Methylamine → Benzyl 3-fluoro-4-(methylamino)piperidine-1-carboxylate

Participants

Reaction Steps

To a solution of 9.4 g (37.5 mmol) of 2-2 in 150 mL of 1,2-dichloroethane was added 37.5 mL (74.9 mmol) of a 2M solution of methylamine in THF and 11.9 g (56.2 mmol) of Na(OAc)3BH. After stirring for 2 h, the reaction was quenched with saturated aqueous K2CO3, partitioned with EtOAc, separated, and the aqueous phase extracted 3×EtOAc. The combined organic extracts were washed with brine, dried over MgSO4, filtered, and concentrated by rotary evaporation. The residue was loaded onto a silica gel column and eluted with 80:10:10 CHCl3/EtOAc/MeOH to provide both the cis and trans isomers of 2-2a as colorless oils. Data for the trans isomer of 2-2a, first to elute (confirmed by NOE analysis): 1HNMR (600 MHz, CD2Cl2) δ 7.4-7.3 (m, 5H), 5.1 (m, 2H), 4.4-4.1 (m, 2H), 3.9 (m, 1H), 3.15-3.05 (m, 2H), 2.75 (m, 1H), 2.4 (s, 3H), 2.0 (in, 1H), 1.25 (m, 1H) ppm. Data for the cis isomer of 2-2a, second to elute (confirmed by NOE analysis): 1HNMR (600 MHz, CD2Cl2) δ 7.4-7.2 (m, 5H), 5.1 (m, 2H), 4.9-4.7 (m 1H), 4.4 (m, 1H), 4.15 (m, 1H), 3.1-2.9 (m, 2H), 2.6 (m, 1H), 2.4 (s, 3H), 1.8 (m, 1H), 1.6 (m, 1H) ppm. HRMS (ES) calc'd M+H for C14H19F1N2O2: 267.1504. Found: 267.1500.

Provenance & Evidence