- Exploring the scope of nitrogen acyclic carbenes (NACs) in gold-catalyzed reactions
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The catalytic activity of the recently reported nitrogen acyclic carbene (NAC) complexes of gold(I) has been investigated and compared with the reported activity of other gold(I) and gold(III) complexes. The complexes studied, [AuCl{C(NEt2)(NHTol-p)}], [AuCl{C(NEt2)(NHXylyl)}], and [Au(NTf2){C(NEt2)(NHXylyl)}], are very active in processes such as the rearrangement of homopropargylsulfoxides, the intramolecular hydroamination of N-allenyl carbamates, the intramolecular hydroalkoxylation of allenes, the hydroarylation of acetylenecarboxylic acid ester, and the benzylation of anisole. Although the NAC ligands have not been optimized for the reactions tested, the yields obtained are usually similar and sometimes better than those reported with other catalysts, showing that the presence of N-H bonds and the wider N-C-N angle in the NAC (as compared to the NHC) complexes are not detrimental for the catalysis. For the hydroarylation reaction (where two competing products can be formed), the NAC complexes allow favoring one over the other. For the benzylation of anisole the selectivity is complementary to that obtained using H[AuCl4] as catalyst, and depending on the substrate, the NAC gold(III) complexes outperform the activity of H[AuCl4]. On average, the reactivity found suggests that the basicity of NACs toward gold(I) is very similar to that of NHCs and higher than that of phosphines.
- Bartolome, Camino,Garcia-Cuadrado, Domingo,Ramiro, Zoraida,Espinet, Pablo
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- Cascade Reductive Friedel-Crafts Alkylation Catalyzed by Robust Iridium(III) Hydride Complexes Containing a Protic Triazolylidene Ligand
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The synthesis of complex molecules like active pharmaceutical ingredients typically requires multiple single-step reactions, in series or in a modular fashion, with laborious purification and potentially unstable intermediates. Cascade processes offer attractive synthetic remediation as they reduce time, energy, and waste associated with multistep syntheses. For example, triarylmethanes are traditionally prepared via several synthetic steps, and only a handful of cascade routes are known with limitations due to high catalyst loadings. Here, we present an expedient catalytic cascade process to produce triarylmethanes. For this purpose, we have developed a bifunctional iridium system as the efficient catalyst to build heterotriaryl synthons via reductive Friedel-Crafts alkylation from ketones, arenes, and hydrogen. The catalytically active species were generated in situ from a robust triazolyl iridium(III) hydride complex and acid and is composed of a metal-bound hydride and a proximal ligand-bound proton for reversible dihydrogen release. These complexes catalyze the direct hydrogenation of ketones at slow rates followed by dehydration. Appropriate adjustment of the conditions successfully intercepts this dehydration and leads instead to efficient C-C coupling and Friedel-Crafts alkylation. The scope of this cascade process includes a variety of carbonyl substrates such as aldehydes, (alkyl)(aryl)ketones, and diaryl ketones as precursor electrophiles with arenes and heteroarenes for Friedel-Crafts coupling. The reported method has been validated in a swift one-step synthesis of the core structure of a potent antibacterial agent. Excellent yields and exquisite selectivities were achieved for this cascade process with unprecedentedly low iridium loadings (0.02 mol %). Moreover, the catalytic activity of the protic system is significantly higher than that of an N-methylated analogue, confirming the benefit of the Ir-H/N-H hydride-proton system for high catalytic performance.
- Albrecht, Martin,Alshakova, Iryna D.
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p. 8999 - 9007
(2021/07/31)
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- Indium Tribromide-Catalysed Transfer-Hydrogenation: Expanding the Scope of the Hydrogenation and of the Regiodivergent DH or HD Addition to Alkenes
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The transfer-hydrogenation as well as the regioselective and regiodivergent addition of H?D from regiospecific deuterated dihydroaromatic compounds to a variety of 1,1-di- and trisubstituted alkenes was realised with InBr3 in dichloro(m)ethane. In comparison with the previously reported BF3?Et2O-catalysed process, electron-deficient aryl-substituents can be applied reliably and thereby several restrictions could be lifted, and new types of substrates could be transformed successfully in hydrodeuterogenation as well as deuterohydrogenation transfer-hydrogenation reactions.
- Li, Luomo,Hilt, Gerhard
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supporting information
p. 11221 - 11225
(2021/06/25)
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- Reductive activation and hydrofunctionalization of olefins by multiphoton tandem photoredox catalysis
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The conversion of olefin feedstocks to architecturally complex alkanes represents an important strategy in the expedient generation of valuable molecules for the chemical and life sciences. Synthetic approaches are reliant on the electrophilic activation of unactivated olefins, necessitating functionalization with nucleophiles. However, the reductive functionalization of unactivated and less activated olefins with electrophiles remains an ongoing challenge in synthetic chemistry. Here, we report the nucleophilic activation of inert styrenes through a photoinduced direct single electron reduction to the corresponding nucleophilic radical anion. Central to this approach is the multiphoton tandem photoredox cycle of the iridium photocatalyst [Ir(ppy)2(dtbbpy)] PF6, which triggers in situ formation of a high-energy photoreductant that selectively reduces styrene olefinic π bonds to radical anions without stoichiometric reductants or dissolving metals. This mild strategy enables the chemoselective reduction and hydrofunctionalization of styrenes to furnish valuable alkane and tertiary alcohol derivatives. Mechanistic studies support the formation of a styrene olefinic radical anion intermediate and a Birch-type reduction involving two sequential single electron transfers. Overall, this complementary mode of olefin activation achieves the hydrofunctionalization of less activated alkenes with electrophiles, adding value to abundant olefins as valuable building blocks in modern synthetic protocols.
