- Preparation and use of tritiated Schwartz' reagent (ZrCp2Cl3H)
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Treatment of Li3H with ZrCp2Cl2 in THF affords ZrCp2Cl3H. By the action of ZrCp2Cl3H on an acetylene, it is possible to stereo- and regioselectively introduce tritium into the vinylic position, a site which has often proved to be metabolically stable in complex molecules. In addition, ZrCp2Cl3H may be used to regioselectively label olefins with tritium.
- Zippi,Andres,Morimoto,Williams
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Read Online
- Thermodynamics and kinetics of formation of intramolecular naphthalene dimer radical cation studied by near-IR transient absorption spectroscopy
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Thermodynamics and kinetics for formation of an intramolecular dimer radical cation of a series of α,ω-di(2-naphthyl)alkanes in solutions were quantitatively investigated by near-IR transient absorption spectroscopy, which allows one to observe dimer radical cations directly. The standard enthalpy (-ΔH°) for the formation of the intramolecular dimer radical cation increased as the chain length between the two naphthyl moieties increased, and was smaller than that of the intermolecular dimer radical cation of 2-ethylnaphthalene. This shows that -ΔH° depends on the strain required for the chain to form the ring-closure configuration. Destabilization due to repulsion between the two naphthyl moieties in the intramolecular dimer radical cation was evaluated to be ca. 20 kJ mol-1. This value is smaller than that of the naphthalene excimer, indicating that the separation distance and/or the overlap between the two naphthyl moieties are not as restricted as those of the excimer. The activation energy for the formation of the intramolecular dimer radical cation was comparable to the energy for local motions of a few methylene units linking the two naphthalene moieties.
- Fushimi, Toshiki,Fujita, Yusuke,Ohkita, Hideo,Ito, Shinzaburo
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Read Online
- Expanding the useful range of ionic liquids: Melting point depression of organic salts with carbon dioxide for biphasic catalytic reactions
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Large and previously unreported melting point depressions (even exceeding ΔTm of 100°C) were observed for simple ammonium and phosphonium salts in the presence of compressed CO2, bringing them well within the range of typical ionic liquids; possible applications include biphasic catalysis in IL/scCO2 systems as demonstrated for rhodium complex catalyzed hydrogenation, hydroformylation, and hydroboration of 2-vinyl-naphthalene using a CO2-induced molten sample of [NBu 4][BF4] as a catalyst phase at temperatures in the range of 55-75°C, i.e. 100°C below the normal melting point of the organic salt. The Royal Society of Chemistry 2006.
- Scurto, Aaron M.,Leitner, Walter
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- Attenuation of Ni(0) Decomposition: Mechanistic Insights into AgF-Assisted Nickel-Mediated Silylation
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In nickel-mediated Kumada cross-coupling reactions, low valent active nickel complexes are often generated in situ and the ligands usually govern the reactivity or stability of these complexes. However, the decomposition of active nickel complexes is inev
- Balakrishnan, Venkadesh,Chindan, Bincy,Murugesan, Vetrivelan,Rasappan, Ramesh
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p. 1438 - 1446
(2022/01/27)
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- Sustainable System for Hydrogenation Exploiting Energy Derived from Solar Light
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Herein described is a sustainable system for hydrogenation that uses solar light as the ultimate source of energy. The system consists of two steps. Solar energy is captured and chemically stored in the first step; exposure of a solution of azaxanthone in ethanol to solar light causes an energy storing dimerization of the ketone to produce a sterically strained 1,2-diol. In the second step, the chemical energy stored in the vicinal diol is released and used for hydrogenation; the diol offers hydrogen onto alkenes and splits back to azaxanthone, which is easily recovered and reused repeatedly for capturing solar energy.
- Ishida, Naoki,Kamae, Yoshiki,Ishizu, Keigo,Kamino, Yuka,Naruse, Hiroshi,Murakami, Masahiro
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supporting information
p. 2217 - 2220
(2021/02/16)
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- Ligand-enabled and magnesium-activated hydrogenation with earth-abundant cobalt catalysts
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Replacing expensive noble metals like Pt, Pd, Ir, Ru, and Rh with inexpensive earth-abundant metals like cobalt (Co) is attracting wider research interest in catalysis. Cobalt catalysts are now undergoing a renaissance in hydrogenation reactions. Herein, we describe a hydrogenation method for polycyclic aromatic hydrocarbons (PAHs) and olefins with a magnesium-activated earth-abundant Co catalyst. When diketimine was used as a ligand, simple and inexpensive metal salts of CoBr2in combination with magnesium showed high catalytic activity in the site-selective hydrogenation of challenging PAHs under mild conditions. Co-catalyzed hydrogenation enabled the reduction of two side aromatics of PAHs. A wide range of PAHs can be hydrogenated in a site-selective manner, which provides a cost-effective, clean, and selective strategy to prepare partially reduced polycyclic hydrocarbon motifs that are otherwise difficult to prepare by common methods. The use of well-defined diketimine-ligated Co complexes as precatalysts for selective hydrogenation of PAHs and olefins is also demonstrated.
- Han, Bo,Jiao, Hongmei,Ma, Haojie,Wang, Jijiang,Zhang, Miaomiao,Zhang, Yuqi
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p. 39934 - 39939
(2021/12/31)
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- Efficient synthesis of quinazolines by the iron-catalyzed acceptorless dehydrogenative coupling of (2-aminophenyl)methanols and benzamides
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The acceptorless dehydrogenation coupling (ADC) of (2-aminophenyl)methanols with benzamides was achieved with catalytic FeCl2·4H2O in an efficient synthesis of quinazolines. This simple catalytic system is atom-economical, environmentally benign and suited to a variety of substrates.
