- 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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- Dual utility of a single diphosphine-ruthenium complex: A precursor for new complexes and, a pre-catalyst for transfer-hydrogenation and Oppenauer oxidation
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The diphosphine-ruthenium complex, [Ru(dppbz)(CO)2Cl2] (dppbz = 1,2-bis(diphenylphosphino)benzene), where the two carbonyls are mutually cis and the two chlorides are trans, has been found to serve as an efficient precursor for the synthesis of new complexes. In [Ru(dppbz)(CO)2Cl2] one of the two carbonyls undergoes facile displacement by neutral monodentate ligands (L) to afford complexes of the type [Ru(dppbz)(CO)(L)Cl2] (L = acetonitrile, 4-picoline and dimethyl sulfoxide). Both the carbonyls in [Ru(dppbz)(CO)2Cl2] are displaced on reaction with another equivalent of dppbz to afford [Ru(dppbz)2Cl2]. The two carbonyls and the two chlorides in [Ru(dppbz)(CO)2Cl2] could be displaced together by chelating mono-anionic bidentate ligands, viz. anions derived from 8-hydroxyquinoline (Hq) and 2-picolinic acid (Hpic) via loss of a proton, to afford the mixed-tris complexes [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], respectively. The molecular structures of four selected complexes, viz. [Ru(dppbz)(CO)(dmso)Cl2], [Ru(dppbz)2Cl2], [Ru(dppbz)(q)2] and [Ru(dppbz)(pic)2], have been determined by X-ray crystallography. In dichloromethane solution, all the complexes show intense absorptions in the visible and ultraviolet regions. Cyclic voltammetry on the complexes shows redox responses within 0.71 to -1.24 V vs. SCE. [Ru(dppbz)(CO)2Cl2] has been found to serve as an excellent pre-catalyst for catalytic transfer-hydrogenation and Oppenauer oxidation.
- Mukherjee, Aparajita,Bhattacharya, Samaresh
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p. 15617 - 15631
(2021/05/19)
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- An air-tolerant polymer gel-immobilized iridium photocatalyst with pumping recyclability properties
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A novel methacrylate-based cross-linked polymer gel bearing an iridium photocatalyst showed air tolerance and pumping recyclability features through its tunable swelling and deswelling ability. The photocatalytic activity of the polymer gel was demonstrated through an E-to-Z isomerisation reaction and in an azide-alkene [2+3] cycloaddition.
- Abramov, Alex,Díaz Díaz, David,Maiti, Binoy,Reiser, Oliver
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supporting information
p. 7762 - 7765
(2021/08/13)
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- Ambient-pressure highly active hydrogenation of ketones and aldehydes catalyzed by a metal-ligand bifunctional iridium catalyst under base-free conditions in water
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A green, efficient, and high active catalytic system for the hydrogenation of ketones and aldehydes to produce corresponding alcohols under atmospheric-pressure H2 gas and ambient temperature conditions was developed by a water-soluble metal–ligand bifunctional catalyst [Cp*Ir(2,2′-bpyO)(OH)][Na] in water without addition of a base. The catalyst exhibited high activity for the hydrogenation of ketones and aldehydes. Furthermore, it was worth noting that many readily reducible or labile functional groups in the same molecule, such as cyan, nitro, and ester groups, remained unchanged. Interestingly, the unsaturated aldehydes can be also selectively hydrogenated to give corresponding unsaturated alcohols with remaining C=C bond in good yields. In addition, this reaction could be extended to gram levels and has a large potential of wide application in future industrial.
- Wang, Rongzhou,Yue, Yuancheng,Qi, Jipeng,Liu, Shiyuan,Song, Ao,Zhuo, Shuping,Xing, Ling-Bao
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- Method for synthesizing primary alcohol in water phase
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The invention discloses a method for synthesizing primary alcohol in a water phase. The method comprises the following steps: taking aldehyde as a raw material, selecting water as a solvent, and carrying out catalytic hydrogenation reaction on the aldehyde in the presence of a water-soluble catalyst to obtain the primary alcohol, wherein the catalyst is a metal iridium complex [Cp*Ir(2,2'-bpyO)(OH)][Na]. Water is used as the solvent, so that the use of an organic solvent is avoided, and the method is more environment-friendly; the reaction is carried out at relatively low temperature and normal pressure, and the reaction conditions are mild; alkali is not needed in the reaction, so that generation of byproducts is avoided; and the conversion rate of the raw materials is high, and the yield of the obtained product is high. The method not only has academic research value, but also has a certain industrialization prospect.
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Paragraph 0030-0031
(2021/07/14)
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- Application of bis(phosphinite) pincer nickel complexes to the catalytic hydrosilylation of aldehydes
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A series of bis(phosphinite) (POCOP) pincer ligated nickel complexes, [2,6-(tBu2PO)2C6H3]NiX (X = SH, 1; SCH2Ph, 2; SPh, 3; NCS, 4; N3, 5), were used to catalyse the hydrosilylation of aldehydes. It was found that both complexes 1 and 2 are active in catalysing the hydrosilylation of aldehydes with phenylsilane and complex 1 is comparatively more active. The expected alcohols were isolated in good to excellent yields after basic hydrolysis of the resultant hydrosilylation products. However, no reaction was observed when complex 3 or 4 or 5 was used as the catalyst. The results are consistent with complexes 1 and 2 serving as catalyst precursors, which generate the corresponding nickel hydride complex [2,6-(tBu2PO)2C6H3]NiH in situ, and the nickel hydride complex is the active species that catalyses this hydrosilylation process. The in situ generation of the nickel hydride species was supported by both experimental results and DFT calculation.
