Abstract

A clean and straightforward methodology developed for the synthesis of substituted indazoles using silica supported polyphosphoric acid
(PPA-SiO2) catalyzed condensation reaction between substituted 2-hydroxybenzaldehydes or acetophenones and hydrazine hydrate or
phenylhydrazine. The reaction conditions are optimized for different solvents at different temperatures. The yield of the products improved
to 88 to 90 % using silica supported polyphosphoric acid as a catalyst, which is reusable, cost-effective and straightforward to synthesize.

Key words: silica supported polyphosphoric acid; hydrazine hydrate; phenyl hydrazine; o-hydroxyacetophenones; indazole.