General procedure for the synthesis of ethyl 1-(aminomethyl)cyclobutanecarboxylate from ethyl 1-cyanocyclobutanecarboxylate: ethyl 1-cyanocyclobutanecarboxylate (2 g, 13 mmol) was dissolved in 1% ammonia in ethanol solution (20 mL), and 5% rhodium/alumina catalyst (0.8 g) was added, and the hydrogenation reaction was carried out at room temperature for 3 days. Upon completion of the reaction, the reaction mixture was filtered through diatomaceous earth to remove the catalyst. The filtrate was concentrated and dried to afford the target product ethyl 1-(aminomethyl)cyclobutanecarboxylate (1.5 g, 75%) as a light yellow liquid. The structure of the product was confirmed by 1H NMR (400 MHz, chloroform-d): δ1.29 (t, J=7.1 Hz, 3H), 1.93-1.96 (m, 2H), 2.33-2.49 (m, 4H), 3.07 (s, 2H), 4.18 (q, J=7.2 Hz, 2H).
