Highly active nickel catalysts for enantioselective reductive alkenylation of N-sulfonyl aldimines

Chiral nickel complexes of bis(oxazoline)s serve as highly active catalysts for an enantioselective reductive alkenylation of N-sulfonyl and N-sulfamoyl aldimines, using readily available alkenyl bromides and triflates as reagents. The new method is readily scalable with low loadings of nickel catalysts, as low as 0.2 mol%. The reaction condition is almost neutral and tolerated polar groups of esters, thioethers, carbamates, heterocyclic pyridine and quinoline, and weakly acidic alcohols. Mechanistically, density functional theory (DFT) calculations reveal that alkenyl transfer to N-sulfonyl imines occurs on nickel catalysts via a classical 1,2-migratory insertion.