- Efficient splitting of alcohols into hydrogen and C–C coupled products over ultrathin Ni-doped ZnIn2S4 nanosheet photocatalyst
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Integrating selective organic synthesis with hydrogen (H2) evolution in one photocatalytic redox reaction system sheds light on the underlying approach for concurrent employment of photogenerated electrons and holes towards efficient production of solar fuels and chemicals. In this work, a facile one-pot oil bath method has been proposed to fabricate a noble metal-free ultrathin Ni-doped ZnIn2S4 (ZIS/Ni) composite nanosheet for effective solar-driven selective dehydrocoupling of benzyl alcohol into value-added C–C coupled hydrobenzoin and H2 fuel, which exhibits higher performance than pure ZIS nanosheet. The remarkably improved photoredox activity of ZIS/Ni is mainly attributed to the optimized electron structure featuring narrower band gap and suitable energy band position, which facilitates the ability of light harvesting and photoexcited charge carrier separation and transfer. Furthermore, it has been demonstrated that it is feasible to employ ZIS/Ni for various aromatic alcohols dehydrocoupling to the corresponding C–C coupled products. It is expected that this work can stimulate further interest on the establishment of innovative photocatalytic redox platform coupling clean solar fuels synthesis and selective organic conversion in a sustainable manner.
- Li, Jing-Yu,Qi, Ming-Yu,Xu, Yi-Jun
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p. 1084 - 1091
(2022/03/15)
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- Ni2P Nanoalloy as an Air-Stable and Versatile Hydrogenation Catalyst in Water: P-Alloying Strategy for Designing Smart Catalysts
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Non-noble metal-based hydrogenation catalysts have limited practical applications because they exhibit low activity, require harsh reaction conditions, and are unstable in air. To overcome these limitations, herein we propose the alloying of non-noble metal nanoparticles with phosphorus as a promising strategy for developing smart catalysts that exhibit both excellent activity and air stability. We synthesized a novel nickel phosphide nanoalloy (nano-Ni2P) with coordinatively unsaturated Ni active sites. Unlike conventional air-unstable non-noble metal catalysts, nano-Ni2P retained its metallic nature in air, and exhibited a high activity for the hydrogenation of various substrates with polar functional groups, such as aldehydes, ketones, nitriles, and nitroarenes to the desired products in excellent yields in water. Furthermore, the used nano-Ni2P catalyst was easy to handle in air and could be reused without pretreatment, providing a simple and clean catalyst system for general hydrogenation reactions.
- Fujita, Shu,Yamaguchi, Sho,Yamasaki, Jun,Nakajima, Kiyotaka,Yamazoe, Seiji,Mizugaki, Tomoo,Mitsudome, Takato
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supporting information
p. 4439 - 4446
(2021/02/09)
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- Metal-free thermal organocatalytic pinacol coupling of arylaldehydes using an isonicotinate catalyst with bis(pinacolato)diboron
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The metal-free thermal organocatalytic pinacol coupling of arylaldehydes has been developed. The intermolecular coupling of arylaldehydes catalyzed byt-butyl isonicotinate with bis(pinacolato)diboron as the co-reducing agent afforded 1,2-diphenylethane-1,2-diols. This reaction was also applicable to the intramolecular coupling of 1,1′-biphenyl-2,2′-dicarbaldehydes to afford 9,10-dihydrophenanthrene-9,10-diols. Various functional groups were tolerated under this coupling condition.
- Hanaya, Kengo,Higashibayashi, Shuhei,Sugai, Takeshi,Yasui, Masamichi
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p. 24652 - 24655
(2021/07/29)
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- A convenient pinacol coupling of diaryl ketones with B2pin2viapyridine catalysis
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A convenient, pyridine-boryl radical-mediated pinacol coupling of diaryl ketones is developed. In contrast to the conventional pinacol coupling that requires sensitive reducing metal, the current method employs a stable diboron reagent and pyridine Lewis base catalyst for the generation of a ketyl radical. The newly developed process is operationally simple, and the desired diols are produced with excellent efficiency in up to 99% yield within 1 hour. The superior reactivity of diaryl ketone was observed over monoaryl carbonyl compounds and analyzed by DFT calculations, which suggests the necessity of both aromatic rings for the maximum stabilization of the transition states.
- Jo, Junhyuk,Kim, Seonyul,Choi, Jun-Ho,Chung, Won-Jin
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supporting information
p. 1360 - 1363
(2021/02/22)
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- Electrochemical Arylation of Aldehydes, Ketones, and Alcohols: from Cathodic Reduction to Convergent Paired Electrolysis
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Arylation of carbonyls, one of the most common approaches toward alcohols, has received tremendous attention, as alcohols are important feedstocks and building blocks in organic synthesis. Despite great progress, there is still a great gap to develop an ideal arylation method featuring mild conditions, good functional group tolerance, and readily available starting materials. We now show that electrochemical arylation can fill the gap. By taking advantage of synthetic electrochemistry, commercially available aldehydes (ketones) and benzylic alcohols can be readily arylated to provide a general and scalable access to structurally diverse alcohols (97 examples, >10 gram-scale). More importantly, convergent paired electrolysis, the ideal but challenging electrochemical technology, was employed to transform low-value alcohols into more useful alcohols. Detailed mechanism study suggests that two plausible pathways are involved in the redox neutral α-arylation of benzylic alcohols.
- Zhang, Sheng,Li, Lijun,Li, Jingjing,Shi, Jianxue,Xu, Kun,Gao, Wenchao,Zong, Luyi,Li, Guigen,Findlater, Michael
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supporting information
p. 7275 - 7282
(2021/03/01)
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- Mo–Catalyzed One-Pot Synthesis of N-Polyheterocycles from Nitroarenes and Glycols with Recycling of the Waste Reduction Byproduct. Substituent-Tuned Photophysical Properties
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A catalytic domino reduction–imine formation–intramolecular cyclization–oxidation for the general synthesis of a wide variety of biologically relevant N-polyheterocycles, such as quinoxaline- and quinoline-fused derivatives, and phenanthridines, is reported. A simple, easily available, and environmentally friendly dioxomolybdenum(VI) complex has proven to be a highly efficient and versatile catalyst for transforming a broad range of starting nitroarenes involving several redox processes. Not only is this a sustainable, step-economical as well as air- and moisture-tolerant method, but also it is worth highlighting that the waste byproduct generated in the first step of the sequence is recycled and incorporated in the final target molecule, improving the overall synthetic efficiency. Moreover, selected indoloquinoxalines have been photophysically characterized in cyclohexane and toluene with exceptional fluorescence quantum yields above 0.7 for the alkyl derivatives.
