SYNTHESIS OF ISOTOPICALLY LABELLED OLEFINS VIA THE WITTIG REACTION

The Wittig Reaction

The Wittig Reaction

This so-called Wittig reaction has a number of advantages over other olefination methods; in particular, it occurs with total positional selectivity (that is, an alkene always directly replaces a carbonyl group). By comparison, a number of other carbonyl olefination reactions often occur with double-bond rearrangement. In addition, the factors that influence Eand Z-stereoselectivity are well un...

Organocatalytic, enantioselective synthesis of benzoxaboroles via Wittig/oxa-Michael reaction Cascade of α-formyl boronic acids.

An unprecedented enantioselective synthesis of 3-substituted benzoxaboroles has been developed. An in situ generated ortho-boronic acid containing chalcone provides the chiral benzoxaboroles via an asymmetric oxa-Michael addition of hydroxyl group attached to the boronic acid triggered by the cinchona alkaloid based chiral amino-squaramide catalysts. In general, good yields with good to excelle...

Synthesis and decarboxylative Wittig reaction of difluoromethylene phosphobetaine.

A key intermediate, difluoromethylene phosphobetaine, in the Wittig reaction of ClCF2CO2Na-Ph3P with aldehydes was synthesized and characterized, which confirmed the reaction mechanism. The decarboxylation of this stable intermediate was a convenient approach for Wittig difluroolefination. Its reactivity could be adjusted by the modification of the substituent on the phosphorus.

Mechanism of the Phospha-Wittig–Horner Reaction**

General. All reactions were performed under argon using Schlenk techniques. Diethyl ether and THF were freshly distilled from sodium/benzophenone prior to use. 1 H, 13 C and 31 P spectra were recorded on a 400 MHz and 300 MHz spectrometers. Chemical shifts (ppm) were reported and referenced to the internal signal of residual protic solvent. High resolution mass spectral analyses (HRMS) were per...