New possible ionic structures in Wittig reaction: Analysis of stability and rotation barriers by semiempirical PM3 method

• Published in: International journal of quantum chemistry Vol. 107; no. 8; pp. 1782 - 1793
• Main Authors: Mracec, Maria, Pascariu, Aurelia, Berger, Stefan, Mracec, Mircea
• Format: Journal Article
• Language: English
• Published: Hoboken Wiley Subscription Services, Inc., A Wiley Company 01.07.2007
• Subjects: ionic intermediary structures; PM3 method; Wittig reaction
• ISSN: 0020-7608; 1097-461X
• DOI: 10.1002/qua.21298

For the Wittig reaction between butylidentriphenylphosphorane and benzaldehyde studied previously using NMR spectroscopy, three ionic intermediates have been proposed in order to explain the “stereochemical drift” (different ratio in oxaphosphetane stereoisomers compared with the ratio of the final Z/E olefins). In this paper, the PM3 semiempirical MO method was applied on the proposed ionic intermediates. Two of the ionic intermediates could lead to a shift of the reaction towards the final products, olefins and phosphine oxide, while the third intermediate could be implicated in a retro‐Wittig reaction. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007