- Hernández-Ruiz, Raquel,Rubio-Presa, Rubén,Suárez-Pantiga, Samuel,Pedrosa, María R.,Fernández-Rodríguez, Manuel A.,Tapia, M. José,Sanz, Roberto
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supporting information
p. 13613 - 13623
(2021/08/23)
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- Oxidative carbon-carbon bond cleavage of 1,2-diols to carboxylic acids/ketones by an inorganic-ligand supported iron catalyst
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The carbon-carbon bond cleavage of 1,2-diols is an important chemical transformation. Although traditional stoichiometric and catalytic oxidation methods have been widely used for this transformation, an efficient and valuable method should be further explored from the views of reusable catalysts, less waste, and convenient procedures. Herein an inorganic-ligand supported iron catalyst (NH4)3[FeMo6O18(OH)6]·7H2O was described as a heterogeneous molecular catalyst in acetic acid for this transformation in which hydrogen peroxide was used as the terminal oxidant. Under the optimized reaction conditions, carbon-carbon bond cleavage of 1,2-diols could be achieved in almost all cases and carboxylic acids or ketones could be afforded with a high conversion rate and high selectivity. Furthermore, the catalytic system was used efficiently to degrade renewable biomass oleic acid. Mechanistic insights based on the observation of the possible intermediates and control experiments are presented.
- Chen, Weiming,Xie, Xin,Zhang, Jian,Qu, Jian,Luo, Can,Lai, Yaozhu,Jiang, Feng,Yu, Han,Wei, Yongge
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supporting information
p. 9140 - 9146
(2021/11/23)
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- Electrochemical synthesis of quinazolinone: via I2-catalyzed tandem oxidation in aqueous solution
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The development of protocols for synthesizing quinazolinones using biocompatible catalysts in aqueous medium will help to resolve the difficulties of using green and sustainable chemistry for their synthesis. Herein, using I2 in coordination with electrochemical synthesis induced a C-H oxidation reaction which is reported when using water as the environmentally friendly solvent to access a broad range of quinazolinones at room temperature. The reaction mechanism strongly showed that I2 cooperates electrochemically promoted the oxidation of alcohols, then effectively cyclizing amides to various quinazolinones.
- Hou, Huiqing,Ma, Xinhua,Lin, Yingying,Lin, Jin,Sun, Weiming,Wang, Lei,Xu, Xiuzhi,Ke, Fang
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p. 17721 - 17726
(2021/05/29)
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- CBZ6 as a Recyclable Organic Photoreductant for Pinacol Coupling
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A recyclable organic photoreductant (1 mol % CBZ6)-catalyzed reductive (pinacol) coupling of aldehydes, ketones, and imines has been developed. Irradiated by purple light (407 nm) using triethylamine as an electron donor, a variety of 1,2-diols and 1,2-diamines could be prepared. The oxidation potential of the excited state of CBZ6 is established as -1.92 V (vs saturated calomel electrode (SCE)). The relative high reductive potential enables the reductive coupling of carbonyl compounds and their derivatives. CBZ6 can be prepared in gram scale and is acid/base- or air-stable. It could be applied in large-scale photoreductive synthesis and recovered in high yield after the reaction.
- Wang, Hua,Qu, Jian-Ping,Kang, Yan-Biao
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p. 2900 - 2903
(2021/05/05)
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- Photocatalytic pinacol C-C coupling and jet fuel precursor production on ZnIn2S4nanosheets
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Visible light-driven C-C bond formation has attracted increasing attention recently, thanks to the advance in molecular photosensitizers and organometallic catalysts. Nevertheless, these homogeneous methodologies typically necessitate the utilization of noble metal-based (e.g., Ir, Ru, etc.) photosensitizers. In contrast, solid-state semiconductors represent an attractive alternative but remain less explored for C-C bond-forming reactions driven by visible-light irradiation. Herein, we report that photocatalytic pinacol C-C coupling of benzaldehyde to hydrobenzoin can be achieved on two-dimensional ZnIn2S4 nanosheets upon visible-light irradiation in the presence of a sacrificial electron donor (e.g., triethylamine). We further demonstrate that it is feasible to take advantage of both excited electrons and holes in irradiated ZnIn2S4 for C-C coupling reactions in the absence of any sacrificial reagent if benzyl alcohol is utilized as the starting substrate, maximizing the energy efficiency of photocatalysis and circumventing any byproducts. In this case, industrially important benzoin and deoxybenzoin are formed as the final products. More importantly, by judiciously tuning the photocatalytic conditions, we are able to produce either benzoin or deoxybenzoin with unprecedented high selectivity. The critical species during the photocatalytic process were systematically investigated with various scavengers. Finally, such a heterogeneous photocatalytic pinacol C-C coupling strategy was applied to produce a jet fuel precursor (e.g., hydrofuroin) from biomass-derived furanics (e.g., furfural and furfural alcohol), highlighting the promise of our approach in practical applications.
- Cao, Zhi,Han, Guanqun,Liu, Xingwu,Sun, Yujie
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p. 9346 - 9355
(2020/10/09)
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- Synthesis of 1,2-amino alcohols by decarboxylative coupling of amino acid derived α-amino radicals to carbonyl compounds: Via visible-light photocatalyst in water
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A general and efficient visible-light photoredox-catalysed decarboxylative radical coupling reaction of N-aryl amino acids with aldehydes or ketones for the synthesis of various 1,2-amino alcohols by using water as the solvent at room temperature is described. This protocol is characterised by broad substrate scopes, mild reaction conditions and amenability to gram-scale synthesis, which opens up a simple, mild but effective method to produce 1,2-amino alcohols from readily available starting materials.
- Pan, Shulei,Jiang, Min,Hu, Jinjin,Xu, Ruigang,Zeng, Xiaofei,Zhong, Guofu
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supporting information
p. 336 - 341
(2020/02/13)
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- Dendrimer crown-ether tethered multi-wall carbon nanotubes support methyltrioxorhenium in the selective oxidation of olefins to epoxides
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Benzo-15-crown-5 ether supported on multi-wall carbon nanotubes (MWCNTs) by tethered poly(amidoamine) (PAMAM) dendrimers efficiently coordinated methyltrioxorhenium in the selective oxidation of olefins to epoxides. Environmentally friendly hydrogen peroxide was used as a primary oxidant. Up to first and second generation dendrimer aggregates were prepared by applying a divergent PAMAM methodology. FT-IR, XRD and ICP-MS analyses confirmed the effective coordination of methyltrioxorhenium by the benzo-15-crown-5 ether moiety after immobilization on MWCNTs. The novel catalysts converted olefins to the corresponding epoxides in high yield without the use of Lewis base additives, or anhydrous hydrogen peroxide, the catalyst being stable for more than six oxidative runs. In the absence of the PAMAM structure, the synthesis of diols largely prevailed.
