The N-ethylbenzisoxazolium cation-II

The N-ethylbenzisoxazolium cation has been shown to undergo a ready general base-catalyzed internal elimination to form a transitory N-ethylbenzoketoketenimine. Alternative pathways involving benzoisoxazolines have been excluded by kinetic evidence and by study of the model substance, 2-ethylbenzo-4-isoxazoline. A competition study has shown that the intermediate benzoketoketenimine exhibits high selectivity in many of its combination reactions, and that for aqueous acetic acid in the pH range of 2-5 the reactive nucleophiles are most probably water and acetate ion.