Stereodivergent conjugate reduction of α-substituted α,β-unsaturated N-sulfinyl ketimines: flexible access to challenging acyclic β,β-disubstituted enesulfinamides

Abstract

A stereoselective 1,4-reduction protocol for α-substituted α,β-unsaturated N-tert-butanesulfinyl ketimines has been developed, providing a flexible pathway to various geometry-defined acyclic β,β-disubstituted enesulfinamides featuring two electronically and sterically similar β-substituents. The reductant-controlled stereodivergent synthesis of both (Z)- and (E)-geometric isomers of these challenging enesulfinamides is achieved using L-Selectride and InBr₃/nBu₃SnH, respectively. This dual reductive approach enables the selective access to either geometric isomer from the CC bond position isomers of α,β-unsaturated ketimines. The utility of this method is exemplified through the enantioselective total synthesis of (–)-daucene, showcasing its synthetic applicability.