6-Isoquinolinecarboxylic acid

Preparation Example G-1. Isoquinoline-6-carboxylic acid A solution prepared by adding (4-bromobenzylydene)-(2, 2-diethoxyethyl) amine (synthesized from 4-bromobenzaldehyde, according to the method described in J. Org. Chem., vol. 48, 3344-3346 (1983)) (51.4g, 0.189mmol) to an ice-cold concentrated sulfuric acid (20g) was added to a solution prepared by adding diphosphorus pentoxide (40g) to an ice-cold concentrated sulfuric acid (360g), and the solution was stirred at 160°C for 2 hours. The reaction solution was gradually cooled to 0°C, the solution was filtered through Celite pad, the filtrate was neutralized with sodium carbonate. This solution was further filtrated through Celite pad, this filtrate was extracted with ethyl acetate and dried over anhydrous magnesium sulfate. The solvent was evaporated, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate), and 6-bromoisoquinoline (482mg, 1.2percent) was obtained as an orange oil. Next, to a solution of 6-bromoisoquinoline (382mg, 1.84mmol) in N, N-dimethylformamide (3.8mL) were added zinc cyanide (431 mg, 3.67mmol) and tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) under nitrogen atmosphere, and the mixture was stirred at 100°C for 1 hour. Tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) was further added, and the mixture was stirred for 2.5 hours at 100°C. The reaction mixture was allowed to room temperature, ethyl acetate and water were added for extraction, the organic layer was washed with water and dried over anhydrous magnesium sulfate. The residue was purified by silica gel column chromatography (hexane : ethyl acetate), and isoquinoline-6-carbonitrile (234mg, 83percent) was obtained as a yellow solid. Lastly, isoquinoline-6-carbonitrile (51mg, 0.331 mmol) was dissolved in diethyleneglycol (1.0mL), potassium hydroxide (9mg, 0.166mmol) was added thereto, followed by stirring at 160°C for 3 hours. The reaction mixture was allowed to room temperature, neutralized using hydrochloric acid, extracted with ethyl acetate, dried over anhydrous magnesium sulfate, then, the solvent was evaporated. Water was added to the residue, the precipitated solid was collected, washed with water, dried in vacuo, so as to obtain the title compound (12mg, 21 percent) as a yellow solid.A solution prepared by adding (4-bromobenzylydene)-(2, 2-diethoxyethyl) amine (synthesized from 4-bromobenzaldehyde, according to the method described in J. Org. Chem., vol. 48, 3344-3346 (1983)) (51.4g, 0.189mmol) to an ice-cold concentrated sulfuric acid (20g) was added to a solution prepared by adding diphosphorus pentoxide (40g) to an ice-cold concentrated sulfuric acid (360g), and the solution was stirred at 160°C for 2 hours. The reaction solution was gradually cooled to 0°C, the solution was filtered through Celite pad, the filtrate was neutralized with sodium carbonate. This solution was further filtrated through Celite pad, this filtrate was extracted with ethyl acetate and dried over anhydrous magnesium sulfate. The solvent was evaporated, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate), and 6-bromoisoquinoline (482mg, 1.2percent) was obtained as an orange oil. Next, to a solution of 6-bromoisoquinoline (382mg, 1.84mmol) in N, N-dimethylformamide (3.8mL) were added zinc cyanide (431mg, 3.67mmol) and tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) under nitrogen atmosphere, and the mixture was stirred at 100°C for 1 hour. Tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) was further added, and the mixture was stirred for 2.5 hours at 100°C. The reaction mixture was allowed to room temperature, ethyl acetate and water were added for extraction, the organic layer was washed with water and dried over anhydrous magnesium sulfate. The residue was purified by silica gel column chromatography (hexane : ethyl acetate), and isoquinoline-6-carbonitrile (234mg, 83percent) was obtained as a yellow solid. Lastly, isoquinoline-6-carbonitrile (51mg, 0.331 mmol) was dissolved in diethyleneglycol (1.0mL), potassium hydroxide (9mg, 0.166mmol) was added thereto, followed by stirring at 160°C for 3 hours. The reaction mixture was allowed to room temperature, neutralized using hydrochloric acid, extracted with ethyl acetate, dried over anhydrous magnesium sulfate, then, the solvent was evaporated. Water was added to the residue, the precipitated solid was collected, washed with water, dried in vacuo, so as to obtain the title compound (12mg, 21 percent) as a yellow solid.Preparation Example G-1. Isoquinoline-6-carboxylic acid A solution prepared by adding (4-bromobenzylydene)-(2, 2-diethoxyethyl) amine (synthesized from 4-bromobenzaldehyde, according to the method described in J. Org. Chem., vol. 48, 3344-3346 (1983)) (51.4g, 0.189mmol) to an ice-cold concentrated sulfuric acid (20g) was added to a solution prepared by adding diphosphorus pentoxide (40g) to an