An Optimized Synthesis, Molecular Structure and Characterization of Benzylic Derivatives of 1,2,4-Triazin-3,5(2H,4H)-dione.

4-Benzyl-1,2,4-triazin-3,5(2,4)-dione (3-benzyl-6-azauracil, ), and 2,4-dibenzyl-1,2,4-triazin-3,5(2,4)-dione (1,3-dibenzyl-6-azauracil, ) were synthesized by the reaction of 1,2,4-triazin-3,5(2,4)-dione (6-azauracil, ) with benzyl bromide and potassium carbonate in dry acetone via the 18-crown-6-ether catalysis. In these reaction methods, we developed more convenient and efficient methodologies to afford compounds and in good yields. These compounds were characterized by ¹H- and C-NMR, MS spectrum, IR spectroscopy and elemental analysis. The structure of was verified by 2D-NMR measurements, including gHSQC and gHMBC measurements. A single-crystal X-ray diffraction experiment indicated that compound , with the molecular formula CHN₃O₂, crystallized from a CH₃OH/CH₂Cl₂ diffusion solvent system in a monoclinic space group 2₁/ with = 13.7844(13), = 8.5691(8), = 13.0527(12) Å, = 105.961(2)°, V = 1482.3(2) ų, Z = 4, resulting in a density D of 1.314 g/cm³. The crystal structure of compound is tightly stabilized by contact with five other molecules from the six short contacts formed by intermolecular C-O···H-C, C-H···C, and weakly π···π stacking interactions. The dihedral angle 31.90° is formed by the mean planes of the benzene rings of the N-2 and N-4 benzyl groups.