- Chang, Jiarui,Fang, Fei,Tu, Chenhao,Zhang, Jie,Ma, Nana,Chen, Xuenian
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- KB3H8: An environment-friendly reagent for the selective reduction of aldehydes and ketones to alcohols
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Selective reduction of aldehydes and ketones to their corresponding alcohols with KB3H8, an air- and moisture-stable, nontoxic, and easy-to-handle reagent, in water and THF has been explored under an air atmosphere for the first time. Control experiments illustrated the good selectivity of KB3H8 over NaBH4 for the reduction of 4-acetylbenzaldehyde and aromatic keto esters. This journal is
- Li, Xinying,Mi, Tongge,Guo, Wenjing,Ruan, Zhongrui,Guo, Yu,Ma, Yan-Na,Chen, Xuenian
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supporting information
p. 12776 - 12779
(2021/12/10)
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- Generation of Oxidoreductases with Dual Alcohol Dehydrogenase and Amine Dehydrogenase Activity
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The l-lysine-?-dehydrogenase (LysEDH) from Geobacillus stearothermophilus naturally catalyzes the oxidative deamination of the ?-amino group of l-lysine. We previously engineered this enzyme to create amine dehydrogenase (AmDH) variants that possess a new hydrophobic cavity in their active site such that aromatic ketones can bind and be converted into α-chiral amines with excellent enantioselectivity. We also recently observed that LysEDH was capable of reducing aromatic aldehydes into primary alcohols. Herein, we harnessed the promiscuous alcohol dehydrogenase (ADH) activity of LysEDH to create new variants that exhibited enhanced catalytic activity for the reduction of substituted benzaldehydes and arylaliphatic aldehydes to primary alcohols. Notably, these novel engineered dehydrogenases also catalyzed the reductive amination of a variety of aldehydes and ketones with excellent enantioselectivity, thus exhibiting a dual AmDH/ADH activity. We envisioned that the catalytic bi-functionality of these enzymes could be applied for the direct conversion of alcohols into amines. As a proof-of-principle, we performed an unprecedented one-pot “hydrogen-borrowing” cascade to convert benzyl alcohol to benzylamine using a single enzyme. Conducting the same biocatalytic cascade in the presence of cofactor recycling enzymes (i.e., NADH-oxidase and formate dehydrogenase) increased the reaction yields. In summary, this work provides the first examples of enzymes showing “alcohol aminase” activity.
- Tseliou, Vasilis,Schilder, Don,Masman, Marcelo F.,Knaus, Tanja,Mutti, Francesco G.
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supporting information
p. 3315 - 3325
(2020/12/11)
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- Ruthenium(II) Complex of a Tridentate Azoaromatic Pincer Ligand and its Use in Catalytic Transfer Hydrogenation of Aldehydes and Ketones with Isopropanol
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In this work, a new Ru(II) complex with the redox-active pincer 2,6-bis(phenylazo)pyridine ligand (L) is reported which acts as a metal-ligand bifunctional catalyst for transfer hydrogenation reactions. The isolated complex [(L)Ru(PMe2Ph)2(CH3CN)](ClO4)2; [1](ClO4)2 is characterized by a host of spectroscopic measurements and X-ray structure determination. It is diamagnetic and single-crystal X-ray structure analysis reveals that [1]2+ adopts a distorted octahedral geometry where L binds Ru center in meridional fashion. The observed elongation in the coordinated azo bond length (1.29 ?) is attributed to the extensive π-back bonding, dπ(RuII)→π*(azo)L. The complex [1](ClO4)2 acts as an efficient catalyst, which brings about catalytic transfer hydrogenation reactions of a broad array of aldehydes and ketones in isopropanol and in inert conditions. The selectivity of the catalyst for aldehyde reduction over the other reducible functional groups such as nitro, nitrile, ester etc was also investigated. Mechanistic studies, examined by suitable control reactions and isotope labelling experiments, indicate synergistic participation of both ligand and metal centres via the formation of a fleeting Ru?H intermediate and hydrogen walking to the coordinated azo function of L.
- Saha, Tanushri,Prasad Rath, Santi,Goswami, Sreebrata
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p. 1455 - 1461
(2021/05/18)
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- Tunable System for Electrochemical Reduction of Ketones and Phthalimides
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Herein, we report an efficient, tunable system for electrochemical reduction of ketones and phthalimides at room temperature without the need for stoichiometric external reductants. By utilizing NaN3 as the electrolyte and graphite felt as both the cathode and the anode, we were able to selectively reduce the carbonyl groups of the substrates to alcohols, pinacols, or methylene groups by judiciously choosing the solvent and an acidic additive. The reaction conditions were compatible with a diverse array of functional groups, and phthalimides could undergo one-pot reductive cyclization to afford products with indolizidine scaffolds. Mechanistic studies showed that the reactions involved electron, proton, and hydrogen atom transfers. Importantly, an N3/HN3 cycle operated as a hydrogen atom shuttle, which was critical for reduction of the carbonyl groups to methylene groups.
- Chen, Gong,Qiao, Tianjiao,Wang, Yaxin,Zhang, Jian,Zhao, Jianyou
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supporting information
p. 3297 - 3302
(2021/10/14)
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- Whole seeds of Bauhinia variegata L. (Fabaceae) as an efficient biocatalyst for benzyl alcohol preparations from benzaldehydes
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Whole seeds of Bauhinia variegata L. (Fabaceae) were utilized as a biological reducer to transform benzaldehyde into benzyl alcohol. The effects of some variables such as temperature, the load of substrate and co-solvent, were established to optimize the reductive process. Utilizing the optimal reaction conditions, a laboratory-scale reaction (final concentration of the substrate: 21.2 mM) was performed to obtain benzyl alcohol (conversion: 95%; isolated yield: 49%; productivity: 1.11 g L?1 or 0.046 g L?1h?1 of benzyl alcohol). In addition, using these optimal conditions, fourteen substituted benzaldehydes were reduced, with a conversion achieved to their corresponding benzyl alcohols ranging from 62% to >99% (isolated yields from 7% to 70%). Moreover, useful building blocks by the synthesis of the drugs and important commercial products were also obtained. The scope, limitations and advantages of this new biocatalytic synthetic method are also discussed.
