Mechanistic evidence of a Gabriel Colman-type rearrangement

Abstract

Rearrangement of quinolinimidoacetic acid derivatives induced by alkoxides leading to a mixture of 7-substituted 8-hydroxy-1,6-naphthyridin-5(6H)-ones and 6-substituted 5-hydroxy1,7-naphthyridin-8(7H)-ones (Gabriel Colman-type reaction) was studied. Several chemical evidences accounts for a mechanism in two steps with quinolinamic ester intermediates (Nsubstituted 3-carbamoyl-2-pyridinecarboxylic acid alkyl esters and 2-carbamoyl-3pyridinecarboxylic acid alkyl esters). These compounds were isolated from a reaction in mild conditions and their structure confirmed through an unequivocal synthesis.