Reactive intermediates. Part VII. Oxidation of 3-aminobenzoxazolin-2-one; stereospecific addition of the amino-nitrene to olefins

Abstract

Benzoxazolin-2-one with hydroxylamine-O-sulphonic acid gives the N-amino-derivative which is dehydrogenated smoothly by lead tetra-acetate to the amino-nitrene. This nitrene does not fragment to benzyne, carbon dioxide, and nitrogen. It adds to olefins to give aziridines, and the addition is stereospecific even at high dilution. It also adds exclusively 1,2 to conjugated dienes to give vinylaziridines. Thus the nitrene appears to be generated in a resonance-stabilised singlet state, which is probably the ground state. With the formally similar nitrene from N-amino-oxindole, however, rearrangement to 3-cinnolinol is much faster than reaction with olefins. The n.m.r. spectra of N-benzoxazolinonyl aziridines are complex and show that inversion at the aziridine nitrogen is greatly retarded.