Photogenerated α,n-didehydrotoluenes from chlorophenylacetic acids at physiological pH.

Aromatic diradicals are recognized as promising intermediates for DNA cleavage, but their formation has thus far been limited to the Bergman and Myers–Saito cycloaromatizations. We report here the phototriggered generation of all isomers of the potential DNA-cleaving α,n-didehydrotoluene diradicals at physiological pH, accomplished by the irradiation of chlorophenylacetic acids under mild conditions. The desired diradicals were formed upon photolysis of the chosen aromatic in aqueous phosphate buffer solution (pH = 7.3), with the consecutive elimination of biologically compatible chloride ion and carbon dioxide. Theoretical simulations reveal that the efficient decarboxylation of the primarily generated phenyl cations involves a previously not known diradical structure.