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In a dry flask equipped with a Dean-Stark trap and reflux condenser, ethyl 1-(t-butoxycarbonyl)-3-oxo-4-piperidinecarboxylate (4.19 g, 15.4 mmol) was dissolved in toluene (50 mL). (R)-(+)-a-Methylbenzylamine (1.91 g, 15.8 mmol) and p-toluenesulfonic acid monohydrate (0.019 g, 0.1 mmol) were added and the mixture heated to reflux for 6 hours. The crude reaction mixture was concentrated in vacuo to give the desired amine (5.78 g, 100%) as a thick orange oil. 1H NMR (300 MHz, CDCl3), δ: 7.36 (t, J=3, 2H), 7.33 (t, J=4, 1H), 7.31 (dd, J=3, J′=4, 2H), 4.59 (m, 1H), 4.16 (q, J=7, 2H), 3.59 (m, 2H), 2.34 (m, 2H), 1.58 (bs, 2H), 1.52 (d, J=3, 3H), 1.29 (s, 9H), 1.26 (t, 3H, J=7). MS (ESI), m+/z: (M+H)+=375.

1. customIn a dry flask equipped with a Dean-Stark trap
2. temperaturereflux condenser
3. temperaturethe mixture heated
4. temperatureto reflux for 6 hours
5. customThe crude reaction mixture
6. concentrationwas concentrated in vacuo