- Synergistic effects of encapsulated phthalocyanine complexes in MIL-101 for the selective aerobic oxidation of tetralin
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Metal phthalocyanine complexes encapsulated in MIL-101, and used as "ship-in-a-bottle" catalysts, show outstanding TONs in the aerobic oxidation of tetralin.
- Kockrick, Emanuel,Lescouet, Tristan,Kudrik, Evgeny V.,Sorokin, Alexander B.,Farrusseng, David
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- Synthesis, characterization of (R)-2,2′-diamino-1,1′-binaphthyl mono-sulfonamide and its ruthenium complex and evaluation of the catalytic properties in transfer hydrogenation reactions
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(R)-2-amino-2′-(8-quinolinesulfonyl amino)-1,1′-binaphthyl is synthesized. Its ruthenium complex is shown to be an asymmetric catalyst for transfer hydrogenation reactions in high chemical yield and modest enantioselectivity. Single crystal diffraction studies of both the ligand and the ruthenium complex show strong π-stacking interactions between the quinoline ring and one of the naphthyl groups. The relationship between the structure and catalytic reactivity is also discussed.
- Cai, Lisheng,Han, Ying,Mahmoud, Hussein,Segal, Brent M.
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- Aerobic oxidation of fluorene to fluorenone over Co-Cu bimetal oxides
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Oxidation of sp3 C-H bonds has attracted increasing attention, and the aim of our work is to prepare catalysts for oxidation of sp3 C-H bonds using O2 without an initiator. In this paper, a series of Co-Cu bimetal oxides with different Co/Cu ratios were synthesized by a sol-gel method and tested for catalytic oxidation of fluorene to fluorenone using molecular oxygen as an oxidant in the absence of a radical initiator. The best catalytic performance was achieved over the Co0.7Cu0.3 catalyst and the catalysts could be reused without significant loss of the catalytic activity. The characterization results indicated that some Cu entered the Co3O4 lattices, leading to more high-valence metal ion sites (Co3+ and Cu2+) and surface oxygen species (O2-, O22-, and O-) as well as promoted redox ability, which all enhanced the catalytic activity. In addition, the catalysts were also efficient for the oxidation of other benzylic C-H containing aromatic hydrocarbons such as tetralin, indan, diphenylmethane and ethylbenzene.
- Luo, Jing,Xuan, Keng,Wang, Yanxia,Li, Feng,Wang, Feng,Pu, Yanfeng,Li, Lei,Zhao, Ning,Xiao, Fukui
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- Coordination frameworks assembled from CuII ions and H2-1,3-bdpb ligands: X-ray and magneto structural investigations, and catalytic activity in the aerobic oxidation of tetralin
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The syntheses and crystal structures of H2-1,3-bdpb·MeOH, [CuII2(1,3-bdpb)(OCH3)2] (CFA-5) and [CuICl(H2-1,3-bdpb)] (H2-1,3-bdpb = 1,3-bis(3,5-dimethyl-1H-pyrazol-4-yl)benzene) are described. The copper(ii) containing metal-organic framework (termed Coordination Framework Augsburg University-5, CFA-5) crystallizes in the trigonal crystal system, within the space group R3 (no. 148) and the unit cell parameters are as follows: a = 26.839(3), c = 15.8317(16) ?, V = 9876.2(19) ?3. CFA-5 features a two-fold interpenetrated 3-D microporous framework structure of cross-linked wheel-shaped {CuII(pz)(OMe)}12 fundamental building units, each containing twelve copper(ii) ions, μ2-bridging MeO- groups and pyrazolate (pz-) ligands. Replacing copper(ii) acetate by copper(ii) chloride in the synthesis leads to compound [CuICl(H2-1,3-bdpb)], which crystallizes in the orthorhombic crystal system, within the space group Pnma (no. 62) and the unit cell parameters are as follows: a = 6.1784(8), b = 6.1784(8), c = 6.1784(8) ?, V = 1583.8(4) ?3. In contrast to the former compound, CuCl(H2-1,3-bdpb) is a non-porous compound consisting of CuI-Cl zigzag chains expanding in the direction [100] and H2-1,3-bdpb ligands. CFA-5 is characterized by elemental and thermogravimetric analyses, variable temperature powder X-ray diffraction and IR-spectroscopy; and its porosity and magnetic properties are described in detail. CFA-5 shows a promising catalytic activity in the heterogeneously catalyzed aerobic oxidation of tetralin, which is compared with other catalytically active metal-organic frameworks.
- Grzywa, MacIej,Gessner, Christof,Bredenk?tter, Bj?rn,Denysenko, Dmytro,Van Leusen, Jan,K?gerler, Paul,Klemm, Elias,Volkmer, Dirk
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- Hydrocarbon oxidation catalyzed by a cheap nonheme imine-based iron(II) complex
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Nonheme iron complex 1 is easily obtained by one-pot assembly of cheap and commercially available starting materials. This complex effectively catalyzes the oxidation of a number of non-activated C-H bonds by H2O 2 with high turnover numbers and good selectivity. the Partner Organisations 2014.
- Olivo, Giorgio,Arancio, Giorgio,Mandolini, Luigi,Lanzalunga, Osvaldo,Di Stefano, Stefano
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- Meso-Substitution Activates Oxoiron(IV) Porphyrin π-Cation Radical Complex More Than Pyrrole-β-Substitution for Atom Transfer Reaction
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There have been two known categories of porphyrins: a meso-substituted porphyrin like meso-tetramesitylporphyrin (TMP) and a pyrrole-β-substituted porphyrin like native porphyrins and 2,7,12,17-tetramethyl-3,8,13,18-tetramesitylporphyrin (TMTMP). To reveal the chemical and biological function of native hemes, we compare the reactivity of the oxoiron(IV) porphyrin π-cation radical complex (Compound I) of TMP (TMP-I) with that of TMTMP (TMTMP-I) for epoxidation, hydrogen abstraction, hydroxylation, sulfoxidation, and demethylation reactions. Kinetic analysis of these reactions indicated that TMP-I is much more reactive than TMTMP-I when the substrate is not sterically bulky. However, as the substrate is sterically bulkier, the difference of the reactivity between TMP-I and TMTMP-I becomes smaller, and the reactivity of TMP-I is comparable to that of TMTMP-I for a sterically hindered substrate. Since the redox potential of TMP-I is almost the same as that of TMTMP-I, we conclude that TMP-I is intrinsically more reactive than TMTMP-I for these atom transfer reactions, but the steric effect of TMP-I is stronger than that of TMTMP-I. This is contrary to the previous result for the single electron transfer reaction: TMTMP-I is faster than TMP-I. DFT calculations indicate that the orbital energies of the Fe=O moiety for TMTMP-I are higher than those for TMP-I. The difference in steric effect between TMP-I and TMTMP-I is explained by the distance from the mesityl group to the oxo ligand of Compound I. Significance of the pyrrole-β-substituted structure of the hemes in native enzymes is also discussed on the basis of this study.
- Fukui, Nami,Ueno, Kanako,Hada, Masahiko,Fujii, Hiroshi
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- Ionic liquid templated preparation of carbon aerogels based on resorcinol-formaldehyde: Properties and catalytic performance
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A series of carbon aerogels were prepared with or without using ionic liquids as templates. By varying the structures and contents of ionic liquids, carbon aerogels with different pore size distributions could be obtained. The effect of the ionic liquids on the properties of the final carbon aerogels was explored and the catalytic performance of the carbon aerogels in the selective oxidation of tetralin was studied.
- Yang, Huimin,Cui, Xinjiang,Deng, Youquan,Shi, Feng
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p. 21852 - 21856,5
(2012)
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- Autoxidation of Tetralin in Water catalysed by Cobalt(II)-Pyridine Complexes bound to Polymer Colloids
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Cobalt(II)-pyridine complexes bound to 60 nm diameter latex copolymers of styrene, divinylbenzene, and either acrylic or methacrylic acid catalayse autoxidation of tetralin in water faster than cobalt(II)-pyridine complexes in aqueous solution or cobalt acetate in acetic acid.
- Chandran, Rama S.,Ford, Warren T.
