Cyclopropyl- and Allyl-substituted Arenes in Reaction with Dinitrogen Tetroxide. Effect of Substrate Oxidation Potential on Reaction Direction

Abstract

A correlation was found between oxidation potentials of acylcyclopropanes in solution (in CH2Cl2 and CH3CN) and their HOMO energies calculated by semiempirical (AM1) and nonempirical (HF/6-31G and HF/6-31G**) methods. The correlation provides a possibility to forecast the reaction direction of the mentioned substrates and N2O4. The correlation possesses a general character. It was established for instance that arylcyclo-propanes, cyclopropylmethyl- and allylbenzenes oxidized at more positive potentials than reduction potential of NO+ and having more positive eHOMOthan 9.0 eV (AM1), 8.4 eV (HF/6-31G), and 8.3 eV (HF/6-31 G**) reacted with N2O4 following the mechanism "electron transfer radical pair recombination" affording nitroaromatic derivatives retaining the cyclopropane (or allyl) fragments. Substrates of the same type where the electron transfer to NO+ should be endothermic process and whose HOMO values are less than the above critical numbers react with N2O4 by the mechanism of electrophilic cyclopropane ring opening (with aryl and benzylcyclopropanes) or by electrophilic addition across the double C=C bond (with allylbenzenes).