Cycloadducts of nitrones with isocyanates; 1,2,4- or 1,3,4-oxadiazolidinones?

Abstract

The adducts formed between various aryl-substituted nitrones and aryl isocyanates have been shown, using 15N n.m.r. spectroscopy and X-ray crystallography, to be substituted 1,2,4-oxadiazolidinones and not the previously reported 1,3,4-oxadiazolinones.