Step 1: Synthesis of 2-amino-5,6-dimethylpyrazine. 2-Aminoacetamidine dihydrobromide (620 mg, 2.64 mmol) was stirred in 6 mL of methanol (MeOH) in a capped flask at -30 °C (using an acetonitrile/CO2 bath). Meanwhile, 2,3-butanedione (232 μL, 2.64 mmol) was stirred with sodium acetate (700 mg) in 6 mL of water (H2O) until homogeneous. Using a pipette, the 2,3-butanedione solution was slowly added to 2-aminoacetamidine dihydrobromide solution followed by 2.5 mL of 3.6 M sodium hydroxide (NaOH) solution. The reaction mixture was slowly warmed to room temperature and stirred overnight. Upon completion of the reaction, methanol was removed by rotary evaporation and the aqueous phase was extracted with ethyl acetate (EtOAc) three times (30 mL each). The organic phases were combined, dried with magnesium sulfate (MgSO4), filtered and concentrated to give a yellow solid containing a small amount of impurities. The solid was ground and filtered with a solvent mixture of ethyl acetate/ether (EtOAc/Et2O) to give pure 2-amino-5,6-dimethylpyrazine (55 mg, 17% yield). 1H-NMR (400 MHz, CDCl3) δ 7.76 (s, 1H), 4.25 (br s, 2H), 2.40 (s, 3H), 2.37 (s, 3H).
