- Microwave-assisted syntheses of 1,2-diketones
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A comparative study of the conversion of a number of α-hydroxyketones into 1,2-diketones by three oxidants under microwave irradiation is reported.
- Mitra, Alok Kumar,De, Aparna,Karchaudhuri, Nilay
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- The novel and efficient reduction of graphene oxide using Ocimum sanctum L. leaf extract as an alternative renewable bio-resource
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The efficient, rapid, bio-inspired synthesis of reduced graphene oxide (rGO) nanosheets was explored using green leaf extract of Ocimum sanctum L. (Tulsi leaves). This mild biorenewable reducing agent containing eugenol, ascorbic acid, and polyols also acts as a stabilizer for the prepared rGO. Characterization of the synthesized graphene nanosheets was performed using XPS, TEM, SEM, XRD, FT-IR, Raman and UV-vis spectroscopy studies. The catalytic application of the prepared rGO was established through the fruitful reduction of α,β-unsaturated aldehydes to the corresponding allylic alcohols in aqueous media. Excellent yields of pure products (92%) in addition to regioselective reduction were practically observed.
- Mahata, Suhasini,Sahu, Anjumala,Shukla, Prashant,Rai, Ankita,Singh, Manorama,Rai, Vijai K.
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- Unique Regio- and Stereoselectivity in Pd-Catalyzed Chlorocarbonylation Reaction of 2-Phenylethynyl Selenides and 2-Alkylethynyl Selenides. Highly Stereoselective Synthesis of 2-Seleno-3-chloroacrylates
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Regio- and stereoselectivity in the chloropalladation carbonylation reaction of different acetylenic selenides in the presence of 0.05 equiv of PdCl2 and 3 equiv of cupric chloride under 1 atm of carbon monoxide affording 2-seleno-3-chloroacrylates were investigated. Opposite stereoselectivities were observed with 2-phenylethynyl selenides and 2-alkylethynyl selenides: the reactions of 2-phenylethynyl selenides afforded (E)-2-seleno-3-chloro-3-phenylacrylates, while the reactions of 2-alkylethynyl selenides gave (Z)-2-seleno-3-chloro-3-alkylacrylates. A chloropalladation carbonylation mechanism for this reaction was proposed. The regio- and stereoselective chloropalladation of the carbon-carbon triple bond in acetylenic selenides affords 1-enylpalladium intermediates, in which the palladium atom connects with the carbon atom bonding with the selenium atom. Carbonylation in the presence of an alcohol affords 2-seleno-3-chloroacrylates.
- Huang, Xian,Sun, Aiming
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- Accelerated reduction of carbonyl compounds under microwave irradiation
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Aldehydes and ketones are quickly reduced to alcohols by aluminium isopropoxide under microwave irradiation.
- Barbry, Didier,Torchy, Severine
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- Trimerisation of the cationic fragments [(eta ring)M(Aa)]+ (where eta ring)M=eta 5 pentamethylcyclopentadienyl rhodium, eta 5 pentamethylcyclopentadienyl iridium, or eta 6 4isopropyltolyl ruthenium and Aa = alpha amino acidate) with chiral self-recognition: Synthesis, characterisation, solution studies and catalytic reactions of the trimers tris[eta ring M(Aa)] tris(tetrafluoroborate)
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The mononuclear neutral chlorides [(η-ring)M(Aa)Cl] ((η-ring)-M- (η5-C5Me5)Rh, (η5-C5Me5)Ir, (η6-p-MeC6H4iPr)Ru; Aa = α-amino acidate) were treated with AgBF4 to yield the corresponding new chiral trimers [{(η-ring)M(Aa)}3](BF4)3. Compounds [{(η5- C5Me5)Ir(Ala)}3](BF4)3 (1b) and [{(η6-p-MeC6H4iPr)Ru(L- Pro)}3](BF4)3 (6c) were characterised by X-ray diffraction. Trimerisation takes place by chiral self-recognition: the trimers R(M)R(M)R(M) (ρ isomer) or S(M)S(M)S(M) (σ isomer), which have equal configuration at the metal centre, were the only diastereomers detected. In solution, a diastereomerisation process between both isomers occurs, where the equilibrium constant depends on the solvent, amino acidate, and metal. The different localisation of the polar groups (NH or NH2 moieties) on the molecular surface of the two diastereomers (ρ and σ) provides a qualitative explanation for the different diastereomer stability observed in solution. The new chiral trimers catalyse the reduction of unsaturated aldehydes to unsaturated alcohols by hydrogen transfer from aqueous sodium formate and the reduction of acetophenone by hydrogen transfer from 2-propanol with up to 75 % ee.
- Carmona, Daniel,Lahoz, Fernando J.,Atencio, Reinaldo,Oro, Luis A.,Lamata, M. Pilar,Viguri, Fernando,San Jose, Emilio,Vega, Cristina,Reyes, Josefa,Joo, Ferenc,Katho, Agnes
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- Selectivity in the electrochemical deprotection of cinnamyl groups from oxygen and nitrogen functionalities: Carbonates versus carbamates
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Several cinnamyloxy carbamates and carbonates were subjected to electrochemical reduction, and the reductive fate of the cinnamyl group was investigated. Complete selectivity was observed in the removal of the cinnamyl group from oxygen versus nitrogen.
- Canka?, Petr,Dubas, Diane,Banfield, Scott C.,Chahma, M'hamed,Hudlicky, Tomas
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- Oxoammonium-Mediated Allylsilane–Ether Coupling Reaction
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A new C(sp3)?H functionalization reaction consisting of the oxidative α-allylation of allyl- and benzyl- methyl ethers has been developed. The C?C coupling could be carried out under mild conditions thanks to the use of cheap and green oxoammonium salts. The scope of the reaction was studied over 27 examples, considering the nature of the substituents on the two coupling partners.
- Carlet, Federica,Bertarini, Greta,Broggini, Gianluigi,Pradal, Alexandre,Poli, Giovanni
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supporting information
p. 2162 - 2168
(2021/04/02)
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- Ruthenium-Catalyzed E-Selective Partial Hydrogenation of Alkynes under Transfer-Hydrogenation Conditions using Paraformaldehyde as Hydrogen Source
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E-alkenes were synthesized with up to 100 % E/Z selectivity via ruthenium-catalyzed partial hydrogenation of different aliphatic and aromatic alkynes under transfer-hydrogenation conditions. Paraformaldehyde as a safe, cheap and easily available solid hydrogen carrier was used for the first time as hydrogen source in the presence of water for transfer-hydrogenation of alkynes. Optimization reactions showed the best results for the commercially available binuclear [Ru(p-cymene)Cl2]2 complex as pre-catalyst in combination with 2,2-bis(diphenylphosphino)-1,1-binaphthyl (BINAP) as ligand (1 : 1 ratio per Ru monomer to ligand). Mechanistic investigations showed that the origin of E-selectivity in this reaction is the fast Z to E isomerization of the formed alkenes. Mild reaction conditions plus the use of cheap, easily available and safe materials as well as simple setup and inexpensive catalyst turn this protocol into a feasible and promising stereo complementary procedure to the well-known Z-selective Lindlar reduction in late-stage syntheses. This procedure can also be used for the production of deuterated alkenes simply using d2-paraformaldehyde and D2O mixtures.