- Czyz, Milena L.,Taylor, Mitchell S.,Horngren, Tyra H.,Polyzos, Anastasios
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p. 5472 - 5480
(2021/06/01)
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- Electrochemically Enabled, Nickel-Catalyzed Dehydroxylative Cross-Coupling of Alcohols with Aryl Halides
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As alcohols are ubiquitous throughout chemical science, this functional group represents a highly attractive starting material for forging new C-C bonds. Here, we demonstrate that the combination of anodic preparation of the alkoxy triphenylphosphonium ion and nickel-catalyzed cathodic reductive cross-coupling provides an efficient method to construct C(sp2)-C(sp3) bonds, in which free alcohols and aryl bromides - both readily available chemicals - can be directly used as coupling partners. This nickel-catalyzed paired electrolysis reaction features a broad substrate scope bearing a wide gamut of functionalities, which was illustrated by the late-stage arylation of several structurally complex natural products and pharmaceuticals.
- Li, Zijian,Sun, Wenxuan,Wang, Xianxu,Li, Luyang,Zhang, Yong,Li, Chao
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supporting information
p. 3536 - 3543
(2021/03/08)
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- Dynamic Kinetic Cross-Electrophile Arylation of Benzyl Alcohols by Nickel Catalysis
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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
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supporting information
p. 513 - 523
(2021/01/12)
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- Rhodium-Catalyzed Regiodivergent Synthesis of Alkylboronates via Deoxygenative Hydroboration of Aryl Ketones: Mechanism and Origin of Selectivities
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Here, we report an efficient rhodium-catalyzed deoxygenative borylation of ketones to synthesize alkylboronates, in which the regioselectivity can be switched by the choice of the ligand. The linear alkylboronates were obtained exclusively in the presence of P(nBu)3, and PPh2Me favored the formation of branched alkylboronates. The protocol also allows access to 1,1,2-triboronates from the readily available ketones. Mechanistic studies suggest that this Rh-catalyzed deoxygenative borylation of ketones goes through an alkene intermediate, which undergoes regiodivergent hydroboration to afford linear and branched alkylboronates. The different steric effects of PPh2Me and P(nBu)3 were found to be responsible for product selectivity by density functional theory calculations. The alkene intermediate can alternatively undergo sequential dehydrogenative borylation and hydroboration to deliver the triboronates.
- Zhang, Bing,Xu, Xin,Tao, Lei,Lin, Zhenyang,Zhao, Wanxiang
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p. 9495 - 9505
(2021/08/04)
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- BH3 ? Me2S: An Alternative Hydride Source for NiH-Catalyzed Reductive Migratory Hydroarylation and Hydroalkenylation of Alkenes
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Borane dimethylsulfide (BMS) was found to be an efficient hydride source for nickel-hydride catalyzed reductive migratory hydrofunctionalization reactions. Catalytic reductive migratory hydroarylation and migratory hydroalkenylation were achieved with BMS in high yields and with excellent regioselectivity. A large-scale experiment employing as little as 0.5 equivalents of BH3 ? Me2S as the hydride source delivered the desired migratory hydroarylation product in high yield and selectivity.
- Liu, Jiandong,Gong, Hegui,Zhu, Shaolin
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supporting information
p. 1543 - 1546
(2021/03/03)
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- Nickel-Catalyzed Regiodivergent Reductive Hydroarylation of Styrenes
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We report a ligand-controlled nickel-catalyzed reductive hydroarylation of styrenes with predictable and controllable regioselectivity. With a diamine ligand, the reaction produces selective linear hydroarylation products. Alternatively, with a chiral PyrOx ligand, branch-selective enantioenriched 1,1-diarylalkane products are obtained. Preliminary mechanistic results are consistent with a reductive Heck process.
- Xue, Yuhang,Chen, Jian,Song, Peihong,He, Yuli,Zhu, Shaolin
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p. 1647 - 1651
(2021/07/02)
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- Regiodivergent DH or HD Addition to Alkenes: Deuterohydrogenation versus Hydrodeuterogenation
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The regioselective and regiodivergent addition of H-D to a variety of 1,1-diarylalkenes was realized utilizing selectively deuterated dihydroaromatic compounds, which were generated by cobalt catalysis. The reaction was initiated by catalytic amounts of B
- Hilt, Gerhard,Li, Luomo
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supporting information
(2020/03/03)
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- Phosphorous acid-catalyzed alkylation of phenols with alkenes
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A H3PO3-catalyzed alkylation of phenols with alkenes is achieved in a facile, efficient, and selective manner. The reaction shows a unique selectivity, i.e., excellent regioselectivity, thorough suppression of overalkylation, without alkylation of a simple phenyl ring, and can selectively provide ortho-, meta-, or para-alkylated phenol derivatives in good to excellent yields. This feature along with mild reaction conditions, sensitive functional group tolerance, and scale-up synthesis and late modification of phenolic bioactive compounds make it an ideal and practical alternative for the modification of phenols.
- Wu, Shaofeng,Dong, Jianyu,Zhou, Dan,Wang, Wan,Liu, Long,Zhou, Yongbo
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p. 14307 - 14314
(2020/01/31)
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- [C^N]-Alkenyl Gold(III) Complexes by Proximal Ring-Opening of (2-Pyridyl)alkylidenecyclopropanes: Mechanistic Insights
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Pyridine-substituted alkylidenecyclopropanes (Py-ACPs) react with gold(III) salts under mild reaction conditions through an unprecedented, proximal ring-opening pathway, to generate highly appealing, catalytically active pyridine alkenyl [C^N]-gold(III) species. Mechanistic studies reveal that the activation of the C?C bond of the ACP takes place through an unusual concerted, σ-bond metathesis type-process.
