Japanese chemists have found aromatic esters as an alternative coupling partner for boronic acids, to produce useful compounds for pharmaceuticals, agrochemicals and organic materials.

The study was conducted by scientists from the Institute of Transformative Bio-Molecules (ITbM), Nagoya University and the NSF Center for Selective C-H Functionalization (NSF-CCHF) at Emory University.

The carbon-carbon bond forming reaction earlier used a palladium catalyst to couple boronic acids with organic halides. Scientists have been working to identify an alternate coupling partner for boronic acids as this reaction can generate corrosive waste by-products. 

The team has expanded the scope of a cross-coupling reaction, the Suzuki-Miyaura, by using aromatic esters with boronic acids in presence of nickel catalyst.

Esters are carbonyl compounds that are primarily found in fats and oils, and are used as ingredients in perfumes.

The team said that the high-synthetic accessibility of esters expands the availability of substrates for the reaction.

As part of the study, scientists have found that a catalytic amount of nickel acetate with sodium carbonate as a base is effective to obtain desired decarbonylative products in good yield, while a range of aromatic ester substrates was also compatible in the reaction.

Emory University Professor Djamaladdin Musaev conducted theoretical calculations to the mechanism of the decarbonylative cross-coupling reaction between aromatic esters and boronic acids.

Musaev said: "This is a beautiful work in the frontier of organic transformations, and establishes a novel, relatively inexpensive and environmentally friendly synthetic strategy for carbon-carbon bond formation.

"The accompanied computational efforts revealed key mechanistic details of this novel reaction."

The team expects the reaction method to facilitate development of industrial processes to produce biologically and structurally active compounds in the future.

Image: A nickel catalyst triggers the cross-coupling reaction between aromatic esters and boronic acids. Photo: courtesy of Institute of Transformative Bio-Molecules Nagoya University.