- Zwitterionic amidinates as effective ligands for platinum nanoparticle hydrogenation catalysts
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Ligand control of metal nanoparticles (MNPs) is rapidly gaining importance as ligands can stabilize the MNPs and regulate their catalytic properties. Herein we report the first example of Pt NPs ligated by imidazolium-amidinate ligands that bind strongly through the amidinate anion to the platinum surface atoms. The binding was established by15N NMR spectroscopy, a precedent for nitrogen ligands on MNPs, and XPS. Both monodentate and bidentate coordination modes were found. DFT showed a high bonding energy of up to -48 kcal mol-1 for bidentate bonding to two adjacent metal atoms, which decreased to -28 ± 4 kcal mol-1 for monodentate bonding in the absence of impediments by other ligands. While the surface is densely covered with ligands, both IR and13C MAS NMR spectra proved the adsorption of CO on the surface and thus the availability of sites for catalysis. A particle size dependent Knight shift was observed in the13C MAS NMR spectra for the atoms that coordinate to the surface, but for small particles, ～1.2 nm, it almost vanished, as theory for MNPs predicts; this had not been experimentally verified before. The Pt NPs were found to be catalysts for the hydrogenation of ketones and a notable ligand effect was observed in the hydrogenation of electron-poor carbonyl groups. The catalytic activity is influenced by remote electron donor/acceptor groups introduced in the aryl-N-substituents of the amidinates; p-anisyl groups on the ligand gave catalysts several times faster the ligand containing p-chlorophenyl groups.
- Martínez-Prieto,Cano,Márquez,Baquero,Tricard,Cusinato,Del Rosal,Poteau,Coppel,Philippot,Chaudret,Cámpora,Van Leeuwen
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- Heterogeneous selective hydrogenation of trans-4-phenyl-3-butene-2-one to allylic alcohol over modified Ir/SiO2 catalyst
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The heterogeneous selective hydrogenation of trans-4-phenyl-3-butene-2-one to allylic alcohol, catalyzed by Ir/SiO2 stabilized with phosphines and modified by cinchona alkaloids, was described herein. Under the optimized conditions, the chemoselectivity to α,β-unsaturated alcohol was more than 99% with enantioselectivity up to 46%.
- Jiang, He-Yan,Sun, Bin,Zheng, Xu-Xu,Chen, Hua
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- HYDROGEN TRANSFER REACTIONS FROM ALCOHOLS TO α,β-UNSATURATED KETONES: Cl, A VERY ACTIVE CATALYST PRECURSOR
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A high catalytic activity, with turnover up to 900 cycles/min, is displayed by Cl in hydrogen transfer reactions from propan-2-ol to α,β-unsaturated ketones in a weakly alkaline medium.
- Camus, A.,Mestroni, G.,Zassinovich, G.
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- First example of selective hydrogenation of unconstrained α,β-unsaturated ketone to α,β-unsaturated alcohol by molecular hydrogen
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Unprecedent hydrogenation of unhindered α,β-unsaturated ketones to unsaturated alcohols by molecular H2 on gold supported on Fe2O3 catalysts.
- Milone,Ingoglia,Tropeano,Neri,Galvagno
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Read Online
- Electrocatalytic Oxidative Hydrofunctionalization Reactions of Alkenes via Co(II/III/IV) Cycle
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Here we disclose a general Co(II/III/IV) electrocatalytic platform for alkene functionalization. Driven by electricity, a set of the oxidative hydrofunctionalization reactions via hydrogen atom transfer were demonstrated without the need for stochiometric chemical oxidants. The scope of the reactions encompasses hydroalkoxylation, hydroacyloxylation, hydroarylation, semipinacol rearrangement, and deallylation. Mechanistic studies and stereochemical evidence support an ECEC process involving an electrochemically generated organocobalt(IV) intermediate. This work presents an example of reactivity space expansion in electrocatalysis in the VB12-system by going beyond the common oxidation states of Co(I/II/III).
- Yang, Fan,Nie, Yi-Chen,Liu, Han-Yuan,Zhang, Lei,Mo, Fanyang,Zhu, Rong
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p. 2132 - 2137
(2022/02/10)
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- Discovery and Redesign of a Family VIII Carboxylesterase with High (S)-Selectivity toward Chiral sec-Alcohols
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Highly enantioselective lipase has been widely utilized in the preparation of versatile enantiopure chiral sec-alcohols through kinetic or dynamic kinetic resolution. Lipase is intrinsically (R)-selective, and it is difficult to obtain (S)-selective lipase. Recent crystal structures of a family VIII carboxylesterase have revealed that the spatial array of its catalytic triad is the mirror image of that of lipase but with a catalytic triad that is distinct from lipase. We, therefore, hypothesized that the family VIII carboxylesterase may exhibit (S)-enantioselectivity toward sec-alcohols similar to (S)-selective serine protease, whose catalytic triad is also spatially arrayed as its mirror image. In this study, a homologous enzyme (carboxylesterase from Proteobacteria bacterium SG_bin9, PBE) of a known family VIII carboxylesterase (pdb code: 4IVK) was prepared, which showed not only moderate (S)-selectivity toward sec-alcohols such as 3-butyn-2-ol and 1-phenylethyl alcohol but also (R)-selectivity toward particular sec-alcohols among the substrates explored. Furthermore, the (S)-selectivity of PBE has been significantly improved by rational redesign based on molecular modeling. Molecular modeling identified a binding pocket composed of Ser381, Ala383, and Arg408 for the methyl substituent of (R)-1-phenylethyl acetate and suggested that larger residues may increase the enantioselectivity by interfering with the binding of the slow-reacting enantiomer. As predicted, substituting Ser381with larger residues (Phe, Tyr, and Trp) significantly improved the (S)-selectivity of PBE toward all sec-alcohols explored, even the substrates toward which the wild-type PBE exhibits (R)-selectivity. For instance, the enantioselectivity toward 3-butyn-2-ol and 1-phenylethyl alcohol was improved from E = 5.5 and 36.1 to E = 2001 and 882, respectively, by single mutagenesis (S381F).