- González, Jorge A.,López, Fernando,Mascare?as, José Luis,Nevado, Cristina,Verdugo, Felipe
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supporting information
p. 20049 - 20054
(2020/09/09)
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- Iron-catalysed enantioconvergent Suzuki-Miyaura cross-coupling to afford enantioenriched 1,1-diarylalkanes
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The first stereoconvergent Suzuki-Miyaura cross-coupling reaction was developed to afford enantioenriched 1,1-diarylalkanes. An iron-based complex containing a chiral cyanobis(oxazoline) ligand framework was best to obtain enantioenriched 1,1-diarylalkanes from cross-coupling reactions between unactivated aryl boronic esters and benzylic chlorides. Enhanced yields were obtained when 1,3,5-trimethoxybenzene was used as an additive, which is hypothesized to extend the lifetime of the iron-based catalyst. Exceptional enantioselectivities were obtained with challenging ortho-substituted benzylic chlorides. This journal is
- Tyrol, Chet C.,Yone, Nang S.,Gallin, Connor F.,Byers, Jeffery A.
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supporting information
p. 14661 - 14664
(2020/12/02)
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- Copper-Catalyzed Enantioconvergent Radical Suzuki-Miyaura C(sp3)-C(sp2) Cross-Coupling
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A copper-catalyzed enantioconvergent Suzuki-Miyaura C(sp3)-C(sp2) cross-coupling of various racemic alkyl halides with organoboronate esters has been established in high enantioselectivity. Critical to the success is the use of a chiral cinchona alkaloid-derived N,N,P-ligand for not only enhancing the reducing capability of copper catalyst to favor a stereoablative radical pathway over a stereospecific SN2-type process but also providing an ideal chiral environment to achieve the challenging enantiocontrol over the highly reactive radical species. The reaction has a broad scope with respect to both coupling partners, covering aryl- and heteroarylboronate esters, as well as benzyl-, heterobenzyl-, and propargyl bromides and chlorides with good functional group compatibility. Thus, it provides expedient access toward a range of useful enantioenriched skeletons featuring chiral tertiary benzylic stereocenters.
- Jiang, Sheng-Peng,Dong, Xiao-Yang,Gu, Qiang-Shuai,Ye, Liu,Li, Zhong-Liang,Liu, Xin-Yuan
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supporting information
p. 19652 - 19659
(2020/12/01)
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- Copper-Catalyzed Direct C-H Alkylation of Polyfluoroarenes by Using Hydrocarbons as an Alkylating Source
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Construction of carbon-carbon bonds is one of the most important tools in chemical synthesis. In the previously established cross-coupling reactions, prefunctionalized starting materials were usually employed in the form of aryl or alkyl (pseudo)halides or their metalated derivatives. However, the direct use of arenes and alkanes via a 2-fold oxidative C-H bond activation strategy to access chemoselective C(sp2)-C(sp3) cross-couplings is highly challenging due to the low reactivity of carbon-hydrogen (C-H) bonds and the difficulty in suppressing side reactions such as homocouplings. Herein, we present the new development of a copper-catalyzed cross-dehydrogenative coupling of polyfluoroarenes with alkanes under mild conditions. Relatively weak sp3 C-H bonds at the benzylic or allylic positions, and nonactivated hydrocarbons could be alkylated by the newly developed catalyst system. A moderate-to-high site selectivity was observed among various C-H bonds present in hydrocarbon reactants, including gaseous feedstocks and complex molecules. Mechanistic information was obtained by performing combined experimental and computational studies to reveal that the copper catalyst plays a dual role in activating both alkane sp3 C-H bonds and sp2 polyfluoroarene C-H bonds. It was also suggested that the noncovalent π-πinteraction and weak hydrogen bonds formed in situ between the optimal ligand and arene substrates are key to facilitating the current coupling reactions.
- Xie, Weilong,Heo, Joon,Kim, Dongwook,Chang, Sukbok
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supporting information
p. 7487 - 7496
(2020/08/06)
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- Nickel-Catalyzed Chain-Walking Cross-Electrophile Coupling of Alkyl and Aryl Halides and Olefin Hydroarylation Enabled by Electrochemical Reduction
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The first electrochemical approach for nickel-catalyzed cross-electrophile coupling was developed. This method provides a novel route to 1,1-diarylalkane derivatives from simple and readily available alkyl and aryl halides in good yields and excellent regioselectivity under mild conditions. The procedure shows good tolerance for a broad variety of functional groups and both primary and secondary alkyl halides can be used. Furthermore, the reaction was successfully scaled up to the multigram scale, thus indicating potential for industrial application. Mechanistic investigation suggested the formation of a nickel hydride in the electroreductive chain-walking arylation, which led to the development of a new nickel-catalyzed hydroarylation of styrenes to provide a series of 1,1-diaryl alkanes in good yields under mild reaction conditions.
