Enantioselective allylation of alkyl glyoxylates catalyzed by (salen)chromium(III) complexes

The enantioselective addition of allylstannanes and allylsilanes to alkyl glyoxylates of type 1, catalyzed by chiral (salen)Cr(III) complexes 3, has been studied. We have found that the reaction proceeded smoothly for low loading (1–2 mol %) of (1R,2R)-(salen)Cr(III)BF4 3a or (1R,2R)-(salen)Cr(III)ClO4 3c, and allyltributyltin under simple, undemanding conditions, affording (R)-2-hydroxypent-4-enoic acid esters 2 in good yield (61–90%) and enantioselectivity (58–76% ee).