- Bizzarri, Bruno Mattia,Botta, Lorenzo,Crucianelli, Marcello,Fanelli, Angelica,Ferella, Francesco,Gontrani, Lorenzo,Sadun, Claudia,Saladino, Raffaele
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p. 17185 - 17194
(2020/05/18)
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- Photocatalytic Coproduction of Deoxybenzoin and H2 through Tandem Redox Reactions
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Photocatalytic H2 evolution from organic feedstocks with simultaneous utilization of photogenerated holes achieves solar energy storage and coproduces value-Added chemicals. Here we show visible-light H2 production from benzyl alcohol (BAL) with controllable generation of deoxybenzoin (DOB) or benzoin (BZ) through tandem redox reactions. Particularly, DOB synthesis circumvents the use of expensive feedstocks and environmentally unfriendly catalysts that are required previously. Under the irradiation of blue LEDs, the key of steering the major product to DOB rather than BZ is to decrease the conduction band bottom potentials of the ZnIn sulfide catalysts by increasing the Zn/In ratio, which results in the dehydration of intermediate hydrobenzoin (HB) to DOB proceeding in a redox-neutral mechanism and consuming an electron-hole pair. As a proof of concept, this method is used to synthesize DOB derivatives in gram scale.
- Luo, Nengchao,Hou, Tingting,Liu, Shiyang,Zeng, Bin,Lu, Jianmin,Zhang, Jian,Li, Hongji,Wang, Feng
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p. 762 - 769
(2020/01/02)
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- Direct Asymmetric Hydrogenation and Dynamic Kinetic Resolution of Aryl Ketones Catalyzed by an Iridium-NHC Exhibiting High Enantio- and Diastereoselectivity
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A chiral iridium carbene-oxazoline catalyst is reported that is able to directly and efficiently hydrogenate a wide variety of ketones in excellent yields and good enantioselectivity (up to 93 % ee). Moreover, when using racemic α-substituted ketones, excellent diastereoselectivities were obtained (dr 99:1) by dynamic kinetic resolution of the in situ formed enolate. Overall, the herein described hydrogenation occurs under ambient conditions using low hydrogen pressures, providing a direct and atom efficient method towards chiral secondary alcohols.
- Ayya Swamy P, Chinna,Varenikov, Andrii,de Ruiter, Graham
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supporting information
p. 2333 - 2337
(2020/02/11)
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- The construction of novel and efficient hafnium catalysts using naturally existing tannic acid for Meerwein-Ponndorf-Verley reduction
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The conversion of carbonyl compounds into alcohols or their derivatives via the catalytic transfer hydrogenation (CTH) process known as Meerwein-Ponndorf-Verley reduction is an important reaction in the reaction chain involved in biomass transformation. The rational design of efficient catalysts using natural and renewable materials is critical for decreasing the catalyst cost and for the sustainable supply of raw materials during catalyst preparation. In this study, a novel hafnium-based catalyst was constructed using naturally existing tannic acid as the ligand. The prepared hafnium-tannic acid (Hf-TA) catalyst was characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and thermogravimetry (TG). Hf-TA was applied in the conversion of furfuraldehyde (FD) to furfuryl alcohol (FA) using isopropanol (2-PrOH) as both the reaction solvent and the hydrogen source. Both preparation conditions and the effects of the reaction parameters on the performance of the catalyst were studied. Under the relatively mild reaction conditions of 70 °C and 3 h, FD (1 mmol) could be converted into FA with a high yield of 99.0%. In addition, the Hf-TA catalyst could be reused at least ten times without a notable decrease in activity and selectivity, indicating its excellent stability. It was proved that Hf-TA could also catalyze the conversion of various carbonyl compounds with different structures. The high efficiency, natural occurrence of tannic acid, and facile preparation process make Hf-TA a potential catalyst for applications in the biomass conversion field.
- Deng, Lijuan,Hao, Jianxiu,He, Runxia,Li, Na,Liu, Quansheng,Wang, Xiaolu,Zhao, Hongye,Zhi, Keduan,Zhou, Huacong
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p. 6944 - 6952
(2020/03/03)
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- Ultrasound Assisted the Synthesis of 1,3-Dioxolane Derivatives from the Reaction of Epoxides or 1,2-Diols with Various Ketones Using Graphene Oxide Catalyst
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Abstract: The main objective of this study concerns the sonochemical synthesis of 1,3-dioxolane derivatives using graphene oxide catalyst by applying two methods. In the first method, we described the synthesis of 1,3-dioxolane by ring-opening of epoxides in the presence of ketones catalyzed by graphene oxide (GO) under ultrasonic irradiation. In the second sonochemical procedure, we described the synthesis of 1,3-dioxolane derivatives by the reaction of 1,2-diols with ketones using same GO catalyst. Mild reaction conditions, high yields, short reaction times, reusability of catalyst and easy isolation of the products make the developed methods very useful. Graphic Abstract: [Figure not available: see fulltext.]
- Mirza-Aghayan, Maryam,Mohammadi, Marzieh,Ahmadi, Zahra,Boukherroub, Rabah
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p. 2959 - 2969
(2020/04/22)
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- Chromium-Catalyzed Linear-Selective Alkylation of Aldehydes with Alkenes
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We developed a chromium-catalyzed, photochemical, and linear-selective alkylation of aldehydes with alkylzirconium species generated in situ from a wide range of alkenes and Schwartz's reagent. Photochemical homolysis of the C-Zr bond afforded alkyl radicals, which were then trapped by a chromium complex catalyst to generate the alkylchromium(III) species for polar addition to aldehydes. The reaction proceeded with high functional group tolerance at ambient temperature under visible-light irradiation.
- Hirao, Yuki,Kanai, Motomu,Katayama, Yuri,Mitsunuma, Harunobu
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supporting information
(2020/11/18)
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- How the sustainable solvent water unleashes the photoredox catalytic potential of ruthenium polypyridyl complexes for pinacol couplings
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By complementing laser flash photolysis with product studies in visible-LED driven syntheses, we show that the one-electron reduced forms OER of tris(2,2′-bipyridine)ruthenium(ii) and its more reactive derivative with 4,4′-dimethylated ligands exhibit a reductive power greater by 0.2 eV in water than in acetonitrile; and that this difference allows the reduction of carbonyl compounds, and thus pinacol couplings, in aqueous medium via ruthenium-based photoredox catalysis as an alternative to using more expensive and less photostable higher-energy complexes (e.g., of iridium). Ascorbate serves as sacrificial donor to access OER. SDS micelles or cyclodextrins as carriers help overcome solubility problems of less hydrophilic substrates, and more reactive water-soluble substrates can even be coupled at neutral pH, such that the mild conditions make the process fully sustainable.
