Crystal structure of enantiomeric 3-amino-6,7-dihydro-6-hydroxy-5H-1,2,4-triazolo [3,4-b] 1,3-thiazine

The crystals of C₅H₈N₄OS are orthorhombic, space group P2₁2₁2₁ (Z=4),a=5.601(1),b=10.224(3), andc=12.233(2) Å. 1,2,4-Triazole ring is approximately planar while 1,3-thiazine ring adopts a C(5)-sofa conformation flattened at the N–C–S end with axial hydroxy group at the opposite side of the ring. The three intermolecular hydrogen bonds, N(3)...O(8), N(3)...N(2), and O(8)...N(1) form a three-dimensional hydrogen bonds network in the crystal. The structure is the first 5H-1,2,4-triazolo 3,4-b] 1,3-thiazine reported in the literature. It shows less aromatic character and smaller delocalization of electrons of the triazole ring than those in known analogs with 5,1-b] junction.