Photoredox Removal Of P-Methoxybenzyl Ether Protecting Group

Protecting group is widely applied strategy by shielding the active functionality temporally in organic synthesis. p-Methoxy benzyl is an popular protecting group for hydroxyls and amines due to its easy availability and various introducing strategy. However, the cleavage of PMB group requires stoichiometric amount of strong oxidation that is not favored regarding the atom economy and environment friendship. It is important to come up with a catalytic strategy emplolying inexpensive catalyst and environment-friendly oxidation.There are a lot of applications of photoredox reactions in organic synthesis recent years while it started at 1980s. Now we find that we can get the same results by photoredox instead of classic methods with the advantage:mild conditions, less energy. Therefore, it has great potentials and prospect in today’s energy shortage, seek new energy environment.Herein, we report a mild protocol for removal of the p-methoxybenzyl ether protecting group under acidic conditions with eosin Y combined with LEDs as a photoredox catalysis system and hydrogen peroxide as the terminal oxidant. This protocol is compatible with ethers derived from primary, secondary, and tertiary alcohols, as well as with various functional groups. The protocol showed unusual selectivity for a tertiary ether over a primary ether. The scale up to gram scale is also explored and identical reactivity is observed.