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- Selective Decomposition of Tetralin Hydroperoxide Catalysed by Quaternary Ammonium Salts
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Tetralin hydroperoxide decomposes to 1-tetralone via a hydrogen bond complex with quaternary ammonium salt catalysts.
- Napadensky, Eduardo,Sasson, Yoel
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- Identification of Novel Unspecific Peroxygenase Chimeras and Unusual YfeX Axial Heme Ligand by a Versatile High-Throughput GC-MS Approach
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Catalyst discovery and development requires the screening of large reaction sets necessitating analytic methods with the potential for high-throughput screening. These techniques often suffer from substrate dependency or the requirement of expert knowledge. Chromatographic techniques (GC/LC) can overcome these limitations but are generally hampered by long analysis time or the need for special equipment. The herein developed multiple injections in a single experimental run (MISER) GC-MS technique allows a substrate independent 96-well microtiter plate analysis within 60 min. This method can be applied to any laboratory equipped with a standard GC-MS. With this concept novel, unspecific peroxygenase (UPO) chimeras, could be identified, consisting of subdomains from three different fungal UPO genes. The GC-technique was additionally applied to evaluate an YfeX library in an E. coli whole-cell system for the carbene-transfer reaction on indole, which revealed the thus far unknown axial heme ligand tryptophan.
- Knorrscheidt, Anja,Püllmann, Pascal,Schell, Eugen,Homann, Dominik,Freier, Erik,Weissenborn, Martin J.
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- Enhancing the Catalytic Performance of a CYP116B Monooxygenase by Transdomain Combination Mutagenesis
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The cytochrome P450 monooxygenase discovered in Labrenzia aggregata (P450LaMO) is a self-sufficient redox system with versatile oxygenation functions. However, its catalytic performance is severely hindered by a low reaction rate, poor electron coupling efficiency (CE) and fragile thermostability. Herein, a simple transdomain combination mutation strategy was proposed for engineering this multi-domain P450 enzyme with redox partners fused to the heme domain. After focused mutagenesis on the heme domain, a triple mutant H3 (N119C/V264A/V437G) was hit, that improved the turnover frequency (TOF) and CE of P450LaMO by about 7.8-fold and 3.0-fold, respectively. A redox domain-based mutant with higher cytochrome c reduction activity, MR1 (M612L/K774Y), mediated more efficient electron transfer, elevated the TOF by 4.9-fold, and the coupling efficiency by 4.2-fold. The beneficial effect was further enhanced by combining the mutation sites from different domains, resulting in a combinatorial mutant (N119C/V264A/V437G/M612L/N694D) with a 9.1-fold increase in coupling efficiency, 10-fold in TOF, as well as +3.8 °C in thermostability (T5010). Meanwhile, for series of tetrahydronaphthalene derivatives, this combinator showed higher hydroxylation activity. This work suggested that employing this combinatorial strategy targeting on both the redox and heme domains is efficient to improve holoenzyme activity, CE and stability of a CYP116B subfamily member from the low starting point.
- Li, Ren-Jie,Xu, Jian-He,Chen, Qi,Zhao, Jing,Li, Ai-Tao,Yu, Hui-Lei
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- Biphasic autoxidation of tetralin catalyzed by surface-active transition metal complexes
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Biphasic autoxidation of tetralin has been carried out using surface-active tetramethylethylenediamine complexes of manganese, chromium, and nickel as catalysts, tetralin as the substrate and organic phase, and dodecyl sodium sulfate as emulsifier. Advantages of the biphasic reaction over the homogeneous and heterogeneous counterparts include avoidance of the use of a troublesome solvent, ease of catalyst recovery and substrate recycle, and attainment of high reactivity, selectivity, and reproducibility under mild reaction conditions (T a?? 60 ?°C, P a?? 1 atm). The main reaction products are ?±-tetralone and ?±-tetralol. The selectivity for the former decreases from 95% with the chromium complex to 90% with the nickel complex and 60% with the manganese complex, and the activity varies in a reverse order. The biphasic reaction stops at a bulk tetralin conversion of 35% due to the buildup of inhibitive, higher oxidation products. Similar product inhibition has been reported in one-liquid-phase systems. The biphasic scheme, however, permits a more convenient recovery and recycle of the catalyst and unreacted substrate. The reaction order with respect to oxygen decreases from 1.0 to 0 above an oxygen pressure of 0.15 atm. The reaction order with respect to catalyst decreases from 2.0 or 1.4 to 1.0 and then 0 with increasing metal concentration. Manganese switches role from catalyst to inhibitor above a threshold metal concentration, as indicated by a lengthening of the induction period of the reaction. A generalized reaction mechanism is proposed which yields model results in good agreement with the experimental findings.
- Ahn, Wha Seung,Zhong, Yaping,Abrams, Cameron F.,Lim,Brown, Phillip A.
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- Metal organic frameworks (MOFs) as catalysts: A combination of Cu2+ and Co2+ MOFs as an efficient catalyst for tetralin oxidation
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Two metal-organic frameworks, [Cu(2-pymo)2] and [Co(PhIM)2] (2-pymo = 2-hydroxypyrimidinolate; PhIM = phenylimidazolate), containing respectively Cu2+ and Co2+ ions and anionic diazaheterocyclic ligands (pyrimidinolate and phenylimidazolate) as organic linkers, have been successfully used for the aerobic oxidation of tetralin, yielding α-tetralone (T{double bond, long}O) as the main product. Both materials are stable and recyclable under the reaction conditions. Kinetic studies revealed significant differences between the two MOFs, as a consequence of the different catalytic behavior of their central metal ions. [Cu(2-pymo)2] is highly active for the activation of tetralin to produce tetralinhydroperoxide (T{single bond}OOH), and less efficient in reacting the peroxide. Meanwhile, the use of the cobalt catalyst involves a long induction period for the reaction. However, once T{single bond}OOH is formed, Co2+ rapidly and efficiently transforms this into T{double bond, long}O, with high tetralone-to-tetralol ratio (T{double bond, long}O/T{single bond}OH of ca. 7). The combination of both materials has revealed as a convenient strategy for preparing a highly efficient, selective and reusable catalyst for the liquid phase aerobic oxidation of tetralin.
- Llabres i Xamena,Casanova,Galiasso Tailleur,Garcia,Corma
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- Synthesis of a sulfonato-salen-nickel(ii) complex immobilized in LDH for tetralin oxidation
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A novel sulfonato-salen-nickel(ii) complex has been immobilized on a Zn(ii)-Al(iii) layered double hydroxide (LDH) host. XRD, FT-IR, TGA and UV-vis spectroscopy, as well as chemical analysis, confirmed the successful incorporation of the nickel-salen complex within the LDH structure. BET surface area measurements, SEM and TEM were also used to characterize the heterogenized catalyst. The sulfonato-salen-nickel(ii) complex-immobilized material, LDH-[nickel-salen], was found to be effective in the oxidation of tetralin, where a combination of trimethylacetaldehyde and dioxygen at atmospheric pressure was employed as the oxidant. At 72.3% conversion, tetralin was converted to 1-tetralone with 72.2% selectivity at 70 °C after 7 h. Tetralin oxidation using tert-butyl hydroperoxide afforded a lower conversion and selectivity of 1-tetralone than with trimethylacetaldehyde and dioxygen as the oxidant. The effect of various reaction parameters on catalytic performance was also investigated. A hot filtration experiment coupled with a blank test revealed that oxidation proceeded mostly on nickel-salen sites in LDH-[nickel-salen]. A reaction mechanism is proposed based on the experimental results.
- Bhattacharjee, Samiran,Jeong, Kwang-Eun,Jeong, Soon-Yong,Ahn, Wha-Seung
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- Design, synthesis, characterization, and catalytic properties of a large-pore metal-organic framework possessing single-site vanadyl(monocatecholate) moieties
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Through a combination of protecting groups, postsynthesis deprotection, and postsynthesis metallation, a homogeneously inaccessible, single-site vanadyl(monocatecholate) moiety can be incorporated into the dipyridyl struts of a Zn-based, pillared paddlewheel MOF. The resulting MOF, which has large pores, exhibits catalytic activity in the benzylic oxidation of tetralin in the presence of tert-butylhydroperoxide.
