Crystal structures of 2-phenyl- and 2-benzyl-5,6-dihydro-6-hydroxy-7H-1,2,4-triazolo [3,2-b] 1,3-thiazines

The examined compounds crystallize in the monoclinic space groupsP2₁/c (phenyl derivative,1) andP2₁/a (benzyl derivative,2). The unit cell parametersa, b, c (Å) and (°) were: 6.402(1), 16.506(1), 10.144(1), 97.48(1) for1 and 12.099(2), 4.612(1), 21.712(4) and 105.20(2) for2. The finalR(Rw) factors were 0.043 (0.041) and 0.121 (0.126) for1 and2, respectively. Both molecules have similar geometry of the bicyclic system with flat 1,2,4-triazole rings, sofa conformations of 1,3-thiazole ones and axial hydroxy groups. In the crystals the molecules form infinite chains (by means of O–H...N(4) hydrogen bonds), enantiomeric in1 and racemic in2.