N-bromobutanimide → tert-Butyl 4-(1-bromo-2-methoxy-2-oxoethyl)piperidine-1-carboxylate

Participants

Reaction Conditions

Reaction Steps

Commercially available methyl 2-(1-tert-butoxycarbonyl-4-piperidinyl)-acetate (Astatech, 2.57 g, 10.0 mmol) was dissolved in anhydrous THF (20 mL) under argon, cooled to −78° C., treated dropwise with a 1N solution of LHMDS in THF (20 mL), and stirred under positive Ar pressure for 30 mins. Bromotrimethylsilane (2.10 mL, 15.9 mmol) was added dropwise via dry syringe over 5 mins, then a solution of freshly recrystallized N-bromosuccinimide (2.14 g, 12.0 mmol) in anhydrous THF (20 mL) was added in one portion from an addition funnel. The reaction was kept at −78° C. for 2 hrs then warmed to ambient temperature. The crude reaction was concentrated in vacuo then partitioned between saturated aq. NaHCO3 and ethyl acetate. The aqueous layer was extracted twice with ethyl acetate, and the combined organic layers washed with brine, dried over Na2SO4, filtered, and filtrate concentrated in vacuo giving 4.7 g of orange slurry. This was purified by flash column chromatography on silica gel (0 to 10% EtOAc/DCM step gradient elution), and the combined TLC-pure fractions were concentrated and dried in vacuo giving the title compound as a viscous, pale yellow oil. 1H NMR (CHLOROFORM-d) δ: 4.05-4.26 (m, 2H), 4.02 (d, J=8.8 Hz, 1H), 3.79 (s, 3H), 2.70 (br. s., 2H), 1.97-2.10 (m, 4H), 1.57-1.68 (m, 2H), 1.45 (s, 9H), 1.13-1.32 (m, 3H).

Provenance & Evidence