- Aimar, Mario L.,Bordón, Daniela L.,Díaz Panero, Mariángeles,Decarlini, María F.,Demmel, Gabriel I.,Rossi, Laura I.,Vázquez, Ana M.
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- Hydroboration Reaction and Mechanism of Carboxylic Acids using NaNH2(BH3)2, a Hydroboration Reagent with Reducing Capability between NaBH4and LiAlH4
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Hydroboration reactions of carboxylic acids using sodium aminodiboranate (NaNH2[BH3]2, NaADBH) to form primary alcohols were systematically investigated, and the reduction mechanism was elucidated experimentally and computationally. The transfer of hydride ions from B atoms to C atoms, the key step in the mechanism, was theoretically illustrated and supported by experimental results. The intermediates of NH2B2H5, PhCH= CHCOOBH2NH2BH3-, PhCH= CHCH2OBO, and the byproducts of BH4-, NH2BH2, and NH2BH3- were identified and characterized by 11B and 1H NMR. The reducing capacity of NaADBH was found between that of NaBH4 and LiAlH4. We have thus found that NaADBH is a promising reducing agent for hydroboration because of its stability and easy handling. These reactions exhibit excellent yields and good selectivity, therefore providing alternative synthetic approaches for the conversion of carboxylic acids to primary alcohols with a wide range of functional group tolerance.
- Wang, Jin,Ju, Ming-Yue,Wang, Xinghua,Ma, Yan-Na,Wei, Donghui,Chen, Xuenian
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p. 5305 - 5316
(2021/04/12)
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- Photoinduced FeCl3-Catalyzed Alkyl Aromatics Oxidation toward Degradation of Polystyrene at Room Temperature?
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While polystyrene is widely used in daily life as a synthetic plastic, the subsequently selective degradation is still very challenging and highly required. Herein, we disclose a highly practical and selective reaction for the catalytically efficient oxidation of alkyl aromatics (including 1°, 2°, and 3° alkyl aromatics) to carboxylic acids. While dioxygen was used as the sole terminal oxidant, this protocol was catalyzed by the inexpensive and readily available ferric compound (FeCl3) with irradiation of visible light (blue LEDs) under only 1 atmosphere of O2 at room temperature. This system could further facilitate the selective degradation of polystyrene to benzoic acid, providing an important and practical tool to generate high-value chemical from abundant polystyrene wastes.
- Zhang, Guoxiang,Zhang, Zongnan,Zeng, Rong
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supporting information
p. 3225 - 3230
(2021/09/28)
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- Efficient Solvent-Free Hydrosilylation of Aldehydes and Ketones Catalyzed by Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH
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An efficient solvent-free catalyst system for hydrosilylation of aldehydes and ketones was developed based on iron pre-catalyst Fe2(CO)9/C6H4-o-(NCH2PPh2)2BH. The reactions were tolerant of many functional groups and the corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the reaction products. The reaction is likely catalyzed by an in situ generated pincer ligated iron hydride complex. Graphic Abstract: [Figure not available: see fulltext.]
- Fang, Fei,Chang, Jiarui,Zhang, Jie,Chen, Xuenian
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p. 3509 - 3515
(2021/03/16)
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- Silver-Catalyzed Hydroboration of C-X (X = C, O, N) Multiple Bonds
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AgSbF6 was developed as an effective catalyst for the hydroboration of various unsaturated functionalities (nitriles, alkenes, and aldehydes). This atom-economic chemoselective protocol works effectively under low catalyst loading, base- A nd solvent-free moderate conditions. Importantly, this process shows excellent functional group tolerance and compatibility with structurally and electronically diverse substrates (>50 examples). Mechanistic investigations revealed that the reaction proceeds via a radical pathway. Further, the obtained N,N-diborylamines were showcased to be useful precursors for amide synthesis.
- Pandey, Vipin K.,Tiwari, Chandra Shekhar,Rit, Arnab
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supporting information
p. 1681 - 1686
(2021/03/03)
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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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- A method of synthesis of alcohols
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The present invention belongs to the field of organic synthesis technology, specifically a synthesis method of an alcohol; the present invention is under the catalytic action of tert-butanol lithium, with ester compounds and pinacol borane as raw materials, tetrahydrofuran as a solvent, reacted at 100 ° C for 24h, followed by adding 2mol / LNaOH / MeOH solution, stirred at room temperature overnight to obtain alcohol compounds; the raw materials of the present invention are of extensive sources or easy to prepare, the reaction conditions are relatively mild and do not require a large number of / cumbersome additives, in addition to the tert-butanol lithium catalyst is simple, And the prepared alcohol compounds are of high quality and high separation yield.
