Enantioselective formal hydration of alpha,beta-unsaturated imides by Al-catalyzed conjugate addition of oxime nucleophiles.

The (salen)Al-catalyzed asymmetric conjugate addition of salicylaldoxime to alpha,beta-unsaturated imides is the key step in an efficient and highly enantioselective two-step formal hydration of these electron-deficient olefins. This reaction constitutes the first example of an enantioselective conjugate addition of an oxygen-centered nucleophile to alpha,beta-unsaturated carboxylic acid derivatives. Application of this method to chiral, nonracemic substrates revealed a high level of catalyst-induced diastereoselectivity, underscoring its potential utility for polyketide natural product synthesis.