Synthesis of (E)-α,β-Unsaturated Amides with High Selectivity by Using Samarium Diiodide.

Stereoselective β-elimination of 2-chloro-3-hydroxyamides 1 is achieved by using samarium diiodide to yield α,β-unsaturated amides 2, in which the C=C bond is di- tri-, or tetrasubstituted. The starting compounds 1 are easily prepared by reaction of the corresponding lithium enolates of α-chloroamides with aldehydes or ketones at −78 °C. The influence of the reaction conditions and the structure of the starting compounds on the stereoselectivity of the β-elimination reaction is also discussed.