Computational Study of the Substitution Effect on the Mechanism for the Aza‐ and Arsa‐Wittig Reactions

Abstract

The aza-and arsa-Wittig reactions HM=PH 3 + O=CHX ® HM=CHX + O=PH 3 (M = N, As; X = H, F, Cl, Me, OMe, NMe 2 , CMe 3 ) were examined using the density functional theory calculations. All of the structures were completely optimized at the B3LYP/6-311++G** level of theory. The main finding of this work is that the difference between singlet-triplet splitting of O=CHX and HM=PH 3 play an important role in determining the kinetic and thermodynamic stability of the aza-and arsa-Wittig reactions. When HM=PH 3 with more ylidic character is utilized, the reaction has a smaller activation energy and a larger exothermicity.

Geometrically Enforced Donor-Facilitated Dehydrocoupling Leading to an Isolable Arsanylidine-Phosphorane

“…Overall, structural, spectroscopic, and computational data confirm the dominance of the ylidic mesomeric structure 4 over its ylene counterpart 4 ′ (Chart ). The electronic structure of (hypothetical) arsanylidene-phosphoranes was the subject of several theoretical papers recently; the theoretical investigations were stimulated by interest in the bonding as well as potential Wittig-like reactivity …”