Reduced 3,4′-bipyrazoles carrying thiophene and thiazole substituents: structures of two intermediates and two products

Chayanna Harish Chinthal, Hemmige S. Yathirajan, Nagaraja Manju, Balakrishna Kalluraya, Sabine Foro, Christopher Glidewell

Research output: Contribution to journalArticlepeer-review


Cyclo­addition reactions between 3-(5-ar­yloxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)-1-(thio­phen-2-yl)prop-2-en-1-ones and thio­semicarbazide leads to the formation of reduced 3,4′-bi­pyrazole-2-carbo­thio­amides. Further cyclo­addition of these inter­mediates with either diethyl acetyl­enedi­carboxyl­ate or 4-bromo­phenacyl bromide leads to reduced 3,4′-bi­pyrazoles carrying oxo­thia­zole or thia­zole substituents, respectively. The structures of two representative inter­mediates and two representative products established unambiguously the regiochemistry of the cyclo­addition reactions. The mol­ecules of 3′-methyl-5′-(2-methyl­phen­oxy)-1′-phenyl-5-(thio­phen-2-yl)-3,4-di­hydro-1′H,2H-3,4′-bi­pyra­zole-2-carbo­thio­amide, C25H23N5OS2 (Ia), are linked by N—H⋯N hydrogen bonds to form simple C(8) chains. The analogous compound 5′-(2,4-di­chloro­phen­oxy)-3′-methyl-1′-phenyl-5-(thio­phen-2-yl)-3,4-di­hydro-1′H,2H-3,4′-bi­pyra­zole-2-carbo­thio­amide hemihydrate crystallizes as a hemihydrate, C24H19Cl2N5OS2·0.5H2O (Ib), and the independent components are linked into a chain of spiro-fused R44(20) rings by a combination of O—H⋯N and N—H⋯O hydrogen bonds. In the structure of ethyl (Z)-2-{2-[3′-methyl-1′-phenyl-5-(thio­phen-2-yl)-5′-(2-methyl­phen­oxy)-3,4-di­hydro-1′H,2H-3,4′-bi­pyrazole-2-yl]-4-oxo-4,5-di­hydro­thia­zol-5-yl­idene}acetate, C31H27N5O4S2 (II), inversion-related pairs of mol­ecules are linked by paired C—H⋯π(arene) hydrogen bonds to form cyclic centrosymmetric dimers, but there are no direction-specific inter­molecular inter­actions in 4-(4-bromo­phen­yl)-2-[5′-(2,4-di­chloro­phen­oxy)-3′-methyl-1′-phenyl-5-(thio­phen-2-yl)-3,4-di­hydro-1′H,2H-3,4′-bi­pyrazole-2-yl]-4-thia­zole, C32H22BrCl2N5OS2 (III). Comparisons are made with the structures of some related compounds.
Original languageEnglish
Pages (from-to)335-340
Number of pages6
JournalActa Crystallographica Section E: Crystallographic Communications
Issue numberPart 4
Early online date5 Mar 2021
Publication statusPublished - Apr 2021


  • Heterocyclic compounds
  • Reduced bipyrazoles
  • Synthesis
  • Crystal structure
  • Regiochemistry
  • Hydrogen bonding
  • Supramolecular assembly


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