Sonogashira coupling catalysts

Alkynes are important functional groups in biologically active small molecules, both as structural components as well as versatile reactive handles for further functionalisation. Firt reported in 1975, the Sonogashira coupling reaction has become a workehorse methodology in the cross-coupling toolbox. This coupling reaction takes place under mild conditions across a wide range of substrates and utilises homogeneous amine bases. Most Sonogashira couplings employ a Cu(I) co-catalyst to facilitate transmetalation of the alkynyl group, but many copper-free methodolgies have been developed to avoid undesiravle alkyne homodimerisation.