Hydrogen Bromide → (2S,3S,6S)-6-Ethyl-3-nitro-2-phenyl-piperidine HBr salt

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Reaction Steps

(2S,3S,6S)-6-Ethyl-3-nitro-2-phenyl-piperidine-1-carboxylic acid benzyl ester (40 gm; 108 mmol) was dissolved in 80 ml of 30% HBr in propionic acid at room temperature. There was a rapid evolution of gas and the desired product precipitated after 3–5 minutes. The mixture was stirred at room temperature for 16 hours. The tan solids were collected, washed with ether and dried in vacuo to afford 29 gm of the (2S,3S,6S)-6-Ethyl-3-nitro-2-phenyl-piperidine HBr salt. 1H NMR (D2O, 400 MHz) δ 7.4–7.2 (br.m, 5H), 5.25 (m, 1H), 4.95 (d), 3.65 (br.m.), 2.4–2.0 (m), 1.9–1.55 (m), 0.85 (t, 3H) ppm. Mass spectra m/z=235 (p+1).

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