7-Chloro-1,2,3,4-tetrahydrobenzo(b)azepin-5-one

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7-Chloro-1,2,3,4-tetrahydrobenzo[b]azepin-5-one is an intermediate in the synthesis of Tolvaptan (T536650) (OPC-41061), an orally active nonpeptide arginine vasopressin V2 receptor antagonist

The synthetic method of 7-Chloro-1,2,3,4-tetrahydrobenzo(b)azepin-5-one comprises the following steps: carrying out an acylation reaction between 4-chloroaniline and succinic anhydride to obtain 4-(4-chloroaniline)-4-oxobutyric acid; carrying out an intramolecular Friedel-Craft reaction on 4-(4-chloroaniline)-4-oxobutyric acid to obtain 7-chloro-3,4-tetrahydrobenzo[b]azepine-2,5-one; reacting 7-chloro-3,4-tetrahydrobenzo[b]azepine-2,5-one with ethylene glycol to obtain 7-chloro-3,4-tetrahydrobenzo[b]azepine-2-one-5-glycol ketal; reducing 7-chloro-3,4-tetrahydrobenzo[b]azepine-2-one-5-glycol ketal, and carrying out de-ketalation under an acidic condition to obtain 7-Chloro-1,2,3,4-tetrahydrobenzo(b)azepin-5-one.