Complete Switch of Selectivity in the C–H Alkenylation and Hydroarylation Catalyzed by Iridium: The Role of Directing Groups
摘要:
A complete switch in the Cp*Ir(III)-catalyzed paths between C-H olefination and hydroarylation was found to be crucially dependent on the type of directing groups. This dichotomy in product distribution was correlated to the efficiency in attaining syn-coplanarity of olefin-inserted 7-membered iridacycles. Theoretical studies support our hypothesis that the degree of flexibility of this key intermediate modulates the beta-H elimination, which ultimately affords the observed chemoselectivity.
The utility of Cp∗Co(III)-catalysts was expanded to oxidative C–C bond-forming reaction. In situ-generated Cp∗Co(III)-catalyst, rather than a preformed cationic Cp∗Co(III)-complex, was effective. Oxidative alkenylation of benzamides and acetanilide with ethyl acrylate proceeded with silver acetate as a stoichiometric oxidant, giving products in up to 93% yield.
Urea‐Substituted Tetramethylcyclopentadienyl Ligands for Supramolecularly Accelerated Rh
<sup>III</sup>
‐Catalyzed
<i>ortho</i>
‐C−H Olefination of Benzoic Acid Derivatives
作者:David Maurer、Bernhard Breit
DOI:10.1002/chem.202005130
日期:2021.2.5
Through kinetic studies and NMR titration experiments, the catalysts’ substrate recognition ability mediated by hydrogenbonding was identified to be the reason for this effect. Introduction of pyridone‐phosphine ligands capable of forming additional H‐bond interactions increased the catalytic performance even further. By unveiling a proportionality between reaction rate and relative complex formation
Palladium-catalyzed C–H alkenylation of C-aryl N-t-butyl nitrones with ethyl acrylate produced ortho-alkenylated benzamide derivatives via isomerization of the nitrone moiety. The use of 1,1,1,3,3,3-hexafluoro-2-propanol/acetic acid as a solvent resulted in effective C–H alkenylation, while competitive 1,3-dipolar cycloaddition was completely suppressed.
Ruthenium-Catalyzed Oxidative C–H Alkenylations of Anilides and Benzamides in Water
作者:Lutz Ackermann、Lianhui Wang、Ratnakancana Wolfram、Alexander V. Lygin
DOI:10.1021/ol203251s
日期:2012.2.3
A cationic ruthenium(II) complex enabled efficient oxidative alkenylations of anilides in water as a green solvent and proved applicable to double C-H bond functionalizations of (hetero)aromatic amides with ample scope. Detailed studies provided strong support for a change of ruthenation mechanism in the two transformations, with an irreversible metalation as the key step in cross-dehydrogenative alkenylations of benzamides.