Issue in Honor of Prof. Ernst Anders ARKIVOC 2007 (iii) 60-67
(triplet), q (quartet), quin (quintet), se (sextet), m (multiplet) and b (broad). High resolution solid state 13C NMR spectra were recorded at 100 MHz on a Bruker Avance 400 digital spectrometer using cross polarization (CP) and standard Bruker magic-angle spinning (MAS) probes with zirkonia rotors (4 mm and 7 mm external diameters). Different MAS frequencies (5–12 kHz) were used. Chemical shifts were given relative to Si(CH3)4, established using adamantane as an external reference.
General Procedures. Syntheses of barbituric acid and 5-amino-barbituric acid derivatives are described in the literature.[11-14] However, no NMR data have been reported for 1-butyl barbituric acid and 1-butyl-5-aminobarbituric acid 1b.
Synthesis of the Schiff bases. The 5-aminobarbituric acid derivative (2.92 mmol) is dissolved in 100 ml dried ethanol and added to a solution of the aldehyde compound (2.92 mmol) in 50 ml dried ethanol. The mixture is refluxed for 4h. Then, the reaction vessel is stored overnight and the coloured precipitate is filtered off, washed with ethanol and dried.
Compound Characterization
1-Butylbarbituric acid. White solid; m.p.: 109–110 °C; 1H NMR (300 MHz, CDCl3): d 0.91 (t, 3J4’3’ = 7.3 Hz, 3H, CH3), 1.32 (se, 2H, CH2), 1.54 (quin, 2H, CH2), 3.63 (s, 2H, 5), 3.82 (t, 3J1’2’ = 7.3 Hz, 2H, N-CH2), 9.39 (s, 1H, 3): 13C NMR (75 MHz, CDCl3): d 13.59 (CH3), 19.90 (CH2),
29.84 (CH2), 39.19 (N-CH2), 41.12 (5), 150.79 (2), 165.31 (4/6), 165.38 (4/6). 5-Aminobarbituric acid (1). White solid; yield: 82%; m.p.: decomp. > 300 °C; IR (cm-1): 3084 (m), 1725 (m), 1710 (m), 1582 (s), 1544 (s), 1536 (s), 1501 (m), 1413 (s); 13C{1H} CP MAS NMR (4 mm, 12 kHz): d 86.78 (5), 153.92 (2), 162.78 (4, 6); anal. calculated for C4H5N3O3 (found): C 33.57 (33.67), H 3.52 (3.42), N 29.37 (29.32). ISSN 1424-6376 Page 65 ©ARKAT-USA, Inc.
