Catalyst-free green synthesis of dihydropyrano[2,3-c]pyrazole scaffolds assisted by ethylene glycol (E-G) as a reusable and biodegradable solvent medium


We revealed a catalyst-free, green and rapid one-pot four-component tandem strategy for the preparation of dihydropyrano[2,3-c]pyrazoles – a biologically significant scaffold – via Knoevenagel-Michael cyclocondensation based on green chemistry principles. Highlights of the current practice are the application of non-hazardous reaction circumstances, catalyst-free, operational simplicity, use of inexpensive initiating substances, isolation of pure product via easy filtration thus preventing the requirement for column chromatography, metal-free, excellent yields, time-saving aspects of the reaction. However, the green ethylene glycol (E-G) can be recycled at least six times with no considerable reduction in activity making it greatly advantageous in addressing the industrial requirements and environmental worries.

Graphic Abstract

The catalyst-free and environmentally friendly synthesis of dihydropyrano[2,3-c]pyrazole scaffolds are reported via ethylene glycol (E-G) as a green, reusable and biodegradable promoting media via tandem Knoevenagel-Michael cyclocondensation reaction of ethyl acetoacetate, hydrazine hydrate/phenylhydrazine, aromatic/aliphatic aldehydes and malononitrile provided the anticipated products in outstanding yields and short reaction times which might solve some cost problems in industry

This is a preview of subscription content, access via your institution.

Figure 1
Scheme 1
Figure 2
Scheme 2


  1. 1.

    Ibad A, Waseem M A, Ibad F, Ansari K, Lone A M, Watal G and Siddiqui I R 2017 A Green Access to Tetrahydro‐1H‐pyrano [2, 3‐d] pyrimidines: Visible‐Light‐Triggered and Ethylene‐Glycol‐Mediated Multicomponent One‐Pot Process Chem. Select. 2 4587

    CAS  Google Scholar 

  2. 2.

    Chauhan P, Mahajan S and Enders D 2015 Asymmetric synthesis of pyrazoles and pyrazolones employing the reactivity of pyrazolin-5-one derivatives Chem. Commun. 51 12890

    CAS  Google Scholar 

  3. 3.

    (a) Junek H and Aigner H 1973 Synthesen mit Nitrilen, XXXV. Reaktionen von tetracyanäthylen mit heterocyclen Chem. Ber. 106 914; (b) Wamhoff H, Kroth E and Strauch K 1993 Dihalogentriphenylphosphorane in der Heterocyclensynthese; 271: Heterokondensierte 1, 2, 4-Triazolo [1, 5-c] pyrimidine aus Enaminonitrilen via O-Ethylformimide Synthesis 11 1129

  4. 4.

    Foloppe N, Fisher L M, Howes R, Potter A, Robertson A G and Surgenor A E 2006 Identification of chemically diverse Chk1 inhibitors by receptor-based virtual screening Bioorg. Med. Chem. 14 4792

    CAS  Google Scholar 

  5. 5.

    (a) Wang J L, Liu D, Zheng Z J, Shan S, Han X, Srinivasula S M, Croce C M, Alnemri E S and Huang Z 2000 Structure-based discovery of an organic compound that binds Bcl-2 protein and induces apoptosis of tumor cells Proc. Natl. Acad. Sci. 97 7124; (b) Kuo C, Huang J and Nakamura H 1984 Studies on heterocyclic compounds. 6. Synthesis and analgesic and antiinflammatory activities of 3, 4-dimethylpyrano [2, 3-c] pyrazol-6-one derivatives Med. Chem. 27 539

  6. 6.

    Abdelrazek F M, Metz P, Kataeva O, Jaeger A and El-Mahrouky S F 2007 Synthesis and Molluscicidal Activity of New Chromene and Pyrano[2,3‐c]pyrazole Derivatives Arch. Pharm. 340 543

    CAS  Google Scholar 

  7. 7.

    El-Tamany E S, El-Shahed F A and Mohamed B H 1999 Synthesis and bilogical activity of some pyrazole derivatives J. Serb. Chem. Soc. 64 9

    CAS  Google Scholar 

  8. 8.

    Saha A, Payra S and Banerjee S 2015 One-pot multicomponent synthesis of highly functionalized bio-active pyrano[2,3-c]pyrazole and benzylpyrazolyl coumarin derivatives using ZrO2 nanoparticles as a reusable catalyst Green Chem. 17 2859

  9. 9.

