- Ferrocenyl-aryl based trans-chelating diphosphine ligands: Synthesis, molecular structure and application in enantioselective hydrogenation
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Potentially trans-chelating diphosphine ligands based on a ferrocenyl-aryl backbone were synthesised in a four-step sequence and the molecular structures in the solid state of two representatives were determined by X-ray diffraction. High throughput screening of these ligands in rhodium-, ruthenium- and iridium-mediated hydrogenations of a variety of alkenes and ketones revealed that these ligands can deliver high enantioselectivity for alkenes (up to 98% ee) but are less selective when ketones are used as the substrates. The coordination behaviour of one ligand in its square planar palladium and platinum dichloride complexes was studied by 31P NMR and only trans-chelated complexes, together with oligomeric by-products, were observed. Reaction with the (p-cymene)ruthenium dichloride dimer, [RuCl2(pcymene)] 2, resulted in a mixture of diastereomeric complexes.
- Schuecker, Raffael,Mereiter, Kurt,Spindler, Felix,Weissensteiner, Walter
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Read Online
- BAKER'S YEAST-MEDIATED HYDROGENATION OF 2-SUBSTITUTED ALLYL ALCOHOLS: A BIOCATALYTIC ROUTE TO A NEW HIGHLY ENANTIOSELECTIVE SYNTHESIS OF (R)-2-METHYL ALKANOLS
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The biohydrogenation of 2-substituted allyl alcohols 1a-c proceeds enentioselectively (95-98percent ee) to afford (R)-2-methyl alkanols 2a-c.
- Ferraboschi, Patrizia,Casati, Silvana,Santaniello, Enzo
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Read Online
- Your mother was right, washing matters: An alkyne-analog of ibuprofen reveals unwanted reactivity of aromatic compounds with proteins during copper-catalyzed click chemistry
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Bioorthogonal chemistry, in particular the copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), has enabled the robust identification of covalent protein targets of probes and drugs. Ibuprofen is commonly used pain and fever reducer and is sold as an enantiomeric racemate. Interestingly, the stereoisomers can be enzymatically converted through an ibuprofen-CoA thioester intermediate, which might non-specifically react with protein nucleophiles. Here, we use an alkyne-analog of ibuprofen to make two discoveries. First, we find that ibuprofen likely does not result in notable chemical labeling of proteins. However, we secondly find that aromatic compounds can react with proteins during the CuAAC reaction unless they are appropriately washed out of the mixture. This second discovery of false positive labeling has important technical implications for the application of this approach.
- Cutolo, Giuliano,Pratt, Matthew R.,Shankar, Sahiti N.
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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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- A Water/Toluene Biphasic Medium Improves Yields and Deuterium Incorporation into Alcohols in the Transfer Hydrogenation of Aldehydes
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Deuterium labeling is an interesting process that leads to compounds of use in different fields. We describe the transfer hydrogenation of aldehydes and the selective C1 deuteration of the obtained alcohols in D2O, as the only deuterium source. Different aromatic, alkylic and α,β-unsaturated aldehydes were reduced in the presence of [RuCl(p-cymene)(dmbpy)]BF4, (dmbpy=4,4′-dimethyl-2,2′-bipyridine) as the pre-catalyst and HCO2Na/HCO2H as the hydrogen source. Moreover, furfural and glucose, were selectively reduced to the valuable alcohols, furfuryl alcohol and sorbitol. The processes were carried out in neat water or in a biphasic water/toluene system. The biphasic system allowed easy recycling, higher yields, and higher selective D incorporation (using D2O/toluene). The deuteration took place due to an efficient effective M–H/D+ exchange from D2O that allows the inversion of polarity of D+ (umpolung). DFT calculations that explain the catalytic behavior in water are also included.
- Ruiz-Casta?eda, Margarita,Santos, Lucía,Manzano, Blanca R.,Espino, Gustavo,Jalón, Félix A.
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p. 1358 - 1372
(2021/03/16)
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- Carbon monoxide and hydrogen (syngas) as a C1-building block for selective catalytic methylation
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A catalytic reaction using syngas (CO/H2) as feedstock for the selective β-methylation of alcohols was developed whereby carbon monoxide acts as a C1 source and hydrogen gas as a reducing agent. The overall transformation occurs through an intricate network of metal-catalyzed and base-mediated reactions. The molecular complex [Mn(CO)2Br[HN(C2H4PiPr2)2]]1comprising earth-abundant manganese acts as the metal component in the catalytic system enabling the generation of formaldehyde from syngas in a synthetically useful reaction. This new syngas conversion opens pathways to install methyl branches at sp3carbon centers utilizing renewable feedstocks and energy for the synthesis of biologically active compounds, fine chemicals, and advanced biofuels.
- Kaithal, Akash,H?lscher, Markus,Leitner, Walter
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p. 976 - 982
(2021/02/06)
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- Highly efficient NHC-iridium-catalyzed β-methylation of alcohols with methanol at low catalyst loadings
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The methylation of alcohols is of great importance since a broad number of bioactive and pharmaceutical alcohols contain methyl groups. Here, a highly efficient β-methylation of primary and secondary alcohols with methanol has been achieved by using bis-N-heterocyclic carbene iridium (bis-NHC-Ir) complexes. Broad substrate scope and up to quantitative yields were achieved at low catalyst loadings with only hydrogen and water as by-products. The protocol was readily extended to the β-alkylation of alcohols with several primary alcohols. Control experiments, along with DFT calculations and crystallographic studies, revealed that the ligand effect is critical to their excellent catalytic performance, shedding light on more challenging Guerbet reactions with simple alcohols. [Figure not available: see fulltext.].