- Nguyen, Huong Giang T.,Weston, Mitchell H.,Sarjeant, Amy A.,Gardner, Daniel M.,An, Zhi,Carmieli, Raanan,Wasielewski, Michael R.,Farha, Omar K.,Hupp, Joseph T.,Nguyen, Sonbinh T.
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- Platinum thiolate complexes supported by PBP and POCOP pincer ligands as efficient catalysts for the hydrosilylation of carbonyl compounds
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Diphosphino-boryl-based PBP pincer platinum thiolate complexes, [Pt(SR){B(NCH2PtBu2)2-1,2-C6H4}] (R = H, 1a; Ph, 1b), and benzene-based bisphosphinite POCOP pincer platinum thiolate complexes, [Pt(SR)(tBu2PO)2-1,3-C6H3] (R = H, 2a; Ph, 2b), were prepared
- Chang, Jiarui,Chen, Xuenian,Xue, Man-Man,Zhang, Jie
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supporting information
p. 2304 - 2312
(2022/02/21)
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- Expanding Zirconocene Hydride Catalysis: In Situ Generation and Turnover of ZrH Catalysts Enabling Catalytic Carbonyl Reductions
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Despite the wide use and popularity of metal hydride catalysis, methods utilizing zirconium hydride catalysts remain underexplored. Here, we report the development of a mild method for the in situ preparation and use of zirconium hydride catalysts. This r
- Kehner, Rebecca A.,Hewitt, Matthew Christian,Bayeh-Romero, Liela
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p. 1758 - 1763
(2022/02/07)
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- Pincerlike molybdenum complex and preparation method thereof, catalytic composition and application thereof, and alcohol preparation method
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The invention discloses a clamp-type molybdenum complex, a preparation method, a corresponding catalyst composition and application. The method comprises the steps: obtaining 9 molybdenum complexes with different structures through coordination reaction of 2-(substituent ethyl)-(5, 6, 7, 8-tetrahydroquinolyl) amine and a corresponding carbonyl molybdenum metal precursor; and catalyzing a ketone compound transfer hydrogenation reaction through a molybdenum complex to generate 40 alcohol compounds. The preparation method of the molybdenum complex is simple, high in yield and good in stability. For a transfer hydrogenation reaction of ketone, the molybdenum-based catalytic system has high catalytic activity and small molybdenum loading capacity, is used for production of aromatic and aliphatic alcohols, and has the advantages of simple method, small environmental pollution and high yield.
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Paragraph 0125-0132
(2021/08/11)
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- Fe-Catalyzed Anaerobic Mukaiyama-Type Hydration of Alkenes using Nitroarenes
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Hydration of alkenes using first row transition metals (Fe, Co, Mn) under oxygen atmosphere (Mukaiyama-type hydration) is highly practical for alkene functionalization in complex synthesis. Different hydration protocols have been developed, however, control of the stereoselectivity remains a challenge. Herein, highly diastereoselective Fe-catalyzed anaerobic Markovnikov-selective hydration of alkenes using nitroarenes as oxygenation reagents is reported. The nitro moiety is not well explored in radical chemistry and nitroarenes are known to suppress free radical processes. Our findings show the potential of cheap nitroarenes as oxygen donors in radical transformations. Secondary and tertiary alcohols were prepared with excellent Markovnikov-selectivity. The method features large functional group tolerance and is also applicable for late-stage chemical functionalization. The anaerobic protocol outperforms existing hydration methodology in terms of reaction efficiency and selectivity.
- Bhunia, Anup,Bergander, Klaus,Daniliuc, Constantin Gabriel,Studer, Armido
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supporting information
p. 8313 - 8320
(2021/03/08)
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- Oxidation Under Reductive Conditions: From Benzylic Ethers to Acetals with Perfect Atom-Economy by Titanocene(III) Catalysis
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Described here is a titanocene-catalyzed reaction for the synthesis of acetals and hemiaminals from benzylic ethers and benzylic amines, respectively, with pendant epoxides. The reaction proceeds by catalysis in single-electron steps. The oxidative addition comprises an epoxide opening. An H-atom transfer, to generate a benzylic radical, serves as a radical translocation step, and an organometallic oxygen rebound as a reductive elimination. The reaction mechanism was studied by high-level dispersion corrected hybrid functional DFT with implicit solvation. The low-energy conformational space was searched by the efficient CREST program. The stereoselectivity was deduced from the lowest lying benzylic radical structures and their conformations are controlled by hyperconjugative interactions and steric interactions between the titanocene catalyst and the aryl groups of the substrate. An interesting mechanistic aspect is that the oxidation of the benzylic center occurs under reducing conditions.
- Funk, Pierre,Richrath, Ruben B.,Bohle, Fabian,Grimme, Stefan,Gans?uer, Andreas
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supporting information
p. 5482 - 5488
(2021/02/03)
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- Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
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A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
- Oestreich, Martin,Seliger, Jan
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supporting information
p. 247 - 251
(2020/10/29)
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- Ruthenium-p-cymene Complex Side-Wall Covalently Bonded to Carbon Nanotubes as Efficient Hybrid Transfer Hydrogenation Catalyst
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A half-sandwich ruthenium-p-cymene organometallic complex has been immobilized at Single Walled Carbon Nanotubes (SWNT) sidewalls through a stepwise covalent chemistry protocol. The introduction of amino groups by means of diazonium-chemistry protocols leads the grafting at the outer walls of the nanotubes. This hybrid material is active in the transfer hydrogenation of ketones to yield alcohols, using as hydrogen source 2-propanol. SWNT?NH2?Ru presents a broad scope, performing the reaction under aerobic conditions and can be recycled over 9 consecutive reaction runs without losing activity or leaching ruthenium out. Comparison of the activity with related homogeneous catalysts reveals an improved performance due to the covalent bond between the metal and the material, achieving turnover frequencies as high as 192774 h?1.
- Blanco, Matías,Cembellín, Sara,Agnoli, Stefano,Alemán, José
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p. 5156 - 5165
(2021/11/05)
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- Cationic nickel(II) pyridinophane complexes: Synthesis, structures and catalytic activities for C-H oxidation
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A series of nickel(II) pyridinophane complexes were synthesized and characterized by X-ray crystallographic analysis. Their IR spectra supported the existence of mononuclear nickel(II) complexes in solution. Furthermore, we conducted catalytic CH oxidation of cyclooctane with nickel(II) pyridinophanes as the catalysts. The activity of nickel(II) pyridinophanes was affected by steric hindrance around the nitrogen atoms.
- Nishimura, Tsubasa,Ando, Yuki,Shinokubo, Hiroshi,Miyake, Yoshihiro
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supporting information
p. 1049 - 1052
(2021/05/19)
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- POLITAG-Pd(0) catalyzed continuous flow hydrogenation of lignin-derived phenolic compounds using sodium formate as a safe H-source
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Phenols are aromatic biobased compounds and as they are accessible from lignin depolymerization, they can be a useful platform chemicals to produce value-added products. Herein we report our recent investigations on the definition of an approach to the efficient continuous flow selective hydrogenation of phenols in water. Our protocol is based on the use of sodium formate as a clean and safe hydrogen source in combination with our newly defined heterogeneous POLITAG-Pd(0) catalytic system. POLITAG is a polymeric heterogeneous support decorated with pincer-type ionic ligands proven to be highly efficient for the stabilization of Pd(0) nanoparticles. The results obtained are remarkable in comparison with other protocols that employ sodium formate as H-source. Indeed, our investigation has been extended to a variety of differently substituted phenolic compounds that have been hydrogenated with excellent to good selectivity in continuous flow conditions. Durability of the catalyst has been also tested with a representative continuous processing of over 100 mmol that showed no loss in efficiency and minimal metal leaching.
