ISSN 1070-4280, Russian Journal of Organic Chemistry, 2007, Vol. 43, No. 11, pp. 1698–1702. © Pleiades Publishing, Ltd., 2007. Original Russian Text © E.A. Nudnova, A.S. Potapov, A.I. Khlebnikov, V.D. Ogorodnikov, 2007, published in Zhurnal Organicheskoi Khimii, 2007, Vol. 43, No. 11, pp. 1698–1702. 1698 Synthesis of Ditopic Ligands Containing Bis(1H-pyrazol-1-yl)- methane Fragments E. A. Nudnova a , A. S. Potapov a , A. I. Khlebnikov a , and V. D. Ogorodnikov b a Polzunov Altai State Technical University, pr. Lenina 46, Barnaul, 656038 Russia e-mail: aikhl@nm.ru b Institute of Petroleum Chemistry, Siberian Division, Russian Academy of Sciences, Akademicheskii pr. 3, Tomsk, 634021 Russia Received January 5, 2007 Abstract—New approaches have been proposed for the synthesis of compounds containing two bis(1H-pyr- azol-1-yl)methane fragments. Nucleophilic replacement of the halogen atoms in appropriate tetrabromo deriv- atives by pyrazoles in the superbasic system KOH–DMSO gave ditopic chelating ligands: 1,1,2,2-tetrakis(1H- pyrazol-1-yl)ethane, 1,4-bis[bis(1H-pyrazol-1-yl)methyl]benzene, and 1,4-bis[bis(3,5-dimethyl-1H-pyrazol- 1-yl)methyl]benzene. 1,4-Bis[bis(1H-pyrazol-1-yl)methyl]benzene was also synthesized by reaction of 1H-pyr- azole with terephthalaldehyde in the presence of thionyl chloride. 1,1,2,2-Tetrakis(1H-pyrazol-1-yl)ethane was converted into the corresponding tetraiodo and tetranitro derivatives. Fig. 1. Schematic representation of ditopic ligands contain- ing bis(1H-pyrazol-1-yl)methane fragments. Bis(1H-pyrazol-1-yl)alkanes are used as chelating ligands in coordination compounds with various metals [1]. Among these, specific interest is attracted by com- pounds whose molecules contain several bis(1H-pyra- zol-1-yl)methane fragments (Fig. 1) connected through various linkers; such derivatives are multitopic chelat- ing ligands. Ditopic ligands could give rise to homo- and heterobimetallic complexes exhibiting high cata- lytic and biological activity, as well as to coordination polymers [2, 3]. Supramolecular structure of such polymers may be varied by changing the linker nature; as a result, new materials, ion exchangers, molecular sieves, and sensors may be obtained [4–6]. The known synthetic approaches to ditopic pyra- zole-containing ligands involve the use of unstable compounds, high temperatures, and thoroughly dehy- drated solvents [4–6]. One of these is based on reaction of appropriate heterocyclic systems with dialdehyde acetals in the presence of a catalytic amount of p-tolu- enesulfonic acid. For example, prolonged heating of a mixture of malonaldehyde tetramethyl acetal and pyrazole in acid medium with continuous removal of the liberated methanol by distillation gave 1,1,3,3-tetra- (1H-pyrazol-1-yl)propane. Compounds with a longer linker, 1,1,4,4-tetra(1 H-pyrazol-1-yl)butane and 1,1,5,5-tetra(1H-pyrazol-1-yl)pentane, were synthe- sized in a similar way [5]. Disadvantages of this proce- dure are low stability of the initial acetals and long reaction time. Compounds containing two bis(1H-pyr- azol-1-yl)methane fragments are also formed by reac- tions of carbonyl- and sulfinyldipyrazoles (prelimi- narily prepared from pyrazole potassium salt and phos- gene or thionyl chloride) with various aldehydes in the presence of anhydrous cobalt(II) chloride [2, 6]. This procedure ensures high yields of the target ligands but involves some experimental difficulties related to the necessity of using alkali metals and phosgene. We can conclude that search for new methods of synthesis of compounds having two bis(1H-pyrazol-1-yl)methane fragments is quite important. In the present article we propose two new synthetic approaches to the above compounds. One of these is based on the reaction of the corresponding pyrazoles DOI: 10.1134/S1070428007110188 N N N N R R N N N N R R Linker