- Lu, Zeye,Zheng, Qingshu,Zeng, Guangkuo,Kuang, Yunyan,Clark, James H.,Tu, Tao
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p. 1361 - 1366
(2021/06/30)
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- Application of Trimethylgermanyl-Substituted Bisphosphine Ligands with Enhanced Dispersion Interactions to Copper-Catalyzed Hydroboration of Disubstituted Alkenes
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We report the incorporation of large substituents based on heavy main-group elements that are atypical in ligand architectures to enhance dispersion interactions and, thereby, enhance enantioselectivity. Specifically, we prepared the chiral biaryl bisphosphine ligand (TMG-SYNPHOS) containing 3,5-bis(trimethylgermanyl)phenyl groups on phosphorus and applied this ligand to the challenging problem of enantioselective hydrofunctionalization reactions of 1,1-disubtituted alkenes. Indeed, TMG-SYNPHOS forms a copper complex that catalyzes hydroboration of 1,1-disubtituted alkenes with high levels of enantioselectivity, even when the two substituents are both primary alkyl groups. In addition, copper catalysts bearing ligands possessing germanyl groups were much more active for hydroboration than one derived from DTBM-SEGPHOS, a ligand containing 3,5-di-tert-butyl groups and widely used for copper-catalyzed hydrofunctionalization. This observation led to the identification of DTMGM-SEGPHOS, a bisphosphine ligand bearing 3,5-bis(trimethylgermanyl)-4-methoxyphenyl groups as the substituents on the phosphorus, as a new ligand that forms a highly active catalyst for hydroboration of unactivated 1,2-disubstituted alkenes, a class of substrates that has not readily undergone copper-catalyzed hydroboration previously. Computational studies revealed that the enantioselectivity and catalytic efficiency of the germanyl-substituted ligands is higher than that of the silyl and tert-butyl-substituted analogues because of attractive dispersion interactions between the bulky trimethylgermanyl groups on the ancillary ligand and the alkene substrate and that Pauli repulsive interactions tended to decrease enantioselectivity.
- Xi, Yumeng,Su, Bo,Qi, Xiaotian,Pedram, Shayun,Liu, Peng,Hartwig, John F.
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supporting information
p. 18213 - 18222
(2020/12/04)
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- Synthesis and olfactory evaluation of optically active β-alkyl substituted γ-lactones and whiskey lactone analogues
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Optically active β-alkyl substituted γ-lactones and whiskey lactone analogues were synthesized, and the odor properties were evaluated. During the preparation of the chiral intermediates, we found good reaction conditions for the highly enantioselective esterification of 3-arylmethyl-2-methyl-1-propanols to kinetically resolve them. The results of the olfactory evaluations of the synthesized lactones revealed that the alkyl groups on the γ-lactone rings played an important role for the odor profiles.
- Kato, Daiki,Kawasaki, Masashi,Morita, Yuko,Okada, Takuya,Tanaka, Yasuo,Toyooka, Naoki
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- Biocatalytic reduction of α,β-unsaturated carboxylic acids to allylic alcohols
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We have developed robust in vivo and in vitro biocatalytic systems that enable reduction of α,β-unsaturated carboxylic acids to allylic alcohols and their saturated analogues. These compounds are prevalent scaffolds in many industrial chemicals and pharmaceuticals. A substrate profiling study of a carboxylic acid reductase (CAR) investigating unexplored substrate space, such as benzo-fused (hetero)aromatic carboxylic acids and α,β-unsaturated carboxylic acids, revealed broad substrate tolerance and provided information on the reactivity patterns of these substrates. E. coli cells expressing a heterologous CAR were employed as a multi-step hydrogenation catalyst to convert a variety of α,β-unsaturated carboxylic acids to the corresponding saturated primary alcohols, affording up to >99percent conversion. This was supported by the broad substrate scope of E. coli endogenous alcohol dehydrogenase (ADH), as well as the unexpected CC bond reducing activity of E. coli cells. In addition, a broad range of benzofused (hetero)aromatic carboxylic acids were converted to the corresponding primary alcohols by the recombinant E. coli cells. An alternative one-pot in vitro two-enzyme system, consisting of CAR and glucose dehydrogenase (GDH), demonstrates promiscuous carbonyl reductase activity of GDH towards a wide range of unsaturated aldehydes. Hence, coupling CAR with a GDH-driven NADP(H) recycling system provides access to a variety of (hetero)aromatic primary alcohols and allylic alcohols from the parent carboxylates, in up to >99percent conversion. To demonstrate the applicability of these systems in preparative synthesis, we performed 100 mg scale biotransformations for the preparation of indole-3-aldehyde and 3-(naphthalen-1-yl)propan-1-ol using the whole-cell system, and cinnamyl alcohol using the in vitro system, affording up to 85percent isolated yield.
- Aleku, Godwin A.,Leys, David,Roberts, George W.
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p. 3927 - 3939
(2020/07/09)
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- Manganese(I)-Catalyzed β-Methylation of Alcohols Using Methanol as C1 Source
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Highly selective β-methylation of alcohols was achieved using an earth-abundant first row transition metal in the air stable molecular manganese complex [Mn(CO)2Br[HN(C2H4PiPr2)2]] 1 ([HN(C2H4PiPr2)2]=MACHO-iPr). The reaction requires only low loadings of 1 (0.5 mol %), methanolate as base and MeOH as methylation reagent as well as solvent. Various alcohols were β-methylated with very good selectivity (>99 %) and excellent yield (up to 94 %). Biomass derived aliphatic alcohols and diols were also selectively methylated on the β-position, opening a pathway to “biohybrid” molecules constructed entirely from non-fossil carbon. Mechanistic studies indicate that the reaction proceeds through a borrowing hydrogen pathway involving metal–ligand cooperation at the Mn-pincer complex. This transformation provides a convenient, economical, and environmentally benign pathway for the selective C?C bond formation with potential applications for the preparation of advanced biofuels, fine chemicals, and biologically active molecules.
- Kaithal, Akash,van Bonn, Pit,H?lscher, Markus,Leitner, Walter
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supporting information
p. 215 - 220
(2019/12/03)
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- Hydrogenation of alkenes via cooperative hydrogen atom transfer
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Radical hydrogenation via hydrogen atom transfer (HAT) to alkenes is an increasingly important transformation for the formation of thermodynamic alkane isomers. Current single-catalyst methods require stoichiometric oxidant in addition to hydride (H-) source to function. Here we report a new approach to radical hydrogenation: cooperative hydrogen atom transfer (cHAT), where each hydrogen atom donated to the alkene arrives from a different catalyst. Further, these hydrogen atom (H?) equivalents are generated from complementary hydrogen atom precursors, with each alkane requiring one hydride (H-) and one proton (H+) equivalent and no added oxidants. Preliminary mechanistic study supports this reaction manifold and shows the intersection of metal-catalyzed HAT and thiol radical trapping HAT catalytic cycles to be essential for effective catalysis. Together, this unique catalyst system allows us to reduce a variety of unactivated alkene substrates to their respective alkanes in high yields and diastereoselectivities and introduces a new approach to radical hydrogenation.