- Zhang, Shi-Qi,Cui, Yao,Guo, Bin,Young, David J.,Xu, Ze,Li, Hong-Xi
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- Chemoselective Hydrogenation of Olefins Using a Nanostructured Nickel Catalyst
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The selective hydrogenation of functionalized olefins is of great importance in the chemical and pharmaceutical industry. Here, we report on a nanostructured nickel catalyst that enables the selective hydrogenation of purely aliphatic and functionalized olefins under mild conditions. The earth-abundant metal catalyst allows the selective hydrogenation of sterically protected olefins and further tolerates functional groups such as carbonyls, esters, ethers and nitriles. The characterization of our catalyst revealed the formation of surface oxidized metallic nickel nanoparticles stabilized by a N-doped carbon layer on the active carbon support.
- Klarner, Mara,Bieger, Sandra,Drechsler, Markus,Kempe, Rhett
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supporting information
p. 2157 - 2161
(2021/05/21)
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- Ambient Hydrogenation and Deuteration of Alkenes Using a Nanostructured Ni-Core–Shell Catalyst
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A general protocol for the selective hydrogenation and deuteration of a variety of alkenes is presented. Key to success for these reactions is the use of a specific nickel-graphitic shell-based core–shell-structured catalyst, which is conveniently prepared by impregnation and subsequent calcination of nickel nitrate on carbon at 450 °C under argon. Applying this nanostructured catalyst, both terminal and internal alkenes, which are of industrial and commercial importance, were selectively hydrogenated and deuterated at ambient conditions (room temperature, using 1 bar hydrogen or 1 bar deuterium), giving access to the corresponding alkanes and deuterium-labeled alkanes in good to excellent yields. The synthetic utility and practicability of this Ni-based hydrogenation protocol is demonstrated by gram-scale reactions as well as efficient catalyst recycling experiments.
- Beller, Matthias,Feng, Lu,Gao, Jie,Jackstell, Ralf,Jagadeesh, Rajenahally V.,Liu, Yuefeng,Ma, Rui
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supporting information
p. 18591 - 18598
(2021/06/28)
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- Nickel Complexes Bearing N,N,O-Tridentate Salicylaldiminato Ligand: Efficient Catalysts for Imines Formation via Dehydrogenative Coupling of Primary Alcohols with Amines
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Treatment of salicylaldiminato ligand L1H-L2H (L1H = 2,4-di-tert-butyl-6-((quinolin-8-ylimino)methyl)phenol; L2H = 2,4-di-tert-butyl-6-(((2-(diethylamino)ethyl)imino)methyl)phenol) with Ni(OAc)2·4H2O in refluxing ethanol afforded nickel complexes [(L1)Ni(OAc)] (1) and [(L2)Ni(OAc)] (2), respectively. Reaction of L3H (L3H = (2,4-di-tert-butyl-6-(((2-(pyridin-2-yl)ethyl)imino)methyl)phenol)) with Ni(OAc)2·4H2O in the presence of excess triethylanmine gave the dual ligands coordinated nickel complex [(L2)2Ni] (3). Complexes 1-3 were well characterized by high-resolution mass spectrometry, infrared spectroscopy, elemental analysis, and X-ray diffraction analysis. All the three Ni(II) complexes exhibited efficient activity and good selectivity in the acceptorless dehydrogenative coupling of alcohols and amines to produce imines and diimines. The present protocol provides an atom-economical and sustainable route for the synthesis of various imine derivatives by employing an earth-abundant nickel salt and easily prepared salicylaldiminato ligands.
- Han, Zhangang,Hao, Zhiqiang,Lin, Jin,Lu, Guo-Liang,Zhang, Junhua,Zhang, Xiaoying
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p. 3843 - 3853
(2021/11/18)
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- A regionally selective hydrogenation method for chromium-catalyzed thick cyclic aromatic hydrocarbons and olefins based on magnesium-activated ligands
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The present invention relates to the field of hydrogenation, specifically to a chromium-activated complex cyclic aromatic hydrocarbons and olefins promoted by magnesium-activated ligands regionally selective hydrogenation method, which is based on the in situ reduction strategy of magnesium, with biimides as ligands, CrCl2 as catalyst precursors, to construct an efficient low-costchromium hydrogenation system, under mild conditions, to achieve unilateral cyclic hydrogenation of thick ring aromatic hydrocarbons and high-selective hydrogenation of olefins. The system of the present invention is suitable for a variety of substrates of fused cyclic aromatic hydrocarbons, such as tetraphenyl, benzoanthracene, pentabenzo and alfalfa and the like. This provides a simple and efficient strategy and pathway for the synthesis of partially saturated thick cyclic aromatic hydrocarbon compounds.
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Paragraph 0020
(2022/01/10)
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- Chemoselective Deoxygenation of 2° Benzylic Alcohols through a Sequence of Formylation and B(C6F5)3-Catalyzed Reduction
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A sequence of formylation and B(C6F5)3-catalyzed reduction of the resulting formate with Et3SiH enables the chemoselective deoxygenation of secondary benzylic alcohols. Primary benzylic and tertiary non-benzylic alcohols are not reduced by this protocol. The formyl group fulfills a double role as activator and self-sacrificing protecting group. The deoxygenation of these formates is fast and can be carried out in the presence of other potentially reducible groups. Neighboring-group participation was found in the deoxygenation of certain diol motifs.
- Oestreich, Martin,Richter, Sven C.
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supporting information
p. 2103 - 2106
(2021/07/22)
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- Metal-Organic Framework-Confined Single-Site Base-Metal Catalyst for Chemoselective Hydrodeoxygenation of Carbonyls and Alcohols
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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
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supporting information
p. 9029 - 9039
(2021/06/28)
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- Arylketones as Aryl Donors in Palladium-Catalyzed Suzuki-Miyaura Couplings
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Herein, we report the arylation, alkylation, and alkenylation of aryl ketones via a palladium-catalyzed Suzuki-Miyaura cross-coupling reaction. The use of the pyridine-oxazoline ligand is the key to the cleavage of the unstrained C-C bond. The late-stage arylation of aryl ketones derived from drugs and natural products demonstrated the synthetic utility of this protocol.
