General procedure for the synthesis of ethyl 1-azepane-N-Boc-4-carboxylate from 1-tert-butyl 4-ethyl 1H-azepine-1,4-dicarboxylate from 2,3,6,7-tetrahydro-1H-azepine-1,4-dicarboxylic acid: 1-tert-butyl 4-ethyl azepine-1,4-dicarboxylate (0.54 g, 2.0 mmol) was dissolved in 20 ml of methanol, 10% Pd/C (50 mg) was added , and the reaction was carried out overnight under hydrogen atmosphere. After completion of the reaction, the solid catalyst was removed by filtration and the filtrate was concentrated. The resulting residue was purified by fast column chromatography (eluent: hexane solution of 20% ethyl acetate) to afford the target product ethyl 1-azepane-N-Boc-4-carboxylate (310 mg, 55% yield). The mass spectrum (DCI/NH3) showed m/z 272 (M+H)+.
