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Development of highly efficient Friedel-Crafts alkylations with alcohols using heterogeneous catalysts under continuous-flow conditions
The development of Friedel-Crafts alkylations with alcohols under continuous-flow conditions using heterogeneous catalysts is reported. The reactivities and durabilities of the examined catalysts were systematically investigated, which showed that montmorillonite clay is the best catalyst for these reactions. A high turnover frequency of 9.0 × 102h?1was recorded under continuous-flow conditions, and the continuous operation was successfully maintained over one week.
Kobayashi, Shū,Koumura, Nagatoshi,Masuda, Koichiro,Okamoto, Yukiko,Onozawa, Shun-Ya
p. 24424 - 24428
(2021/07/29)

Multifunctional oxygen vacancies in WO3–x for catalytic alkylation of C–H by alcohols under red-light
Surface reaction kinetics and light absorption properties of a photocatalyst are essential demands for efficiently solar to chemical energy converting. In this study, plasmonic WO3–x was firstly applied to photocatalytic alkylation of arenes under red light irradiation. The oxygen vacancies, both on the surface and in the bulk of WO3–x, allow abundant free electrons to increase carrier densities and support its LSPR using low energy photons. The surface oxygen vacancies have more functions: they not only release surface tungsten sites which ensure the chemisorption of alcohols due to the coordianation ability but also promote the activation of alcohols via an efficient transport of the holes on the neighbouring O sites to chemisorption alcohol species. In brief, the bulk oxygen vacancies provide abundant charges and the surface vacancies promote the bond adsorption and activation abilities, which ensure the high efficiency of photocatalytic alkylation of C–H.
Gu, Xianmo,Sun, Xichen,Wang, Yunwei,Zhang, Jin,Zheng, Zhanfeng,Zhu, Pengqi
p. 208 - 217
(2021/09/06)

Cascade Reductive Friedel-Crafts Alkylation Catalyzed by Robust Iridium(III) Hydride Complexes Containing a Protic Triazolylidene Ligand
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.
p. 8999 - 9007
(2021/07/31)

Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
Chemoselective deoxygenation of carbonyls and alcohols using hydrogen by heterogeneous base-metal catalysts is crucial for the sustainable production of fine chemicals and biofuels. We report an aluminum metal-organic framework (DUT-5) node support cobalt(II) hydride, which is a highly chemoselective and recyclable heterogeneous catalyst for deoxygenation of a range of aromatic and aliphatic ketones, aldehydes, and primary and secondary alcohols, including biomass-derived substrates under 1 bar H2. The single-site cobalt catalyst (DUT-5-CoH) was easily prepared by postsynthetic metalation of the secondary building units (SBUs) of DUT-5 with CoCl2 followed by the reaction of NaEt3BH. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) indicated the presence of CoII and AlIII centers in DUT-5-CoH and DUT-5-Co after catalysis. The coordination environment of the cobalt center of DUT-5-Co before and after catalysis was established by extended X-ray fine structure spectroscopy (EXAFS) and density functional theory. The kinetic and computational data suggest reversible carbonyl coordination to cobalt preceding the turnover-limiting step, which involves 1,2-insertion of the coordinated carbonyl into the cobalt-hydride bond. The unique coordination environment of the cobalt ion ligated by oxo-nodes within the porous framework and the rate independency on the pressure of H2 allow the deoxygenation reactions chemoselectively under ambient hydrogen pressure.
Antil, Neha,Kumar, Ajay,Akhtar, Naved,Newar, Rajashree,Begum, Wahida,Manna, Kuntal
supporting information
p. 9029 - 9039
(2021/06/28)

Method for reducing carbonyl reduction to methylene under illumination
The invention belongs to the technical field of organic chemical synthesis. The method comprises the following steps: (1) mixing the carbonyl compound and the amine compound in a solvent, reacting 3 - 6 under the illumination of 380 - 456 nm, the reaction system is low in toxicity, high in atom utilization rate 12 - 24h. and production efficiency, safe and controllable in reaction process and capable of simplifying the operation in the preparation and production process. At the same time, the residue toxicity of the reaction is minimized, the pollution caused by the production process to the environment is reduced, and the steps and operations of removing residues after the reaction are simplified. In addition, the reactant feedstock is readily available. The reactant does not need additional modification before the reaction, can be directly used for preparing production, simplifies the operation steps, and shortens the reaction route. The production cost is obviously reduced.
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Paragraph 0033-0038; 0104-0108

(2021/09/29)

Conversion of Aryl Aldehydes to Benzyl Iodides and Diarylmethanes by H3PO3/I2
For the first time, H3PO3 was used as both the reducing reagent and the promotor in the reductive benzylation reactions with aryl aldehydes. By using a H3PO3/I2 combination, various aromatic aldehydes underwent iodination reactions and Friedel-Crafts type reactions with arenes via benzyl iodide intermediates, readily producing benzyl iodides and diarylmethanes in good yields. Intramolecular cyclization reactions also took place, giving the corresponding cyclic compounds. This new strategy features easy-handling, low-cost, and metal-free conditions.
Lv, Fang,Xiao, Jing,Xiang, Junchun,Guo, Fengzhe,Tang, Zi-Long,Han, Li-Biao
p. 3081 - 3088
(2021/02/01)

Controlled Access to C1-Symmetrical Cyclotriveratrylenes (CTVs) by Using a Sequential Barluenga Boronic Coupling (BBC) Approach
We describe here a controlled approach to C1-symmetrical cyclotriveratrylenes (CTVs). In this approach dimers are synthesized through Barluenga boronic coupling (BBC) and after borylation, the last aromatic ring is introduced by a second BBC. After functional transformations of the trimers, the CTVs are formed using intramolecular SEAr. (Figure presented.).
Cailly, Thomas,Dubost, Emmanuelle,Fabis, Frédéric,Fossé, Pierre,Vigier, Clément
supporting information
p. 3756 - 3761
(2021/07/14)

