The Stereochemistry of the Phosphonate Modification of the Wittig Reaction

Abstract

A number of olefins prepared by the phosphonate carbanion modification of the Wittig reaction were shown to have trans configurations. Vapor phase chromatography of the intact reaction mixtures showed, at most, only trace amounts of cis isomers. To determine the degree of stereospecificity of the reaction under adverse circumstances, several experiments were devised with systems which, based on the generally accepted reaction mechanism,1•2 34567should be more favorable for the preparation of cis olefins. In only one case, however, was a significant amount of a cis isomer formed [6.4% cis-l,2-{ 1,1 z-dinaphthyl)ethylene in a 1:10 cis-trans mixture], demonstrating the great stereospecific tendency of the reaction. Possible interpretations of the observed differences in stereospecificity of olefin formation from phosphonate carbanions and phosphorus ylids are discussed.

Optimization of peptidyl allyl sulfones as clan CA cysteine protease inhibitors

“…Trans-vinyl sulfones 1-4 were prepared as previously described via Wadsworth-Emmons chemistry using chiral amino acid aldehydes and a sulfonylphosphonate 40,47 . Phe-OMe was reacted with morpholinocarbonyl chloride and saponified to carboxylic acid 5 (Mu-Phe-OH) in 71% overall yield (Scheme 1).…”

Spectroscopic, structural and textural properties of CaO and CaO–SiO2 materials synthesized by sol–gel with different acid catalysts

“…Alkaline earth oxides with strong surface basic sites, exhibits good catalytic properties [1,2], and have several applications in the chemical industry for the manufacture of perfumes, fragrances, analgesics, insecticides, carotenoids, pheromones, pharmaceuticals, and prostaglandins [3,4], in processes where the Wadsworth-Emmons reactions are involved [5], and for aldehydes dimerization on the Tishchenko reaction [2,6]. Nanocrystalline CaO was found to be a good catalyst in the synthesis of urea from ethylene carbonate [7]; for biodiesel production from soybean oil, poultry fat [8] and sunflower oil [9,10] by the transesterification reaction.…”

Kinetic studies on the reaction between substituted benzyl phosphonates and substituted benzaldehydes

“…2 The mechanism of Wittig-Horner reaction has been well studied. [3][4][5] But a great part of these was based on the stereochemistry of olefin formation until the reaction kinetics for the reaction ofphosphoryl-stabilized carbanions and substituted benzaldehydes was studied by Larson and Aksnes. They proposed a reaction mechanism from these kinetic studies which involves a fourmembered cyclic structure as the reactive intermediate.…”