Molbank 2010, M666; doi:10.3390/M666 OPEN ACCESS molbank ISSN 1422-8599 www.mdpi.com/journal/molbank Short Note 5-[(3,5-Dimethyl-1-phenyl-1H-pyrazol-4-yl)methylene]-1,3diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione Abdullah Mohamed Asiri 1,2,* and Salman A. Khan 1 1 2 Chemistry Department, Faculty of Science, King Abdul Aziz University, P.O. Box 80203, Jeddah 21413, Saudi Arabia The Center of Excellence for Advanced Materials, King Abdul Aziz University, Jeddah 21589, P.O. Box 80203, Saudi Arabia * Author to whom correspondence should be addressed; E-Mail: aasiri2@kau.edu.sa; Tel.: +966 2 569701362; Fax: +966 2 6952292. Received: 1 March 2010 / Accepted: 16 March 2010 / Published: 17 March 2010 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-4carbaldehyde 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. Keywords: thiobarbituric acid; Knoevenagel condensation; pyridine 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. M666 (Page 2) Molbank 2010 N O CHO H3C CH3 N O + N 2 O H N (1) Pyridine, 3h S N H3C Ethanol (2) S N N N O CH3 (3) A mixture of 1,3-diethyl-2-thiobarbituric acid (1) (1.0 g, 0.005 mol), 3,5-dimethyl-1phenylpyrazole-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). H-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), 1 C-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. 13 Anal. calc. for C20H22O2N4S: C, 62.82, H, 5.75, N, 14.65. Found: C, 62.76, H, 5.55, N, 14.58. Acknowledgements The authors would like to thank the Chemistry Department, King Abdul Aziz University, Jeddah, Saudi Arabia for providing the research facilities. References and Notes 1. Asiri, A.M. Synthesis and characterization of dyes dicyanomethyleneindane. Dyes Pigm. 1999, 42, 209–213. exemplified by 2-arylidene- Molbank 2010 2. 3. 4. 5. 6. M666 (Page 3) Jiang, L.; Chang, Q.; Ouyang, Q.; Liu, H.; Wang, Y.; Zhang, X.; Song, Y.; Li, Y. Fabrication and nonlinear optical properties of an ultrathin film with acceptor–donor periodically overlapping structure. Chem. Phys. 2006, 324, 556–562. Wu, C.; Tretiak, S.; Chernyak, V.Y. Excited states and optical response of a donor–acceptor substituted polyene: A TD-DFT study. Chem. Phy. Lett. 2007, 433, 305–311. Chandrassekarn, Y.; Dutta, G.K.; Kanth, R.B.; Patil, S. Tetrahydroquinoxaline based squaraines: Synthesis and photophysical properties. Dyes Pigm. 2009, 83, 162–167. Liu, Y.; Zhou, J.; Zhang, X.; Liu, Z.; Wan, X.; Tian, J.; Wang, T.; Chen, Y. Synthesis, characterization and optical limiting property of covalently oligothiophene-functionalized graphene material. Carbon 2009, 47, 3113–3121. Bosch, P.; Peinado, C.; Martin, V.; Catalina, F.; Corrales, T. Fluorescence monitoring of photoinitiated polymerization reactions: Synthesis, photochemical study and behaviour as fluorescent probes of new derivatives of 4′-dimethylaminostyryldiazines. J. Photochem. Photobio. A: Chem. 2006, 180, 118–129. © 2010 by the authors; licensee Molecular Diversity Preservation International, Basel, Switzerland. This article is an open-access article distributed under the terms and conditions of the Creative Commons Attribution license (http://creativecommons.org/licenses/by/3.0/).