- Dual Photoredox-/Palladium-Catalyzed Cross-Electrophile Couplings of Polyfluoroarenes with Aryl Halides and Triflates
-
A visible-light photoredox-/Pd-catalyzed cross-electrophile arylation of polyfluoroarenes with aryl halides and triflates in the presence of dialkylamines is reported for the first time. This synergistic protocol affords access to a series of fluorodiaryls from easily available starting materials under mild and operationally simple conditions. A series of mechanistic experiments, including the stoichiometric reactions of a ligated (aryl)Pd complex, Stern-Volmer fluorescence quenching studies, cyclic voltammetry studies, and UV-vis spectroscopy, were performed to elucidate the potential catalytic pathway in this synergistic process.
- Qin, Jian,Zhu, Shengqing,Chu, Lingling
-
supporting information
p. 2246 - 2252
(2021/04/02)
-
- Dynamic Kinetic Cross-Electrophile Arylation of Benzyl Alcohols by Nickel Catalysis
-
Catalytic transformation of alcohols via metal-catalyzed cross-coupling reactions is very important, but it typically relies on a multistep procedure. We here report a dynamic kinetic cross-coupling approach for the direct functionalization of alcohols. The feasibility of this strategy is demonstrated by a nickel-catalyzed cross-electrophile arylation reaction of benzyl alcohols with (hetero)aryl electrophiles. The reaction proceeds with a broad substrate scope of both coupling partners. The electron-rich, electron-poor, and ortho-/meta-/para-substituted (hetero)aryl electrophiles (e.g., Ar-OTf, Ar-I, Ar-Br, and inert Ar-Cl) all coupled well. Most of the functionalities, including aldehyde, ketone, amide, ester, nitrile, sulfone, furan, thiophene, benzothiophene, pyridine, quinolone, Ar-SiMe3, Ar-Bpin, and Ar-SnBu3, were tolerated. The dynamic nature of this method enables the direct arylation of benzylic alcohol in the presence of various nucleophilic groups, including nonactivated primary/secondary/tertiary alcohols, phenols, and free indoles. It thus offers a robust alternative to existing methods for the precise construction of diarylmethanes. The synthetic utility of the method was demonstrated by a concise synthesis of biologically active molecules and by its application to peptide modification and conjugation. Preliminary mechanistic studies revealed that the reaction of in situ formed benzyl oxalates with nickel, possibly via a radical process, is an initial step in the reaction with aryl electrophiles.
- Guo, Peng,Wang, Ke,Jin, Wen-Jie,Xie, Hao,Qi, Liangliang,Liu, Xue-Yuan,Shu, Xing-Zhong
-
supporting information
p. 513 - 523
(2021/01/12)
-
- Transition-Metal-Free C-C, C-O, and C-N Cross-Couplings Enabled by Light
-
Transition-metal-catalyzed cross-couplings to construct C-C, C-O, and C-N bonds have revolutionized chemical science. Despite great achievements, these metal catalysts also raise certain issues including their high cost, requirement of specialized ligands, sensitivity to air and moisture, and so-called "transition-metal-residue issue". Complementary strategy, which does not rely on the well-established oxidative addition, transmetalation, and reductive elimination mechanistic paradigm, would potentially eliminate all of these metal-related issues. Herein, we show that aryl triflates can be coupled with potassium aryl trifluoroborates, aliphatic alcohols, and nitriles without the assistance of metal catalysts empowered by photoenergy. Control experiments reveal that among all common aryl electrophiles only aryl triflates are competent in these couplings whereas aryl iodides and bromides cannot serve as the coupling partners. DFT calculation reveals that once converted to the aryl radical cation, aryl triflate would be more favorable to ipso substitution. Fluorescence spectroscopy and cyclic voltammetry investigations suggest that the interaction between excited acetone and aryl triflate is essential to these couplings. The results in this report are anticipated to provide new opportunities to perform cross-couplings.
- Liu, Wenbo,Li, Jianbin,Querard, Pierre,Li, Chao-Jun
-
supporting information
p. 6755 - 6764
(2019/05/06)
-
- Achieving vinylic selectivity in Mizoroki-heck reaction of cyclic olefins
-
In Heck reactions of cyclic olefins, the products usually have aryl groups that end up at the allylic and/or homoallylic position. We herein report new selectivity that adds aryl groups to the vinylic position. Cyclic olefins of various ring size worked well. The desired isomers were produced by palladium-hydride-catalyzed isomerization of the initial products. Thus, a specific catalyst must be used so that it can perform two jobs under one set of reaction conditions. Copyright
- Wu, Xiaojin,Lu, Yunpeng,Hirao, Hajime,Zhou, Jianrong
-
supporting information
p. 6014 - 6020
(2013/06/26)
-
- Intermolecular mizoroki-heck reaction of aliphatic olefins with high selectivity for substitution at the internal position
-
New ligand for old reaction: The title reaction of aryltriflates with aliphatic olefins leads to substitution at the internal position with high selectivity. The ratio of the desired isomer (shown in the scheme) to the sum of all other isomers is generall
- Qin, Liena,Ren, Xinfeng,Lu, Yunpeng,Li, Yongxin,Zhou, Jianrong
-
supporting information; experimental part
p. 5915 - 5919
(2012/07/30)
-
- A synthetic approach to a molecular crank mechanism: Toward intramolecular motion transformation between rotation and translation
-
A molecular crank mechanism that enables transformation between rotational and translational motions was designed and synthesized. This molecule consists of a molecular ball bearing as the rotational part in which two disk-shaped rotors can rotate relative to each other through ligand exchange and flipping motion, and a [2]rotaxane as a translational part in which an axle molecule can move back-and-forth through the cavity of a crown ether-based macrocycle. 1H NMR analysis revealed that these two motions influence each other.
