Aryl radical-mediated N-heterocyclic carbene catalysis

Transition-metal-free transformations

23 December 2021

A radical organocatalytic approach to assembling complex organic molecules that contain an aromatic ring has been developed.

High-value organic molecules — from pharmaceuticals to flavour and fragrance compounds — commonly have an aromatic ‘aryl’ ring in their structure. Aryl groups have typically been incorporated into complex organic structures via a transition-metal-catalysed reaction of aryl halides. However, more-sustainable metal-free reaction conditions are being sought.

Reactions based on free radicals are sparking growing interest as a potentially clean and efficient way to assemble organic molecules.

Now, seven researchers, all at Kanazawa University in Japan, have shown that organocatalysts such as N-heterocyclic carbenes (NHCs) offer a transition-metal-free method to drive radical-based synthesis.

The team developed an NHC-catalysed, radical-based method for aryl halides to produce aryl-containing structures. Their discovery expands the scope of radical-based NHC organocatalysis.

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