Figure 1: Benzene (depicted here) is the most well-known example of an arene. RIKEN researchers have found a new way to add a boron-containing group into an arene. © RUSLANAS BARANAUSKAS/SCIENCE PHOTO LIBRARY
RIKEN chemists have demonstrated a new way to synthesize organic compounds that contain the element boron1. Such compounds are used in drugs and as important stepping stones in organic synthesis.
Organoboron compounds are used in a wide range of drugs, including those for treating cancer, fungal infections and eczema. They are also employed as intermediates in reactions to produce even more drugs. Furthermore, they are used in light-emitting materials and organic semiconductors.
The simplest way to synthesize aromatic organoboron compounds is the direct introduction of a boron-containing group into an arene-a molecule made up of carbon and hydrogen and that contains at least one aromatic ring.
The usual way to do that is to activate a carbon-hydrogen bond using a transition metal as a catalyst. But these reactions often require special arenes and complex catalysts.
Now, Yuichiro Mutoh and Laurean Ilies, both of the RIKEN Center for Sustainable Resource Science, and co-workers have found an alternative strategy for adding boron to an arene. It involves the temporary activation of an arene through π-coordination.
"By using a metal precursor designed to interact with the π electrons of an arene, we can activate the arene toward an organic transformation without employing any complex metal catalysts," explains Ilies.
The team hit on the strategy after encountering several challenges during previous work. "We've been working on the design of catalysts that can recognize an organic molecule through weak noncovalent interactions," says Ilies.
During this work, the team found that synthesizing catalysts could be tedious. They also discovered that recognizing π electrons of an aromatic molecule through non-covalent interactions was difficult because they are weak. The π-coordination strategy overcomes both problems.
The team initially did experiments using a metal catalysis. But to their surprise they found that the reaction proceeded even when there was no catalyst.
"We realized that there was no need for a catalyst when a base is present," says Ilies. "Further investigations suggested that a borate species attacks the arene activated through π-coordination."
A team seminar sparked the idea. "Interestingly, the initial idea came during a study seminar," says Ilies. "Each month, a team member chooses a topic from an organometallic chemistry textbook and presents it to the team. During one such seminar, one member presented about π-coordination complexes, and that's when the idea of transient π-coordination of arene substrates was born."
Publishing the paper was "a long battle" involving "four revisions and many additional experiments to convince the reviewers," recalls Ilies. But the hard work was worth it. "While revising the paper, we obtained a very unexpected result that we were so surprised and excited about. We're researching the details now."
Yuichiro Mutoh (first row, second from right), Laurean Ilies (first row, third from left), Sobi Asako (first row, first from left), Relam Khalaf (first row, second from left) and co-workers have found that nucleophilic borylation of simple arenes is enabled by transient π-coordination. © 2026 RIKEN