- Wang, Zhen-Yu,Ma, Biao,Xu, Hui,Wang, Xing,Zhang, Xu,Dai, Hui-Xiong
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p. 8291 - 8295
(2021/11/13)
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- Iron-catalyzed cross-coupling reactions of alkyl grignards with aryl chlorobenzenesulfonates
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Aryl sulfonate esters are versatile synthetic intermediates in organic chemistry as well as attractive architectures due to their bioactive properties. Herein, we report the synthesis of alkyl-substituted benzenesulfonate esters by iron-catalyzed C(sp2)–C(sp3) cross-coupling of Grignard reagents with aryl chlorides. The method operates using an environmentally benign and sustainable iron catalytic system, employing benign urea ligands. A broad range of chlorobenzenesulfonates as well as challenging alkyl organometallics containing β-hydrogens are compatible with these conditions, affording alkylated products in high to excellent yields. The study reveals that aryl sulfonate esters are the most reactive activating groups for iron-catalyzed alkylative C(sp2)–C(sp3) cross-coupling of aryl chlorides with Grignard reagents.
- Bisz, Elwira
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- Chromium-Catalyzed Borylative Coupling of Aliphatic Bromides with Pinacolborane by Hydrogen Evolution
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The chromium-catalyzed borylative coupling between aliphatic bromides and pinacolborane (HBpin) is described. This reaction was promoted by low-cost and bench-stable CrCl3as a precatalyst combined with 4,4′-di-tert-butyl-2,2′-dipyridyl and aluminum, presenting a rare example of using HBpin as a borane reagent by coupling with alkyl bromides in forming borylated alkanes. Mechanistic studies indicate that aluminum plays important roles in the formation of reactive Cr species and aliphatic radicals, which lead to (alkyl)Cr by reaction with HBpin to give the products.
- Fu, Aiping,Li, Chao,Luo, Meiming,Zeng, Xiaoming,Zhao, Lixing
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supporting information
p. 2204 - 2208
(2021/06/28)
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- Nickel-Mediated Enantiospecific Silylation via Benzylic C-OMe Bond Cleavage
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Benzylic stereocenters are found in bioactive and drug molecules, as enantiopure benzylic alcohols have been used to build such a stereogenic center, but are limited to the construction of a C-C bond. Silylation of alkyl alcohols has the potential to build bioactive molecules and building blocks; however, the development of such a process is challenging and unknown. Herein, we describe an unprecedented AgF-assisted nickel catalysis in the enantiospecific silylation of benzylic ethers.
- Balakrishnan, Venkadesh,Murugesan, Vetrivelan,Chindan, Bincy,Rasappan, Ramesh
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p. 1333 - 1338
(2021/02/20)
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- HIGHLY SELECTIVE ELECTROCHEMICAL HYDROGENATION OF ALKYNES
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Disclosed are electrochemical methods to prepare an alkane or an alkene, such as a cis- alkene, from an alkyne, or an alkane from an alkene. The method utilizes an electrochemical cell having a cathode and an anode and a reactor.
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Page/Page column 7
(2020/10/20)
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- Transition metal complexes of a bis(carbene) ligand featuring 1,2,4-triazolin-5-ylidene donors: structural diversity and catalytic applications
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Dialkylation of the 1,3-bis(1,2,4-triazol-1-yl)benzene with ethyl bromide results in the formation of [L-H2]Br2which, upon salt metathesis with NH4PF6, readily yields the bis(triazolium) salt [L-H2](PF6)2with non-coordinating counterions. [L-H2](PF6)2and Ag2O react in a 1?:?1 ratio to yield a binuclear AgI-tetracarbene complex of the composition [(L)2Ag2](PF6)2which undergoes a facile transmetalation reaction with [Cu(SMe2)Br] to deliver the corresponding CuI-NHC complex [(L)2Cu2](PF6)2. In contrast, the [L-H2]Br2reacts with [Ir(Cp*)Cl2]2to generate a doubly C-H activated IrIII-NHC complex5. Similarly, the triazolinylidene donor supported diorthometalated RuII-complex6is also obtained. Complexes5and6represent the first examples of a stable diorthometalated binuclear IrIII/RuII-complex supported by 1,2,4-triazolin-5-ylidene donors. The synthesized IrIII-NHC complex5is found to be more effective than its RuII-analogue (6) for the reduction of a range of alkenes/alkynesviathe transfer hydrogenation strategy. Conversely, RuII-complex6is identified as an efficient catalyst (0.01 mol% loading) for the β-alkylation of a wide range of secondary alcohols using primary alcohols as alkylating partnersviaa borrowing hydrogen strategy.
- Donthireddy, S. N. R.,Illam, Praseetha Mathoor,Rit, Arnab,Singh, Vivek Kumar
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p. 11958 - 11970
(2020/09/21)
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- Hollow Carbon Sphere Nanoreactors Loaded with PdCu Nanoparticles: Void-Confinement Effects in Liquid-Phase Hydrogenations
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Nanoreactors with hollow structures have attracted great interest in catalysis research due to their void-confinement effects. However, the challenge in unambiguously unraveling these confinement effects is to decouple them from other factors affecting catalysis. Here, we synthesize a pair of hollow carbon sphere (HCS) nanoreactors with presynthesized PdCu nanoparticles encapsulated inside of HCS (PdCu?HCS) and supported outside of HCS (PdCu/HCS), respectively, while keeping other structural features the same. Based on the two comparative nanoreactors, void-confinement effects in liquid-phase hydrogenation are investigated in a two-chamber reactor. It is found that hydrogenations over PdCu?HCS are shape-selective catalysis, can be accelerated (accumulation of reactants), decelerated (mass transfer limitation), and even inhibited (molecular-sieving effect); conversion of the intermediate in the void space can be further promoted. Using this principle, a specific imine is selectively produced. This work provides a proof of concept for fundamental catalytic action of the hollow nanoreactors.
