Br[C:2]1[C:7]([CH3:8])=[CH:6][N:5]=[CH:4][C:3]=1[CH3:9].C([Li])CCC.CN([CH:18]=[O:19])C>CCOCC.CCCCCC>[CH3:9][C:3]1[CH:4]=[N:5][CH:6]=[C:7]([CH3:8])[C:2]=1[CH:18]=[O:19]A solution of 4-bromo-3,5-dimethylpyridine (0.70 g, 3.76 mmol) in ether (10 mL) was cooled to −78° C. and then 2.50 M n-butyllithium in hexane (1.50 mL) was added to the reaction flask dropwise. After stirring at −78° C. for 1 h, DMF (1.75 mL, 22.6 mmol) was added to the reaction flask slowly. The reaction solution was allowed to warm to room temperature overnight. The reaction was quenched with 10 mL saturated NH4Cl solution and diluted with ethyl acetate. The aqueous layer was extracted with ethyl acetate once. The combined organic solutions were dried over Na2SO4, filtered and concentrated. The residue was purified by silica gel chromatography (40% to 50% ethyl acetate/hexanes) to afford the desired product as a solid. (280 mg, 55%). 1H NMR (400 MHz, CDCl3): δ 10.62 (s, 1 H), 8.43 (s, 2 H), 2.57 (s, 6 H).
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