Dimethylformamide → 6-cyclopentyloxy-4-formyl-7-methoxy-1-(3-methoxy-benzyl)-1H-isoquinoline-2-carboxylic acid ethyl ester

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Reaction Steps

To anhydrous N,N-dimethylformamide (0.151 mL, 1.95 mmol) at 0° C. was added phosphorus oxychloride (0.079 mL, 0.85 mmol) dropwise. The mixture was warmed to room temperature and stirred for 30 minutes. The mixture was cooled in an ice-bath, 6-cyclopentyloxy-7-methoxy-1-(3-methoxy-benzyl)-1H-isoquinoline-2-carboxylic acid ethyl ester (350 mg, 0.78 mmol) in dichloromethane (2 mL) was added dropwise. After addition was complete, the mixture was heated on an oil bath for 4 hrs at 80° C. The mixture was cooled to 0° C. and a solution of potassium acetate (228 mg, 2.32 mmol) in water (2 mL) was added slowly. The mixture was then heated at 80° C. for 20 minutes. The mixture was cooled, poured into water and diluted with dichloromethane (60 mL). The organic layer was washed water (2×20 mL), saturated aqueous sodium bicarbonate solution (20 mL), saturated aqueous sodium chloride solution (20 mL), dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo to afford 6-cyclopentyloxy-4-formyl-7-methoxy-1-(3-methoxy-benzyl)-1H-isoquinoline-2-carboxylic acid ethyl ester (386 mg, 99% yield) as a yellow oil. The crude product was used without further purification.

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