- Dong, Chao,Liu, Jian,Su, Panpan,Wang, Guang-Hui,Ye, Run-Ping,Yu, Qun
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supporting information
p. 18374 - 18379
(2020/08/19)
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- Reductive Deamination with Hydrosilanes Catalyzed by B(C6F5)3
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The strong boron Lewis acid tris(pentafluorophenyl)borane B(C6F5)3 is known to catalyze the dehydrogenative coupling of certain amines and hydrosilanes at elevated temperatures. At higher temperature, the dehydrogenation pathway competes with cleavage of the C?N bond and defunctionalization is obtained. This can be turned into a useful methodology for the transition-metal-free reductive deamination of a broad range of amines as well as heterocumulenes such as an isocyanate and an isothiocyanate.
- Fang, Huaquan,Oestreich, Martin
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supporting information
p. 11394 - 11398
(2020/05/25)
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- Copper-catalyzed formal transfer hydrogenation/deuteration of aryl alkynes
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A copper-catalyzed reduction of alkynes to alkanes and deuterated alkanes is described under transfer hydrogenation and transfer deuteration conditions. Commercially available alcohols and silanes are used interchangeably with their deuterated analogues as the hydrogen or deuterium sources. Transfer deuteration of terminal and internal aryl alkynes occurs with high levels of deuterium incorporation. Alkyne-containing complex natural product analogues undergo transfer hydrogenation and transfer deuteration selectively, in high yield. Mechanistic experiments support the reaction occurring through a cis-alkene intermediate and demonstrate the possibility for a regioselective alkyne transfer hydrodeuteration reaction.
- Sloane, Samantha E.,Reyes, Albert,Vang, Zoua Pa,Li, Lingzi,Behlow, Kiera T.,Clark, Joseph R.
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supporting information
p. 9139 - 9144
(2020/11/30)
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- Catalytic Transfer Hydrogenation Using Biomass as Hydrogen Source
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We developed an operationally simple method for the direct use of biomass-derived chemical entities in a fundamentally important process, such as hydrogenation. Various carbohydrates, starch, and lignin were used for stereoselective hydrogenation. Employing a transition metal catalyst and a novel catalytic system, the reduction of alkynes, alkenes, and carbonyl groups with high yields was demonstrated. The regioselective hydrogenation to access different stereoisomers was established by simple variations in the reaction conditions. This work is based on an unprecedented catalytic system and represents a straightforward application of biomass as a reducing reagent in chemical reactions.
- Antonchick, Andrey P.,Manna, Srimanta
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p. 3094 - 3098
(2018/09/14)
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- Combined Photoredox/Enzymatic C?H Benzylic Hydroxylations
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Chemical transformations that install heteroatoms into C?H bonds are of significant interest because they streamline the construction of value-added small molecules. Direct C?H oxyfunctionalization, or the one step conversion of a C?H bond to a C?O bond, could be a highly enabling transformation due to the prevalence of the resulting enantioenriched alcohols in pharmaceuticals and natural products,. Here we report a single-flask photoredox/enzymatic process for direct C?H hydroxylation that proceeds with broad reactivity, chemoselectivity and enantioselectivity. This unified strategy advances general photoredox and enzymatic catalysis synergy and enables chemoenzymatic processes for powerful and selective oxidative transformations.
- Betori, Rick C.,May, Catherine M.,Scheidt, Karl A.
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supporting information
p. 16490 - 16494
(2019/11/03)
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- Nickel-catalyzed anti-Markovnikov hydroarylation of alkenes
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We have developed a nickel-catalyzed hydroarylation of alkenes using aryl halides as coupling partners. Excellent anti-Markovnikov selectivity is achieved with aryl-substituted alkenes and enol ethers. We also show that hydroarylation occurs with alkyl substituted alkenes to yield linear products. Preliminary examination of the reaction mechanism suggests irreversible hydrometallation as the selectivity determining step of the hydroarylation.
- Nguyen, Julia,Chong, Andrea,Lalic, Gojko
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p. 3231 - 3236
(2019/03/21)
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- A catalytically active [Mn]-hydrogenase incorporating a non-native metal cofactor
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Nature carefully selects specific metal ions for incorporation into the enzymes that catalyse the chemical reactions necessary for life. Hydrogenases, enzymes that activate molecular H2, exclusively utilize Ni and Fe in [NiFe]-, [FeFe]- and [Fe]-hydrogeanses. However, other transition metals are known to activate or catalyse the production of hydrogen in synthetic systems. Here, we report the development of a biomimetic model complex of [Fe]-hydrogenase that incorporates a Mn, as opposed to a Fe, metal centre. This Mn complex is able to heterolytically cleave H2 as well as catalyse hydrogenation reactions. The incorporation of the model into an apoenzyme of [Fe]-hydrogenase results in a [Mn]-hydrogenase with an enhanced occupancy-normalized activity over an analogous semi-synthetic [Fe]-hydrogenase. These findings demonstrate a non-native metal hydrogenase that shows catalytic functionality and that hydrogenases based on a manganese active site are viable.
