1-[3-(Diethylamino)phenyl]ethyl (DEAPE): A Photolabile Protecting Group for Hydroxyl and Carboxyl Groups

Herein we demonstrate that the photolabile protecting group (PPG), the 1-[3-(diethylamino)-phenyl]ethyl (DEAPE) group, has dramatically different photochemical properties from the parent 3-(diethylamino)benzyl (DEABn) PPG. The new PPG, derived from DEABn by adding a methyl group to the benzylic carbon, has similar reactivity as DEABn in releasing alcohol in MeCN/water; however, it is more efficient than DEABn in releasing carboxylic acid. In particular, it can release carboxylic acid efficiently in aprotic solvents and the PPG itself converts to 3-diethylaminostyrene. Photochemical removal of DEAPE can also be conveniently carried out with sunlight. The results in this work suggest that there probably exist multiple reaction pathways in cleaving the benzylic C–O bond and they can be affected by the benzylic substitution and the reaction conditions.