Propylenediamine → 2-Methyl-5-phenylpyrazine

Participants

Reaction Steps

To a stirred solution of propylenediamine (2.94 g, 0.04 mol) in ethanol was added phenylglyoxal-monohydrate (5.00 g, 0.03 mol) at 0° C. within 30 minutes. After stirring for 1.5 hours at room temperature KOH (2.10 g, 0.04 mol) was added and the reaction mixture was refluxed for 12 hours. Then the solvent was removed under vacuum and the residue was extracted with ether. The organic phases were washed with brine and dried over MgSO4. Crude product was purified by flash chromatography on silica-gel using a mixture of hexane/ethyl acetate (7:3→3:7) as eluent. After flash chromatography the product was recrystallized from hexane. White solid. Yield: 780 mg, 15%. 1H NMR (CDCl3, 500 MHz): δH (ppm)=2.57 (s, 3H), 7.38-7.50 (m, 3H), 7.91-7.99 (m, 2H), 8.43-8.49 (m, 1H), 8.87 (d, J=1.5 Hz, 1H); 13C NMR (CDCl3, 125 MHz): δC (ppm)=21.2, 126.6, 128.9, 129.4, 136.5, 140.9, 143.8, 149.8, 151.9; (ESI): m/z=170.94 [M+H]+.

Provenance & Evidence