N,N'-Dicyclohexylurea → 2-(4-dimethylamino-4-phenylcyclohexylidene)-1-[3-(1H-indol-3-yl)piperidine-1-yl]-ethanone

Participants

Reaction Steps

1-hydroxybenzotriazole (675 mg, 5.0 mmole), 3-piperidine-3-yl-1H-indole (500 mg, 2.5 mmole) and N-methylmorpholine (0.555 ml, 5.0 mmole) were added in succession under argon to a solution of (4-dimethylamino-4-phenylcyclohexylidene)-acetic acid (739 mg, 2.5 mmole) in dry dimethylformamide (10 ml). The solution was cooled in an ice bath and dicyclohexylcarbodiimide (1.03 g, 5.0 mmole) was added. The reaction mixture was stirred for 5 days at RT, the dicyclohexylurea precipitating out little by little. The reaction mixture was worked up by separating the precipitated urea and adding the filtrate to a mixture of saturated NaCl solution (40 ml) and saturated NaHCO3 solution (10 ml). Further urea together with 2-(4-dimethylamino-4-phenylcyclohexylidene)-1-[3-(1H-indol-3-yl)-piperidine-1-yl]-ethanone thereupon precipitated out (1.5 g). The aqueous phase was diluted with water (300 ml), 5M sodium hydroxide (7 ml, 35 mmole) was added, and the whole was kept for 16 hours at 5° C. The crude product thereupon precipitated out as a colourless solid (464 mg). The crude product of 2-(4-dimethylamino-4-phenylcyclohexylidene)-1-[3-(1H-indol-3-yl)-piperidine-1-yl]-ethanone was purified chromatographically on silica gel (60 g) with EE/methanol (4:1) and (2:1) and obtained in a yield of 30% (322 mg)—2-(4-dimethylamino-4-phenylcyclohexylidene)-1-[3-(1H-indol-3-yl)-piperidine-1-yl]-ethanone was obtained as a diastereoisomer mixture. A separation was not possible.

Provenance & Evidence