General procedure for the synthesis of 3-methylazetidine hydrochloride from benzyl 3-methylene azetidine-1-carboxylate: the product of step (iii) (14.1 g) was dissolved in ethanol (100 mL), 10% Pd/C (JM type 87L) (1.48 g) was added and treated under hydrogen atmosphere. The reaction mixture was stirred for 40 h at 20 °C under hydrogen pressure of 4.50 bar to remove the Cbz protecting groups. Subsequently, the mixture was transferred to ethanol (100 mL) containing palladium hydroxide (2 g) and continued to be hydrogenated at 4.50 bar hydrogen pressure for 24 hours. Upon completion of the reaction, the mixture was filtered through a pad of diatomaceous earth and the filtrate was cooled to 0°C in an ice bath. To the cooled filtrate was added dropwise a dioxane solution (26.0 mL) of 4 M HCl, followed by evaporation of the solution to dryness to give the title product 3-methylazetidine hydrochloride (7.46 g) as a light brown oil. The product was characterized by 1H NMR (400 MHz, CDCl3): δ 9.24 (s, 2H), 3.95 (ddd, J = 7.4, 9.8, 11.4 Hz, 2H), 3.55-3.45 (m, 2H), 2.85 (dt, J = 6.7, 14.2 Hz, 1H), 1.16 (d, 3H).
