Understanding the Electronic Structure and Diels–Alder Reactivity of Nitrilium-Type N -Hetarynes

-hetarynes were investigated using computational methods. To this end, the diradical character, aromaticity, and Diels-Alder reactivity of these species have been compared with those of their well-established o-benzyne analogues. By means of the activation strain model of reactivity, in combination with the energy decomposition analysis approach, it is found that a significant reduction of the Pauli repulsion between the reactants is behind the enhanced reactivity of the heterocyclic aryne. Furthermore, this study also examines how substituents directly attached to the boron atom in 1,2-azaborine-derived 1,6-BN-arynes, as well as the nature of the group-13 element adjacent to the nitrilium fragment, influence the reactivity of these novel species.