The direct vinylogous aldol reaction of α-substituted α,β-unsaturated aldehydes with isatins is described. The chemistry provides easy access to valuable 3-substituted 3-hydroxyoxindole derivatives with high stereocontrol and perfect γ-site selectivity. Preliminary mechanistic studies suggest that, depending on the nature of the α-branched enal substituents, two divergent reaction mechanisms can be operating, leading to different products and stereochemical outcomes.
Direct catalytic enantioselective vinylogous Aldol reaction of alpha-branched enals with isatins
Org. Lett. 2012, 14, 5590-5593.