Synthesis of (E)-alpha,beta-unsaturated esters with total or high diastereoselectivity from alpha,beta-epoxyesters.
[reaction: see text] High stereoselective beta-elimination in 2,3-epoxyesters 1 was achieved using samarium diiodide, yielding alpha,beta-unsaturated esters 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 alpha-chloroesters with aldehydes or ketones at -78 degrees C. The influence of the reaction conditions and the structure of the starting compounds in the stereoselectivity of the beta-elimination reaction is also discussed.
Concellón
José M
JM
Departamento de Química Orgánica e Inorgánica, Facultad de Química Universidad de Oviedo, Julián Clavería, 8, 33071 Oviedo, Spain. jmcg@sauron.quimica.uniovi.es
Bardales
Eva
E