- Park, Areum,Park, Seongsoon
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p. 2397 - 2402
(2022/02/17)
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- Application of robust ketoreductase from Hansenula polymorpha for the reduction of carbonyl compounds
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Enzyme-catalysed asymmetric reduction of ketones is an attractive tool for the production of chiral building blocks or precursors for the synthesis of bioactive compounds. Expression of robust ketoreductase (KRED) from Hansenula polymorpha was upscaled and applied for the asymmetric reduction of 31 prochiral carbonyl compounds (aliphatic and aromatic ketones, diketones and β-keto esters) to the corresponding optically pure hydroxy compounds. Biotransformations were performed with the purified recombinant KRED together with NADP+ recycling glucose dehydrogenase (GDH, Bacillus megaterium), both overexpressed in Escherichia coli BL21(DE3). Maximum activity of KRED for biotransformation of ethyl-2-methylacetoacetate achieved by the high cell density cultivation was 2499.7 ± 234 U g–1DCW and 8.47 ± 0.40 U·mg–1E, respectively. The KRED from Hansenula polymorpha is a very versatile enzyme with broad substrate specificity and high activity towards carbonyl substrates with various structural features. Among the 36 carbonyl substrates screened in this study, the KRED showed activity with 31, with high enantioselectivity in most cases. With several ketones, the Hansenula polymorpha KRED catalysed preferentially the formation of the (R)-secondary alcohols, which is highly valued.
- Petrovi?ová, Tatiana,Gyuranová, Dominika,Pl?, Michal,Myrtollari, Kamela,Smonou, Ioulia,Rebro?, Martin
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- Novel non-metal catalyst for catalyzing asymmetric hydrogenation of ketone and alpha, beta-unsaturated ketone
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The invention discloses a novel non-metal catalyst for catalyzing asymmetric hydrogenation of ketone and alpha, beta-unsaturated ketone. The preparation method of a chiral alcohol compound shown as formula IV comprises the following step of: reacting a ketone compound shown as formula V with hydrogen under the catalysis of tri(4-hydrotetrafluorophenyl)boron and a chiral oxazoline compound to obtain the chiral alcohol compound shown as the formula IV; the preparation method of a chiral tetralone compound shown as formula VI comprises the following step of: under the catalysis of tri(4-hydrotetrafluorophenyl)boron and a chiral oxazoline compound, reacting an alpha, beta-unsaturated ketone compound shown as formula VII with hydrogen to obtain the chiral tetralone compound shown as the formula VI. The method has the advantages of easy synthesis of raw materials, mild reaction conditions, simple operation, high stereoselectivity and the like, the ee value of the product is up to 92%, and the yield is up to 99%.
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Paragraph 0126-0131
(2021/04/26)
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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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- Organometallic Synthesis of Bimetallic Cobalt-Rhodium Nanoparticles in Supported Ionic Liquid Phases (CoxRh100?x@SILP) as Catalysts for the Selective Hydrogenation of Multifunctional Aromatic Substrates
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The synthesis, characterization, and catalytic properties of bimetallic cobalt-rhodium nanoparticles of defined Co:Rh ratios immobilized in an imidazolium-based supported ionic liquid phase (CoxRh100?x@SILP) are described. Following an organometallic approach, precise control of the Co:Rh ratios is accomplished. Electron microscopy and X-ray absorption spectroscopy confirm the formation of small, well-dispersed, and homogeneously alloyed zero-valent bimetallic nanoparticles in all investigated materials. Benzylideneacetone and various bicyclic heteroaromatics are used as chemical probes to investigate the hydrogenation performances of the CoxRh100?x@SILP materials. The Co:Rh ratio of the nanoparticles is found to have a critical influence on observed activity and selectivity, with clear synergistic effects arising from the combination of the noble metal and its 3d congener. In particular, the ability of CoxRh100?x@SILP catalysts to hydrogenate 6-membered aromatic rings is found to experience a remarkable sharp switch in a narrow composition range between Co25Rh75 (full ring hydrogenation) and Co30Rh70 (no ring hydrogenation).
- Rengshausen, Simon,Van Stappen, Casey,Levin, Natalia,Tricard, Simon,Luska, Kylie L.,DeBeer, Serena,Chaudret, Bruno,Bordet, Alexis,Leitner, Walter
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- Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
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We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
- Topf, Christoph,Vielhaber, Thomas
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- Impact of the Difluoromethylene Group in the Organocatalyzed Acylative Kinetic Resolution of α,α-Difluorohydrins
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Due to the omnipresence of chiral organofluorine compounds in pharmaceutical, agrochemical, and material chemistry, the development of enantioselective methods for their preparation is highly desirable. In the present study, the enantioselective organocatalyzed acylation of α,α-difluorohydrins using a commercially available chiral isothiourea is reported through a kinetic resolution (KR) process. It reveals that the difluoromethylene moiety (C(sp3)F2) can serve as a directing group through electrostatic fluorine–cation interactions, greatly improving the enantioselectivity of the KR. In this context, a broad range of fluorinated alcohols such as valuable 4,4-difluoro-1,3-diols could be synthesized with exquisite enantiocontrol (typically >99:1 er). Turning to 2,2-difluoro-1,3-diols, we also demonstrated that aromatic and fluorinated groups were mutually compatible to provide the expected enantioenriched adducts with >99:1 er.
- Andrei, Daniela,Bressy, Cyril,Desrues, Titouan,Médebielle, Maurice,Merad, Jérémy,Parrain, Jean-Luc,Pons, Jean-Marc,Quintard, Adrien
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supporting information
p. 24924 - 24929
(2021/10/19)
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- Umpolung Strategy for Arene C?H Etherification Leading to Functionalized Chromanes Enabled by I(III) N-Ligated Hypervalent Iodine Reagents
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The direct formation of aryl C?O bonds via the intramolecular dehydrogenative coupling of a C?H bond and a pendant alcohol represents a powerful synthetic transformation. Herein, we report a method for intramolecular arene C?H etherification via an umpoled alcohol cyclization mediated by an I(III) N-HVI reagent. This approach provides access to functionalized chromane scaffolds from primary, secondary and tertiary alcohols via a cascade cyclization-iodonium salt formation, the latter providing a versatile functional handle for downstream derivatization. Computational studies support initial formation of an umpoled O-intermediate via I(III) ligand exchange, followed by competitive direct and spirocyclization/1,2-shift pathways. (Figure presented.).
- Mikhael, Myriam,Guo, Wentao,Tantillo, Dean J.,Wengryniuk, Sarah E.
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supporting information
p. 4867 - 4875
(2021/09/14)
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- Four-Coordinated Manganese(II) Disilyl Complexes for the Hydrosilylation of Aldehydes and Ketones with 1,1,3,3-Tetramethyldisiloxane
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The coordinatively unsaturated manganase(II) bis(supersilyl) complex Mn[Si(SiMe3)3]2(THF)2 (2) was synthesized in one step via the reaction of MnBr2 with two equivalents of KSi(SiMe3)3 in THF. Complex 2 acts as an effective precatalyst for the catalytic hydrosilylation of aldehydes and ketones with 1,1,3,3-tetramethyldisiloxane (TMDS). The catalytic efficiency can be improved by combining 2 and adamantyl isocyanide (CNAd). The stoichiometric reaction of 2 and two equivalents of CNAd led to the isolation of Mn[Si(SiMe3)3]2(CNAd)2 (3) in high yield. Complex 3 shows superior catalytic performance than 2 in the hydrosilylation of relatively unreactive ketones.
