Br[C:2]1[N:3]=[CH:4][C:5]([NH2:8])=[N:6][CH:7]=1.[CH3:9][C:10]1[CH:11]=[C:12](B(O)O)[CH:13]=[CH:14][C:15]=1[CH3:16].C(=O)([O-])[O-].[Na+].[Na+]>O1CCOCC1.CO.O.C1C=CC([P]([Pd]([P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)([P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)[P](C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)(C2C=CC=CC=2)C2C=CC=CC=2)=CC=1>[CH3:9][C:10]1[CH:11]=[C:12]([C:2]2[N:3]=[CH:4][C:5]([NH2:8])=[N:6][CH:7]=2)[CH:13]=[CH:14][C:15]=1[CH3:16]To a solution of 5-bromopyrazin-2-amine (4 g, 22.99 mmol, 1.00 equiv) in 1,4-dioxane (68 mL) and methanol (23 mL) was added 3,4-dimethylphenylboronic acid (3.52 g, 23.47 mmol, 1.02 equiv), sodium carbonate (4.872 g, 45.96 mmol, 2.00 equiv) in water (23 mL), and Pd(PPh3)4 (532 mg, 0.46 mmol, 0.02 equiv) and the resulting solution was stirred for 4.5 h at 110° C. in an oil bath. The resulting mixture was concentrated under vacuum, diluted with 200 mL of ethyl acetate, washed with 2×100 mL of brine, dried over anhydrous sodium sulfate and then concentrated under vacuum. The residue was applied onto a silica gel column with petroleum ether/ethyl acetate=10:1˜1:1, then with dichloromethane/methanol (10:1˜5:1). The collected fractions were combined and concentrated under vacuum. This resulted in 4.82 g (crude) of 5-(3,4-dimethylphenyl)pyrazin-2-amine as a yellow solid.
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