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Paragraph 0055-0060
(2022/01/10)
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- A substrate-binding metal-organic layer selectively catalyzes photoredox ene-carbonyl reductive coupling reactions
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Intermolecular photoredox ene-carbonyl reductive coupling reactions typically have low product selectivity owing to competing dimerization and/or reduction of ketyl radicals. Herein, we report a metal-organic layer (MOL), Hf-Ir-OTf, as a bifunctional photocatalyst for selective photoredox reductive coupling of ketones or aldehydes with electron-deficient alkenes. Composed of iridium-based photosensitizers (Ir-PSs) and triflated Hf12 clusters, Hf-Ir-OTf uses Lewis acidic Hf sites to bind and activate electron-deficient alkenes to accept ketyl radicals generated by adjacent Ir-PSs, thereby suppressing undesired dimerization and reduction of ketyl radicals to enhance the selectivity for the cross-coupling products. The MOL-catalyzed reductive coupling reaction accommodates a variety of olefinic substrates and tolerates reducible groups, nicely complementing current methods for cross-coupling reactions.
- Fan, Yingjie,You, Eric,Xu, Ziwan,Lin, Wenbin
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supporting information
p. 18871 - 18876
(2021/11/22)
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- Deoxygenative hydroboration of primary, secondary, and tertiary amides: Catalyst-free synthesis of various substituted amines
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Transformation of relatively less reactive functional groups under catalyst-free conditions is an interesting aspect and requires a typical protocol. Herein, we report the synthesis of various primary, secondary, and tertiary amines through hydroboration of amides using pinacolborane under catalyst-free and solvent-free conditions. The deoxygenative hydroboration of primary and secondary amides proceeded with excellent conversions. The comparatively less reactive tertiary amides were also converted to the corresponding N,N-diamines in moderate yields under catalyst-free conditions, although alcohols were obtained as a minor product.
- An, Duk Keun,Jaladi, Ashok Kumar,Kim, Hyun Tae,Yi, Jaeeun
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- A Unified Strategy to Access 2- And 4-Deoxygenated Sugars Enabled by Manganese-Promoted 1,2-Radical Migration
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The selective manipulation of carbohydrate scaffolds is challenging due to the presence of multiple, nearly chemically indistinguishable O-H and C-H bonds. As a result, protecting-group-based synthetic strategies are typically necessary for carbohydrate modification. Here we report a concise semisynthetic strategy to access diverse 2- and 4-deoxygenated carbohydrates without relying on the exhaustive use of protecting groups to achieve site-selective reaction outcomes. Our approach leverages a Mn2+-promoted redox isomerization step, which proceeds via sugar radical intermediates accessed by neutral hydrogen atom abstraction under visible light-mediated photoredox conditions. The resulting deoxyketopyranosides feature chemically distinguishable functional groups and are readily transformed into diverse carbohydrate structures. To showcase the versatility of this method, we report expedient syntheses of the rare sugars l-ristosamine, l-olivose, l-mycarose, and l-digitoxose from commercial l-rhamnose. The findings presented here validate the potential for radical intermediates to facilitate the selective transformation of carbohydrates and showcase the step and efficiency advantages attendant to synthetic strategies that minimize a reliance upon protecting groups.
- Carder, Hayden M.,Suh, Carolyn E.,Wendlandt, Alison E.
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supporting information
p. 13798 - 13805
(2021/09/07)
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- Membrane transport inspired hydrolysis of non-activated esters at near physiological pH
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A positively charged micelle loaded with substrates was transported selectively to the reaction site (cathode) to promote the proximity and localization of the reactants (ester and hydroxide). The guided vehicular delivery coupled with electrolysis allows the hydrolysis of non-activated esters at near physiological pH with significant yields along with recyclability.
- Mandal, Raki,Mahanty, Kingshuk,Mandal, Subhendu,De Sarkar, Suman,Tarafdar, Pradip K.
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supporting information
p. 11088 - 11091
(2021/10/30)
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- A mild and selective Cu(II) salts-catalyzed reduction of nitro, azo, azoxy, N-aryl hydroxylamine, nitroso, acid halide, ester, and azide compounds using hydrogen surrogacy of sodium borohydride
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The first mild, in situ, single-pot, high-yielding well-screened copper (II) salt-based catalyst system utilizing the hydrogen surrogacy of sodium borohydride for selective hydrogenation of a broad range of nitro substrates into the corresponding amine under habitancy of water or methanol like green solvents have been described. Moreover, this catalytic system can also activate various functional groups for hydride reduction within prompted time, with low catalyst-loading, without any requirement of high pressure or molecular hydrogen supply. Notably, this system explores a great potential to substitute expensive traditional hydrogenation methodologies and thus offers a greener and simple hydrogenative strategy in the field of organic synthesis.
- Kalola, Anirudhdha G.,Prasad, Pratibha,Mokariya, Jaydeep A.,Patel, Manish P.
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supporting information
p. 3565 - 3589
(2021/10/12)
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- Homoleptic cobalt(II) phenoxyimine complexes for hydrosilylation of aldehydes and ketones without base activation of cobalt(II)
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Air-stable, easy to prepare, homoleptic cobalt(II) complexes bearing pendant-modified phenoxyimine ligands were synthesized and determined. The complexes exhibited high catalytic performance for reducing aldehydes and ketones via catalytic hydrosilylation, where a hydrosilane and a catalytic amount of the cobalt(II) complex were added under base-free conditions. The reaction proceeded even in the presence of excess water, and excellent functional-group tolerance was observed. Subsequent hydrolysis gave the alcohol in high yields. Moreover, H2O had a critical role in activation of the Co(II) catalyst with hydrosilane. Several additional results also indicated that the cobalt(II) center acts as an active catalyst in the hydrosilylation of aldehydes and ketones.