- Saito, Kyoka,Ito, Tatsuyoshi,Arata, Shogo,Sunada, Yusuke
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p. 1152 - 1156
(2020/12/18)
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- Cobalt-Catalyzed Radical Hydroamination of Alkenes with N-Fluorobenzenesulfonimides
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An efficient and general radical hydroamination of alkenes using Co(salen) as catalyst, N-fluorobenzenesulfonimide (NFSI) and its analogues as both nitrogen source and oxidant was successfully disclosed. A variety of alkenes, including aliphatic alkenes, styrenes, α, β-unsaturated esters, amides, acids, as well as enones, were all compatible to provide desired amination products. Mechanistic experiments suggest that the reaction underwent a metal-hydride-mediated hydrogen atom transfer (HAT) with alkene, followed by a pivotal catalyst controlled SN2-like pathway between in situ generated organocobalt(IV) species and nitrogen-based nucleophiles. Moreover, by virtue of modified chiral cobalt(II)-salen catalyst, an unprecedented asymmetric version was also achieved with good to excellent level of enantiocontrol. This novel asymmetric radical C?N bond construction opens a new door for the challenging asymmetric radical hydrofunctionalization.
- Lv, Guowei,Meng, Qi,Qin, Tao,Xiong, Tao,Zhang, Ge,Zhang, Qian
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supporting information
p. 25949 - 25957
(2021/11/01)
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- Nickel-Catalyzed Hydrodeoxygenation of Aryl Sulfamates with Alcohols as Mild Reducing Agents
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The nickel-catalyzed hydrodeoxygenation of aryl sulfamates has been developed with alcohols as mild reductants. A variety of functional groups and heterocycles were tolerated in this reaction system to give the desired products in high yields. In addition, the gram-scale process and stepwise cine-substitution were also achieved with high efficiency.
- Matsuo, Kasumi,Kuriyama, Masami,Yamamoto, Kosuke,Demizu, Yosuke,Nishida, Koyo,Onomura, Osamu
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p. 4449 - 4460
(2021/08/25)
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- Selective palladium nanoparticles-catalyzed hydrogenolysis of industrially targeted epoxides in water
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Palladium nanoparticles, with core sizes of ca. 2.5 nm, were easily synthesized by chemical reduction of Na2PdCl4 in the presence of hydroxyethylammonium salts and proved to be efficient for the selective hydrogenolysis of various aromatic, alkylphenyl, aliphatic epoxides in water as green solvent. Capping agents of the metal species were screened to define the most suitable micellar nanoreactors on two target substrates of industrial interest, epoxystyrene and 7,8-epoxy-2-methoxy-2,6-dimethyloctane. In our conditions, the hydrogenolysis of epoxystyrene proved to be pH-dependent, producing either the diol under acidic conditions, or the sweet-smelling 2-phenylethanol in the presence of a base. Promisingly, 7,8-epoxy-2-methoxy-2,6-dimethyloctane was completely and selectively hydrogenated into Florsantol, a sandalwood odorant at a multigram scale (40 g and up to 175g). A general mechanism for the palladium nanoparticles-catalyzed hydrogenolysis of terminal epoxides was proposed according to steric and electronic properties and finely corroborated with deuterium labelling experiments.
- Duval, Marion,Deboos, Victor,Hallonet, Agnès,Sagorin, Gilles,Denicourt-Nowicki, Audrey,Roucoux, Alain
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p. 261 - 268
(2021/03/22)
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- Tridentate nitrogen phosphine ligand containing arylamine NH as well as preparation method and application thereof
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The invention discloses a tridentate nitrogen phosphine ligand containing arylamine NH as well as a preparation method and application thereof, and belongs to the technical field of organic synthesis. The tridentate nitrogen phosphine ligand disclosed by the invention is the first case of tridentate nitrogen phosphine ligand containing not only a quinoline amine structure but also chiral ferrocene at present, a noble metal complex of the type of ligand shows good selectivity and extremely high catalytic activity in an asymmetric hydrogenation reaction, meanwhile, a cheap metal complex of the ligand can also show good selectivity and catalytic activity in the asymmetric hydrogenation reaction, and is very easy to modify in the aspects of electronic effect and space structure, so that the ligand has huge potential application value. A catalyst formed by the ligand and a transition metal complex can be used for catalyzing various reactions, can be used for synthesizing various drugs, and has important industrial application value.
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Paragraph 0095-0102; 0105-0109
(2021/06/26)
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- Reduction of α,β-unsaturated carbonyl compounds and 1,3-diketones in aqueous media, using a raney ni-al alloy
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The treatment of α,β-unsaturated carbonyl compounds and 1,3-diketones with Raney Ni-Al alloy in aqueous media yielded as major reaction products the corresponding saturated alcohols and/or the corresponding hydrocarbons, in a complete transformation of the starting material.
- Simion, Cristian,Mitoma, Yoshiharu,Katayama, Yumi,Simion, Alina Marieta
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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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- Samarium-based Grignard-type addition of organohalides to carbonyl compounds under catalysis of CuI
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Grignard-type additions were readily achieved under the mediation of CuI (10 mol%) and samarium (2 equiv.) by employing various organohalides,e.g.benzyl, aryl, heterocyclic and aliphatic halides (Cl, Br or I), and diverse carbonyl compounds (e.g.carbonic esters, carboxylic esters, acid anhydrides, acyl chlorides, ketones, aldehydes, propylene epoxides and formamides) to afford alcohols, ketones and aldehydes, respectively, with high efficiency and chemoselectivity, in which the organosamarium intermediate might be involved.
- Liu, Chen,Liu, Yongjun,Qi, Yan,Song, Bin,Wang, Liang,Xiao, Shuhuan
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supporting information
p. 6169 - 6172
(2021/06/30)
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- Pickering-Droplet-Derived MOF Microreactors for Continuous-Flow Biocatalysis with Size Selectivity
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Enzymatic microarchitectures with spatially controlled reactivity, engineered molecular sieving ability, favorable interior environment, and industrial productivity show great potential in synthetic protocellular systems and practical biotechnology, but their construction remains a significant challenge. Here, we proposed a Pickering emulsion interface-directed synthesis method to fabricate such a microreactor, in which a robust and defect-free MOF layer was grown around silica emulsifier stabilized droplet surfaces. The compartmentalized interior droplets can provide a biomimetic microenvironment to host free enzymes, while the outer MOF layer secludes active species from the surroundings and endows the microreactor with size-selective permeability. Impressively, the thus-designed enzymatic microreactor exhibited excellent size selectivity and long-term stability, as demonstrated by a 1000 h continuous-flow reaction, while affording completely equal enantioselectivities to the free enzyme counterpart. Moreover, the catalytic efficiency of such enzymatic microreactors was conveniently regulated through engineering of the type or thickness of the outer MOF layer or interior environments for the enzymes, highlighting their superior customized specialties. This study provides new opportunities in designing MOF-based artificial cellular microreactors for practical applications.
