Hydrochloric Acid → (2R,4S)-Methyl 2-(2-methyl-4-(trifluoromethyl)phenyl)-4-(3-oxo-2,3-dihydroisoxazol-5-yl)-piperidine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

Cis-methyl 4-(3-ethoxy-3-oxopropanoyl)-2-(2-methyl-4-(trifluoromethyl)phenyl)piperidine-1-carboxylate (6.28 g, 15.12 mmol) was dissolved in MeOH (60 mL) and cooled to −40° C. 3.8 M NaOH (3.98 mL, 15.12 mmol) was dissolved in water (6 mL) and added to the mixture and the reaction stirred at −40° C. for 40 min. Hydroxylamine (50% by weight in water, 0.926 mL, 15.12 mmol) was added and stirring continued for 3.5 h at −40° C. The reaction mixture was then added to a preheated 80° C. warm solution of 6 M HCl (76 mL, 453.53 mmol) and stirred for 20 min. The reaction mixture was partitioned between water and DCM. The aqueous phase was extracted twice with DCM and the combined organic phase was dried and evaporated. The compound was purified in two runs by preparative HPLC on a Kromasil C8 column (10 μm 250×50 ID mm) using a gradient of 35-75% acetonitrile in H2O/MeCN/AcOH 95/5/0.2 buffer over 30 minutes with a flow of 100 mL/min. Cis-methyl 2-(2-methyl-4-(trifluoromethyl)phenyl)-4-(3-oxo-2,3-dihydroisoxazol-5-yl)piperidine-1-carboxylate (3.2 g, 55%) was isolated. 1H NMR (400 MHz, cdcl3) δ 1.81-1.93 (m, 2H), 2.21-2.42 (m, 2H), 2.44 (s, 3H), 3.03-3.13 (m, 1H), 3.59 (s, 3H), 3.63-3.75 (m, 1H), 4.12-4.20 (m, 1H), 5.02 (dd, 1H), 5.65 (s, 1H), 7.30 (d, 1H), 7.37-7.44 (m, 2H). MS m/z 383 (M−H)−

Provenance & Evidence