The oxidation of thiols in the presence of pyrroles

Abstract

The oxidation of aliphatic, aromatic, and heterocyclic thiols in the presence of pyrroles with iodine-potassium iodide gives pyrrolyl alkyl, aryl, or heteroaryl sulphides in addition to the expected disulphides. A mechanism is proposed which involves the initial reaction of iodine and the thiol to give a sulphenyl iodide species, followed by electrophilic attack of this species on the pyrrole nucleus. Several of the sulphides were oxidized by hydrogen peroxide in acetic acid to the corresponding sulphones. Suitably substituted pyrrolyl aryl sulphides were cyclized to several new fused heterocyclic ring systems.