Construction of Multifunctionalized Azopyrazoles by Silver‐ Catalyzed Cascade Reaction of Diazo Compounds

Abstract A variety of multisubstituted azopyrazoles were synthesized in good yield from an efficient one‐pot silver trifluoromethanesulfonate (AgOTf)‐catalyzed cascade reaction of α‐diazo‐β‐keto esters with two arylhydrazines or two arylhydrazine hydrochlorides. This cascade reaction included pyrazolone formation, NH insertion, and oxidation. For the synthesis of more diverse azopyrazoles bearing two different aromatic rings, the silver(I)‐catalyzed cascade reaction of 4‐diazopyrazol‐3‐one with arylhydrazine hydrochlorides was also developed. The advantages of these methodologies are easy handling, mild reaction conditions, and an effective and non‐toxic catalyst usage. magnified image