Regioselective methanesulfonylation of simple aromatics using methanesulfonic anhydride can be achieved over zeolite catalysts. For example, methanesulfonylation of toluene over various cation-exchanged zeolite beta catalysts affords higher para-selectivity in the synthesis of methyl tolyl sulfone than standard Friedel-Crafts methanesulfonylation utilising aluminium chloride.