- Enantioselective α-Arylation of Ketones via a Novel Cu(I)-Bis(phosphine) Dioxide Catalytic System
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A novel catalytic system based on copper(I) and chiral bis(phosphine) dioxides is described. This allows the arylation of silyl enol ethers to access enolizable α-arylated ketones in good yields and enantiomeric excess up to 95%. Noncyclic ketones are amenable substrates with this method, which complements other approaches based on palladium catalysis. Optimization of the ligand structure is accomplished via rational design driven by correlation analysis. Preliminary mechanistic hypotheses are also evaluated in order to identify the role of chiral bis(phosphine) dioxides.
- Escudero-Casao, Margarita,Licini, Giulia,Orlandi, Manuel
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supporting information
p. 3289 - 3294
(2021/04/07)
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- Blue Light Promoted Difluoroalkylation of Aryl Ketones: Synthesis of Quaternary Alkyl Difluorides and Tetrasubstituted Monofluoroalkenes
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A facile and cost-effective method for the preparation of fluoroalkylated compounds has been described by the direct photoexcitation of halofluoroalkanes with blue light absorptivity, enabling the difluoroalkylation of aryl ketones. The methodology has provided an efficient, mild, and catalyst-free synthetic method for quaternary difluoroalkylated arenes and tetrasubstituted monofluoroalkenes.
- Li, Kangkui,Chen, Jingchao,Yang, Chunhui,Zhang, Keyang,Pan, Chunxiang,Fan, Baomin,Fan, Baomin
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supporting information
p. 4261 - 4265
(2020/06/04)
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- NHC-Catalyzed Dual Stetter Reaction: A Mild Cascade Annulation for the Syntheses of Naphthoquinones, Isoflavanones, and Sugar-Based Chiral Analogues
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The N-heterocycle carbene (NHC)-catalyzed dual Stetter cascade reaction is discovered through coupling of β-nitrostyrene with phthalaldehyde under mild conditions to furnish valuable aryl-naphthoquinones. The generality of the new reaction is validated through the development of a C-C and O-C bond forming Stetter cascade reaction using salicylaldehydes to obtain functionalized dihydroisoflavanones. The mild NHC organocatalysis is successfully employed for the construction of optically pure sugar-based naphthoquinones and dihydroisoflavanones. Herein, NHC is found as a unique and powerful organocatalyst to construct homoatomic C-C cross-coupling, heteroatomic O-C bond formation, and cascade cyclization utilizing NO2 as a leaving group at ambient temperature. A mechanistic pathway of the new metal-free catalysis is predicted on the basis of our ESI-MS study of the ongoing reaction and literature.
- Mitra, Rajendra N.,Show, Krishanu,Barman, Debabrata,Sarkar, Satinath,Maiti, Dilip K.
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- Comprehensive evaluation of antioxidant effects of Japanese Kampo medicines led to identification of Tsudosan formulation as a potent antioxidant agent
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Oxidative stress due to the overproduction of reactive oxygen species plays an important role in the pathogenesis of various diseases. In the present study, we comprehensively evaluated the antioxidant activities of 147 oral formulations of Japanese traditional herbal medicines (Kampo medicines), representing the entire panel of oral Kampo medicines listed in the Japanese National Health Insurance Drug List, using in vitro radical scavenging assays, including the 2,2-diphenyl-1-picrylhydrazyl free radical scavenging activity assay, the superoxide anion scavenging activity assay, and the oxygen radical absorption capacity assay. Three of the formulations tested, namely, Tsudosan, Daisaikoto, and Masiningan, showed the most potent in vitro antioxidant activities and were selected for further investigation of their intracellular and in vivo antioxidant effects. The results of the 2′,7′-dichlorodihydrofluorescin diacetate assay demonstrated that all three Kampo medicines significantly inhibited hydrogen peroxide-induced oxidative stress in human hepatocellular liver carcinoma HepG2 cells. In addition, Tsudosan significantly increased the serum biological antioxidant potential values when orally administrated to mice, indicating that it also had in vivo antioxidant activity. The potent antioxidant activity of Tsudosan may be one of the mechanisms closely correlated to its clinical usage against blood stasis.
- Sato, Naoko,Li, Wei,Takemoto, Hiroaki,Takeuchi, Mio,Nakamura, Ai,Tokura, Emi,Akahane, Chie,Ueno, Kanako,Komatsu, Kana,Kuriyama, Noriko,Onoda, Toshihisa,Higai, Koji,Koike, Kazuo
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p. 163 - 172
(2018/11/06)
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- Desulfonylative Methenylation of β-Keto Sulfones
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A one-step strategy for the synthesis of α-methenyl ketones from β-keto sufones is reported. Success of the methodology is elaborated for the synthesis of chromanones and isoflavanones in one-step.
