Understanding the Diels-Alder Reactivity of Superelectrophilic Nitrobenzofuroxans and Related 10Π-Heteroaromatics through DFT-Based Electrophilicity Descriptors

A close relationship between the superelectrophilic reactivity of a large set of nitrobenzofuroxans and related 10 Pi-heteroaromatics (nitrobenzofurazans, nitrobenzotriazoles, nitrotetrazolopyridines..) and the high propensity of these compounds to contribute to a variety of Diels-Alder processes has been experimentally established. This relationship suggests that most of the corresponding cycloadditions must be strongly polar processes. In this paper, it is shown that this important mechanistic outcome is fully supported by an analysis of the reactions on the basis of the reactivity descriptors defined by Parr within the DFT theory, namely the global electrophilicity parameter omega (and the related Delta Nmax parameter) and the local electrophilicity parameter (omega(k)).