Mixed Alkyl/Aryl Diphos Ligands for Iron-Catalyzed Negishi and Kumada Cross Coupling Towards the Synthesis of Diarylmethane
Mixed alkyl/aryl diphos ligands have been prepared and their application in iron-catalyzed cross coupling of benzylic chlorides with diaryl zinc (Negishi) or aryl Grignard reagents (Kumada) towards the synthesis of diarylmethane has been evaluated. The iron?diphos catalytic system exhibited the enhanced activity and selectivity in the two coupling reactions. The electron-rich mixed PPh2/PCy2 ligands outperformed their symmetrical PPh2 congeners, and led to decreased homocoupling byproduct formation. It indicates that the electronic effect of the ligands plays an important role in the catalytic performance. The Fe catalyst supported by L8 bearing an electron-rich PCy2 substituent and a sterically demanding tert-butyl on ethene backbone exhibited the best catalytic performance and good functional group tolerance in the two cross coupling reactions.
Ma, Xufeng,Wang, Han,Liu, Yao,Zhao, Xing,Zhang, Jun
p. 5134 - 5140
(2021/11/16)

Photochemical benzylic radical arylation promoted by supported Pd nanostructures
We report a novel way to promote photochemical benzylic radical arylations using Pd nanostructures. Traditional benzylic radical reaction pathways are challenged by the presence of metal centres that provoke unprecedented regioselectivity towards more synthetically relevant C(sp3)-C(sp2) couplings. This new C-H activation pathway is rationalised by means of a pseudo-persistent radical effect facilitated by metal centres. We show the mechanistic and computational aspects of the heterogeneous photocatalytic processes that are the root of this drastic change in reactivity. This journal is
Costa, Paolo,Gawargy, Teresa A.,Lanterna, Anabel E.,Scaiano, Juan C.
supporting information
p. 6047 - 6052
(2020/10/21)

Friedel–Crafts benzylation of toluene catalyzed by ZnCl2/SiO2 heterogeneous catalyst to para- and ortho-mono-benzylated toluene
A series of catalysts was prepared for the liquid-phase Friedel–Crafts benzylation of toluene with benzyl chloride (BC) by impregnating rice husk ash silica with ZnCl2 (3?wt%, 6?wt%, 9?wt%, and 12?wt%) via a wet impregnation method. The XRD analysis indicates that the catalysts were amorphous with ill-defined pore systems. The XPS analysis detected the coexistence of ZnO nanoparticles together with ZnCl2 on the catalyst surface, whereas the 29Si NMR analysis indicates the formation of Si–O–Zn bond. Quantitative conversion of benzyl chloride (100%) was achieved within 3?h at 353?K when a catalyst with 9?wt% ZnCl2 was used due to its narrow pore size and high surface area (635?m2?g?1). Para- and ortho-mono-benzylated toluene was obtained as the products. The reaction is proposed to take place via weak attraction between benzyl chloride and the Zn through its chlorine atom. The catalyst was recycled four times with minimum loss (8%) in activity. The benzylation of benzene, toluene, p-xylene, and anisole followed the classical mechanism of Friedel–Craft-type acid-catalyzed benzylation reaction. The BC conversion increased in the order of toluene = p-xylene > anisole > benzene. The catalyst was also screened to be active in the benzoylation of toluene with benzoyl chloride (BOC). The conversion of BOC was 45% with selectivity toward 2-methylbenzophenone (50%) and 3-methylbenzophenone (50%).
Iqbal, Anwar,Tan, Kok-Hou,Shaari,Ahmad,Adam, Farook,Lee, Hwei Voon,Yusop, Rahimi M.,Abu Bakar,Lee, Hooi Ling,Pauzi, Hariy,Malik, Muhammad Fadhirul Izwan Abd,Jusoh, Ahmad Fadly,Wilson, Lee D.,Ahmad,Hazwan Hussain,Ibrahim, Mohamad Nasir Mohamad
p. 1615 - 1626
(2020/03/05)

Intramolecular activation of imidate with cationic gold(I) catalyst: A new benzylation reaction of alcohols
Benzylation of alcohols with benzyl (Z)-2,2,2-trifluoro-N-(2-alkynylphenyl)acetimidates 5a-f in the presence of a cationic gold(I) catalyst was investigated. Reagent 5f was the most effective, affording benzyl ethers in good yields. Our results indicate that these gold(I)-activated imidates are effective leaving groups.
Ban, Shintaro,Endo, Tomotake,Matsui, Rikako,Morita, Nobuyoshi,Hashimoto, Yoshimitsu,Tanaka, Kosaku,Tamura, Osamu
(2020/08/28)

N-heterocyclic carbene–palladium complexes for Suzuki–Miyaura coupling reaction with benzyl chloride and aromatic boronic acid leading to diarylmethanes
A family of N-heterocyclic carbene–palladium(II)–N,N-dimethylbenzylamine complexes ((NHC)LPdCl2; L?=?N,N-dimethylbenzylamine) were synthesized as well as characterized using single-crystal X-ray diffraction and spectroscopic data. These complexes exhibited higher catalytic activities for the Suzuki reaction of benzyl chlorides to afford diarylmethanes under milder conditions than other efficient (NHC)LPdCl2 complexes. Using the optimum conditions, the expected coupling products were obtained in moderate to high yields. All reactions were carried out in air and all starting materials were used as supplied without purification.
Chen, Ming-Tsz,Wang, Wan-Rong,Li, Yi-Jun
(2019/04/08)