- Liang, Linfeng,Shi, Hu,Tian, Danping,Wang, Jun-Hao,Xue, Nan,Yang, Hengquan,Zhang, Xiaoming
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supporting information
p. 16641 - 16652
(2021/10/20)
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- Enantioselective direct, base-free hydrogenation of ketones by a manganese amido complex of a homochiral, unsymmetrical P-N-P′ ligand
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The use of manganese in homogeneous hydrogenation catalysis has been a recent focus in the pursuit of more environmentally benign base metal catalysts. It has great promise with its unique reactivity when coupled with metal-ligand cooperation of aminophosphine pincer ligands. Here, a manganese precatalyst Mn(P-N-P′)(CO)2, where P-N-P′ is the amido form of the ligand (S,S)-PPh2CHPhCHPhNHCH2CH2PiPr2, has been synthesized and used for base-free ketone hydrogenation. This catalyst shows exceptionally high enantioselectivity and good activity, with tolerance for base-sensitive substrates. NMR structural analysis of intermediates formed by the reaction of the amido complex with hydrogen under pressure identified a reactive hydride with an NOE contact with the syn amine proton. Computational analysis of the catalytic cycle reveals that the heterolytic splitting of dihydrogen across the MnN bond in the amido complex has a low barrier while the hydride transfer to the ketone is the turnover-limiting step. The pro-S transition state is found to be usually much lower in energy than the pro-R transition state depending on the ketone structure, consistent with the high (S) enantiomeric excess in the alcohol products. The energy to reach the transition state is higher for the distortion of the in-coming ketone than that of the hydride complex. In a one-to-one comparison with the similar iron catalyst FeH2(CO)(P-NH-P′), the manganese catalyst is found to have higher enantioselectivity, often over 95% ee, while the iron catalyst has higher activity and productivity. An explanation of these differences is provided on the basis of the more deformable iron hydride complex due to the smaller hydride ligands.
- Seo, Chris S. G.,Tsui, Brian T. H.,Gradiski, Matthew V.,Smith, Samantha A. M.,Morris, Robert H.
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p. 3153 - 3163
(2021/05/25)
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- Deep eutectic solvents as H2-sources for Ru(II)-catalyzed transfer hydrogenation of carbonyl compounds under mild conditions
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The employment of easily affordable ruthenium(II)-complexes as pre-catalysts in the transfer hydrogenation of carbonyl compounds in deep eutectic media is described for the first time. The eutectic mixture tetrabutylammonium bromide/formic acid = 1/1 (TBABr/HCOOH = 1/1) acts both as reaction medium and hydrogen source. The addition of a base is required for the process to occur. An extensive optimization of the reaction conditions has been carried out, in terms of catalyst loading, type of complexes, H2-donors, reaction temperature and time. The combination of the dimeric complex [RuCl(p-cymene)-μ-Cl]2 (0.01–0.05 eq.) and the ligand dppf (1,1′-ferrocenediyl-bis(diphenylphosphine)ferrocene) in 1/1 molar ratio has proven to be a suitable catalytic system for the reduction of several and diverse aldehydes and ketones to their corresponding alcohols under mild conditions (40–60 °C) in air, showing from moderate to excellent tolerability towards different functional groups (halogen, cyano, nitro, phenol). The reduction of imine compounds to their corresponding amine derivatives was also studied. In addition, the comparison between the results obtained in TBABr/HCOOH and in organic solvents suggests a non-innocent effect of the DES medium during the process.
- Cavallo, Marzia,Arnodo, Davide,Mannu, Alberto,Blangetti, Marco,Prandi, Cristina,Baratta, Walter,Baldino, Salvatore
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supporting information
(2021/02/22)
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- Synthetic ferripyrophyllite: Preparation, characterization and catalytic application
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Sheet silicates, also known as phyllosilicates, contain parallel sheets of tetrahedral silicate built up by [Si2O5]2- entities connected through intermediate metal-oxygen octahedral layers. The well-known minerals talc and pyrophyllite are belonging to this group based on magnesium and aluminium, respectively. Surprisingly, the ferric analogue rarely occurs in nature and is found in mixtures and conglomerates with other materials only. While partial incorporation of iron into pyrophyllites has been achieved, no synthetic protocol for purely iron-based pyrophyllite has been published yet. Here we report about the first artificial synthesis of ferripyrophyllite under exceptional mild conditions. A similar ultrathin two-dimensional (2D) nanosheet morphology is obtained as in talc or pyrophyllite but with iron(iii) as a central metal. The high surface material exhibits a remarkably high thermostability. It shows some catalytic activity in ammonia synthesis and can serve as catalyst support material for noble metal nanoparticles.
- Qiao, Yunxiang,Theyssen, Nils,Spliethoff, Bernd,Folke, Jan,Weidenthaler, Claudia,Schmidt, Wolfgang,Prieto, Gonzalo,Ochoa-Hernández, Cristina,Bill, Eckhard,Ye, Shengfa,Ruland, Holger,Schüth, Ferdi,Leitner, Walter
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supporting information
p. 850 - 857
(2021/02/03)
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- Homochiral Dodecanuclear Lanthanide "cage in Cage" for Enantioselective Separation
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It is extremely difficult to anticipate the structure and the stereochemistry of a complex, particularly when the ligand is flexible and the metal node adopts diverse coordination numbers. When trivalent lanthanides (LnIII) and enantiopure amino acid ligands are utilized as building blocks, self-assembly sometimes yields rare chiral polynuclear structures. In this study, an enantiopure carboxyl-functionalized amino acid-based ligand with C3 symmetry reacts with lanthanum cations to give a homochiral porous coordination cage, (Δ/λ)12-PCC-57. The dodecanuclear lanthanide cage has an unprecedented octahedral "cage-in-cage"framework. During the self-assembly, the chirality is transferred from the enantiopure ligand and fixed by the binuclear lanthanide cluster to give 12 metal centers that have either Δor λ homochiral stereochemistry. The cage exhibits excellent enantioselective separation of racemic alcohols, 2,3-dihydroquinazolinones, and multiple commercially available drugs. This finding exhibits a rare example of a multinuclear lanthanide complex with a dual-walled topology and homochirality. The highly ordered self-assembly and self-sorting of flexible amino acids and lanthanides shed light on the chiral transformation between different complicated artificial systems that mimic natural enzymes.