- Naumann, Robert,Goez, Martin
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p. 4470 - 4474
(2019/08/21)
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- Bifunctional copper-based photocatalyst for reductive pinacol-type couplings
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A bifunctional copper-based photocatalyst has been prepared that employs a pyrazole-pyridine ligand incorporating a sulfonamide moiety that functions as an intramolecular hydrogen-bond donor for a photochemical PCET process. In typical reductive PCET processes, the photocatalyst and H-bond donor must have an appropriate redox potential and pKa, respectively, to promote the PCET. When working in concert in a bifunctional catalyst such as Cu(pypzs)(BINAP)BF4, the pKa of the H-bond donor can have an acidity that is orders of magnitude less and still efficiently promote the PCET process. A reductive pinacol-type coupling can be performed using a base-metal derived photocatalyst to afford valuable diols (24 examples, 46-99% yield), from readily available aldehydes and ketones.
- Caron, Antoine,Morin, émilie,Collins, Shawn K.
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p. 9458 - 9464
(2019/10/11)
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- ORGANIC ELECTROLUMINESCENT DEVICE, ORGANIC ELECTROLUMINESCENT DISPLAY DEVICE INCLUDING THE SAME, AND ORGANOMETALLIC COMPOUND FOR ORGANIC ELECTROLUMINESCENT DEVICE
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An organic electroluminescent device includes a first electrode, a hole transport region provided on the first electrode, an emission layer provided on the hole transport region, an electron transport region provided on the emission layer, and a second electrode provided on the electron transport region, wherein the emission layer includes an organometallic compound represented by Formula 1.
- -
-
Paragraph 0171; 0172
(2019/08/20)
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- HETEROCYCLIC COMPOUND AND ORGANIC LIGHT-EMITTING DEVICE INCLUDING THE SAME
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An organic light-emitting device and a heterocyclic compound, the device including a first electrode; a second electrode facing the first electrode; and an organic layer between the first electrode and the second electrode and including an emission layer, wherein the emission layer includes a compound represented by Formula 1A or a compound represented by Formula 1B:
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-
Paragraph 0403; 0404
(2019/09/06)
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- Isothiourea-Catalysed Sequential Kinetic Resolution of Acyclic (±)-1,2-Diols
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The isothiourea-catalysed acylative kinetic resolution of a range of acyclic (±)-1,2-diols using 1 molpercent of catalyst under operationally simple conditions is reported. Significantly, the bifunctional nature of (±)-1,2-diols was exploited in a sequential double kinetic resolution, in which both kinetic resolutions operate synergistically to provide access to highly enantioenriched products. The principles that underpin this process are discussed, and selectivity factors for the individual kinetic resolution steps are reported in a model system.
- Greenhalgh, Mark D.,Harrer, Siegfried,Neyyappadath, Rifahath M.,Smith, Andrew D.
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p. 1555 - 1560
(2019/08/07)
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- Sodium Hypochlorite Pentahydrate as a Reagent for the Cleavage of trans-Cyclic Glycols
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Sodium hypochlorite pentahydrate (NaOCl·5H2O) can be used toward the efficient glycol cleavage of trans-cyclic glycols, which are generally resistant to this transformation. Interestingly, the reaction of cis-cyclic glycols with NaOCl·5H2O is slower than that observed for the corresponding trans-isomer. This trans selectivity is in sharp contrast to traditional oxidants used for glycol cleavage. Acyclic glycols can also react efficiently with NaOCl·5H2O to form their corresponding carbonyl compounds in high yield.
- Kirihara, Masayuki,Osugi, Rie,Saito, Katsuya,Adachi, Kouta,Yamazaki, Kento,Matsushima, Ryoji,Kimura, Yoshikazu
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p. 8330 - 8336
(2019/06/24)
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- Flat and Efficient H CNN and CNN Pincer Ruthenium Catalysts for Carbonyl Compound Reduction
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The bidentate HCNN dicarbonyl ruthenium complexes trans,cis-[RuCl2(HCNN)(CO)2] (1-3) and trans,cis-[RuCl2(ampy)(CO)2] (1a) were prepared by reaction of [RuCl2(CO)2]n with 1-[6-(4′-methylphenyl)pyridin-2-yl]methanamine, benzo[h]quinoline (HCNN), and 2-(aminomethyl)pyridine (ampy) ligands. Alternatively, the derivatives 1-3 were obtained from the reaction of RuCl3 hydrate with HCO2H and HCNN. The pincer CNN cis-[RuCl(CNN)(CO)2] (4) was isolated from 1 by reaction with NEt3. The monocarbonyl complexes trans-[RuCl2(HCNN)(PPh3)(CO)] (5-7) were synthesized from [RuCl2(dmf)(PPh3)2(CO)] and HCNN ligands, while the diacetate trans-[Ru(OAc)2(HCNN)(PPh3)(CO)] (8) was obtained from [Ru(OAc)2(PPh3)2(CO)]. Carbonylation of cis-[RuCl(CNN)(PPh3)2] with CO afforded the pincer derivatives [RuCl(CNN)(PPh3)(CO)] (9-11). Treatment of 9 with Na[BArf]4 and PPh3 gave the cationic complex trans-[Ru(CNN)(PPh3)2(CO)][BArf4] (12). The dicarbonyl derivatives 1-4, in the presence of PPh3 or PCy3, and the monocarbonyl complexes 5-12 catalyzed the transfer hydrogenation (TH) of acetophenone (a) in 2-propanol at reflux (S/C = 1000-100000 and TOF up to 100000 h-1). Compounds 1-3, with PCy3, and 6 and 8-10 were proven to catalyze the TH of carbonyl compounds, including α,β-unsaturated aldehydes and bulky ketones (S/C and TOF up to 10000 and 100000 h-1, respectively). The derivatives 1-3 with PCy3 and 5 and 6 catalyzed the hydrogenation (HY) of a (H2, 30 bar) at 70 °C (S/C = 2000-10000). Complex 5 was active in the HY of diaryl ketones and aryl methyl ketones, leading to complete conversion at S/C = 10000.