- Brzozowska, Aleksandra,Kumar, Gadde Sathish,Nikolaienko, Pavlo,Peshkov, Anatoly,Rueping, Magnus,Zhu, Chen
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supporting information
p. 6513 - 6519
(2020/03/19)
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- Nickel-Catalyzed Electrochemical Reductive Relay Cross-Coupling of Alkyl Halides to Aryl Halides
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A highly regioselective Ni-catalyzed electrochemical reductive relay cross-coupling between an aryl halide and an alkyl halide has been developed in an undivided cell. Various functional groups are tolerated under these mild reaction conditions, which pro
- Fang, Ping,Jiao, Ke-Jin,Liu, Dong,Ma, Hong-Xing,Mei, Tian-Sheng,Qiu, Hui
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supporting information
p. 6520 - 6524
(2020/01/24)
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- Deoxygenative cross-electrophile coupling of benzyl chloroformates with aryl iodides
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This work describes Ni-catalyzed cross-electrophile coupling of benzyl chloroformate derivatives with aryl iodides that generates a wide range of diaryl methane products. The mild reaction conditions merit the C-O bond radical fragmentation of benzyl chloroformates via halide abstraction or a single electron reduction by a Ni catalyst. This work offers a new substrate type for cross-electrophile couplings.
- Pan, Yingying,Gong, Yuxin,Song, Yanhong,Tong, Weiqi,Gong, Hegui
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p. 4230 - 4233
(2019/05/06)
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- Nickel(0)-Catalyzed Hydroarylation of Styrenes and 1,3-Dienes with Organoboron Compounds
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A Ni-catalyzed hydroarylation of styrenes and 1,3-dienes with organoboron compounds has been developed. The reaction offers a highly selective approach to diarylalkanes and allylarenes under redox-neutral conditions. In this hydroarylation reaction, a new strategy that uses the proton of methanol to generate the active catalyst species Ni?H was developed. The Ni-catalyzed hydroarylation, combined with a Ir-catalyzed C?H borylation, affords a very efficient and straightforward access to a retinoic acid receptor agonist.
- Xiao, Li-Jun,Cheng, Lei,Feng, Wei-Min,Li, Mao-Lin,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 461 - 464
(2018/02/21)
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- Synthesis of 1,1′-diarylethanes and related systems by displacement of trichloroacetimidates with trimethylaluminum
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Benzylic trichloroacetimidates are readily displaced by trimethylaluminum under Lewis acid promoted conditions to provide the corresponding methyl substitution product. This method is a convenient way to access 1,1′-diarylethanes and related systems, which play a significant role in medicinal chemistry, with a number of systems owing their biological activity to this functionality. Most benzylic substrates undergo ready displacement, with electron deficient systems being the exception. The use of an enantiopure imidate showed significant racemization, implicating the formation of a cationic intermediate.
- Mahajani, Nivedita S.,Chisholm, John D.
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p. 4131 - 4139
(2018/04/14)
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- Ligand-Controlled Nickel-Catalyzed Reductive Relay Cross-Coupling of Alkyl Bromides and Aryl Bromides
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1,1-Diarylalkanes are important structural frameworks which are widespread in biologically active molecules. Herein, we report a reductive relay cross-coupling of alkyl bromides with aryl bromides by nickel catalysis with a simple nitrogen-containing ligand. This method selectively affords 1,1-diarylalkane derivatives with good to excellent yields and regioselectivity.
- Peng, Long,Li, Yuqiang,Li, Yangyang,Wang, Wang,Pang, Hailiang,Yin, Guoyin
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p. 310 - 313
(2018/01/17)
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- Mild and regioselective benzylic C-H functionalization: Ni-catalyzed reductive arylation of remote and proximal olefins
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The synergistic combination of NiH-catalyzed alkene isomerization with nickel-catalyzed cross-coupling has yielded a general protocol for the synthesis of a wide range of structurally diverse 1,1-diarylalkanes in excellent yields and high regioselectivities from readily accessible olefin starting materials. Furthermore, the practicality and synthetic flexibility of this approach is highlighted by the successful employment of isomeric mixtures of olefins for regioconvergent arylation.
- He, Yuli,Cai, Yalei,Zhu, Shaolin
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supporting information
p. 1061 - 1064
(2017/05/15)
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- Nickel-Catalyzed Reductive Cross-Coupling of Benzyl Halides with Aryl Halides
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Systematic studies of the coupling of benzylic with aryl halides are presented. The optimized reaction conditions for electron-deficient aryl halides cannot be applied to the electron-rich or neutral counterparts, and vice versa. The excellent functional group tolerance and broad substrate scope may enable the current work to be useful for the construction of diaryl methane products.
- Zhang, Qingchen,Wang, Xuan,Qian, Qun,Gong, Hegui
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p. 2829 - 2836
(2016/08/31)
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- Br?nsted Acid-Catalyzed Transfer Hydrogenation of Imines and Alkenes Using Cyclohexa-1,4-dienes as Dihydrogen Surrogates
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Cyclohexa-1,4-dienes are introduced to Br?nsted acid-catalyzed transfer hydrogenation as an alternative to the widely used Hantzsch dihydropyridines. While these hydrocarbon-based dihydrogen surrogates do offer little advantage over established protocols in imine reduction as well as reductive amination, their use enables the previously unprecedented transfer hydrogenation of structurally and electronically unbiased 1,1-di- and trisubstituted alkenes. The mild procedure requires 5.0 mol % of Tf2NH, but the less acidic sulfonic acids TfOH and TsOH work equally well.
- Chatterjee, Indranil,Oestreich, Martin
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supporting information
p. 2463 - 2466
(2016/06/09)
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- Synthesis and catalytic reactivity of mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes
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The reactions of five dinuclear carbonyl complexes [(η 5-C5Me4R)Mo(CO)3]2 [R = allyl, n Bu, t Bu, Ph, Bz] with I2 in chloroform solution gave the corresponding mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes [(η 5-C5Me4R)MoI(CO)3] [R = allyl (1), n Bu (2), t Bu (3), Ph (4), Bz (5)]. The molecular structures of complexes 2, 3 and 5 were determined by X-ray diffraction analysis. The results show that the substituent in the ring can directly affect the Mo-I bond distances; the more sterically hindered the substituent, the longer the Mo-I bond. Friedel-Crafts reactions of aromatic compounds with a variety of alkylation reagents catalyzed by the complexes showed that all of these mononuclear molybdenum carbonyl complexes have catalytic activity in Friedel-Crafts alkylation reactions. Indeed, compared with traditional catalysts, these mononuclear metal carbonyl complexes have obvious advantages such as higher activities, mild reaction conditions, high selectivity, simple post-processing, and environmentally friendly chemistry.
