An X-ray study of the most probable conformers of s-triazolebenzothiazinès inferred from 1H NMR spectra : The structures of 1-(4-nitrophenyl)-3-(4-chlorophenyl)-7,8-dimethoxy-10-methyl- s-triazolobenzothiazine, 1-phenyl-3-(4-chlorophenyl)-7,8-dimethoxy- 10-methyl- s-triazolobenzothiazine and 1-(4-chlorophenyl)-3-carbethoxy-7,8-dimethoxy-10-methyl- s-triazolobenzothiazine

Abstract

The structures of the title compounds have been established by X-ray crystallography from diffractometry data. Crystals of the first (2c) C 2, H 21, ClN 4O 4S · 2H 2O are triclinic, space group P1, with a = 9.292(2), b = 11.521(1), c = 12.077 A, a = 102.83(1), β = 95.59(1), γ = 86.98(1), Z = 2, D c = 1.412 g cm −3. Crystals of the second (2d) C 24H 22-CIN 3O 2S are triclinic, space group P 1 , with a = 8.688(2), b = 10.248(1), c = 13.707(1) A, α = 104.52(1), β = 94.30(1), γ = 65.88(1)°, Z = 2, D c = 1.393 g cm −3. Crystals of the third (2g) C 21H 22ClN 3O 4S are also triclinic, space group P1, with a = 7.344(2), b = 12.186(1), c = 13.440(2) A, α = 76.80(1), β = 78.67(1), γ = 70.87(1)°, Z = 2, D c = 1.356 g cm −3. The structures, determined by direct methods were refined to R = 0.083 for 3283 reflections of 2c, R = 0.034 for 2590 reflections of 2d and R = 0.044 for 2488 reflections of 2g. The refinement of 2c was limited by the presence of two positionally disordered water molecules. The ambiguities of the interpretation of 1H NMR spectra have been elucidated by these structure determinations underscoring the predominance of the cis junction between the six- and five-membered hetero kings (E/C) and the cis inverse form of the thiazine ring. It was shown, however, that the inversion of N1 is not hindered. The detailed analysis of the three molecular geometries basically substantiated the flexible B and E conformers suggested by Sohár and co-workers (Org. Magn. Reson., 22 (1984) 720).