- Giboulot, Steven,Baldino, Salvatore,Ballico, Maurizio,Figliolia, Rosario,P?thig, Alexander,Zhang, Shuanming,Zuccaccia, Daniele,Baratta, Walter
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p. 1127 - 1142
(2019/03/14)
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- Preparation of monocarbonyl ruthenium complexes bearing bidentate nitrogen and phosphine ligands and their catalytic activity in carbonyl compound reduction
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Monocarbonyl complexes [RuCl2(CO)(PR3)(NN)] (R = Cy, NN = en 1, ampy 2; R = iPr; NN = en 3) have been prepared in a one pot reaction from [RuCl2(CO)(dmf)(PPh3)2], PR3 and the NN ligand in CH2Cl2. Treatment of [Ru(OAc)2(CO)(PPh3)2] with NN ligands in methanol gives the cationic derivatives [Ru(OAc)(CO)(PPh3)(NN)]OAc (NN = en 4, ampy 5) in which one acetate acts as a bidentate ligand, whereas the other is not coordinated. Diphosphine complexes [RuCl2(CO)(PP)(PPh3)] (PP = dppb 6, dppf 7, (R)-BINAP 8, (R,Sp)-Josiphos 9 and (R,R)-Skewphos 10) have been obtained starting from [RuCl2(CO)(dmf)(PPh3)2] and the PP ligand in CHCl3 or toluene at reflux. The reaction of [Ru(OAc)2(CO)(PPh3)2] with PP in CH2Cl2 or toluene affords the fluxional acetate derivatives [Ru(OAc)2(CO)(PP)] (PP = dppb 11, dppf 12, (R)-BINAP 13, and (R,R)-Skewphos 14). The cationic diphosphine complexes [RuCl(CO)(PP)(en)]Cl (PP = dppb 15, dppf 16) are prepared from [RuCl2(CO)(dmf)(PPh3)2], PP and en in CH2Cl2 or, alternatively, from [RuCl2(CO)2]n or the 6, 7 derivatives. Similarly, [Ru(OAc)(CO)(PP)(NN)]OAc (PP = dppb, NN = en 17, ampy 18; PP = dppf, NN = en 19, ampy 20) are isolated starting from [Ru(OAc)2(CO)(PPh3)2], PP and NN ligands or from 11, 12. The derivatives [Ru(OAc)2(CO)(PP)] show a fluxional behavior in solution as the result of the flexible coordination of acetate ligands. These complexes are found to be active in the transfer hydrogenation and hydrogenation of ketones and aldehydes, including furfural derivatives, at an S/C up to 10000 and a TOF up to 18000 h-1.
- Giboulot, Steven,Comuzzi, Clara,Del Zotto, Alessandro,Figliolia, Rosario,Lippe, Giovanna,Lovison, Denise,Strazzolini, Paolo,Susmel, Sabina,Zangrando, Ennio,Zuccaccia, Daniele,Baldino, Salvatore,Ballico, Maurizio,Baratta, Walter
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supporting information
p. 12560 - 12576
(2019/08/26)
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- Efficient acceptorless photo-dehydrogenation of alcohols and: N -heterocycles with binuclear platinum(ii) diphosphite complexes
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Although photoredox catalysis employing Ru(ii) and Ir(iii) complexes as photocatalysts has emerged as a versatile tool for oxidative C-H functionalization under mild conditions, the need for additional reagents acting as electron donor/scavenger for completing the catalytic cycle undermines the practicability of this approach. Herein we demonstrate that photo-induced oxidative C-H functionalization can be catalysed with high product yields under oxygen-free and acceptorless conditions via inner-sphere atom abstraction by binuclear platinum(ii) diphosphite complexes. Both alcohols (51 examples), particularly the aliphatic ones, and saturated N-heterocycles (24 examples) can be efficiently dehydrogenated under light irradiation at room temperature. Regeneration of the photocatalyst by means of reductive elimination of dihydrogen from the in situ formed platinum(iii)-hydride species represents an alternative paradigm to the current approach in photoredox catalysis.
- Zhong, Jian-Ji,To, Wai-Pong,Liu, Yungen,Lu, Wei,Che, Chi-Ming
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p. 4883 - 4889
(2019/05/16)
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- Reductive coupling between aromatic aldehydes and ketones or imines by copper catalysis
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The copper-catalyzed reductive coupling of two different carbonyl compounds has been achieved. The reaction of aromatic aldehydes and arylketones with a silylboronate in the presence of a catalytic amount of a CuCl-N-heterocyclic carbene (NHC) complex and a stoichiometric amount of alkoxide base yielded cross-coupled 1,2-diol derivatives. A reaction pathway is proposed that involves the catalytic formation of a nucleophilic α-silyloxybenzylcopper(I) species from the aromatic aldehyde and its subsequent coupling with the arylketone. This process was amenable to asymmetric catalysis. This copper catalyst system also enabled the reductive coupling between aromatic aldehydes and imines.
- Takeda, Mitsutaka,Mitsui, Atsuhisa,Nagao, Kazunori,Ohmiya, Hirohisa
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supporting information
p. 3664 - 3669
(2019/02/14)
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- Substrate and inhibitor selectivity, and biological activity of an epoxide hydrolase from Trichoderma reesei
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Epoxide hydrolases (EHs) are present in all living organisms and catalyze the hydrolysis of epoxides to the corresponding vicinal diols. EH are involved in the metabolism of endogenous and exogenous epoxides, and thus have application in pharmacology and biotechnology. In this work, we describe the substrates and inhibitors selectivity of an epoxide hydrolase recently cloned from the filamentous fungus Trichoderma reesei QM9414 (TrEH). We also studied the TrEH urea-based inhibitors effects in the fungal growth. TrEH showed high activity on radioative and fluorescent surrogate and natural substrates, especially epoxides from docosahexaenoic acid. Using a fluorescent surrogate substrate, potent inhibitors of TrEH were identified. Interestingly, one of the best compounds inhibit up to 60% of T. reesei growth, indicating an endogenous role for TrEH. These data make TrEH very attractive for future studies about fungal metabolism of fatty acids and possible development of novel drugs for human diseases.
- de Oliveira, Gabriel S.,Adriani, Patricia P.,Wu, Hao,Morisseau, Christophe,Hammock, Bruce D.,Chambergo, Felipe S.
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p. 371 - 379
(2018/11/23)
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- Application of coumarin dyes for organic photoredox catalysis
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Here we report the application of readily prepared and available coumarin dyes for photoredox catalysis, which are able to mimic powerful reductant [Ir(iii)] complexes. Coumarin derivatives 9 and 10 were employed as photoreductants in pinacol coupling and in other reactions, in the presence of Et3N as a sacrificial reducing agent. As the electronic, photophysical, and steric properties of coumarins could be varied, a wide applicability to several classes of photoredox reactions is predicted.
