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Updated: Jun 20, 2025

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Synthesis and reactivity of an N-heterocyclic carbene-stabilized diazoborane
Chonghe Zhang1, Christopher C Cummins1, Robert J Gilliard1
1Department of Chemistry, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Abstract:
Diazo compounds and organic azides are widely used as reagents for accessing valuable molecules in multiple areas of fundamental and applied chemistry. Their capacity to undergo versatile chemical transformations arises from the reactive nature of an incipient dinitrogen molecule at the terminal position. In this work, we report the synthesis and characterization of an N-heterocyclic carbene (NHC)-stabilized diazoborane-a boron-centered analog of organic azides and diazoalkanes. The diazoborane displays a strong tendency to release dinitrogen, thus serving as a borylene source, in analogy to organic azides and diazoalkanes serving as nitrene and carbene sources, respectively. Also reminiscent of diazoalkane and organic azide reactivity, the diazoborane serves as a 1,3-dipole that undergoes uncatalyzed [3+2] cycloaddition with an unactivated terminal alkyne, affording a five-membered heterocycle after a two-step rearrangement.
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