# Characterization of a Silver Vinylcarbene Intermediate in Carbene–Alkyne Metathesis and Its Concerted C(sp2)–H Bond Insertion

## TL;DR

This study reveals a new mechanism in a chemical reaction involving silver and carbon compounds, showing a direct bond formation process.

## Contribution

The paper introduces a novel, concerted mechanism for C(sp2)-H bond insertion in carbene-alkyne metathesis.

## Key findings

- Silver vinylcarbenes play a key role in the carbene-alkyne metathesis reaction.
- The C(sp2)-H insertion occurs via a concerted mechanism, not a stepwise one.
- The substitution pattern significantly influences the reaction mechanism.

## Abstract

Herein we present compelling evidence of the intervention
of electrophilic
silver vinylcarbenes in the carbene-alkyne metathesis (CAM) reaction,
leading to a pivotal C­(sp2)-H insertion process. The delicate
equilibrium between the stability and reactivity of transient species
is crucial for efficient detection. Through meticulous mechanistic
exploration, we unveil that the mechanism for the C­(sp2)-H insertion hinges on the substitution pattern. Indeed, it departs
from the previously documented stepwise mechanism (involving Wheland
intermediates), and it follows a concerted route, quite uncommon for
this transformation.