- Highly Selective Hydrogenation of C═C Bonds Catalyzed by a Rhodium Hydride
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Under mild conditions (room temperature, 80 psi of H2) Cp*Rh(2-(2-pyridyl)phenyl)H catalyzes the selective hydrogenation of the C═C bond in α,β-unsaturated carbonyl compounds, including natural product precursors with bulky substituents in the β position and substrates possessing an array of additional functional groups. It also catalyzes the hydrogenation of many isolated double bonds. Mechanistic studies reveal that no radical intermediates are involved, and the catalyst appears to be homogeneous, thereby affording important complementarity to existing protocols for similar hydrogenation processes.
- Gu, Yiting,Lisnyak, Vladislav G.,Norton, Jack R.,Salahi, Farbod,Snyder, Scott A.,Zhou, Zhiyao
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supporting information
p. 9657 - 9663
(2021/07/19)
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- Borane-Catalyzed, Chemoselective Reduction and Hydrofunctionalization of Enones Enabled by B-O Transborylation
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The use of stoichiometric organoborane reductants in organic synthesis is well established. Here these reagents have been rendered catalytic through an isodesmic B-O/B-H transborylation applied in the borane-catalyzed, chemoselective alkene reduction and formal hydrofunctionalization of enones. The reaction was found to proceed by a 1,4-hydroboration of the enone and B-O/B-H transborylation with HBpin, enabling catalyst turnover. Single-turnover and isotopic labeling experiments supported the proposed mechanism of catalysis with 1,4-hydroboration and B-O/B-H transborylation as key steps.
- Nicholson, Kieran,Langer, Thomas,Thomas, Stephen P.
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p. 2498 - 2504
(2021/04/13)
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- Cu(I) mediated hydrogen borrowing strategy for the α-alkylation of aryl ketones with aryl alcohols
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Abstract: New triazolium Schiff bases (TSBs) were synthesised via a simple and high throughput process. The new salts were successfully characterised. When reacted with Cu(CH3CN)4PF6, the TSB salts formed mononuclear triazole Schiff base copper(I) complexes and dinuclear complexes that were also characterised. The?copper complexes were generated in situ (mixtures of TSB salts with Cu(CH3CN)4PF6) and applied as homogeneous catalysts for the C–C coupling of a variety of aryl ketones with aryl alcohols, from which?significant reactivity was observed. Reaction conditions were optimised, and the results indicate that the catalyst systems are very robust. A catalyst concentration of 10?mol% efficiently and selectively catalysed the α-alkylation of methyl phenyl ketone and its derivatives to afford up to 94% yield of 1,3-diphenylpropan-1-one and its analogues. The process is adaptable with analogues of acetophenone and benzyl alcohol bearing various regulating substituents tolerated. Graphic abstract: [Figure not available: see fulltext.].
- Lawal, Nasir S.,Ibrahim, Halliru,Bala, Muhammad D.
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p. 275 - 285
(2021/02/09)
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- Preparation method of novel aromatic ketone compound
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The invention discloses a preparation method of a novel aromatic ketone compound. According to the preparation method, an aromatic carboxylic acid compound and an aromatic olefin compound are used asreaction raw materials, triphenylphosphine is taken as a deoxidizing reagent, Methylenene blue is taken as a photocatalyst, stirring and reacting are carried out at room temperature in an N,N-dimethylacetamide solvent under the irradiation of a white light lamp in a nitrogen atmosphere and under the condition of taking 2,4,6-trimethylpyridine as an alkali, thereby obtaining a target product, namely the aromatic ketone compound. The method has the advantages of mild reaction conditions, simplicity in operation, low cost, convenience in purification, environmental friendliness and the like.
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Paragraph 0027-0028
(2020/12/08)
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- Structure-activity relationship study of antitrypanosomal chalcone derivatives using multivariate analysis
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Chagas disease represents one of several neglected diseases with a reduced number of chemotherapeutical drugs including the highly toxic compounds benznidazole and nifurtimox. In this sense, natural products represent an import scaffold for the discovery of new biologically active compounds, in which chalcones are promising representatives due to their antitrypanosomal potential. In this work, a series of 36 chalcone derivatives were synthesized and tested against trypomastigotes of Trypanosoma cruzi. In addition, a detailed investigation on their molecular features was performed. The obtained results suggest that certain molecular features are fundamental for an efficient antitrypanosomal potential of chalcones, such as allylic groups, α,β-unsaturated carbonyl system, and aromatic hydroxyl groups. These results were obtained based on the interpretation of machine-learning and multivariate statistical methods, which revealed the essential characteristics of chalcone prototypes against trypomastigotes of T. cruzi.
- Gomes, Kaio S.,da Costa-Silva, Thais A.,Oliveira, Igor H.,Aguilar, Andrea M.,Oliveira-Silva, Diogo,Uemi, Miriam,Silva, Wender A.,Melo, Lennine R.,Andrade, Carlos Kleber Z.,Tempone, Andre G.,Baldim, Jo?o L.,Lago, Jo?o Henrique G.