- Kattamuri, Padmanabha V.,West, Julian G.
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supporting information
p. 19316 - 19326
(2020/11/13)
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- A General Regioselective Synthesis of Alcohols by Cobalt-Catalyzed Hydrogenation of Epoxides
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A straightforward methodology for the synthesis of anti-Markovnikov-type alcohols is presented. By using a specific cobalt triphos complex in the presence of Zn(OTf)2 as an additive, the hydrogenation of epoxides proceeds with high yields and selectivities. The described protocol shows a broad substrate scope, including multi-substituted internal and terminal epoxides, as well as a good functional-group tolerance. Various natural-product derivatives, including steroids, terpenoids, and sesquiterpenoids, gave access to the corresponding alcohols in moderate-to-excellent yields.
- Beller, Matthias,Junge, Kathrin,Leischner, Thomas,Li, Wu,Liu, Weiping
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supporting information
p. 11321 - 11324
(2020/05/16)
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- Controlled Reduction of Carboxamides to Alcohols or Amines by Zinc Hydrides
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New protocols for controlled reduction of carboxamides to either alcohols or amines were established using a combination of sodium hydride (NaH) and zinc halides (ZnX2). Use of a different halide on ZnX2 dictates the selectivity, wherein the NaH-ZnI2 system delivers alcohols and NaH-ZnCl2 gives amines. Extensive mechanistic studies by experimental and theoretical approaches imply that polymeric zinc hydride (ZnH2)∞ is responsible for alcohol formation, whereas dimeric zinc chloride hydride (H?Zn?Cl)2 is the key species for the production of amines.
- Ong, Derek Yiren,Yen, Zhihao,Yoshii, Asami,Revillo Imbernon, Julia,Takita, Ryo,Chiba, Shunsuke
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supporting information
p. 4992 - 4997
(2019/03/13)
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- Phosphite-thioether/selenoether Ligands from Carbohydrates: An Easily Accessible Ligand Library for the Asymmetric Hydrogenation of Functionalized and Unfunctionalized Olefins
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A large family of phosphite-thioether/selenoether ligands has been easily prepared from accessible L-(+)-tartaric acid and D-(+)-mannitol and applied in the M-catalyzed (M=Ir, Rh) asymmetric hydrogenation of a broad number of substrates (46 in total). Its highly modular architecture has been crucial to maximize the catalytic performance. Improving most of the reported approaches, this ligand family presents a broad substrate scope. By selecting the ligand parameters high enantioselectivities (ee's up to 99 %) have therefore been achieved in a broad range of both, functionalized and unfunctionalized substrates. Interestingly, both enantiomers of the hydrogenation products can be usually achieved by changing the ligand parameters.
- Margalef, Jèssica,Borràs, Carlota,Alegre, Sabina,Alberico, Elisabetta,Pàmies, Oscar,Diéguez, Montserrat
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p. 2142 - 2168
(2019/04/13)
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- CO-Free Enantioselective Hydroformylation of Functionalised Alkenes: Using a Dual Catalyst System to Give Improved Selectivity and Yield
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The scope of carbon monoxide-free Asymmetric Transfer HydroFormylation (ATHF) procedures using a highly active single catalyst system derived from 1,2-bis-((2,5)-diphenylphospholano)ethane as chiral ligand has been studied. This reveals some highly successful reactions, but also significant limitations. The development of a new protocol in which a catalyst for formaldehyde decomposition to CO and H2 is combined with the catalyst of choice for the subsequent asymmetric hydroformylation is described. This enables ATHF reactions that were problematic to be significantly improved. The new method has been used in the synthesis of several key precursors to biologically active molecules. (Figure presented.).
- Pittaway, Rachael,Dingwall, Paul,Fuentes, José. A.,Clarke, Matthew. L.
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supporting information
p. 4334 - 4341
(2019/08/21)
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- Method used for reduction of tertiary amide into alcohols and/or amines
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The invention discloses a method used for reduction of tertiary amide into alcohols and/or amines. The method comprises following steps: tertiary amide, an alkali metal reagent, and a proton donor agent are added into an organic solvent for a following reaction selectively: when the proton donor agent is a raw material alcohol and/or inorganic salt aqueous solution, the reaction product is an alcohol compound and/or tertiary amine compound. The method is capable of realizing selective reduction of tertiary amide into alcohols and tertiary amine compounds, the yield is high, the suitable rangeis wide, operation is safe and simple, the adopted raw materials are cheap and easily available; no precious metal catalyst, toxic silanes, and flammable and combustible metal hydrides are adopted; notoxic by product is generated; reaction is more friendly to the environment; problems in the prior art that amide compound reducing method operation is complex, conditions are strict, and control ofproducts is difficult are solved.
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Paragraph 0219-0222
(2019/08/07)
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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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- Highly pH-Dependent Chemoselective Transfer Hydrogenation of α,β-Unsaturated Aldehydes in Water
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The pH-dependent selective Ir-catalyzed hydrogenation of α,β-unsaturated aldehydes was realized in water. Using HCOOH as the hydride donor at low pH, the unsaturated alcohol products were obtained exclusively, while the saturated alcohol products were formed preferentially by employing HCOONa as the hydride donor at high pH. A wide range of functional groups including electron-rich as well as electron-poor substituents on the aryl group of α,β-unsaturated aldehydes can be tolerated, affording the corresponding products in excellent yields with high TOF values. High selectivity and yields were also observed for α,β-unsaturated aldehydes with aliphatic substituents. Our mechanistic investigations indicate that the pH value is critical to the chemoselectivity.
- Luo, Nianhua,Liao, Jianhua,Ouyang, Lu,Wen, Huiling,Liu, Jitian,Tang, Weiping,Luo, Renshi
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p. 3025 - 3031
(2019/08/30)
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- Synthesis method of chiral compound R-(+)-2-methyl-3-phenyl-1-propyl alcohol
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The invention discloses a synthesis method of a chiral compound R-(+)-2-methyl-3-phenyl-1-propyl alcohol. The synthesis method comprises the following steps: taking alpha-methyl cinnamaldehyde as a raw material and performing a catalytic hydrogenation reaction on the alpha-methyl cinnamaldehyde to obtain (plus or minus)-2-methyl-3-phenyl-1-propyl alcohol; performing an esterification reaction on the (plus or minus)-2-methyl-3-phenyl-1-propyl alcohol and phthalic anhydride to form monoester; performing an acid-base reaction on the monoester and S-(-)-alpha-phenylethylamine to form salt; separating and purifying a single chiral isomer in the salt through crystallization and recrystallization; performing a hydrolysis reaction to obtain R-(+)-2-methyl-3-phenyl-1-propyl alcohol and a hydrolysisby-product; and finally, removing the hydrolysis by-product through separation and purification to obtain the R-(+)-2-methyl-3-phenyl-1-propyl alcohol.