- Okuno, Erika,Hiraoka, Shuichi,Shionoya, Mitsuhiko
-
supporting information; experimental part
p. 4107 - 4116
(2010/07/04)
-
- The use of Hagemann's Esters to prepare highly functionalized phenols and benzenes
-
Hagemann's esters can be converted into highly functionalized phenols or arenes. The systematic functionalization of Hagemann's ester derivatives permits the preparation of tri-and tetraalkyl-substituted phenols or tetra-, penta-, and hexaalkyl-substituted benzenes. Kotnis's aromatization procedure was found to be solvent dependent, and Suzuki couplings were found to be sensitive to steric hindrance. Wittig olefination and ortho-Claisen reactions were reliable means to introduce alkyl substituents at C-4 and/or C-5 positions, respectively. The acid-promoted dehydration of tertiary alcohol 46 to produce enone 47, followed by its selective alkylation (cf. 48) is new. ARKAT USA, Inc.
- Majetich, George,Allen, Scott
-
p. 104 - 124
(2012/11/07)
-
- Biaryl and aryl ketone synthesis via Pd-catalyzed decarboxylase coupling of carboxylate salts with aryl triflates
-
A bimetallic catalyst system has been developed that for the first time allows the decarboxylative crosscoupling of aryl and acyl carboxylates with aryl triflates. In contrast to aryl halides, these electrophiles give rise to non-coordinating anions as byproducts, which do not interfere with the decarboxylation step that leads to the generation of the carbon nucleophilic crosscoupling partner. As a result, the scope of carboxylate substrates usable in this transformation was extended from ortho-substituted or otherwise activated derivatives to a broad range of ortho-, meta-, and para-substituted aromatic carboxylates. Two alternative protocols have been optimized, one involving heating the substrates in the presence of CuI/1,10- phenanthroline (10-15 mol %) and PdI2/phosphine (23 mol%) in NMP for 1-24 h, the other involving CuI/l,10-phenanthroline (615mol%) and PdBr2/Tol-BINAP (2 mol % ) in NMP using microwave heating for 5-10 min. While most products are accessible using standard heating, the use of microwave irradiation was found to be beneficial especially for the conversion of non-activated carboxylates with functionalized aryl triflates. The synthetic utility of the transformation is demonstrated with 48 examples showing the scope and limitations of both protocols. In mechanistic studies, the special role of microwave irradiation is elucidated, and further perspectives of decarboxylase crosscouplings are discussed.
- Goossen, Lukas J.,Linder, Christophe,Rodriguez, Nuria,Lange, Paul P.
-
supporting information; experimental part
p. 9336 - 9349
(2010/04/03)
-
- N-heterocycle carbene (NHC)-ligated cyclopalladated N,N- dimethylbenzylamine: A highly active, practical and versatile catalyst for the Heck-Mizoroki reaction
-
The wide dissemination of catalytic protocols in academic and industrial laboratories is facilitated by the development of catalysts that are not only highly active but also user-friendly, stable to moisture, air and long term storage and easy to prepare on a large scale. Herein we describe a protocol for the Heck-Mizoroki reaction mediated by cyclopalladN-dimethylbenzylamine (dmba) ligated ne, 1,3-bdot;HCl in refluxing acetonitrile in air in the presence of K2CO in iates the H bromides in reagent grade NMP at the 0.1-2 mol% range without the need for rigorous anhydrous techniques or a glovebox, and is active even in air. The catalyst is capable of achieving very high levels of catalytic activity (TON of up to 5.22 × 105) for the coupling of a deactivated arylbromide, p-bromoanisole, with tBu acrylate as a benchmark substrate pair. A wide range of aryl bromides, iodides and, for the first time with a NHC-Pd catalyst, a triflate was coupled with diverse acrylate derivatives (nitrile, tert-butyl ester and amides) and styrene derivatives. The use of excess (>2 equiv.) of the aryl bromide and tert-butyl acrylate leads to mixture of tert-butyl β,β-diarylacrylate and tert-butyl cinnamate derivatives depending on the substitution pattern of the aryl bromide. Electron rich m- and p-substituted arylbromides give the diarylated products exclusively, whereas electron-poor aryl bromides give predominantly mono-arylated products. For o-substituted aryl bromides, no doubly arylated products could be obtained under any conditions. Overall, the active catalyst (IMes-Pd) shows higher activity with electron-rich aryl halides, a marked difference compared with the more commonly used phosphane-Pd or non-ligated Pd catalysts.
- Peh, Guang-Rong,Kantchev, Eric Assen B.,Zhang, Chi,Ying, Jackie Y.
-
supporting information; experimental part
p. 2110 - 2119
(2009/09/05)
-
- PPAR ACTIVE COMPOUNDS
-
Compounds are described that are active on at least one of PPARα, PPARδ, and PPARγ, which are useful for therapeutic and/or prophylactic methods involving modulation of at least one of PPARα, PPARδ, and PPARγ.
- -
-
Page/Page column 65
(2008/12/08)
-