Reactions of Benzyl Aryl Sulfides with Excess Active Halogen Reagents

1,2,3-Tribromopyrrolo[1,2-b][1,2]benzothiazin-10-one (2) is produced from 2-[2-(benzylthio)benzoyl]pyrrole (1) when treated with excess (5 equiv) NBS in CHCl3. With NCS, a mixture is obtained in which di- and trichloropyrrolo[1,2-b][1,2]benzothiazin-10-ones are present. If ethanol is present in the NCS reaction, compound 4 is formed as the major product. Further, compound 3 is also formed by the reaction of compound 1 or the corresponding disulfide with excess SOCl2. A novel route to alkyl arenesulfinic esters is also reported. Treatment of a benzyl aryl sulfide with excess (5 equiv) NCS in the presence of an n-alkyl alcohol (7 equiv) produces an n-alkyl arenesulfinic ester in good yield. An arenesulfonyl chloride is the major product in the presence of benzyl alcohol.