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Paragraph 0019-0020; 0030-0031; 0041-0042
(2019/04/04)
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- Method for synthesizing chiral compound S-(-)-2-methyl-3-phenyl-1-propanol
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The invention discloses a method for synthesizing a chiral compound S-(-)-2-methyl-3-phenyl-1-propanol. The method comprises the steps that alpha-methyl cinnamic aldehyde is used as a raw material, and (+/-)-2-methyl-3-phenyl-1-propanol is first synthesized by a catalytic hydrogenation reaction; then a monoester is formed by an esterification reaction with phthalic anhydride; then a salt is formedby an acid-base reaction with R-(+)-alpha-phenethylamine; then a single chiral isomer is separated and purified by crystallization and recrystallization; then S-(-)-2-methyl-3-phenyl-1-propanol and ahydrolysis by-product are obtained by a hydrolysis reaction; and finally, separation and purification are performed to remove the hydrolysis by-product to obtain S-(-)-2-methyl-3-phenyl-1- propanol.
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Paragraph 0031; 0032
(2019/04/10)
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- Acid-Promoted Hydroformylative Synthesis of Alcohol with Carbon Dioxide by Heterobimetallic Ruthenium-Cobalt Catalytic System
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The acid-aided heterobimetallic ruthenium-cobalt catalytic system for the reductive hydroformylation with carbon dioxide was established. Various alkenes, including waste from biomass and petroleum industry, could be upgraded to valuable alcohols with this protocol. Acid-promoted reverse water-gas shift (RWGS), thereby accelerating the hydroformylative synthesis of alcohol. The theoretical computations revealed that acid promoted RWGS by facilitating the dehydroxylation of ruthenium hydroxy carbonyl intermediate.
- Zhang, Xuehua,Tian, Xinxin,Shen, Chaoren,Xia, Chungu,He, Lin
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p. 1986 - 1992
(2019/03/17)
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- Ruthenium(II)-Catalyzed β-Methylation of Alcohols using Methanol as C1 Source
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Selective introduction of methyl branches into the carbon chains of alcohols can be achieved with low loadings of ruthenium precatalyst [RuH(CO)(BH4)(HN(C2H4PPh2)2)] (Ru-MACHO-BH) using methanol both as methylating reagent and as reaction medium. A wide range of structurally divers alcohols was β-methylated with excellent selectivity (>99 %) in fair to high yields (up to 94 %) under standard conditions, and turnover numbers up to 18,000 could be established. The overall reaction rate of the complex catalytic network appears to be governed by interconnection of the individual subcycles through availability of the reactive intermediates. The synthetic procedure opens pathways to important structural motifs following the Green Chemistry principles.
- Kaithal, Akash,Schmitz, Marc,H?lscher, Markus,Leitner, Walter
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p. 5287 - 5291
(2019/05/28)
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- Iron-Catalyzed Borrowing Hydrogen β- C(sp3)-Methylation of Alcohols
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Herein we report the iron-catalyzed β-C(sp3)-methylation of primary alcohols using methanol as a C1 building block. This borrowing hydrogen approach employs a well-defined bench-stable (cyclopentadienone)iron(0) carbonyl complex as precatalyst (5 mol %) and enables a diverse selection of substituted 2-arylethanols to undergo β-C(sp3)-methylation in good isolated yields (24 examples, 65% average yield).
- Polidano, Kurt,Williams, Jonathan M. J.,Morrill, Louis C.
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p. 8575 - 8580
(2019/09/12)
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- One-Pot Conversion of Allylic Alcohols to α-Methyl Ketones via Iron-Catalyzed Isomerization-Methylation
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A one-pot iron-catalyzed conversion of allylic alcohols to α-methyl ketones has been developed. This isomerization-methylation strategy utilized a (cyclopentadienone)iron(0) carbonyl complex as precatalyst and methanol as the C1 source. A diverse range of allylic alcohols undergoes isomerization-methylation to form α-methyl ketones in good isolated yields (up to 84% isolated yield).
- Latham, Daniel E.,Polidano, Kurt,Williams, Jonathan M. J.,Morrill, Louis C.
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supporting information
p. 7914 - 7918
(2019/10/16)
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- Synthesis of β-Chiral Amines by Dynamic Kinetic Resolution of α-Branched Aldehydes Applying Imine Reductases
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Imine reductases (IREDs) allow the one-step preparation of optically active secondary and tertiary amines by reductive amination of ketones. Until now, mainly α-chiral amines have been prepared by this route. In this study, we explored the possibility of synthesizing β-chiral amines, a class of compounds which is also frequently found as structural motif in pharmaceuticals but much more challenging to prepare due to the following reasons: (i) The aldehyde substrate already contains the chiral center and needs to be racemized to enable full conversion. (ii) Because the intermediate imine bears the stereo center two carbon atoms remote to the imine nitrogen, it is more challenging to achieve high enantioselectivity compared to α-chiral amine synthesis. For investigating the proof of concept, we first confirmed that different IREDs are able to convert a variety of α-branched aldehydes when combined with five different amine substrates. The IRED from Streptomyces ipomoeae was a suitable enzyme facilitating the dynamic kinetic resolution of 2-phenylpropanal and a substituted 2-methyl-3-phenylpropanal: the corresponding N-methylated β-chiral amines were obtained with '95 % conversion and 78 and 95 %ee. Other amines were formed with low to moderate enantiomeric excess. This exemplifies the potential of IREDs for the one-step synthesis of secondary β-chiral amines, but also the challenge to identify highly selective enzymes for a desired amine product.