- Campana, Filippo,Ferlin, Francesco,Silvetti, Matteo,Trombettoni, Valeria,Vaccaro, Luigi,Valentini, Federica
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- Sodium Aminodiboranate, a New Reagent for Chemoselective Reduction of Aldehydes and Ketones to Alcohols
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Sodium aminodiboranate (NaNH 2(BH 3) 2, NaADBH) is a new member of the old borane family, which exhibits superior performance in chemoselective reduction. Experimental results show that NaADBH can rapidly reduce aldehydes and ketones to the corresponding alcohols in high efficiency and selectivity under mild conditions. There are little steric and electronic effects on this reduction.
- Wang, Jin,Guo, Yu,Li, Shouhu,Chen, Xuenian
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supporting information
p. 1104 - 1108
(2021/05/25)
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- Efficient Solvent-Free Hydrosilylation of Aldehydes and Ketones Catalyzed by Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH
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An efficient solvent-free catalyst system for hydrosilylation of aldehydes and ketones was developed based on iron pre-catalyst Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH. The reactions were tolerant of many functional groups and the corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the reaction products. The reaction is likely catalyzed by an in situ generated pincer ligated iron hydride complex. Graphic Abstract: [Figure not available: see fulltext.]
- Fang, Fei,Chang, Jiarui,Zhang, Jie,Chen, Xuenian
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p. 3509 - 3515
(2021/03/16)
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- Hydrosilylation of Carbonyl Compounds Catalyzed by a Nickel Complex Bearing a PBP Ligand
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The efficient catalytic hydrosilylation of ketones and aldehydes has been investigated using a nickel pincer hydride complex supported by a diphosphino-boryl ligand (PBP). It was found that the presence of the boryl group within the skeleton of the ligand has a beneficial effect on the catalytic activities observed for ketones compared to related pincer systems. The analysis of the reaction mechanism allows for the synthesis and characterization of a nickel alkoxide derivative by insertion of the carbonyl moiety into the Ni?H bond. Combined experimental and theoretical analysis (DFT) support a reaction mechanism that involves the initial formation of an alkoxide complex followed by reaction with the silane to release the corresponding silyl ether and regenerate the catalyst.
- Antonio Fernández, José,Manuel García, Juan,Ríos, Pablo,Rodríguez, Amor
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supporting information
p. 2993 - 2998
(2021/07/10)
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- N-Heterocyclic Carbene (NHC)-Stabilized Ru0 Nanoparticles: In Situ Generation of an Efficient Transfer Hydrogenation Catalyst
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Tethered and untethered ruthenium half-sandwich complexes were synthesized and characterized spectroscopically. X-ray crystallographic analysis of three untethered and two tethered Ru N-heterocyclic carbene (NHC) complexes were also carried out. These RuNHC complexes catalyze transfer hydrogenation of aromatic ketones in 2-propanol under reflux, optimally in the presence of (25 mol %) KOH. Under these conditions, the formation of 2–3 nm-sized Ru0 nanoparticles was detected by TEM measurements. A solid-state NMR investigation of the nanoparticles suggested that the NHC ligands were bound to the surface of the Ru nanoparticles (NPs). This base-promoted route to NHC-stabilized ruthenium nanoparticles directly from arene-tethered ruthenium–NHC complexes and from untethered ruthenium–NHC complexes is more convenient than previously known routes to NHC-stabilized Ru nanocatalysts. Similar catalytically active RuNPs were also generated from the reaction of a mixture of [RuCl2(p-cymene)]2 and the NHC precursor with KOH in isopropanol under reflux. The transfer hydrogenation catalyzed by these NHC-stabilized RuNPs possess a high turnover number. The catalytic efficiency was significantly reduced if nanoparticles were exposed to air or allowed to aggregate and precipitate by cooling the reaction mixtures during the reaction.
- Kathuria, Lakshay,Din Reshi, Noor U.,Samuelson, Ashoka G.
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supporting information
p. 7622 - 7630
(2020/05/29)
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- Efficient catalytic transfer hydrogenation reactions of carbonyl compounds by Ni(II)-diphosphine complexes
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The catalytic transfer hydrogenation reactions of a series of aromatic and aliphatic carbonyl compounds were investigated using divalent Ni(II)-diphosphine complexes, [L2NiCl2] (where L2 = 1,1-bis(diphenylphosphino)methane (dppm), 1,2-bis(diphenylphosphino)ethane (dppe), 1,3-bis(diphenylphosphino)propane (dppp), 1,1-bis(diphenylphosphino)ferrocene (dppf), and N-butyl-N-(diphenylphosphino)-1,1-diphenylphosphinamine (dppba)). This is a single-step reaction in the presence of potassium hydroxide and isopropyl alcohol to afford the corresponding alcohols. This protocol tolerates other sensitive functional groups like olefinic double bonds and also achieves high chemoselectivity. All the reactions were monitored by GC and GC–MS. The plausible mechanism is also discussed. The method reported in the present article is simple, cost-effective, and provides excellent conversions. Nickel-diphosphine complexes appear as a potential alternative to expensive transition metal complexes.
- Venkatesh, Sadhana,Panicker, Rakesh R.,Lenin Kumar, Verdhi,Pavankumar,Viswanath, Nukala,Singh, Shangrila,Desikan, Rajagopal,Sivaramakrishna, Akella
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p. 2963 - 2977
(2020/11/03)
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- Access to both enantiomers of substituted 2-tetralol analogs by a highly enantioselective reductase
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Both (S) and (R) forms of enantiomerically pure 2-tetralols, and their substituted analogs, are fundamental pharmaceutical intermediates. Here, we utilized the wild type and an engineered form of a highly enantioselective acetophenone reductase from Geotrichum candidum NBRC 4597 (GcAPRD) to produce (S)- and (R)-2-tetralols, and their substituted analogs. All mutations targeted residue Trp288, which has been shown to restrict substrate binding, but not play a direct role in catalysis. The wild type produced (S)-alcohols with excellent enantioselectivity, while the engineered forms produced either (S)- or (R)- alcohols, depending on the substituent on the aromatic ring of the substrate, indicating that enantioselectivity can be rationally controlled. As a result, we were able to produce 6-hydroxy-2-tetralol, a potential antifungal drug intermediate, with 98% ee (S) and 81% ee (R) by wild type and Trp288Ser GcAPRD, respectively. To our knowledge, this is the first report of generating chiral 6-hydroxy-2-tetralol by rational enzyme design.
- Koesoema, Afifa Ayu,Matsuda, Tomoko,Standley, Daron M.,T. sriwong, Kotchakorn,Tamura, Mayumi
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supporting information
(2020/02/11)
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- Efficient Transfer Hydrogenation of Ketones using Methanol as Liquid Organic Hydrogen Carrier
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Herein, we demonstrate an efficient protocol for transfer hydrogenation of ketones using methanol as practical and useful liquid organic hydrogen carrier (LOHC) under Ir(III) catalysis. Various ketones, including electron-rich/electron-poor aromatic ketones, heteroaromatic and aliphatic ketones, have been efficiently reduced into their corresponding alcohols. Chemoselective reduction of ketones was established in the presence of various other reducible functional groups under mild conditions.
- Garg, Nidhi,Paira, Soumen,Sundararaju, Basker
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p. 3472 - 3476
(2020/05/29)
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- Enantioselective Hydroxylation of Benzylic C(sp3)-H Bonds by an Artificial Iron Hydroxylase Based on the Biotin-Streptavidin Technology
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The selective hydroxylation of C-H bonds is of great interest to the synthetic community. Both homogeneous catalysts and enzymes offer complementary means to tackle this challenge. Herein, we show that biotinylated Fe(TAML)-complexes (TAML = Tetra Amido Macrocyclic Ligand) can be used as cofactors for incorporation into streptavidin to assemble artificial hydroxylases. Chemo-genetic optimization of both cofactor and streptavidin allowed optimizing the performance of the hydroxylase. Using H2O2 as oxidant, up to ~300 turnovers for the oxidation of benzylic C-H bonds were obtained. Upgrading the ee was achieved by kinetic resolution of the resulting benzylic alcohol to afford up to >98% ee for (R)-tetralol. X-ray analysis of artificial hydroxylases highlights critical details of the second coordination sphere around the Fe(TAML) cofactor.
