General procedure for the synthesis of methyl isoquinoline-3-carboxylate from methyl 1,2,3,4-tetrahydroisoquinoline-3-carboxylate: In a 250 mL aubergine vial, (3S)-1,2,3,4-tetrahydroisoquinoline-3-carboxylate (2) (4.23 g, 22.15 mmol) and N,N-dimethylformamide (50 mL) were added. Subsequently, potassium permanganate (2.97 g, 18.79 mmol) was added to the solution. After the reaction was carried out for 6 hours, ethanol (50 mL) was added and stirred for 30 minutes. After that, the solvent was removed and the residue was dissolved with methanol (30 mL). Finally, the residue was purified by column chromatography to give a colorless solid product (858 mg, 24.56% yield).