Catalytic arene alkylation over H-Beta zeolite: Influence of zeolite shape selectivity and reactant nucleophilicity
Renewable arenes and aromatic alcohols can be derived from lignocellulose by biorefineries, which has been considered as a sustainable alternative to replace petrochemical feedstocks in the synthesis of monobenzylation products, key industrial intermediates, via benzylation reactions. Zeolites with micropores are the most widely used catalysts in the benzylation of arenes, however, their performance suffers from diffusion limitations in converting large arenes. In this work, mesoporous and microporous H–Beta zeolites were prepared and applied in the systematic study of benzylation of arenes (benzene, toluene, p-xylene and mesitylene) with benzyl alcohol (BA). The porous structure of these zeolites has been confirmed by XRD, BET and TEM techniques. The catalytically active Br?nsted acid sites (BAS) were determined by quantitative 1H magic-angle spinning (MAS) nuclear magnetic resonance (NMR) experiments. The benzylation studies have shown that introducing mesopores into H–Beta zeolites can significantly increase the diffusion/access of arenes to surface sites, particularly for bulky arenes (e.g. mesitylene), while micropores are mainly selective for the conversion of small arenes (e.g. benzene). Increasing the nucleophilicity of arenes with more alkyl groups can enhance their catalytic performance in mesopores, however, the increase hinders their conversion in micropores because of the shape selectivity due to their increasing molecular size. Compared to mesopores, micropores promote the conversion of small arenes (e.g. benzene), which can be additionally enhanced by a high Br?nsted acidity. Therefore, introducing a suitable porosity balanced with acidity are keys in the tailoring of the catalytic performance of H-Beta zeolites for target benzylation reactions.
Zeng, Xin,Wang, Zichun,Ding, Jia,Wang, Leizhi,Jiang, Yijiao,Stampfl, Catherine,Hunger, Michael,Huang, Jun
p. 9 - 20
(2019/10/19)

Green, Mild, and Efficient Friedel–Crafts Benzylation of Scarcely Reactive Arenes and Heteroarenes under On-Water Conditions
Metal-free Friedel–Crafts benzylation (FCB) of scarcely reactive arenes and heteroarenes was performed under on-water conditions by an environmentally sustainable procedure. The catalytic strategy exploits the hydrophobicity of the resorcinarene macrocycle 1 a. The proposed mechanism is based on the activation of benzyl chloride by H-bonding interactions with catalyst 1 a. In fact, under on-water conditions the hydrophobic amplification of the strength of the H-bonding interactions between the OH groups of the resorcinarene catalyst and the chlorine atom of benzyl chloride leads to polarization of the C?Cl bond, which consequently promotes electrophilic attack of the π nucleophile. Thus, many arenes and heteroarenes were efficiently benzylated under mild on-water conditions by using resorcinarene 1 a as catalyst. The FCB of benzene is industrially relevant for the synthesis of diphenylmethane, and hence the on-water procedure was extended to the gram-scale synthesis of diphenylmethane, starting from benzene and benzyl chloride in the presence of resorcinarene catalyst 1 a.
La Manna, Pellegrino,Soriente, Annunziata,De Rosa, Margherita,Buonerba, Antonio,Talotta, Carmen,Gaeta, Carmine,Neri, Placido
p. 1673 - 1683
(2019/03/26)

Phosphonic acid mediated practical dehalogenation and benzylation with benzyl halides
For the first time, by using H3PO3/I2 system, various benzyl chlorides, bromides and iodides were dehalogenated successfully. In the presence of H3PO3, benzyl halides underwent electrophilic substitution reactions with electron-rich arenes, leading to a broad range of diarylmethanes in good yields. These transformations feature green, cheap reducing reagents and metal-free conditions. A possible mechanism was proposed.
Gao, Jing,Han, Li-Biao,Ma, Yonghao,Tang, Zilong,Wu, Xiaofang,Xiao, Jing
p. 22343 - 22347
(2019/07/31)

Carbonyl and olefin hydrosilylation mediated by an air-stable phosphorus(iii) dication under mild conditions
The readily-accessible, air-stable Lewis acid [(terpy)PPh][B(C6F5)4]21 is shown to mediate the hydrosilylation of aldehydes, ketones, and olefins. The utility and mechanism of these hydrosilylations are considered.
Andrews, Ryan J.,Chitnis, Saurabh S.,Stephan, Douglas W.
supporting information
p. 5599 - 5602
(2019/05/21)

Super electron donor-mediated reductive desulfurization reactions
The desulfurization of thioacetals and thioethers by a pyridine-derived electron donor is described. This methodology provides efficient access to the reduced products in high yields and does not require the use of transition-metals, elemental alkali-metals, or hydrogen atom donors.
Nozawa-Kumada, Kanako,Ito, Shungo,Noguchi, Koto,Shigeno, Masanori,Kondo, Yoshinori
p. 12968 - 12971
(2019/11/05)

Gold-catalyzed cyclization of enediynes and arenediynes to 6H-benzo[c]chromen-6-one and dibenzo[c,h]chromen-6-one derivatives
The efficient synthesis of 6H-benzo[c]chromen-6-one and dibenzo[c,h]chromen-6-one derivatives is described. Thus, treatment of arenediynes 1 and enediynes 5 with 5 mol % Ph3PAuCl and 10 mol % of AgSbF6 in refluxing toluene gave dibenzo[c,h]chromen-6-ones 4 and 6H-benzo[c]chromen-6-ones 6, in good yields, respectively.
Chen, Chin-Chau,Hsu, Chia-Ling,Wu, Ming-Jung
p. 1034 - 1043
(2019/01/26)

Palladium-Catalyzed Hiyama Coupling of Benzylic Ammonium Salts via C-N Bond Cleavage
The first palladium-catalyzed Hiyama cross-coupling of arylsilanes with benzyltrimethylammonium salts is reported. The reaction proceeds smoothly to facilitate C(sp2)-C(sp3) bond formation via cleavage of the C-N bond and provides a useful approach to various diarylmethanes with a broad substrate scope and excellent functional group tolerance in good to excellent yields.
Han, Chunyu,Zhang, Zhenming,Xu, Silin,Wang, Kai,Chen, Kaiting,Zhao, Junfeng
p. 16308 - 16313
(2019/12/25)

