A facile and general sequential elimination/reduction process promoted by samariumdiiodide provides an efficient method for synthesizing saturated esters or amides 3 from readily available starting materials. The reaction involves a beta-elimination of the starting 2-halo-3-hydroxyesters or -amides 1 and subsequent 1,4-reduction of the obtained alpha,beta-unsaturated esters or amides in the presence
Stereoselective beta -elimination of 2-chloro-3-hydroxyamides 1 is achieved by using samarium diiodide to yield alpha,beta -unsaturated amides 2, in which 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 influence of the reaction conditions and the structure of the starting compounds on the stereoselectivity of the beta -elimination reaction is also discussed.
Synthesis of (E)-α,β-Unsaturated Esters and Amides with Total Selectivity Using Samarium Diiodide
作者:José M. Concellón、Juan A. Pérez-Andrés、Humberto Rodríguez-Solla
Sequential Elimination−Cyclopropanation Reactions Promoted by Samarium: Highly Diastereoselective Synthesis of Cyclopropylamides
作者:José M. Concellón、Humberto Rodríguez-Solla、Ricardo Llavona
DOI:10.1021/jo0262098
日期:2003.2.1
trans-Cyclopropanamides were obtained, in high yield, from 2-chloro-3-hydroxyamides by a sequenced elimination-cyclopropanation process promoted by Samarium/diiodomethane or Samarium diiodide and Samarium/diiodomethane.