A clean bifurcation between two important photochemical reactions through competition of a triplet state Type II H-abstraction reaction with a photo-Favorskii rearrangement for (o/p)- hydroxy-o-methylphenacyl esters that depends on the water content of the solvent has been established. The switch from the anhydrous Type II pathway that yields indanones to the aqueous-dependent pathway producing benzofuranones occurs abruptly at low water ...