- Fetzer, Marcus N. A.,Tavakoli, Ghazal,Klein, Axel,Prechtl, Martin H. G.
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p. 1317 - 1325
(2021/02/11)
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- Differentiation of Pt?Fe and Pt?Ni3 Surface Catalytic Mechanisms towards Contrasting Products in Chemoselective Hydrogenation of α,β-Unsaturated Aldehydes
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Noble-metal catalysts serve as an irreplaceable role in pharmaceutical, perfume and fine chemicals fields. However, there still remains a grand challenge in controlling chemoselectivity. Herein, we have synthesized a bimetallic nanostructure supported on porous metal-organic frameworks (Pt?Fe/UiO-66, Pt-Ni3/UiO-66), in which Pt nanoparticles was modified with non-noble metal (Fe or Ni) directly. The as-synthesized catalysts can function as a switch for selective hydrogenation of α,β-unsaturated aldehydes to afford the potential products on-demand. In comparison with the conventional Pt-based catalysts, Pt?Fe/UiO-66 and Pt-Ni3/UiO-66 catalysts exhibit excellently catalytic activity, enhanced selectivity and improved stability for selectivity hydrogenation. The partial charge reconfiguration and electronic coupling effect existing in such distinctive bicomponent nanocatalysts was confirmed by some comprehensive characterization and density functional theory (DFT) calculations. The developed method for precisely modification the composition and interaction between the noble metal and non-noble metal provides a feasible avenue to design the advanced catalysts.
- Ning, Liangmin,Zhang, Mingtao,Liao, Shengyun,Zhang, Yuting,Jia, Dandan,Yan, Yunfang,Gu, Wen,Liu, Xin
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p. 704 - 711
(2020/12/07)
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- Platinum and cobalt intermetallic nanoparticles confined within MIL-101(Cr) for enhanced selective hydrogenation of the carbonyl bond in a,?-unsaturated aldehydes: synergistic effects of electronically modified Pt sites and Lewis acid sites
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Precious metals have been shown to play a vital role in the selective hydrogenation of a,?-unsaturated aldehydes, but still suffer from challenges to control selectivity. Herein, we have advanced the design of catalysts made out of Pt-Co intermetallic nanoparticles (IMNs) supported on a MIL-101(Cr) MOF (3%Pty%Co/MIL-101(Cr)), prepared by using a polyol reduction method, as an effective approach to enhance selectivity toward the production of a,?-unsaturated alcohol, the desired product. XRD, N2adsorption-desorption, FTIR spectroscopy, SEM, TEM, XPS, CO adsorption, NH3-TPD, XANES and EXAFS measurements were used to investigate the structure and surface properties of our 3%Pty%Co/MIL-101(Cr) catalysts. It was found that the Co-modified 3%Pty%Co/MIL-101(Cr) catalysts can indeed improve the hydrogenation of cinnamaldehyde (CAL) to cinnamyl alcohol (COL), reaching a higher selectivity under mild conditions than the monometallic Pt/MIL-101(Cr) catalysts: 95% conversion of CAL with 91% selectivity to COL can be reached with 3%Pt3%Co/MIL-101(Cr). Additionally, high conversion of furfural (97%) along with high selectivity to furfural alcohol (94%) was also attained with the 3%Pt3%Co/MIL-101(Cr) catalyst. The enhanced activity and selectivity toward the unsaturated alcohols are attributed to the electronic and geometric effects derived from the partial charge transfer between Co and Pt through the formation of uniformly dispersed Pt-Co IMNs. Moreover, various characterization results revealed that the addition of Co to the IMPs can promote the Lewis acid sites that facilitate the polarization of the charge-rich C?O bonds and their adsorptionviatheir oxygen atom, and also generate new interfacial acid sites.
- Zahid, Muhammad,Li, Jiang,Ismail, Ahmed,Zaera, Francisco,Zhu, Yujun
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p. 2433 - 2445
(2021/04/22)
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- Platinum Nanosheets Intercalated into Natural and Artificial Graphite Powders
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Insertion of sheet-type platinum particles (platinum nanosheets) between graphite layers was achieved by a thermal treatment of a mixture of platinum chloride (IV) and graphite powder (natural graphite or artificial graphite) under 0.3 MPa of chlorine at 723 K, followed by the treatment under 40 kPa of hydrogen pressure. Similar platinum nanosheets, which were 1–3 nm in thickness and 100–500 nm in width and had a number of hexagonal holes and edges with 120° angle, were formed between the layers of both natural graphite or artificial graphite; however, their location in the graphite layers depended on the type of graphite used. A number of platinum nanosheets were observed in the edge region of natural graphite particles which have flat surface. On the other hand, a number of platinum nanosheets were found inside and away from the edge of the artificial graphite particles especially in the vicinity of the cracks. Both the platinum nanosheet-containing artificial and natural graphite samples showed high selectivity to cinnamyl alcohol in cinnamaldehyde hydrogenation under supercritical carbon dioxide conditions, while spherical platinum particles, which were located on the surface of natural and artificial graphite, showed lower selectivity.
- Shirai, Masayuki,Kubo, Kohei,Sodeno, Mika,Nanao, Hidetaka
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p. 2035 - 2040
(2021/06/25)
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- Supported silver catalysts prepared via melt infiltration: Synthesis, characterization and performance in selective hydrogenation
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Heterogeneous supported catalysts are often synthesized by impregnation or precipitation methods. Recently, melt infiltration has emerged as an alternative method that allows high metal loadings and eliminates the need for a solvent, but challenges arise regarding control over the particle size and distribution. In this work, melt infiltration for the synthesis of supported silver catalysts is explored. The narrow pore size distribution of the chosen ordered mesoporous silica support, SBA-15, allowed in depth in-situ and ex-situ characterization of the infiltration of the precursor, molten silver nitrate, into the support and its subsequent decomposition to form metallic silver nanowires or nanoparticles. The heat treatment parameters during decomposition played a key role in determining whether nanowires or nanoparticles were formed. The supported silver catalysts containing high silver weight loadings were investigated in the selective hydrogenation of cinnamaldehyde, where the silver nanowires showed superior activity and selectivity over the nanoparticles. Hence, melt infiltration shows great promise for the synthesis of supported silver catalysts containing high silver weight loadings, which are applicable in, e.g., selective oxidation or hydrogenation reactions.
