# N‑Heterocyclic Olefins of Pyrazole and Indazole

## TL;DR

Scientists synthesized new N-heterocyclic olefins from pyrazole and indazole compounds and studied their reactivity and properties.

## Contribution

The synthesis and characterization of N-heterocyclic olefins from pyrazole and indazole salts with high yields and detailed computational analysis.

## Key findings

- N-heterocyclic olefins were synthesized in excellent yields from 3-methylpyrazolium and 3-methylindazolium salts.
- Proton affinities of indazole and pyrazole NHOs were calculated as 261 and 272 kcal/mol, respectively.
- Exocyclic double bond lengths in these NHOs are shorter than those in imidazole NHOs.

## Abstract

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 pK
a 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.