GENERAL STEPS: Preparation of Example 3 2-methyl-1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid
0.364 g (2.07 mmol) of 1,2,3,4-tetrahydroisoquinoline-3-carboxylic acid was dissolved in 25 mL of formic acid. To this solution was added 2.5 mL of 37% formaldehyde solution. The resulting mixture was heated to reflux for about 17 hours. Upon completion of the reaction, the mixture was cooled and concentrated under reduced pressure to give a gummy substance. The gummy was dissolved in 3.0 mL of water and the pH was adjusted with hydrochloric acid to 2. Subsequently, purification was carried out using ion exchange chromatography (Dowex 50x-8, 100 mesh) to give 0.21 g of yellow powdery product in 53% yield.
Product characterization data:
1H NMR (DMSO-d6): δ 2.56 (s, 3H), 3.01 (m, 2H), 3.48 (t, 1H), 3.9 (dd, 2H), 7.05 (m, 1H), 7.13 (m, 3H).
MS (FD): m/e 192 (M+2).
