- Synthesis of Bidentate Nitrogen Ligands by Rh-Catalyzed C-H Annulation and Their Application to Pd-Catalyzed Aerobic C-H Alkenylation
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A new class of bidentate ligands was prepared by a modular approach involving Rh-catalyzed C-H annulation reactions. The resulting conformationally constrained ligands enabled the Pd-catalyzed C-H alkenylation at electron-rich and sterically less hindered positions of electron-rich arenes while promoting the facile oxidation of Pd(0) intermediates by oxygen. This newly introduced ligand class is complementary to the ligands developed for Pd-catalyzed oxidative reactions and may find broad application in transition-metal-catalyzed reactions.
- Kim, Hyun Tae,Kang, Eunsu,Kim, Minkyu,Joo, Jung Min
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supporting information
p. 3657 - 3662
(2021/05/10)
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- Iodonium Cation-Pool Electrolysis for the Three-Component Synthesis of 1,3-Oxazoles
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The synthesis of 1,3-oxazoles from symmetrical and unsymmetrical alkynes was realized by an iodonium cation-pool electrolysis of I2 in acetonitrile with a well-defined water content. Mechanistic investigations suggest that the alkyne reacts with the acetonitrile-stabilized I+ ions, followed by a Ritter-type reaction of the solvent to a nitrilium ion, which is then attacked by water. The ring closure to the 1,3-oxazoles released molecular iodine, which was visible by the naked eye. Also, some unsymmetrical internal alkynes were tested and a regioselective formation of a single isomer was determined by two-dimensional NMR experiments.
- Sattler, Lars E.,Hilt, Gerhard
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p. 605 - 608
(2020/12/07)
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- Asymmetric Dearomatization of Indole by Palladium/PC-Phos-Catalyzed Dynamic Kinetic Transformation
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A palladium-catalyzed intermolecular dynamic kinetic asymmetric dearomatization of 3-arylindoles with internal alkynes was developed with the use of achiral Xantphos and chiral sulfinamide phosphine ligand (PC-Phos) as the co-ligands. This method could deliver various spiro[indene-1,3′-indole] compounds in good yields (up to 95 % yield) with up to 98 % ee. The salient features of the transformation include the use of readily available substrates, ease of scale-up and the versatile functionalization of the products. The mechanistic experiments gave some insights on active intermediates.
- Cheng, Jie,Chu, Haoke,Guo, Yin-Long,Yang, Junfeng,Zhang, Junliang
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supporting information
p. 21991 - 21996
(2020/10/02)
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- Ruthenium(ii)-catalyzed intermolecular annulation of alkenyl sulfonamides with alkynes: Access to bicyclic sultams
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A ruthenium-catalyzed allylic C(sp3)-H activation strategy has been employed to develop an intermolecular coupling of alkenyl sulfonamides with alkynes. This protocol features the diastereoselective construction of [3.3.0] and [4.3.0] bicyclic sultams in one step.
- Qian, Lei-Lei,Min, Xiang-Ting,Hu, Yan-Cheng,Shen, Bing-Xue,Yang, Sa-Na,Wan, Boshun,Chen, Qing-An
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supporting information
p. 2614 - 2617
(2020/03/10)
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- Preparation and Reactions of Mono- and Bis-Pivaloyloxyzinc Acetylides
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Mono-pivaloyloxyzinc acetylide and bis-pivaloyloxyzinc acetylide were selectively prepared from ethynylmagnesium bromide in quantitative yields. These zinc reagents readily underwent Negishi cross-couplings with (hetero)aryl iodides or bromides as well as subsequent Sonogashira cross-couplings. 1,3-Dipolar cycloadditions of these zinc acetylides with benzylic azides produced zincated and bis-zincated triazoles which were trapped with several electrophiles. An opposite regioselectivity compared to the Cu-catalyzed click-reactions was observed.
- Tüllmann, Carl Phillip,Chen, Yi-Hung,Schuster, Robin J.,Knochel, Paul
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supporting information
p. 4601 - 4605
(2018/08/09)
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- Site-Selective Catalytic Carboxylation of Unsaturated Hydrocarbons with CO2 and Water
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A catalytic protocol that reliably predicts and controls the site-selective incorporation of CO2 to a wide range of unsaturated hydrocarbons utilizing water as formal hydride source is described. This platform unlocks an opportunity to catalytically repurpose three abundant, orthogonal feedstocks under mild conditions.
- Gaydou, Morgane,Moragas, Toni,Juliá-Hernández, Francisco,Martin, Ruben
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supporting information
p. 12161 - 12164
(2017/09/12)
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- Pd- and Ni-catalyzed cross-coupling reactions of functionalized organozinc reagents with unsaturated thioethers
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A variety of unsaturated thioethers have been subjected to cross-coupling reactions with functionalized zinc reagents in the presence of a transition-metal catalyst. Three different catalytic systems based on Pd(OAc)2 or [Ni(acac)2] and the ligands S-Phos or DPE-Phos gave the best results. N-Heterocyclic thioethers based on a pyridine, pyrimidine, pyrazine, pyridazine, triazine, benzothiazole, benzoxazole, pyrrole, or quinazoline ring, as well as thiomethylacetylenes, serve as electrophiles in this cross-coupling reaction. Aryl-, heteroaryl-, benzylic, and alkylzinc halides with sensitive functionalities, such as ester, nitrile, or ketone groups react at ambient temperature with unsaturated thioethers using a Ni catalyst. The corresponding Pd-catalyzed reactions require slightly higher temperatures. Large-scale cross-coupling experiments (10-20 mmol) with N-heterocycles are also reported.
- Melzig, Laurin,Metzger, Albrecht,Knochel, Paul
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supporting information; experimental part
p. 2948 - 2956
(2011/04/16)
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- Pyrrole synthesis via allylic sp3 C-H activation of enamines followed by intermolecular coupling with unactivated alkynes
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A conceptually novel pyrrole synthesis is reported, efficiently merging enamines and (unactivated) alkynes under oxidative conditions. In an intermolecular Rh catalyzed process, the challenging allylic sp3 C-H activation of the enamine substrates is followed by the cyclization with the alkyne (R3 = CO2R). Alternatively, in some cases (R 3 = CN), the enamine can be utilized for a vinylic sp2 C-H activation. A total of 17 examples with yields above 60% is presented, together with the results of an initial mechanistic investigation.
- Rakshit, Souvik,Patureau, Frederic W.,Glorius, Frank
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supporting information; experimental part
p. 9585 - 9587
(2010/09/10)
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- Alkyne metathesis with simple catalyst systems: High yield dimerization of propynylated aromatics; scope and limitations
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High yield dimerization of propynylated benzenes and propynylnaphthalene by a mixture of Mo(CO)6 and 4-chlorophenol at 140 °C in 1,2-dichlorobenzene is reported to give the corresponding disubstituted alkynes. The scope and limitation of the reaction and the influence of substitution pattern and substitution type are discussed. Oxygen or nitrogen carrying substrates metathesize in moderate to good yields and ortho-alkyl substituted examples form the respective tolanes very efficiently.
- Pschirer, Neil Gregory,Bunz, Uwe H. F.
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p. 2481 - 2484
(2007/10/03)
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