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A metal catalyst makes sure that molecules join at the correct region of a carbon ring, disrupting the same bond every time.

Chemists have made strides in identifying reactions that disrupt notoriously unreactive carbon–hydrogen bonds, which is a key step when attaching molecules to carbon-ring structures. But it is still challenging to ensure that a molecule joins at the correct region of a ring. Frank Glorius and his colleagues at the University of Münster in Germany have solved this problem for a recalcitrant region on a class of rings known as benzo[b]thiophenes. Using palladium on a carbon support, together with copper chloride, the authors developed a catalyst with more than 99% selectivity for the desired hydrogen atom in many cases. The reaction is quite cheap, and withstands air and water.

J. Am. Chem. Soc. 135, 7450–7453 (2013)