- Matzel, Philipp,Wenske, Sebastian,Merdivan, Simon,Günther, Sebastian,H?hne, Matthias
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p. 4281 - 4285
(2019/08/20)
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- TETRAHYDRO-IMIDAZO QUINOLINE COMPOSITIONS AS CBP/P300 INHIBITORS
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The present disclosure is directed to inhibitors of the CBP/p300 family of bromodomains. The compounds can be useful in the treatment of disease or disorders associated with the inhibition of the CBP/p300 family of bromodomains. For instance, the disclosure is concerned with compounds and compositions for inhibition of the CBP/p300 family of bromodomains, methods of treating, preventing, or ameliorating diseases or disorders associated with the inhibition of CBP/p300 family of bromodomains, and methods of synthesis of these compounds.
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Paragraph 00118
(2019/04/11)
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- Pyrrolidine-Based P,O Ligands from Carbohydrates: Easily Accessible and Modular Ligands for the Ir-Catalyzed Asymmetric Hydrogenation of Minimally Functionalized Olefins
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The potential of P,O-iminosugar based ligands in the Ir-catalyzed asymmetric hydrogenation of minimally functionalized olefins is presented. These new ligands were prepared from easily available carbohydrates (D-mannose, D-ribose and D-arabinose). The stereochemical and polyfunctional diversity of carbohydrates allowed the modulation of the ligands, both from their electronic properties and the rigidity of their backbone. High enantioselectivities (ee’s up to 99 %) can be reached in the hydrogenation of selected tri- and disubstituted substrates.
- Elías-Rodríguez, Pilar,Borràs, Carlota,Carmona, Ana T.,Faiges, Jorge,Robina, Inmaculada,Pàmies, Oscar,Diéguez, Montserrat
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p. 5414 - 5424
(2018/12/11)
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- Enantioselective Copper-Catalyzed Methylboration of Alkenes
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An enantioselective Cu-catalyzed borylative cross-coupling reaction of alkenes, bis(pinacolato)diboron (B2(pin)2), and methyl iodide is reported. Alkenes including styrenes, β-substituted styrenes, and challenging aliphatic olefins were smoothly transferred to the desired methylboration products with excellent diastereoselectivities (dr up to >99:1) and enantioselectivities (er up to 99:1). The utility of this process was demonstrated by the synthesis of naproxen and formal synthesis of two natural products.
- Chen, Bin,Cao, Peng,Liao, Yang,Wang, Min,Liao, Jian
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supporting information
p. 1346 - 1349
(2018/03/09)
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- Dess-Martin periodinane oxidative rearrangement for preparation of α-keto thioesters
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A Dess-Martin Periodinane (DMP) mediated oxidative rearrangement reaction was uncovered. The reaction proceeds via oxidation of a β-hydroxy thioester to a β-keto thioester, followed by an α-hydroxylation and then further oxidation to form a vicinal thioester tricarbonyl. This product then rearranges, extruding CO2, to form an α-keto product. The mechanism of the rearrangement was elucidated using 13C labelling and analysis of the intermediates as well as the products of the reaction. This efficient process allows for easy preparation of α-keto thioesters which are potential intermediates in the synthesis of pharmaceutically important heterocyclic scaffolds such as quinoxalinones.
- Sanichar, Randy,Carroll, Ciaran,Kimmis, Ryan,Reiz, Bela,Vederas, John C.
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p. 593 - 597
(2018/02/09)
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- Methanol as hydrogen source: Transfer hydrogenation of aromatic aldehydes with a rhodacycle
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A cyclometalated rhodium complex has been shown to perform highly selective and efficient reduction of aldehydes, deriving the hydrogen from methanol. With methanol as both the solvent and hydrogen donor under mild conditions and an open atmosphere, a wide range of aromatic aldehydes were reduced to the corresponding alcohols, without affecting other functional groups.
- Aboo, Ahmed H.,Bennett, Elliot L.,Deeprose, Mark,Robertson, Craig M.,Iggo, Jonathan A.,Xiao, Jianliang
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supporting information
p. 11805 - 11808
(2018/11/10)
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- Ru-Catalyzed Cross-Dehydrogenative Coupling between Primary Alcohols to Guerbet Alcohol Derivatives: With Relevance for Fragrance Synthesis
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A simple method has been developed for the cross dehydrogenative coupling between two different primary alcohols using readily available RuCl2(PPh3)3 as a precatalyst through the borrowing-hydrogen approach. The present methodology is applicable to a large variety of alcohol derivatives including long chain aliphatic alcohols and heteroaryl alcohols. In addition, the methodology was applied in a straightforward protocol to synthesize commercially available fragrances such as Rosaphen and Cyclamenaldehyde in good yields.
- Manojveer, Seetharaman,Salahi, Saleh,Wendt, Ola F.,Johnson, Magnus T.
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p. 10864 - 10870
(2018/09/06)
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- Mild Ring-Opening 1,3-Hydroborations of Non-Activated Cyclopropanes
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The Brown hydroboration reaction, first reported in 1957, is the addition of B?H across an olefin in an anti-Markovnikov fashion. Here, we solved a long-standing problem on mild 1,3-hydroborations of non-activated cyclopropanes. A three-component system including cyclopropanes, boron halides, and hydrosilanes has been developed for borylative ring-opening of cyclopropanes following the anti-Markovnikov rule, under mild reaction conditions. Density functional theory (M06-2X) calculations show that the preferred pathway involves a cationic boron intermediate which is quenched by hydride transfer from the silane.
- Wang, Di,Xue, Xiao-Song,Houk, Kendall N.,Shi, Zhuangzhi
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supporting information
p. 16861 - 16865
(2018/11/27)
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- Reduction and Reductive Deuteration of Tertiary Amides Mediated by Sodium Dispersions with Distinct Proton Donor-Dependent Chemoselectivity
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A practical and scalable single electron transfer reduction mediated by sodium dispersions has been developed for the reduction and reductive deuteration of tertiary amides. The chemoselectivity of this method highly depends on the nature of the proton donor. The challenging reduction via C-N bond cleavage has been achieved using Na/EtOH, affording alcohol products, while the use of Na/NaOH/H2O leads to the formation of amines via selective C-O scission. Sodium dispersions with high specific surface areas are crucial to obtain high yields and good chemoselectivity. This new method tolerates a range of tertiary amides. Moreover, the corresponding reductive deuterations mediated by Na/EtOD-d1 and Na/NaOH/D2O afford useful α,α-dideuterio alcohols and α,α-dideuterio amines with an excellent deuterium content.
