Photolytic release of carboxylic acids using linked donor-acceptor molecules: direct versus mediated photoinduced electron transfer to N-alkyl-4-picolinium esters.

[reaction: see text] Efficient photorelease (Phi = 0.7) of carboxylic acids is achieved with a covalently linked mediator (benzophenone) protecting group (N-alkyl-4-picolinium ester) molecule. The mechanism involves initial photoreduction of the mediator, followed by rapid electron transfer to the protecting group.