Highly selective reaction of alpha-halo-alpha,beta-unsaturated esters with ketones or aldehydes promoted by SmI2: an efficient alternative access to Baylis-Hillman adducts.

A samarium diiodide promoted addition of aromatic or aliphatic beta-substituted-alpha-halo-alpha,beta-unsaturated esters 1 or 3 to both ketones (in THF) and aldehydes (in acetonitrile) led to (Z)-2-(1-hydroxyalkyl)-2,3-alkenoates 2 and 4 in good yields and very high stereoselectivity. This method constitutes an efficient and valuable alternative to the synthesis of Baylis-Hillman adducts. A mechanism is proposed to explain this transformation.