Starch-sulfuric acid (SSA) as a bio-degradable and recyclable solid acid catalyst for one-pot synthesis of 6-amino-1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitriles

Starch-sulfuric acid (SSA) catalyzed, one-pot, multi-component and an environmentally benign synthesis of 6-amino-1,4-dihydropyrano[2,3-c]-pyrazole-5-carbonitrile derivatives has been achieved by reaction of ethyl acetoacetate, hydrazine hydrate, aryl aldehydes and malononitrile under solvent-free conditions. Upon completion of the reaction, the SSA could be recycled and reused several times with consistent catalytic efficiency. This protocol has several advantages including high yields, simple work-up process, avoiding the use of organic solvents, short reaction times, and use of an inexpensive and mild catalyst.