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Paper | Regular issue | Vol 38, No. 8, 1994, pp.1775-1789
Published online, 1st January, 1970
DOI: 10.3987/COM-93-6645
Intramolecular Sulfenylation Using Sulfoxides. Preparation of 5H-Pyrrolo[1,2-a][3,1]benzothiazines

Joseph A. Picard, Shaowu Chen, and Dallas K. Bates*

*Department of Chemistry, College of Sciences and Arts, Michigan Technological University, 1400 Townsend Drive, Houghton, Michigan, 49931, U.S.A.

Abstract

N-[2-(Phenylsulfinylmethyl)phenyl]pyrrole (4) undergoes transfer sulfenylation to N-(2-chloromethylphenyl)-2-phenylthiopyrrole (5‘) presumably via S-phneyl 5H-pyrrolo[1,2-a][3,1]benzothiazonium chloride (7). Depending upon the rigor of the reaction conditions, either N-(2-hydroxymethylphenyl)-2-phenylthiopyrrole (5) or its 5-trifluoroacetyl derivative (6) are obtained when 4 is treated with TFAA in trifluoroacetic acid. N-[2-(Methylsulfinylmethyl)aryl]pyrroles (12), when treated with gaseous hydrogen chloride and the resulting sulfonium salts refluxed in dichloroethane, produce substituted 5H-pyrrolo[1,2-a][3,1]benzothiazines (14). 1-Formyl-5H-pyrrolo[1,2-a][3,1]benzothiazines (22) are formed in one step in good yield when sulfoxides (12) are reacted with the Vilsmeier-Haack reagent (DMF/POCl3). No Pummerer rearrangement product is isolated from these reactions.