- Gualandi, Andrea,Rodeghiero, Giacomo,Della Rocca, Emanuele,Bertoni, Francesco,Marchini, Marianna,Perciaccante, Rossana,Jansen, Thomas Paul,Ceroni, Paola,Cozzi, Pier Giorgio
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supporting information
p. 10044 - 10047
(2018/09/13)
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- Solvent free facile room temperature reduction of aromatic carbonyl and nitro compounds by zn/Conc. HCl system - An experimental and DFT study
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This experimental and DFT studies involve a novel technique for the reduction of aromatic carbonyl/nitro compounds to the corresponding alcohols/amines, in high yield under laboratory conditions. The reducing species is the nascent hydrogen generated by the Zn/HCl system. The novelty of this work is that the comparison of yield with and without solvent. The yield is increased by many folds in the solvent free method compared to the solvent method reported earlier. The technique followed is to make a 'slurry' of the substrate with zinc dust (zinc slurry) and to add (in small portion of the dry slurry) to the optimized amount of conc. HCl, over a period of 3 to 4 h at room temperature. In this technique the substrate, adsorbed on zinc dust being very proximal to the site of generation nascent hydrogen, the reduction is very effective and the yield is high. The novelty is that zinc dust acts as catalyst (adsorbent role) and reactant (hydrogen generation role). The DFT study with B3LYP/6.311g ++ (d,p) basis set revealed that the stability of first formed free radical (energy factor) and the homo nuclear nature of carbonyl and nitro group (charge factor) decide the yield. The electrostatic potential calculated by DFT studies correlates well with Mullikan charges in deciding the charge factor. The free radical mechanism was confirmed by the formation of pinacol coupled product in one instance.
- Rajamathe,Bhuvaneswari
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p. 639 - 644
(2018/02/09)
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- Organic photoredox catalyst with substrate-capture ability: A perylene derivative bearing urethane moiety for reductive coupling of ketones and aldehydes under visible light
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A perylene derivative bearing a urethane moiety served as an efficient photoredox catalyst for the reductive coupling of ketones and aldehydes under visible light, implicating that the urethane moiety captured substrates through hydrogen bonds to lower the LUMO levels of the captured substrates, thus promoting single electron transfer from the reductant anion radical of the perylene moiety to the substrates.
- Okamoto, Shusuke,Tsujioka, Hiroki,Sudo, Atsushi
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supporting information
p. 369 - 372
(2018/03/05)
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- Photocatalytic Barbier reaction-visible-light induced allylation and benzylation of aldehydes and ketones
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We report a photocatalytic version of the Barbier type reaction using readily available allyl or benzyl bromides and aromatic aldehydes or ketones as starting materials to generate allylic or benzylic alcohols. The reaction proceeds at room temperature under visible light irradiation with the organic dye 3,7-di(4-biphenyl)1-naphthalene-10-phenoxazine as a photocatalyst and DIPEA as sacrificial electron donor. The proposed cross-coupling mechanism of a ketyl- and an allyl or benzyl radical is supported by spectroscopic investigations and cyclic voltammetry measurements.
- Berger, Anna Lucia,Donabauer, Karsten,K?nig, Burkhard
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p. 7230 - 7235
(2018/10/02)
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- Air-Stable Blue Phosphorescent Tetradentate Platinum(II) Complexes as Strong Photo-Reductant
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Strong photo-reductants have applications in photo-redox organic synthesis involving reductive activation of C?X(halide) and C=O bonds. We report herein air-stable PtII complexes supported by tetradentate bis(phenolate-NHC) ligands having peripheral electron-donating N-carbazolyl groups. Photo-physical, electrochemical, and computational studies reveal that the presence of N-carbazolyl groups enhances the light absorption and redox reversibility because of its involvement into the frontier MOs in both ground and excited states, making the complexes robust strong photo-reductant with E([Pt]+/*) over ?2.6 V vs. Cp2Fe+/0. The one-electron reduced [Pt]? species are stronger reductants with EPC([Pt]0/?) up to ?3.1 V vs. Cp2Fe+/0. By virtue of the strong reducing nature of these species generated upon light excitation, they can be used in light-driven reductive coupling of carbonyl compounds and reductive debromination of a wide range of unactivated aryl bromides.
- Li, Kai,Wan, Qingyun,Yang, Chen,Chang, Xiao-Yong,Low, Kam-Hung,Che, Chi-Ming
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supporting information
p. 14129 - 14133
(2018/10/15)
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- Cyclometalated Dicarbonyl Ruthenium Catalysts for Transfer Hydrogenation and Hydrogenation of Carbonyl Compounds
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The dicarbonyl complex RuCl2(L)2(CO)2 (1) was easily prepared by reaction of ruthenium chloride hydrate with formic acid and L (L = (2,6-Me2C6H3)PPh2) in ethanol at reflux, via the [RuCl2(CO)2]n intermediate. Alternatively, 1 was obtained from [RuCl2(CO)3]2 and L by CO elimination. Reaction of 1 with NEt3 in toluene at reflux afforded the cyclometalated derivative RuCl{(2-CH2-6-MeC6H3)PPh2}(L)(CO)2 (2). A simple one-pot synthesis of 2 was achieved by treatment of RuCl3 hydrate with formic acid, L, and NEt3. The cyclometalated dicarbonyl complexes [Ru{(2-CH2-6-MeC6H3)PPh2}(NN)(CO)2]Cl (NN = ethylenediamine, 3; 2-(aminomethyl)pyridine, 4; (R,R)-1,2-diphenylethane-1,2-diamine, 5) were isolated by reaction of 2 with the corresponding dinitrogen ligand in methanol at reflux. Complexes 1-4 catalyze the transfer hydrogenation (TH) of acetophenone in 2-propanol at reflux (S/C = 1000 and TOF up to 30 000 h-1) with alkali base (1-5 mol %), whereas 5 leads to (S)-1-phenylethanol with 68% ee. The derivatives 1-5 catalyze the hydrogenation (HY) of several ketones (H2, 30 bar) at 70 °C in MeOH and EtOH with KOtBu (2 mol %) (S/C and TOF up to 25 000 and 14 000 h-1). Addition of NN ligands to 1 and 2 in situ increases both the TH and HY activity, with ampy displaying the better performance. Heating of the cationic complex 3 in solid state and in solution leads to decarbonylation, affording the neutral monocarbonyl compound RuCl{(2-CH2-6-MeC6H3)PPh2}(en)(CO) (6) which was found active in the ketone HY.
- Giboulot, Steven,Baldino, Salvatore,Ballico, Maurizio,Nedden, Hans Günter,Zuccaccia, Daniele,Baratta, Walter
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p. 2136 - 2146
(2018/07/25)
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- Aminotriazole Mn(I) Complexes as Effective Catalysts for Transfer Hydrogenation of Ketones
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A catalytic system based on complexes comprising abundant and cheap manganese together with readily available aminotriazole ligands is reported. The new Mn(I) complexes are catalytically competent in transfer hydrogenation of ketones with 2-propanol as hydrogen source. The reaction proceeds under mild conditions at 80 °C for 20 h with 3 % of catalyst loading using either KOtBu or NaOH as base. Good to excellent yields were obtained for a wide substrate scope with broad functional group tolerance. The obtained results by varying the substitution pattern of the ligand are consistent with an out-sphere mechanism for the H-transfer.
