Methyl 4-iodobenzoate (1.00 g, 3.82 mmol, 1.0 eq) was dissolved in DMF and tert-butyl 1,4-diazepane-1-carboxylate (765 mg, 3.82 mmol, 1.0 eq), caesium carbonate (2.49 g, 7.63 mmol, 2.0 eq), 2-acetylcyclohexanone (101 μl, 0.76 mmol, 0.20 eq [20 mol %]) and copper iodide (37 mg, 0.19 mmol, 0.05 eq [5 mol %]) were added. The reaction mixture was stirred at 90° C. under nitrogen for 7 h. The reaction mixture was evaporated, dissolved in DCM (50 ml), washed with water (20 ml), saturated ammonium chloride solution (20 ml), dried over MgSO4, filtered and evaporated. The crude product was purified by silica column chromatography, eluting with 0-1% MeOH in DCM. The product containing fractions were combined, evaporated and dried in vacuo to give tert-butyl 4-(4-methoxycarbonylphenyl)-1,4-diazepane-1-carboxylate (168 mg, 13%) as a yellow oil.
