Water-solvent method for tosylation and mesylation of primary alcohols promoted by KOH and catalytic amines

We have developed an efficient water-solvent method for p-toluenesulfonylation (tosylation) and methanesulfonylation (mesylation) of primary alcohols using p-toluenesulfonyl chloride and methanesulfonyl chloride, respectively, promoted by KOH and catalytic amines. The reaction was performed by maintaining the pH at around 10 using a pH controller to prevent the undesirable decomposition of sulfonyl chlorides. Several primary alcohols were smoothly sulfonylated in excellent yield. The choice of the amine catalyst (0.1 equiv.) was important: N,N-dimethylbenzylamine, a sterically unhindered and lipophilic tertiary amine, was effective for the tosylation, whereas N,N-dimethylbutylamine and triethylamine were effective for the mesylation. The present Schotten–Baumann-type method is the first example of catalytic sulfonylation using sulfonyl chlorides, and is a green chemical process due to the use of water as the solvent.