- Keijzer,Donoeva,de Jong,de Jongh
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p. 393 - 400
(2020/04/01)
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- Manganese-Catalyzed Hydrogenation of Ketones under Mild and Base-free Conditions
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In this paper, several Mn(I) complexes were applied as catalysts for the homogeneous hydrogenation of ketones. The most active precatalyst is the bench-stable alkyl bisphosphine Mn(I) complex fac-[Mn(dippe) (CO)3(CH2CH2CH3)]. The reaction proceeds at room temperature under base-free conditions with a catalyst loading of 3 mol % and a hydrogen pressure of 10 bar. A temperature-dependent selectivity for the reduction of α,β-unsaturated carbonyls was observed. At room temperature, the carbonyl group was selectively hydrogenated, while the C=C bond stayed intact. At 60 °C, fully saturated systems were obtained. A plausible mechanism based on DFT calculations which involves an inner-sphere hydride transfer is proposed.
- Brünig, Julian,Kirchner, Karl,Veiros, Luis F.,Weber, Stefan
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supporting information
p. 1388 - 1394
(2021/05/31)
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- Efficient and chemoselective hydrogenation of aldehydes catalyzed by well-defined PN3-pincer manganese(ii) catalyst precursors: An application in furfural conversion
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Well-defined and air-stable PN3-pincer manganese(ii) complexes were synthesized and used for the hydrogenation of aldehydes into alcohols under mild conditions using MeOH as a solvent. This protocol is applicable for a wide range of aldehydes containing various functional groups. Importantly, α,β-unsaturated aldehydes, including ynals, are hydrogenated with the CC double bond/CC triple bond intact. Our methodology was demonstrated for the conversion of biomass derived feedstocks such as furfural and 5-formylfurfural to furfuryl alcohol and 5-(hydroxymethyl)furfuryl alcohol respectively.
- Gholap, Sandeep Suryabhan,Dakhil, Abdullah Al,Chakraborty, Priyanka,Li, Huaifeng,Dutta, Indranil,Das, Pradip K.,Huang, Kuo-Wei
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supporting information
p. 11815 - 11818
(2021/11/30)
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- CeO2-nanocubes as efficient and selective catalysts for the hydroboration of carbonyl groups
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The CeO2-nanoparticle catalysed hydroboration of carbonyl compounds with HBpin (pin = OCMe2CMe2O) is reported to afford the corresponding borate esters in excellent yield. A series of aromatic and aliphatic aldehydes and ketones having synthetically important functional groups were well-Tolerated under mild reaction conditions. Further, chemoselective hydroboration of aldehydes over other reducible functional groups such as ketone, nitrile, hydroxide, alkene, alkyne, amide, ester, nitro, and halides was achieved. Importantly the catalyst can be recycled up to ten runs with slight loss in activity. This journal is
- Bhawar, Ramesh,Bose, Shubhankar Kumar,Patil, Kiran S.
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supporting information
p. 15028 - 15034
(2021/09/04)
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- Wittig Olefination Using Phosphonium Ion-Pair Reagents Incorporating an Endogenous Base
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Despite common perception, the use of strong bases in Wittig chemistry is utterly unnecessary: we report a series of novel ion-pair phosphonium carboxylate reagents which are essentially "storable ylides". These reagents are straightforwardly prepared in excellent yields, and their fluxional nature permits clean olefination of a broad range of aldehydes and even hemiacetals.
- Vetter, Anna C.,Gilheany, Declan G.,Nikitin, Kirill
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supporting information
p. 1457 - 1462
(2021/03/08)
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- Strong acid-catalyzed electrophilic ring expansion of oxetanes and sulfoxonium ylides
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A strong protic acid-catalyzed electrophilic ring expansion of oxetanes into trans-2,3-disubstituted tetrahydrofuran derivatives using sulfoxonium ylides has been developed. This reaction produces functionalized trans-2,3-disubstituted tetrahydrofuran derivatives stereospecifically by using safe and stable sulfoxonium ylides without metal catalysts and the protection of inert gas.
- Xie, Wenlai,Xu, Jiaxi,Yuan, Wenhao
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- Catalytic enantioselective addition of alkylzirconium reagents to aliphatic aldehydes
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A catalytic methodology for the enantioselective addition of alkylzirconium reagents to aliphatic aldehydes is reported here. The versatile and readily accessible chiral Ph-BINMOL ligand, in the presence of Ti(OiPr)4 and a zinc salt, facilitates the reaction, which proceeds under mild conditions and is compatible with functionalized nucleophiles. The alkylzirconium reagents are conveniently generated in situ by hydrozirconation of alkenes with the Schwartz reagent. This work is a continuation of our previous work on aromatic aldehydes.
- Carter, Nicholas,González-Soria, María José,Maciá, Beatriz,Vaccari, Jade
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- Hydrosilylation of Aldehydes and Ketones Catalyzed by a 2-Iminopyrrolyl Alkyl-Manganese(II) Complex
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A well-defined and very active single-component manganese(II) catalyst system for the hydrosilylation of aldehydes and ketones is presented. First, the reaction of 5-(2,4,6-iPr3C6H2)-2-[N-(2,6-iPr2C6H3)formimino]pyrrolyl potassium (KL) and [MnCl2(Py)2] afforded the binuclear 2-iminopyrrolyl manganese(II) pyridine chloride complex [Mn2{κ2N,N′-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H)═N(2,6-iPr2C6H3)}2(Py)2(μ-Cl)2] 1. Subsequently, the alkylation reaction of complex 1 with LiCH2SiMe3 afforded the respective (trimethylsilyl)methyl-Mn(II) complex [Mn{κ2N,N′-5-(2,4,6-iPr3C6H2)-NC4H2-2-C(H)═N(2,6-iPr2C6H3)}(Py)CH2SiMe3] 2 in a good yield. Complexes 1 and 2 were characterized by elemental analysis, 1H NMR spectroscopy, Evans' method, FTIR spectroscopy, and single-crystal X-ray diffraction. While the crystal structure of complex 1 has been identified as a binuclear entity, in which the Mn(II) centers present pentacoordinate coordination spheres, that of complex 2 corresponds to a monomer with a distorted tetrahedral coordination geometry. Complex 2 proved to be a very active precatalyst for the atom-economic hydrosilylation of several aldehydes and ketones under very mild conditions, with a maximum turnover frequency of 95 min-1, via a silyl-Mn(II) mechanistic route, as asserted by a combination of experimental and theoretical efforts, the respective silanes were cleanly converted to the respective alcoholic products in high yields.
- Cruz, Tiago F. C.,Gomes, Pedro T.,Veiros, Luís F.
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- Synthetic and Mechanistic Studies on 2,3-Dihydrobenzo[ b ][1,4]-oxaselenines Formation from Selenocyanates
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An expedient preparation of selenium-containing hetero-cycles via an m -chloroperbenzoic acid-mediated seleno-annulation starting from selenocyanate derivatives is described. In spite of its significance, this cyclization reaction is virtually understudied not only from the point of view of its scope, but also from the mechanistic aspects associated to this remarkable transformation. In this sense, several selenocyanate and thiocyanate derivatives bearing an aromatic ring were evaluated as substrates under different reaction conditions of this interesting cyclization yielding important insights on its scope as well as relevant information on the reaction mechanism.
