Abstract
The title compound, 5-[(3,5-dimethyl-1-phenyl-1H-pyrazol-4-yl)methylene]-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione, has been synthesized by condensation of 1,3-diethyl-2-thiobarbituric acid and 3,5-dimethyl-1-phenylpyrazole-4- carbaldehyde in ethanol in the presence of pyridine. The structure of this new compound was confirmed by elemental analysis, IR, 1H-NMR, 13C-NMR and EI-MS spectral analysis.
The Knoevenagel condensation of aldehydes with active methylene compounds is an important and widely employed method for donor-acceptor chromophore formation in organic synthesis [1] with numerous applications in the synthesis of fine chemicals such as photoelectronics [2], photophotonics, photodynamic therapy [3], electrochemical sensing [4], optical limiting [5], Langmuir film and photoinitiated polymerization [6]. The donor acceptor chromophores are also applicable in the field of biomedicinal chemistry. Due to the wide application of donor-acceptor chromophores, the authors have undertaken the synthesis of a novel donor-acceptor chromophore.
A mixture of 1,3-diethyl-2-thiobarbituric acid (1) (1.0 g, 0.005 mol), 3,5-dimethyl-1-phenylpyrazole-4-carbaxaldehyde (2) (1.0 g, 0.005 mol) and a few drops of pyridine in anhydrous ethanol (15 mL) was refluxed at 80 °C for 3 h with continuous stirring. Progress of the reaction was monitored by TLC. After completion of the reaction, the solution was cooled. The heavy precipitate thus obtained was collected by filtration and purified by recrystallization from methanol/chloroform to give the title compound (3).
Yield: 78%; m.p. 177–178 °C.
EI-MS m/z (rel. int.%): 383 (62) [M+1]+.
IR (KBr) vmax cm-1: 2979 (C-Haromatic), 2926 (C-Haliphatic) 1694 (C=O), 1568 (C=C), 1194 (C-N), 1172 (C=S).
1H-NMR (600 MHz, CDCl3) δ: 8.56 (s, C=CH), 7.52 (d, J = 3.6 Hz, CHaromatic), 7.50 (d, J = 1.8 Hz, CHaromatic), 7.45 (dd, J = 3.0, 2.8 Hz, CHaromatic), 7.43 (dd, J =1.2, 1.8 Hz , CHaromatic), 7.24 (dd, J =1.4, 1.6 Hz, CHaromatic) 4.56 (t, J = 3.6 Hz, CH3-CH2-N), 2.37 (s, -CH3), 2.28 (s, -CH3), 1.34 (q, J = 6.0 Hz, CH3-CH2-N),
13C-NMR (600 MHz, CDCl3) δ: 178.94, 160.84, 158.29, 152.91, 150.40, 145.19, 138.46, 129.34, 128.69, 125.04, 117.63, 114.45, 43.92, 43.50, 14.63, 13.55, 12.70, 12.43.
Anal. calc. for C20H22O2N4S: C, 62.82, H, 5.75, N, 14.65. Found: C, 62.76, H, 5.55, N, 14.58.
Supplementary materials
Supplementary File 1Supplementary File 2Supplementary File 3Acknowledgements
The authors would like to thank the Chemistry Department, King Abdul Aziz University, Jeddah, Saudi Arabia for providing the research facilities.
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