Synthesis and properties of 5-ferrocenyl-1H-pyrazole-3-carbaldehydes

New ferrocene derivatives – ethyl esters of 1-aryl-5-ferrocenyl-1H-pyrazole-3-carboxylic acids were synthesized. The corresponding aldehydes were obtained from acid esters in two steps. The reductive amination reaction of 5-ferrocenyl-1-phenyl-1H-pyrazole-3-carbaldehyde was studied. Several of these compounds were investigated by cyclic voltammetry. All of them exhibited a reversible one-electron oxidation–reduction wave owing to the ferrocene–ferricinium redox couple with a positive shift (0.51–0.69 V) compared with that of ferrocene (0.46 V). The X-ray crystal structure of the ethyl ether 1-(3-chloro-2-fluorophenyl)-5-ferrocenyl-1H-pyrazole-3-carboxylic acid is also presented.

New ferrocene derivatives 5-ferrocenyl-1-aryl-3-pyrazolecarbaldehydes were synthesized. The reductive amination reaction of 5-ferrocenyl-1-phenyl-1H-pyrazole-3-carbaldehyde was studied. Compounds were investigated by cyclic voltammetry. All exhibited a reversible one-electron oxidation–reduction wave owing to the ferrocene–ferrocenium redox couple. The X-ray crystal structure of the ethyl 1-(3-chloro-2-fluorophenyl)-5-ferrocenyl-1H-pyrazole-3-carboxylate is also presented.Figure optionsDownload as PowerPoint slideHighlights
► New 5-ferrocenyl-1-aryl-3-pyrazolecarbaldehydes were synthesized.
► The reductive amination reaction of 5-ferrocenyl-1-phenyl-1H-pyrazole-3-carbaldehyde was studied.
► The X-ray crystal structure of the ethyl 1-(3-chloro-2-fluorophenyl)-5-ferrocenyl-1H-pyrazole-3-carboxylate is also presented.