The first ruthenium-catalysed oxidative annulation of alkynes with air as an oxidant has been done by scientists in Germany.
The team used an inexpensive ruthenium catalyst for aerobic C-H bond functionalisations, providing novel access to structural motifs of bioactive alkaloids.
Oxidative annulations reactions of alkynes by C-H bond cleavages provides a route to polycyclic heteroarenes. Ruthenium-catalysed methods use stoichiometric amount of copper(II) or silver(II) salts, but these lead to heavy metal by-products. Rhodium-catalysed methods are known but this ruthenium method is cheaper with improved scope and chemoselectivity.
Ruthenium-catalyzed aerobic oxidative coupling of alkynes with 2-aryl-substituted pyrroles
L Ackermann, L Wang and A V Lygin, Chem. Sci., 2011,