Ammonia → HCID 22714419, compound

Participants

Reaction Steps

A mixture of (2-methyl-5-nitrophenyl)acetic acid (47 g) and thionyl chloride (62 mL) in dichloromethane (400 mL) was boiled under reflux for 5 h and concentrated in vacuo. A small amount of the residue (5 g) was dissolved in tetrahydrofuran (100 mL) and added dropwise to a mixture of 6-chloro-3-(3,6-dihydro-2H-pyridin-4-yl)-1H-indole (6.0 g) and triethylamine (5 mL) in tetrahydrofuran (250 mL) at 0° C. over a period of 10 min. The mixture was concentrated in vacuo, aqueous 2 N sodium hydroxide (400 mL) and ethyl acetate (400 mL) was added, whereby 6-chloro-3-{1-[2-(2-methyl-5-nitrophenyl)-1-oxoethyl]-3,6-dihydro-2H-pyridin-4-yl}-1H-indole precipitated and was collected by filtration (3.7 g). The organic phases were isolated, washed with brine, dried (Na2SO4), filtered and concentrated in vacuo. The residue was purified by flash chromatography on silicagel (eluent:ethyl acetate/heptane 2:1) to give another batch of 6-chloro-3-{1-[2-(2-methyl-5-nitrophenyl)-1-oxoethyl]-3,6-dihydro-2H-pyridin-4-yl}-1H-indole (2.2 g). A mixture of 6-chloro-3-{1-[2-(2-methyl-5-nitrophenyl)-1-oxoethyl]-3,6-dihydro-2H-pyridin-4-yl}-1H-indole (5.3 g) in tetrahydrofuran (100 mL) and tin(II) chloride dihydrate (14.5 g) in ethanol (150 mL) was boiled under reflux for 2 h, and the solvent reduced to about 100 mL in vacuo. Aqueous ammonia was added and the organic phase was removed in vacuo. The aqueous phase was extracted with ethyl acetate, and the combined organic phases were washed with brine, dried (Na2SO4), filtered and concentrated in vacuo to give 6-chloro-3-{1-[2-(5-amino-2-methylphenyl)-1-oxoethyl]-3,6-dihydro-2H-pyridin-4-yl}-1H-indole (5.1 g). This compound was dissolved in tetrahydrofuran (200 mL) and added dropwise to a suspension of lithium aluminium hydride (1.5 g) in tetrahydrofuran (100 mL) at 10° C. over a period of 15 min. The resulting mixture was stirred at room temperature for 16 h and subjected to a standard work up procedure to give crude 6-chloro-3-{1-[2-(5-amino-2-methylphenyl)ethyl]-3,6-dihydro-2H-pyridin-4-yl}-1H-indole (7.5 g, includes tetrahydrofuran). Crude compound (4.0 g) was dissolved in acetic acid (100 mL) followed by the addition of platinum oxide (400 mg), and the resulting mixture was shaken under 3 atmosphere hydrogen pressure for 6 h at room temperature. The mixture was filtered and added water (400 mL) followed by the addition of aqueous ammonia to basic pH. The aqueous phase was extracted with an ethyl acetate, and the combined organic phase was washed with brine, dried (Na2SO4), filtered and concentrated in vacuo to give 6-chloro-3-{1-[2-(5-amino-2-methylphenyl)ethyl]piperidin-4-yl}-1H-indole (2.4 g). The compound was dissolved in tetrahydrofuran (200 mL) and triethylamine (1 mL), and the mixture was cooled to 0° C. followed by dropwise addition of acetyl chloride (0.5 mL) in dichloromethane (30 mL). The resulting mixture was stirred at room temperature for 2 h, filtered and concentrated in vacuo. The residue was purified by flash chromatography on silicagel (eluent:ethyl acetate/ethanol/triethylamine 80:20.4) to give crude title compound that was collected as the fumerate salt from ethanol (0.7 g). Mp 164-166° C. 1H NMR (DMSO-d6): 1.85-2.10 (m, 4H); 2.25 (s, 3H); 2.65-3.00 (m, 7H); 3.30-3.45 (m, 2H); 6.60 (s, 3H (fumerate)); 7.00 (dd, 1H); 7.10 (d, 1H); 7.20 (d, 1H); 7.30-7.45 (m, 3H); 7.65 (d, 1H); 9.85 (s, 1H); 11.05 (s, 1H). MS m/z: 410 (MH+), 259, 247, 176.

Provenance & Evidence