ice-cold concentrated sulfuric acid (360g), and the solution was stirred at 160C for 2 hours. The reaction solution was gradually cooled to 0C, the solution was filtered through Celite pad, the filtrate was neutralized with sodium carbonate. This solution was further filtrated through Celite pad, this filtrate was extracted with ethyl acetate and dried over anhydrous magnesium sulfate. The solvent was evaporated, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate), and 6-bromoisoquinoline (482mg, 1.2%) was obtained as an orange oil. Next, to a solution of 6-bromoisoquinoline (382mg, 1.84mmol) in N, N-dimethylformamide (3.8mL) were added zinc cyanide (431 mg, 3.67mmol) and tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) under nitrogen atmosphere, and the mixture was stirred at 100C for 1 hour. Tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) was further added, and the mixture was stirred for 2.5 hours at 100C. The reaction mixture was allowed to room temperature, ethyl acetate and water were added for extraction, the organic layer was washed with water and dried over anhydrous magnesium sulfate. The residue was purified by silica gel column chromatography (hexane : ethyl acetate), and isoquinoline-6-carbonitrile (234mg, 83%) was obtained as a yellow solid. Lastly, isoquinoline-6-carbonitrile (51mg, 0.331 mmol) was dissolved in diethyleneglycol (1.0mL), potassium hydroxide (9mg, 0.166mmol) was added thereto, followed by stirring at 160C for 3 hours. The reaction mixture was allowed to room temperature, neutralized using hydrochloric acid, extracted with ethyl acetate, dried over anhydrous magnesium sulfate, then, the solvent was evaporated. Water was added to the residue, the precipitated solid was collected, washed with water, dried in vacuo, so as to obtain the title compound (12mg, 21 %) as a yellow solid.A solution prepared by adding (4-bromobenzylydene)-(2, 2-diethoxyethyl) amine (synthesized from 4-bromobenzaldehyde, according to the method described in J. Org. Chem., vol. 48, 3344-3346 (1983)) (51.4g, 0.189mmol) to an ice-cold concentrated sulfuric acid (20g) was added to a solution prepared by adding diphosphorus pentoxide (40g) to an ice-cold concentrated sulfuric acid (360g), and the solution was stirred at 160C for 2 hours. The reaction solution was gradually cooled to 0C, the solution was filtered through Celite pad, the filtrate was neutralized with sodium carbonate. This solution was further filtrated through Celite pad, this filtrate was extracted with ethyl acetate and dried over anhydrous magnesium sulfate. The solvent was evaporated, and the residue was purified by silica gel column chromatography (hexane:ethyl acetate), and 6-bromoisoquinoline (482mg, 1.2%) was obtained as an orange oil. Next, to a solution of 6-bromoisoquinoline (382mg, 1.84mmol) in N, N-dimethylformamide (3.8mL) were added zinc cyanide (431mg, 3.67mmol) and tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) under nitrogen atmosphere, and the mixture was stirred at 100C for 1 hour. Tetrakis(triphenylphosphine)palladium(0) (42mg, 0.0367mmol) was further added, and the mixture was stirred for 2.5 hours at 100C. The reaction mixture was allowed to room temperature, ethyl acetate and water were added for extraction, the organic layer was washed with water and dried over anhydrous magnesium sulfate. The residue was purified by silica gel column chromatography (hexane : ethyl acetate), and isoquinoline-6-carbonitrile (234mg, 83%) was obtained as a yellow solid. Lastly, isoquinoline-6-carbonitrile (51mg, 0.331 mmol) was dissolved in diethyleneglycol (1.0mL), potassium hydroxide (9mg, 0.166mmol) was added thereto, followed by stirring at 160C for 3 hours. The reaction mixture was allowed to room temperature, neutralized using hydrochloric acid, extracted with ethyl acetate, dried over anhydrous magnesium sulfate, then, the solvent was evaporated. Water was added to the residue, the precipitated solid was collected, washed with water, dried in vacuo, so as to obtain the title compound (12mg, 21 %) as a yellow solid.A solution of 700 mL of 50% by mass of sulfuric acid solution, Add to four bottles, Then, 200 g of 6-cyanoisoquinoline was added with stirring, And then heated to about 120 degrees Celsius temperature, Reflux 2h, TLC monitoring to the disappearance of raw materials, after cooling, precipitation of a large number of solids, poured into about 1.5L crushed ice, pumping, a small amount of water washed 2 times, drying, the S2 step product isoquinoline-6-carboxylic acidIsoquinoline-6-carbonitrile (1 g, 6.49 mmol) was heated to reflux in 10 mL of concentrated hydrochloric acid for 4 h.After the reaction solution was cooled to room temperature, the pH was adjusted to ~6 with a saturated NaHCO3 solution.The resulting white precipitate is collected by filtration, dried, Isoquinoline-6-carboxylic acid (1.2 g, white solid) was obtained.