Reaction of N-unsubstituted imidazoles with benzonitrile oxide

Abstract

The behaviour of N-unsubstituted imidazoles 1 with benzonitrile oxide is reported. The results indicate that in solution a ring-chain tautomerism exists between the cycloadduct 3B and the Z-oxime 3A; while in the solid state only the chain form 3A was observed. Oximes of N–benzoylimidazol-2-ones 4, derived from subsequent attack of the 1,3-dipole on both tautomers, and 3,6-diphenyl-1,4,2,5-dioxadiazine 2, an unusual dimer of the benzonitrile oxide, were also isolated. A mechanism involving a zwitterionic intermediate is proposed. The structure of the oximes of N-benzoylimidazol-2-one 4 and 10, derived from benzonitrile oxide and p-toluonitrile oxide respectively, was determined by X-ray diffraction analysis.