Methanesulfonyl chloride is a precursor to many compounds because it is highly reactive. It is an electrophile, functioning as a source of the "CH3SO2+"
synthon. In contrast to the formation of toluenesulfonates from alcohols and
p-toluenesulfonyl chloride in the presence of pyridine, the formation of methanesulfonates is believed to proceed via a mechanism wherein methanesulfonyl chloride first undergoes an
E1cB elimination to generate the highly reactive parent
sulfene (), followed by attack by the alcohol and rapid proton transfer to generate the observed product. This mechanistic proposal is supported by isotope labeling experiments and the trapping of the transient sulfene as cycloadducts. Methanesulfonates are used as intermediates in
substitution reactions,
elimination reactions,
reductions, and
rearrangement reactions. When treated with a
Lewis acid,
oxime methanesulfonates undergo facile
Beckmann rearrangement. Methanesulfonates are occasionally used as a
protecting group for alcohols. They are stable to acidic conditions and is cleaved back to the alcohol using
sodium amalgam.
Methanesulfonamides Methanesulfonyl chloride react with primary and secondary
amines to give
methanesulfonamides. Unlike methanesulfonates, methanesulfonamides are very resistant toward hydrolysis under both acidic and basic conditions.
Addition to alkynes In the presence of
copper(II) chloride, methanesulfonyl chloride will add across alkynes to form β-chloro
sulfones.
Formation of heterocycles Upon treatment with a base, such as
triethylamine, methanesulfonyl chloride will undergo an
elimination to form
sulfene. Sulfene can undergo
cycloadditions to form various heterocycles. α-Hydroxyketones react with sulfene to form five-membered
sultones.
Miscellaneous Forming
acyliminium ions from α-hydroxy
amides can be done using methanesulfonyl chloride and a base, typically
triethylamine. ==Safety==