Asymmetric 1,4-Reductions of Hindered β-Substituted Cycloalkenones Using Catalytic SEGPHOS−Ligated CuH

Abstract

The reagent combination of catalytic amounts of copper hydride ligated by a nonracemic SEGPHOS ligand leads in situ to an extremely reactive species capable of effecting asymmetric hydrosilylations of conjugated cyclic enones in very high ees. An unprecedented substrate-to-ligand ratio as high as 275 000:1 for this transformation has been documented. [reaction: see text]