A facile synthesis of 2-methyl-1,4-benzodiazepin-5-ones via intramolecular azide cycloaddition

It is well known that a large array of pharmaceuticals contain the 1,4-benzodiazepine skeleton. A number of them are 1,4-benzodiazepin-5-ones, e.g. the antibiotic neothramycin, the antidepressant flumazenil, and the antihistaminic clobenzepam(1-5). The literature on this subject, although very copious, is mainly constituted by patents. Therefore, both new synthetic methods and new representatives of this class of compounds are valuable targets. This paper describes a facile and general synthesis of 2-methyl-1,4-benzodiazepin-5-ones based on an intramolecular azide cycloaddition.