- Pan, Hui-Jie,Huang, Gangfeng,Wodrich, Matthew D.,Tirani, Farzaneh Fadaei,Ataka, Kenichi,Shima, Seigo,Hu, Xile
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p. 669 - 675
(2019/05/29)
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- Phosphine Ligand-Free Ruthenium Complexes as Efficient Catalysts for the Synthesis of Quinolines and Pyridines by Acceptorless Dehydrogenative Coupling Reactions
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A series of phosphine-free Ru(III)/Ru(II) complexes of NH functionalized N?N?N pincer ligands exhibit excellent activity for acceptorless dehydrogenative coupling (ADC) of secondary alcohols with 2-aminobenzyl or γ-amino alcohols to quinolines and pyridines. Ru(III) complexes [LRuCl3] (L=6-(3-R1,5-R2-1H-pyrazol-1-yl)-N-(pyridin-2-yl)pyridin-2-amine; 1 a: R1=R2=H (L1); 1 b: R1=R2=Me (L2); 1 c: R1=H, R2=CF3 (L3); 1 d: R1=H, R2=Ph (L4); 1bMe: L=6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-methyl-N-(pyridin-2-yl)pyridin-2-amine (L2Me)) were obtained by refluxing RuCl3 ? xH2O with the corresponding ligand in EtOH. Five Ru(II) complexes [LRu(DMSO-κS)Cl2] (2 a: L=L1; 2 b: L=L2; 2 c: L=L3; 2 d: L=L4; 2bMe: L=L2Me) were formed by reducing the corresponding Ru(III) complex in refluxing EtOH. The latter complexes could also be prepared directly by refluxing Ru(DMSO)4Cl2 with the corresponding ligand in EtOH. These Ru(III) and Ru(II) complexes, especially 1 b/2 b, exhibited high catalytic efficiency and broad functional group tolerance in ADC reactions of secondary alcohols with 2-aminobenzyl or γ-amino alcohols to quinolines and pyridines. A detail mechanistic study indicated the Ru(III) complex was reduced into the Ru(II) species, which is the active catalytic center for ADC via a Ru?H/N?H bifunctional outer-sphere mechanism. This protocol provides a reliable, atom-economical and environmentally benign procedure for C?N and C?C bond formation.
- Guo, Bin,Yu, Tian-Qi,Li, Hong-Xi,Zhang, Shi-Qi,Braunstein, Pierre,Young, David J.,Li, Hai-Yan,Lang, Jian-Ping
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p. 2500 - 2510
(2019/05/10)
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- Mild and efficient rhodium-catalyzed deoxygenation of ketones to alkanes
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A new and simple method for the deoxygenation of ketones to alkanes is presented. Most substrates are reduced under mild conditions by triethylsilane in the presence of catalytic amounts of [Rh(μ-Cl)(CO)2]2. This system selectively provides the methylene hydrocarbons in good to excellent yields starting from acetophenones and diaryl ketones. A rapid examination of the reaction pathway suggests that the ketone is first converted into an alcohol, which then undergoes hydrogenolysis to give the alkane.
- Argouarch, Gilles
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supporting information
p. 11041 - 11044
(2019/07/31)
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- Reductive C-O, C-N, and C-S Cleavage by a Zirconium Catalyzed Hydrometalation/β-Elimination Approach
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A zirconium catalyzed reductive cleavage of Csp3 and Csp2 carbon-heteroatom bonds is reported that makes use of a tethered alkene functionality as a traceless directing group. The reaction is successfully demonstrated on C-O, C-N, and C-S bonds and proposed to proceed via a hydrozirconation/β-heteroatom elimination sequence of an in situ formed zirconium hydride catalyst. The positional isomerization of the catalyst further enables the cleavage of homoallylic ethers and the removal of terminal allyl and propargyl groups.
- Matt, Christof,K?lblin, Frederic,Streuff, Jan
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supporting information
p. 6983 - 6988
(2019/09/09)
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- Catalytic protodeboronation of pinacol boronic esters: Formal anti-Markovnikov hydromethylation of alkenes
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Pinacol boronic esters are highly valuable building blocks in organic synthesis. In contrast to the many protocols available on the functionalizing deboronation of alkyl boronic esters, protodeboronation is not well developed. Herein we report catalytic protodeboronation of 1°, 2° and 3° alkyl boronic esters utilizing a radical approach. Paired with a Matteson-CH2-homologation, our protocol allows for formal anti-Markovnikov alkene hydromethylation, a valuable but unknown transformation. The hydromethylation sequence was applied to methoxy protected (-)-Δ8-THC and cholesterol. The protodeboronation was further used in the formal total synthesis of δ-(R)-coniceine and indolizidine 209B.
- Clausen, Florian,Kischkewitz, Marvin,Bergander, Klaus,Studer, Armido
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p. 6210 - 6214
(2019/06/27)
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- Pd anchored on C3N4 nanosheets/reduced graphene oxide: An efficient catalyst for the transfer hydrogenation of alkenes
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In this work, a porous g-C3N4 nanosheets/reduced graphene oxide (rGO) composite was synthesized via the hydrothermal co-assembly of GO and g-C3N4 nanosheets (g-C3N4 NS). Compared with g-C3N4 NS, rGO and bulk g-C3N4/rGO, the g-C3N4 NS/rGO supported Pd nanocatalyst displayed a remarkable catalytic activity for the hydrogenation of alkenes with formic acid and formates as the hydrogen source at atmospheric pressure. Among all the as-prepared Pd-g-C3N4 NS/rGO catalysts, the optimized Pd-g-C3N4 NS/rGO20 exhibited the highest turnover frequency of 133 mol mol-1 Pd h-1, which is among the highest value reported in documents. 99% conversion and 99% selectivity were achieved after 30 min reaction at 30 °C for the hydrogenation of nitrobenzene. In addition, Pd-g-C3N4 NS/rGO20 exhibited an excellently high stability after five successive cycles without significant loss of its catalytic activity.
