[NH2:1][C:2]1[N:7]=[C:6]([CH3:8])[C:5]([Br:9])=[C:4]([CH3:10])[N:3]=1.[CH3:11][C:12](=O)[CH2:13][CH2:14][C:15](=O)[CH3:16].C1(C)C=CC(S(O)(=O)=O)=CC=1.O>C1(C)C=CC=CC=1>[Br:9][C:5]1[C:4]([CH3:10])=[N:3][C:2]([N:1]2[C:15]([CH3:16])=[CH:14][CH:13]=[C:12]2[CH3:11])=[N:7][C:6]=1[CH3:8]To a stirred solution containing 2.00 g (9.89 mmol) of 2-amino-5-bromo-4,6-dimethylpyrimidine in 16 mL of anhydrous toluene was added 1.36 mL (11.5 mmol) of 2,5-hexanedione followed by 96 mg (0.50 mmol) of p-toluenesulfonic acid. The reaction mixture was heated and stirred at reflux for 12 h. The reaction mixture was poured into 150 mL of water and then extracted with 200 mL of ethyl acetate. The organic solution was washed with 150 mL of brine, dried (MgSO4) and concentrated under diminished pressure. The residue was purified by chromatography on a silica gel column (15×5 cm). Elution with 5:1 hexanes-ethyl acetate afforded the expected product as light yellow crystals: yield 2.23 g (81%); mp 64-65° C.; silica gel TLC Rf 0.65 (6:1 hexanes-ethyl acetate); 1H NMR (CDCl3) δ 2.34 (s, 6H), 2.67 (s, 6H) and 5.89 (s, 2H); 13C NMR (CDCl3) δ 14.5, 14.5, 24.9, 24.9, 108.7, 108.7, 118.6, 129.5, 129.5, 155.3, 155.3 and 166.9; mass spectrum (APCI), m/z 280.0458 (M+H)+ (C12H15N3Br requires 280.0449).
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