A rhodium-catalyzed cyclization of azobenzenes and vinylene carbonate via C−H bond activation to construct indazolo[2,3-a]quinolines has been developed. This protocol offers an efficient method for synthesis of the titled products in good yields with broad functional group tolerance. In this reaction, three C−C bonds and C−N bond are formed in one pot, and vinylene carbonate (VC) acts as C1 and C2 synthons as well as "vinylene transfer" agent and acylation reagent in the construction of targetfused heterocycles. Moreover, the products exhibit favorable fluorescence properties, which indicate their potential application as fluorescent materials and biosensors.

Dioxazolone has been attractive as an important synthon for a direct C−H amidation through a nitrene intermediate or Curtius rearrangement to form the isocyanate. However, the combination of two reaction models of dioxazolone has not been reported. Herein, a cobalt-catalyzed C−H and N−H functionalization of 1-arylpyrazolidinones with dioxazolones was developed. The dioxazolones acted as an amidated and carboxamidated reagent. Three C−N bonds were formed in a "one-pot" manner, which promoted the requirement of synthetic diversity.

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