- Barnet, Maxime,Peterson, Ryan L.,Rebelein, Johannes G.,Rumo, Corentin,Serrano-Plana, Joan,Ward, Thomas R.
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supporting information
p. 10617 - 10623
(2020/07/04)
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- Iron(III) 5,15-diazaporphyrin catalysts for the direct oxidation of C(sp3)-H bonds
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5,15-Diazaporphyrins are porphyrin analogues with imine-type sp2-hybridized nitrogen atoms at the meso-positions. Even though these compounds are more electron-deficient than regular porphyrins, the use of iron diazaporphyrins as catalysts has not been reported. Herein, we disclose the synthesis, structure, and electronic properties of iron(III) 5,15-diazaporphyrins. We evaluate their structures and electronic natures by X-ray analysis and electrochemical analyses. We also demonstrate that chloroiron(III) 5,15-diazaporphyrins exhibit high catalytic activity in the direct oxidation of alkanes due to their intrinsic electron-deficient nature. On the basis of stoichiometric reactions of iron(III) diazaporphyrin with iodosylbenzene as an oxidant, it was possible to demonstrate the existence of an iodosylbenzene-iron diazaporphyrin adduct reaction intermediate that serves as a reservoir to generate oxo-iron species.
- Ikeue, Takahisa,Miyake, Yoshihiro,Nishimura, Tsubasa,Shinokubo, Hiroshi,Shoji, Osami
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supporting information
p. 15751 - 15756
(2020/11/20)
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- Highly selective electrocatalytic oxidation of benzyl C-H using water as safe and sustainable oxygen source
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The selective oxidation of C-H bond is critical for feedstock manufacturing in chemical industry. Current strategies typically involve the use of oxygen or peroxide as the oxidation reagent under high temperature, which sets severe challenges in production sustainability and industrial safety. Herein, we demonstrate an environmental-friendly and safe electrocatalytic strategy for the selective oxidation of benzyl group to ketones at ambient conditions, while using water as the sole oxygen source. Water addition reduces the onset potential of anodic C-H oxidation, and produces 1-tetralone with satisfying conversion and excellent ketone to alcohol ratio. Layered MnO2 catalysts (with rich oxygen vacancies) further adjust the water affinity and facilitate the oxidation, leading to a significantly improved faradaic efficiency. This journal is
- Ding, Mengning,Li, Xiaoshan,Sun, Yuxia,Xie, Jin,Xu, Wentao,Yang, Miao
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supporting information
p. 7543 - 7551
(2020/11/18)
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- Green Organic Solvent-Free Oxidation of Alkylarenes with tert-Butyl Hydroperoxide Catalyzed by Water-Soluble Copper Complex
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Different benzylic compounds were efficiently oxidized to the corresponding ketones with aqueous 70% tert-butyl hydroperoxide (TBHP) and the catalytic system composed of CuCl2.2H2O and 2,2'-biquinoline-4,4'-dicarboxylic acid dipotassium salt (BQC). The catalytic system CuCl2/BQC/TBHP allows obtaining high yields at room temperature under organic solvent-free conditions. The interest of this system lies in its cost effectiveness and its benign nature towards the environment. Benzylic tertbutylperoxy ethers and benzylic alcohols were observed and suggested as the reaction intermediates. Analysis of organic products by atomic absorption did not show any contamination with copper metal. In terms of efficiency, CuCl2/BQC system is comparable or superior to the most of the catalytic systems described in the literature and which are based on toxic organic solvent.
- Ajjou, Abdelaziz Nait,Rahman, Ateeq
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p. 165 - 174
(2020/04/15)
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- Homoleptic Zinc-Catalyzed Hydroboration of Aldehydes and Ketones in the Presence of HBpin
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Here, we report the reaction between N-phenyl-o-phenylenediamine and pyrrole-2-carboxaldehyde to afford the N-phenyl-o-phenyl-enediiminopyrrole ligand {L-H2} in quantitative yield. A one-pot reaction between {L-H2} and diethylzinc (ZnEt2) in a 2:1 ratio afforded the homoleptic zinc metal complex [{L-H}2Zn] (1). The solid-state structures of ligand {L-H2} and zinc complex 1 were confirmed using X-ray crystallography. Further, complex 1 was used for chemoselective hydroboration of aldehydes and ketones in the presence of pinacolborane (HBpin) at ambient temperature to produce the corresponding boronate esters in high yield.
- Kumar, Gobbilla Sai,Harinath, Adimulam,Narvariya, Rajrani,Panda, Tarun K.
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supporting information
p. 467 - 474
(2020/02/04)
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- Palladium-Catalyzed Selective Reduction of Carbonyl Compounds
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Two new examples of structurally characterized β-diketiminate analogues i.e., conjugated bis-guanidinate (CBG) supported palladium(II) complexes, [LPdX]2; [L= {(ArHN)(ArN)–C=N–C=(NAr)(NHAr)}; Ar = 2,6-Et2-C6H3], X = Cl (1), Br (2) have been reported. The synthesis of complexes 1–2 was achieved by two methods. Method A involves deprotonation of LH by nBuLi followed by the treatment of LLi (insitu formed) with PdCl2 in THF, which afforded compound 1 in good yield (75 %). In Method B, the reaction between free LH and PdX2 (X = Cl or Br) in THF allowed the formation of complexes 1 (Yield 73 %) and 2 (Yield 52 %), respectively. Moreover, these complexes were characterized thoroughly by several spectroscopic techniques (1H, 13C NMR, UV/Vis, FT-IR, and HRMS), including single-crystal X-ray structural and elemental analyses. In addition, we tested the catalytic activity of these complexes 1–2 for the hydroboration of carbonyl compounds with pinacolborane (HBpin). We observed that compound 1 exhibits superior catalytic activity when compared to 2. Compound 1 efficiently catalyzes various aldehydes and ketones under solvent-free conditions. Furthermore, both inter- and intramolecular chemoselectivity hydroboration of aldehydes over other functionalities have been established.
- Sarkar, Nabin,Mahato, Mamata,Nembenna, Sharanappa
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p. 2295 - 2301
(2020/05/18)
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- Erratum: Redox-Noninnocent Ligand-Supported Vanadium Catalysts for the Chemoselective Reduction of C=X (X = O, N) Functionalities (Journal of the American Chemical Society (2019) 141:38 (15230-15239) DOI: 10.1021/jacs.9b07062)
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Pages 15232, 15233, and 15236. In the original paper, the doublet wave functions for 21 and 21a/21b were incorrectly (Figure Presented). reported as spin-contaminated in sections 2.3 and 2.8 (Figure 3 and Scheme 9, respectively.) This comes from the incorrectly reported expected eigenvalue of 0.75 for the spin-squared operator ??2? for the antiferromagnetically coupled doublet |↓?L|↑↑?V state (originally given in the Supporting Information). The correct expected eigenvalue for the |↓?L|↑↑?V state should be 1.75. The wave functions for 21 and 21a/21b (eigenvalues 1.79 and 1.77/1.66, respectively) are therefore not spincontaminated. The corrected Figure 3 and Scheme 9 are presented below. A corrected Supporting Information file is also provided. The corrections do not affect any of the conclusions of the Article, but slightly decrease the gap between the quartet and doublet spin surfaces. Scheme 3 has been also corrected to reflect the fact that (CH3)3SiCH2 ? radicals can only react based on spin conservation.
- Zhang, Guoqi,Wu, Jing,Zheng, Shengping,Neary, Michelle C.,Mao, Jincheng,Flores, Marco,Trovitch, Ryan J.,Dub, Pavel A.
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supporting information
p. 16507 - 16509
(2020/10/14)
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- A General Method for Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids
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A general and practical method for decarboxylative hydroxylation of carboxylic acids was developed through visible light-induced photocatalysis using molecular oxygen as the green oxidant. The addition of NaBH4 to in situ reduce the unstable peroxyl radical intermediate much broadened the substrate scope. Different sp3 carbon-bearing carboxylic acids were successfully employed as substrates, including phenylacetic acid-type substrates, as well as aliphatic carboxylic acids. This transformation worked smoothly on primary, secondary, and tertiary carboxylic acids.