- Ma, Zhi-Hong,Lv, Lin-Qian,Wang, Hong,Han, Zhan-Gang,Zheng, Xue-Zhong,Lin, Jin
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p. 225 - 233
(2016/02/20)
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- Efficient hydroarylation and hydroalkenylation of vinylarenes by Br?nsted acid catalysis
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Br?nsted acid Tf2NH alone catalyzed Friedel-Crafts-type hydroarylation and head-to-tail hydroalkenylation of vinylarenes under mild reaction conditions have been realized, providing a readily scalable, metal-free, and practical access to the 1,1-diarylalkane scaffolds and trans-1,3-diaryl-1-butenes in high yields and excellent regioselectivities.
- Liu, Muwen,Zhang, Jinlong,Zhou, Hui,Yang, Huameng,Xia, Chungu,Jiang, Gaoxi
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p. 76780 - 76784
(2016/09/03)
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- Room Temperature Catalyst System for the Hydroarylation of Olefins
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A simple protocol for the hydroarylation of olefins to yield diarylmethine products is described. A Friedel-Crafts-type synthetic strategy allows direct access to biorelevant products in high atom efficiency. A combination of substoichiometric amounts of TMSCl and ZnBr2 promotes a rapid hydroarylation process at ambient temperature. The method is high yielding and is amenable to scale-up protocols.
- Lee, Siu Yin,Villani-Gale, Alexander,Eichman, Chad C.
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supporting information
p. 5034 - 5037
(2016/10/14)
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- Transition-Metal-Free Stereospecific Cross-Coupling with Alkenylboronic Acids as Nucleophiles
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We herein report a transition-metal-free cross-coupling between secondary alkyl halides/mesylates and aryl/alkenylboronic acid, providing expedited access to a series of nonchiral/chiral coupling products in moderate to good yields. Stereospecific SN2-type coupling is developed for the first time with alkenylboronic acids as pure nucleophiles, offering an attractive alternative to the stereospecific transition-metal-catalyzed C(sp2)-C(sp3) cross-coupling.
- Li, Chengxi,Zhang, Yuanyuan,Sun, Qi,Gu, Tongnian,Peng, Henian,Tang, Wenjun
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supporting information
p. 10774 - 10777
(2016/09/09)
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- Reductive cross-coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis
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A method for the reductive cross-coupling of conjugated arylalkenes and aryl bromides with hydrosilanes by cooperative palladium/copper catalysis was developed, thus resulting in the highly regioselective formation of various 1,1-diarylalkanes, including a biologically active molecule. Under the applied reaction conditions, high levels of functional-group tolerance were observed, and the reductive cross-coupling of internal alkynes with aryl bromides afforded trisubstituted alkenes. Forming a Co-op: A method for the reductive cross-coupling of conjugated arylalkenes or internal alkynes and aryl bromides with hydrosilanes using cooperative palladium/copper catalysis was developed. The resulting 1,1-diarylalkanes and trisubstituted alkenes were isolated with high regio- and stereoselectivity. Under the applied reaction conditions, high levels of functional-group tolerance were observed.
- Semba, Kazuhiko,Ariyama, Kenta,Zheng, Hong,Kameyama, Ryohei,Sakaki, Shigeyoshi,Nakao, Yoshiaki
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supporting information
p. 6275 - 6279
(2016/05/24)
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- B(C6F5)3-Catalyzed Transfer of Dihydrogen from One Unsaturated Hydrocarbon to Another
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A transition-metal-free transfer hydrogenation of 1,1-disubstituted alkenes with cyclohexa-1,4-dienes as the formal source of dihydrogen is reported. The process is initiated by B(C6F5)3-mediated hydride abstraction from the dihydrogen surrogate, forming a Bronsted acidic Wheland complex and [HB(C6F5)3]-. A sequence of proton and hydride transfers onto the alkene substrate then yields the alkane. Although several carbenium ion intermediates are involved, competing reaction channels, such as dihydrogen release and cationic dimerization of reactants, are largely suppressed by the use of a cyclohexa-1,4-diene with methyl groups at the C1 and C5 as well as at the C3 position, the site of hydride abstraction. The alkene concentration is another crucial factor. The various reaction pathways were computationally analyzed, leading to a mechanistic picture that is in full agreement with the experimental observations.
- Chatterjee, Indranil,Qu, Zheng-Wang,Grimme, Stefan,Oestreich, Martin
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supporting information
p. 12158 - 12162
(2015/10/12)
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- Electrophilic Fluorophosphonium Cations in Frustrated Lewis Pair Hydrogen Activation and Catalytic Hydrogenation of Olefins
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The combination of phosphorus(V)-based Lewis acids with diaryl amines and diaryl silylamines promotes reversible activation of dihydrogen and can be further exploited in metal-free catalytic olefin hydrogenation. Combined experimental and density functional theory (DFT) studies suggest a frustrated Lewis pair type activation mechanism. FLP hydrogenation: The combination of a phosphorus(V)-based Lewis acid with diaryl amines or diaryl silylamines promotes reversible activation of dihydrogen and can be further exploited in metal-free catalytic olefin hydrogenation. Combined experimental and density functional theory (DFT) studies suggest a frustrated Lewis pair (FLP)-type activation mechanism.
