Synthesis, Crystal Structures and Molecular Packing of a Series of Pyrazolo-Benzothiazine Hybrid Derivatives

Abstract

The crystal structures of four derivatives of pyrazolo[4,3-c][1,2]benzothiazine-2,4-dihydro-3,4-dimethyl-,5,5-dioxide containing benzothiazine dioxide and pyrazolo fused rings that have been synthesized were determined. (C₁₁ H₁₁ N₃ O₂ S): Mr = 249.29, monoclinic, P2₁/c, a = 8.3070(3), b = 13.6331(5), c = 10.1661(3) Å, β = 106.924(2)°, V = 1101.45(7) Å^3, Z = 4. (C₁₂ H₁₃ N₃ O₂ S): Mr = 263.31, monoclinic, P2₁/n, a = 9.729(3), b = 11.224(4), c = 11.436(3) Å, β = 98.85(2)°, V = 1233.9(7) ų, Z = 4. (C₁₄ H₁₅ N₃ O₄ S): Mr = 321.35, monoclinic, P2₁/c, a = 9.2534(3), b = 19.3920(7), c = 7.9489(2) Å, β = 95.323(2)°, V = 1420.21(8) Å^3, Z = 4. (C₁₄ H₁₅ N₃ O₃ S): Mr = 305.35, monoclinic, P2₁ /c, a = 13.816(7), b = 7.464(3), c = 14.674(8) Å, β = 109.05(3)°, V = 1430.3(12) ų, Z = 4. The heterocyclic thiazine rings adopt half-chair conformations, and the mean-planes of the phenyl and pyrazolo rings lie between 10.43(11) and 15.93(16)° with respect to each other. In each case, the geometry about thiazine N-atom is trigonal pyramidal and only the first compound containing a donor N-atom shows classical hydrogen bonds. However, non-classical H-bonding of the type C–H···O is observed in all structures.

Graphical Abstract

The synthesis, crystal structures and molecular packing of four pyrazolo[4,3-c][1,2]benzothiazine-2,4-dihydro-3,4-dimethyl-5,5-dioxide derivatives have been presented.