Acetic Acid → 4-(2,5-Dimethyl-phenylamino)-piperidine-1-carboxylic acid tert-butyl ester

Participants

Reaction Steps

A solution of 4-oxo-piperidine-1-carboxylic acid tert-butyl ester (1 g, 0.00502 mole) in dry 1,2-dichloroethane (10 mL) was stirred under an atmosphere of nitrogen for 10 minutes. 2,5-dimethylaniline (0.73 g, 0.00602 mole), acetic acid (0.301 g, 0.005 mole) and sodium triacetoxyborohydride (1.596 g, 0.00753 mole) were then added portionwise and stirring was continued at ambient temperature for 16 hours. The reaction mixture was basified with sodium bicarbonate solution and the product was extracted with dichloromethane. The dichloromethane layer was washed with brine solution, dried over sodium sulfate and concentrated under reduced pressure. The resulting transparent viscous liquid was purified by column chromatography using neutral aluminium oxide (1% ethyl acetate in hexane) to afford 1.5 g (82%) of 4-(2,5-dimethyl-phenylamino)-piperidine-1-carboxylic acid tert-butyl ester. 1H NMR (CDCl3): δ 7.0 (t, 1H), 6.6 (d, 2H), 4.2 (dd, 2H), 3.5 (m, 1H), 2.9 (t, 2H), 2.3 (t, 3H), 2.15 (s, 3H), 2.05 (s, 3H), 1.5 (s, 9H), 1.3 (t, 2H). A solution of 4-(2,5-dimethyl-phenylamino)-piperidine-1-carboxylic acid tert-butyl ester (1.5 g, 0.00492 mole) in ethyl acetate.HCl (7 mL) was stirred at ambient temperature for 2 hours. The reaction mixture was concentrated under reduced pressure and the residue was washed with ether and dried to afford 1.1 g (80%) of (2,5-dimethyl-phenyl)-piperidin-4-yl-amine dihydrochloride. LCMS: 205.16 (M+1)+, 92.74%, 1H NMR (DMSO-d6): δ 9.4 (d, 1H), 9.0 (d, 1H), 7.2 (d, 2H), 7.1 (s, 1H), 3.7 (m, 1H), 3.6 (s, 1H), 3.4 (d, 2H), 3.2 (bs, 1H), 2.9 (m, 2H), 2.4 (s, 3H), 2.3 (s, 3H), 2.1 (m, 4H).

Provenance & Evidence