Fluorous solvent-promoted deprotection of p -methoxybenzyl- and 2,4-dimethoxyphenylmethyl-protected alcohols with camphorsulfonic acid

Abstract

We found that a catalytic amount of camphorsulfonic acid (CSA) in CF3CH2OH (TFE) deprotected p-methoxybenzyl (PMB) groups in high yield with the addition of anisole to scavenge the liberated PMB groups. This enabled selective deprotection of PMB groups even in the presence of other protecting groups such as Bn and Ac. Furthermore, by switching the acid to pyridinium p-toluenesulfonate (PPTS) and the solvent to (CF3)2CHOH (HFIP), highly chemoselective PMB deprotection was achieved even in the presence of acid-labile silyl protecting groups. The combination of PPTS and TFE proved effective for deprotection of 2,4-dimethoxyphenylmethyl groups.