Novel rhodium on carbon catalysts for the oxidation of benzyl alcohol to benzaldehyde: A study of the modification of metal/support interactions by acid pre-treatments
Rhodium nanoparticles or rhodium organometallic complexes are mainly used in catalysis for reduction or hydroformylation reactions. In this work instead, we explored the capabilities of Rh nanoparticles as an oxidation catalyst, applied to the oxidation o
Wilde, Conor A.,Ryabenkova, Yulia,Firth, Ian M.,Pratt, Liam,Railton, James,Bravo-Sanchez, Mariela,Sano, Naoko,Cumpson, Peter J.,Coates, Phil D.,Liu, Xi,Conte, Marco
p. 271 - 282
(2018/12/11)

Cross coupling of benzylammonium salts with boronic acids using a well-defined N-heterocyclic carbene-palladium(ii) precatalyst
N-heterocyclic carbene-palladium(ii)-catalyzed cross-coupling of benzylammonium salts with arylboronic acids for the synthesis of diarylmethane derivatives via C-N bond activation has been developed. Notably, in the presence of the easily prepared and bench-stable Pd-PEPPSI precatalyst, the Csp3-N bond activation of the benzylammonium salt even proceeded smoothly in isopropanol at room temperature.
Wang, Tao,Guo, Jiarui,Wang, Xiaojuan,Guo, Han,Jia, Dingli,Wang, Hengjin,Liu, Lantao
p. 5738 - 5741
(2019/03/02)

The Dual Role of Benzophenone in Visible-Light/Nickel Photoredox-Catalyzed C?H Arylations: Hydrogen-Atom Transfer and Energy Transfer
A dual catalytic protocol for the direct arylation of non-activated C(sp3)?H bonds has been developed. Upon photochemical excitation, the excited triplet state of a diaryl ketone photosensitizer abstracts a hydrogen atom from an aliphatic C?H bond. This inherent reactivity was exploited for the generation of benzylic radicals which subsequently enter a nickel catalytic cycle, accomplishing the benzylic arylation.
Dewanji, Abhishek,Krach, Patricia E.,Rueping, Magnus
supporting information
p. 3566 - 3570
(2019/02/26)

Ni(NIXANTPHOS)-Catalyzed Mono-Arylation of Toluenes with Aryl Chlorides and Bromides
A nickel-catalyzed cross-coupling of toluene derivatives with both aryl bromides and chlorides using a NIXANTPHOS-ligated nickel(II) complex has been developed. The key factor to success is proposed to be the catalyst activation of toluene by a cation-π complex, enabling methyl arenes (pKa ≈ 43) to be deprotonated with the relatively mild base NaN(SiMe3)2. This method facilitates access to a variety of sterically and electronically diverse hetero- and nonheteroaryl-containing diarylmethanes.
Jiang, Hui,Sha, Sheng-Chun,Jeong, Soo A,Manor, Brian C.,Walsh, Patrick J.
supporting information
p. 1735 - 1739
(2019/03/20)

Preparation and application of blended nickel (II) complex with bisoxazoline derived azacyclo-carbene ligand and phosphite ester ligand
The invention discloses a blended nickel (II) complex with a bisoxazoline derived azacyclo-carbene ligand and a phosphite ester ligand and application of the blended nickel (II) complex. The blended nickel (II) complex has a chemical formula of Ni(NHC)[P(OR)3]X2, in the formula, R is one of ethyl or isopropyl; X is one of bromine atoms or helium atoms; and NHC is the bisoxazoline derived azacyclo-carbene ligand. In the presence of magnesium chips, the blended nickel (II) complex with the bisoxazoline derived azacyclo-carbene ligand and the phosphite ester ligand, which is disclosed by the invention, is capable of catalyzing aromatic hydrocarbon or fluoro-aromatic hydrocarbon with low activity to have a reduction cross coupling reaction with a benzyl chloride type compound at a single temperature, then a diarylmethane compound can be generated at one step, and a novel method is provided for synthesizing diarylmethane compounds.
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(2019/10/17)

Nickel-catalyzed cross-coupling of aldehydes with aryl halides: Via hydrazone intermediates
Traditional cross-couplings require stoichiometric organometallic reagents. A novel nickel-catalyzed cross-coupling reaction between aldehydes and aryl halides via hydrazone intermediates has been developed, merging the Wolff-Kishner reduction and the classical cross-coupling reactions. Aromatic aldehydes, aryl iodides and aryl bromides are especially effective in this new cross-coupling chemistry.
Tang, Jianting,Lv, Leiyang,Dai, Xi-Jie,Li, Chen-Chen,Li, Lu,Li, Chao-Jun
p. 1750 - 1753
(2018/02/21)

Nickel-Catalyzed Cross-Electrophile Coupling between Benzyl Alcohols and Aryl Halides Assisted by Titanium Co-reductant
A nickel-catalyzed cross-electrophile coupling reaction between benzyl alcohols and aryl halides has been developed using a homolytic C-O bond cleavage protocol that has recently been established. The treatment of a benzyl alcohol and aryl halide with a nickel catalyst and low-valent titanium reagent generated from TiCl4(lutidine) (lutidine = 2,6-lutidine) and manganese powder afforded the cross-coupled product in high yield. A mechanistic study indicated the intermediacy of the benzyl radicals that originate from the benzyl alcohols.
Suga, Takuya,Ukaji, Yutaka
p. 7846 - 7850
(2019/01/14)