- Zhang, Bin,Li, Hengzhao,Ding, Yuxuan,Yan, Yuhao,An, Jie
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p. 6006 - 6014
(2018/05/24)
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- C -Methylation of Alcohols, Ketones, and Indoles with Methanol Using Heterogeneous Platinum Catalysts
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A versatile, selective, and recyclable heterogeneous catalytic method for the methylation of C-H bonds in alcohols, ketones, and indoles with methanol under oxidant-free conditions using a Pt-loaded carbon (Pt/C) catalyst in the presence of NaOH is reported. This catalytic system is effective for various methylation reactions: (1) the β-methylation of primary alcohols, including aryl, aliphatic, and heterocyclic alcohols, (2) the α-methylation of ketones, and (3) the selective C3-methylation of indoles. The reactions are driven by a borrowing-hydrogen mechanism. The reaction begins with the dehydrogenation of the alcohol(s) to afford aldehydes, which subsequently undergo a condensation reaction with the nucleophile (aldehyde, ketone, or indole), followed by hydrogenation of the condensation product by Pt-H species to yield the desired product. In all of the methylation reactions explored in this study, the Pt/C catalyst exhibits a significantly higher turnover number than other previously reported homogeneous catalytic systems. Moreover, it is demonstrated that the high catalytic activity of Pt can be rationalized in terms of the adsorption energy of hydrogen on the metal surface, as revealed by density functional theory calculations on different metal surfaces.
- Siddiki, S. M. A. Hakim,Touchy, Abeda S.,Jamil, Md. A. R.,Toyao, Takashi,Shimizu, Ken-Ichi
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p. 3091 - 3103
(2018/04/14)
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- A KIT FOR DETERMINING THE ABSOLUTE CONFIGURATION OF ALCOHOLS USING A COMPETING ENANTIOSELECTIVE CONVERSION APPROACH
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Provided herein is a kit for the determination of the absolute configuration of alcohols of a competing enantioselective conversion approach.
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Paragraph 0036; 0055
(2018/06/06)
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- Enantioselective Formal α-Methylation and α-Benzylation of Aldehydes by Means of Photo-organocatalysis
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Detailed herein is the photochemical organocatalytic enantioselective α-alkylation of aldehydes with (phenylsulfonyl)alkyl iodides. The chemistry relies on the direct photoexcitation of enamines to trigger the formation of reactive carbon-centered radicals from iodosulfones, while the ground-state chiral enamines provide effective stereochemical control over the radical trapping process. The phenylsulfonyl moiety, acting as a redox auxiliary group, facilitates the generation of radicals. In addition, it can eventually be removed under mild reducing conditions to reveal methyl and benzyl groups.
- Filippini, Giacomo,Silvi, Mattia,Melchiorre, Paolo
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supporting information
p. 4447 - 4451
(2017/04/13)
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- Copper-catalyzed enantioselective hydroboration of unactivated 1, 1-disubstituted alkenes
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We report an efficient and highly enantioselective hydroboration of aliphatic 1, 1-disubstituted alkenes with pinacolborane using a phosphine-Cu catalyst. The method allows facile preparation of enantiomerically enriched β-chiral alkyl pinacolboronates from a range of 1, 1-disubstituted alkenes with high enantioselectivity up to 99% ee. Unprecedented enantiodiscrimination between the geminal alkyl substituents was observed with functional group compatibility in the hydroboration. Furthermore, a catalyst loading as low as 1 mol % furnished the desired product without a decrease in yield or selectivity, demonstrating its efficiency in gram scale synthesis.
- Jang, Won Jun,Song, Seung Min,Moon, Jong Hun,Lee, Jin Yong,Yun, Jaesook
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supporting information
p. 13660 - 13663
(2017/11/07)
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- Determination of the Absolute Configuration of β-Chiral Primary Alcohols Using the Competing Enantioselective Conversion Method
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A method for determining the absolute configuration of β-chiral primary alcohols has been developed. Enantioenriched alcohols were acylated in the presence of either enantiomer of the enantioselective acylation catalyst HBTM, and the faster reaction was determined by measuring product conversion using 1H NMR spectroscopic analysis. An empirical mnemonic was developed that correlates the absolute configuration of the alcohol to the faster reacting catalyst. Successful substrates for this method include primary alcohols that bear a "directing group" on the stereogenic center; directing groups include arenes, heteroarenes, enones, and halides.
- Burns, Alexander S.,Wagner, Alexander J.,Fulton, Jennifer L.,Young, Kyle,Zakarian, Armen,Rychnovsky, Scott. D.
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p. 2953 - 2956
(2017/06/07)
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- Iridium Clusters Encapsulated in Carbon Nanospheres as Nanocatalysts for Methylation of (Bio)Alcohols
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C?H methylation is an attractive chemical transformation for C?C bonds construction in organic chemistry, yet efficient methylation of readily available (bio)alcohols in water using methanol as sustainable C1 feedstock is limited. Herein, iridium nanocatalysts encapsulated in yolk–shell-structured mesoporous carbon nanospheres (Ir@YSMCNs) were synthesized for this transformation. Monodispersed Ir clusters (ca. 1.0 nm) were encapsulated in situ and spatially isolated within YSMCNs by a silica-assisted sol–gel emulsion strategy. A selection of (bio)alcohols (19 examples) was selectively methylated in aqueous phase with good-to-high yields over the developed Ir@YSMCNs. The improved catalytic efficiencies in terms of activity and selectivity together with the good stability and recyclability were contributable to the ultrasmall Ir clusters with oxidation chemical state as a consequence of the confinement effect of YSMCNs with interconnected nanostructures.
- Liu, Qiang,Xu, Guoqiang,Wang, Zhendong,Liu, Xiaoran,Wang, Xicheng,Dong, Linlin,Mu, Xindong,Liu, Huizhou
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p. 4748 - 4755
(2017/12/15)
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- Nickel-Catalyzed Asymmetric Kumada Cross-Coupling of Symmetric Cyclic Sulfates
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Nickel-catalyzed enantioselective cross-couplings between symmetric cyclic sulfates and aromatic Grignard reagents are described. These reactions are effective with a broad range of substituted cyclic sulfates and deliver products with asymmetric tertiary carbon centers. Mechanistic experiments point to a stereoinvertive SN2-like oxidative addition of a nickel complex to the electrophilic substrate.
- Eno, Meredith S.,Lu, Alexander,Morken, James P.
