Hydrido-Cobalt Catalyst as a Selective Tool for the Dimerisation of Arylacetylenes: Scope and Theoretical Studies
作者:Sandrine Ventre、Etienne Derat、Muriel Amatore、Corinne Aubert、Marc Petit
DOI:10.1002/adsc.201300486
日期:2013.9.16
A simple hydrido‐cobaltcomplex efficiently catalyses the highly regio‐ and stereoselective dimerisation of various terminal arylacetylenes under mild conditions. The corresponding (E)‐1,4‐enynes are obtained as sole isomers with good to excellent yields. DFT calculations revealed that the reaction proceeds via a CH activation/hydrocobaltation pathway.
regio- and stereochemical reaction outcome. Mechanistic studies suggest that a double μ–κ:η2 acetylide bridging enables a bimetallic syn-carbometalation. Interestingly, depending on the reaction conditions, it is also possible to form the geminal regioisomer as major product with the same catalyst. This regiodivergent outcome is explained by bi- versus monometallic reaction pathways.
Pyridine-Enhanced Head-to-Tail Dimerization of Terminal Alkynes by a Rhodium-N-Heterocyclic-Carbene Catalyst
作者:Laura Rubio-Pérez、Ramón Azpíroz、Andrea Di Giuseppe、Victor Polo、Ricardo Castarlenas、Jesús J. Pérez-Torrente、Luis A. Oro
DOI:10.1002/chem.201302079
日期:2013.11.4
rhodium‐catalyzed head‐to‐tail dimerization of terminalalkynes is presented. The presence of a pyridine ligand (py) in a Rh–N‐heterocyclic‐carbene (NHC) catalytic system not only dramatically switches the chemoselectivity from alkyne cyclotrimerization to dimerization but also enhances the catalytic activity. Several intermediates have been detected in the catalytic process, including the π‐alkyne‐coordinated RhI
Reactivity Switch Enabled by Counterion: Highly Chemoselective Dimerization and Hydration of Terminal Alkynes
作者:Caixia Xu、Weiyuan Du、Yi Zeng、Bin Dai、Hao Guo
DOI:10.1021/ol403684a
日期:2014.2.7
A counterion-controlled reactivity tuning in Pd-catalyzed highly chemoselective and regioselective dimerization and hydration of terminalalkynes is reported. The use of acetate as counterion favors the formation of an alkenyl alkynyl palladium intermediate which forms hitherto less reported 1,3-diaryl-substituted conjugated enynes after reductive elimination. Using chloride, which is a better leaving