Synthesis of mesylates and tosylates:

It is occasionally convenient to synthesize an activated alcohol that can be employed in nucleophilic substitution reactions as an alkyl halide. Mesylates and tosylates are instances of sulfonate compounds that serve this purpose. They are synthesized by treating alcohols with sulfonyl chlorides in the existence of a base like pyridine or triethylamine.

Figure: Synthesis of (a) tosylate and (b) mesylate.

The base works to 'mop up' the HCl that is formed and prevents acid-catalyzed rearrangement reactions.