    Moshtaghi Zonouz A and Moghani D 2016 Green and highly efficient synthesis of pyranopyrazoles in choline chloride/urea deep eutectic solvent Synth. Commun. 46 220

    CAS  Google Scholar 

  10. 10.

    Zolfigol M A, Tavasoli M, Moosavi-Zare A R, Moosavi P, Grehardus Kruger H, Shiri M and Khakyzadeh V 2013 Synthesis of pyranopyrazoles using isonicotinic acid as a dual and biological organocatalyst RSC Adv. 3 25681

    CAS  Google Scholar 

  11. 11.

    Gujar J B, Chaudhari M A, Kawade D S and Shingara M S 2014 Molecular sieves: an efficient and reusable catalyst for multi-component synthesis of dihydropyrano [2, 3-c] pyrazole derivatives Tetrahedron Lett. 55 6030

  12. 12.

    Guo R Y, An Z M, Mo L P, Yang S T, Liu H X and Wang S X 2013 Meglumine promoted one-pot, four-component synthesis of pyranopyrazole derivatives Tetrahedron 69 9931

  13. 13.

    Tamaddon F and Alizadeh M A 2014 A four-component synthesis of dihydropyrano [2, 3-c] pyrazoles in a new water-based worm-like micellar medium Tetrahedron Lett. 55 3588

  14. 14.

    Mecadon H, Rohman M R, Kharbangar I, Laloo B M, Kharkongor I, Rajbangshi M and Myrboh B 2011 l-Proline as an efficicent catalyst for the multi-component synthesis of 6-amino-4-alkyl/aryl-3-methyl-2,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles in water Tetrahedron Lett. 52 3228

  15. 15.

    Wu M, Feng Q, Wan D and Ma J 2013 CTACl as catalyst for four-component, one-pot synthesis of pyranopyrazole derivatives in aqueous medium Synth. Commun. 43 1721

    CAS  Google Scholar 

  16. 16.

    Bora P P, Bihani M and Bez G 2013 Multicomponent synthesis of dihydropyrano [2, 3-c] pyrazoles catalyzed by lipase from Aspergillus niger J Mol. Catal. B 92 24

    CAS  Article  Google Scholar 

  17. 17.

    Dalal K S, Tayade Y A, Wagh Y B, Trivedi D R, Dalal D S and Chaudhari B L 2016 Bovine serum albumin catalyzed one-pot, three-component synthesis of dihydropyrano [2, 3-c] pyrazole derivatives in aqueous ethanol RSC Adv. 6 14868

  18. 18.

    Tayade Y A, Padvi S A, Wagh Y B and Dalal D S 2015 β-Cyclodextrin as a supramolecular catalyst for the synthesis of dihydropyrano [2, 3-c] pyrazole and spiro [indoline-3, 4′-pyrano [2, 3-c] pyrazole] in aqueous medium Tetrahedron Lett. 56 2441

  19. 19.

    Zhou C F, Li J J and Su W K 2016 Morpholine triflate promoted one-pot, four-component synthesis of dihydropyrano [2, 3-c] pyrazoles Chin. Chem. Lett. 27 1686

    CAS  Google Scholar 

  20. 20.

    Yarie M, Zolfigol M A, Baghery S, Alonso D A, Khoshnood A, Bayat Y and Asgar A 2018 Triphenyl (3-sulfopropyl) phosphonium trinitromethanide as a novel nanosized molten salt: Catalytic activity at the preparation of dihydropyrano [2, 3-c] pyrazoles J. Mol. Liq. 271 872

    CAS  Article  Google Scholar 

  21. 21.

    Liu T, Lai Y H, Yu Y Q and Xu D Z 2018 A facile and efficient procedure for one-pot four-component synthesis of polysubstituted spiro pyrano[2,3-c]pyrazole and spiro 1,4-dihydropyridine catalyzed by a Dabco-based ionic liquid under mild conditions New. J. Chem. 42 1046

    CAS  Google Scholar 

  22. 22.

