A molecular electron density theory study of the [3 + 2] cycloaddition reaction of 1,4-diphosphorinium-3-olates with methyl acrylate and methyl methacrylate

Abstract

The [3 + 2] cycloaddition (32CA) reactions between the unsubstituted, P1 and C-methyl substituted 1,4-diphosphorinium-3-olates (DPOs) with methyl acrylate (MA) and methyl methacrylate (MMA) were studied within the molecular electron density theory using the B3LYP/6-31G(d) method in the gas phase, THF and MeCN. An analysis of the kinetic and thermodynamic parameters associated to these 32CA reactions indicates that the formation of the 6-exo cycloadducts (CAs) is preferred. The theoretical findings of the 32CA reactions of DPOs with MA and MMA were compared with those of phosphorinium-3-olate and the nitrogen analogs. These zw-type 32CA reactions have very low polar character as a consequence of the low electrophilic character of MA and MMA. The electron localization function topological analysis of the bonding changes along the most favorable reaction path associated with the unsubstituted and highly substituted 32CA reactions indicates that these reactions take place through a non-concerted two-stage one-step mechanism. These reactions may be used to examine 32CA reactions involving complex phosphorus moieties. The major outcome of these investigations is promising for the study of phosphorus containing heterocycles due to their rising applications and limited research.