Efficient Photodecarboxylation of Trifluoromethyl-substituted Phenylacetic and Mandelic Acids

A total of eight CF₃-substituted phenylacetic and mandelic acids are shown to undergo efficient photodecarboxylation (PDC; Φ = 0.37–0.74) in basic aqueous solution to give the corresponding trifluoromethyltoluenes or trifluoromethylbenzyl alcohols. The products are consistent with the almost exclusive formation of benzylic carbanions that subsequently react with water, with minor amounts (≤5%) of radical-derived products detected. Quenching studies indicate that the reaction likely proceeds from the singlet excited state. This work demonstrates that the CF₃ group greatly facilitates the excited state ionic PDC of phenylacetic acids.