Frontispiece: The Mechanism of Phosphonium Ylide Alcoholysis and Hydrolysis: Concerted Addition of the O−H Bond Across the P=C Bond. Issue 27 (23rd June 2016)

• Record Type: Journal Article
• Authors: Byrne, Peter A.; Gilheany, Declan G.
• Is Part Of: Chemistry. Volume 22:Issue 27(2016)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2016-06-23
• Subjects: alkoxyphosphorane -- concerted additions -- hypervalent compounds -- reaction intermediates -- ylides; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201682762
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract : Ylide Hydrolysis & Alcoholysis The reactions of phosphonium ylides (Ar3 P=CHR′) with alcohols (ROH) and H2 O in protic solvents to give alkoxyphosphorane or hydroxyphosphorane, respectively, generally occur through a two‐step pathway involving a phosphonium hydroxide or alkoxide intermediate. In protic solvents, the p K aH of the ylide is typically higher than the p K a of H2 O or alcohol. In aprotic media, the p K a values of H2 O and alcohols are dramatically higher than in protic media, and yet formation of phosphorane intermediates is still observed. The characteristic high field 31 P NMR signal of an alkoxyphosphorane formed in an aprotic solvent is shown in the image. On the basis of this observation, and other substantial evidence in support of their interpretation from 1D and 2D NMR studies, P. A. Byrne and D. G. Gilheany conclude in their Full Paper onpage 9140 ff. that concerted formation of phosphorane intermediates from ylide+ROH (R=H or alkyl) occurs in any solvent in which the p K aH of the ylide is lower than the p K a of ROH.