- Khan, Shah Nawaz,Zaman, Muhammad Kashif,Li, Ruining,Sun, Zhankui
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p. 5019 - 5026
(2020/05/01)
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- Capturing the Monomeric (L)CuH in NHC-Capped Cyclodextrin: Cavity-Controlled Chemoselective Hydrosilylation of α,β-Unsaturated Ketones
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The encapsulation of copper inside a cyclodextrin capped with an N-heterocyclic carbene (ICyD) allowed both to catch the elusive monomeric (L)CuH and a cavity-controlled chemoselective copper-catalyzed hydrosilylation of α,β-unsaturated ketones. Remarkably, (α-ICyD)CuCl promoted the 1,2-addition exclusively, while (β-ICyD)CuCl produced the fully reduced product. The chemoselectivity is controlled by the size of the cavity and weak interactions between the substrate and internal C?H bonds of the cyclodextrin.
- Bistri-Aslanoff, Olivia,Derat, Etienne,Leloux, Sébastien,Leyssens, Tom,Ménand, Micka?l,Meijide Suárez, Jorge,Riant, Olivier,Roland, Sylvain,Sollogoub, Matthieu,Xu, Guangcan,Zhang, Pinglu,Zhang, Yongmin
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supporting information
p. 7591 - 7597
(2020/03/23)
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- Hydrosilylation of Aldehydes and Ketones Catalysed by Bis(phosphinite) Pincer Platinum Hydride Complexes
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Bis(phosphinite) pincer platinum hydride complexes, [2,6-(R2PO)2C6H3]PtH (R=tBu, iPr), were synthesized, characterized and applied to the hydrosilylation of aldehydes and ketones. NMR study and single crystal X-ray diffraction analysis indicated that the hydrides in these two platinum complexes are comparatively less hydridic: down-field 1H NMR resonances (0.71 and 0.98 ppm) and weak Pt?H interactions were observed. Both the platinum complexes were found to be good catalysts for the hydrosilylation of aldehydes and ketones with phenylsilane. The corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the resultant hydrosilylation products and turnover frequencies (TOFs) up to 3200 h?1 were achieved at 60 °C in toluene, which are much higher than those of the hydrosilylation catalysed by the corresponding nickel pincer hydride complexes. A possible mechanism for the present hydrosilylation process was discussed. (Figure presented.).
- Chang, Jiarui,Fang, Fei,Zhang, Jie,Chen, Xuenian
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p. 2709 - 2715
(2020/06/02)
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- Benzimidazole fragment containing Mn-complex catalyzed hydrosilylation of ketones and nitriles
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The synthesis of a new bidentate (NN)–Mn(I) complex is reported and its catalytic activity towards the reduction of ketones and nitriles is studied. On comparing the reactivity of various other Mn(I) complexes supported by benzimidazole ligand, it was observed that the Mn(I) complexes bearing 6-methylpyridine and benzimidazole fragments exhibited the highest catalytic activity towards monohydrosilylation of ketones and dihydrosilylation of nitriles. Using this protocol, a wide range of ketones were selectively reduced to the corresponding silyl ethers. In case of unsaturated ketones, the chemoselective reduction of carbonyl group over olefinic bonds was observed. Additionally, selective dihydrosilylation of several nitriles were also achieved using this complex. Mechanistic investigations with radical scavengers suggested the involvement of radical species during the catalytic reaction. Stoichiometric reaction of the Mn(I) complex with phenylsilane revealed the formation of a new Mn(I) complex.
- Ganguli, Kasturi,Mandal, Adarsha,Sarkar, Bidisha,Kundu, Sabuj
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supporting information
(2020/08/13)
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- A Conformationally Restricted Aza-BODIPY Platform for Stimulus-Responsive Probes with Enhanced Photoacoustic Properties
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Photoacoustic (PA) dyes, which absorb near-infrared (NIR) light to generate an ultrasonic signal, can be detected at centimeter depths in tissues with significantly higher resolution than dyes imaged with fluorescence-based methods. As such, PA agents show great promise as research tools for the study of live-animal disease models. However, the development of activatable PA probes has been hampered by the relative scarcity of appropriate PA-active molecular platforms with properties that can be manipulated in a rational manner. Herein we synthesized and evaluated six modifications to the aza-BODIPY dye platform with respect to their absorbance, fluorescence, and PA properties. We identified a promising conformationally restricted aza-BODIPY (CRaB) scaffold that prioritizes three criteria necessary for the design of stimulus-responsive dyes with optimal ratiometric PA response: absorbance at NIR wavelengths, strong PA intensity, and large Δλ upon interaction with the desired stimulus. Using this scaffold, we synthesized three chemically diverse stimulus-responsive PA probes and demonstrated between 2- and 8-fold improvements in theoretical ratiometric response in vitro. This suggests that improvements in PA parameters are generalizable. Finally, we validated the in vitro turnover of each CRaB PA probe and demonstrated the in vivo potential of the CRaB scaffold by direct comparison to an established hypoxia-responsive probe for the detection of tumor hypoxia.
- Zhou, Effie Y.,Knox, Hailey J.,Liu, Chang,Zhao, Weili,Chan, Jefferson
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supporting information
p. 17601 - 17609
(2019/11/11)
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- Synthetic Entry to Polyfunctionalized Molecules through the [3+2]-Cycloaddition of Thiocarbonyl Ylides
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Here we present a comprehensive study on the [3+2]-cycloaddition of thiocarbonyl ylides with a wide variety of alkenes and alkynes. The obtained dihydro- and tetrahydrothiophene products serve as exceptionally versatile intermediates providing access to thiophenes, dienes, dendralenes, and vic-quarternary carbon centers. The use of high-pressure conditions enables thermally unstable, sterically encumbered or moderately reactive substrates to undergo the cycloaddition under mild conditions, thereby increasing the yield by up to 58percent. In addition, we showcase its utility by the formal syntheses of the pharmaceuticals NGB 4420 and tenilapine.
- Habiger, Christoph,Haut, Franz-Lucas,Korber, Johannes Nepomuk,Müller, Thomas,Magauer, Thomas,Mayer, Peter,Speck, Klaus,Wurst, Klaus
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supporting information
(2019/09/06)
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- Dearomatization and Functionalization of Terpyridine Ligands Leading to Unprecedented Zwitterionic Meisenheimer Aluminum Complexes and Their Use in Catalytic Hydroboration
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This paper reports the first example of dearomatization of ubiquitous terpyridine (tpy) ligands via 2′/6′-, 3′/5′-, or 4′-selective alkylation of the central pyridine ring. The reaction is mediated by the most abundant metal in the Earth's crust, aluminum (Al), and depending on the conditions employed, exhibits ionic or radical character as suggested by experimental and computational analysis. In the latter case, intermediate formation of an AlIII complex supported by π-radical monoanionic ligand (tpy?)1- is apparent. The 3′/5′-alkylation leads to unprecedented zwitterionic Meisenheimer AlIII complexes, which were identified as efficient precatalysts for the selective hydroboration of C=O and C-C functionalities. Turnover numbers (TONs) up to ~1000 place the corresponding complexes in the category of the most efficient Al catalysts reported to date for the title reaction. The acquired data suggest that aluminum monohydrides, or more likely dihydrides, could be relevant catalytic species. Alternatively, one can also imagine a mechanistic scenario in which the dearomatized "chemically noninnocent" ligand acts as hydride donor, and a detailed investigation of this is warranted in the future.
- Zhang, Guoqi,Wu, Jing,Zeng, Haisu,Neary, Michelle C.,Devany, Matthew,Zheng, Shengping,Dub, Pavel A.
