Unusual process in Sonogashira cross-coupling was discovered by scientists from Zelinsky Institute

Functionalized acetylenes are a key fragment of many natural compounds and are actively used as intermediates in organic synthesis, pharmaceuticals, and materials science. Over the past decades, Sonogashira cross-coupling reaction has become one of the key approaches to the functionalization of alkynes in modern organic synthesis. Among the numerous palladium catalysts used in this transformation, palladium/N-heterocyclic carbene complexes have proven themselves to be highly active catalysts that are much more resistant to air and moisture than the popular palladium/phosphine complexes.

Researchers of Laboratory № 30 of Zelinsky Institute are actively studying the role of N-heterocyclic carbene ligands in the Sonogashira reaction catalyzed by palladium. In their latest work, they discovered an unusual process of carbon-carbon bond formation between N-heterocyclic carbene and alkyne. The detected transformation was studied in detail using mass spectrometry, DFT calculations, and molecular dynamics. It was found that this process ran with the participation of one of the key intermediate reaction products and should be taken into account when developing new catalytic systems for alkynes functionalization reactions.

Source:

D. B. Eremin, D. A. Boiko, A. Yu. Kostyukovich, J. V. Burykina, E. A. Denisova, M. Anania, J. Martens, G. Berden, J. Oomens, J. Roithová, and V. P. Ananikov Mechanistic study of Pd/NHC-catalyzed Sonogashira reaction: discovery of NHC-ethynyl coupling process Chem. Eur. J., 2020, accepted manuscript. DOI: 10.1002/chem.202003533.