Molbank 2004

Molbank 2004, M361

http://www.mdpi.net/molbank/

5-(3,4-Dimethoxybenzylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione

Abdullah Mohamed Asiri *, Khaled Ahmed Alamry

Chemistry Department, Faculty of Science, King Abdul-Aziz University,

Jeddah 21413, P.O.Box 9028, Saudi Arabia. Tel.(+966)-2-6952293, Fax (+966)-2-6952293, E-mail: [email protected]

Received: 13 September 2003 / Accepted: 4 February 2004 / Published: 24 February 2004

5-(3,4-Dimethoxybenzylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione 3 was prepared by Knoevenagel condensation of 3,4di-methoxybenzaldehyde 1 and N,N-diethylthiobarbituric acid 2 in ethanol using piperidine as a base [1,2].

N,N-diethylthiobarbituric acid 2 ( 6.0 g, 0.03 mol) and 3,4-dimethoxy- benzaldehyde 1 (5.0 g, 0.03 mol ) in ethanol ( 50 mL) was heated under reflux for ten minutes. Piperidine (1.5 mL) was added in one portion and the reflux was continued for further three hours. The reaction mixture was cooled to room temperature and the solid formed was filtered, washed with cooled ethanol ( 2x 50 mL) and dried. 5-(3,4-Dimethoxybenzylidene)-1,3-diethyl-2-thioxodihydropyrimidine-4,6(1H,5H)-dione 3 was recrystallized from ethanol as deep yellow crystals (9.85 g, 94%).

M.p. 169 ^оC (EtOH, uncorrected).

UV lmax (nm; EtOH)/e (dm³.mol^-1.cm^-1) 260/2009, 370/2875 and 220/ 2475.

IR nmax (cm^-1; KBr Disk) 1694 (C=O), 1670 (N-CO-N), 1632 (C=C).

¹H-NMR (400 MHz; CDCl₃; Me₄Si) dH 8.48 (1H, s, olefinic Proton), 8.35 (1H), 7.84 (1H, d, J = 8.5 Hz), 6.96 (1H, d, J= 8.5 Hz), 4.51, 4.50 ( 4H, t, 2xCH₂), 4.00, 3.98 (5H, s, 2xMeO), 1.33, 1.28 ( 6H, q, 2xCH₃).

¹³C-NMR (100 MHz; CDCl₃; Me₄Si) d C 178.8 (C=S), 161.4, 160.9 (2xC=O), 154.74, 148.16 (CH olefinic), 133.6, 131.97, 122.5, 120.8, 117.38, 109.9, 55.4, 55.02 ( 2x CH₃O), 44.1, 43.5 ( 2xCH₂), 13.0, 12.7 (2xCH₃).

Anal.Calc. for C₁₇H₂₀N₂O₄S ( 348.418): C 58.60, H 5.79 , N 8.04; found : C 58.45, H 5.89, N 7.95.

References

1. G. Jones, Org. React., 1967, 15, 204.

2. K. Tanaka, X. Chen and F. Yoneda, Tetrahedron, 1988, 44, 3241.