The general procedure for the synthesis of tert-butyl 2,3,6,7-tetrahydroazepine-1-carboxylate from tert-butyl bis(but-3-en-1-yl)carbamate was as follows: 500 mL of dichloromethane (DCM) was added to a 1 L round-bottomed flask equipped with a reflux condenser, followed by the addition of tert-butyl bis(but-3-en-1-yl)carbamate (1.00 g, 4.44 mmol). The operation was carried out with reference to the method described by Kuhn, KM et al. in Organic Letters, Vol. 12, No. 5, 2010, pp. 984-987. After heating the reaction solution to 45 °C, Grubbs first generation catalyst (238 mg, 0.289 mmol) was added. The reaction mixture was refluxed at 45 °C for 2 hours. After completion of the reaction, the solvent was removed using a rotary evaporator. The product was purified by column chromatography with the eluent being a hexane solution containing 4% ethyl acetate, resulting in 790 mg (4.01 mmol, 9% yield) of tert-butyl 2,3,6,7-tetrahydroazepine-1-carboxylate as an oil.
