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Theoretical study of the mechanism of the Wittig reaction: Ab initio and MNDO-PM3 treatment of the reaction of unstabilized, semistabilized, and stabilized ylides with acetaldehyde

✍ Scribed by Albeiro A. Restrepo-Cossio; Hermisul Cano; Frank Marí; Carlos A. Gonzalez

Publisher
John Wiley and Sons
Year
1997
Tongue
English
Weight
313 KB
Volume
8
Category
Article
ISSN
1042-7163

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✦ Synopsis

In this study, we describe the results of ab initio (HF and MP2) and MNDO-PM3 calculations on the model reactions of unstabilized (Me 3 P‫ס‬CH-CH 3 ), semistabilized (Me 3 P‫ס‬CH-CϵCH), and stabilized (Me 3 P‫ס‬CH-CϵN) ylides with acetaldehyde to form their respective Z and E olefins and trimethylphosphine oxide. These reactions occur in three stages: oxaphosphetane formation, oxaphosphetane pseudorotation, and oxaphosphetane decomposition. The calculated barriers for these processes vary considerably depending on the level of theory employed (ab initio vs. MNDO-PM3 or HF vs. MP2 at the ab initio level). However, self-consistent geometries of reactants, intermediates, transition states and products are Dedicated to Prof. William E. McEwen on the occasion of his seventy-fifth birthday.

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