- Vom Stein, Thorsten,Perz, Manuel,Dobrovetsky, Roman,Winkelhaus, Daniel,Caputo, Christopher B.,Stephan, Douglas W.
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supporting information
p. 10178 - 10182
(2015/09/01)
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- Graphene-Catalyzed Direct Friedel-Crafts Alkylation Reactions: Mechanism, Selectivity, and Synthetic Utility
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Transition-metal-catalyzed alkylation reactions of arenes have become a central transformation in organic synthesis. Herein, we report the first general strategy for alkylation of arenes with styrenes and alcohols catalyzed by carbon-based materials, exploiting the unique property of graphenes to produce valuable diarylalkane products in high yields and excellent regioselectivity. The protocol is characterized by a wide substrate scope and excellent functional group tolerance. Notably, this process constitutes the first general application of graphenes to promote direct C-C bond formation utilizing polar functional groups anchored on the GO surface, thus opening the door for an array of functional group alkylations using benign and readily available graphene materials. Mechanistic studies suggest that the reaction proceeds via a tandem catalysis mechanism in which both of the coupling partners are activated by interaction with the GO surface.
- Hu, Feng,Patel, Mehulkumar,Luo, Feixiang,Flach, Carol,Mendelsohn, Richard,Garfunkel, Eric,He, Huixin,Szostak, Michal
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supporting information
p. 14473 - 14480
(2015/11/27)
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- Iron-catalyzed arylation of aromatic ketones and aldehydes mediated by organosilanes
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A simple and efficient iron-catalyzed method for arylation of aromatic carbonyl compounds is reported. The use of 4-% FeCl3 or Fe(acac) 3 as the catalyst, in combination with a slight excess of chlorotrimethylsilane and triethylsilane, chlorination of benzylic ketones and aldehydes with subsequent Friedel-Crafts alkylation of arenes is achieved. Although the method is limited by the general constraints associated with Friedel-Crafts alkylation reactions, robust applications for the synthesis of pharmaceutical intermediates and so on can be envisioned. A robust one-pot, iron-catalyzed chlorination Friedel-Crafts alkylation reaction of benzylic carbonyl compounds, mediated by chlorotrimethylsilane and triethylsilane, has been developed to yield substituted diaryl and triaryl building blocks. Copyright
- Savela, Risto,Majewski, Marcin,Leino, Reko
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p. 4137 - 4147
(2014/07/08)
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- Iron-catalyzed friedel-crafts benzylation with benzyl TMS ethers at room temperature
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Friedel-Crafts benzylations between unactivated arenes and benzyl alcohol derivatives are clean and straightforward processes to construct biologically useful di- and triarylmethanes. We have established an efficient iron-catalyzed Friedel-Crafts benzylation method at room temperature that uses benzyl TMS ethers as substrates, which are poorly reactive under common nucleophilic substitution conditions. The reaction seems to progress through iron-catalyzed self-condensation of the benzyl TMS ether to the corresponding dibenzylic ether. The use of excess arene relative to benzyl TMS ether produced mono-benzylated arene (diand tri-arylmethane products), whereas the use of excess benzyl TMS ether versus arene provided bis-benzylated arene (polyarylated products) in high yields and regioselectivities. In previous methods, the latter double Friedel-Crafts benzylations hardly proceed.
- Sawama, Yoshinari,Shishido, Yuko,Kawajiri, Takahiro,Goto, Ryota,Monguchi, Yasunari,Sajiki, Hironao
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p. 510 - 516
(2014/04/03)
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- Cationic Iron(III) porphyrin catalyzed dehydrative friedel-crafts reaction of alcohols with arenes
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Alcohols react with arenes in the presence of cationic iron(III) porphyrin catalyst. The reaction involves the formation of the C-C bond via dehydration, which is formal Lewis acid catalyzed Friedel-Crafts reaction. Georg Thieme Verlag Stuttgart, New York.
- Teranishi, Satoru,Kurahashi, Takuya,Matsubara, Seijiro
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supporting information
p. 2148 - 2152
(2013/10/21)
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- Highly chemoselective and enantiospecific Suzuki-Miyaura cross-couplings of benzylic organoboronic esters
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The use of potassium carbonate in addition to silver oxide is shown to increase the enantiospecificity of the Suzuki-Miyaura cross-coupling reaction of chiral secondary benzylic boronic esters. From mechanistic studies, it is shown that the reaction is co
- Glasspoole, Ben W.,Oderinde, Martins S.,Moore, Brandon D.,Antoft-Finch, Aurora,Crudden, Cathleen M.
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p. 1759 - 1763
(2013/07/26)
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- H-β-zeolite-catalysed hydroarylation of styrenes
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The hydroarylation of styrenes with various arene(heteroarene) compounds using H-β-zeolite as a green and recyclable heterogeneous catalyst under mild reaction conditions has been developed. The catalyst showed versatility and high selectivity (up to 100a€‰%) of desired 1,1-diarylalkanes in cyclohexane as solvent under the conditions studied. The catalyst could be reactivated by simple treatment with mineral acid at room temperature for better catalytic activity. Hydroarylation of styrenes with variousarene(heteroarene) compounds using H-β-zeolite as a green, heterogeneous and reusable catalyst under mild conditions is reported.