    Ghorbani-Vaghei R, Mahmoodi J, Shahriari A and Maghbooli Y 2017 Synthesis of pyrano[2,3‐c]pyrazole derivatives using Fe3O4@SiO2@piperidinium benzene‐1,3‐disulfonate (Fe3O4@SiO2 nanoparticle‐supported IL) as a novel, green and heterogeneous catalyst Appl. Organomet. Chem. 31 e3816

    Article  Google Scholar 

  23. 23.

    Kiyani H and Bamdad M 2018 Sodium ascorbate as an expedient catalyst for green synthesis of polysubstituted 5-aminopyrazole-4-carbonitriles and 6-amino-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles Res. Chem. Intermed. 44 2761

    CAS  Article  Google Scholar 

  24. 24.

    Salehi N and Mirjalili F B B 2018 Green Synthesis of Pyrano[2,3-c]pyrazoles and Spiro[indoline-3,4′-pyrano[2,3-c]pyrazoles] Using Nano-silica Supported 1,4-Diazabicyclo[2.2.2]octane as a Novel Catalyst Org. Prep. Proced. Int. 50 578

  25. 25.

    Konakanchi R, Gondru R, Bharat Nishtala V and Reddy Kotha L NaF-catalyzed efficient one-pot synthesis of dihydropyrano[2,3-c]pyrazoles under ultrasonic irradiation via MCR approach 2018 Synth. Commun. 48 1994

  26. 26.

    Patel K G, Misra N M, Vekariya R H and Shettigar R R 2018 One-pot multicomponent synthesis in aqueous medium of 1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitrile and derivatives using a green and reusable nano-SiO2 catalyst from agricultural waste Res. Chem. Intermed. 44 289

    CAS  Article  Google Scholar 

  27. 27.

    Mohamadpour F 2019 Synthesis of Pyran-Annulated Heterocyclic Systems Catalyzed by Theophylline as a Green and Bio-Based Catalyst Polycycl. Aromat. Comp. doi:

    Google Scholar 

  28. 28.

    Zolfigol M A, Afsharnadery F, Baghery S, Salehzadeh S and Maleki F 2015 Catalytic applications of {[HMIM]C(NO2)3}: as a nano ionic liquid for the synthesis of pyrazole derivatives under green conditions and a mechanistic investigation with a new approach RSC Adv. 5 75555

  29. 29.

    Mohamadpour F and Lashkari M 2018 Three-component reaction of β-keto esters, aromatic aldehydes and urea/thiourea promoted by caffeine: A green and natural, biodegradable catalyst for eco-safe Biginelli synthesis of 3,4-dihydropyrimidin-2-(1H)-ones/tiones derivatives under solvent-free conditions J. Serb. Chem. Soc. 83 673

    CAS  Article  Google Scholar 

  30. 30.

    Mohamadpour F 2018 Green and Convenient One-Pot Access to Polyfunctionalized Piperidine Scaffolds via Glutamic Acid Catalyzed Knoevenagel- Intramolecular [4+2] aza-Diels-Alder Imin-Based Multi-Component Reaction Under Ambient Temperature Polycycl. Aromat. Comp. doi:

    Google Scholar 

  31. 31.

    Mohamadpour F 2019 Glutamic acid as green and bio-based α-amino acid catalyst promoted one-pot access to polyfunctionalized dihydro-2-oxypyrroles J. Serb. Chem. Soc. 84 1083

    CAS  Article  Google Scholar 

  32. 32.

    Mohamadpour F 2019 Theophylline as a Green Catalyst for the Synthesis of 1H-Pyrazolo[1,2-b]phthalazine-5,10-dione Org. Prep. Proced. Int. doi:

    Google Scholar 

Download references


We gratefully acknowledge the financial support from the Research Council of the Apadana Institute of Higher Education.

Author information



Corresponding author

Correspondence to Farzaneh Mohamadpour.

Electronic supplementary material

Below is the link to the electronic supplementary material.

Supplementary material 1 (PDF 501 kb)

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Mohamadpour, F. Catalyst-free green synthesis of dihydropyrano[2,3-c]pyrazole scaffolds assisted by ethylene glycol (E-G) as a reusable and biodegradable solvent medium. J Chem Sci 132, 72 (2020).

Download citation


  • Catalyst-free
  • ethylene glycol (E-G)
  • green protocol
  • reusable solvent medium
  • dihydropyrano[2,3-c]pyrazoles