The substituent effects on the [3+2] cycloaddition of nitrile oxides generated by photooxidation of arylazides to acetonitrile

Abstract

The DFT approach in M06L/6-311 + G(d,p) approximation was used to study the transformation of unsaturated nitrile oxides (RCNO), which were generated by photooxidation of the corresponding aromatic azide, to oxadiazoles via [3 + 2]cyclization with acetonitrile. It was found that the cycloaddition activation enthalpy was within 60-93 kJ/mol, depending on the structure of the nitrile oxide. A significant mesomeric effect of the substituent and its position in the conjugated molecular system on the activation barrier of the reaction studied was identified. The relationship between the thermodynamic characteristics of [3 + 2] cycloaddition and electron density distribution in RCNO was demonstrated by a representative set of compounds including mono- and disubstituted nitrile oxides.

Keywords: DFT approximation; Nitrile oxides; Nitroso oxides; [3+2] cycloaddition.