- Martínez-Ferraté, Oriol,Werlé, Christophe,Franciò, Giancarlo,Leitner, Walter
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p. 4514 - 4518
(2018/10/20)
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- Facile oxidation of alcohols to carboxylic acids in basic water medium by employing ruthenium picolinate cluster as an efficient catalyst
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Selective transformation of alcohols into carboxylic acids is a crucial process in industry for the synthesis of bulk chemicals. Current methods for the production of acids involve oxygen under pressure or toxic reagents like ruthenium chlorite or iodate or chromium oxides. Herein, we report the preparation of [Ru3(CO)8(C5H4NCO2)2] cluster which is an efficient catalyst precursor for the conversion of primary alcohols into carboxylic acids under aerobic conditions. The catalytic process involves the use of NaOH in a water–isopropanol medium which gives a 90% yield of carboxylic acid (90% yield for benzoic acid in standard reaction). This clean process appears to be safe for the synthesis of various benzoic acids for both laboratory and also industrial purposes.
- Singh, Ajeet,Singh, Sandip K.,Saini, Anoop K.,Mobin, Shaikh M.,Mathur, Pradeep
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- Zinc-Mediated Efficient and Selective Reduction of Carbonyl Compounds
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We herein describe for the first time that an optimized combination of Zn and NH4Cl can be used for the selective reduction of aldehydes and ketones to the corresponding alcohols. The aldehyde and keto groups are selectively reduced in the presence of azide, cyano, epoxy, ester, and carbon–carbon double-bond functional groups. A broad functional-group compatibility, chemoselective reduction of aldehydes in the presence of ketones, and selective reduction of isatins at the C3 carbonyl group are the highlights of the present method.
- Mandal, Tirtha,Jana, Snehasish,Dash, Jyotirmayee
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p. 4972 - 4983
(2017/09/13)
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- Nickel-catalyzed reduction of ketones with water and triethylsilane
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The acetophenone (1a) reduction using catalytically active nickel complexes and water is an efficient and sustainable method to access a new methodology of transfer hydrogenation of ketones. When triethylsilane (Et3SiH) was used as sacrificial agent to promote the transfer hydrogenation from water, 1-phenylethanol (2a) was obtained in excellent yield along with silanol (Et3SiOH) as the reaction's driving force. Deuterium labeling studies were made using Et3SiD or D2O and these studies showed that both compounds participate as hydride sources for the ketone reduction. A scope of substrates was assessed, including a variety of mono/diketones, and α,β-unsaturated ketones, to yield the corresponding secondary alcohols and saturated ketones. Additionally, asymmetric transfer hydrogenation of mono-ketones was studied for the mixture of nickel/(bisphosphine or phospholane) as catalyst precursor, using H2O/Et3SiO system and ethanol as hydrogen sources.
- Castellanos-Blanco, Nahury,Flores-Alamo, Marcos,García, Juventino J.
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p. 324 - 332
(2017/06/29)
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- Base-Free Asymmetric Transfer Hydrogenation of 1,2-Di- and Monoketones Catalyzed by a (NH)2P2-Macrocyclic Iron(II) Hydride
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The hydride isonitrile complex [FeH(CNCEt3)(1 a)]BF4 (2) containing a chiral P2(NH)2 macrocycle (1 a), in the presence of 2-propanol as hydrogen donor, catalyzes the base-free asymmetric transfer hydrogenation (ATH) of prostereogenic ketones to alcohols and the hemihydrogenation of benzils to benzoins, which contain a base-labile stereocenter. Benzoins are formed in up to 83 % isolated yield with enantioselectivity reaching 95 % ee. Ketones give the same enantioselectivity observed with the parent catalytic system [Fe(CNCEt3)2(1 a)] (3 a) that operates with added NaOtBu.
- De Luca, Lorena,Mezzetti, Antonio
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p. 11949 - 11953
(2017/09/20)
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- Selective One-Pot Three-Step Cascade Reaction: From Aromatic Aldehydes to 2,2-Diphenylethanol Derivatives
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We report herein a green and scalable one-pot, three-step, pinacol-coupling-rearrangement-reduction cascade reaction useful for the formation of 2,2-diphenylethanol derivatives. The reaction is carried out in water in the presence of a commercially available and regenerable supported acid under moderate pressure. A dozen of aromatic aldehydes have been successfully submitted to the standard protocol giving the target 2,2-diarylethanol derivatives in good yield (70-85%).
- Billamboz, Muriel,Imbs, Claire,Banaszak-Léonard, Estelle,Len, Christophe
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p. 835 - 843
(2017/06/23)
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- Secondary amides as hydrogen atom transfer promoters for reactions of samarium diiodide
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Two secondary amides (N-methylacetamide and 2-pyrrolidinone) were used as additives with SmI2 in THF to estimate the extent of N-H bond weakening upon coordination. Mechanistic and synthetic studies demonstrate significant bond-weakening, providing a reagent system capable of reducing a range of substrates through formal hydrogen atom transfer.
- Chciuk, Tesia V.,Li, Anna M.,Vazquez-Lopez, Andres,Anderson, William R.,Flowers, Robert A.
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supporting information
p. 290 - 293
(2017/11/27)
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- An efficient FeCl3-mediated approach for reduction of ketones through N-heterocyclic carbene boranes
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An efficient FeCl3-mediated approach for reduction of ketones by NHC-BH3 has been developed. A series of ketones were smoothly converted to the corresponding alcohols in good to excellent yields through NHC-BH3 reductive process.
- Wang, Ming-Hui,Chen, Ling-Yan
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supporting information
p. 732 - 735
(2017/03/31)
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- Biginelli reaction of vicinal diols: A new route for one-pot synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives
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Background: 3,4-Dihydropyrimidin-2(1H)-one derivatives are an important class of nitrogen heterocycles. These compounds present a wide range of biological activities viz antibacterial, antifungal, and antidiabetic. Although many synthetic methods are available in the literature for the synthesis of these molecules, many of these methods have their own limitations such as use of excess of expensive catalyst and poor yields. Methods: The synthesis of 3,4-dihydropyrimidin-2(1H)-one derivatives is developed through the reaction of 1,2-diols, ethyl acetoacetate and urea in the presence of lead tetraacetate in dry ethanol under reflux conditions. Results: A series of 3,4-dihydropyrimidin-2(1H)-one derivatives were synthesized in good yields (82-95%) under reflux for 2-3.5 hours in ethanol solvent. The structural assignments of these compounds were made on the basis of elemental analysis and spectroscopic data. Conclusion: This protocol is an alternative to existing procedure for the synthesis of Biginelli compounds. The present methodology reduces the number of steps in total synthesis.
