General procedure for the synthesis of 2-acetyl-5-methylpyridine from 2-bromo-5-methylpyridine and N,N-dimethylacetamide: [Reference Example 35] 5-(5-methyl-2-pyridinyl)-1-(2-pyridinyl)-1H-pyrazole-3-carboxylic acid; [show image] 1) 1-(5-methyl-2-pyridinyl)ethanone; At -78 °C, over 5 min n-butyllithium (1.58 M hexane solution, 24 ml) was added dropwise to a solution of diethyl ether (100 ml) of 2-bromo-5-methylpyridine (5.0 g) and the mixture was stirred for 5 min. Maintaining the same temperature, N,N-dimethylacetamide (3.5 ml) was added to the reaction solution and stirring was continued for 2 hours. After completion of the reaction, water and ethyl acetate were added to the reaction solution and the organic and aqueous phases were separated. The organic layer was dried with anhydrous magnesium sulfate, filtered and concentrated under reduced pressure to remove the solvent. The residue was purified by silica gel column chromatography (eluent: hexane-ethyl acetate) to afford 1-(5-methyl-2-pyridinyl)ethanone (3.43 g, 87% yield) as an oily product.1H-NMR (400 MHz, CDCl3) δ: 2.42 (3H, s), 2.71 (3H, s), 7.62 (1H, dd, J = 1.59, 7.93 Hz), 7.94 (1H, d, J = 7.93 Hz), 8.50 (1H, s).