- Mohan, Darapaneni Chandra,Patil, Rajendra D.,Adimurthy, Subbarayappa
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experimental part
p. 3520 - 3525
(2012/07/30)
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- Chemical photocatalysis with 1-(N, N-dimethylamino)pyrene
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1-(N,N-Dimethylamino)pyrene was applied as chemical photocatalyst for two different organic reactions: Both the photocatalytically driven nucleophilic addition of methanol to 1,1-diphenylethylene and the photocatalytic deprotection of N-phenylsulfonylindole gave the corresponding products in good yields and in a highly sustainable way after short irradiation with high-power LED. This concept can potentially be transferred to other photochemical reactions. Copyright
- Penner, Alexander,B?tzner, Effi,Wagenknecht, Hans-Achim
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p. 2803 - 2807
(2013/02/22)
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- Synthesis of diarylmethanes via metal-free reductive cross-coupling of diarylborinic acids with tosyl hydrazones
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This paper describes a practical and efficient procedure that takes advantage of diarylborinic acids as a cost-effective alternative to arylboronic acids for synthesis of diarylmethanes through metal-free reductive cross-coupling with N-tosylhydrazones of aromatic aldehydes and ketones. The procedure tolerates hydroxyl, halide, amine, and allyl functionality, complementary to the transition-metal catalyzed cross-coupling techniques.
- Li, Xijing,Feng, Yuanyuan,Lin, Lin,Zou, Gang
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p. 10991 - 10995
(2013/02/22)
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- Carbon-based leaving group in substitution reactions: Functionalization of sp3-hybridized quaternary and tertiary benzylic carbon centers
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Lewis acid promoted substitution reactions employing Meldrum's acid and 5-methyl Meldrum's acid as carbon-based leaving groups are described which transform unstrained quaternary and tertiary benzylic Csp 3-Csp3 bonds into Csp3-X bonds (X = C, H, N). Importantly, this reaction has a broad scope in terms of both suitable substrates and nucleophiles with good to excellent yields obtained (typically >90%).
- Mahoney, Stuart J.,Lou, Tiantong,Bondarenko, Ganna,Fillion, Eric
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p. 3474 - 3477
(2012/09/05)
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- Application of nickel complexes modified by tridentate O,N,O'-ligands as precatalysts in nickel-catalyzed C(sp2)-C(sp3) bond formations
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1-Acetyl- [1a; 3,5-CF3, 1-C(=O)CH3] and 1-benzoyl-5-hydroxypyrazolines [1b; 3,5-CF3, 1-C(=O)C 6H5] have been synthesized and treated with Ni(OAc) 2·4H2O in the presence of an excess of base [NH3 or 4-(dimethylamino)pyridine (DMAP)] to form the nickel complexes 4a-c. These complexes have been characterized by various techniques, which indicate a tridentate coordination mode of the ligands. X-ray crystallography determined an O,N,O'-coordination of the ligands, in which the ligand is planar, the oxygen donors are trans to each other, and the nitrogen donor is in a cis position. The other coordination sites on the nickel centre are occupied by the added base molecules (NH3 or DMAP). The number of NH3 or DMAP ligands depends on the nature of the base; in the case of ammonia, one molecule is coordinated to the nickel centre to form a diamagnetic square-planar complex, whereas with DMAP, an octahedral paramagnetic complex with three additional DMAP ligands was observed. Initial catalytic experiments have been performed by applying the complexes in the nickel-catalyzed C(sp2)-C(sp3) cross-coupling of aryl halides with benzylzinc bromides or dialkylzinc reagents; excellent yields and selectivities have been achieved.
- Someya, Chika I.,Inoue, Shigeyoshi,Krackl, Sebastian,Irran, Elisabeth,Enthaler, Stephan
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experimental part
p. 1269 - 1277
(2012/05/19)
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- Iron(iii)-based ionic liquid-catalyzed regioselective benzylation of arenes and heteroarenes
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An easily prepared Fe(iii)-derived Lewis acid ionic liquid ([C 4mim][FeCl4]), being comprised of 1-butyl-3-methyl imidazolium cation and tetrachloroferrate anion, was found to be an efficient, recyclable catalyst for benzylation of various arenes/heteroarenes into the diarylmethanes derivatives under mild reaction conditions without utilization of additional organic solvent. Interestingly, the acidity of [C 4mim][FeCl4] could account for its catalytic activity in promoting the Lewis acid-catalyzed alkylation. Notably, this type of Fe(iii)-based ionic liquid (IL) shows excellent stability, and could be easily recovered, and reused for five times without significant loss of its catalytic activity.
- Gao, Jian,Wang, Jin-Quan,Song, Qing-Wen,He, Liang-Nian
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supporting information; experimental part
p. 1182 - 1186
(2011/06/25)
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- Microwave-accelerated alkylation of arenes/heteroarenes with benzylic alcohols using antimony(III) chloride as catalyst: Synthesis of O-heterocycles
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An efficient protocol for alkylation of electron-rich arenes/heteroarenes with benzylic alcohols under microwave irradiation using antimony(III) chloride as catalyst has been developed. The mild reaction conditions, high yields, operational simplicity, and applicability to various substrates render the approach a useful route for the synthesis of diaryl/triarylalkane. In addition, a new route for the conversion of ortho-alkenylated phenols into functionalized O-heterocycles has been accomplished. Georg Thieme Verlag Stuttgart ? New York.
- Shukla, Prashant,Choudhary, Manoj K.,Nayak, Sandip K.
