Arylboronates made easy
Abandoning expensive and toxic materials in chemical synthesis: This is the goal pursued by scientists at the University of Würzburg. In the magazine "Angewandte Chemie", they describe a new way to achieve this goal.
The synthesis of arylboronates to date has required metalliferous catalysts such as palladium, iridium or nickel. These materials have a number of drawbacks: The metals are either expensive, toxic or both.
Progress with zinc catalysts.
The Würzburg chemists Shubhankar Kumar Bose and Todd Marder now present an entirely new catalytic process that enables arylboronates to be produced at lower costs and with less environmental impact. Their success is based on the use of zinc catalysts. "Zinc is cheap, non-toxic and abundant on our planet," Marder names some of the metal's benefits.
A baffling effect occurred during their research work. The scientists haven't been able to fully account for the effect yet, but it should cause a stir among experts, because it might deliver the key to facilitating the synthesis of many important arylboronates in the future.
Simultaneous bonding of boronate groups
What caused the astonishment? To produce the arylboronates, circular molecules are used in which either a hydrogen atom or a halogen atom is replaced with a boronate group. When the Würzburg scientists initiated this exchange using their zinc catalyst, the two actions happened simultaneously. The result is an aryl with two boronate groups. Usually, these molecules are not so easy to synthesise and they are highly interesting for industrial synthesis.
Next steps in research
In a next step, the scientists want to find out what happened exactly during the reaction with the zinc catalyst. And they are working on increasing the yield of the much sought after substance: The reaction produces around 70 percent of molecules with one boronate group and 30 percent with two boronate groups.
Original publication
Shubhankar Kumar Bose, Andrea Deißenberger, Antonius Eichhorn, Patrick G. Steel, Zhenyang Lin, Todd B. Marder; "Zinc-Catalyzed Dual C–X and C–H Borylation of Aryl Halides"; Angew. Chem. Int. Ed.; 2015
Shubhankar Kumar Bose, Andrea Deißenberger, Antonius Eichhorn, Patrick G. Steel, Zhenyang Lin, Todd B. Marder; "Simultane Zink-katalysierte C–X- und C–H-Borylierung von Arylhalogeniden"; Angew. Chem.; 2015
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