Heteropoly Acids an Efficient Catalyst for Ultrasound Promoted Synthesis of Substituted Indazole

A clean and simple methodology was developed for the synthesis of substituted indazoles using heteropoly acids containing tungsten, molybdenum metal catalyzed condensation reaction between substituted 2-hydroxy benzaldehydes/acetophenones and hydrazine hydrate/phenyl hydrazine. The reaction conditions are optimized for two different heteropoly acids such as H3PMo12O40 and H3PW12O40 using conventional and ultrasound sonication method. Yield of the products improved to 92 to 95% using H3PW12O40 heteropoly acid as catalyst which is reusable, cost effective and easy to handle.