- Jagadishbabu, Narasashetty,Shivashankar, Kalegowda
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p. 330 - 336
(2017/07/26)
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- Method for Highly Enantioselective Ligation of Two Chiral C(sp3) Stereocenters
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A method is described for the joining of two α-lithiated C(sp3) stereocenters efficiently and with retention of configuration. The key step involves the effective removal of two electrons from a chiral organocuprate R2CuLi, by i-propyl 2,4-dinitrobenzoate to form a Cu(III) complex that undergoes at -90 °C accelerated reductive elimination enantioselectively and exclusively without the formation of free radicals.
- Bhimireddy, Eswar,Corey
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supporting information
p. 11044 - 11047
(2017/08/22)
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- Efficient Visible Light-Driven Splitting of Alcohols into Hydrogen and Corresponding Carbonyl Compounds over a Ni-Modified CdS Photocatalyst
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Splitting of alcohols into hydrogen and corresponding carbonyl compounds has potential applications in hydrogen production and chemical industry. Herein, we report that a heterogeneous photocatalyst (Ni-modified CdS nanoparticles) could efficiently split alcohols into hydrogen and corresponding aldehydes or ketones in a stoichiometric manner under visible light irradiation. Optimized apparent quantum yields of 38%, 46%, and 48% were obtained at 447 nm for dehydrogenation of methanol, ethanol, and 2-propanol, respectively. In the case of dehydrogenation of 2-propanol, a turnover number of greater than 44-000 was achieved. To our knowledge, these are unprecedented values for photocatalytic splitting of liquid alcohols under visible light to date. Besides, the current catalyst system functions well with other aliphatic and aromatic alcohols, affording the corresponding carbonyl compounds with good to excellent conversion and outstanding selectivity. Moreover, mechanistic investigations suggest that an interface between Ni nanocrystal and CdS plays a key role in the reaction mechanism of the photocatalytic splitting of alcohol.
- Chai, Zhigang,Zeng, Ting-Ting,Li, Qi,Lu, Liang-Qiu,Xiao, Wen-Jing,Xu, Dongsheng
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supporting information
p. 10128 - 10131
(2016/08/31)
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- N-Heterocyclic olefins as ancillary ligands in catalysis: A study of their behaviour in transfer hydrogenation reactions
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The Ir(i) complexes [Ir(cod)(κP,C,P′-NHOPPh2)]PF6 and [IrCl(cod)(κC-NHOOMe)] (cod = 1,5-cyclooctadiene, NHOPPh2 = 1,3-bis(2-(diphenylphosphanyl)ethyl)-2-methyleneimidazoline) and NHOOMe = 1,3-bis(2-(methoxyethyl)-2-methyleneimidazoline), both featuring an N-heterocyclic olefin ligand (NHO), have been tested in the transfer hydrogenation reaction; this representing the first example of the use of NHOs as ancillary ligands in catalysis. The pre-catalyst [Ir(cod)(κP,C,P′-NHOPPh2)]PF6 has shown excellent activities in the transfer hydrogenation of aldehydes, ketones and imines using iPrOH as a hydrogen source, while [IrCl(cod)(κC-NHOOMe)] decomposes throughout the reaction to give low yields of the hydrogenated product. Addition of one or two equivalents of a phosphine ligand to the latter avoids catalyst decomposition and significantly improves the reaction yields. The reaction mechanism has been investigated by means of stoichiometric studies and theoretical calculations. The formation of the active species ([Ir(κP,C,P′-NHOPPh2)(iPrO)]) has been proposed to occur via isopropoxide coordination and concomitant COD dissociation. Moreover, throughout the catalytic cycle the NHO moiety behaves as a hemilabile ligand, thus allowing the catalyst to adopt stable square planar geometries in the transition states, which reduces the energetic barrier of the process.
- Iturmendi, Amaia,García, Nestor,Jaseer,Munárriz, Julen,Sanz Miguel, Pablo J.,Polo, Victor,Iglesias, Manuel,Oro, Luis A.
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p. 12835 - 12845
(2016/08/24)
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- Nickel-catalyzed transfer hydrogenation of ketones using ethanol as a solvent and a hydrogen donor
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We report a nickel(0)-catalyzed direct transfer hydrogenation (TH) of a variety of alkyl-aryl, diaryl, and aliphatic ketones with ethanol. This protocol implies a reaction in which a primary alcohol serves as a hydrogen atom source and solvent in a one-pot reaction without any added base. The catalytic activity of the nickel complex [(dcype)Ni(COD)] (e) (dcype: 1,2-bis(dicyclohexyl-phosphine)ethane, COD: 1,5-cyclooctadiene), towards transfer hydrogenation (TH) of carbonyl compounds using ethanol as the hydrogen donor was assessed using a broad scope of ketones, giving excellent results (up to 99% yield) compared to other homogeneous phosphine-nickel catalysts. Control experiments and a mercury poisoning experiment support a homogeneous catalytic system; the yield of the secondary alcohols formed in the TH reaction was monitored by gas chromatography (GC) and NMR spectroscopy.
- Castellanos-Blanco, Nahury,Arévalo, Alma,García, Juventino J.
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p. 13604 - 13614
(2016/09/04)
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- (Caffeine) (tetrahydroborato)zinc complex [Zn(BH4 )2 (caf)]: A new stable and efficient reducing agent
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In this context, (Caffeine)(tetrahydroborato)zinc complex as white stable reducing agents [Zn(BH4 )2 (caf)], has been prepared by complexation of one equimolar amounts of zinc tetrahydroborate and one equimolar amounts of caffeine at room temperature. Also, [Zn(BH4 )2 (caf) ]has been used for reduce of a variety of carbonyl compounds such as aldehydes, ketones, α, β-unsaturated carbonyl compounds, acyloins and a-diketones to their corresponding alcohols in excellent yields (90-95%). The reduction reactions have been completed in appropriate times (30-90 min) by using of 0.5-1 equivalents of [Zn(BH4 )2 (caf)] in CH3 CN at room temperature or under reflux conditions.
- Abdollahpour, Fatemeh,Setamdideh, Davood
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p. 1787 - 1792
(2016/01/25)
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- (Acridine)(tetrahydroborato)zinc complex [Zn(BH4)2(acr)]: A new stable and efficient reducing agent
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(Acridine)(tetrahydroborato)zinc complex[Zn(BH4)2(acr)] has been prepared by complexation of oneequimolar amounts of zinc tetrahydroborate and one equimolar amounts of acridine at room temperatureas gray stable reducing agents. Also, [Zn(BH4)2(acr)] has been used for reduce of different carbonyl compounds such as aldehydes, ketones, α, β-unsaturated carbonyl compounds, acyloins and a-diketones to their corresponding alcohols in excellent yields (85-95%). The reduction reactions have been carried outwithin 30-120 min by using of 0.5-1 equivalents of [Zn(BH4)2(acr)] in CH3CN at room temperature or under reflux conditions.
- Mohammadi, Sina,Setamdideh, Davood
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p. 2395 - 2399
(2016/02/27)
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