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supporting information
p. 1459 - 1462
(2019/04/17)
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- Synthesis and Structures of Arene Ruthenium (II)–NHC Complexes: Efficient Catalytic α-alkylation of ketones via Hydrogen Auto Transfer Reaction
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A panel of six new arene Ru (II)-NHC complexes 2a-f, (NHC?=?1,3-diethyl-(5,6-dimethyl)benzimidazolin-2-ylidene 1a, 1,3-dicyclohexylmethyl-(5,6-dimethyl)benzimidazolin-2-ylidene 1b and 1,3-dibenzyl-(5,6-dimethyl)benzimidazolin-2-ylidene 1c) were synthesized from the transmetallation reaction of Ag-NHC with [(η6-arene)RuCl2]2 and characterized. The ruthenium (II)-NHC complexes 2a-f were developed as effective catalysts for α-alkylation of ketones and synthesis of bioactive quinoline using primary/amino alcohols as coupling partners respectively. The reactions were performed with 0.5?mol% catalyst load in 8?h under aerobic condition and the maximum yield was up to 96%. Besides, the different alkyl wingtips on NHC and arene moieties were studied to differentiate the catalytic robustness of the complexes in the transformations.
- Balamurugan, Gunasekaran,Balaji, Sundarraman,Ramesh, Rengan,Bhuvanesh, Nattamai S.P.
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- Rapid and regioselective hydrogenation of α,β-unsaturated ketones and alkylidene malonic diesters using Hantzsch ester catalyzed by titanium tetrachloride
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A regioselective hydrogenation of α,β-unsaturated ketones and alkylidene malonic diesters using Hantzsch ester as the reducing agent and titanium tetrachloride as a catalyst is described. The short reaction times and mild reaction conditions are the advantages of this method. Georg Thieme Verlag Stuttgart New York.
- Che, Jun,Lam, Yulin
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experimental part
p. 2415 - 2420
(2010/11/19)
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- Efficient chemoselective biohydrogenation of 1,3-diaryl-2-propen-1-ones catalyzed by Saccharomyces cerevisiae yeasts in biphasic system
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A series of chalcones (1-9) was synthesized by base catalyzed aldol condensation with 50-94% yields. These α,β-unsaturated carbonyl compounds were used as substrates in biotransformation reactions mediated by three industrial Saccharomyces cerevisiae strains in biphasic systems. Several reaction parameters were evaluated, such as yeast concentration, temperature, pH, substrate concentration, organic solvent, volume of aqueous and organic phases and the influence of substituent groups on chalcones 1-9. The biotransformation was chemoselective and formed only the corresponding saturated ketones. The highest conversion (>99%) to the dihydrochalcone was obtained at 30-45°C and pH above 5.5, while the cellular and substrate concentrations also showed a strong influence on the biohydrogenation reaction. Organic solvents with log. P >3.2 (hexane or heptane) were the most appropriate, and 40-80% of aqueous phase allowed the highest conversions probably by maintaining the yeast enzymes catalytically active. The influence of substituents on rings A and B of chalcones 1-9 was low and no correlation between the donor or withdrawing electron groups was observed.
- Silva, Vanessa Dutra,Stambuk, Boris Ugarte,Nascimento, Maria da Graca
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experimental part
p. 157 - 163
(2010/10/19)
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- Thienopyrimidine ureas as novel and potent multitargeted receptor tyrosine kinase inhibitors
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A series of novel thienopyrimidine-based receptor tyrosine kinase inhibitors has been discovered. Investigation of structure-activity relationships at the 5- and 6-positions of the thienopyrimidine nucleus led to a series of N,N′-diaryl ureas that potentl
- Dai, Yujia,Guo, Yan,Frey, Robin R.,Ji, Zhiqin,Curtin, Michael L.,Ahmed, Asma A.,Albert, Daniel H.,Arnold, Lee,Arries, Shannon S.,Barlozzari, Teresa,Bauch, Joy L.,Bouska, Jennifer J.,Bousquet, Peter F.,Cunha, George A.,Glaser, Keith B.,Guo, Jun,Li, Junling,Marcotte, Patrick A.,Marsh, Kennan C.,Moskey, Maria D.,Pease, Lori J.,Stewart, Kent D.,Stoll, Vincent S.,Tapang, Paul,Wishart, Neil,Davidsen, Steven K.,Michaelides, Michael R.
