Reactivity and substituent effects in the cyclization of N-aryl-2-nitrosoanilines to phenazines

Reactivity of variously substituted N-aryl-2-nitrosoanilines in the reaction of cyclization leading to phenazine derivatives, carried out in the presence of N,O-bis(trimethylsilyl)acetamide (BSA), was estimated on the base of the observed reaction times. A strong opposite effect of substituents located at position para to the nitroso group and those located para to the amino group in the side ring was observed. Mechanistic explanation, based on the electronic properties of the substituents and their mesomeric effects, was presented. The usefulness of the obtained data for the designed syntheses of phenazines was exposed. (C) 2017 Elsevier Ltd. All rights reserved.