Synthesis of Tricyclic 4-Chloro-pyrimido[4,5-b][1,4]benzodiazepines

A novel methodology was developed for the efficient synthesis of 4-chloro-pyrimido[4,5-b][1,4]benzodiazepines. The key is the intramolecular Friedel−Crafts cyclization of 5-amino-4-(N-substituted)anilino-6-chloropyrimidine with either a carboxylic acid or its derivatives to construct the 4-chloro-pyrimido[4,5-b][1,4]benzodiazepine core. Subsequent nucleophilic substitution allows the introduction of one more diversity point in the target molecules. This strategy provides an efficient method to access a library of compounds based on privileged substructures that are of great interest in drug discovery.