An efficient synthesis of indazoles from readily accessible E/Z mixtures of o‐haloaryl N‐tosylhydrazones has been developed. The thermo‐induced isomerization of N‐tosylhydrazones is discussed. A series of valuable indazole derivatives are prepared in good yields, and the method has been successfully applied to the synthesis of the bioactive compounds, lonidamine, AF‐2785, axitinib, YC‐1 and YD‐3.magnified image

The reactions of 1-sulfonyl-1H-indazoles under basic conditions are discussed, and the direct N-alkylation and Kemp elimination reactions of these compounds are reported. A series of 2-(p-tosylamino)benzonitriles and N-alkyl indazoles were prepared in good yields. Moreover, the 2-(p-tosylamino)benzonitriles could be transformed into a diverse range of important derivatives in a one-pot reaction. This method was successfully applied to the total syntheses of quindolinone and cryptolepinone; quindolinone was prepared in a one-pot reaction from 1-sulfonyl-1H-indazole.

The synthesis of indazoles from E/Z‐mixtures of o‐haloraryl‐N‐sulfonylhydrazones is reported.