Citric Acid → 2,3-Bis(methoxycarbonyl)-6,7-dimethoxy-1-[2-(4-oxo-1,2,3,4-tetrahydroquinolin-1-yl)-4-pyridyl]naphthalene

Participants

Reaction Conditions

Reaction Steps

The internal pressure of a reaction vessel was reduced (−0.09 MPa or less) and thereto was charged nitrogen gas and added toluene (120 mL) at room temperature and then added tripotassium phosphate (41.51 g) under stirring. After cooling the mixture (internal temperature: 20° C. or lower), thereto was added sodium sulfate decahydrate (13.425 g) at the same temperature. To the mixture were added 1-(2-bromo-4-pyridyl)-2,3-bis(methoxycarbonyl)-6,7-dimethoxynaphthalene (30.0 g), 4-oxo-1,2,3,4-tetrahydroquinoline (10.07 g), palladium acetate (219 mg) and Xantphos (849 mg), and the inside of the vessel was washed with toluene (15 mL). The internal pressure of the vessel was reduced (−0.09 MPa) and maintained for 5 minutes, and then nitrogen gas was charged thereto to restore the internal pressure (the procedure was carried out three times). The mixture was warmed to 45° C. to 65° C. under nitrogen stream and stirred at the same temperature for 15 hours. In the course of reaction, the internal temperature was maintained at about 47° C. over the initial 10 hours and, after that, maintained at about 57° C. After cooling the reaction mixture (internal temperature: 40° C.), thereto was added dropwise an aqueous citric acid solution (25.04 g of citric acid in 120 mL of water) at the same temperature, and thereto was added dropwise chloroform (150 mL). After warming the mixture at 45±5° C. (internal temperature), the mixture was filtered through Celite at 20° C. or more. The organic layer was separated from the filtrate and to the filtrate was added water (90 mL) at 20° C. or more and the mixture was stirred nearly for 10 minutes. The organic layer was separated and concentrated in vacuo at 60° C. or lower and to the residue was added toluene (90 mL) and the mixture was concentrated in vacuo at 60° C. or lower. The residue was allowed to stand at 20±5° C. or lower (internal temperature) nearly for one hour and the precipitated crystals were collected by filtration. The crystals were washed with a cold methanol (5±5° C., 60 mL) to obtain a toluene monosolvate of the captioned compound [c-11] as crystals. To the crystals was added a mixture of chloroform (60 mL) and methanol (6 mL) at 30±5° C. and the mixture was stirred nearly for 15 minutes. Thereto was added dropwise methanol (54 mL) at 15±5° C. over a period of one hour and the mixture was stirred at the same temperature for one hour. Subsequently, to the mixture was added methanol (39 mL) and the mixture was cooled to 5±5° C. and stirred at the same temperature for one hour. The precipitated crystals (a chloroform monosolvate of the captioned compound [c-11]) were collected by filtration, washed with a cold methanol (5±5° C., 90 mL) and dried in vacuo at 60° C. or lower to obtain the captioned compound (free form, 34.3 g) as pale yellow crystals (yield: 86%).

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