- Hori, Momoko,Ishikawa, Ryuta,Koga, Yuji,Matsubara, Kouki,Mitsuyama, Tomoaki,Shin, Sayaka
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p. 1379 - 1387
(2021/05/29)
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- Sodium Aminodiboranate, a New Reagent for Chemoselective Reduction of Aldehydes and Ketones to Alcohols
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Sodium aminodiboranate (NaNH 2(BH 3) 2, NaADBH) is a new member of the old borane family, which exhibits superior performance in chemoselective reduction. Experimental results show that NaADBH can rapidly reduce aldehydes and ketones to the corresponding alcohols in high efficiency and selectivity under mild conditions. There are little steric and electronic effects on this reduction.
- Wang, Jin,Guo, Yu,Li, Shouhu,Chen, Xuenian
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supporting information
p. 1104 - 1108
(2021/05/25)
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- Chemoselective and Site-Selective Reductions Catalyzed by a Supramolecular Host and a Pyridine-Borane Cofactor
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Supramolecular catalysts emulate the mechanism of enzymes to achieve large rate accelerations and precise selectivity under mild and aqueous conditions. While significant strides have been made in the supramolecular host-promoted synthesis of small molecules, applications of this reactivity to chemoselective and site-selective modification of complex biomolecules remain virtually unexplored. We report here a supramolecular system where coencapsulation of pyridine-borane with a variety of molecules including enones, ketones, aldehydes, oximes, hydrazones, and imines effects efficient reductions under basic aqueous conditions. Upon subjecting unprotected lysine to the host-mediated reductive amination conditions, we observed excellent ?-selectivity, indicating that differential guest binding within the same molecule is possible without sacrificing reactivity. Inspired by the post-translational modification of complex biomolecules by enzymatic systems, we then applied this supramolecular reaction to the site-selective labeling of a single lysine residue in an 11-amino acid peptide chain and human insulin.
- Morimoto, Mariko,Cao, Wendy,Bergman, Robert G.,Raymond, Kenneth N.,Toste, F. Dean
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supporting information
p. 2108 - 2114
(2021/02/06)
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- Pyridine: N-oxide promoted hydrosilylation of carbonyl compounds catalyzed by [PSiP]-pincer iron hydrides
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Five [PSiP]-pincer iron hydrides 1-5, [(2-Ph2PC6H4)2HSiFe(H)(PMe3)2 (1), (2-Ph2PC6H4)2MeSiFe(H)(PMe3)2 (2), (2-Ph2PC6H4)2PhSiFe(H)(PMe3)2 (3), (2-(iPr)2PC6H4)2HSiFe(H)(PMe3) (4), and (2-(iPr)2PC6H4)2MeSiFe(H)(PMe3)2 (5)], were used as catalysts to study the effects of pyridine N-oxide and the electronic properties of [PSiP]-ligands on the catalytic hydrosilylation of carbonyl compounds. It was proved for the first time that this catalytic process could be promoted with pyridine N-oxide as the initiator at 30 °C because the addition of pyridine N-oxide is beneficial for the formation of an unsaturated hydrido iron complex, which is the key intermediate in the catalytic mechanism. Complex 4 as the best catalyst shows excellent catalytic performance. Among the five complexes, complex 3 was new and the molecular structure of complex 3 was determined by single crystal X-ray diffraction. A proposed mechanism was discussed.
- Chang, Guoliang,Fenske, Dieter,Fuhr, Olaf,Li, Xiaoyan,Sun, Hongjian,Xie, Shangqing,Yang, Wenjing,Zhang, Peng
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p. 9349 - 9354
(2020/09/09)
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- CO2-Controlled Reductive Amination Reactions with NaBH4
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We report the use of CO2 to curb the reactivity of NaBH4 enabling its use in reductive amination reactions. CO2 readily reacts with NaBH4 to decrease its capacity to reduce aldehydes to alcohols while remaining able to reduce imines and iminium ions for desired alkylation reactions. The formation of NaBH(OCHO)3 as a reducing reagent was critical to achieve the desired selectivity. A general protocol was established for C–N bond formation reactions and replacing NaBH4 with NaBD4 allowed for reductive amination with concomitant deuteration to be carried out.
- Petersen, Allan R.,Lauridsen, Jerik Mathew Valera,Lee, Ji-Woong
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supporting information
p. 7368 - 7372
(2020/11/30)
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- Reduction of Aldehydes with Formic acid in Ethanol using Immobilized Iridium Nanoparticles on a Triazine-phosphanimine Polymeric Organic Support
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A novel triazine-phosphanimine polymeric organic support (TPA) was synthesized successfully by a controllable one-pot method using melamine (1,3,5-triazine-2,4,6-triamine) and trichlorophosphane (PCl3). The TPA substrate is a material incorporating P and N atoms which can coordinate with metals as a pincer ligand to stabilize them, providing an efficient heterogeneous support to prepare recyclable transition metal catalyst systems. In this study, TPA was used as support to immobilize iridium nanoparticles in the range of ~8 nm on its surface, resulting in the generation of a novel iridium nanocatalyst system (INP-TPA-POP). This catalyst system was characterized using different microscopic and spectroscopic techniques such as FT-IR, TEM, XPS, XRD, SEM, EDX, elemental analysis, ICP and BET analysis. The INP-TPA-POP nanocatalyst exhibited remarkable activity in reduction of aldehydes to alcohols using formic acids as reducing agent in ethanol as solvent.
- Panahi, Farhad,Haghighi, Fatemeh,Khalafi-Nezhad, Ali
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- Reduction over Condensation of Carbonyl Compounds through a Transient Hemiaminal Intermediate Using Hydrazine
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Reduction of carbonyl moieties to the corresponding alcohol using simply hydrazine hydrate has been considerably unfeasible until now due to the well-known condensation reaction. However, herein, we report that using an excess of 20-fold equivalents, the reduction proceeds in excellent yields. 1H NMR study of the reaction and density functional theory (DFT) calculations indicate that the final fate of the hemiaminal intermediate is crucial to obtain the alcohol or the hydrazone.