- Zhu, Chengfeng,Tang, Haitong,Yang, Keke,Fang, Yu,Wang, Kun-Yu,Xiao, Zhifeng,Wu, Xiang,Li, Yougui,Powell, Joshua A.,Zhou, Hong-Cai
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supporting information
p. 12560 - 12566
(2021/08/23)
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- C3 The symmetry contains a chiral ligand H3L of an amide bond. Preparation method and application
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The invention discloses C. 3 Chiral ligand H with symmetric amide bond3 L Relates to the technical field of material chemistry and chiral chemistry. The invention further provides the chiral ligand H. 3 L Preparation method and application thereof. The present invention has the advantage that the chiral ligand H of the present invention is a chiral ligand. 3 The L has a higher C. 3 The symmetric and flexible amide group enables coordination of the lanthanide metal ions with high coordination number and high oxygen affinity to be assembled into a novel structure-structure lanthanide metal chiral porous coordination cage. Moreover, the abundant chiral amide groups and amino acid residues on the ligand framework can be directly introduced into the synthesized lanthanide metal chiral porous coordination cage, thereby being beneficial to generating multiple chiral recognition sites and unique chiral microenvironments which mimic the biological enzyme binding pocket and further realize the purpose of high enantioselectivity separation of a series of chiral small molecule compounds.
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Paragraph 0092-0100
(2021/09/08)
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- Stereospecific Nickel-Catalyzed Reductive Cross-Coupling of Alkyl Tosylate and Allyl Alcohol Electrophiles
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The stereospecific cross-coupling of easily accessed electrophiles holds significant promise in the construction of C-C bonds. Herein, we report a nickel-catalyzed reductive coupling of allyl alcohols with chiral, nonracemic alkyl tosylates. This cross-coupling delivers valuable allylation products with high levels of stereospecificity across a range of substrates. The catalytic system consists of a simple nickel salt in conjunction with a commercially available reductant and importantly represents a rare example of a cross-coupling involving the C-O bonds of two electrophiles.
- Alexanian, Erik J.,Tercenio, Quentin D.
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supporting information
p. 7215 - 7219
(2021/09/22)
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- Cu-catalyzed cross-coupling of benzylboronic esters and epoxides
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A reaction between epoxides and benzylboronic acid pinacol esters is described. CuI was found to be an effective catalyst of this transformation upon activation of the benzylboronic ester with an alkyllithium reagent. The reaction was very efficient and a variety of substituted epoxides were found to be good substrates with good regioselectivity for substitution at the less substituted side of the epoxide. A reaction using an enantioenriched secondary benzylboronic ester was found to not be stereospecific.
- Gierszal, Sophia G.,Barker, Timothy J.
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supporting information
(2021/09/20)
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- Ni/Chiral Sodium Carboxylate Dual Catalyzed Asymmetric O-Propargylation
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A highly enantioselective O-propargylation catalyzed by combining a phosphine-nickel complex and an axially chiral sodium dicarboxylate has been developed. The transformation features mild reaction conditions, a broad substrate scope, and excellent functional group tolerance, offering an efficient approach to an array of enantioenriched O-propargyl hydroxylamines. Mechanistic studies support the presumed role of the chiral carboxylate as a counterion for nickel catalysis enabling the discovery of highly stereoselective transformations. The power of this reaction is illustrated by its application in the asymmetric total synthesis of potent firefly luciferase inhibitors and (S)-dihydroyashabushiketol.
- Chang, Xihao,Guo, Chang,Peng, Lingzi,Xu, Xianghong
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supporting information
p. 21048 - 21055
(2021/12/14)
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- Deracemization and Stereoinversion of Alcohols Using Two Mutants of Secondary Alcohol Dehydrogenase from Thermoanaerobacter pseudoethanolicus
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We developed a one-pot sequential two-step deracemization approach to chiral alcohols using two mutants of Thermoanaerobacter pseudoethanolicus secondary alcohol dehydrogenase (TeSADH). This approach relies on consecutive non-stereospecific oxidation of alcohols and stereoselective reduction of their prochiral ketones using two mutants of TeSADH with poor and good stereoselectivities, respectively. More specifically, W110G TeSADH enables a non-stereospecific oxidation of alcohol racemates to their corresponding prochiral ketones, followed by W110V TeSADH-catalyzed stereoselective reduction of the resultant ketone intermediates to enantiopure (S)-configured alcohols in up to > 99 percent enantiomeric excess. A heat treatment after the oxidation step was required to avoid the interference of the marginally stereoselective W110G TeSADH in the reduction step; this heat treatment was eliminated by using sol-gel encapsulated W110G TeSADH in the oxidation step. Moreover, this bi-enzymatic approach was implemented in the stereoinversion of (R)-configured alcohols, and (S)-configured alcohols with up to > 99 percent enantiomeric excess were obtained by this Mitsunobu-like stereoinversion reaction.
- Hamdan, Samir M.,Musa, Musa M.,Nafiu, Sodiq A.,Takahashi, Etsuko,Takahashi, Masateru
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- A Simple Biosystem for the High-Yielding Cascade Conversion of Racemic Alcohols to Enantiopure Amines
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The amination of racemic alcohols to produce enantiopure amines is an important green chemistry reaction for pharmaceutical manufacturing, requiring simple and efficient solutions. Herein, we report the development of a cascade biotransformation to aminate racemic alcohols. This cascade utilizes an ambidextrous alcohol dehydrogenase (ADH) to oxidize a racemic alcohol, an enantioselective transaminase (TA) to convert the ketone intermediate to chiral amine, and isopropylamine to recycle PMP and NAD+ cofactors via the reversed cascade reactions. The concept was proven by using an ambidextrous CpSADH-W286A engineered from (S)-enantioselective CpSADH as the first example of evolving ambidextrous ADHs, an enantioselective BmTA, and isopropylamine. A biosystem containing isopropylamine and E. coli (CpSADH-W286A/BmTA) expressing the two enzymes was developed for the amination of racemic alcohols to produce eight useful and high-value (S)-amines in 72–99 % yield and 98–99 % ee, providing with a simple and practical solution to this type of reaction.
