Synthesis of the 6-oxidopyrido[1,2-a]quinoxalinium derivatives from quinoxalin-2-one and aldehydes – new examples of domino reactions

Quinoxalin-2-one reacts with aldehydes on heating in the presence of an acid to afford 6-oxidopyrido[1,2- a ]quinoxalinium zwitter ions which on treatment with picric acid give picrates.