Behaviour of nitrile oxides towards nucleophiles. Part I. Pyridine-catalysed dimerisation of aromatic nitrile oxides

Abstract

When treated with pyridine in ethanol, non-hindered aromatic nitrile oxides dimerise to 3,6-diaryl-1,4,2,5-dioxadiazines, whose structures have been proved by the results of catalytic hydrogenation. The dimerisation of 2,4-dichlorobenzonitrile oxide has been shown to be second-order in the nitrile oxide and first-order in the nucleophile. A reaction scheme is suggested in which an intermediate adduct between nitrile oxide and pyridine reacts with more nitrile oxide to give the dimer.