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p. 874 - 884
(2019/01/14)
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- Design of Manganese Phenol Pi-complexes as Shvo-type Catalysts for Transfer Hydrogenation of Ketones
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Catalytic hydrogenation is one of the most important reactions both in academic research and industry. We explored ability of the manganese pi-complexes to act as Shvo-type catalysts for transfer hydrogenation of ketones. DFT calculations suggested that the transfer of hydrogen atoms from the hypothetical intermediate [(C6Me3H2OH)Mn(CO)2H] to acetone has low activation barrier of 10.9 kcal mol?1. Experimentally a number of ketones with various functional groups (OMe, NH2, Cl, CF3, pyridyl) were successfully reduced in isopropanol at 90 °C in the presence of the complex [(C6Me3H2OH)Mn(CO)3]BF4 (1 mol %) and tBuOK (75 mol %). However, further investigation revealed that the reduction was mainly promoted by base rather than the manganese complex.
- Shvydkiy, Nikita V.,Vyhivskyi, Oleksandr,Nelyubina, Yulia V.,Perekalin, Dmitry S.
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p. 1602 - 1605
(2019/03/07)
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- Transfer hydrogenation of ketones catalyzed by 2,6‐bis(triazinyl)pyridine ruthenium complexes: The influence of alkyl arms
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The transfer hydrogenation of ketones catalyzed by transition metal complexes has attracted much attention. A series of ruthenium(II) complexes bearing 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine ligands (R-BTPs) were synthesized and characterized by NMR analysis and X-ray diffraction. These ruthenium(II) complexes were applied in the transfer hydrogenation of ketones. Their different catalytic activity were attributed to the alkyl arms on the 2,6-bis(5,6-dialkyl-1,2,4-triazin-3-yl)pyridine. As the length of the alkyl arms rising, the catalytic activities of the complex catalysts decreased. By means of 0.4 mol % catalyst RuCl2(PPh3)(3-methylbutyl-BTP) in refluxing 2-propanol, a variety of ketones were reduced to their corresponding alcohols with >95% conversion over a period of 3 h.
- Wang, Liandi,Liu, Tingting
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supporting information
(2019/08/12)
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- Diastereoselective Synthesis of Cyclic sp 3 -Enriched cis -β-Alkoxysulfonyl Chlorides
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A three-step synthesis of β-alkoxy-substituted alicyclic sulfonyl chlorides from cyclic alkenes and alcohols is reported. The scope of the method was studied for a range of the substrates with various steric and electronic properties. The title compounds were obtained on a hundred-gram scale in up to 52% overall yield scale as single cis -diastereomers.
- Sokolov, Andriy,Golovach, Sergey,Kozlinsky, Ihor,Dolia, Krystyna,Tolmachev, Andrey A.,Kuchkovska, Yuliya,Grygorenko, Oleksandr O.
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supporting information
p. 848 - 858
(2019/02/10)
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- Cooperative Mn(i)-complex catalyzed transfer hydrogenation of ketones and imines
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The synthesis and reactivity of Mn(i) complexes bearing bifunctional ligands comprising both the amine N-H and benzimidazole fragments are reported. Among the various ligands, the N-((1H-benzimidazol-2-yl)methyl)aniline ligand containing Mn(i) complex presented higher reactivity in the transfer hydrogenation (TH) of ketones in 2-propanol. Experimentally, it was established that both the benzimidazole and amine N-H proton played a vital role in the enhancement of the catalytic activity. Utilizing this system a wide range of aldehydes and ketones were reduced efficiently. Notably, the TH of several imines, as well as chemoselective reduction of unsaturated ketones, was achieved in the presence of this catalyst. DFT calculations were carried out to understand the plausible reaction mechanism which disclosed that the transfer hydrogenation reaction followed a concerted outer-sphere mechanism.
- Ganguli, Kasturi,Shee, Sujan,Panja, Dibyajyoti,Kundu, Sabuj
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p. 7358 - 7366
(2019/06/06)
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- Aliphatic amines modified CoO nanoparticles for catalytic oxidation of aromatic hydrocarbon with molecular oxygen
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The surface modification of metal oxides using organic modifiers is a potential strategy for enhancing their catalytic performances. In this study, a hydrophobic surface amine-modified CoO catalyst with a water contact angle of 143° was fabricated. The catalyst was characterized by XRD, TGA, FT-IR, HR-TEM, and XPS. The results showed that the fabricated catalyst performed better than the hydrophilic commercial CoO nanoparticle in the process of aromatic hydrocarbon oxidation. After the amines modification, commercial CoO also became hydrophobic and improved conversion of ethylbenzene was achieved. The surface modification of CoO with amines induced the hydrophobicity property, which could serve as a reference for the design of other hydrophobic catalysts.
- Liu, Meng,Shi, Song,Zhao, Li,Chen, Chen,Gao, Jin,Xu, Jie
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p. 1488 - 1493
(2019/09/09)
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- Scalable Wolff-Kishner Reductions in Extreme Process Windows Using a Silicon Carbide Flow Reactor
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A safe and scalable continuous flow strategy for Wolff-Kishner reductions that employs methanol as the solvent has been developed. The use of low-cost hydrazine as the reducing agent in combination with a caustic base provides an atom-efficient, environmentally friendly method for the deoxygenation of aldehydes and ketones to alkanes. Because of the required harsh and corrosive reaction conditions (200 °C, 50 bar), reactor materials such as stainless steel, glass, or any type of polymer have compatibility problems, rendering this process problematic on a production scale. The use of corrosion-resistant silicon carbide (SiC) as the reactor material opens up the possibility of performing Wolff-Kishner reductions on scale with a considerably improved safety profile. Methanol as the solvent significantly simplifies the workup procedure compared with the generally employed high-boiling solvents such as diethylene glycol. The continuous flow protocol was applied to a number of substrates and provided the desired products in good to high yields with space-time yields of up to 152 g L-1 h-1. In addition, a pharmaceutically valuable active pharmaceutical ingredient precursor was synthesized by employing this higherature/pressure Wolff-Kishner protocol.
- Znidar, Desiree,O'Kearney-Mcmullan, Anne,Munday, Rachel,Wiles, Charlotte,Poechlauer, Peter,Schmoelzer, Christoph,Dallinger, Doris,Kappe, C. Oliver
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supporting information
p. 2445 - 2455
(2019/11/03)
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- Photocatalytic Oxidation of Α-C?H Bonds in Unsaturated Hydrocarbons through a Radical Pathway Induced by a Molecular Cocatalyst
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To improve the photocatalytic oxidation of α-C?H bonds in unsaturated hydrocarbons, N-hydroxyphthalimide (NHPI) was used as a molecular cocatalyst with CdS as the photoabsorber. Compared with previously reported photocatalysts involving solid cocatalysts, metal-free NHPI offers better sustainability in addition to the significantly enhanced performance as cocatalyst. The photogenerated holes were transferred into the more active phthalimide-N-oxyl radical (PINO) by reacting with NHPI. In this way, α-C?H bond oxidation was significantly improved through the activation by PINO; even for the sluggish toluene oxidation, the apparent quantum efficiency was as high as 36.5 %. The effects of substrates/NHPI concentration ratio, reaction temperature, and time as well as the reaction intermediates were comprehensively studied. It was possible to identify ketones/aldehydes as the primary products, and overoxidation was controlled by adjusting the substrates/NHPI concentration ratio and reaction time. Thus, the radical path induced by the NHPI–PINO redox pair is an efficient alternative to boost the sluggish photocatalytic oxidation of α-C?H bonds.
- Zhao, Guixia,Hu, Bin,Busser, G. Wilma,Peng, Baoxiang,Muhler, Martin
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p. 2795 - 2801
(2019/06/24)
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- Practical and selective hydroboration of aldehydes and ketones in air catalysed by an iron(ii) coordination polymer
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The in air catalytic hydroboration of ketones and aldehydes with pinacolborane by an iron(ii) coordination polymer (CP) is carried out under mild and solvent-free conditions. The precatalyst is highly active towards a wide range of substrates including functionalized ketones and aldehydes in the presence of KOtBu as an activator, achieving a high turnover number (TON) of up to 9500. Excellent chemoselectivity to aldehydes over ketones was also revealed, which is in sharp contrast with the results obtained under inert atmosphere using the same catalyst system. This catalyst observed here is not only highly efficient but also recyclable for reuse for at least 5 times without losing its effectiveness.
