To a stirred solution of 8-chloro-2-methyl-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole (0.2 g, 0.00090 mol) and copper sulfate (0.023 g, 0.00009 mol) in toluene (15 mL) was added potassium carbonate (0.25 g, 0.0018 mol) and 1,10 phenanthroline (0.033 g, 0.000018 mol). The reaction mixture was stirred for 5 min at RT. A solution of 5-(bromoethynyl)-2-propylpyridine (0.221 g, 0.00099 mol) in toluene (5 mL) was added to the reaction mixture. The reaction mixture was stirred for 18 h at 80° C. The reaction was monitored by TLC. After completion of reaction, water (30 mL) was added, and the mixture extracted with EtOAc (3×30 mL). The organic layer was dried over anhydrous sodium sulfate, solvent was removed under reduced pressure, and the crude product purified by column chromatography using silica (100-200 mesh) and 3% MeOH:DCM as eluent, diameter of column—5.0 cm, height of silica—approx. 5 inch) to provide the desired compound as a yellow colored oil (0.06 g, 18% yield). 8-Chloro-2-methyl-5-((6-propylpyridin-3-yl)ethynyl)-2,3,4,5-tetrahydro-1H-pyrido[4,3-b]indole (0.056 g, 0.000153 mol) was dissolved in THF (1.0 mL). A solution of oxalic acid dihydrate (0.02 g, 0.000153 mol) in THF (2 mL) was added and stirred for 30 min at RT. The precipitate was filtered and dried to give the oxalate salt as an off-white solid (0.050 g, 80% yield). 1H NMR (CD3OD, oxalate salt) δ (ppm): 8.65 (s, 1H), 7.95 (d, 1H), 7.62 (d, 1H), 7.60 (s, 1H), 7.38 (dd, 2H), 4.78 (m, 2H), 4.50 (s, 2H), 3.76 (m, 2H), 3.10 (s, 3H), 2.80 (m, 2H), 1.76 (m, 2H), 1.0 (t, 3H).