- Li, Zhi,Tian, Kaiyuan
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supporting information
p. 21745 - 21751
(2020/09/21)
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- Boron containing chiral Schiff bases: Synthesis and catalytic activity in asymmetric transfer hydrogenation (ATH) of ketones
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Asymmetric Transfer Hydrogenation (ATH) has been an attractive way for the reduction of ketones to chiral alcohols. A great number of novel and valuable synthetic pathways have been achived by the combination usage of organometallic and coordination chemistry for the production of important class of compounds and particularly optically active molecules. For this aim, four boron containing Schiff bases were synthesized by the reaction of 4-formylphenylboronic acid with chiral amines. The boron containing structures have been found as stable compounds due to the presence of covalent B–O bonds and thus could be handled in laboratory environment. They were characterized by 1H NMR and FT-IR spectroscopy and elemental analysis and they were used as catalyst in the transfer hydrogenation of ketones to the related alcohol derivatives with high conversions (up to 99%) and low enantioselectivities (up to 22% ee).
- Pa?a, Salih,Arslan, Nevin,Meri??, Nermin,Kayan, Cezmi,Bingül, Murat,Durap, Feyyaz,Aydemir, Murat
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- Enantioselective transfer hydrogenation of pro-chiral ketones catalyzed by novel ruthenium and iridium complexes of well-designed phosphinite ligand
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The interaction of [Ru(η6-arene)(μ-Cl)Cl]2 and Ir(η5-C5Me5)(μ-Cl)Cl]2 with a new Ionic Liquid-based phosphinite ligand, [(Ph2PO)-C6H9N2Ph]Cl, (2) gave [Ru((Ph2PO)-C6H9N2Ph)(η6-p-cymene)Cl2]Cl (3), [Ru((Ph2PO)-C6H9N2Ph)(benzene)Cl2]Cl (4) and [Ir((Ph2PO)-C6H9N2Ph)(C5Me5)Cl2]Cl (5), complexes. All the compounds were characterized by a combination of multinuclear NMR and IR spectroscopy as well as elemental analysis. Furthermore, the Ru(II) and Ir(III) catalysts were applied to asymmetric transfer hydrogenation of acetophenone derivatives using 2-propanol as a hydrogen source. The results showed that the corresponding alcohols could be obtained with good activity (up to 55% ee and 99% conversion) under mild conditions. Notably, [Ir((Ph2PO)-C6H9N2Ph)(C5Me5)Cl2]Cl (5) is more active than the other analogous complexes in the transfer hydrogenation (up to 81% ee).
- Arslan, Nevin
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p. 628 - 637
(2020/01/02)
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- Chiral Imidazo[1,5- a]pyridine-Oxazolines: A Versatile Family of NHC Ligands for the Highly Enantioselective Hydrosilylation of Ketones
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Herein we report the synthesis and application of a versatile class of N-heterocyclic carbene ligands based on an imidazo[1,5-a]pyridine-3-ylidine backbone that is fused to a chiral oxazoline auxiliary. The key step in the synthesis of these ligands involves the installation of the oxazoline functionality via a microwave-assisted condensation of a cyano-azolium salt with a wide variety of 2-amino alcohols. The resulting chiral bidentate NHC-oxazoline ligands form stable complexes with rhodium(I) that are efficient catalysts for the enantioselective hydrosilylation of structurally diverse ketones. The corresponding secondary alcohols are isolated in good yields (typically >90%) with good to excellent enantioselectivities (80-93% ee). The reported hydrosilylation occurs at ambient temperatures (40 °C), with excellent functional group tolerability. Even ketones bearing heterocyclic substituents (e.g., pyridine or thiophene) or complex organic architectures are hydrosilylated efficiently, which is discussed further in this report.
- Chinna Ayya Swamy,Varenikov, Andrii,Ruiter, Graham De
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supporting information
p. 247 - 257
(2020/02/04)
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- Copper(I) Diphosphine Bifluoride Complexes as Efficient Preactivated Catalysts for Nucleophilic Addition on Unsaturated Functional Groups
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Herein we report the synthesis of a family of copper(I) diphosphine bifluoride complexes, their characterization, and their use as efficient preactivated catalysts for nucleophilic copper addition of pronucleophiles on unsaturations. Their use as mechanistic probes is also highlighted by the identification of two copper deuterides.
- Rasson, Corentin,Riant, Olivier
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supporting information
p. 835 - 840
(2020/02/13)
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- Asymmetric Hydrogenation of Ketones and Enones with Chiral Lewis Base Derived Frustrated Lewis Pairs
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The concept of frustrated Lewis pairs (FLPs) has been widely applied in various research areas, and metal-free hydrogenation undoubtedly belongs to the most significant and successful ones. In the past decade, great efforts have been devoted to the synthesis of chiral boron Lewis acids. In a sharp contrast, chiral Lewis base derived FLPs have rarely been disclosed for the asymmetric hydrogenation. In this work, a novel type of chiral FLP was developed by simple combination of chiral oxazoline Lewis bases with achiral boron Lewis acids, thus providing a promising new direction for the development of chiral FLPs in the future. These chiral FLPs proved to be highly effective for the asymmetric hydrogenation of ketones, enones, and chromones, giving the corresponding products in high yields with up to 95 % ee. Mechanistic studies suggest that the hydrogen transfer to simple ketones likely proceeds in a concerted manner.
- Du, Haifeng,Feng, Xiangqing,Gao, Bochao,Meng, Wei
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supporting information
p. 4498 - 4504
(2020/02/05)
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- Iridium-Catalyzed Enantioselective Transfer Hydrogenation of Ketones Controlled by Alcohol Hydrogen-Bonding and sp3-C?H Noncovalent Interactions
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Iridium-catalyzed enantioselective transfer hydrogenation of ketones with formic acid was developed using a prolinol-phosphine chiral ligand. Cooperative action of the iridium atom and the ligand through alcohol-alkoxide interconversion is crucial to facilitate the transfer hydrogenation. Various ketones including alkyl aryl ketones, ketoesters, and an aryl heteroaryl ketone were competent substrates. An attractive feature of this catalysis is efficient discrimination between the alkyl and aryl substituents of the ketones, promoting hydrogenation with the identical sense of enantioselection regardless of steric demand of the alkyl substituent and thus resulting in a rare case of highly enantioselective transfer hydrogenation of tert-alkyl aryl ketones. Quantum chemical calculations revealed that the sp3-C?H/π interaction between an sp3-C?H bond of the prolinol-phosphine ligand and the aryl substituent of the ketone is crucial for the enantioselection in combination with O?H???O/sp3-C?H???O two-point hydrogen-bonding between the chiral ligand and carbonyl group. (Figure presented.).
