3-Ethyl-6-(4-fluorophenyl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazine

In the title compound, C12H11FN4S, the thiadiazine ring adopts a twist-boat conformation. The dihedral angle between the triazolothiadiazine system and the benzene ring is 10.54 (9)°. The crystal structure is characterized by C—H⋯N hydrogen bonds. The crystal packing also exhibits π–π interactions, with a centroid–centroid distance of 3.6348 (15) Å.

In the title compound, C 12 H 11 FN 4 S, the thiadiazine ring adopts a twist-boat conformation. The dihedral angle between the triazolothiadiazine system and the benzene ring is 10.54 (9) . The crystal structure is characterized by C-HÁ Á ÁN hydrogen bonds. The crystal packing also exhibitsinteractions, with a centroid-centroid distance of 3.6348 (15) Å .
The 1,2,4-triazoles nucleus has recently been incorporated into a wide variety of therapeutically interesting drugs including H1/H2 histamine receptor blockers, cholinesterase active agents, CNS stimulants, anti-anxiety agents and sedatives (Heindel et al., 1980). Further fluorinated heterocycles have been shown to possess wide variety of biocidal activities. Compounds such as fluorouracil and fluoroquinolone have been used as anticancer agents and antibiotics (Heidelberger et al., 1957;Andersson et al., 2003;Novak et al., 2006).

Experimental
A mixture of triazole (1) (0.01 mol) and p-fluorophenacyl bromide (0.01 mol) in ethanol (25 ml) was heated under reflux for 1-2 hrs. The reaction mixture was cooled to room temparature and neutralized with sodium acetate (5%). The precipitated triazolothiadiazines were collected by filtration, washed with water and recrystallized from ethanol. Yield 82%; m.p.455 K.

Refinement
All H atoms were positioned geometrically, with C-H = 0.93 Å for aromatic H, C-H = 0.97 Å for methylene H and C -H = 0.96 Å for methyl H, and refined using a riding model with U iso (H) = 1.5U eq (C) for methyl H and U iso (H) =

Figure 1
The molecular structure of the title compound. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
The packing of molecules in the title structure. Special details Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes. Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.