Oxidative Cyclizations. VIII. Mechanisms of Oxidation of ortho-Substituted Benzenamines and Improved Cyclizations by Bis(acetato-O)Phenyliodine

Abstract

Published reports describe the oxidative cyclization of suitable ortho-substituted arenamines to form such products as 2,1-benzisoxazoles, benzofurazan 1-oxides and benzotriazoles, by using bis(acetato-O)phenyliodine at room temperature. However, the reactions are often inconveniently slow. We now report attempts to achieve short reaction times with more powerful iodine(III) oxidants. These often failed to give cyclic products, but the results enable us to argue that the reaction competing with cyclization involves the arenaminyl, cation ArN⁺H. When such cations are predicted to be relatively unstable, the parent arenamine can be rapidly cyclized in high yield by oxidation with bis(acetato-O)phenyliodine in boiling benzene.