Synthesis of (E)-alpha,beta-unsaturated amides with high selectivity by using samarium diiodide

Stereoselective beta -elimination of 2-chloro-3-hydroxyamides 1 is achieved by using samarium diiodide to yield alpha,beta -unsaturated amides 2, in w hich the C=C bond is di- tri-, or tetrasubstituted. The starting compounds a are easily prepared by reaction of the corresponding lithium enolates of alpha -chloroamides with aldehydes or ketones at -78 degreesC. The influenc e of the reaction conditions and the structure of the starting compounds on the stereoselectivity of the beta -elimination reaction is also discussed.