N-Heterocyclic Olefins of Pyrazole and Indazole.

Deprotonation of 3-methylpyrazolium and 3-methylindazolium salts yielded N-heterocyclic olefins (NHOs) in excellent yields, which reacted with isocyanates, halogens, and carbon disulfide. Calculated proton affinities are 261 kcal/mol (indazole NHOs) and 272 kcal/mol (pyrazole NHOs). The calculated pKa values are between 14.8 and 25.2, and bond lengths of the exocyclic double bond are slightly shorter than those of imidazole NHOs. As expected, the highest occupied molecular orbitals show significant atomic orbital coefficients at the exocyclic carbon atom.