Step C: Synthesis of 3,3-difluorocyclobutylamine hydrochloride. A mixture of benzyl (3,3-difluorocyclobutyl)carbamate (1.47 g, 6.1 mmol) and 10% Pd/C (1 g) in methanol (20 mL) was subjected to a hydrogen atmosphere (1 atm) and stirred overnight at room temperature. After completion of the reaction, the mixture was filtered through a diatomaceous earth pad and washed with methanol. Concentrated hydrochloric acid (2 mL) was added to the filtrate, followed by evaporation of the solvent under vacuum to afford the target product 3,3-difluorocyclobutanamine hydrochloride (0.8 g, 85% yield). The product was characterized by 1H NMR (400 MHz, DMSO-d6): δ 8.60 (m, 3H), 3.64 (m, 1H), 2.89 (m, 4H).
