RT info:eu-repo/semantics/article
T1 Palladium-Catalyzed Aerobic Homocoupling of Alkynes: Full Mechanistic Characterization of a More Complex Oxidase-Type Behavior
A1 Toledo Pérez, Alberto
A1 Funes Ardóiz, Ignacio
A1 Masera Cuni, Feliu
A1 Albéniz Jiménez, Ana Carmen
K1 Chemistry
K1 Catalysis
K1 Aalkyne
K1 C-C coupling
K1 Oxygen
K1 Oxidase
K1 Palladium
K1 Reaction mechanisms
AB A combined experimental and computationalapproach has been used to shed light on the mechanism of thePd-catalyzed oxidative homocoupling of alkynes using oxygen asthe oxidant. Mechanistic understanding is important because ofthe synthetically relevant direct involvement of oxygen in theoxidative coupling and because of the presence of related pro-cesses as undesired side reactions in cross-coupling reactionsinvolving terminal alkynes. A low-ligated [Pd(PPh3)(alkyne)] com-plex is key in the process, and it can be conveniently generated fromallylic palladium(II) complexes in the presence of a base or fromPd(I) allylic dimers as precatalysts. The catalytic coupling occursby alkyne metalation to give an anionic [Pd(PPh3)(alkynyl)]−complex that is then oxidized by oxygen. The interaction withoxygen occurs only on this electron-rich Pd(0) anionic species and leads to a (κO,κO-peroxo)palladium(II) singlet intermediate that undergoes subsequent protonolysis to give a (κO-hydroperoxo)palladium(II) complex and then hydrogen peroxide. The second alkyne metalation occurs on a Pd(II) derivative to give a bis(alkynyl)palladium(II) complex that evolves to the product by reductive elimination as the product-forming step. This reaction is an oxidase-type process that, in contrast to most Pd-catalyzed oxidative processes, occurs without separation of the substrate transformation and the catalyst oxidation, with these two processes being intertwined and dependent on one another.
PB American Chemical Society
YR 2018
FD 2018
LK http://uvadoc.uva.es/handle/10324/31482
UL http://uvadoc.uva.es/handle/10324/31482
LA eng
NO ACS Catalysis, 2018, vol. 8, p. 7495−7506
DS UVaDOC
RD 22-dic-2024