- Pandey, Ganesh,Vaitla, Janakiram
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p. 4890 - 4893
(2015/10/12)
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- Tandem Alkyne Hydroacylation and Oxo-Michael Addition: Diastereoselective Synthesis of 2,3-Disubstituted Chroman-4-ones and Fluorinated Derivatives
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Tandem reactions involving Rh-catalyzed intermolecular hydroacylations of alkynes with salicylaldehydes followed by intramolecular oxo-Michael additions are described for the diastereoselective synthesis of 2,3-disubstituted chroman-4-ones. The tandem hydroacylation/oxo-Michael additions occur to form 2,3-disubstituted chroman-4-ones in high yields from a range of 1,2-disubstituted acetylenes and substituted salicylaldehyes. The resulting 2,3-disubstituted chroman-4-ones are readily fluorinated to form trans-3-fluoro-2,3-disubstituted chroman-4-ones in high yields with excellent diastereoselectivity. (Chemical Equation Presented).
- Du, Xiang-Wei,Stanley, Levi M.
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p. 3276 - 3279
(2015/07/15)
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- Intermolecular C-O addition of carboxylic acids to arynes: Synthesis of o-hydroxyaryl ketones, xanthones, 4-chromanones, and flavones
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An efficient and simple route to biologically and pharmaceutically important o-hydroxyaryl ketones, xanthones, 4-chromanones, and flavones has been developed utilizing readily available carboxylic acids and commercially available o-(trimethylsilyl)aryl tr
- Dubrovskiy, Anton V.,Larock, Richard C.
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p. 2789 - 2798
(2013/03/29)
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- Radical-involved photosynthesis of AuCN oligomers from Au nanoparticles and acetonitrile
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We show here the first radical route for the direct photosynthesis of AuCN oligomers with different sizes and shapes, as evidenced by TEM observations, from an Au nanoparticle/benzaldehyde/CH3CN ternary system in air under UV-light irradiation. This photochemical route is green, mild, and universal, which makes itself distinguishable from the common cyanidation process. Several elementary reaction steps, including the strong C-C bond dissociation of CH3CN and subsequent ?CN radical addition to Au, have been suggested to be critical in the formation of AuCN oligomers based on the identification of ?CN radical by in situ EPR and the radical trapping technique, and other reaction products by GC-MS and 1H NMR, and DFT calculations. The resulting solid-state AuCN oligomers exhibit unique spectroscopic characters that may be a result of the shorter Au-Au distances (namely, aurophilicity) and/or special polymer-like structures as compared with gold cyanide derivatives in the aqueous phase. The nanosized AuCN oligomers supported on mesoporous silica showed relatively good catalytic activity on the homogeneous annulation of salicylaldehyde with phenylacetylene to afford isoflavanones employing PBu3 as the cocatalyst under moderate conditions, which also serves as evidence for the successful production of AuCN oligomers.
- Li, Renhong,Kobayashi, Hisayoshi,Tong, Jiawei,Yan, Xiaoqing,Tang, Yu,Zou, Shihui,Jin, Jiabin,Yi, Wuzhong,Fan, Jie
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p. 18286 - 18294
(2013/01/15)
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- Highly selective palladium-catalyzed direct c-h α-monoarylation of carbonyl compounds using water containing the surfactant polyoxyethylene- α-tocopheryl sebacate (PTS) as a solvent
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Highly selective direct C-H α-monoarylation reactions of 4-chromanones, ketones and 2-phenylacetaldehyde with aryl halides have been performed in satisfactory yields by using a tris(dibenzylideneacetone) dipalladium(0)/tri-tert-butylphosphine tetrafluoroborate catalyst system, potassium bicarbonate as the base and a solvent consisting of pure water containing a small amount of polyoxyethylene-α-tocopheryl sebacate (PTS). Analogous reaction conditions have been employed in a tandem process leading to phenyl-substituted isocoumarins from carbonyl compounds and methyl 2-bromobenzoate.
- Lessi, Marco,Masini, Tiziana,Nucara, Luca,Bellina, Fabio,Rossi, Renzo
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supporting information; scheme or table
p. 501 - 507
(2011/04/15)
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- Convenient synthesis of chromones and quinolinones
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A one pot synthesis of substituted chromones and quinolinones by condensing commercially available and cheaper molecules like salicylic acid and anthranilic acid respectively with alkenes / nitriles followed by insitu cyclization using ammonium acetate as base has been achieved.
- Hemavathi,Naveen,Lokanatha Rai
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p. 409 - 410
(2013/09/24)
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- Homogeneous hydrogenation of electron-deficient alkenes by iridium complexes
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The catalytic homogeneous hydrogenation of electron-deficient alkenes (nucleophilic hydrogenation) was achieved in the presence of iridium complexes and a base as co-catalyst. Contrary to hydrogenation of electron-rich alkenes, which is inactivated by bases, the hydrogenation of the electron-deficient alkenes turned out to be base activated. Here, we present a more thorough study on the capacities but also limitations of this new reaction mechanism using screenings of the reaction conditions as well as different Ir complexes and substrates. The formation of a catalytically active Ir complex is proposed. The active complex usually attacks a soft electron-deficient atom, if more than one possibility exists (as shown by density functional theory computations). Additionally, first examples of enantiomeric enrichments in the presence of chiral Ir complexes are presented. The high catalyst load needed and the moderate yields show that the active complex is very unstable under conditions of nucleophilic hydrogenation and is quickly deactivated, which has to be addressed in further studies. Copyright
- Semeniuchenko, Volodymyr,Exner, Thomas E.,Khilya, Volodymyr,Groth, Ulrich
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experimental part
p. 804 - 809
(2012/03/26)
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- Palladium-catalyzed direct arylation of 4-chromanones: Selective synthesis of racemic isoflavanones and 3,3-diaryl-4-chromanones
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For the first time, the synthesis of racemic isoflavanones has been achieved in satisfactory to good yields and with high selectivity by Pd-catalyzed direct C-3 arylation of 3-unsubstituted 4-chromanones with aryl bromides with the aid of a Pd2(dba)3/tBu 3PHBF4 catalyst system in the presence of KHCO3 as the base in a dioxane/water mixture (4:1). This catalyst system has also been employed in an unprecedented synthesis of 3,3-diaryl-4-chromanones through direct arylation of 4-chromanones in water.
