A practical synthesis of 1-cyano-4,5-dimethoxybenzocyclobutene, the key intermediate of Ivabradine, was developed in four or five steps using two different routes. 2-Bromo-4,5-dimethoxyhydrocinnamonitrile was produced via the condensation of 2-bromo-4,5-dimethoxybenzaldehyde with acetonitrile or cyanoacetic acid and reduction by NaBH4. Cyclisation gave 1-cyano-4,5-dimethoxybenzocyclobutene. Overall yields of the routes A and B were 30% and 37% respectively. Route B is a short and simple route, permitting the synthesis of 1-cyano-4,5-dimethoxybenzocyclobutene on a large scale.
