Rapid and Mild Cleavage of Aryl‐Alkyl Ethers to Liberate Phenols

We report that the Piers‐Rubinsztajn reaction enables rapid deprotection of aryl alkyl ethers under ambient conditions. This chemistry leverages tris(pentafluorophenyl)borane and silyl hydrides to convert aryl methyl ethers to siloxanes, which can then be cleaved using 1 % HCl in EtOH. We examined 26 derivatives and routinely obtained yields >85 %, even in the presence of sterically demanding groups and complex substrate structures. Other alkyl ethers including ethyl, propyl, isopropyl, tert‐butyl, and benzyl groups were also easily removed. Mild, rapid, and efficient demethylation of aryl alkyl ethers is accomplished using tris(pentafluorophenyl)borane via the Piers‐Rubinsztajn reaction. This two‐step deprotection allows alkyl ethers to be used as effective phenol protecting groups without the need for harsh deprotection conditions.