Catalytic Asymmetric Diels-Alder Reaction of Quinone Imine Ketals: A Site-Divergent Approach

The catalytic asymmetric Diels–Alder reaction of quinone imine ketals with diene carbamates catalyzed by axially chiral dicarboxylic acids is reported herein. A variety of primary and secondary alkyl‐substituted quinone derivatives which have not been applied in previous asymmetric quinone Diels–Alder reactions could be employed using this method. More importantly, we succeeded in developing a strategy to divert the reaction site in unsymmetrical 3‐alkyl quinone imine ketals from the inherently favored unsubstituted CC bond to the disfavored alkyl‐substituted CC bond. Here or there? Axially chiral dicarboxylic acids serve as the catalyst in the Diels–Alder reaction between quinone imine ketals and diene carbamates. A strategy is also developed to divert the reaction site in unsymmetrical 3‐alkyl quinone imine ketals from the inherently favored unsubstituted CC bond to the disfavored alkyl‐substituted CC bond.