Dinuclear NHC–palladium(II) complexes: synthesis,characterization and application to Suzuki–Miyaura cross-coupling reactions
Abstract: Four dinuclear N-heterocyclic carbene–palladium(II) complexes 1–4 were prepared and characterized by elemental analysis and spectroscopic methods. The X-ray crystal structure of complex 2 showed a dinuclear framework in which N-heterocyclic ligands bridge between two square planar palladium(II) units. Each palladium center is surrounded by an imidazolylidene, a nitrogen atom from the central linking ligand, and two trans-chloride ligands. These dinuclear NHC–palladium(II) complexes exhibited efficient catalytic activities for the Suzuki–Miyaura coupling of aryl and benzyl chlorides with arylboronic acids.
Wang, Tao,Xu, Kai,Wang, Wanli,Zhang, Anan,Liu, Lantao
p. 347 - 353
(2018/03/23)

Substrate switchable Suzuki-Miyaura coupling for benzyl ester: Vs. benzyl halide
Two reaction conditions were developed to accomplish the substrate switchable Suzuki-Miyaura coupling of benzyl derivatives and arylboronic acid derivatives. Under conditions for esters, benzyl esters such as carbonates and acetates reacted with arylboronic acids to afford the corresponding diarylmethanes. However, the benzyl halides did not react under the same conditions. On the other hand, benzyl halides such as bromides and chlorides furnished diarylmethanes under conditions for halides, under which benzyl ester substrates did not react, in which water was found to play an important role. This switching system was tested using the intermolecular/intramolecular competitive reactions, during which the desired products could be synthesized by selecting the appropriate reaction conditions.
Ohsumi, Masato,Ito, Akitaka,Nishiwaki, Nagatoshi
p. 35056 - 35061
(2018/10/24)

Benzylation with Benzyl Alcohol Catalyzed By [ChCl][TfOH]2, a Br?nsted Acidic DES with Reaction Control Self-Separation Performance
Abstract: A deep eutectic solvent with strong Br?nsted acidity was prepared easily by choline chloride and trifluoromethanesulfonic acid. The obtained [ChCl][TfOH]2 catalyst which was characterized by FT-IR, 1H NMR and TG, possessed greatly enhanced stability than trifluoromethanesulfonic acid, and exhibited excellent catalytic performance in benzylation with benzyl alcohol. Especially, the prepared [ChCl][TfOH]2 catalyst could dissolve into the reactants to realize homogeneous catalysis, and then self-separate from the organic phase after reaction due to the entire consumption of benzyl alcohol. As a result, the catalyst could be recovered and reused simply for six-runs without noticeable loss of catalytic performance. Graphical Abstract: [Figure not available: see fulltext.].
Yuan, Bing,Li, Yinglian,Yu, Fengli,Li, Xiaoqiang,Xie, Congxia,Yu, Shitao
p. 2133 - 2138
(2018/05/29)

Bisulfate Salt-Catalyzed Friedel-Crafts Benzylation of Arenes with Benzylic Alcohols
We report here a method of direct Friedel-Crafts benzylation of arenes with benzylic alcohols using cheap and readily available bisulfate salt as the catalyst in hexafluoroisopropanol. The catalytic system is powerful with a quite diverse group of functionalized arenes and benzylic alcohols. These mild conditions provide a straightforward synthesis of a variety of unsymmetrical diarylmethanes in high yield with good to high regioselectivity. An SN1 mechanism involving activation of the hydroxy group through a hydrogen bond is proposed.
Tang, Ren-Jin,Milcent, Thierry,Crousse, Benoit
p. 14001 - 14009
(2018/11/23)

Mild Friedel–Crafts Reactions inside a Hexameric Resorcinarene Capsule: C?Cl Bond Activation through Hydrogen Bonding to Bridging Water Molecules
A novel catalytic feature of a hexameric resorcinarene capsule is highlighted. The self-assembled cage was exploited to promote the Friedel–Crafts benzylation of several arenes and heteroarenes with benzyl chloride under mild conditions. Calculations showed that there are catalytically relevant hydrogen-bonding interactions between the bridging water molecules of the capsule and benzyl chloride, which is fundamental for the activation of the C?Cl bond. The capsule controls the reaction outcome. Inside the inner cavity of the capsule, N-methylpyrrole is preferentially benzylated in the unusual β-position while mesitylene reacts faster than 1,3-dimethoxybenzene despite the greater π-nucleophilicity of the latter compound.
La Manna, Pellegrino,Talotta, Carmen,Floresta, Giuseppe,De Rosa, Margherita,Soriente, Annunziata,Rescifina, Antonio,Gaeta, Carmine,Neri, Placido
p. 5423 - 5428
(2018/04/09)

Chlorotrimethylsilane and Sodium Iodide: A Remarkable Metal-Free Association for the Desulfurization of Benzylic Dithioketals under Mild Conditions
A novel metal-free process allowing the reductive desulfurization of various benzylic dithioketals to afford diarylmethane and benzylester derivatives with good to excellent yields is reported. At room temperature, this mild reduction process requires only the use of TMSCl and NaI in CH2Cl2 and tolerates a large variety of functional groups. (Figure presented.).
Zhao, Guangkuan,Yuan, Ling-Zhi,Alami, Mouad,Provot, Olivier
p. 2522 - 2536
(2018/05/14)

Cross-Coupling of Phenol Derivatives with Umpolung Aldehydes Catalyzed by Nickel
A nickel-catalyzed cross-coupling to construct the C(sp2)-C(sp3) bond was developed from two sustainable biomass-based feedstocks: phenol derivatives with umpolung aldehydes. This strategy features the in situ generation of moisture/air-stable hydrazones from naturally abundant aldehydes, which act as alkyl nucleophiles under catalysis to couple with readily available phenol derivatives. The avoidance of using both halides as the electrophiles and organometallic or organoboron reagents (also derived from halides) as the nucleophiles makes this method more sustainable. Water tolerance, great functional group (ketone, ester, free amine, amide, etc.) compatibility, and late-stage elaboration of complex biological molecules exemplified its practicability and unique chemoselectivity over organometallic reagents.
Lv, Leiyang,Zhu, Dianhu,Tang, Jianting,Qiu, Zihang,Li, Chen-Chen,Gao, Jian,Li, Chao-Jun
p. 4622 - 4627
(2018/05/22)

