General procedure for the synthesis of cyclobutylmethylamine hydrochloride from cyclobutanecarbonitrile: A tetrahydrofuran solution of borane (1 M, 296 mL, 296 mmol) was slowly added to a tetrahydrofuran (60 mL) solution of cyclobutanecarbonitrile (20 g, 247 mmol) under argon protection. The reaction mixture was heated to reflux and kept overnight. Upon completion of the reaction, the mixture was cooled in an ice-water bath and methanol (120 mL) was added slowly and dropwise, controlling the reaction temperature below 20 °C. Subsequently, a methanolic solution of 4M hydrochloric acid (300mL) was added and the temperature continued to be controlled below 20°C. The resulting solution was heated and refluxed for 2.5 hours. At the end of the reaction, the mixture was cooled and concentrated. The residue was diluted with methanol (100 mL) and concentrated again and the process was repeated. Ether was added to the residue, stirred for 30 min and filtered to give the title compound cyclobutylmethylamine hydrochloride (25.9 g, 86% yield) as a white solid. NMR hydrogen spectrum (300 MHz, DMSO-d6) δ ppm: 1.70-1.86 (m, 4H), 1.97-2.04 (m, 2H), 2.46-2.61 (m, 1H), 2.75-2.84 (m, 2H), 8.02 (br s, 3H).
