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

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.