Transition-Metal-Free Synthesis of Biarylmethanes from Aryl Iodides and Benzylic Ketones
An original metal-free procedure for the synthesis of biarylmethanes is disclosed herein. The reactions occur with high selectivity starting from aryl iodides and benzylic ketones in the presence of superbasic media (CsOH/DMSO). This procedure allows a straightforward access to a wide range of biarylmethane derivatives substituted with electron-withdrawing and -donating substituents.
Pichette Drapeau, Martin,Tlili, Anis,Zaid, Yassir,Toummini, Dounia,Ouazzani Chahdi, Fouad,Sotiropoulos, Jean-Marc,Ollevier, Thierry,Taillefer, Marc
supporting information
p. 17449 - 17453
(2018/11/10)

MoO3 supported on ordered mesoporous zirconium oxophosphate: An efficient and reusability solid acid catalyst for alkylation and esterification
A series of molybdenum oxide supported on ordered mesoporous zirconium oxophosphate (MoO3/M-ZrPO) materials with different MoO3 loadings (0–20 wt%) and calcination temperatures (500–900 °C) have been designed, synthesized and employed as solid acid catalysts in alkylation and esterification. The XRD, TG-DSC, H2-TPR, N2-physisorption and TEM characterizations were taken to investigate the structural properties and states of introduced MoO3 species. The influence of MoO3 loadings and calcination temperatures in catalytic performance was detailedly investigated and optimal catalytic activity was reached at 10 wt% MoO3 loadings and treated at 700 °C. Moreover, MoO3/M-ZrPO catalysts exhibited outstanding catalytic performance in Friedel-Crafts alkylation of different aromatic compounds and esterification of levulinic acid with 1-butanol. Furthermore, it was noteworthy that the catalyst had superior reusability and no noticeable declines were observed in catalytic performance even after seven runs.
Miao, Zhichao,Li, Zhenbin,Zhao, Jinping,Si, Weijiang,Zhou, Jin,Zhuo, Shuping
p. 10 - 21
(2017/12/06)

An efficient class of bis-NHC salts: Applications in Pd-catalyzed reactions under mild reaction conditions
This study describes an efficient class of bis-N-heterocyclic carbene (bis-NHC) salts that can be easily made from commercially available and inexpensive starting materials. The application of these salts to Pd-catalyzed reactions is described. The palladium (Pd) catalyst generated in situ was highly effective under mild reaction conditions.
Chiu, Chien-Cheng,Chiu, Hui-Tzu,Lee, Dong-Sheng,Lu, Ta-Jung
p. 26407 - 26415
(2018/08/04)

Cation-π Interactions in the Benzylic Arylation of Toluenes with Bimetallic Catalysts
A method to directly arylate toluene derivatives with aryl bromides to generate diarylmethanes, which are important building blocks in drug discovery, is described. In this method, KN(SiMe3)2 in combination with a (NIXANTPHOS)Pd catalyst accomplished the deprotonative activation of toluene derivatives to permit cross-coupling with aryl bromides. Good to excellent yields are obtained with a range of electron-rich to neutral aryl bromides. Both electron-rich and electron-poor toluene derivatives are well tolerated, and even 2-chlorotoluene performs well, providing a platform for introduction of additional functionalization. This discovery hinges on the use of a main group metal to activate toluene for deprotonation by means of a cation-π interaction, which is secured by a bimetallic K(NIXANTPHOS)Pd assembly. Mechanistic and computational studies support acidification of toluene derivatives by the K+-cation- π interaction, which may prove pertinent in the development of other, new reaction systems.
Sha, Sheng-Chun,Tcyrulnikov, Sergei,Li, Minyan,Hu, Bowen,Fu, Yue,Kozlowski, Marisa C.,Walsh, Patrick J.
supporting information
p. 12415 - 12423
(2018/10/02)

Palladium-Catalysed Cross-Coupling of Benzylammonium Salts with Boronic Acids under Mild Conditions
Herein, we give a full account of the development of the palladium-catalysed cross-coupling of benzylammonium salts with boronic acids. A range of benzylamine-derived quaternary ammonium salts can be coupled with boronic acids under relatively mild conditions. Our optimization has identified ligands that can be used to chemoselectively cross-couple at the ammonium in the presence of chlorides. We demonstrate that intramolecular palladium-catalysed C-H activation is also a viable pathway for the putative benzyl-Pd(II) intermediate obtained upon oxidative addition and have optimised this to obtain fluorene in good yield.
Türtscher, Paul L.,Davis, Holly J.,Phipps, Robert J.
p. 793 - 803
(2017/10/07)

New bio-nanocomposites based on iron oxides and polysaccharides applied to oxidation and alkylation reactions
Polysaccharides from natural sources and iron precursors were applied to develop new bio-nanocomposites by mechanochemical milling processes. The proposed methodology was demonstrated to be advantageous in comparison with other protocols for the synthesis of iron oxide based nanostructures. Additionally, mechanochemistry has enormous potential from an environmental point-of-view since it is able to reduce solvent issues in chemical syntheses. The catalytic activity of the obtained nanocatalysts was investigated in both the oxidation of benzyl alcohol to benzaldehyde and in the alkylation of toluene with benzyl chloride. The microwave-assisted oxidation of benzyl alcohol reached 45% conversion after 10 min. The conversion of the alkylation of toluene in both microwave-assisted and conventional heating methods was higher than 99% after 3 min and 30 min, respectively. The transformation of benzyl alcohol and toluene into valuable product in both the oxidation and alkylation reaction reveals a potential method for the valorization of lignocellulosic biomass.
Rodríguez-Padrón, Daily,Balu, Alina M,Romero, Antonio A,Luque, Rafael
p. 1982 - 1993
(2017/10/16)

