Graphite/Methanesulfonic Acid (GMA) as a New Reagent for Sulfonylation of Phenols and Thia‐ Fries Rearrangement of Aryl Sulfonates to Sulfonylphenols

A new facile method for direct sulfonylation of phenols was developed. Graphite in methanesulfonic acid (GMA) was used to prepare sulfonylphenols by sulfonylation of phenol and naphthalene derivatives with p ‐toluenesulfonic acid (=4‐methylbenzenesulfonic acid) ( Table 1 ) and the thia‐ Fries rearrangement of aryl sulfonates ( Table 4 ). Mechanistic studies showed that the sulfonylation reaction of phenols in GMA occurred through an initial sulfonate formation followed by a thia‐ Fries rearrangement of the aryl sulfonate by an intermolecular mechanism ( Scheme 3 ).