Synthesis of some new biologically active thiadiazolotriazinones--Part II

Molecular structure, spectroscopic (FT-IR, FT-Raman), NBO analysis of N,N'-diphenyl-6-piperidin-1-yl-[1,3,5]-triazine-2,4-diamine

In the present work, we have synthesized and reported a combined experimental and theoretical study on the molecular structure, vibrational spectra and HOMO-LUMO analysis of N,N'-diphenyl-6-piperidin-1-yl-[1,3,5]-triazine-2,4-diamine (C20N6H22). The FT-IR and FT-Raman spectra of N,N'-diphenyl-6-piperidin-1-yl-[1,3,5]-triazine-2,4-diamine were recorded. The molecular geometry, harmonic vibrational wavenumbers and bonding features of the title molecule in the ground-state have been calculated by using the density functional B3LYP method with 6-31G(d) as basis set. Non-linear optical (NLO) behavior of the N,N'-diphenyl-6-piperidin-1-yl-[1,3,5]-triazine-2,4-diamine was investigated by determining the electric dipole moment μ, polarizability α, and hyperpolarizability β using the above mentioned basis set. The molecular properties such as ionization potential, electro-negativity, chemical potential, electrophilicity have been deduced from HOMO-LUMO analysis employing the same basis set. The calculated HOMO and LUMO energies showed that charge transfer occurs within the molecule. Stability of the molecule arising from hyper conjugative interaction and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. Finally, the calculation results were applied to simulate infrared and Raman spectra of the title compound which showed good agreement with the observed spectra.

Synthesis of novel thiadiazolotriazin-4-ones and study of their mosquito-larvicidal and antibacterial properties

A series of novel 3-tert-butyl-7-(aryloxymethyl)-4H-[1,3,4]thiadiazolo[2,3-c][1,2,4]triazin-4-ones (5a-5n) were synthesized by refluxing 3,3-dimethyl-2-oxobutanoic acid (trimethyl pyruvic acid) (1) and thiocarbohydrazide (2) in ethanol as solvent for 12 h, to yield 3-mercapto-4-amino-6-tert-butyl-1,2,4-triazine-5(4H)-one (3) (Scheme 1), then the compound (3) was condensed with different substituted aryloxyacetic acids (4) in POCl3 at 90 °C for 8 h (Scheme 2). The structures of the newly synthesized compounds were confirmed by IR, (1)H NMR, (13)C NMR, elemental analyses and mass spectroscopic studies. Few of the synthesized compounds exhibited moderate mosquito-larvicidal and antibacterial activities. Among the novel derivatives, the compound (5f) showed relatively high larvicidal activity against a malaria vector. Compounds (5i) and (5m) exhibited a broad spectrum antibacterial activity against Gram positive and Gram negative species and hence they may be considered as drug candidates for bacterial pathogens.

Molecular structural, IR and NMR spectroscopic studies on the four isomers of thiotriazinone by DFT and HF calculations

One of the isomers of thiotriazinone, 6-hydroxy-2-methyl-3-thioxo-2H-1,2,4-triazin-5-one, was characterized by single-crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P2(1)/c with a=9.5837(19)Å, b=5.7006(11)Å, c=15.065(4)Å, α=90°, β=128.540(19)° and γ=90°. The molecular geometries and vibrational frequencies of the four isomers of thiotriazinone in the ground state have been calculated using the density functional theory (DFT) and Hartree-Fock (HF) methods with 6-311++G(d,p) basis set, and compared with the experimental data. Gauge-including atomic orbital (GIAO) (13)C and (1)H NMR chemical shift values were calculated by DFT/6-311++G(2d,2p) and HF/6-311++G(2d,2p) methods, and compared with the experimental data. The calculated results show that the optimized geometries can well reproduce the crystal structural parameters. The theoretical IR spectra and (13)C and (1)H NMR chemical shift values also show good agreement with experimental data. In addition, frontier molecular orbitals (FMO) and molecular electrostatic potential (MEP) analysis of the four isomers were investigated using theoretical calculations.

Synthesis of some new biologically active thiadiazolotriazinones--part III

4-Amino-6-arylmethyl/tert-butyl-3-mercapto-1,2,4-triazin-5(4H)-ones (1) were condensed with arylfuroic acids (2) to yield 7-(5-aryl-2-furyl)-3-arylmethyl/tert-butyl-4H-1,3,4-thiadiazolo[2,3-c]-1,2,4-triazin-4-ones (3). The newly synthesized compounds exhibited antibacterial activity comparable to that of nitrofurazone. In addition, two compounds displayed in vitro antitumor activity with moderate growth inhibition against a panel of 60 tumor cell lines.