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

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)]