Conversion of substituted 5-aryloxypyrazolecarbaldehydes into reduced 3,4'-bipyrazoles: synthesis and characterization, and the structures of four precursors and two products, and their supramolecular assembly in zero, one and two dimensions.

The reaction of 5-chloro-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde with phenols under basic conditions yields the corresponding 5-aryloxy derivatives; the subsequent reaction of these carbaldehydes with substituted acetophenones yields the corresponding chalcones, which in turn undergo cyclocondensation reactions with hydrazine in the presence of acetic acid to form N-acetylated reduced bipyrazoles. Structures are reported for three 5-aryloxycarbaldehydes and the 5-piperidino analogue, and for two reduced bipyrazole products. 5-(2-Chlorophenoxy)-3-methyl-1-phenyl-1H-pyrazole-4-carbaldehyde, C17H13ClN2O2, (II), which crystallizes with Z' = 2 in the space group P-1, exhibits orientational disorder of the carbaldehyde group in each of the two independent molecules. Each of 3-methyl-5-(4-nitrophenoxy)-1-phenyl-1H-pyrazole-4-carbaldehyde, C17H13N3O4, (IV), 3-methyl-5-(naphthalen-2-yloxy)-1-phenyl-1H-pyrazole-4-carbaldehyde, C21H16N2O2, (V), and 3-methyl-1-phenyl-5-(piperidin-1-yl)-1H-pyrazole-4-carbaldehyde, C16H19N3O, (VI), (3RS)-2-acetyl-5-(4-azidophenyl)-5'-(2-chlorophenoxy)-3'-methyl-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazole] C27H22ClN7O2, (IX) and (3RS)-2-acetyl-5-(4-azidophenyl)-3'-methyl-5'-(naphthalen-2-yloxy)-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazole] C31H25N7O2, (X), has Z' = 1, and each is fully ordered. The new compounds have all been fully characterized by analysis, namely IR spectroscopy, 1H and 13C NMR spectroscopy, and mass spectrometry. In each of (II), (V) and (IX), the molecules are linked into ribbons, generated respectively by combinations of C-H...N, C-H...π and C-Cl...π interactions in (II), C-H...O and C-H...π hydrogen bonds in (V), and C-H...N and C-H...O hydrogen bonds in (IX). The molecules of compounds (IV) and (IX) are both linked into sheets, by multiple C-H...O and C-H...π hydrogen bonds in (IV), and by two C-H...π hydrogen bonds in (IX). A single C-H...N hydrogen bond links the molecules of (X) into centrosymmetric dimers. Comparisons are made with the structures of some related compounds.