalyzed by tertiary-phosphines provides the corresponding Baylis–Hillman adducts. Among the catalysts, diphenylmethylphosphine was found to be the most effective promoter allowing the reaction to proceed smoothly at room temperature and to give the corresponding adducts in higher yields in the presence of p-nitrophenol. Whereas, the similar reaction of α-keto esters with cyclopent-2-enone catalyzed by tertiary-amine of DBU furnishes the corresponding aldol adducts with syn-configuration exclusively.