Mesylater

Mesylater is a term that can refer to a salt or ester of methanesulfonic acid, commonly known as mesylic acid. Methanesulfonic acid has the chemical formula CH3SO3H. When it reacts with a base, it forms a mesylate salt. For example, sodium mesylate is formed by the reaction of methanesulfonic acid with sodium hydroxide. These salts are typically crystalline solids and are often soluble in water.

Alternatively, mesylates can be esters formed when the hydroxyl group of an alcohol is replaced by the mesylate group (CH3SO2O-). In this context, the mesylate group acts as a leaving group in organic reactions, making it very useful for nucleophilic substitution and elimination reactions. This is because the mesylate anion is a resonance-stabilized species, making it a relatively stable species to depart from the molecule.

Mesylates are widely used in organic synthesis as intermediates for introducing other functional groups or for preparing alkenes. The formation of a mesylate ester is often a preferred method for activating an alcohol for subsequent reactions compared to using a halide, as the reaction conditions are generally milder and it avoids the formation of strong acidic byproducts. The preparation of mesylate esters typically involves reacting an alcohol with methanesulfonyl chloride (mesyl chloride) in the presence of a base, such as triethylamine or pyridine, to neutralize the hydrochloric acid produced during the reaction.