Wittig- and Horner–Wadsworth–Emmons-Olefination Reactions with Stabilised and Semi-Stabilised Phosphoranes and Phosphonates under Non-Classical Conditions

Abstract

Developments in the Wittig and Horner-Wadsworth-Emmons (HWE)-olefination of aldehydes and ketones with stabilised phosphoranes or phosphonates provide opportunities for multicomponent reactions and for reactions with greatly reduced solvent requirements. The in situ preparation of phosphonium salts, phosphoranes or phosphonates and carrying out the reaction and product workup in a biphasic medium can greatly facilitate the reactions. Microwave irradiation and ultrasonication can shorten reaction times considerably. Wittig and HWE reactions have also been carried out in the solid phase, with either polymer-bound reagents or in Wittig reactions with reagents adsorbed on silica or alumina. Good Eand Z-selectivity has been achieved, despite the E/Z-directivity of the carbonyl reagent and of the residue linked to the phosphorane moiety.

Facile, Direct Reaction of Benzaldehydes to 3-Arylprop-2-Enoic Acids and 3-Arylprop-2-Ynoic Acids in Aqueous Medium

“…In former times, the Wittig olefination reaction has not been viewed as a green reaction due to its poor atomeconomy. Recently, however, a dedicated effort has seen the development of numerous methods to recycle the toxic triphenylphosphine oxide [17] [68]- [70] that joins older methods [71], and some of them already established in industrial processes [17] [72]. The reaction procedure described above allows for an efficient separation of triphenylphosphine oxide from the mixture upon completion of the reaction by simple filtration.…”

Phosphonium salts and P-ylides

“…A review by Jasem, El-Esawi and Thiemann focused on the use of stabilised and semi-stabilised phosphoranes and phosphonates under non-classical conditions. 274 The mechanism of the Wittig reaction of anisaldehyde with a stabilized ylide was studied by Singleton and coworkers. 275 A combination of 13 C kinetic isotope effects, conventional calculations, and molecular dynamics calculations in a cluster of 53 THF molecules was considered, in order to establish if the reaction proceeds through a concerted or a two-step processes.…”

A novel synthetic approach to glycerophospholipids via Horner–Wadsworth–Emmons reaction of mixed phosphonoacetate

“…[23][24][25][26][27] In the HWE reaction, a water-soluble dialkyl phosphate salt is obtained as a stoichiometric amount of by-product and is disposed of as waste. However, we recently began to investigate the possible use of the HWE reaction for synthesizing glycerophospholipids by focusing on the similarity of chemical structures between dialkyl phosphates and glycerophospholipids.…”