Oxidative alkylamination of 2-methyl-3(2H)-cinnolinone: unexpected dealkylation of the entering alkylamino group

The oxidative alkylamination of 2-methyl-3(2H)-cinnolinone by secondary alkylamines in the presence of KMnO₄ leads to the smooth formation of the expected 4-alkylamino-2-methyl-3(2H)-cinnolinones. The analogous reaction with primary alkylamines is accompanied by the partial or complete N-dealkylation of the entering alkylamino group depending on the temperature. *Dedicated with gratitude to an outstanding heterocyclic chemist, Prof. Henk van der Plas on the occasion of his eightieth jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 602-611, April, 2009.