Shedding Light on the Reaction Mechanism of the Catalytic Aza‐Wittig Reaction of 2‐Methylbenzoxazole: A Bonding Evolution Theory Analysis

ABSTRACT Density functional theory (DFT) with the ωB97X‐D exchange‐correlation functional and the 6‐311G(d,p) basis set together with the Bonding Evolution Theory (BET) have been enacted to unravel the mechanism of the catalytic aza‐Wittig reaction leading to the formation of 2‐methylbenzoxazole 3 . The exploitation of the potential energy surface has shown that this reaction takes place following two main Channels, a and b , where favorable Channel a leads to the targeted product and takes place following four steps. A panoply of computational chemistry tools has been employed, leading to comprehensive and consistent results and interpretations: (i) BET analysis has highlighted the successive formation and breaking of chemical bonds leading to the synthesis of 3 and the liberation of a carbon dioxide molecule from the attack of phosphine oxide on the aryl isocyanate; (ii) moreover, BET has revealed that the synthesis of 3 takes place in four steps, with asynchronous transition states; (iii) characterized by large electron density transfers (larger than for the synthesis of the parent 2‐methylbenzothiazole, owing to the larger electronegativity of the O vs. S atoms); (iv) the relative energies of the transition state and intermediate isomers have been substantiated by carrying out a NonCovalent Interaction (NCI) analysis, pointing out the role of specific H‐bonds and π‐π interactions; and (v) the key elements of this NCI analysis have further corroborated the results of the Distortion Interaction/Activation Strain (DIAS) approach.