1,1'-Carbonyldiimidazole → 7-chloro-3-{1-[2-(2-methyl-5-nitrophenyl)-1-oxoethyl]-piperidin-4-yl}-1H-indole

Participants

Reaction Steps

A mixture of (2-methyl-5-nitrophenyl)acetic acid (2.5 g) and 1,1′-carbonyldiimidazole (2.1 g) in dimethyl formamide (50 mL) was stirred at room temperature for 15 min and subsequently added a solution of 7-chloro-3-(piperidin-4-yl)-1H-indole (3.0 g) in dimethyl formamide (50 mL). The resulting mixture was stirred at room temperature for 1 h and poured onto an ice/water mixture. The compound was isolated by filtration and dissolved in tetrahydrofuran. The organic phase was washed with brine, dried (MgSO4), filtered and concentrated in vacuo to give 7-chloro-3-{1-[2-(2-methyl-5-nitrophenyl)-1-oxoethyl]-piperidin-4-yl}-1H-indole (4.7 g). A mixture of 7-chloro-3-{1-[2-(2-methyl-5-nitrophenyl)-1-oxoethyl]-piperidin-4-yl}-1H-indole (16.6 g) and ethanol (500 mL) was heated to reflux temperature and subsequently added concentrated HCl (22 mL) and iron powder (11.3 g) over a period of 30 min. The resulting mixture was boiled under reflux for an additional 90 min, filtered hot and concentrated in vacuo. The residue was dissolved in tetrahydrofuran, and the organic phase was washed with brine, dried (MgSO4), filtered and concentrated in vacuo to give give 7-chloro-3-{1-[2-(5-amino-2-methylphenyl)-1-oxoethyl]-piperidin-4-yl}-1H-indole (14.3 g). A suspension of lithium aluminium hydride (6.4 g) in tetrahydrofuran (250 mL) was cooled (5° C.) and subsequently added a mixture of 7-chloro-3-{1-[2-(5-amino-2-methylphenyl)-1-oxoethyl]-piperidin-4-yl}-1H-indole (16.0 g) in tetrahydrofuran (250 mL). The resulting mixture was boiled under reflux for 90 min, cooled to 5° C. and quenched by the addition of water. The mixture was dried (MgSO4), stirred for 10 min, filtered and concentrated in vacuo to give 7-chloro-3-{1-[2-(5-amino-2-methylphenyl)ethyl]piperidin-4-yl}-1H-indole (12.4 g). A solution of 7-chloro-3-{1-[2-(5-amino-2-methylphenyl)ethyl]piperidin-4-yl}-1H-indole (1.0 g) and N-ethyldiisopropylamine (0.7 g) in tetrahydrofuran (25 mL) was cooled (5° C.) and subsequently added a solution of (4-fluorophenyl)acetyl chloride in tetrahydrofuran (25 mL). The resulting mixture was stirred at room temperature for 1 h and subsequently poured onto brine. The aqueous phase was extracted with tetrahydrofuran, and the combined organic phases were dried (MgSO4), filtered and concentrated in vacuo. The residue was purified by flash chromatography on silicagel (eluent:ethyl acetate/heptane/triethylamine 70:30:5) to give the product (0.81 g). LC/MS (m/z) 504 (MH+), RT=2.45, purity: 62%.

Provenance & Evidence