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Short Paper | Regular issue | Vol 85, No. 9, 2012, pp.2281-2290
Published online, 25th July, 2012
DOI: 10.3987/COM-12-12528
The Structures of 8- and 10-Trifluoromethylquino[3,2-b]benzo[1,4]thiazines and Their Benzyl Derivatives

Małgorzata Jeleń, Kinga Suwińska, Céline Besnard, Krystian Pluta,* and Beata Morak-Młodawska

*Department of Organic Chemistry, The Medical University of Silesia, Jagielloñska Str. 4, 41-200 Sosnowiec, Poland

Abstract

The modification of the phenothiazine structure via the substitution of the benzene ring with the quinoline ring may proceed through the Ullmann cyclization or the Smiles rearrangement of the appropriate sulfides followed by cyclization. Reactions of 2,2’-dichloro-3,3’-diquinolinyl disulfide or pentacyclic diquinodithiin with m-trifluoromethylaniline led to two isomeric tetracyclic trifluoromethylquinobenzothiazines. The product structures as the appropriate 6H-X-trifluoromethylquino[3,2-b]benzo[1,4]thiazines (X = 8, 10) were finally confirmed by X-ray analysis (one product was transformed into N-benzyl derivative). These results exclude the possibility of the reverse Smiles rearrangement and the existence of 5H-tautomers in these conditions. Although both compounds have the same quinobenzothiazine system, they differ in the spatial structures and geometric data. Molecule 6b is unexpectedly almost planar that is the result of larger than usual the C–S–C and C–N–C angles in the thiazine ring. Molecule 14 is folded along the S–N axis with the thiazine ring in boat conformation and the benzyl group in equatorial position.