Methanol → Methyl isoquinoline-5-carboxylate
Reaction equation
[CH:1]1[C:10]2[CH:9]=[CH:8][CH:7]=[C:6]([C:11]([OH:13])=[O:12])[C:5]=2[CH:4]=[CH:3][N:2]=1.S(=O)(=O)(O)O.[CH3:19]O>>[CH:1]1[C:10]2[CH:9]=[CH:8][CH:7]=[C:6]([C:11]([O:13][CH3:19])=[O:12])[C:5]=2[CH:4]=[CH:3][N:2]=1Participants
4
Procedure
Isoquinoline-5-carboxylic acid (5.6 g, 32.36 mmol) obtained in Step (2) above and methanol (90 mL) were mixed and stirred. The reaction solution was slowly added with sulfuric acid (15 mL, 259 mmol) and refluxed for about 20 hours. The reaction mixture was cooled to room temperature, and the solvent was distilled under reduced pressure. The concentrate was added with distilled water and adjusted to have a pH value in a range of 10˜11 by adding DIPEA. The reaction mixture was diluted with ethyl acetate, and washed with a saturated aqueous sodium bicarbonate solution and saline. The organic layer thus obtained was dried over anhydrous sodium sulfate, filtered, and concentrated under reduced pressure to obtain the title compound (5.8 g, 96%).