A Convenient Synthesis of (E)-α,β-UnsaturatedEsters with Total Stereoselectivity Promoted by CatalyticSamarium Diiodide

Synthesis of (E)-α,β-unsaturated esters in high yields and with total stereoselectivity is achieved from α-halo-β-hydroxy esters promoted by catalytic amounts of SmI 2 . The starting compounds were easily prepared from α-halo esters and aldehydes as a mixture of stereoisomers. A mechanism is proposed to explain this samarium(II)-promoted catalytic β-elimination reaction.