Enantioselective chlorinative aldol reaction of α-substituted acroleins catalyzed by chiral phosphine oxides

Abstract

The enantioselective chlorinative aldol reaction of α-substituted acroleins with aldehydes catalyzed by chiral phosphine oxides is described. A hypervalent silicon complex-derived chloride adds to the α-substituted acroleins to form the corresponding silyl enol ethers in situ, which subsequently reacts with aldehydes to produce the α-chloromethyl aldol adducts bearing a quaternary stereogenic center in good yields and stereoselectivities. When activated by a phosphine oxide catalyst, trichlorosilyl triflate acts as an effective promoter for the chlorinative aldol reaction as well as the chloride source; this discovery enabled the enantioselective chlorinative aldol reaction of α-substituted acroleins.