Novel tandem reactions of ethyl acetoacetate with aromatic aldehydes: product- and stereo-selective formation of highly functionalised cyclohexanones

The five-component tandem reaction of ethyl acetoacetate with aromatic aldehydes in the presence of pyrrolidine affords t(3),t(5)-diaryl-t(4)-[(E)-3-aryl-2-propenonyl]-r(2)-ethoxycarbonylcyclohexanones stereoselectively in good yields presumably via a tandem Knoevenagel condensation-Michael addition-condensation via enamine-deethoxycarbonylation-Michael addition sequence. The same reactants in the presence of DBU led to the formation of t(3)-aryl-r(2),c(4)-bisethoxycarbonyl-c(5)-hydroxy-t(5)-methylcyclohexanones in excellent yields via a tandem Knoevenagel condensation-Michael addition-aldol reaction sequence.