- Li, Jie,Cheng, Saisai,Du, Tianxing,Shang, Ningzhao,Gao, Shutao,Feng, Cheng,Wang, Chun,Wang, Zhi
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p. 9324 - 9331
(2018/06/08)
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- Pd Nanoparticles Confined in the Porous Graphene-like Carbon Nanosheets for Olefin Hydrogenation
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As a novel type of defective graphene, porous graphene has been considered an excellent support material for metal clusters, as the interaction between defective carbon atoms surrounded with the metal nanoparticles (NPs) is very different from that on the ordinary supported catalyst. In this work, we reported a facile three-step method to confine the Pd NPs and grow the graphene-like carbon nanosheets (GLCs) in the same interlayer space of the layered silicate, generating embedded Pd NPs in the pores of porous GLCs in situ. The Pd@GLC nanocomposite exhibited not only high activity and stability than the common commercial Pd/C catalyst for the hydrogenation of olefins but also superior ability of resisting high temperature, which benefitted from the two-dimensional structure of layered GLCs, the confinement of Pd, and the increased edge and defect of the unsaturated carbon atoms in GLCs.
- Chen, Zhe,Wang, Weixue,Zhang, Yifei,Liang, Yu,Cui, Zhimin,Wang, Xiangke
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p. 12809 - 12814
(2018/10/24)
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- Homogeneous Palladium-Catalyzed Transfer Hydrogenolysis of Benzylic Alcohols Using Formic Acid as Reductant
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We report the first homogeneous palladium-based transfer hydrogenolysis of benzylic alcohols using an in situ formed palladium-phosphine complex and formic acid as reducing agent. The reaction requires a catalyst loading as low as only 1 mol % of palladium and just a slight excess of reductant to obtain the deoxygenated alkylarenes in good to excellent yields. Besides demonstrating the broad applicability for primary, secondary and tertiary benzylic alcohols, a reaction intermediate could be identified. Additionally, it could be shown that partial oxidation of the applied phosphine ligand was beneficial for the course of the reaction, presumably by stabilizing the active catalyst. Reaction profiles and catalyst poisoning experiments were used to characterize the catalyst, the results of which indicate a homogeneous metal complex as the active species.
- Ciszek, Benjamin,Fleischer, Ivana
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p. 12259 - 12263
(2018/08/28)
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- Chlorotrimethylsilane and Sodium Iodide: A Remarkable Metal-Free Association for the Desulfurization of Benzylic Dithioketals under Mild Conditions
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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
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p. 2522 - 2536
(2018/05/14)
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- Bimetallic Nanoparticles in Supported Ionic Liquid Phases as Multifunctional Catalysts for the Selective Hydrodeoxygenation of Aromatic Substrates
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Bimetallic iron–ruthenium nanoparticles embedded in an acidic supported ionic liquid phase (FeRu@SILP+IL-SO3H) act as multifunctional catalysts for the selective hydrodeoxygenation of carbonyl groups in aromatic substrates. The catalyst material is assembled systematically from molecular components to combine the acid and metal sites that allow hydrogenolysis of the C=O bonds without hydrogenation of the aromatic ring. The resulting materials possess high activity and stability for the catalytic hydrodeoxygenation of C=O groups to CH2 units in a variety of substituted aromatic ketones and, hence, provide an effective and benign alternative to traditional Clemmensen and Wolff–Kishner reductions, which require stoichiometric reagents. The molecular design of the FeRu@SILP+IL-SO3H materials opens a general approach to multifunctional catalytic systems (MM′@SILP+IL-func).
- Offner-Marko, Lisa,Bordet, Alexis,Moos, Gilles,Tricard, Simon,Rengshausen, Simon,Chaudret, Bruno,Luska, Kylie L.,Leitner, Walter
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supporting information
p. 12721 - 12726
(2018/09/12)
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- Hydrodebromination of allylic and benzylic bromides with water catalyzed by a rhodium porphyrin complex
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Hydrodebromination of allylic and benzylic bromides was successfully achieved by a rhodium porphyrin complex catalyst using water as the hydrogen source without a sacrificial reductant. Mechanistic investigations suggest that bromine atom abstraction via a rhodium porphyrin metalloradical operates to give the rhodium porphyrin alkyl species and the subsequent hydrolysis of the rhodium porphyrin alkyl species to a hydrocarbon product is a key step to harness the hydrogen from water.
- Yang, Wu,Chen, Chen,Chan, Kin Shing
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p. 12879 - 12883
(2018/10/02)
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- Pd-Catalyzed Alkylation of (Iso)quinolines and Arenes: 2-Acylpyridine Compounds as Alkylation Reagents
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The first Pd-catalyzed alkylation of (iso)quinolines and arenes is reported. The readily available and bench-stable 2-acylpyridine compounds were used as an alkylation reagent to form the structurally versatile alkylated (iso)quinolines and arenes. The method affords a convenient pathway for the introduction of alkyl groups into organic molecules.
- Wu, Qingsong,Han, Shuaijun,Ren, Xiaoxiao,Lu, Hongtao,Li, Jingya,Zou, Dapeng,Wu, Yangjie,Wu, Yusheng
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supporting information
p. 6345 - 6348
(2018/10/20)
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- Ni-Catalyzed cross-coupling of aryl thioethers with alkyl Grignard reagents via C-S bond cleavage
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A Ni-catalyzed cross-coupling of aryl thioethers with alkyl Grignard reagents, accompanied by the cleavage of the C(aryl)-SMe bond, has been presented. This method is distinguished by its mild conditions and moderate functional group tolerance, such as hydroxyl, halogen, and heterocycles, which should provide a straightforward access to the modification of sulfur-containing molecules.