- Vilches-Herrera, Marcelo,Gallardo-Fuentes, Sebastián,Aravena-Opitz, Mauricio,Yá?ez-Sánchez, Mauricio,Jiao, Haijun,Holz, Jens,B?rner, Armin,Lühr, Susan
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p. 9213 - 9218
(2020/08/14)
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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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- Hydrogen Bond Directed Photocatalytic Hydrodefluorination and Methods of Use Thereof
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Methods of synthesizing compounds comprising fluorinated aryl groups are disclosed, wherein said methods utilize hydrogen bond directed photocatalytic hydrodefluorination.
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Paragraph 0203
(2021/01/22)
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- Hydrosilylation of Aldehydes and Ketones Catalysed by Bis(phosphinite) Pincer Platinum Hydride Complexes
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Bis(phosphinite) pincer platinum hydride complexes, [2,6-(R2PO)2C6H3]PtH (R=tBu, iPr), were synthesized, characterized and applied to the hydrosilylation of aldehydes and ketones. NMR study and single crystal X-ray diffraction analysis indicated that the hydrides in these two platinum complexes are comparatively less hydridic: down-field 1H NMR resonances (0.71 and 0.98 ppm) and weak Pt?H interactions were observed. Both the platinum complexes were found to be good catalysts for the hydrosilylation of aldehydes and ketones with phenylsilane. The corresponding alcohols were isolated in good to excellent yields following basic hydrolysis of the resultant hydrosilylation products and turnover frequencies (TOFs) up to 3200 h?1 were achieved at 60 °C in toluene, which are much higher than those of the hydrosilylation catalysed by the corresponding nickel pincer hydride complexes. A possible mechanism for the present hydrosilylation process was discussed. (Figure presented.).
- Chang, Jiarui,Fang, Fei,Zhang, Jie,Chen, Xuenian
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p. 2709 - 2715
(2020/06/02)
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- Potassium Fluoride-Catalyzed Hydroboration of Aldehydes and Ketones: Facile Reduction to Primary and Secondary Alcohols
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A catalytic hydroboration of various ketones and aldehydes can be achieved in the presence of inexpensive and commercially available inorganic salts containing fluoride anion. As a result, the reduction of carbonyl moieties to the corresponding primary and secondary alcohols can be achieved at room temperature under mild conditions.
- Kuciński, Krzysztof,Hreczycho, Grzegorz
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supporting information
p. 552 - 555
(2020/02/04)
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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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- Continuous-Flow Amide and Ester Reductions Using Neat Borane Dimethylsulfide Complex
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Reductions of amides and esters are of critical importance in synthetic chemistry, and there are numerous protocols for executing these transformations employing traditional batch conditions. Notably, strategies based on flow chemistry, especially for amide reductions, are much less explored. Herein, a simple process was developed in which neat borane dimethylsulfide complex (BH3?DMS) was used to reduce various esters and amides under continuous-flow conditions. Taking advantage of the solvent-free nature of the commercially available borane reagent, high substrate concentrations were realized, allowing outstanding productivity and a significant reduction in E-factors. In addition, with carefully optimized short residence times, the corresponding alcohols and amines were obtained in high selectivity and high yields. The synthetic utility of the inexpensive and easily implemented flow protocol was further corroborated by multigram-scale syntheses of pharmaceutically relevant products. Owing to its beneficial features, including low solvent and reducing agent consumption, high selectivity, simplicity, and inherent scalability, the present process demonstrates fewer environmental concerns than most typical batch reductions using metal hydrides as reducing agents.
- ?tv?s, Sándor B.,Kappe, C. Oliver
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p. 1800 - 1807
(2020/02/27)
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- Cobalt-catalysed selective synthesis of aldehydes and alcohols from esters
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Efficient and selective reduction of esters to aldehydes and alcohols is reported in which a simple cobalt pincer catalyst catalyses both transformations using diethylsilane as a reductant. Remarkably, the reaction selectivity is controlled by the stoichiometry of diethylsilane. This journal is
- Pattanaik, Sandip,Gunanathan, Chidambaram
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supporting information
p. 7345 - 7348
(2020/07/14)
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- KMnO4-catalyzed chemoselective deprotection of acetate and controllable deacetylation-oxidation in one pot
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A novel and efficient protocol for chemoselective deacetylation under ambient conditions was developed using catalytic KMnO4. The stoichiometric use of KMnO4 highlighted the dual role of a heterogeneous oxidant enabling direct access to aromatic aldehydes in one-pot sequential deacetylation-oxidation. The reaction employed an alternative solvent system and allowed the clean transformation of benzyl acetate to sensitive aldehyde in a single step while preventing over-oxidation to acids. Use of inexpensive and readily accessible KMnO4 as an environmentally benign reagent and the ease of the reaction operation were particularly attractive, and enabled the controlled oxidation and facile cleavage of acetate in a preceding step. This journal is
- Gurawa, Aakanksha,Kumar, Manoj,Rao, Dodla S.,Kashyap, Sudhir
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supporting information
p. 16702 - 16707
(2020/10/27)
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- Selective hydrogenation of primary amides and cyclic di-peptides under Ru-catalysis
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A ruthenium(II)-catalyzed selective hydrogenation of challenging primary amides and cyclic di-peptides to their corresponding primary alcohols and amino alcohols, respectively, is reported. The hydrogenation reaction operates under mild and eco-benign conditions and can be scaled-up.