- Bonesi, Sergio M.,Cattaneo, Mauricio,Chao, María N.,Rodriguez, Juan B.,Sanchez Gonzalez, Jonathan,Szajnman, Sergio H.
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p. 1643 - 1658
(2020/05/25)
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- PHARMACEUTICAL COMPOSITION FOR PREVENTING OR TREATING AGING-RELATED DISEASES CONTAINING DECURSIN DERIVATIVE AS ACTIVE INGREDIENT
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A composition for preventing or treating an aging-related disease includes a novel decursin derivative as an active ingredient, wherein the novel decursin derivative has exhibited an excellent effect of inhibiting progerin expression and excellent effect of inhibiting binding between progerin and lamin A, and it has been confirmed that the novel decursin derivative prolongs the survival period of animal models in which progerin was induced.
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Paragraph 0051-0055
(2020/02/27)
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- C–C Cross-Coupling Reactions of Organosilanes with Terminal Alkenes and Allylic Acetates Using PdII Catalyst Supported on Starch Coated Magnetic Nanoparticles
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Starch coated magnetic nanoparticles supported palladium catalyst has been explored to perform C–C cross coupling reactions, such as oxidative Heck coupling and Tsuji–Trost allylic coupling using organosilicon compounds as one of the coupling partners. The biopolymer coated magnetic catalyst was very easy to recover magnetically and was efficiently recycled in the subsequent batches. All the reactions were performed in air and thus the necessity of air and moisture free reaction condition is avoided. The present protocols show wide substrate scope and good yields of the products.
- Patra, Debabrata,Panja, Subir,Saha, Amit
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supporting information
p. 878 - 883
(2020/02/13)
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- Selective Synthesis of Z-Cinnamyl Ethers and Cinnamyl Alcohols through Visible Light-Promoted Photocatalytic E to Z Isomerization
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A photocatalytic E to Z isomerization of alkenes using an iridium photosensitizer under mild reaction conditions is disclosed. This method provides scalable and efficient access to Z-cinnamyl ether and allylic alcohol derivatives in high yields with excellent stereoselectivity. Importantly, this method also provides a powerful strategy for the selective synthesis of Z-magnolol and honokiol derivatives possessing potential biological activity.
- Li, Hengchao,Chen, Hang,Zhou, Yang,Huang, Jin,Yi, Jundan,Zhao, Hongcai,Wang, Wei,Jing, Linhai
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supporting information
p. 555 - 559
(2020/02/05)
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- Photocatalyzed Diastereoselective Isomerization of Cinnamyl Chlorides to Cyclopropanes
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Endergonic isomerizations are thermodynamically unfavored processes that are difficult to realize under thermal conditions. We report a photocatalytic and diastereoselective isomerization of acyclic cinnamyl chlorides to strained cyclopropanes. Quantum mechanical calculations (uM06-2X and DLPNO), including TD-DFT calculations, and experimental studies provide evidence for the energy transfer from an iridium photocatalyst to the allylic chloride substrate followed by C-Cl homolytic cleavage. Subsequent Cla￠ radical migration forms a localized triplet 1,3-diradical intermediate that, after intersystem crossing, undergoes ring-closing to form the desired product. The mild reaction conditions are compatible with a broad range of functional groups to generate chlorocyclopropanes in high yields and diastereoselectivities. A more efficient process is developed by addition of a catalytic amount of a nickel complex, and we propose a novel role for this cocatalyst to recycle an allyl chloride byproduct generated in the course of the reaction. The reaction is also shown to be stereoconvergent, as an E/Z mixture of cinnamyl chlorides furnish the anti-chlorocyclopropane product in high diastereoselectivity. We anticipate that the use of a visible light activated photocatalyst to transform substrates in combination with a transition metal catalyst to recycle byproducts back into the catalytic cycle will provide unique opportunities for the discovery of new reactivity.
- Dykstra, Ryan,Gutierrez, Osvaldo,Martin, Robert T.,Tambar, Uttam K.,Troian-Gautier, Ludovic,Xu, Bin
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supporting information
p. 6206 - 6215
(2020/04/27)
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- Aurovertin B derivative and preparation method and application thereof
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The invention relates to an aurovertin B derivative and a preparation method of the aurovertin B derivative, and application of the aurovertin B derivative in preparation of a medicine for treating triple-negative breast cancer. Compared with aurovertin B, the aurovertin B derivative disclosed by the invention has the advantages that the water solubility of the compound is improved, the bioavailability can be improved, and the preparation is convenient to prepare. Meanwhile, compared with aurovertin B, the aurovertin B derivative disclosed by the invention has the advantages that the derivative has obvious dose dependence, the toxicity of the compound to normal cells is reduced, and the druggability of the compound is improved. The aurovertin B derivative disclosed by the invention has a very strong inhibition effect on proliferation of triple-negative breast cancer cells, and the activity of the aurovertin B derivative is stronger than that of paclitaxel serving as a clinical drug.
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Paragraph 0015
(2020/09/23)
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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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- CNN pincer ruthenium complexes for efficient transfer hydrogenation of biomass-derived carbonyl compounds
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The ligand HCNNOMe (6-(4-methoxyphenyl)-2-aminomethylpyridine) is easily prepared from the commercially available 6-(4-methoxyphenyl)pyridine-2-carbaldehyde by the reaction of hydroxylamine and hydrogenation (H2, 1 atm) with Pd/C. The pincer complexes cis-[RuCl(CNNOMe)(PPh3)2] (1) and [RuCl(CNNOMe)(PP)] (PP = dppb, 2; and dppf, 3) are synthesized from [RuCl2(PPh3)3], HCNNOMe and PP (for 2 and 3) in 2-propanol with NEt3 at reflux and are isolated in 85-93% yield. Carbonylation of 1 (CO, 1 atm) gives [RuCl(CNNOMe)(CO)(PPh3)] (4) (79% yield) which cleanly reacts with Na[BArf4] and PCy3, affording the cationic trans-[Ru(CNNOMe)(CO)(PCy3)(PPh3)][BArf4] (5) (92% yield). These robust pincer complexes display remarkably high catalytic activity in the transfer hydrogenation (TH) of lignocellulosic biomass carbonyl compounds, using 2-propanol at reflux in a basic medium (NaOiPr or K2CO3). Thus, furfural, 5-(hydroxymethyl)furfural and Cyrene are reduced to the corresponding alcohols with 2 and 3, at S/C in the range of 10 000-100 000, within minutes or hours (TOF up to 1 500 000 h-1). The monocarbonyl complex 5 was found to be extremely active in the TH of cinnamaldehyde, vanillin derivatives and ethyl levulinate at S/C in the range of 10 000-50 000. Vanillyl alcohol is also obtained by the TH of vanillin with 5 (S/C = 500) in 2-propanol in the presence of K2CO3.
