A versatile protocol for the synthesis of pyrazolyl-substituted pyridinium and guanidinium salts from pyridone and urea derivatives.

Antje K. C. Echterhoff, Sivathmeehan Yogendra, Jutta Koesters, Roland Fischer, Jan J. Weigand

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The trication I was used as a convenient pyrazolyl-transfer reactant to convert 2-pyridone, 4-pyridone and urea derivs. such as benzimidazol-2-one and theobromine to their pyrazolyl substituted triflate salts, e.g., II. The conversion represented a new, efficient and highly functional group-compatible approach that yielded the desired products conveniently and in high yields. Typically the reaction proceeded via exchange of carbonyl oxygen atom of the substrate for pyrazolyl moiety. However, for the structurally related 3-hydroxypyridines, a different reaction pathway occurred giving tripyridyl phosphites, e.g., III which was explained by the lactam-lactim tautomerism of the substrate. The structural arrangements of most of the products were confirmed by X-ray crystallog. anal. [on SciFinder(R)]
Original languageEnglish
Pages (from-to)7631-7642
Number of pages12
JournalEuropean Journal of Organic Chemistry
Issue number34
Publication statusPublished - 2014

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