Glyoxal → 6-Methylquinoxaline

Reaction equation

[CH3:1][C:2]1[CH:3]=[C:4]([NH2:9])[C:5]([NH2:8])=[CH:6][CH:7]=1.[CH:10]([CH:12]=O)=O>C(O)(C)C>[CH3:1][C:2]1[CH:3]=[C:4]2[C:5](=[CH:6][CH:7]=1)[N:8]=[CH:12][CH:10]=[N:9]2

Participants

Conditions

Temperature: 80 °C

Procedure

To a solution of 4-methylbenzene-1,2-diamine (50.0 g, 0.41 mol) in isopropanol (300 mL) was added a solution of glyoxal (40% in water, 65.3 g, 0.45 mol) at room temperature. The reaction mixture was heated at 80° C. for 2 hours and evaporated under vacuum to give 6-methylquinoxaline (55 g, 93%), which was used directly in the next step. 1H NMR (300 MHz, CDCl3) δ 8.77 (dd, J=1.5, 7.2 Hz, 2H), 7.99 (d, J=8.7 Hz, 1H), 7.87 (s, 1H), 7.60 (dd, J=1.5, 8.4 Hz, 1H), 2.59 (s, 3H).