Access to a Novel Class of Tetracyclic 1,4‐Benzodiazepin‐5‐ones Starting from α‐Amino Acids by Pd‐Catalyzed Amination/1,3‐Dipolar Cycloaddition as the Key Steps

A convenient procedure for the preparation of the novel class of tetracyclic imidazo[2,1‐ c ]pyrazolo[1,5‐ a ][1,4]benzodiazepine‐5,8‐diones is reported. The protocol uses cheap andeasily accessible α‐amino acids as chiral‐pool starting materials and leads to products in an enantiopure form. An intramolecular palladium‐catalyzed amination process to form the imidazole nucleus and an intramolecular 1,3‐dipolar cycloaddition reaction to simultaneously achieve the pyrazole and 1,4‐diazepine rings are the key steps.