Core-shell zeolite y with ant-nest like hollow interior constructed by amino acids and enhanced catalytic activity
Core-shell zeolite Y containing an ant-nest like hollow interior has been synthesized in the presence of natural amino acids. Time-resolved characterization of zeolite samples revealed the gradual development of three-dimensionally interconnected mesoporous channels via an intermediate stage of spatially aligned cavities in the core, which did not follow either a classical or a reversed crystal growth route. Comparative experiments suggested coordinative construction actions of amino acids, the interpenetration of which into the internal weak points of the aluminosilicate framework takes place simultaneously with zeolite crystallization. At the point of complete zeolite growth, amino acids in aggregated domains begin disassembling the zeolite interior forming a network of channels while maintaining the external zeolite shell thickness of 165 nm and morphologically similar to conventional faujasite. The core-shell zeolite Y samples exhibit superior crystallinity and enhanced catalytic activity for Friedel-Crafts benzylation of toluene.
Zhang, Jian,Bai, Shan,Chen, Zhuwen,Wang, Yanding,Dong, Lei,Zheng, Hairong,Cai, Feiyan,Hong, Mei
p. 20757 - 20764
(2017/10/16)

Effect of the nature of sulfur compounds on their reactivity in the oxidative desulfurization of hydrocarbon fuels with oxygen over a modified CuZnAlO catalyst
The reactivity of thiophene, dibenzothiophene (DBT), and 4,6-dimethyldibenzothiophene (4,6-DMDBT), which are the representatives of the main classes of sulfur compounds that are the constituents of diesel fractions, was studied in the course of their oxidative desulfurization with oxygen on a CuO/ZnO/Al2O3 catalyst modified with boron and molybdenum additives. At T ≥ 375°C, the reactivity increased in the order thiophene 2 from hydrocarbon fuel, which was simulated by a solution of 4,6-DMDBT in toluene, was 80%. Under the assumption of a first order reaction with respect to sulfur compound and oxygen, the apparent activation energies of the test processes were calculated. An attempt was made to reveal the role of the adsorption of sulfur compounds in the overall process of oxidative desulfurization with the use of X-ray diffraction analysis, X-ray photoelectron spectroscopy, and differential thermal and thermogravimetric analysis with the massspectrometric monitoring of gas phase composition.
Yashnik,Salnikov,Kerzhentsev,Saraev,Kaichev,Khitsova,Ismagilov,Yamin,Koseoglu
p. 58 - 72
(2017/03/11)

Synthetic method of diarylmethanes
The invention discloses a synthetic method of diarylmethanes. The method is characterized in that benzyl pseudohalide and aromatic boric acid are reacted in an organic solvent under alkaline condition. The method employs easily available raw materials, conversion is realized under effect of no transition metal catalysis, water-free and oxygen-free are not required, Lewis acid catalysis is not required, the method has wide substrate universality, and various substituted diarylmethanes can be synthesized by the method.
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Paragraph 0166; 0167; 0168; 0169; 0170

(2017/08/28)

Cooperative Al-H Bond Activation in DIBAL-H: Catalytic Generation of an Alumenium-Ion-Like Lewis Acid for Hydrodefluorinative Friedel-Crafts Alkylation
The Ru-S bond in Ohki-Tatsumi complexes breaks oligomeric DIBAL-H structures into their more reactive monomer. That deaggregation is coupled to heterolytic Al-H bond activation at the Ru-S bond, formally splitting the Al-H linkage into hydride and an alumenium ion. The molecular structure of these Lewis pairs was established crystallographically, revealing an additional Ru-Al interaction next to the Ru-H and Al-S bonds. That bonding situation was further analyzed by quantum-chemical calculations and is best described as a three-center-two-electron (3c2e) donor-acceptor σ(Ru-H) → Al interaction. Despite the extra stabilization of the aluminum center by the interaction with both the sulfur atom and the Ru-H bond, the hydroalane adducts are found to be stronger Lewis acids and electrophiles than the free ruthenium catalyst and DIBAL-H in its different aggregation states. Hence, the DIBAL-H molecule and its Al-H bond are activated by the Ru-S bond, but these hydroalane adducts are not to be mistaken as sulfur-stabilized alumenium ions in a strict sense. The Ohki-Tatsumi complexes catalyze C(sp3)-F bond cleavage with DIBAL-H, and the catalytic setup is applied to hydrodefluorinative Friedel-Crafts alkylations. A broad range of CF3-substituted arenes is efficiently converted into unsymmetrical diarylmethanes with various arenes as nucleophiles. Computed fluoride-ion affinities (FIAs) of the hydroalane adducts as well as DIBAL-H in its aggregation states support this experimental finding.
Forster, Francis,Mets?nen, Toni T.,Irran, Elisabeth,Hrobárik, Peter,Oestreich, Martin
supporting information
p. 16334 - 16342
(2017/11/22)

A Zwitterionic Palladium(II) Complex as a Precatalyst for Neat-Water-Mediated Cross-Coupling Reactions of Heteroaryl, Benzyl, and Aryl Acid Chlorides with Organoboron Reagents
The Suzuki–Miyaura cross-coupling (SMC) reactions of several heteroaryl chlorides, benzyl chlorides, and aryl acid chlorides with (hetero)arylboron reagents have been investigated in the presence of [Pd(HL1)(PPh3)Cl2] (I) [HL1 = 3-[(2,6-diisopropylphenyl)-1-imidazolio]-2-quinoxalinide] as catalyst and K2CO3 as base in neat water. The synthesis of the heterocycle-containing biaryls required the addition of 2 mol-% of a phosphine ligand (PPh3 or X-Phos). A combination of more than 115 substrates were screened and it was found that I is a versatile catalyst that can produce heterocycle-containing biaryls, diarylmethanes, and benzophenones in moderate-to-excellent yields.
Ramakrishna, Visannagari,Rani, Morla Jhansi,Reddy, Nareddula Dastagiri
p. 7238 - 7255
(2018/01/01)

