Practical Synthesis of N-{4-[(2-Methyl-4,5-dihydroimidazo[4,5-d][1]benzazepin- 6(1H)-yl)carbonyl]phenyl}biphenyl-2-carboxamide Monohydrochloride:  an Arginine Vasopressin Antagonist

A novel, reliable, and cost-effective synthetic route to N-{4-[(2-methyl-4,5-dihydroimidazo[4,5-d][1]benzazepin-6(1H)-yl)carbonyl]phenyl}biphenyl-2-carboxamide monohydrochloride (1, YM087), a potent Arginine vasopressin antagonist, has been developed. Using moisture-controlled potassium carbonate, imidazole formation from α-bromoketone furnished imidazobenzazepine, avoiding potential oxazole-ring formation. Catalytic reduction of nitro imidazobenzazepine afforded the corresponding amine in high yields. Treatment of the imidazole-containing amine directly, with a carbonyl chloride, afforded the target amide circumventing protection of the imidazole.