Acetic Acid → tert-Butyl 4-(isobutylamino)piperidine-1-carboxylate

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Reaction Steps

Sodium triacetoxyborohydride (32.0 g, 151.0 mmol) is added to a stirred solution of tert-butyl 4-oxo-1-piperidine carboxylate (20.0 g, 100.4 mmol), isobutylamine (10.5 ml, 105.7 mmol), acetic acid (6.0 ml, 104.8 mmol) and 1,2-dichloroethane (300 ml). The reaction is stirred for 18 hours at room temperature under nitrogen. The reaction is poured into 2N NaOH (300 ml) and extracted with ethyl acetate (200 ml×3). The ethyl acetate is dried over sodium sulfate and then the sodium sulfate is filtered off. The crude product is concentrated on a rotary evaporator and purified by flash chromatography on silica gel eluting with 0.5% concentrated ammonium hydroxide/5% ethanol/chloroform to yield (24.5 g, 95%) of 4-isobutylamino-piperidine-1-carboxylic acid tert-butyl ester: mass spectrum (ion spray): m/z=257.1 (M+1); 1H NMR (CDCl3): δ=4.01 (2H, br s), 2.78-2.75 (2H, m), 2.60-2.53 (1H, m), 2.42 (2H, d), 1.83-1.64 (3H, m), 1.56 (1H, br s), 1.44 (9H, s), 1.28-1.18 (2H, m), 0.90 (6H, d).

Provenance & Evidence