Background: The pyrano[2,3-c]pyrazole derivatives are important building blocks
of many biologically active compounds owing to their diverse biological potential for
example, antiinflammatory, anticancer, antimicrobial and antioxidant properties.
Objective: Keeping in mind the wide range of applications of pyrano[2,3-c]pyrazoles, herein
we intended to develop a novel synthetic methodology for dihydropyranopyrazole. We were
also interested to check the influence of amino acids and dipeptides as catalyst on the
synthesis of pyrano[2,3-c]pyrazole derivatives.
Method: To achieve our objectives, we used a one-pot multi-component reaction of ethyl 3-
oxobutanoate, propanedinitrile, hydrazine monohydrate and several substituted
benzaldehydes by using different catalysts and solvents to synthesize our desired products in
the presence of various catalysts.
Results: We found that optimal conditions for the preparation of pyrano[2,3-c]pyrazoles were
L-cysteine (0.5 mol) in the presence of water:ethanol (9:1) at 90 oC. Various 1,4-
dihydropyrano[2,3-c]pyrazoles were afforded by using several substituted benzaldehydes in
Conclusion: We described a green and environmentally benign method to synthesize
pyrano[2,3-c]pyrazoles in a one-pot four component reaction of ethyl 3-oxobutanoate,
propanedinitrile, hydrazine monohydrate and different substituted benzaldehyde in the
presence of L-cysteine in aqueous ethanol (9:1) at 90 oC. Excellent yields of the products,
simple work-up, easily available starting materials, use of green solvents, naturally occurring
catalyst, non-toxicity, non-chromatographic purification and environmentally benign reaction
conditions are some main advantages of this protocol.