150433-19-5Relevant articles and documents
Trinuclear diamagnetic nickel(II) complexes with bridging 3-arylpyrazolato ligands
Salih, Kifah S. M.,Bergner, Susann,Kelm, Harald,Sun, Yu,Gruen, Anneken,Schmitt, Yvonne,Schoch, Roland,Busch, Mark,Deibel, Naina,Braese, Stefan,Sarkar, Biprajit,Bauer, Matthias,Gerhards, Markus,Thiel, Werner R.
, p. 6049 - 6059 (2013)
Orange-red trinuclear nickel(II) complexes are obtained by reacting Ni(ClO4)2(H2O)6 with 3(5)-arylpyrazoles in the presence of a base. Herein, the diamagnetic nickel centers are coordinated in a square-pyramidal manner by four pyrazolato ligands, each of which bridges two nickel sites. The structurally unique complexes were investigated by NMR, IR, fluorescence, and X-ray spectroscopy. All seven compounds described here were structurally elucidated by single-crystal X-ray diffraction. With 3(5)-ferrocenylpyrazole as the substrate, a nonametallic system that possesses six redox-active ferrocenyl moieties was obtained. The reactions of Ni(ClO4)2(H2O)6 with 3(5)-arylpyrazoles in the presence of a base lead to pyrazolate-bridged trinuclear nickel(II) complexes. This strategy allows the introduction of a broad variety of aromatic substituents such as redox-active sites or additional phosphine donors in the periphery of the trinuclear core. Copyright
Selective palladium-catalyzed direct C-H arylation of unsubstituted N-protected pyrazoles
Kumpulainen, Esa T. T.,Pohjakallio, Antti
supporting information, p. 1555 - 1561 (2014/06/09)
A highly selective C-5 arylation of N-dimethylaminosulfamoyl-protected pyrazole with aryl bromides is catalyzed by 2-5 mol% palladium in the presence of triphenylphosphine ligand and carboxylic acid additive. Selectivities up to 45:1 (C-5:C-4) can be achieved by running the reaction in non-polar solvents. A thorough study of scope and limitations shows good general tolerance of aryl bromide substitution. However, limitations on tolerance of ortho-subsitution and protic functional groups were established. Together with a telescoped deprotection step this method presents a viable alternative for the synthesis of C-3 arylated pyrazole building blocks.
