Combining Organocatalysis with PhotoOrganocatalysis: Photocatalytic Hydroacylation of Asymmetric Organocatalytic Michael Addition Products

Organocatalysis and photoorganocatalysis are two areas of synthetic methodology that have found wide applications in organic synthesis. Herein, we report a combination of these two stategies, taking advantage of an organocatalytic Michael addition of alpha,alpha-disubstituted aldehydes to maleimides as the first step and a photocatalytic hydroacylation of diisopropyl azodicarboxylate as the second step. Employing an amino acid as the organocatalyst for the asymmetric organocatalytic part and an organic molecule as the photocatalyst, the combination of these two strategies led to the desired products. A number of alkyl- and aryl-substituted maleimides were successfully employed, while the protocol can be used on alpha,alpha-disubstituted aldehydes leading to products in moderate to high yields (44-84%) and excellent enantioselectivities (98-100% ee).