An Enantioselective Synthesis of Substituted Cyclohexanone Derivatives with an All-Carbon Quaternary Stereocenter by Using an Organocatalytic Asymmetric Domino Double Michael Addition

A cinchona alkaloid-catalyzed enantioselective method has been developed for the synthesis of densely functionalized cyclohexanone derivatives with excellent diastereoselectivities and good enantioselectivities [diastereomeric ratio (dr) >95:5 and an enantiomeric excess (ee) value up to 86%]. The products have an all-carbon quaternary center that contains both a cyano and ester group flanked by two vicinal tertiary stereocenters. By using a one-pot procedure, the tautomeric products were then transformed into the corresponding pyrazoles, which were obtained as single isomers in good yields. A quinine-catalyzed enantioselective method has been reported to generate polysubstituted cyclohexenes that have an all-carbon quaternary center. The resulting isomeric product mixtures were easily converted into the corresponding pyrazoles through a one-pot procedure.