- Subaramanian, Murugan,Sivakumar, Ganesan,Babu, Jessin K.,Balaraman, Ekambaram
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supporting information
p. 12411 - 12414
(2020/10/30)
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- Scope and limitations of reductive amination catalyzed by half-sandwich iridium complexes under mild reaction conditions
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The conversion of aldehydes and ketones to 1° amines could be promoted by half-sandwich iridium complexes using ammonium formate as both the nitrogen and hydride source. To optimize this method for green chemical synthesis, we tested various carbonyl substrates in common polar solvents at physiological temperature (37 °C) and ambient pressure. We found that in methanol, excellent selectivity for the amine over alcohol/amide products could be achieved for a broad assortment of carbonyl-containing compounds. In aqueous media, selective reduction of carbonyls to 1° amines was achieved in the absence of acids. Unfortunately, at Ir catalyst concentrations of 1 mM in water, reductive amination efficiency dropped significantly, which suggest that this catalytic methodology might be not suitable for aqueous applications where very low catalyst concentration is required (e.g., inside living cells).
- Nguyen, Dat P.,Sladek, Rudolph N.,Do, Loi H.
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supporting information
(2020/07/15)
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- A General Method for Photocatalytic Decarboxylative Hydroxylation of Carboxylic Acids
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A general and practical method for decarboxylative hydroxylation of carboxylic acids was developed through visible light-induced photocatalysis using molecular oxygen as the green oxidant. The addition of NaBH4 to in situ reduce the unstable peroxyl radical intermediate much broadened the substrate scope. Different sp3 carbon-bearing carboxylic acids were successfully employed as substrates, including phenylacetic acid-type substrates, as well as aliphatic carboxylic acids. This transformation worked smoothly on primary, secondary, and tertiary carboxylic acids.
- Khan, Shah Nawaz,Zaman, Muhammad Kashif,Li, Ruining,Sun, Zhankui
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p. 5019 - 5026
(2020/05/01)
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- Cerium(IV) Carboxylate Photocatalyst for Catalytic Radical Formation from Carboxylic Acids: Decarboxylative Oxygenation of Aliphatic Carboxylic Acids and Lactonization of Aromatic Carboxylic Acids
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We found that in situ generated cerium(IV) carboxylate generated by mixing the precursor Ce(OtBu)4 with the corresponding carboxylic acids served as efficient photocatalysts for the direct formation of carboxyl radicals from carboxylic acids under blue light-emitting diodes (blue LEDs) irradiation and air, resulting in catalytic decarboxylative oxygenation of aliphatic carboxylic acids to give C-O bond-forming products such as aldehydes and ketones. Control experiments revealed that hexanuclear Ce(IV) carboxylate clusters initially formed in the reaction mixture and the ligand-to-metal charge transfer nature of the Ce(IV) carboxylate clusters was responsible for the high catalytic performance to transform the carboxylate ligands to the carboxyl radical. In addition, the Ce(IV) carboxylate cluster catalyzed direct lactonization of 2-isopropylbenzoic acid to produce the corresponding peroxy lactone and ?3-lactone via intramolecular 1,5-hydrogen atom transfer (1,5-HAT).
- Hirosawa, Keishi,Mashima, Kazushi,Satoh, Tetsuya,Shinohara, Koichi,Shirase, Satoru,Tamaki, Sota,Tsurugi, Hayato
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supporting information
(2020/03/25)
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- Chemoenzymatic Synthesis of 5-Hydroxymethylfurfural (HMF)-Derived Plasticizers by Coupling HMF Reduction with Enzymatic Esterification
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Biobased plasticizers, as substitutes for phthalates, have been synthesized from 5-hydroxymethylfurfural (HMF) and carboxylic acids (or esters) through a chemoenzymatic cascade process that involves as its first step the reduction of 5-hydroxymethylfurfural into 2,5-bis(hydroxymethyl)furan (BHMF), followed by the esterification of BHMF with carboxylic acids (or esters) by using a supported lipase (Novozym 435). The reduction of HMF into BHMF is performed by using monodisperse metallic Co nanoparticles with a thin carbon shell (Co@C) with high activity and selectivity. After optimization of reaction conditions (temperature, hydrogen pressure, and solvent), it is possible to achieve 97 % conversion of HMF with 99 % selectivity to BHMF after 2 h reaction time. The reduction of HMF and esterification of BHMF using carboxylic acids or vinyl esters as acyl donors by lipase are optimized separately in batch and in fixed-bed continuous reactors. The coupling of two flow reactors (for reduction and subsequent esterification) working under optimized reaction conditions affords the diesters of BHMF in roughly 90 % yield with no loss of activity during 60 h of operation.
- Arias, Karen S.,Carceller, Jose M.,Climent, Maria J.,Corma, Avelino,Iborra, Sara
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p. 1864 - 1875
(2020/03/11)
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- Manganese-catalysed transfer hydrogenation of esters
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Manganese catalysed ester reduction using ethanol as a hydrogen transfer agent in place of dihydrogen is reported. High yields can be achieved for a range of substrates using 1 mol% of a Mn(i) catalyst, with an alkoxide promoter. The catalyst is derived from a tridentate P,N,N ligand.
- Oates, Conor L.,Widegren, Magnus B.,Clarke, Matthew L.