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supporting information; experimental part
p. 1585 - 1591
(2011/08/03)
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- Tin exchanged heteropoly tungstate: An efficient catalyst for benzylation of arenes with benzyl alcohol
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The partial exchange of tin with the protons of 12-tungstophosphoric acid (TPA) results in a highly active heterogeneous catalyst for benzylation of arenes with benzyl alcohol as benzylating agent. The catalysts were characterized by X-ray diffraction, Laser-Raman and FT-IR of pyridine adsorption. The catalytic activity depends significantly on the extent of tin exchanged with the protons of heteropoly tungstate. The characterization results suggest the presence of Lewis acidic sites by the exchange of tin. The catalyst with partial exchange of Sn showed high benzylation activity, which in turn related to variation in acidity of the catalysts. The catalyst is highly active for benzylation reaction irrespective of the nature of substituted arenes and benzyl alcohols. These catalysts are highly active compared to other acid catalysts used for benzylation of different arenes. The catalyst is easy to separate from reaction mixture and exhibit consistent activity upon reuse. The plausible reaction mechanism based on the role of both Lewis and Bronsted acid sites of the catalyst was discussed.
- Ramesh Kumar, Ch.,Rao, K.T. Venkateswara,Sai Prasad,Lingaiah
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experimental part
p. 17 - 24
(2011/04/21)
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- Br?nsted acid-catalyzed synthesis of diarylmethanes under non-genotoxic conditions
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Triflic acid and triflimide were found to efficiently catalyze the formation of a wide diversity of diarylmethanes from the non-genotoxic benzylic acetates and electron-rich arenes or heteroarenes. The reaction worked best with acetates capable of generating a stabilized benzylic cationic species. In most cases, the reactions were conveniently run in the absence of solvent under mild conditions.
- Mendoza, Oscar,Rossey, Guy,Ghosez, Léon
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experimental part
p. 2235 - 2239
(2011/05/05)
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- Extremely efficient cross-coupling of benzylic halides with aryltitanium tris(isopropoxide) catalyzed by low loadings of a simple palladium(II) acctate/Tris(p-tolyl)phosphine system
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Highly efficient coupling reactions of benzylic bromides or chlorides with aryltitanium tris(isopropoxide) [ArTi(O-i-Pr)3] catalyzed by a simple palladium(II) Acctate/tris(p-tolyl)phosphine [Pd(OAc)2/ P(p-tolyl)3] system are reported. The coupling reactions proceed in general at room temperature employing low catalyst loadings of 0.02 to 0.2 mol%, affording coupling products in excellent yields of up to 99%. For benzylic bromides bearing strong electronwithdrawing cyano (CN) or trifluoromethyl (CF 3) substituents, the reactions require a higher catalyst loading of 1 mol%, or the reactions are carried out at 60°C. The catalytic system also tolerates (1-bromoethyl)benzene bearing β-hydrogen atoms while using a catalyst loading of 1 mol% to afford the coupling product in a 70% yield.
- Chen, Chi-Ren,Zhou, Shuangliu,Biradar, Deepak Baburao,Gau, Han-Mou
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experimental part
p. 1718 - 1727
(2010/09/18)
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- Rhodium-catalyzed reductive decyanation of nitriles using hydrosilane as a reducing agent: Scope, mechanism and synthetic application
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A rhodium-catalyzed reductive cleavage reaction of carbon-cyano bonds is developed using hydrosilane as a mild reducing agent. A wide range of nitriles, including aryl, benzyl, and p-hydrogen containing alkyl cyanides are applicable to this decyanation reaction. The method is also applicable to organic synthesis, in which benzyl cyanide is used as a benzyl anion equivalent and a cyano group functions as a removable ortho-directing group.
- Tobisu, Mamoru,Nakamura, Ryo,Kita, Yusuke,Chatani, Naoto
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scheme or table
p. 582 - 587
(2010/08/07)
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- Efficient and general continuous-flow hydroarylation and hydroalkylation of styrenes
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A simple and efficient continuous-flow hydroarylation of arenes and heteroarenes using various styrenes in conjunction with a heterogeneous catalyst has been developed. Additionally, this method has been successfully extended to the hydroalkylation of styrenes by employing 1,3-dicarbonyl compounds as the nucleophile. Multigram quantities of diarylmethanes have been prepared using this new flow method. Copyright
- Rueping, Magnus,Bootwicha, Teerawut,Sugiono, Erli
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experimental part
p. 2961 - 2965
(2011/02/22)
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- A simple catalyst for the efficient benzylation of arenes by using alcohols, ethers, styrenes, aldehydes, or ketones
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The compound [IrCp* (OTf)2(InBu)] (I nBu = 1,3-di-n-butyl-imidazolylidene) is an effective catalyst in the benzylation of arenes with different benzylating agents, such as alcohols, ethers and styrenes, representing an unprecedented highly versatile catalyst for this type of process. The same compound also catalyses a remarkable tandem process that allows the use of aldehydes and ketones as benzylating agents, through the base-free hydrogenation of C=O bonds with iPrOH and further use of the resulting primary or secondary alcohols as benzylating agents.
- Prades, Amparo,Corberan, Rosa,Poyatos, Macarena,Peris, Eduardo
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experimental part
p. 4610 - 4613
(2009/12/26)
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- Palladium-catalyzed cross-coupling reaction of secondary benzylic bromides with grignard reagents
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"Chemical Equation Presented" A mild palladium-catalyzed Kumada-Corriu reaction of secondary benzylic bromides with aryl and alkenyl Grignard reagents has been developed. In the presence of the Xantphos ligand, the undesired β-elimination pathway Is minimized, affording the corresponding cross-coupling products In acceptable to good yields. The reaction proceeds with inversion of the configuration.
- Lopez-Perez, Ana,Adrio, Javier,Carretero, Juan C.
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supporting information; experimental part
p. 5514 - 5517
(2010/02/28)
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