Towards Long-Living Metathesis Catalysts by Tuning the N-Heterocyclic Carbene (NHC) Ligand on Trifluoroacetamide-Activated Boomerang Ru Complexes
作者:Hervé Clavier、Fréderic Caijo、Etienne Borré、Diane Rix、Fabien Boeda、Steven P. Nolan、Marc Mauduit
DOI:10.1002/ejoc.200900407
日期:2009.9
trifluoromethylamido-containing “boomerang” precatalysts bearing various N-heterocycliccarbene (NHC) ligands are reported. Comparative kinetic and stability studies show the significant effect of the NHC on the catalyst reaction profile. An investigation of the reaction scope for diverse metathesis transformations has allowed us to establish the influence of the NHC on catalyst activity, especially as a
Increased Efficiency in Cross-Metathesis Reactions of Sterically Hindered Olefins
作者:Ian C. Stewart、Christopher J. Douglas、Robert H. Grubbs
DOI:10.1021/ol702624n
日期:2008.2.1
Efficiency in olefin cross-metathesis reactions is affected upon reducing the steric bulk of N-heterocyclic carbene ligands of ruthenium-based catalysts. For the formation of disubstituted olefins containing one or more allylic substituents, the catalyst bearing N-tolyl groups is more efficient than the corresponding N-mesityl catalyst. In contrast, the formation of trisubstituted olefins is more efficient
Synthesis of Symmetrical Trisubstituted Olefins by Cross Metathesis
作者:Arnab K. Chatterjee、Daniel P. Sanders、Robert H. Grubbs
DOI:10.1021/ol0259793
日期:2002.5.1
[reaction: see text] Trisubstituted alkenes have been prepared via intermolecular olefin cross-metathesis (CM) between alpha-olefins and symmetrically 1,1-disubstituted olefins using an imidazolylidene ruthenium benzylidene complex. Of particular interest is the synthesis of isoprenoid/prenyl groups by a simple solvent-free CM reaction with isobutylene. In addition, prenyl groups can also be installed
Studies on the asymmetric synthesis of huperzine A. Part 2: Highly enantioselective palladium-catalyzed bicycloannulation of the β-keto-ester using new chiral ferrocenylphosphine ligands
作者:Xu-Chang He、Bin Wang、Gengli Yu、Donglu Bai
DOI:10.1016/s0957-4166(02)00006-x
日期:2001.12
Newchiralferrocenylphosphineligands were designed and tested in the enantioselective bicycloannulation of β-keto-ester 2 with bifunctional allylic agent 4. A range of e.e. values from 80 to 90% of the bicyclic intermediate 6 was achieved. Subsequently, enantiopure (−)-huperzine A was prepared in ca. 40% yield from β-keto-ester 2.
Radical hydro-fluorosulfonylation of olefins has been successfully achieved by employing FABI as a FSO2-radical precursor and ODA as an organic photocatalyst. With this photocatalytic system, radical hydro-fluorosulfonylation of alkynes can also be realized with a unique, high Z-selectivity. Utilization of this method is further demonstrated in the late-stage modification of natural products and drug