Reaction Steps
2.00 g (18.33 mmol) of 3,4-diaminopyridine were added to a solution of 2.82 ml of glyoxal (40 wt. % in water, ρ=1.265 g/ml, 62.48 mmol) in 30 ml of ethanol. The reaction mixture was maintained at an oil bath temperature of 70° C. for 5 hours and after cooling to room temperature the solvent was distilled off on a rotary evaporator. The crude product was purified by flash chromatography (EtOAc/isohexane, 9:1). This gave 2.35 g (17.96 mmol, 98%) of a white powder. Rf=0.27 (isohexane/EtOAc, 1:9). 1H NMR (200 MHz, CDCl3): δ=7.94 (dd, 3J=5.8 Hz, 4J=0.6 Hz, 1H, H-7), 8.83 (d, 3J=5.8 Hz, 1H, H-8), 8.96 (d, 3J=1.6 Hz, 1H, H-3), 9.02 (d, 3J=1.6 Hz, 1H, H-2), 9.56 (d, 4J=0.6 Hz, 1H, H-5) ppm. 13C NMR (100 MHz, CDCl3): δ=121.6 (CH, C-7), 138.0 (Cq), 145.3 (Cq), 147.3 (C—H, C-8), 146.5 (C—H, C-3), 149.2 (CH, C-2), 154.8 (C—H, C-5) ppm. GC-MS (EI): RT 5.45 min, m/e (%): 132 (8), 131 (M+, 100), 104 (25), 77 (13), 50 (10) IR (KBr): ν=3435 (vs), 3092 (w), 3023 (m), 1969 (w), 1758 (w), 1631 (w), 1598 (vs), 1562 (m), 1536 (w), 1488 (s), 1436 (vs), 1416 (m), 1381 (m), 1351 (w), 1290 (w), 1279 (m), 1212 (m), 1201 (m), 1148 (w), 1033 (s), 1014 (s), 972 (w), 959 (vs), 931 (m), 881 (vs), 838 (m), 824 (s), 773 (w), 651 (s), 623 (m), 546 (w), 524 (w), 457 (s) cm1.
