Reaction Pathways and Redox States in α‐Selective Cobalt‐Catalyzed Hydroborations of Alkynes
作者:Clemens K. Blasius、Vladislav Vasilenko、Regina Matveeva、Hubert Wadepohl、Lutz H. Gade
DOI:10.1002/anie.202009625
日期:2020.12.14
Cobalt(II) alkyl complexes supported by a monoanionic NNN pincer ligand are pre‐catalysts for the regioselective hydroboration of terminal alkynes, yielding the Markovnikov products with α:β‐(E) ratios of up to 97:3. A cobalt(II) hydride and a cobalt(II) vinyl complex appear to determine the main reaction pathway. In a background reaction the highly reactive hydrido species specifically converts to
N-Heterocyclic carbenes: deducing σ- and π-contributions in Rh-catalyzed hydroboration and Pd-catalyzed coupling reactions
作者:Dimitri M. Khramov、Evelyn L. Rosen、Joyce A.V. Er、Peter D. Vu、Vincent M. Lynch、Christopher W. Bielawski
DOI:10.1016/j.tet.2008.04.030
日期:2008.7
The effect of tuning the electronic properties of N-heterocyclic carbene (NHC) ligands was evaluated in multiple, mechanistically distinct, metal-mediated reactions. Hydroboration and Heck reactions, catalyzed by Rh-NHC and Pd-NHC complexes, respectively, were found to result in yields that were up to ten times lower when pi-withdrawing substituents were incorporated into the NHC backbone relative to analogues bearing sigma-withdrawing groups. (C) 2008 Elsevier Ltd. All Fights reserved.