tert-Butyl 4-(3,3-difluoroazetidin-1-yl)piperidine-1-carboxylate

288315-03-7

79099-07-3

1093066-74-0

GENERAL STEPS: To a solution of N-tert-butoxycarbonyl-4-piperidone (1.0 g, 5.0 mmol) in dichloroethane (DCE, 50 mL) was added 3,3-difluoroazetidine hydrochloride (712 mg, 5.5 mmol). The reaction mixture was stirred at room temperature for 15 minutes, followed by the addition of sodium triacetoxyborohydride (1.59 g, 7.5 mmol) and continued stirring for 17 hours. After completion of the reaction, the reaction mixture was diluted with saturated brine and extracted with dichloromethane (DCM). The organic layer was separated, dried over anhydrous sodium sulfate (Na2SO4) and concentrated under reduced pressure. The residue was purified by silica gel column chromatography to afford tert-butyl 4-(3,3-difluoroazetidin-1-yl)piperidine-1-carboxylate as a light yellow solid (1.2 g, 88% yield). Tert-butyl 4-(3,3-difluoroazetidin-1-yl)piperidine-1-carboxylate (552 mg, 2.0 mmol) was dissolved in dichloromethane (DCM, 4 mL) and trifluoroacetic acid (TFA, 2 mL) was added. The reaction mixture was stirred at room temperature for 45 min. Subsequently, the mixture was loaded onto an Isolute SCX-2 column, washed first with methanol (MeOH) and then eluted with a methanol solution of 2 M ammonia to give the target compound as a light yellow solid (271 mg, 77% yield). 61H NMR (400 MHz, CDCl3): δ 1.16-1.27 (m, 2H), 1.63-1.72 (m, 2H), 2.14-2.23 (m, 1H), 2.54-2.62 (m, 2H), 3.09 (dt, J = 12.7,3.9Hz, 2H), 3.46-3.57 (m, 4H).