Cyclobutylamine is a substrate employed in a microwave-assisted synthesis of 7-azaindoles from dihalopyridines. Also it is a reactant in the preparation of imidazo[1,2-b]pyridazine derivatives as selective and orally available Mps1 (TTK) kinase inhibitors.
It has been purified by steam distillation. The aqueous distillate (e.g. 2L) is acidified with 3N HCl (90mL) and evaporated to dryness in a vacuum. The hydrochloride is treated with a few mL of H2O, cooled in ice and a slush of KOH pellets ground in a little H2O is added slowly in portions and keeping the solution very cold. The amine separates as an oil from the strongly alkaline solution. The oil is collected, dried over solid KOH and distilled using a vacuum jacketed Vigreux column (p 11) and protected from CO2 using a soda lime tube. The fraction boiling at 79-83o is collected, dried over solid KOH for 2days and redistilled over a few pellets of KOH (b 80.5-81.5o). Best distil in a dry N2 atmosphere. The purity can be checked by GLC using a polyethylene glycol on Teflon column at 72o, 15 psi, flow rate of 102 mL/min of He. The sample can appear homogeneous but because of tailing it is not possible to tell if H2O is present. The NMR in CCl4 should show no signals less than 1 ppm from TMS. The hydrochloride has a multiplet at ca 1.5-2.6ppm (H 2,2,4,3,3,4,4), a quintet at 3.8 ppm (H 1) and a singlet at 4.75 for NH2 [Roberts & Chambers J Am Chem Soc 73 2509 1951]. The benzenesulfonamide has m 85-86o (from aqueous MeOH) and the benzoyl derivative has m 120.6-121.6o. [Roberts & Mazur J Am Chem Soc 73 2509 1951, Iffland et al. J Am Chem Soc 75 4044 1953, Werner & Casanova Jr Org Synth Coll Vol V 273 1973, Beilstein 12 IV 3.]
