General procedure for the synthesis of 4-methyl-1,2,3,4-tetrahydroisoquinoline hydrochloride from 4-methylisoquinoline: 0.50 g (3.5 mmol) of 4-methylisoquinoline was dissolved in 50 mL of methanol under a hydrogen atmosphere, and the hydrogenation reaction was carried out with the addition of 50 mg of dichloromethane and 3.5 mL of aqueous 1 M hydrochloric acid. Upon completion of the reaction, the catalyst was removed by diafiltration followed by evaporation of the reaction mixture. A mixture containing the starting material and the product was obtained, which could be used directly in the next step of the reaction without further purification. The yield was 0.60 g, which represents 94% of the theoretical yield.ESI-MS detection showed: m/z = 148 ([M + H]+).
