- Direct C-H Arylation of Heteroarenes with Copper Impregnated on Magnetite as a Reusable Catalyst: Evidence for CuO Nanoparticle Catalysis in Solution
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A reusable copper-based catalyst system was employed for the direct arylation of electron-rich heteroarenes. Under mild and operationally simple reaction conditions good yields and selectivities were obtained using diaryliodonium salts as coupling partners. A combination of experimental methods including kinetic studies, filtration tests, and a series of analytical tools (TXRF, ICP-MS, SEM, XPS, TEM, EFTEM) provide evidence for catalytically active soluble nanoparticles formed from an amorphous heterogeneous precursor. Mechanistic studies hint at a redox-neutral process which promotes counterion dissociation from the diaryliodonium salt by a copper(II) oxide species.
- Vásquez-Céspedes, Suhelen,Chepiga, Kathryn M.,M?ller, Nadja,Sch?fer, Andreas H.,Glorius, Frank
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p. 5954 - 5961
(2016/09/09)
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- Pd/C as a catalyst for completely regioselective c=h functionalization of thiophenes under mild conditions
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The completely C3-selective arylation of thiophenes and benzo[b]thiophenes was achieved by using Pd/C as a heterogeneous catalyst without ligands or additives under mild reaction conditions. The practicability of this transformation is demonstrated by notable functional group tolerance and the insensitivity of the reaction to H2O and air. This method is also applicable to nitrogen- and oxygen-containing heterocycles, yielding the corresponding C2-arylated products. Three-phase tests along with Hg-poisoning and hot-filtration tests suggest that the catalytically active species is heterogeneous in nature. I+ can do better! Pd/C can be used without ligands or additives to catalyze the completely C3-selective arylation of diversely substituted thiophenes and benzo[b]thiophenes under mild reaction conditions. The physical nature of the catalytic species was investigated and the mechanism was studied. Relative rate data generated in a "robustness screen" were used to design a complex substrate that undergoes highly chemoselective sequential functionalization. Copyright
- Tang, Dan-Tam D.,Collins, Karl D.,Ernst, Johannes B.,Glorius, Frank
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supporting information
p. 1809 - 1813
(2014/03/21)
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- Rapid assessment of protecting-group stability by using a robustness screen
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An experimentally simple method has been developed to rapidly establish the stability of widely utilized silyl, acetal, and carbamate protecting groups to a given set of reaction conditions. Assessment of up to twelve protecting groups in a single experiment has been demonstrated. Evaluation of this protocol in two unrelated synthetic transformations suggests that this method can be used to select appropriate protecting groups in the design of synthetic routes.
- Collins, Karl D.,Ruehling, Andreas,Lied, Fabian,Glorius, Frank
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supporting information
p. 3800 - 3805
(2014/04/03)
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- Pd-catalyzed β-selective direct C-H bond arylation of thiophenes with aryltrimethylsilanes
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Direct arylation of thiophenes and benzothiophenes with aryltrimethylsilanes was effectively catalyzed by PdCl2(MeCN) 2 in the presence of CuCl2 as an oxidant. The reaction preferentially occurred at the β-position of both
- Funaki, Kenji,Sato, Tetsuo,Oi, Shuichi
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supporting information
p. 6186 - 6189
(2013/02/23)
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