Photodecarboxylation of chromone-2-carboxylic acid in aerated and deaerated ethanol solution

The typical photodecarboxylation of chromone-2-carboxylic acid occurs in ae rated and deaerated ethanol solutions to afford 4-hydroxycoumarin and 2-( 1 '-hydroxyethyl)-chromone, respectively. The former proceeds through an addi tion of the ground state oxy gen molecule, while the latter through the rec ombination between the ketyl radical and the 1-hydroxyethyl radical followe d by the release of CO2. Chemiluminescence technique was successfully applied to detect ketohydroper oxide intermediates assumed in the photoreaction of the aerated system. (C) 2001 Elsevier Science B.V. All rights reserved.