Dimethylformamide → Benzyl 1,4-diazepane-1-carboxylate

To 230 ml of dimethylformamide were added 25 g of homopiperazine and 5.4 g of sodium bicarbonate and then 25 ml of water followed by dropwise addition of 10 g of benzyloxycarbonyl chloride with stirring under ice cooling, and the mixture was stirred at a room temperature overnight. After evaporating off dimethylformamide under a reduced pressure, the reaction mixture was extracted three times with 100 ml of chloroform, and the extract was dried over magnesium sulfate and evaporated to remove the solvent under a reduced pressure. The resulting residue was applied to a silica gel column and eluted with chloroform/methanol (9:1), to obtain 9 g of the title compound as a light yellow liquor liquid.