Merging Catalysis in Single Electron Steps with Photoredox Catalysis—Efficient and Sustainable Radical Chemistry
作者:Zhenhua Zhang、Ruben B. Richrath、Andreas Gansäuer
DOI:10.1021/acscatal.9b00787
日期:2019.4.5
a combination of catalysts that allows the coupling of titanocene(III) catalysis with photoredox catalysis. Oxidation of radical intermediates by a photoredox catalyst opens novel catalytic mechanisms for reductive epoxide ring opening and redox-neutral epoxideradicalarylation. In the former case, the requirement of metallic reductants and stoichiometric acidic additives is bypassed.
Cationic Titanocene(III) Complexes for Catalysis in Single-Electron Steps
作者:Andreas Gansäuer、Sven Hildebrandt、Antonius Michelmann、Tobias Dahmen、Daniel von Laufenberg、Christian Kube、Godfred D. Fianu、Robert A. Flowers
DOI:10.1002/anie.201501955
日期:2015.6.8
By exploiting solvent and anion effects, [Cp2Ti]+ complexes for atom‐economical catalysis in single‐electron steps were developed and applied for the first time. These complexes constitute remarkably stable and active catalysts for radical arylations. The reaction kinetics and catalyst composition were studied by cyclic voltammetry and in situ IR spectroscopy.
A cyclic‐voltammetry‐based screening method for Cp2TiX‐catalyzed reactions is introduced. Our mechanism‐based approach enables the study of the influence of various additives on the electrochemically generated active catalyst Cp2TiX, which is in equilibrium with catalytically inactive [Cp2TiX2]−. Thioureas and ureas are most efficient in the generation of Cp2TiX in THF. Knowing the precise position
Catalytic, Atom-Economical Radical Arylation of Epoxides
作者:Andreas Gansäuer、Maike Behlendorf、Daniel von Laufenberg、André Fleckhaus、Christian Kube、Dhandapani V. Sadasivam、Robert A. Flowers
DOI:10.1002/anie.201200431
日期:2012.5.7
A slow electron waltz: Catalysis in single‐electron steps with radicals as intermediates is essential for an atom‐economical arylation of epoxides with a proton‐coupled electron transfer as a key step. Stabilization of the catalyst is essential for low catalyst loading, as demonstrated by reaction‐progress kinetic analysis, cyclic voltammetry, and calculations.
Cyclicvoltammetry‐based screening method for Cp2TiX‐catalyzed reactions is extended to the screening of solvents other than tetrahydrofuran for bulk electrolysis of the catalyst and radical arylation. It was found that CH3CN can be used as a solvent for both processes without additives. Furthermore, in tetrahydrofuran, squaramide L2 is more efficient than the previously reported supramolecular halide