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, CHClNO, (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, CHNO, (IV), 3-methyl-5-(naphthalen-2-yloxy)-1-phenyl-1H-pyrazole-4-carbaldehyde, CHNO, (V), and 3-methyl-1-phenyl-5-(piperidin-1-yl)-1H-pyrazole-4-carbaldehyde, CHNO, (VI), (3RS)-2-acetyl-5-(4-azidophenyl)-5'-(2-chlorophenoxy)-3'-methyl-1'-phenyl-3,4-dihydro-1'H,2H-[3,4'-bipyrazole] CHClNO, (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] CHNO, (X), has Z' = 1, and each is fully ordered. The new compounds have all been fully characterized by analysis, namely IR spectroscopy, H and C 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.