- Murayama, Hiroaki,Heike, Yoshito,Higashida, Kosuke,Shimizu, Yohei,Yodsin, Nuttapon,Wongnongwa, Yutthana,Jungsuttiwong, Siriporn,Mori, Seiji,Sawamura, Masaya
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supporting information
p. 4655 - 4661
(2020/07/13)
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- Asymmetric Catalytic Meerwein-Ponndorf-Verley Reduction of Ketones with Aluminum(III)-VANOL Catalysts
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We report herein an efficient aluminum-catalyzed asymmetric MPV reduction of ketones with broad substrate scope and excellent yields and enantiomeric inductions. A variety of aromatic (both electron-poor and electron-rich) and aliphatic ketones were converted to chiral alcohols in good yields with high enantioselectivities (26 examples, 70-98percent yield and 82-99percent ee). This method operates under mild conditions (-10 °C) and low catalyst loading (1-5 mol percent). Furthermore, this process is catalyzed by the earth-abundant main-group element aluminum and employs 2-propanol as the hydride source.
- Guan, Yong,Mohammadlou, Aliakbar,Staples, Richard,Sullivan, Ryan P.,Wulff, William D.,Yin, Xiaopeng,Zheng, Li
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p. 7188 - 7194
(2020/07/21)
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- P-chirogenic Trost ligands mediated asymmetric hydrogenation of simple ketones
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Herein, we report a highly active catalyst system consisting of (Rc,Rc,Rp,Rp)-P-chirogenic Trost ligand and [Ru(C6H6)Cl2]2 for asymmetric hydrogenation of simple ketones, affording the corresponding optically active alcohols in moderate enantioselectivity. A synergetic effect between P- and C-chirogenic centers of the P-chirogenic Trost ligands was observed in this asymmetric hydrogenation process.
- Du, Peng,Liu, Yan-Lan,Lu, Xiao-Bing
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supporting information
(2020/09/22)
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- Selective Cross-Dehydrogenative C(sp3)-H Arylation with Arenes
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Selective C(sp3)-C(sp2) bond construction is of central interest in chemical synthesis. Despite the success of classic cross-coupling reactions, the cross-dehydrogenative coupling between inert C(sp3)-H and C(sp2)-H bonds represents an attractive alternative toward new C(sp3)-C(sp2) bonds. Herein, we establish a selective inter-and intramolecular C(sp3)-H arylation of alcohols with nondirected arenes that thereby provides a general pathway to access a wide range of β-arylated alcohols, including tetrahydronaphthalen-2-ols and benzopyran-3-ols, with high to excellent chemo-and regioselectivity.
- Hao, Hong-Yan,Mao, Yang-Jie,Xu, Zhen-Yuan,Lou, Shao-Jie,Xu, Dan-Qian
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supporting information
p. 2396 - 2402
(2020/03/13)
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- Efficient Transfer Hydrogenation of Ketones Catalyzed by a Phosphine-Free Cobalt-NHC Complex
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A simple phosphine-free cobalt-NHC pincer complex has been synthesized and utilized for the transfer hydrogenation of ketones with 2-propanol as hydrogen donor. A broad range of ketones varying from aromatic, aliphatic and heterocyclic were effectively reduced to their corresponding alcohols in moderate to excellent yields with good tolerance of functional groups.
- Ibrahim, Jessica Juweriah,Reddy, C. Bal,Fang, Xiaolong,Yang, Yong
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p. 4429 - 4432
(2020/07/04)
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- Transfer Hydrogenation of Ketones and Imines with Methanol under Base-Free Conditions Catalyzed by an Anionic Metal-Ligand Bifunctional Iridium Catalyst
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An anionic iridium complex [Cp*Ir(2,2′-bpyO)(OH)][Na] was found to be a general and highly efficient catalyst for transfer hydrogenation of ketones and imines with methanol under base-free conditions. Readily reducible or labile substituents, such as nitro, cyano, and ester groups, were tolerated under present reaction conditions. Notably, this study exhibits the unique potential of anionic metal-ligand bifunctional iridium catalysts for transfer hydrogenation with methanol as a hydrogen source.
- Han, Xingyou,Li, Feng,Liu, Peng,Wang, Rongzhou,Xu, Jing
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p. 2242 - 2249
(2020/03/13)
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- Transfer hydrogenation of aldehydes and ketones catalyzed using an aminophosphinite POCNHpincer complex of Ni(ii)
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The aminophosphinite pincer complex (POCNH)NiBr was found to effectively catalyze the transfer hydrogenation of aldehydes and ketones with 2-propanol and KOtBu as a base, presenting a rare example of bifunctional nickel transfer hydrogenation catalysts. The transfer hydrogenation of aldehydes and ketones was found to be selective, tolerating a wide range of other functional groups, including those prone to reduction, such as esters, amides, alkenes, pyridines, and nitriles. The reactions were suggested to proceedviathe metal-ligand cooperative mechanism with an intermediacy of an amido (POCN)NiIIspecies.
- ?ztop?u, ?zgür,Hayrapetyan, Davit,Khalimon, Andrey Y.,Lyssenko, Konstantin A.,Segizbayev, Medet,Shakhman, Dinmukhamed
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supporting information
p. 11950 - 11957
(2020/09/21)
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- Production of enantiomerically enriched chiral carbinols using whole-cell biocatalyst
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Biocatalytic asymmetric reduction of ketone is an efficient method for the production of chiral carbinols. The study indicates selective bioreduction of different ketones (1–8) to their respective (R)-alcohols (1a–8a) in low to high selectivity (0- >99%) with good yields (11–96%). In this work, whole-cell of Lactobacillus kefiri P2 catalysed enantioselective reduction of various prochiral ketones was investigated. (R)-4-Phenyl-2-butanol 2a, which is used as a precursor to antihypertensive agents and spasmolytics (anti-epileptic agents), was obtained using L kefiri P2 in 99% conversion and 91% enantiomeric excess (ee). Moreover, bioreduction of 2-methyl-1-phenylpropan-1-one substrate 8, containing a branched alkyl chain and difficult to asymmetric reduction with chemical catalysts as an enantioselective, to (R)-2-methyl-1-phenylpropan-1-ol (8a) in enantiomerically pure form was carried out in excellent yield (96%). The gram-scale production was carried out, and 9.70 g of (R)-2-methyl-1-phenylpropan-1-ol (8a) in enantiomerically pure form was obtained in 96% yield. Also especially, the yield and gram scale of (R)-2-methyl-1-phenylpropan-1-ol (8a) synthesised through catalytic asymmetric reduction using the biocatalyst was the highest report so far. The efficiency of L kefiri P2 for the conversion of the substrates and ee of products were markedly influenced by the steric factors of the substrates. This is a cheap, clean and eco-friendly process for production of chiral carbinols compared to chemical processes.