Development of Versatile Sulfone Electrophiles for Suzuki-Miyaura Cross-Coupling Reactions
The development of fluorinated sulfone derivatives as versatile electrophiles for Suzuki-Miyaura cross-coupling reactions is described. Introducing electron-withdrawing groups on the aryl ring of the sulfone facilitates the Pd-catalyzed activation of C-SO2 bonds. Cross-coupling reactions with fluorinated sulfone electrophiles are reported, leading to a variety of multiply arylated products in good yields. The reactivity of this unusual electrophile is benchmarked versus common electrophiles and its use in iterative cross-couplings for concise synthesis of biologically active molecules is described.
Nambo, Masakazu,Keske, Eric C.,Rygus, Jason P. G.,Yim, Jacky C.-H.,Crudden, Cathleen M.
p. 1108 - 1112
(2017/08/09)

Method for catalytic synthesis of benzyl toluene by activated clay-loaded ferric trichloride (FeCl3) solid acid catalyst
The invention relates to a method for catalytic synthesis of benzyl toluene by an activated clay-loaded ferric trichloride (FeCl3) solid acid catalyst. The method comprises the following steps: adding calcium-based bentonite with concentrated sulfuric acid, performing backflow stirring and drying to obtain solid activated clay; dissolving the FeCl3 in an acetonitrile solution, adding the prepared activated clay, stirring for 24 hours at a room temperature, filtering and activating at a temperature of 120 DEG C to obtain the activated clay-loaded FeCl3 solid acid catalyst; adding the activated clay-loaded FeCl3 solid acid catalyst in an alkylation reaction system of benzyl chloride and toluene for catalytic reaction, filtering and recovering the catalyst; performing reduced-pressure distillation and refinement on a benzyl toluene crude product to obtain benzyl toluene. The method provided by the invention has the advantages that the catalyst is rich in raw material source, low in cost, simple in preparation process, low in energy consumption due to no need of high temperature activation and easy for separation from the product; when the catalyst is used for the synthetic reaction of the benzyl toluene, the reaction conversion rate is high, the selectivity is strong, conditions are mild, the equipment corrosion is low, the catalyst is easy to recover and can be reused, and the environment pollution is less, so that the application prospect is wide.
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Paragraph 0018; 0019; 0020

(2017/08/29)

Feedstocks to Pharmacophores: Cu-Catalyzed Oxidative Arylation of Inexpensive Alkylarenes Enabling Direct Access to Diarylalkanes
A Cu-catalyzed method has been identified for selective oxidative arylation of benzylic C-H bonds with arylboronic esters. The resulting 1,1-diarylalkanes are accessed directly from inexpensive alkylarenes containing primary and secondary benzylic C-H bonds, such as toluene or ethylbenzene. All catalyst components are commercially available at low cost, and the arylboronic esters are either commercially available or easily accessible from the commercially available boronic acids. The potential utility of these methods in medicinal chemistry applications is highlighted.
Vasilopoulos, Aristidis,Zultanski, Susan L.,Stahl, Shannon S.
p. 7705 - 7708
(2017/06/20)

Synthesis and characterization of trinuclear N-heterocyclic carbene-palladium(II) complexes and their applications in the Suzuki-Miyaura cross-coupling reaction
Five novel trinuclear N-heterocyclic carbene-palladium(ii) complexes 5a-e were conveniently synthesized through one-pot reactions of imidazolium salts, tridentate N-heterocycles {tris(4-(pyridin-4-yl)phenyl)amine or tris(4-(pyridin-3-yl)phenyl)amine} and palladium chloride in one step. All of the new complexes have been fully characterized by elemental analysis, 1H, 13C NMR, and IR spectra. Among them, the molecular structures of complex 5d have been determined by X-ray single-crystal diffraction. Moreover, the obtained trinuclear palladium(ii) complexes were the effective catalyst precursors for the Suzuki-Miyaura coupling of aryl as well as benzyl chlorides with arylboronic acids. Under the optimal reaction conditions, the expected biaryl products were obtained in good to almost quantitative yields.
Wang, Tao,Liu, Lantao,Xu, Kai,Xie, Huanping,Shen, Hui,Zhao, Wen-Xian
p. 100690 - 100695
(2016/11/09)

Synthesis and catalytic reactivity of mononuclear substituted tetramethylcyclopentadienyl molybdenum carbonyl complexes
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
p. 225 - 233
(2016/02/20)

Synthesis and catalytic activity of monobridged bis(cyclopentadienyl)rhenium carbonyl complexes
Thermal treatment of three monobridged biscyclopentadienes (C5H5)R(C5H5) [R?=?C(CH3)2 (1), C(CH2)5 (2), Si(CH3)2 (3)] with Re2(CO)10 in refluxing mesitylene gave the corresponding complexes [(η5-C5H4)2R][Re(CO)3]2 [R?=?C(CH3)2 (4), C(C5H10) (5), Si(CH3)2 (6)], which were separated by chromatography, and characterized by elemental analysis, IR, and 1H NMR spectroscopy. The molecular structures of complexes 5 and 6 were characterized by X-ray crystal diffraction analysis and show that both are monobridged bis(cyclopentadienyl)rhenium carbonyl complexes in which the molecule consists of two [(η5-C5H4)Re(CO)3] moieties linked by a single bridge, in which each of the two Re(CO)3 units is coordinated to the cyclopentadienyl ring in an η5 mode. All three of these monobridged bis(cyclopentadienyl)rhenium carbonyl complexes have good catalytic activities in Friedel–Crafts alkylation reactions.
Li, Zhen,Ma, Zhi-Hong,Wang, Hong,Han, Zhan-Gang,Zheng, Xue-Zhong,Lin, Jin
p. 647 - 653
(2016/07/29)