An unexpected tandem enantioselective Michael addition/oxa-nucleophilic rearrangement reaction of β,γ-unsaturated α-keto esters catalyzed by cinchona alkaloids
Cinchona alkaloids were found to catalyze an enantioselectiveMichaeladdition/oxa-nucleophilic rearrangement reaction of β,γ-unsaturated α-keto esters 1 and malonates 2. Using the optimum catalyst quinine 4a, a series of the rearranged products 3 were obtained with up to 98% yield and 82% ee under mild reaction conditions.