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p. 7824 - 7827
(2016/07/11)
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- Stereocontrolled Syntheses of Seven-Membered Carbocycles by Tandem Allene Aziridination/[4+3] Reaction
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A tandem allene aziridination/[4+3]/reduction sequence converts simple homoallenic sulfamates into densely functionalized aminated cycloheptenes, where the relative stereochemistry at five contiguous asymmetric centers can be controlled through the choice
- Gerstner, Nels C.,Adams, Christopher S.,Tretbar, Maik,Schomaker, Jennifer M.
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supporting information
p. 13240 - 13243
(2016/10/30)
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- Synthesis of Chiral Tertiary Boronic Esters by Oxime-Directed Catalytic Asymmetric Hydroboration
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Chiral boronic esters are useful intermediates in asymmetric synthesis. We have previously shown that carbonyl-directed catalytic asymmetric hydroboration (CAHB) is an efficient approach to the synthesis of functionalized primary and secondary chiral boronic esters. We now report that the oxime-directed CAHB of alkyl-substituted methylidene and trisubstituted alkene substrates by pinacolborane (pinBH) affords oxime-containing chiral tertiary boronic esters with yields up to 87 % and enantiomeric ratios up to 96:4 e.r. The utility of the method is demonstrated by the formation of chiral diols and O-substituted hydroxylamines, the generation of quaternary carbon stereocenters through carbon-carbon coupling reactions, and the preparation of chiral 3,4,4-trisubstituted isoxazolines.
- Shoba, Veronika M.,Thacker, Nathan C.,Bochat, Andrew J.,Takacs, James M.
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supporting information
p. 1465 - 1469
(2016/02/12)
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- Chloride-Bridged Dinuclear Rhodium(III) Complexes Bearing Chiral Diphosphine Ligands: Catalyst Precursors for Asymmetric Hydrogenation of Simple Olefins
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Efficient rhodium(III) catalysts were developed for asymmetric hydrogenation of simple olefins. A new series of chloride-bridged dinuclear rhodium(III) complexes 1 were synthesized from the rhodium(I) precursor [RhCl(cod)]2, chiral diphosphine ligands, and hydrochloric acid. Complexes from the series acted as efficient catalysts for asymmetric hydrogenation of (E)-prop-1-ene-1,2-diyldibenzene and its derivatives without any directing groups, in sharp contrast to widely used rhodium(I) catalytic systems that require a directing group for high enantioselectivity. The catalytic system was applied to asymmetric hydrogenation of allylic alcohols, alkenylboranes, and unsaturated cyclic sulfones. Control experiments support the superiority of dinuclear rhodium(III) complexes 1 over typical rhodium(I) catalytic systems.
- Kita, Yusuke,Hida, Shoji,Higashihara, Kenya,Jena, Himanshu Sekhar,Higashida, Kosuke,Mashima, Kazushi
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supporting information
p. 8299 - 8303
(2016/07/19)
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- Particle size effects in the selective hydrogenation of cinnamaldehyde over supported palladium catalysts
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This work investigated the catalytic performance of palladium catalysts in the selective hydrogenation of α,β-unsaturated aldehydes, and especially the effect of Pd particle size on the hydrogenation of cinnamaldehyde (CAL). An unsupported nanosized Pd catalyst and a series of supported Pd catalysts using supports of activated carbon, SiO2, TiO2, γ-Al2O3, SiC, and graphene oxide were prepared and evaluated in the selective hydrogenation of CAL. Varied sizes of Pd particles could be obtained directly by using different Pd precursors and indirectly by introducing an inactive Ag metal over a γ-Al2O3 supported palladium catalyst. Over a reducible TiO2 support, the Pd particle size can also be controlled indirectly by the effect of strong metal-support interaction (SMSI). Combined with their TEM observations and catalytic tests, density functional theory (DFT) calculations have confirmed that smaller Pd particles favored CC-centered adsorption of CAL leading to a higher selectivity to hydrogenation of the CC bond, forming hydrocinnamaldehyde (HCAL), while on larger ones, the CC-centered adsorption would be partly substituted by CO-centered adsorption resulting in a lowered selectivity to HCAL but an increased selectivity to CO bond hydrogenation, forming hydrocinnamyl alcohol (HCOL). It is clarified that the size dependence of the catalytic selectivity originates from the strong dependence of CC/CO-centered adsorption on Pd particle size. Finally, tests using solvents with different Pd-solvent interactions and α,β-unsaturated aldehydes with remarkable steric effect variations were applied to further regulate the adsorption between palladium and substrate to alter the catalytic activity and selectivity.
- Jiang, Feng,Cai, Jian,Liu, Bing,Xu, Yuebing,Liu, Xiaohao
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p. 75541 - 75551
(2016/08/24)
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- Asymmetric hydrogenation of allylic alcohols using ir?N,P-Complexes
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In this study, a series of γ,γ-disubstituted and β,γ-disubstituted allylic alcohols were prepared and successfully hydrogenated using suitable N,P-based Ir complexes. High yields and excellent enantioselectivities were obtained for most of the substrates studied. This investigation also revealed the effect of the acidity of the N,P?Ir-complexes on the acid-sensitive allylic alcohols. DFT ΔpKa calculations were used to explain the effect of the N,P-ligand on the acidity of the corresponding Ir-complex. The selectivity model of the reaction was used to accurately predict the absolute configuration of the hydrogenated alcohols.
- Li, Jia-Qi,Liu, Jianguo,Krajangsri, Suppachai,Chumnanvej, Napasawan,Singh, Thishana,Andersson, Pher G.
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p. 8342 - 8349
(2018/05/23)
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- Extending the substrate scope of bicyclic p-oxazoline/thiazole ligands for ir-catalyzed hydrogenation of unfunctionalized olefins by introducing a biaryl phosphoroamidite group
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This study identifies a series of Ir-bicyclic phosphoroamidite-oxazoline/thiazole catalytic systems that can hydrogenate a wide range of minimally functionalized olefins (including E- and Z-tri- and disubstituted substrates, vinylsilanes, enol phosphinates, tri- and disubstituted alkenylboronic esters, and ?±,?2-unsaturated enones) in high enantioselectivities (ee values up to 99%) and conversions. The design of the new phosphoroamidite-oxazoline/thiazole ligands derives from a previous successful generation of bicyclic N-phosphane-oxazoline/thiazole ligands, by replacing the N-phosphane group with a p-acceptor biaryl phosphoroamidite moiety. A small but structurally important family of Ir-phosphoroamidite-oxazoline/thiazole precatalysts has thus been synthesized by changing the nature of the Ndonor group (either oxazoline or thiazole) and the configuration at the biaryl phosphoroamidite moiety. The substitution of the N-phosphane by a phosphoroamidite group in the bicyclic N-phosphane-oxazoline/thiazole ligands extended the range of olefins that can be successfully hydrogenated.