- Figliolia, Rosario,Cavigli, Paolo,Comuzzi, Clara,Del Zotto, Alessandro,Lovison, Denise,Strazzolini, Paolo,Susmel, Sabina,Zuccaccia, Daniele,Ballico, Maurizio,Baratta, Walter
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supporting information
p. 453 - 465
(2020/01/21)
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- Magnetic Fe3O4 nanoparticles as easily separable catalysts for efficient catalytic transfer hydrogenation of biomass-derived furfural to furfuryl alcohol
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Magnetic Fe3O4-12 nanoparticles, an easily separable heterogeneous catalyst, exhibits high catalytic performance in the catalytic transfer hydrogenation (CTH) reaction of biomass-derived furfural (FAL) to furfuryl alcohol (FOL) with 2-propanol (2-PrOH) as the hydrogen source (90.1 percent FOL yield at 160 °C for 5 h). Comparing Fe3O4 nanoparticles with different particle sizes found that the smaller the nanoparticles, the larger the BET surface area, pore volume and pore diameter, resulting in more acid-base active sites through BET, SEM, TEM, NH3-/CO2-TPD and other characterizations. Moreover, a scaled-up CTH experiment of FAL and a stepwise reaction from xylose to FOL verified that the catalytic system has great industrial application prospects. A feasible flowchart of the chemical process from xylose to FOL was designed, which can realize the regeneration of biomass resources (xylose derived from corncob), the reuse and recycling of catalysts and solvents, and minimize the amount of solvents and pollutant emissions.
- Cao, Jingjie,Feng, Shouhua,Hou, Pan,Liu, Hui,Ma, Mingwei,Tian, Ge,Yue, Huijuan,Zhang, Peng
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- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
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Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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supporting information
p. 21176 - 21182
(2020/09/17)
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- cis-Selective Transfer Semihydrogenation of Alkynes by Merging Visible-Light Catalysis with Cobalt Catalysis
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Herein, the first example of visible-light-driven, cobalt-catalyzed transfer semihydrogenation of alkynes to alkenes is reported. It is carried out by using Ir[dF(CF3)ppy]2(dtbbpy)]PF6 as photosensitizer, CoBr2/n-Bu3P as proton-reducing catalyst, and i-Pr2NEt/AcOH as the hydrogen source. Under the established catalytic system, the semihydrogenation proceeds with Z as the major selectivity and with inhibition of over-reduction. Under mild reaction conditions, both internal and terminal alkynes, as well as reducible functional groups such as halogen, cyano, and ester, are tolerated. Preliminary mechanistic studies revealed the dual role of the photosensitizer in initiating the reaction via a single-electron transfer process and controlling the stereoselectivity via an energy transfer process. (Figure presented.).
- Ding, Hai-Xin,Guo, Wen-Jie,He, Yong-Qin,Song, Xian-Rong,Tian, Wan-Fa,Xiao, Qiang,Ye, Jing
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supporting information
(2020/02/05)
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- Method for catalytically reducing alkynes into olefins through visible light induction
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The invention discloses a method for catalytically reducing alkynes into olefins through visible light induction. The method can avoid generation of over-reduced alkane products and the highest yieldis 99%. The method comprises the following steps: by taking an alkyne as a raw material, adding a photosensitizer and a cobalt catalyst, then adding a phosphine ligand or bipyridine ligand, an electronic sacrificial reagent, acetic acid and an organic solvent under inert gas protection, and irradiating with blue light at room temperature for 7-14 hours; and after the reaction is finished, spin-drying an obtained reaction solution, and carrying out silica gel column chromatography separation to obtain an olefin product; wherein the organic solvent is 1, 4-dioxane or tetrahydrofuran, and the alkyne is an aliphatic alkyne or an aromatic alkyne. Reduction of alkyne is realized through a hydrogen transfer strategy, use of dangerous hydrogen is avoided, generation of overreduction products is avoided, reaction conditions are mild, the reaction yield is high, and the method has a good application prospect.
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Paragraph 0047-0050
(2020/03/09)
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- Transfer semihydrogenation of alkynes catalyzed by imidazo[1,5-a]pyrid-3-ylidenepd complexes: Positive effects of electronic and steric features on N-heterocyclic carbene ligands
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To investigate the catalytic utility of the imidazo[1,5-a]pyrid-3-ylidene (IPC) ligand, Pd-catalyzed transfer semihydrogenation of alkynes with formic acid as a hydrogen source was conducted. The steric bulkiness of the substituent on N2 affected the configuration of the π-allyl moiety of the precatalyst of IPC-Pd-π-allyl complexes and the robustness of the catalytic process. The catalytic activities of IPC-Pd complexes were clearly higher than those of conventional NHC-Pd complexes.
- Mizuno, Takahiro,Murai, Toshiaki,Shibahara, Fumitoshi,Shibata, Yoshifuru
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p. 332 - 337
(2020/04/27)
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- Simpler and Cleaner Synthesis of Variously Capped Cobalt Nanocrystals Applied in the Semihydrogenation of Alkynes
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Unlike the classical organometallic approach, we report here a synthetic pathway requiring no reducing sources or heating to produce homogeneous hexagonal-close-packed cobalt nanocrystals (Co NCs). Involving a disproportionation process, this simple and fast (6 min) synthesis is performed at room temperature in the presence of ecofriendly fatty alcohols to passivate Co NCs. Through a recycling step, the yield of Co NCs is improved and the waste generation is limited, making this synthetic route cleaner. After an easy exchange of the capping ligands, we applied them as unsupported catalysts in the stereoselective semihydrogenation of alkynes.
- Moisset, A.,Petit, C.,Petit, M.,Salzemann, C.,Sodreau, A.,Vivien, A.
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supporting information
p. 13972 - 13978
(2020/10/09)
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- 1-D manganese(ii)-terpyridine coordination polymers as precatalysts for hydrofunctionalisation of carbonyl compounds
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Reductive catalysis with earth-abundant metals is currently of increasing importance and shows potential in replacing precious metal catalysis. In this work, we revealed catalytic hydroboration and hydrosilylation of ketones and aldehydes achieved by a structurally defined manganese(ii) coordination polymer (CP) as a precatalyst under mild conditions. The manganese-catalysed methodology can be applied to a range of functionalized aldehydes and ketones with turnover numbers (TON) of up to 990. Preliminary results on the regioselective catalytic hydrofunctionalization of styrenes by the Mn-CP catalyst are also presented.
- Johnson, Jahvon,Li, Sihan,Mo, Zixuan,Neary, Michelle C.,Zeng, Haisu,Zhang, Guoqi,Zheng, Shengping
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supporting information
p. 2610 - 2615
(2020/03/05)
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- Lithium Bromide/HBpin: A Mild and Effective Catalytic System for the Selective Hydroboration of Aldehydes and Ketones
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The catalytic hydroboration of aldehydes and ketones with HBpin was examined using simple and commercially available metal salts (Li, Na, and K). Among the tested salts, LiBr (0.5–1.0 mol%) was found to be an efficient catalyst for the hydroboration of various aldehydes and ketones at room temperature. Further, the chemoselective hydroboration of aldehydes over ketones was also demonstrated.
