Synthesis of fluorinated dipyrazolyl sulfones from bis(2-fluoro-2-polyfluoroalkylalkenyl) sulfones and diazomethane
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Synthesis of fluorinated dipyrazolyl sulfones from bis(2-fluoro-2-polyfluoroalkylalkenyl) sulfones and diazomethane Yaroslav S. Borodkin1, Eduard B. Rusanov1, Aleksandr I. Khizhan2,3, Yurii G. Shermolovich1* 1
Institute of Organic Chemistry, National Academy of Sciences of Ukraine, 5 Murmanska St., Kyiv 02660, Ukraine; е-mail: [email protected] 2 Enamine Ltd., 78 Chervonotkatska St., Kyiv 02094, Ukraine; e-mail: [email protected] 3 L. M. Litvinenko Institute of Physical-Organic Chemistry and Coal Chemistry, National Academy of Sciences of Ukraine 50 Kharkiv Shosse, Kyiv 02160, Ukraine Submitted May 30, 2019 Accepted July 8, 2019
Translated from Khimiya Geterotsiklicheskikh Soedinenii, 2019, 55(11), 1065–1069
The reactions of diazomethane with bis(2-fluoro-2-polyfluoroalkylalkenyl) sulfones are accompanied by dehydrofluorination and lead to the formation of new dipyrazolyl sulfones containing polyfluoroalkyl substituents at position 4 of the pyrazole ring. The structure of four new sulfones was confirmed by X-ray diffraction analysis. Keywords: diazomethane, divinyl sulfides, fluorinated divinyl sulfones, 1-methyl-4-polyfluoroalkylpyrazoles, dehydrofluorination.
Recently, we reported the synthesis of new types of fluorine-containing divinyl sulfides 1 and sulfones 2 containing a CH=CF(AlkF) fragment1 (Scheme 1). Scheme 1
The presence of two vinyl fragments containing an activated C=C double bond in the molecules of sulfides and sulfones suggests that these compounds can be used for accessing of various bisheterocycles. For the synthesis of these compounds, for example, cycloaddition reactions of divinyl sulfones with 1,3-dipoles of various nature can be used. It should be noted that the development of methods for the synthesis of methylene derivatives of bisheterocycles has recently received quite a lot of attention due to 0009-3122/19/55(11)-1065©2019 Springer Science+Business Media, LLC
the possibility of their use as ligands for the preparation of organometallic catalysts.2 Much less is known about compounds containing two heterocyclic fragments bonded by a sulfur atom with different valencies. The synthesis of the first dipyrazolyl sulfides and sulfones was reported in publications from the middle of the last century.3 Considering the fact that much attention has been paid to the study of the synthesis methods, chemical and biological properties of fluorine-containing pyrazoles,4 in this paper we investigated the reactions of fluorinated divinyl sulfones 2 with diazomethane. We found that divinyl sulfones 2 react with diazomethane in CH2Cl2 at room temperature to form a mixture of isomeric N-methylpyrazoles 3 and 4, which differ in the arrangement of methyl groups at the nitrogen atoms (Scheme 2). In the case of all three investigated divinyl sulfones 2a–c, the formation of symmetric dipyrazoles 3a–c predominates. According to 19F NMR spectroscopy of the reaction mixtures, the ratio of isomeric products is 1:0.5 (compounds 3, 4a), 1:0.7 (compounds 3, 4b), and 1:0.6 (compounds 3, 4c). It is necessary to use
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