- Zhang, Guoqi,Cheng, Jessica,Davis, Kezia,Bonifacio, Mary Grace,Zajaczkowski, Cynthia
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p. 1114 - 1121
(2019/03/12)
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- Combining Photo-Organo Redox- and Enzyme Catalysis Facilitates Asymmetric C-H Bond Functionalization
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In this study, we combined photo-organo redox catalysis and biocatalysis to achieve asymmetric C–H bond functionalization of simple alkane starting materials. The photo-organo catalyst anthraquinone sulfate (SAS) was employed to oxyfunctionalise alkanes to aldehydes and ketones. We coupled this light-driven reaction with asymmetric enzymatic functionalisations to yield chiral hydroxynitriles, amines, acyloins and α-chiral ketones with up to 99 % ee. In addition, we demonstrate functional group interconversion to alcohols, esters and carboxylic acids. The transformations can be performed as concurrent tandem reactions. We identified the degradation of substrates and inhibition of the biocatalysts as limiting factors affecting compatibility, due to reactive oxygen species generated in the photocatalytic step. These incompatibilities were addressed by reaction engineering, such as applying a two-phase system or temporal and spatial separation of the catalysts. Using a selection of eleven starting alkanes, one photo-organo catalyst and 8 diverse biocatalysts, we synthesized 26 products and report for the model compounds benzoin and mandelonitrile > 97 % ee at gram scale.
- Zhang, Wuyuan,Fueyo, Elena Fernandez,Hollmann, Frank,Martin, Laura Leemans,Pesic, Milja,Wardenga, Rainer,H?hne, Matthias,Schmidt, Sandy
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supporting information
p. 80 - 84
(2019/01/04)
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- Conversion of Olefins into Ketones by an Iron-Catalyzed Wacker-type Oxidation Using Oxygen as the Sole Oxidant
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We describe a mild and operationally simple procedure for the oxidation of olefins into ketones. The reaction is catalyzed by the hexadecafluorinated iron–phthalocyanine complex FePcF16 with stoichiometric amounts of triethylsilane as an additive under oxygen atmosphere to give ketones in good to high yields with excellent chemoselectivity and functional group tolerance. Ketone formation proceeds in up to 95 % yield and with 100 % regioselectivity while the corresponding alcohols were observed as side products.
- Puls, Florian,Kn?lker, Hans-Joachim
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supporting information
p. 1222 - 1226
(2018/01/01)
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- Visible-Light-Mediated Aerobic Oxidation of Organoboron Compounds Using in Situ Generated Hydrogen Peroxide
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A simple and general visible-light-mediated oxidation of organoboron compounds has been developed with rose bengal as the photocatalyst, substoichiometric Et3N as the electron donor, as well as air as the oxidant. This mild and metal-free protocol shows a broad substrate scope and provides a wide range of aliphatic alcohols and phenols in moderate to excellent yields. Notably, the robustness of this method is demonstrated on the stereospecific aerobic oxidation of organoboron compounds.
- Weng, Wei-Zhi,Liang, Hao,Zhang, Bo
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p. 4979 - 4983
(2018/08/24)
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- “Inverse” Frustrated Lewis Pairs: An Inverse FLP Approach to the Catalytic Metal Free Hydrogenation of Ketones
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For the first time have boron-containing weak Lewis acids been demonstrated to be active components of Frustrated Lewis Pair (FLP) catalysts in the hydrogenation of ketones to alcohols. Combining the organosuperbase (pyrr)3P=NtBu with the Lewis acid 9-(4-CF3-C6H4)-BBN generated an “inverse” FLP catalyst capable of hydrogenating a range of aliphatic and aromatic ketones including N-, O- and S-functionalized substrates and bio-mass derived ethyl levulinate. Initial computational and experimental studies indicate the mechanism of catalytic hydrogenation with “inverse” FLPs to be different from conventional FLP catalysts that contain strong Lewis acids such as B(C6F5)3.
- Mummadi, Suresh,Brar, Amandeep,Wang, Guoqiang,Kenefake, Dustin,Diaz, Rony,Unruh, Daniel K.,Li, Shuhua,Krempner, Clemens
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supporting information
p. 16526 - 16531
(2018/10/20)
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- Enantioselective metal-free reduction of ketones by a user-friendly silane with a reusable chiral additive
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1-Hydrosilatrane, a safe and easy-to-handle reducing reagent that can be inexpensively accessed, has been shown to reduce prochiral ketones asymmetrically in the presence of chiral 1,2-aminoalcohols with ees ranging from 8% to 86%. The best result was achieved using ephedrine as the source of chirality, which is readily commercially available. The additive can be recovered through extraction and reused without any erosion of enantioselectivity.
- Varjosaari, Sami E.,Skrypai, Vladislav,Herlugson, Sharon M.,Gilbert, Thomas M.,Adler, Marc J.
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supporting information
p. 2839 - 2843
(2018/06/25)
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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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supporting information
p. 12259 - 12263
(2018/08/28)
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- Iridium-catalyzed efficient reduction of ketones in water with formic acid as a hydride donor at low catalyst loading
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A highly efficient and chemoselective transfer hydrogenation of ketones in water has been successfully achieved with our newly developed catalyst. Simple ketones, as well as α- or β-functionalized ketones, are readily reduced. Formic acid is used as a traceless hydride source. At very low catalyst loading (S/C = 10:000 in most cases; S/C = 50:000 or 100:000 in some cases), the iridium catalyst is impressively efficient at reducing ketones in good to excellent yields. The TOF value can be as high as up to 26:000 mol mol-1 h-1. A variety of functional groups are well tolerated, for example, heteroaryl, aryloxy, alkyloxy, halogen, cyano, nitro, ester, especially acidic methylene, phenol and carboxylic acid groups.
- Liu, Ji-Tian,Yang, Shiyi,Tang, Weiping,Yang, Zhanhui,Xu, Jiaxi
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supporting information
p. 2118 - 2124
(2018/05/24)
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- (Poly)cationic λ3-Iodane-Mediated Oxidative Ring Expansion of Secondary Alcohols
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Herein, a simplified approach to the synthesis of medium-ring ethers through the electrophilic activation of secondary alcohols with (poly)cationic λ3-iodanes (N-HVIs) is reported. Excellent levels of selectivity are achieved for C–O bond migration over established α-elimination pathways, enabled by the unique reactivity of a novel 2-OMe-pyridine-ligated N-HVI. The resulting hexafluoroisopropanol (HFIP) acetals are readily derivatized with a range of nucleophiles, providing a versatile functional handle for subsequent manipulations. The utility of this methodology for late-stage natural product derivatization was also demonstrated, providing a new tool for diversity-oriented synthesis and complexity-to-diversity (CTD) efforts. Preliminary mechanistic investigations reveal a strong effect of alcohol conformation on the reactive pathway, thus providing a predictive power in the application of this approach to complex molecule synthesis.
- Walters, Jennifer C.,Tierno, Anthony F.,Dubin, Aimee H.,Wengryniuk, Sarah E.
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supporting information
p. 1460 - 1464
(2018/04/06)
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- Hydrosilylation of Carbonyl Compounds Catalyzed through a Lithiated Hydrazone Derivative
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A well-defined lithiated hydrazone derivative has been synthesized and fully characterized through various analytical platforms, including multinuclear (1H, 13C, 15N, 7Li) and two-dimensional NMR, high-resolution MS spectrometry, IR, and X-ray diffraction crystallography. It behaves as a binuclear species in the solid state and as a monomeric contact ion pair in solution. It has also been tested as a catalyst in hydrosilylation reactions, being the first lithium hydrazone reported to catalyze the full conversion of carbonyls of different nature into alcohols in short reaction times, at room temperature, and with catalyst loadings equal to or below 0.5 mol %. Kinetic studies have proven fractional order dependences with respect to ketone and silane and first order dependence in the case of the catalyst. The proposed reaction mechanism is characterized by the nucleophilic addition of the lithium hydrazonide to the silicon atom of the silane to give a five-coordinate silicon species.
- Raya-Barón, álvaro,O?a-Burgos, Pascual,Rodríguez-Diéguez, Antonio,Fernández, Ignacio
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p. 2682 - 2689
(2018/09/10)
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