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supporting information
p. 8635 - 8638
(2020/08/21)
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- Selective Room-Temperature Hydrogenation of Carbonyl Compounds under Atmospheric Pressure over Platinum Nanoparticles Supported on Ceria-Zirconia Mixed Oxide
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A Pt/CeO2-ZrO2 catalytic system was able to initiate an extremely intense hydrogen spillover providing a huge amount of activated hydrogen (12 mol/mol Pt) at temperatures –50°C - +25°C, which was not observed before. The idea was to use this activated hydrogen for reduction of carbonyl compounds under ambient conditions. Thus, the efficient and selective heterogeneous hydrogenation of carbonyl compounds of different structure, including 5-hydroxymethylfurfural and cinnamaldehyde, to the corresponding alcohols with quantitative yields was successfully performed over the Pt/CeO2-ZrO2 catalysts at room-temperature and atmospheric pressure of H2. The proposed catalysts afforded hydrogenation under significantly milder conditions with a much higher activity and selectivity compared to the commercial catalysts and reported catalytic systems. Hydrogenation of the C=O bond in the presence of a C=C bond proceeded with a high regioselectivity.
- Redina, Elena A.,Vikanova, Kseniia V.,Kapustin, Gennady I.,Mishin, Igor V.,Tkachenko, Olga P.,Kustov, Leonid M.
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supporting information
p. 4159 - 4170
(2019/07/12)
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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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- A method of synthesis of primary alcohol (by machine translation)
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The invention discloses a method for synthesizing a primary alcohol, using transition metal catalysis, the use of isopropanol as a hydrogen source to synthesize primary alcohol, the reaction not only using a cheap, environmental protection of isopropanol as a hydrogen source and solvent, and has high yield, environmental protection and the like, so that the reaction has broad prospects for development. (by machine translation)
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Paragraph 0060; 0061; 0062; 0063; 0064
(2019/03/17)
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- Borinic Acid Mediated Hydrosilylations: Reductions of Carbonyl Derivatives
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4-Fluoro-2-chlorophenylborinic acid acts as a precatalyst in the presence of phenylsilane for the facile reduction of ketones, aldehydes and imines. Notably, synergistic mediation of a tertiary amine was found essential to trigger silicon to boron hydride transfer to generate a key amine–diarylhydroborane Lewis complex.
- Chardon, Aurélien,Rouden, Jacques,Blanchet, Jér?me
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supporting information
p. 995 - 998
(2018/12/13)
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- Ambient-pressure hydrogenation of ketones and aldehydes by a metal-ligand bifunctional catalyst [Cp*Ir(2,2′-bpyO)(H2O)] without using base
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An efficient catalytic system for hydrogenation of ketones and aldehydes using a Cp*Ir complex [Cp*Ir(2,2′-bpyO)(H2O)] bearing a bipyridine-based functional ligand as catalyst has been developed. A wide variety of secondary and primary alcohols were synthesized by the catalyzed hydrogenation of ketones and aldehydes under facile atmospheric-pressure without a base. The catalyst also displays an excellent chemoselectivity towards other carbonyl functionalities and unsaturated motifs. This catalytic system exhibits high activity for hydrogenation of ketones and aldehydes with H2 gas.
- Wang, Rongzhou,Qi, Jipeng,Yue, Yuancheng,Lian, Zhe,Xiao, Haibin,Zhuo, Shuping,Xing, Lingbao
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- Polypyridyl iridium(III) based catalysts for highly chemoselective hydrogenation of aldehydes
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Iridium-catalyzed transfer hydrogenation (TH) of carbonyl compounds using HCOOR (R = H, Na, NH4) as a hydrogen source is a pivotal process as it provides the clean process and is easy to execute. However, the existing highly efficient iridium catalysts work at a narrow pH; thus, does not apply to a wide variety of substrates. Therefore, the development of a new catalyst which works at a broad pH range is essential as it can gain a broader scope of utilization. Here we report highly efficient polypyridyl iridium(III) catalysts, [Ir(tpy)(L)Cl](PF6)2 {where tpy = 2,2′:6′,2′'-Terpyridine, L = phen (1,10-Phenanthroline), Me2phen (4,7-Dimethyl-1,10-phenanthroline), Me4phen (3,4,7,8-Tetramethyl-1,10-phenanthroline), Me2bpy (4,4′-Dimethyl-2–2′-dipyridyl)} for the chemoselective reduction of aldehydes to alcohols in aqueous ethanol and sodium formate as the hydride source. The reaction can be carried out efficiently in broad pH ranges, from pH 6 to 11. These catalysts are air stable, easy to prepare using commercially available starting materials, and are highly applicable for a wide range of substrates, such as electron-rich or deficient (hetero)arenes, halogens, phenols, alkoxy, ketones, esters, carboxylic acids, cyano, and nitro groups. Particularly, acid and hydroxy groups containing aldehydes were reduced successfully in basic and acidic reaction conditions, demonstrating the efficiency of the catalyst in a broad pH range with high conversion rates under microwave irradiation.
- Pandrala, Mallesh,Resendez, Angel,Malhotra, Sanjay V.
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p. 283 - 288
(2019/09/30)
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- Efficient transfer hydrogenation of carbonyl compounds catalyzed by selenophenolato hydrido iron(II) complexes
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Selenophenolato hydrido iron(II) complexes 1–3 cis-[(H)(SeAr)Fe(PMe3)4] (Ar = C6H5 (1), p-MeOC6H4 (2) and o-MeC6H4 (3)) could catalyze transfer hydrogenation of aldehydes and ketones. Among the three complexes, catalyst 1 exhibited the highest catalytic activity. The catalytic reactions took place under very mild conditions, using isopropanol as solvent and hydrogen source, tBuONa as base under 60–80 °C. This catalytic system has good tolerance for many functional groups, such as halides, C[dbnd]C double bonds, nitro groups and cyano groups at the phenyl ring of the substrates.
- Wang, Yangyang,Du, Zhengyin,Zheng, Tingting,Sun, Hongjian,Li, Xiaoyan
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