A Convenient Synthesis of 1-Aryl- and 2-Aryl-Substituted Indazolones via Intramolecular C–N Coupling Promoted by KOt-Bu

A new method for the synthesis of 1-arylindazolones and 2-arylindazolones from N′-aryl-2-halobenzohydrazides promoted by KOt-Bu was developed. The difference of 2-halogen substituent exerted a significant effect on the distribution of the products. Two distinct reaction pathways are proposed for the generation of 1-arylindazolones and 2-arylindazolones, respectively.