3,6-Bis(3,4,5-trimethoxyphenyl)-1,2,4-triazolo[3,4-b][1,3,4]thiadiazole

In the molecule of the title compound, C21H22N4O6S, the planar central heterocyclic ring system is oriented with respect to the trimethoxyphenyl rings at dihedral angles of 2.60 (5) and 3.60 (6)°. Intramolecular C—H⋯N and C—H⋯S hydrogen bonds result in the formation of planar five- and six-membered rings. In the crystal structure, intermolecular C—H⋯O hydrogen bonds link the molecules. There is a C—H⋯π contact between a methyl group and a trimethoxyphenyl ring, and a π–π contact between the central heterocyclic ring system and a trimethoxyphenyl ring [centroid–centroid distance = 3.640 (1) Å].

In the molecule of the title compound, C 21 H 22 N 4 O 6 S, the planar central heterocyclic ring system is oriented with respect to the trimethoxyphenyl rings at dihedral angles of 2.60 (5) and 3.60 (6) . Intramolecular C-HÁ Á ÁN and C-HÁ Á ÁS hydrogen bonds result in the formation of planar five-and six-membered rings. In the crystal structure, intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules. There is a C-HÁ Á Á contact between a methyl group and a trimethoxyphenyl ring, and acontact between the central heterocyclic ring system and a trimethoxyphenyl ring [centroid-centroid distance = 3.640 (1) Å ].   Table 1 Hydrogen-bond geometry (Å , ).  et al., 2007) and anti-inflammatory activity (Mathew et al., 2007).

Related literature
We report herein the crystal structure of the title compound.
In the crystal structure, intermolecular C-H···O hydrogen bonds (Table 1) link the molecules (Fig. 2), in which they may be effective in the stabilization of the structure. A C-H···π contact (Table 1) between the trimethoxyphenyl ring and the methyl group and a π-π contact between B and D rings Cg2···Cg4 i [symmetry code: (i) 1 -x, 1 -y, -z, where Cg2 and Cg4 are centroids of the rings B (N1-N3/C10/C11) and D (C13-C18), respectively] further stabilize the structure, with centroid-centroid distance of 3.640 (1) Å.

Experimental
For the preparation of the title compound, 4-amino-5-(3,4,5-trimethoxyphenyl) -4H-1,2,4-triazole-3-thiol (0.01 M) and 3,4,5-trimethoxybenzoic acid (0.01 M) were dissolved in dry phosphorous oxychloride (10 ml). The resulted solution was further heated under reflux for 7 h. The reaction mixture was cooled to room temperature and the mixture was gradually poured onto crushed ice with stirring. Finally, powdered potassium carbonate and the required amount of solid potassium hydroxide were added until the pH of the mixture was raised to 8, to remove the excess of phosphorous oxychloride. The mixture was allowed to stand overnight and the solid was separated. It was filtered, washed with cold water, and then dried.
Crystals suitable for X-ray analysis were obtained by the recrystallization of the solid residue from a mixture of N,N-dimethyl-formamide/ethanol (1:1) by slow evaporation at room temperature.

Refinement
H atoms were positioned geometrically, with C-H = 0.93 and 0.96 Å for aromatic and methyl H, respectively, and constrained to ride on their parent atoms with U iso (H) = xU eq (C), where x = 1.5 for methyl H and x = 1.2 for aromatic H atoms.
Figures Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. as large as those based on F, and R-factors based on ALL data will be even larger.