Abstract: The invention is directed to a process for the synthesis of 5-chlorocarbonyl-5H-dibenz[b,f]azepine, which is the precursor for the industrial scale synthesis of 5-carbamoyl-5H-dibenz[b,f]azepine. The latter substance is used as pharmaceutical compound. In the process phosgene is passed into a suspension of iminostilbene in an inert solvent at 20.degree. C.-60.degree. C. until the iminostilbene reacted to form an almost equimolar mixture of 5-chlorocarbonyl-5H-dibenz[b,f]azepine and iminostilbene hydrochloride, and then iminostilbene is released from the iminostilbene hydrochloride by the addition of an aqueous base. The iminostilbene so released is also made available for a complete phosgenation while an acidic reaction environment is maintained. After the iminostilbene reacted completely, the reaction mixture is heated slowly to 20.degree. C.-90.degree. C. with stirring and is detoxified by the hydrochloric acid that is formed.