- An, Duk Keun,Choi, Hyeon Seong,Hwang, Hyonseok,Kim, Hanbi,Lee, Ji Hye,Shin, Hye Lim,Yi, Jaeeun
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p. 1009 - 1018
(2020/10/12)
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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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- Base-induced Sommelet–Hauser rearrangement of N-(α-(2-oxyethyl)branched)benzylic glycine ester-derived ammonium salts via a chelated intermediate
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The base-induced Sommelet–Hauser (S–H) rearrangement of N-(α-branched)benzylic glycine ester-derived ammonium salts 1 was investigated. When the α-branched substituent was a simple alkyl, such as a methyl or butyl, desired S–H rearrangement product 2 was obtained in low yield with formation of the [1,2] Stevens rearranged 4 and Hofmann eliminated products 5 and 6. However, when the α-branched substituent had a 2-oxy moiety, such as 2-acetoxyethyl or 2-benzoyloxyethyl, the yields of 2 were improved. These results could be explained by formation of chelated intermediate C that stabilizes the carbanionic ylide, and the subsequent initial dearomative [2,3] sigmatropic rearrangement would be accelerated. The existence of C was supported by mechanistic experiments. This enhancement effect is not very strong or effective; however, it will expand the synthetic usefulness of ammonium ylide rearrangements.
- Baba, Souya,Hirano, Kazuki,Tayama, Eiji
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- Exploration of the Fluoride Reactivity of Aryltrifluoroborate on Selective Cleavage of Diphenylmethylsilyl Groups
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The first known report on the fluoride catalytic reactivity of potassium aryltrifluoroborate is described. The fluoride reactivity of phenyltrifluoroborate was controlled by substituents on the trifluoroborate-attached benzene, such as the methoxy group a
- Fujiki, Katsumasa,Tanaka, Katsunori
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supporting information
p. 4616 - 4620
(2020/07/06)
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- Copper-Catalyzed Decarboxylative Hydrophosphinylation of α-Acyl-α-Diazoacetates
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A simple copper-catalyzed decarboxylation–denitrogenation C–P coupling reaction of α-acyl-α-diazoacetates with hydrophosphoryl compounds is reported. The reaction may proceed via a process involving the generation of (diazomethyl)ketones after hydrolysis in the presence of water and the hydrophosphinylation of the copper carbene intermediates. This finding may suggest the potential use of the relatively more readily available α-acyl-α-diazoacetates as replacement of (diazomethyl)ketones in some cases.
- Zhang, Can,Dong, Chao,Wang, Xin,Shen, Ruwei
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supporting information
p. 7440 - 7444
(2020/12/01)
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- Iron catalysed selective reduction of esters to alcohols
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The reaction of (dppBIAN)FeCl2 with 3 equivalents of n-BuLi affords a catalytically active anionic Fe complex; the nature of the anionic complex was probed using EPR and IR experiments and is proposed to involve a dearomatized, radical, ligand scaffold. This complex is an active catalyst for the hydrosilylation of esters to afford alcohols; loadings as low as 1 mol% were employed.
- Tamang, Sem Raj,Cozzolino, Anthony F.,Findlater, Michael
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supporting information
p. 1834 - 1838
(2019/02/20)
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- Hafnium Triflate as a Highly Potent Catalyst for Regio- and Chemoselective Deprotection of Silyl Ethers
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As a Group IVB transition metal Lewis acid, hafnium triflate [Hf(OTf) 4 ] exhibited exceptionally high potency in desilylations. Since the amounts of Hf(OTf) 4 required for the deprotection of 1°, 2°, 3° alkyl and aryl tert -butyldimethylsilyl (TBS) ethers are significantly different, ranging from 0.05 mol% to 3 mol%, regioselective deprotection of TBS could be easily implemented. Moreover, chemoselective cleavage of different silyl ethers or removal of TBS in the presence of most hydroxyl protecting groups was also accomplished. NMR analyses of silyl products from TBS deprotection indicated that Hf(OTf) 4 -catalyzed desilylation may proceed via different mechanisms, depending on the solvent used.
- Zheng, Xiu-An,Kong, Rui,Huang, Hua-Shan,Wei, Jing-Ying,Chen, Ji-Zong,Gong, Shan-Shan,Sun, Qi
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supporting information
p. 944 - 953
(2019/02/10)
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- Catalytic removal of tert-butyldimethylsilyl (TBS) ether by PVP-I
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A mild, efficient and rapid protocol the deprotection of alcoholic TBDMS ethers using PVP-1 as catalyst in methanol, the procedure of deprotection of various TBDMS ethers were found to be very convenient, easy work-up, high yielding.
- Ke, Yanxiong,Lu, Guangying,Ren, Jiangmeng,Wang, Di,Zeng, Bu-Bing
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- Developing glutathione-activated catechol-type diphenylpolyenes as small molecule-based and mitochondria-targeted prooxidative anticancer theranostic prodrugs
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Developing concise theranostic prodrugs is highly desirable for personalized and precision cancer therapy. Herein we used the glutathione (GSH)-mediated conversion of 2,4-dinitrobenzenesulfonates to phenols to protect a catechol moiety and developed stable pro-catechol-type diphenylpolyenes as small molecule-based prooxidative anticancer theranostic prodrugs. These molecules were synthesized via a modular route allowing creation of various pro-catechol-type diphenylpolyenes. As a typical representative, PDHH demonstrated three unique advantages: (1) capable of exploiting increased levels of GSH in cancer cells to in situ release a catechol moiety followed by its in situ oxidation to o-quinone, leading to preferential redox imbalance (including generation of H2O2 and depletion of GSH) and final selective killing of cancer cells over normal cells, and is also superior to 5-fluorouracil and doxorubicin, the widely used chemotherapy drugs, in terms of its ability to kill preferentially human colon cancer SW620 cells (IC50 = 4.3 μM) over human normal liver L02 cells (IC50 = 42.3 μM) with a favourable in vitro selectivity index of 9.8; (2) permitting a turn-on fluorescent monitoring for its release, targeting mitochondria and therapeutic efficacy without the need of introducing additional fluorophores after its activation by GSH in cancer cells; (3) efficiently targeting mitochondria without the need of introducing additional mitochondria-directed groups.
