- Photoredox-Catalyzed Cascade Reactions Involving Aryl Radical: Total Synthesis of (±)-Norascyronone A and (±)-Eudesmol
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Herein, we have developed two types of photoredox-catalyzed cascade reactions using diaryliodonium salts for the concise synthesis of norascyronone A and β-eudesmol. A rationally designed photoredox-catalyzed arylation/cyclization/Friedel-Crafts cascade reaction of enone was exploited to generate the norascyronone polycyclic skeleton. A visible-light-induced radical cyclization/acyloxy-migration reaction was explored to forge the decalin skeleton of eudesmol, and mechanistic studies indicated the reaction was initiated by one-electron oxidation of the enol ester.
- Xu, Ze-Jun,Liu, Xu-Yuan,Zhu, Ming-Zhu,Xu, Yu-Liang,Yu, Yue,Xu, Hai-Ruo,Cheng, Ai-Xia,Lou, Hong-Xiang
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supporting information
p. 9073 - 9077
(2021/12/06)
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- Lewis Acidity Scale of Diaryliodonium Ions toward Oxygen, Nitrogen, and Halogen Lewis Bases
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Equilibrium constants for the associations of 17 diaryliodonium salts Ar2I+X- with 11 different Lewis bases (halide ions, carboxylates, p-nitrophenolate, amines, and tris(p-anisyl)phosphine) have been investigated by titrations followed by photometric or conductometric methods as well as by isothermal titration calorimetry (ITC) in acetonitrile at 20 °C. The resulting set of equilibrium constants KI covers 6 orders of magnitude and can be expressed by the linear free-energy relationship lg KI = sI LAI + LBI, which characterizes iodonium ions by the Lewis acidity parameter LAI, as well as the iodonium-specific affinities of Lewis bases by the Lewis basicity parameter LBI and the susceptibility sI. Least squares minimization with the definition LAI = 0 for Ph2I+ and sI = 1.00 for the benzoate ion provides Lewis acidities LAI for 17 iodonium ions and Lewis basicities LBI and sI for 10 Lewis bases. The lack of a general correlation between the Lewis basicities LBI (with respect to Ar2I+) and LB (with respect to Ar2CH+) indicates that different factors control the thermodynamics of Lewis adduct formation for iodonium ions and carbenium ions. Analysis of temperature-dependent equilibrium measurements as well as ITC experiments reveal a large entropic contribution to the observed Gibbs reaction energies for the Lewis adduct formations from iodonium ions and Lewis bases originating from solvation effects. The kinetics of the benzoate transfer from the bis(4-dimethylamino)-substituted benzhydryl benzoate Ar2CH-OBz to the phenyl(perfluorophenyl)iodonium ion was found to follow a first-order rate law. The first-order rate constant kobs was not affected by the concentration of Ph(C6F5)I+ indicating that the benzoate release from Ar2CH-OBz proceeds via an unassisted SN1-type mechanism followed by interception of the released benzoate ions by Ph(C6F5)I+ ions.
- Legault, Claude Y.,Mayer, Robert J.,Mayr, Herbert,Ofial, Armin R.
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supporting information
(2020/03/13)
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- Halogen exchange via a halogenation of diaryliodonium salts with cuprous halide
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An efficient halogenation reaction has been developed with diaryliodonium salts and cuprous halides. Various diaryliodonium salts 1 could perform the reaction with readily available CuBr or CuCl in CH3CN at 80°C, assembling bromoarenes or chloroarenes in up to 92% yields. This provides us a method for the transformation from iodoarenes to other haloarenes.
- Li, Jian,Liu, Li,Ding, Dong,Sun, Jiang-Tao
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p. 541 - 548
(2014/01/06)
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- Method for making diaryliodonium polyhalometalloid salts
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A method is provided for making certain diaryliodonium salt photoinitiators, based on the initial formation of diaryliodonium perchlorate which is formed from a diaryliodonium bisulfate precursor. The diaryliodonium perchlorate is then reacted with a counter ion source, such as an alkali metal hexafluoro metalloid salt, to produce the desired diaryliodonium salt, which can be used as a photoinitiator. The iodonium salt photoinitiators made by the method of the present invention can be used to effect the cure of a variety of cationically polymerizable organic materials, such as epoxy resins.
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- Photoinitiators
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Halogen onium salts, and onium salts of Group VA and V1A elements having an MF6- anion, where M is selected from P, As and Sb, have been found to exhibit unusual activity under ultraviolet light. These onium salts can be employed as cationic photoinitiators when used with a variety of organic resins and cyclic organic compounds.
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