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Making new molecules by adding carbons one at a time

Method allows for more select editing of complex molecules

by Leigh Krietsch Boerner
February 14, 2023


Scheme showing the addition of a single carbon from an N-heterocyclic carbene to make a lactam.
The newly formed lactam (right) gets its additional carbon from the N-heterocyclic carbene (center), while two hydrogens in the amide (left) shift over.

Chemists have increased their power to make a variety of compounds by figuring out how to add a single carbon to simple amides, creating four new C bonds in a single step. Mamoru Tobisu and coworkers at Osaka University used an N-heterocyclic carbene, a stable compound with two unpaired electrons at the C, to make a variety of cyclic amides called lactams with a variety of side groups (Science 2023, DOI: 10.1126/science.ade5110).

In the past, single carbon atoms have been too unstable to be useful in organic synthesis. In this method, the researchers gamed the system by using the carbene as a stable precursor to an atomic carbon, creating a more practical way to add just one C atom at a time. The group was initially working on a reaction that used the carbene as a catalyst but were surprised to find products that had one extra C, Tobisu says in an email.

One of the main goals of organic synthesis is to create complex molecules that can be useful—as drugs or in new materials, for example. Chemists need to do this as efficiently as possible, Tobisu says. This ability to add a single carbon in one step could potentially shorten synthetic processes to create more elaborate compounds.


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