- Zhu, Dan,Shi, Lei
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supporting information
p. 9313 - 9316
(2018/08/29)
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- Nickel-Catalyzed Reductive Cleavage of Carbon-Oxygen Bonds in Anisole Derivatives Using Diisopropylaminoborane
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The catalytic removal of a methoxy group on an aromatic ring allows this group to be used as a traceless activating and directing group for aromatic functionalization reactions. Although several catalytic methods for the reductive cleavage of anisole derivatives have been reported, all are applicable only to π-extended aryl ethers, such as naphthyl and biphenyl ethers, while monocyclic aryl ethers cannot be reduced. Herein, we report a nickel-catalyzed reductive cleavage reaction of C-O bonds in aryl ethers using diisopropylaminoborane as the reducing agent. Unlike previously reported methods, this reducing reagent allows effective C-O bond reduction in a much wider range of aryl ether substrates, including monocyclic and heterocyclic ethers bearing various functional groups.
- Igarashi, Takuya,Haito, Akira,Chatani, Naoto,Tobisu, Mamoru
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p. 7475 - 7483
(2018/07/21)
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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 Chemoselective C(acyl)-O Bond vs C(aryl)-C Bond Activation of Aromatic Esters in Nickel Catalyzed C(sp2)-C(sp3) Cross-Couplings
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A ligand-controlled and site-selective nickel catalyzed Suzuki-Miyaura cross-coupling reaction with aromatic esters and alkyl organoboron reagents as coupling partners was developed. This methodology provides a facile route for C(sp2)-C(sp3) bond formation in a straightforward fashion by successful suppression of the undesired β-hydride elimination process. By simply switching the phosphorus ligand, the ester substrates are converted into the alkylated arenes and ketone products, respectively. The utility of this newly developed protocol was demonstrated by its wide substrate scope, broad functional group tolerance and application in the synthesis of key intermediates for the synthesis of bioactive compounds. DFT studies on the oxidative addition step helped rationalizing this intriguing reaction chemoselectivity: whereas nickel complexes with bidentate ligands favor the C(aryl)-C bond cleavage in the oxidative addition step leading to the alkylated product via a decarbonylative process, nickel complexes with monodentate phosphorus ligands favor activation of the C(acyl)-O bond, which later generates the ketone product.
- Chatupheeraphat, Adisak,Liao, Hsuan-Hung,Srimontree, Watchara,Guo, Lin,Minenkov, Yury,Poater, Albert,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 3724 - 3735
(2018/03/21)
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- Methylation of Arenols through Ni-catalyzed C—O Activation with Methyl Magnesium Bromide
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Direct alkylation of arenols with alkyl organometallic reagents has never been approached. Herein we reported the first successful example of nickel-catalyzed methylation of arenols with methyl Grignard reagents to construct C(sp2)-C(sp3/
- Shi, Wen-Juan,Shi, Zhang-Jie
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supporting information
p. 183 - 186
(2018/01/15)
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- Efficient Water Reduction with sp3-sp3 Diboron(4) Compounds: Application to Hydrogenations, H–D Exchange Reactions, and Carbonyl Reductions
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A series of crystalline sp3-sp3 diboron(4) compounds were synthesized and shown to promote the facile reduction of water with dihydrogen formation. The application of these diborons as simple and effective dihydrogen and dideuterium sources was demonstrated by conducting a series of selective reductions of alkynes and alkenes, and hydrogen–deuterium exchange reactions using two-chamber reactors. Finally, as the water reduction reaction generates an intermediate borohydride species, a range of aldehydes and ketones were reduced by using water as the hydride source.
- Flinker, Mathias,Yin, Hongfei,Juhl, René W.,Eikeland, Espen Z.,Overgaard, Jacob,Nielsen, Dennis U.,Skrydstrup, Troels
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supporting information
p. 15910 - 15915
(2017/11/23)
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- Iridium-catalysed hydrosilylation of cyclopropanes: Via regioselective carbon-carbon bond cleavage
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While cyclopropanes have been explored as synthetically valuable building blocks, their transformation without conjugated substituents or directly substituted heteroatoms remains challenging. The current study describes the iridium-catalysed ring-opening hydrosilylation of cyclopropanes. A nitrogen-based directing group was found to control the reactivity of iridium active species as well as the regiochemistry of carbon-carbon bond cleavage and hydrosilylation.
- Murai, Masahito,Nishiyama, Atsushi,Nishinaka, Naoki,Morita, Haruka,Takai, Kazuhiko
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supporting information
p. 9281 - 9284
(2017/08/21)
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- Nickel-Catalyzed C-O Bond-Cleaving Alkylation of Esters: Direct Replacement of the Ester Moiety by Functionalized Alkyl Chains
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Two efficient protocols for the nickel-catalyzed aryl-alkyl cross-coupling reactions using esters as coupling components have been established. The methods enable the selective oxidative addition of nickel to acyl C-O and aryl C-O bonds and allow the aryl-alkyl cross-coupling via decarbonylative bond cleavage or through cleavage of a C-O bond with high efficiency and good functional group compatibility. The protocols allow the streamlined, unconventional utilization of widespread ester groups and their precursors, carboxylic acids and phenols, in synthetic organic chemistry.
- Liu, Xiangqian,Jia, Jiaqi,Rueping, Magnus
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p. 4491 - 4496
(2017/07/24)
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- Nickel-catalyzed cross-coupling of aryl or 2-menaphthyl quaternary ammonium triflates with organoaluminum reagents
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The cross-coupling of aryltrimethylammonium triflates with AlMe3 and β-H-containing trialkylaluminums was performed in dioxane at 110 °C under catalysis of (dppp)NiCl2 to afford alkylated arenes. The cross-coupling of 2-menaphthyltri
- He, Fang,Wang, Zhong-Xia
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p. 4450 - 4457
(2017/06/30)
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- Preparation of Magnetic Tubular Nanoreactors for Highly Efficient Catalysis
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We report an efficient and controllable route to prepare magnetic tubular nanoreactors composed of a mesoporous SiO2 shell with iron-noble metal nanoparticles inside. The key of this method is to design and fabricate Fe nanoparticles encapsulated in a mesoporous SiO2 shell. Making use of a galvanic replacement reaction between Fe and noble metal ions, all of the noble metal nanoparticles are loaded inside the mesoporous SiO2 shell, and thus nanoreactors are formed. Taking Pd as an example, the prepared Pd?Fe@meso-SiO2 tubular nanoreactor exhibits a high catalytic activity and excellent reusability for styrene hydrogenation under mild conditions. This study provides a facile route to fabricate magnetic nanoreactors with enhanced catalytic properties.