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p. 6066 - 6083
(2007/10/03)
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- NAD(P)+-NAD(P)H Models. 64. The Quantitative Elucidation of the Mechanistic Aspects in the Silica Gel-Catalyzed Reduction of α,β-Unsaturated Carbonyl Compounds by a Model of NAD(P)H
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Eight α,β-unsaturated carbonyl compounds, 1-(2'- or 4'-substituted phenyl)-3-phenyl-2-propen-1-ones (2'-or 4'-substituted chalcones), were subjected to the reduction by an NAD(P)H model in the presence of silica gel in benzene.All of these afforded quantitatively the corresponding saturated carbonyl compounds, whereas no 1,2-reduction took place.For 2'-methoxy, 4'-methyl, 4'-bromo, and 4'-nitro derivatives as well as the unsubstituted carbonyl compound, the apparent reactivity of the substrate increases with the increase in electronwithdrawing ability of the substituent, whereas the degree of the adsorption onto the surface of silica gel decreases.It is also apparent that the 4'-hydroxy derivative exerts lower reactivity than the 2'-hydroxy derivative in spite of much more efficient adsorption of the former.In order to uniformly interpret the apparent results, the data obtained were quantitatively analyzed in terms of kinetics as well as equilibrium constants for the adsorption of the substrates onto the surface of silica gel.It has been revealed that the silanol group on the surface of silica gel acts as a general-acid catalyst in the reduction.
- Yasui, Shinro,Fujii, Masayuki,Ohno, Atsuyoshi
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p. 4019 - 4026
(2007/10/02)
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- Selective Hydrogenation of Carbon-Carbon Double bonds of Chalcones by Corynebacterium equi IFO 3730
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1,3-Diphenyl-2-propen-1-one (chalcone) was selectively hydrogenated at the carbon-carbon double bond on incubation with Corynebacterium equi IFO 3730. to give the corresponding saturated ketone, 1,3-diphenyl-1-propanone.Practically no alcoholic compounds were detected in the reaction mixture.This highly selective hydrogenation reaction was also successful with substrates having substituents on aromatic rings.On the other hand, two hydrogen atoms on the olefinic carbons were essential, because substitution of either one of the hydrogens by a methyl group completely inhibited the reaction.
- Ohta, Hiromichi,Konishi, Jin,Tsuchihashi, Gen-ichi
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p. 665 - 670
(2007/10/02)
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- SELECTIVE HYDROGENATION OF CARBON-CARBON DOUBLE BONDS OF CHALCONES BY THE AID OF A MICROORGANISM
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Chalcone and substituted chalcones are selectively hydrogenated on C=C double bonds by incubation with Corynebacterium equi IFO 3730, to give the corresponding saturated ketones.
- Ohta, Hiromichi,Konishi, Jin,Tsuchihashi, Gen-ichi
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p. 1895 - 1896
(2007/10/02)
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- Acylations and Alkylations of an Ester Enolate in High Yield at Room Temperature on Polystyrene Supports
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Polymer-bound esters of 3-phenylpropanoic acid are converted to enolates at room temperature and acylated and alkylated in 73-87percent isolated yields with little or no self-condensation of ester.
- Chang, Young H.,Ford, Warren T.
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p. 3756 - 3758
(2007/10/02)
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- Use of Highly Cross-Linked Polystyrene Supports for Acylation and Alkylation of an Ester Enolate at Room Temperature
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The enolate of polystyrene-bound 3-phenylpropanoic ester is prepared with (triphenylmethyl)lithium in tetrahydrofuran at room temperature and is trapped with carboxylic acid chlorides and alkyl bromides.Gas chromatographic yields exceed 90percent, and isolated yields are 73-87percent with a partially esterified 10percent divinylbenzene-cross-linked gel copolymer containing 0.67 mmol of ester/g of copolymer.Yields of p-nitrobenzoylation and self-condensation depend upon the degree of cross-linking of the polystyrene support, the gel or macroporous morphology of the polymer, the degree of functionalization of the polymer, the percent conversion of the chloromethyl polystyrene to ester, the structure of the base used to form the enolate, the time between enolate generation and trapping with p-nitrobenzoyl chloride, and the temperature.Yields of acylation product increase, and self-condensation of the ester decreases as percent cross-linking increases from 2percent to 20percent and as the concentration of ester in fully esterified polymers decreases from 1.08 to 0.18 mmol/g of polymer.When the original esterification of the polymer is carried to only partial conversion, the subsequent enolate acylation yields increase, conversion, the subsequent enolate acylation yields increase, self-condensation yields decrease, and unreacted ester yields decrease.Macroporous 20percent cross-linked polymers gave better site isolation than 10percent cross-linked gel polymers but lacked the physical stability necessary for recycling.One sample of 10percent cross-linked gel polymer in three esterification/enolate acylation/hydrolysis cycles showed no decrease in acylation yield but a decrease in the degree of functionalization.The higher degrees of cross-linking and functionalization of the polystyrene in this work than in similar experiments with a conventional 2percent cross-linked polystyrene enable ester enolate acylation in 77percent yield at room temperature on a 0.1-mol scale in just 1400 mL of reaction mixture.
- Chang, Young H.,Ford, Warren T.
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p. 5364 - 5371
(2007/10/02)
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