# Mild Generation of Highly Nucleophilic N‐Heterocyclic Carbene Boryl Anion From Neutral sp2–sp3 Diboron Reagents and Its Applications in Nucleophilic Borylation

## TL;DR

A highly reactive boryl anion is generated at room temperature and used to efficiently borylate a wide range of electrophiles.

## Contribution

A new method for generating a highly nucleophilic NHC boryl anion at room temperature using a neutral diboron reagent.

## Key findings

- The NHC boryl anion is generated in situ at room temperature using (NHC)BH2Bpin and KOtBu.
- The anion shows broad reactivity with diverse electrophiles, including traditionally inert ones.
- DFT calculations confirm the anion's nucleophilicity and reaction mechanisms.

## Abstract

Due to its high activity, the synthesis or generation of the N‐heterocyclic carbene (NHC) boryl anion remains challenging, with only limited methods available. Traditional stabilization through bulky ligands or aromatic systems restricts its reactivity as a boron synthon. In this work, we present a straightforward strategy for the in situ generation of an NHC boryl anion at room temperature through the reaction of neutral sp2–sp3 diboron reagent (NHC)BH2Bpin with KO
t
Bu. This less sterically hindered and strongly nucleophilic boryl anion demonstrates broad reactivity with diverse electrophiles, including those that are unreactive with other types of boryl anions or traditional diboron reagents. These nucleophilic borylation reactions enable the synthesis of a diverse array of four‐coordinate organoboron compounds. Detailed mechanistic studies and DFT calculations confirm the intermediacy of the NHC boryl anion and provide clear insights into the reaction pathways for the newly discovered reactivities.

A less hindered and highly nucleophilic N‐heterocyclic carbene (NHC) boryl anion is generated at room temperature by reacting sp2–sp3 diboron reagent (NHC)BH2Bpin with KO
t
Bu. This highly reactive anion demonstrates broad reactivity with various electrophiles, including those traditionally considered inert, enabling their efficient borylation. DFT calculations confirm the anion's high nucleophilicity and offer insights into reaction pathways.