General procedure for the synthesis of 1-(oxetan-3-yl)piperazine from benzyl 4-(oxetan-3-yl)piperazine-1-carboxylate: in a 1L three-necked flask, palladium hydroxide (Pd(OH)2, 1.661 g, 2.366 mmol) was added under nitrogen protection. Methanol (MeOH, 130.8 mL) and ethyl acetate (EtOAc, 261.6 mL) were then added and the mixture was degassed by vacuum/nitrogen cycles (3 times). Then benzyl 4-(oxetan-3-yl)piperazine-1-carboxylate (32.7 g, 118.3 mmol) was added and the reaction mixture was stirred overnight under hydrogen atmosphere. After completion of the reaction, the mixture was filtered through a pad of diatomaceous earth and washed sequentially with ethyl acetate and methanol. The filtrate was concentrated under reduced pressure to afford the target product 1-(oxetan-3-yl)piperazine (25) as an orange oil (8.1 g, quantitative yield). The structure of the product was confirmed by 1H NMR (500 MHz, DMSO-d6) with the following characteristic peaks: δ 4.51 (t, 2H), 4.41 (t, 2H), 3.36-3.30 (masked signal, 1H), 2.69 (t, 4H) and 2.14 (br s, 4H).