- Bao, Xia-Zhen,Dai, Fang,Wang, Qi,Jin, Xiao-Ling,Zhou, Bo
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p. 406 - 418
(2019/02/06)
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- Interconverting Lanthanum Hydride and Borohydride Catalysts for C=O Reduction and C?O Bond Cleavage
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The high catalytic reactivity of homoleptic tris(alkyl) lanthanum La{C(SiHMe2)3}3 is highlighted by C?O bond cleavage in the hydroboration of esters and epoxides at room temperature. The catalytic hydroboration tolerates functionality typically susceptible to insertion, reduction, or cleavage reactions. Turnover numbers (TON) up to 10 000 are observed for aliphatic esters. Lanthanum hydrides, generated by reactions with pinacolborane, are competent for reduction of ketones but are inert toward esters. Instead, catalytic reduction of esters requires activation of the lanthanum hydride by pinacolborane.
- Patnaik, Smita,Sadow, Aaron D.
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p. 2505 - 2509
(2019/02/01)
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- Suppressive activities of KC1–3 on HMGB1-mediated septic responses
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In the present study, several decursin analogues (KC1–3) were synthesized and evaluated in terms of their anti-septic activities on high mobility group box 1 (HMGB1)-mediated septic responses and survival rate in a mouse model of sepsis. KC1 and KC3, but not KC2, significantly reduced HMGB1 release in lipopolysaccharide (LPS)-activated human umbilical vein endothelial cells (HUVECs) and attenuated the cecal ligation and puncture (CLP)-induced release of HMGB1. Additionally, in vitro analyses revealed that KC1 and KC3 both alleviated HMGB1-mediated vascular disruptions and inhibited hyperpermeability in mice, and in vivo analyses revealed that KC1 and KC3 reduced sepsis-related mortality and tissue injury. Taken together, the present results suggest that KC1 and KC3 both reduced HMGB1 release and septic mortality and, thus, may be useful for the treatment of sepsis.
- Lee, Wonhwa,Yuseok,Lee, Changhun,Jeong, So Yeon,Lee, Jee-Hyun,Baek, Moon-Chang,Song, Gyu-Yong,Bae, Jong-Sup
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p. 260 - 268
(2019/03/04)
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- Copper-Catalyzed Perfluoroalkylation of Allyl Phosphates with Stable Perfluoroalkylzinc Reagents
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A general and practical method for copper-catalyzed cross-coupling of allyl phosphates with stable perfluoroalkylzinc reagents has been developed. The reaction proceeds under mild reaction conditions with high efficiency, good functional group tolerance, and high regio- A nd stereoselectivities and provides general, straightforward, and useful access to allyl-perfluoroalkyl compounds. Preliminary mechanistic studies reveal that the allyl copper intermediate may be involved in the catalytic cycle.
- Liu, Lihua,Bao, Xifei,Xiao, Hua,Li, Junlan,Ye, Feifan,Wang, Chaoqin,Cai, Qinhua,Fan, Shilu
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p. 423 - 434
(2019/01/08)
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- Vinylethylene Carbonates as α,β-Unsaturated Aldehyde Surrogates for Regioselective [3 + 3] Cycloaddition
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Herein, we report a novel stepwise addition-controlled ring size method, to access tetrahydropyrimidines through an operationally simple [3 + 3] cycloaddition of vinylethylene carbonates with triazinanes. Interestingly, we could also use this method for a [3 + 3] oxidative cycloaddition, which allows the facile synthesis of polysubstituted terphenyls under mild conditions. Mechanistic studies suggest that vinylethylene carbonates could generate α,β-unsaturated aldehydes as 3-carbon synthons for cycloaddition via a combination process of Pd-catalyzed decarboxylation and β-H elimination.
- Xu, Yi,Chen, Lu,Yang, Yu-Wen,Zhang, Zhiqiang,Yang, Weibo
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supporting information
p. 6674 - 6678
(2019/09/03)
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- Biocatalytic dynamic kinetic reductive resolution with ketoreductase from: Klebsiella pneumoniae: The asymmetric synthesis of functionalized tetrahydropyrans
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Ketoreductase from growing cells of Klebsiella pneumoniae (NBRC 3319) acts as an efficient reagent for converting racemic α-benzyl/cinnamyl substituted-β-ketoesters to the corresponding β-hydroxy esters with excellent yields and stereoselectivities (ee and de >99 %). The reactions described herein followed a biocatalytic dynamic kinetic reductive resolution (DKRR) pathway, which is reported for the first time with such substrates. It was found that the enzyme system can accept substituted mono-aryl rings with different electronic natures. In addition, it also accepts a substituted naphthyl ring and heteroaryl ring in the α-position of the parent β-ketoester. The synthesized enantiopure β-hydroxy esters were then synthetically manipulated to valuable tetrahydropyran building blocks.
- Barik, Rasmita,Halder, Joydev,Nanda, Samik
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supporting information
p. 8571 - 8588
(2019/10/02)
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- Boron-catalyzed CC functionalization of allyl alcohols
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Tris(pentafluorophenyl)borane-catalyzed CC bond functionalization of arylallyl alcohols using donor-acceptor carbenes is presented. The allylic hydroxyl group is found to assist the product formation by neighboring group participation providing a clue towards mechanistic understanding. This method can also be employed to effect homologation of allyl alcohols to homoallyl alcohols. Overall, this metal-free transformation presents a novel disconnection strategy towards carbon-carbon bond scission and formation.
- Rao, Santhosh,Kapanaiah, Raja,Prabhu, Kandikere Ramaiah
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supporting information
p. 1301 - 1306
(2019/10/28)
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- Structural Basis for Achieving GSK-3β Inhibition with High Potency, Selectivity, and Brain Exposure for Positron Emission Tomography Imaging and Drug Discovery
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Using structure-guided design, several cell based assays, and microdosed positron emission tomography (PET) imaging, we identified a series of highly potent, selective, and brain-penetrant oxazole-4-carboxamide-based inhibitors of glycogen synthase kinase-3 (GSK-3). An isotopologue of our first-generation lead, [3H]PF-367, demonstrates selective and specific target engagement in vitro, irrespective of the activation state. We discovered substantial ubiquitous GSK-3-specific radioligand binding in Tg2576 Alzheimer's disease (AD), suggesting application for these compounds in AD diagnosis and identified [11C]OCM-44 as our lead GSK-3 radiotracer, with optimized brain uptake by PET imaging in nonhuman primates. GSK-3β-isozyme selectivity was assessed to reveal OCM-51, the most potent (IC50 = 0.030 nM) and selective (>10-fold GSK-3β/GSK-3α) GSK-3β inhibitor known to date. Inhibition of CRMP2T514 and tau phosphorylation, as well as favorable therapeutic window against WNT/β-catenin signaling activation, was observed in cells.