- ?ahin, Engin,Bayda?, Yasemin,Kalay, Erbay
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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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- Chemoselective Oxidation of p-Methoxybenzyl Ethers by an Electronically Tuned Nitroxyl Radical Catalyst
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The oxidation of p-methoxy benzyl (PMB) ethers was achieved using nitroxyl radical catalyst 1, which contains electron-withdrawing ester groups adjacent to the nitroxyl group. The oxidative deprotection of the PMB moieties on the hydroxy groups was observed upon treatment of 1 with 1 equiv of the co-oxidant phenyl iodonium bis(trifluoroacetate) (PIFA). The corresponding carbonyl compounds were obtained by treating the PMB-protected alcohols with 1 and an excess of PIFA.
- Hamada, Shohei,Sugimoto, Koichi,Elboray, Elghareeb E.,Kawabata, Takeo,Furuta, Takumi
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supporting information
p. 5486 - 5490
(2020/07/24)
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- Reduction of α,β-Unsaturated carbonyl compounds and 1,3-Diketones in aqueous media, using a raney ni-al alloy
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The treatment of α,β-unsaturated carbonyl compounds and 1,3-diketones with Raney Ni-Al alloy in aqueous media yielded as major reaction products the corresponding saturated alcohols and/or the corresponding hydrocarbons, in a complete transformation of the starting material.
- Katayama, Yumi,Mitoma, Yoshiharu,Simion, Alina Marieta,Simion, Cristian
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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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- Highly activity asymmetric hydrogenation of enones catalyzed by iridium complexes with chiral diamines and achiral phosphines
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A selective asymmetric hydrogenation of enones has been well established by using an iridium complex composed of cheap phosphine ligands and cinchona alkaloids derivatives as catalyst. A wide range of allylic alcohol products could be obtained in high chemoselectivities (up to 99.6%), enantioselectivities (70.1% ee) and high activities (up to 3.64 × 104(1/h) TOF). This catalytic system opens a new way of selective asymmetric hydrogenation and the method can be of practical value.
- Chen, Hua,Gao, Xiuli,Jiang, Jian,Li, Chun,Li, Li,Lu, Xunhua,Wang, Mengna,Zhang, Lin,Zhang, Ling
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- Chelate ring size effects of Ir(P,N,N) complexes: Chemoselectivity switch in the asymmetric hydrogenation of α,β-unsaturated ketones
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A novel, highly modular approach has been developed for the synthesis of new chiral P,N,N ligands with the general formula Ph2P(CH3)CH(CH2)mCH(CH3)NHCH2CH2(CH2)nN(CH3)2 and Ph2P(CH3)CHCH2CH(CH3)NHCH2(CH2)n-2-Py (m, n = 0, 1). The systematic variation of their P–N and N–N backbone led to the conclusion that the activity, chemo- and enantioselectivity in the hydrogenation of α,β-unsaturated ketones are highly dependent on the combination of the two bridge lengths. It has been found that a minor change in the ligand's structure, i. e. varying the value of m from 1 to 0, can switch the chemoselectivity of the reaction, from 80percent C[dbnd]O to 97percent C[dbnd]C selectivity.
- Bényei, Attila C.,Bakos, József,Császár, Zsófia,Farkas, Gergely,Szabó, Eszter Z.
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- Synthesis of cis-1,2-diol-type chiral ligands and their dioxaborinane derivatives: Application for the asymmetric transfer hydrogenation of various ketones and biological evaluation
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Two cis-1,2-diol-type chiral ligands (T1 and T2) and their tri-coordinated chiral dioxaborinane (T(1–2)B(1–2)) and four-coordinated chiral dioxaborinane adducts with 4-tert-butyl pyridine sustained by N → B dati
- Kilic, Ahmet,Balci, Tu?ba Ersayan,Arslan, Nevin,Aydemir, Murat,Durap, Feyyaz,Okumu?, Veysi,Tekin, Recep
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- Ruthenium [NNN] and [NCN]-type pincer complexes with phosphine coligands: synthesis, structures and catalytic applications
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A series of ruthenium [NNN]- or [NCN]-type complexes (3–7) bearing PPh3 ancillary ligands have been synthesized from pyridine- or phenylene-bridged bis(triazoles) 1 and 2. In the case of [NNN]-pincer complex 3, an unusual and unexpected cis-orientation adopted by two sterically demanding PPh3 ligands was observed, and such configuration proved to be unchanged in solution for a long time. By contrast and as expected, the two phosphines are found to be trans to each other in the case of [NCN]-type pincer complex 4, but an oxidation of RuII center to RuIII occurred. Complex cis-3 underwent ligand exchanges leading to the formations of diphosphine derivatives 5 and 6. As a representative, cis-3 was treated with the base in isopropanol affording a mixture of Ru–hydrido complexes with various phosphine binding modes, one of which (trans-7) bearing two trans-standing phosphines has been successfully isolated and fully characterized. The catalytic performances of all newly synthesized Ru complexes have been examined and compared in transfer hydrogenations of ketones and enones, in which mono-phosphine complexes proved to be significantly superior to their diphosphine counterparts. The catalytic process proved to involve Ru–H key intermediates, but the trans-oriented Ru–H species is unlikely to be the main catalytic contributor. In particular, the best performer cis-3 exhibits high chemoselectivity in certain cases catalyzing α,β-unsaturated ketones, whose behavior is quite different compared to most precedents.
- Zhang, Bo,Wang, Haiying,Yan, Xuechao,Duan, Yu-Ai,Guo, Shuai,Luo, Fei-Xian
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- Catalytic Activity of a Zr MOF Containing POCOP-Pd Pincer Complexes
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A metal-organic framework assembled from POCOP-Pd pincer complex metallolinkers (1-PdBF4, Zr6O4(OH)4(L-PdMeCN)3(BF4)3, L = (2,6-(OPAr2)2C6H3, Ar = p-C6H4CO2-) has been generated via postsynthetic oxidative I-/BF4- ligand exchange with NOBF4. 1-PdBF4 catalyzes a range of organic transformations, including transfer hydrogenation of unsaturated organic substrates, terminal alkyne hydration, and intramolecular hydroarylation of alkynes. The homogeneous analogue, tBu4POCOP-PdBF4, shows poor catalytic activity for transfer hydrogenation and alkyne hydration and decomposes under the catalytic reaction conditions. Solubility limitations and catalyst deactivation pathways observed for the homogeneous pincer complex propound the advantages of using porous solid supports to immobilize organometallic species.
- Kassie, Abebu A.,Wade, Casey R.
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p. 2214 - 2221
(2020/07/06)
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