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).