Water → N-(5-Methylpyridin-2-yl)pivalamide

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Reaction Steps

25.5 g of 6-amino-3 picoline was dissolved in 100 mλ of acetonitrile. 30.5 g of pivalic chloride was dropwise added to the solution at room temperature. After completion of the dropwise addition, the mixture was heated under reflux for 30 minutes and then cooled. It was poured into 100 mλ of water and the pH value thereof was adjusted to 8 with the addition of sodium carbonate. After extraction with chloroform, the solvent was distilled off under a reduced pressure to give 44.7 g of crystalline 6-pivaloylamino 3-picoline. This compound was suspended in 500 mλ of chloroform and then 44 g of m-chloroperbenzoic acid was added in portions thereto. After completion of the addition, the mixture was stirred for 2 hours and then allowed to stand overnight. It was concentrated under a reduced pressure and then dissolved in ethyl acetate. The solution was washed with an aqueous sodium carbonate solution. The solvent was distilled off under a reduced pressure to obtain 44.5 g of solid 6-pivaloylamino-3-picoline oxide. It was dissolved in 200 mλ of chloroform. 54 mλ of acetic anhydride was added to the solution. 43 g of bromine diluted with 100 mλ of chloroform was dropwise added thereto under cooling with ice. After completion of the addition, the mixture was allowed to stand at room temperature for 30 minutes. 23 g of sodium acetate was added thereto and the mixture was heated under reflux for 3 hours. A small amount of water was added thereto. After neutralization with sodium carbonate, the chloroform phase was recovered and concentrated under a reduced pressure. The residue was taken by silica gel column chromatography (solvent: 5% methanol, chloroform) to obtain 28 g of 5 bromo-6-pivaloylamino-3-picoline oxide. It was dissolved in 80 mλ of methanol. 0.15 mole of sodium methoxide was added to the solution and the mixture was heated under reflux for 40 hours. After cooling followed by neutralization with oxalic acid and concentration, the product was dissolved in chloroform and insoluble matters were removed by filtration. The solvent was distilled off under a reduced pressure to obtain 26 g of 5-methoxy-6-pivaloylamino-3-picoline oxide. This product was added to 200 mλ of methanol and 50 mλ of 6N hydrochloric acid and the mixture was heated under reflux for 52 hours. After neutralization of the hydrochloric acid followed by extraction with chloroform, the solvent was distilled off under reduced Pressure. 200 mλ of acetonitrile was added thereto and 33.8 g of 2-(2', 4'-di-t-amylphenoxy)butyric chloride was dropwise added thereto under reflux with heating. The mixture was cooled and the resulting crystals were collected by filtration to obtain 35.4 g of 5-methoxy-6-(2-(2', 4'-di-t-amylphenoxy)butyroylamino) -3 picoline oxide. It was dissolved in 500 mλ of chloroform. 55 g of phosphorus trichloride was added to the solution at room temperature. The mixture was heated under reflux for one hour. After cooling, the mixture was poured into 500 g of ice. pH of the mixture was adjusted to 10 with the addition of aqueous ammonia. After extraction with ethyl acetate, the solvent was distilled off under a reduced pressure to give 31.8 g of 5-methoxy-6-(2-(2', 4'-di-t-amylphenoxy) butyroylamino)-3-picoline. It was dissolved in 200 mλ of chloroform. 22.5 g of boron tribromide was dropwise added thereto under cooling with ice. Then the temperature was slowly elevated to room temperature and the stirring was continued at room temperature for 2 hours. The reaction mixture was poured into ice/water and then neutralized with sodium carbonate. After extraction with chloroform, the solvent was distilled off under a reduced pressure. The residue was taken by silica gel column chromatography (solvent: chloroform). After recrystallization from ethyl acetate/acetonitrile, 22.6 g of Coupler (5) was obtained. m.p.: 91°-95° C.

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