2-Hydroxyphenacyl ester: a new photoremovable protecting groupDedicated to Professor Jakob Wirz on the occasion of his 70th birthday.Electronic supplementary information (ESI) available: Materials and methods, synthetic procedures, LFP data, Quantum chemical calculations, NMR and UV spectra of the compounds. See DOI: 10.1039/c2pp25133g

A 2-hydroxyphenacyl moiety absorbing below 370 nm is proposed as a new photoremovable protecting group for carboxylates and sulfonates. Laser flash photolysis and steady-state sensitization studies show that the leaving group is released from a short-lived triplet state. In addition, DFT-based quantum chemical calculations were performed to determine the key reaction steps. We found that triplet excited state intramolecular proton transfer represents a major deactivation channel. Minor productive pathways involving the triplet anion and quinoid triplet enol intermediates have also been identified. A 2-hydroxyphenacyl moiety absorbing below 370 nm is proposed as a new photoremovable protecting group for carboxylates and sulfonates.