Aluminum hydrogen sulfate as a green catalyst for the solvent-free synthesis of pyrazolopyridines

Aluminum hydrogen sulfate turned out to be a mild, convenient, and efficient reagent for the conversion of substituted benzyl alcohols into pyrazolopyridines via condensation with 3-methyl-1 H -pyrazole-5-amine and CH acid (malononitrile or indan-1,3-dione) at room temperature under solvent-free conditions with high yield, high purity, and short reaction time.