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

Abstract

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 1 are easily prepared by reaction of the corresponding lithium enolates of alpha-chloroamides with aldehydes or ketones at - 78 degrees C. The influence of the reaction conditions and the structure of the starting compounds on the stereoselectivity of the beta-elimination reaction is also discussed.

The Development of a Stereoselective Method for the Synthesis of Tetrasubstituted Derivatives of α,β‐Unsaturated Carboxylic Acids

“…Our first attempt involved the stereoselective synthesis of tetrasubstituted α , β ‐unsaturated amides 2a using the Concéllon et al . procedure . This method is based on reductive elimination of α , β ‐epoxyamides or 2‐chloro‐3‐hydroxyamides using SmI 2 .…”

A Novel Method for the Synthesis of α,β-Unsaturated Amides Mediated by Samarium Diiodide

“…Melting points are uncorrected. 1 H NMR spectra were recorded on a Bruker 400 MHz instrument as CDCl 3 solutions using TMS as internal standard. Chemical shifts (d) are reported in ppm and coupling constants J are given in Hz.…”

“…Recently, Concellón et al 1 reported a stereoselective b-elimination of 2-chloro-3-hydroxyamides using samarium diiodide (SmI 2) to synthesize a,b-unsaturated amides. Herein we wish to describe an alternative way employing SmI 2 to prepare a,b-unsaturated amides from nitro compounds and a,b-unsaturated esters.…”

Complete Stereospecific Cyclopropanation of α,β-Unsaturated Amides Promoted by Sm/CH2I2 We acknowledge financial support from II Plan Regional de Investigación del Principado de Asturias (PB-EXP01-11) and Ministerio de Ciencia y Tecnología (BQU2001-3807). We thank Dr. Francisco J. González for valuable discussions and Robin Walker for revising the English manuscript. J.M.C. thanks Carmen Fernández-Flórez for her time. H.R.S. thanks Principado de Asturias for a predoctoral fellowship.

“…[11] Imamoto et al described the cyclopropanation of lithium enolates derived from ketones by using SmI 2 / CH 2 I 2 . [13] Recently, we described the SmI 2 -promoted highly diastereoselective synthesis of vinyl halides, [14] a,b-unsaturated esters [15] and amides, [16] deuterated b,g-unsaturated esters, [17] and vinylsilanes. [13] Recently, we described the SmI 2 -promoted highly diastereoselective synthesis of vinyl halides, [14] a,b-unsaturated esters [15] and amides, [16] deuterated b,g-unsaturated esters, [17] and vinylsilanes.…”