- Bernard-Gauthier, Vadim,Mossine, Andrew V.,Knight, Ashley,Patnaik, Debasis,Zhao, Wen-Ning,Cheng, Chialin,Krishnan, Hema S.,Xuan, Lucius L.,Chindavong, Peter S.,Reis, Surya A.,Chen, Jinshan Michael,Shao, Xia,Stauff, Jenelle,Arteaga, Janna,Sherman, Phillip,Salem, Nicolas,Bonsall, David,Amaral, Brenda,Varlow, Cassis,Wells, Lisa,Martarello, Laurent,Patel, Shil,Liang, Steven H.,Kurumbail, Ravi G.,Haggarty, Stephen J.,Scott, Peter J. H.,Vasdev, Neil
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supporting information
p. 9600 - 9617
(2019/10/28)
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- Selective Hydroboration of Carboxylic Acids with a Homogeneous Manganese Catalyst
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Catalytic reduction of carboxylic acid to the corresponding alcohol is a challenging task of great importance for the production of a variety of value-added chemicals. Herein, a manganese-catalyzed chemoselective hydroboration of carboxylic acids has been developed with a high turnover number (>99?000) and turnover frequency (>2000 h-1) at 25 °C. This method displayed tolerance of electronically and sterically differentiated substrates with high chemoselectivity. Importantly, aliphatic long-chain fatty acids, including biomass-derived compounds, can efficiently be reduced. Mechanistic studies revealed that the reaction occurs through the formation of active manganese-hydride species via an insertion and bond metathesis type mechanism.
- Barman, Milan K.,Das, Kuhali,Maji, Biplab
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p. 1570 - 1579
(2019/01/30)
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- Pt/TiH2 Catalyst for Ionic Hydrogenation via Stored Hydrides in the Presence of Gaseous H2
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A Pt/TiH2 catalyst having hydrogen storage and release capability was investigated for selective hydrogenation of trans-cinnamaldehyde (CAL) to cinnamyl alcohol (COL) with gaseous dihydrogen. The catalytic behavior of this catalyst was significantly different from that of a reference Pt/TiO2 catalyst with respect to the product selectivity and the hydrogenation mechanism. The Pt/TiH2 catalyst showed a COL selectivity of 97% at a CAL conversion of 98%, which was ascribed to the function of a Pt crystallite-support boundary layer that caused the preferential adsorption of CAL with its carbonyl group. Furthermore, the carbonyl group was hydrogenated by hydride species (H+, H-) supplied from the support and the hydride species consumed were compensated from gaseous dihydrogen; hydrogen atoms were formed by ordinary homolytic cleavage on Pt and then these hydrogen atoms moved onto the surface of TiH2 and diffused into the bulk of the support, during which those simultaneously changed to hydride species (H+, H-) via electron transfer with titanium species and hydride vacancies therein. The surface and bulk diffusion of the hydrogen atoms from Pt to TiH2 support should be the dominant step rather than their addition to the carbonyl group of CAL (ordinary hydrogenation). That is, ionic hydrogenation occurs with Pt/TiH2 in the presence of gaseous dihydrogen.
- Wu, Qifan,Zhang, Chao,Arai, Masahiko,Zhang, Bin,Shi, Ruhui,Wu, Peixuan,Wang, Zhuangqing,Liu, Qiang,Liu, Ke,Lin, Weiwei,Cheng, Haiyang,Zhao, Fengyu
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p. 6425 - 6434
(2019/08/15)
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- PROCESS
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Process is disclosed for the hydrogenation of a compound comprising an α,β-unsaturated carbonyl group to form a compound comprising an allyl alcohol group, wherein the hydrogenation is carried out in the presence of a hydrogenation catalyst, hydrogen gas and an inorganic base in an aqueous solvent, wherein the hydrogenation catalyst is an iron-, ruthenium- or osmium-containing complex.
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Page/Page column 43
(2019/03/17)
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- Tris(pyrazolyl)borate Cobalt-Catalyzed Hydrogenation of C=O, C=C, and C=N Bonds: An Assistant Role of a Lewis Base
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The combination of tris(pyrazolyl)borate cobalt complexes and Lewis base is developed as an efficient catalyst precursor in the homogeneous hydrogenation. A broad substrate scope including carbonyls, alkenes, enamines, and imines is reduced with 60 atm of H2 at 60 °C. Mechanistic studies support the hydrogenation operates through a frustrated Lewis pair (FLP)-like reduction process. These results highlight the development of novel non-noble metal catalytic processes, when combined with the diverse small molecule activation chemistry associated with FLPs.
- Lin, Yang,Zhu, De-Ping,Du, Yi-Ran,Zhang, Rui,Zhang, Suo-Jiang,Xu, Bao-Hua
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supporting information
p. 2693 - 2698
(2019/04/25)
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- Development and Scale-up of Continuous Electrocatalytic Hydrogenation of Functionalized Nitro Arenes, Nitriles, and Unsaturated Aldehydes
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Electrolysis flow reactors based on the filter-press architecture of redox flow batteries have proven to be effective and scalable toward the production of commercially relevant, pharmaceutical quantities of anilines (>500 kg/year) from halogen-, hydroxyl-, and carbonyl-substituted nitroarenes. Turbulent flow through the carbon felts on which the catalysts were supported facilitated scaling toward production levels because it conferred on the reactors scale-independent, plug flow-like residence time distributions and high mass transfer coefficients. Equipping the cells with microreference electrodes made it possible to transfer reaction conditions first developed in batch systems to the continuous flow reactors. The catalysts prepared by incipient wetness impregnation of metal salts into lightly oxidized carbon felt supports were readily generalizable.
- Egbert, Jonathan D.,Thomsen, Edwin C.,O'Neill-Slawecki, Stacy A.,Mans, Douglas M.,Leitch, David C.,Edwards, Lee J.,Wade, Charles E.,Weber, Robert S.
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p. 1803 - 1812
(2019/08/15)
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- Homogeneous Hydrogenation with a Cobalt/Tetraphosphine Catalyst: A Superior Hydride Donor for Polar Double Bonds and N-Heteroarenes
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The development of catalysts based on earth abundant metals in place of noble metals is becoming a central topic of catalysis. We herein report a cobalt/tetraphosphine complex-catalyzed homogeneous hydrogenation of polar unsaturated compounds using an air- and moisture-stable and scalable precatalyst. By activation with potassium hydroxide, this cobalt system shows both high efficiency (up to 24 000 TON and 12 000 h-1 TOF) and excellent chemoselectivities with various aldehydes, ketones, imines, and even N-heteroarenes. The preference for 1,2-reduction over 1,4-reduction makes this method an efficient way to prepare allylic alcohols and amines. Meanwhile, efficient hydrogenation of the challenging N-heteroarenes is also furnished with excellent functional group tolerance. Mechanistic studies and control experiments demonstrated that a CoIH complex functions as a strong hydride donor in the catalytic cycle. Each cobalt intermediate on the catalytic cycle was characterized, and a plausible outer-sphere mechanism was proposed. Noteworthy, external inorganic base plays multiple roles in this reaction and functions in almost every step of the catalytic cycle.
- Duan, Ya-Nan,Du, Xiaoyong,Cui, Zhikai,Zeng, Yiqun,Liu, Yufeng,Yang, Tilong,Wen, Jialin,Zhang, Xumu
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supporting information
p. 20424 - 20433
(2019/12/27)
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