- Yang, Shuliang,Peng, Li,Cao, Changyan,Wei, Fang,Liu, Jian,Zhu, Ya-Nan,Liu, Chang,Wang, Xiaoshi,Song, Weiguo
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p. 2797 - 2801
(2016/10/11)
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- Palladium nanoparticles stabilised by cinchona-based alkaloids in glycerol: Efficient catalysts for surface assisted processes
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Palladium nanoparticles (PdNPs) were synthesised and fully characterised, both in solution and the solid state, using naturally-occurring cinchona-based alkaloids in neat glycerol. These nano-systems were stable under reaction conditions, finding applications in hydrogenation and hydrodehalogenation processes, as a result of their surface-like behaviour. Their reactivity was improved in relation to that involving PdNPs stabilised by phosphines and also by Pd/C as a heterogenous catalyst, mainly in terms of recyclability. In particular, the colloidal palladium catalyst stabilised by quinidine was highly efficient to promote the hydrodechlorination of aromatic compounds under low dihydrogen pressure. These original catalysts found applications in the synthesis of secondary and tertiary amines including N-substituted anilines, by means of one-pot tandem Pd-catalysed methodologies under smooth conditions. In all of these processes, glycerol performed a crucial function as a liquid support for the immobilisation of nanoparticle-based catalysts, allowing both the stabilisation of the nano-catalysts and easy recycling of the catalytic phase.
- Reina,Pradel,Martin,Teuma,Gómez
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p. 93205 - 93216
(2016/10/11)
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- Nickel-Catalyzed Alkoxy–Alkyl Interconversion with Alkylborane Reagents through C?O Bond Activation of Aryl and Enol Ethers
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A nickel-catalyzed alkylation of polycyclic aromatic methyl ethers as well as methyl enol ethers with B-alkyl 9-BBN and trialkylborane reagents that involves the cleavage of stable C(sp2)?OMe bonds is described. The transformation has a wide substrate scope and good chemoselectivity profile while proceeding under mild reaction conditions; it provides a versatile way to form C(sp2)?C(sp3) bonds that does not suffer from β-hydride elimination. Furthermore, a selective and sequential alkylation process by cleavage of inert C?O bonds is presented to demonstrate the advantage of this method.
- Guo, Lin,Liu, Xiangqian,Baumann, Christoph,Rueping, Magnus
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p. 15415 - 15419
(2016/12/03)
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- Highly selective hydrogenation and hydrogenolysis using a copper-doped porous metal oxide catalyst
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A copper-doped porous metal oxide catalyst in combination with hydrogen shows selective and quantitative hydrogenolysis of benzyl ketones and aldehydes, and hydrogenation of alkenes. The approach provides an alternative to noble-metal catalysed reductions and stoichiometric Wolff-Kishner and Clemmensen methods.
- Petitjean, Laurene,Gagne, Raphael,Beach, Evan S.,Xiao, Dequan,Anastas, Paul T.
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p. 150 - 156
(2015/12/31)
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- Intramolecular carbonyl-ene reactions in the synthesis of peri-oxygenated hydroaromatics
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2-Methallyl aromatic aldehydes, synthesized by Suzuki coupling of 2-formylphenylboronic acids, are shown to provide cycloalkylidene ene products under acidic conditions. Susceptibility of the products to aromatization is manoeuvred by varying the reaction conditions and catalysts including binol-derived Br?nsted acid catalysts. A peri-effect is identified as a controlling factor for the aromatizations. Several oxidative transformations of an ene product are carried out as model studies of hydroaromatic polyketide natural products.
- Basak, Shyam,Mal, Dipakranjan
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p. 1758 - 1772
(2018/03/29)
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- Domino Methylenation/Hydrogenation of Aldehydes and Ketones by Combining Matsubara's Reagent and Wilkinson's Catalyst
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The methylenation/hydrogenation cascade reaction of aldehydes or ketones through a domino process involving two ensuing steps in a single pot is realized. The compatibility of Matsubara's reagent and Wilkinson's complex give a combination that allows, under dihydrogen, the transformation of a carbonyl function into a methyl group. This new method is suitable to introduce an ethyl motif from aromatic and aliphatic aldehydes with total chemoselectivity and total retention of α-stereochemical purity. The developed procedure is also extended to the introduction of methyl groups from ketones.
- Maazaoui, Radhouan,Pin-Nó, María,Gervais, Kevin,Abderrahim, Raoudha,Ferreira, Franck,Perez-Luna, Alejandro,Chemla, Fabrice,Jackowski, Olivier
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supporting information
p. 5732 - 5737
(2016/12/14)
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- Nickel-Catalyzed Borylation of Aryl and Benzyl 2-Pyridyl Ethers: A Method for Converting a Robust ortho-Directing Group
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The nickel-catalyzed borylation of aryl 2-pyridyl ethers via the loss of a 2-pyridyloxy group is described. This method allows a 2-pyridyloxy group to be used as a convertible directing group in C?H bond functionalization reactions. The nickel catalyst can also borylate arylmethyl 2-pyridyl ethers, in which the stereochemistry at the benzylic position is retained in the case of chiral secondary benzylic substrates. (Figure presented.).
- Tobisu, Mamoru,Zhao, Jiangning,Kinuta, Hirotaka,Furukawa, Takayuki,Igarashi, Takuya,Chatani, Naoto
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supporting information
p. 2417 - 2421
(2016/08/16)
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