To a solution of tert-butyl 3-(cyanomethylene)azetidine-1-carboxylate (3.0 g, 15 mmol) in tetrahydrofuran (8 mL) was added a 4.0 M solution of hydrogen chloride in 1,4-dioxane (10 mL, 40 mmol). After being stirred at room temperature for two hours, the reaction mixture was concentrated under reduced pressure. The residue was dissolved in tetrahydrofuran (20 mL), and tert-butyl 3-methoxy-4-oxopiperidine-1-carboxylate (3.58 g, 15.62 mmol) and triethylamine (3.126 g, 30.89 mmol) were added. After being stirred at room temperature for 30 minutes, sodium triacetoxyborohydride (8.184 g, 38.61 mmol) was added. The mixture was stirred at room temperature overnight. The resulting solution was diluted with aqueous NaHCO3 and EtOAc. The organic layer was separated and washed with brine, dried over Na2SO4 and concentrated. Purification with combi-flash (20-100% EtOAc in hexanes) afforded 2.8 g (60% yield) of the desired product. LC/MS found: 308.1 (M−56)+.