- Biosca, Maria,Paptchikhine, Alexander,P??mies, Oscar,Andersson, Pher G.,Di??guez, Montserrat
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supporting information
p. 3455 - 3464
(2015/03/04)
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- NOVEL CHIRAL NITROGEN-PHOSPHORUS LIGANDS AND THEIR USE FOR ASYMMETRIC HYDROGENATION OF ALKENES
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The invention relates to a series of novel chiral nitrogen-phosphorus ligands of formulae (Ia) and (Ib): wherein R1-R3 and X are as defined herein. The invention also relates to chiral metal complexes prepared with these chiral nitrogen-phosphorus ligands. The chiral metal complexes are useful as catalysts for carrying out asymmetric hydrogenation.
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Page/Page column 31; 32; 33
(2015/02/02)
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- From alkenes to alcohols by cobalt-catalyzed hydroformylation-reduction
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The cobalt-catalyzed hydroformylation of alkenes in the presence of a range of novel cyclic phosphine ligands was investigated. The effect of various parameters such as solvents, additives, cobalt/phosphine ratio, CO/H2 (1:2), and nature of the alkenes was examined. The results revealed that both terminal and internal alkenes are hydroformylated in high yields to give mainly linear products at moderate temperature and syn gas pressure. The linearity ranges from 43 to 85%, with Lim-10 giving the highest proportion of linear product.
- Achonduh, George,Yang, Qian,Alper, Howard
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supporting information
p. 1241 - 1246
(2015/03/05)
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- METHOD FOR MANUFACTURING ALCOHOL BY HYDROGENATION OF CARBOXYLIC ACID COMPOUND AND ESTER COMPOUND
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PROBLEM TO BE SOLVED: To provide a method for obtaining alcohol by hydrogenation of carboxylic acid compound efficiently by using a homogeneous system catalyst, especially a method for obtaining alcohol by hydrogenation of various carboxylic acid compound and ester compound by the homogeneous system catalyst efficiently even under alleviation condition. SOLUTION: A carboxylic acid compound and/or an ester compound is hydrogenated in a presence of a rhenium complex represented by ReXmYnZp, where X is a halogen atom, Y is same or different and each a ligand containing one or more phosphorus atom, Z is a ligand other than X and Y, m is an integer of 1 to 6, p is an integer of 0 to 2 and the sum of m, n and p is an integer of 2 to 6, and a specific alkali metal salt. COPYRIGHT: (C)2015,JPOandINPIT
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Paragraph 0117; 0118; 0127; 0129; 0130
(2016/10/10)
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- Systematic methodology for the development of biocatalytic hydrogen-borrowing cascades: Application to the synthesis of chiral α-substituted carboxylic acids from α-substituted α,β-unsaturated aldehydes
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Ene-reductases (ERs) are flavin dependent enzymes that catalyze the asymmetric reduction of activated carbon-carbon double bonds. In particular, α,β-unsaturated carbonyl compounds (e.g. enals and enones) as well as nitroalkenes are rapidly reduced. Conversely, α,β-unsaturated esters are poorly accepted substrates whereas free carboxylic acids are not converted at all. The only exceptions are α,β-unsaturated diacids, diesters as well as esters bearing an electron-withdrawing group in α- or β-position. Here, we present an alternative approach that has a general applicability for directly obtaining diverse chiral α-substituted carboxylic acids. This approach combines two enzyme classes, namely ERs and aldehyde dehydrogenases (Ald-DHs), in a concurrent reductive-oxidative biocatalytic cascade. This strategy has several advantages as the starting material is an α-substituted α,β-unsaturated aldehyde, a class of compounds extremely reactive for the reduction of the alkene moiety. Furthermore no external hydride source from a sacrificial substrate (e.g. glucose, formate) is required since the hydride for the first reductive step is liberated in the second oxidative step. Such a process is defined as a hydrogen-borrowing cascade. This methodology has wide applicability as it was successfully applied to the synthesis of chiral substituted hydrocinnamic acids, aliphatic acids, heterocycles and even acetylated amino acids with elevated yield, chemo- and stereo-selectivity. A systematic methodology for optimizing the hydrogen-borrowing two-enzyme synthesis of α-chiral substituted carboxylic acids was developed. This systematic methodology has general applicability for the development of diverse hydrogen-borrowing processes that possess the highest atom efficiency and the lowest environmental impact. This journal is
- Knaus, Tanja,Mutti, Francesco G.,Humphreys, Luke D.,Turner, Nicholas J.,Scrutton, Nigel S.
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supporting information
p. 223 - 233
(2015/02/19)
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- Synthesis and activity of putative small-molecule inhibitors of the F-box protein SKP2
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The tetrahydropyran 4-(((3-(2,2-dimethyltetrahydro-2H-pyran-4-yl)-4-phenylbutyl)amino)methyl)-N,N-dimethylaniline was reported to disrupt the SCFSKP2 E3 ligase complex. Efficient syntheses of this tetrahydropyran derivative and analogues, including the des-dimethyl derivative 4-(((3-(tetrahydro-2H-pyran-4-yl)-4-phenylbutyl)amino)methyl)-N,N-dimethylaniline, are described. The enantiomers of the des-dimethyl compound were obtained using Evans' chiral auxiliaries. Structure-activity relationships for these tetrahydropyrans and analogues have been determined by measurement of growth-inhibitory activities in HeLa cells, which indicated a non-specific mechanism of action that correlates with inhibitor lipophilicity. However, preliminary data with (R)-and (S)-4-(((3-(tetrahydro-2H-pyran-4-yl)-4-phenylbutyl)amino)methyl)-N,N-dimethylaniline showed enantioselective inhibition of the degradation of p27 in a cell-based assay that acts as a reporter of SKP2 activity.
- Shouksmith, Andrew E.,Evans, Laura E.,Tweddle, Deborah A.,Miller, Duncan C.,Willmore, Elaine,Newell, David R.,Golding, Bernard T.,Griffin, Roger J.
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p. 660 - 679
(2015/04/27)
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