Synthesis and crystal structures of two racemic 2-heteroaryl-3-phenyl-2,3-di-hydro-4-pyrido[3,2-][1,3]thia-zin-4-ones.

3-Phenyl-2-(thio-phen-3-yl)-2,3-di-hydro-4-pyrido[3,2-][1,3]thia-zin-4-one (CHNOS, ) and 2-(1-indol-3-yl)-3-phenyl-2,3-di-hydro-4-pyrido[3,2-][1,3]thia-zin-4-one 0.438-hydrate (CHNOS·0.438HO, ) crystallize in space groups 2/ and 2/, respectively. The asymmetric unit in each case is comprised of two parent mol-ecules, albeit of mixed chirality in the case of and of similar chirality in with the enanti-omers occupying the neighboring asymmetric units. Structure also has water mol-ecules (partial occupancies) that form continuous channels along the axis direction. The thia-zine rings in both structures exhibit an envelope conformation. Inter-molecular inter-actions in are defined only by C-H⋯O and C-H⋯N hydrogen bonds between crystallographically independent mol-ecules. In , hydrogen bonds of the type N-H⋯O between independent mol-ecules and C-H⋯N(π) type, and π-π stacking inter-actions between the pyridine rings of symmetry-related mol-ecules are observed.