C–H Activation/Functionalization Catalyzed by Simple, Well-Defined Low-Valent Cobalt Complexes
摘要:
A facile C-H activation and functionalization of aromatic imines is presented using low-valent cobalt catalysts. Using Co(PMe3)(4) as catalyst we have developed an efficient and simple protocol for the C-H/hydroarylation of alkynes with an anti selectivity. Deuterium-labeling experiments, DFT calculations coupled with the use of a well-defined catalyst have for the first time shed light on the elusive black box of cobalt catalyzed C-H functionalization.
Cobalt-Catalyzed, Room-Temperature Addition of Aromatic Imines to Alkynes via Directed C–H Bond Activation
作者:Pin-Sheng Lee、Takeshi Fujita、Naohiko Yoshikai
DOI:10.1021/ja2047073
日期:2011.11.2
A quaternary catalytic system consisting of a cobalt salt, a triarylphosphine ligand, a Grignard reagent, and pyridine has been developed for chelation-assisted C-Hbondactivation of an aromatic imine, followed by insertion of an unactivated internal alkyne that occurs at ambient temperature. The reaction not only tolerates potentially senstitive functional groups (e.g., Cl, Br, CN, and tertiary amide)
Ruthenium(0)-catalyzed hydroarylation of alkynes via ketone-directed C–H functionalization using in situ-generated ruthenium complexes
作者:Feng Hu、Michal Szostak
DOI:10.1039/c6cc04537e
日期:——
Ketone-directed Ru(0)-catalyzed hydroarylation of alkynes enabled by in situ generation of a Ru(0) catalyst from an air-stable, inexpensive and user-friendly Ru(II) precatalyst is reported.
Cationic Ir complex ([Ir(cod)2]BF4 + BINAP) catalyzed the addition of ortho-C–H bonds in arylketones to alkynes, which gave alkenylated products in good to high yield. Styrene derivatives were good substrates, and the enantioselective addition to norbornene was also described.
Ternary catalytic systems consisting of cobalt salts, phosphine ligands, and Grignard reagents promote addition of arylpyridines and imines to unactivated internal alkynes with high regio- and stereoselectivities. Deuterium-labeling experiments suggest that the reaction involves chelation-assisted oxidative addition of the aryl C-H bond to the cobalt center and insertion of the C-C triple bond into the Co-H bond, followed by reductive elimination of the resulting diorganocobalt species.