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'Ester Dance Reaction' Yields Low-cost Aromatic Esters

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Scientists in Japan have developed a novel, practical catalytic reaction, called the 'ester dance reaction,' that reportedly yields high amounts of aromatic esters from low-cost starting materials. Their work recently was published in Science Advances.

According to the authors, aromatic esters are commonly used as feedstock in the chemical industry. However, high costs, low product yields and harsh reaction conditions impede the production of pure-form aromatic esters. As such, researchers from Waseda University, Japan, led by Junichiro Yamaguchi, Ph.D., sought to identify efficient reactions for their synthesis.

Finding Inspiration

The scientists derived their inspiration from another reaction—the halogen dance reaction—wherein a halogen substituent is translocated to another carbon atom on the aromatic ring. According to the researchers, it not easy to make an ester group change its position from one ring carbon to another under mild conditions but previous experiments revealed it was possible.

Yamaguchi explained, “During our recent efforts in the development of decarbonylative transformations of aromatic esters, we unexpectedly discovered an aromatic compound with ester translocated from one carbon to another carbon. After optimizing conditions, we were able to develop a new reaction, which we discovered by chance.”

Catalyst as Key

The key to developing this reaction was a palladium catalyst consisting of an easy-to-handle diphosphine ligand called dcypt, developed by the scientists. When the scientists tested this new catalyst, they were surprised by the reaction, which resulted in the ester group successfully being translocated on the aromatic ring. The researchers named the process the "ester dance reaction," owing to the ability of ester groups to "dance" around the aromatic ring.

Speaking of the achievement, Yamaguchi said, “In one of our experiments involving transformations of aromatic esters, we found that our homemade catalyst can enable a difficult conversion reaction. This was an exciting new discovery.’’

Optimizing Yield for Sustainable Production

Experiments were conducted to optimize the appropriate concentrations of the palladium salt and chemical reagent potassium carbonate and under optimal conditions, produced a yield as high as 85%. Having optimized the reaction, the scientists explored the new ester dance reaction in other aromatic substances, such as phenyl benzoates, heteroarenes and other aromatics. They found that combining this reaction with other ester-transforming reactions, such as arylation, amination and etherification, produced compounds with an array of different substitution patterns.

With the novel catalyst and the optimized catalytic reaction, the researchers believe that synthesizing aromatic compounds sustainably can now become easier. Yamaguchi concluded, “We believe that our unconventional yet predictable approach of using the ester dance reaction will help organic chemists synthesize aromatic compounds that are usually difficult and expensive to create."

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