Synthesis and crystal structures of two racemic 2-heteroaryl-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-ones

Abstract

3-Phenyl-2-(thiophen-3-yl)-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-one (C17H12N2OS2, 1) and 2-(1H-indol-3-yl)-3-phenyl-2,3-dihydro-4H-pyrido[3,2-e][1,3]thiazin-4-one 0.438-hydrate (C21H15N3OS·0.438H2O, 2) crystallize in space groups P21/n and C2/c, respectively. The asymmetric unit in each case is comprised of two parent molecules, albeit of mixed chirality in the case of 1 and of similar chirality in 2 with the enantiomers occupying the neighboring asymmetric units. Structure 2 also has water molecules (partial occupancies) that form continuous channels along the b -axis direction. The thiazine rings in both structures exhibit an envelope conformation. Intermolecular interactions in 1 are defined only by C—H...O and C—H...N hydrogen bonds between crystallographically independent molecules. In 2, hydrogen bonds of the type N—H...O between independent molecules and C—H...N(π) type, and π–π stacking interactions between the pyridine rings of symmetry-related molecules are observed.