Lewis Acid Promoted Deprotection of Benzylidene Acetals and p -Methoxybenzyl Ethers with Mercaptoacid Acid as Scavenger.

We demonstrate a new and high-yielding method for removal of benzylidene acetals and para -methoxybenzyl ethers under catalytic conditions (BF 3 :OEt 2 orFeCl 3 , 10 mol%) with mercaptoacetic acid as a scavenger. The reaction coproducts are converted to water-soluble molecules, which can be removed by aqueous extraction, thereby bypassing the need for chromatographic purification. The reaction was demonstrated on both multimilligram and multigram scale.