Highly enantioselective carbonyl-ene reactions catalyzed by a hindered silyl-salen-cobalt complex

We report here the enantioselective carbonyl-ene reactions of various 1,1-disubstituted and trisubstituted alkenes with ethyl glyoxylate. The reactions are catalyzed by a new Co-salen complex, in which bulky triisobutylsilyl (TIBS) substituents occupy the positions ortho to the phenolic oxygens. This complex catalyzes the reactions under nearly ideal conditions-at room temperature and using catalyst loadings as low as 0.1 mol %-and provides the chiral, homoallylic alcohol products in excellent yields, enantioselectivities, and diastereoselectivities.