- Bellina, Fabio,Masini, Tiziana,Rossi, Renzo
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experimental part
p. 1339 - 1344
(2010/04/29)
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- Intermolecular C-O addition of carboxylic acids to arynes
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(Figure Presented) A novel, efficient, and expedient route to biologically and pharmaceutically important o-hydroxyaryl ketones, xanthones, 4-chromanones, and flavones has been developed starting from readily available carboxylic acids and commercially available o-(trimethylsilyl)aryl triflates.
- Dubrovskiy, Anton V.,Larock, Richard C.
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supporting information; experimental part
p. 3117 - 3119
(2010/08/22)
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- Catalytic asymmetric alkylation of substituted isoflavanones
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The asymmetric alkylation of isoflavanones (3-aryl-chroman-4-ones) and protected 3-phenyl-2,3-dihydroquinolin-4(1H)-ones catalyzed by a novel cinchonidine-derived phase transfer catalyst E is reported. This functionalization occurs at the unactivated C3 methine to afford novel products that can easily be functionalized to generate more complex fused ring systems. The process accommodates a variety of isoflavanones and activated electrophiles and installs a stereogenic quaternary center in high yield and with good-to-excellent selectivity. Isoflavanones are a privileged class of natural products with a broad spectrum of biological activities including insecticidal, antimicrobial, antibacterial, estrogenic, antitumor, and anti-HIV activity. 1 Isoflavanones are also precursors for more complex natural products such as pterocarpans and rotenones.1 Given their therapeutic promise, selective strategies to access new classes of isoflavanones and related structures has high value.2 The functionalization of the C3 position could promote beneficial interactions with biological targets of interest. Specifically, an alkylation at C3 can rapidly access new members of the general class of biologically active homoisoflavanones.3
- Nibbs, Antoinette E.,Baize, Amanda-Lauren,Herter, Rachel M.,Scheidt, Karl A.
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supporting information; experimental part
p. 4010 - 4013
(2009/12/05)
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- Gold(I)-catalyzed annulation of salicylaldehydes and aryl acetylenes as an expedient route to isoflavanones
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(Chemical Equation Presented) The value of gold 'n' rings: An isoflavanone moiety is the key structural feature of many complex natural products. It is now shown that such structures can be generated efficiently and atom economically by the annulation of
- Skouta, Rachid,Li, Chao-Jun
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p. 1117 - 1119
(2008/03/14)
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- Rapid syntheses of (±)-pterocarpans and isoflavones via the gold-catalyzed annulation of aldehydes and alkynes
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(±)-Pterocarpan and analogues (4a-c) have been synthesized efficiently via the annulation of salicylaldehydes (1a, 1b and 1c) and o-methoxymethoxylphenylacetylene (2a), followed by a one-pot reduction and acidic cyclization of the ketones (3a-c). In addition, isoflavone derivatives (5a-c) have been synthesized rapidly, in two steps, via the annulation of salicylaldehyde (1a) and arylacetylenes (2b, 2c and 2d), followed by IBX/DMSO oxidation of the isoflavanones (3d, 3e and 3f).
- Skouta, Rachid,Li, Chao-Jun
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p. 8343 - 8346
(2008/03/14)
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- Organolead-mediated Arylation of Allyl β-Ketoesters: A Selective Synthesis of Isoflavanones and Isoflavones
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Arylation of A-ring substituted and unsabstituted 3-allyloxycarbonylchroman-4-ones with aryllead(IV) triacetates followed by selective catalytic deallyloxycarbonylation affords isoflavanones or isoflavones in high overall yields.The highest yield in the arylation step was observed in the reaction of 5,7-dimethoxychroman-4-one with the more hindered 2,4,6-trimethoxyphenyllead triacetate.
- Donnelly, Dervilla M.,Finet, Jean-Pierre,Rattigan, Bernard A.
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p. 1729 - 1736
(2007/10/02)
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- Ligand Coupling Route to Isoflavanones and Isoflavones
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Phenylation of 3-phenylsulfonylchroman-4-ones using Ph3BiCO3 leading to the synthesis of isoflavanones and isoflavones is reported.
- Santhosh, K. C.,Balasubramanian, K. K.
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p. 224 - 225
(2007/10/02)
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- PALLADIUM CATALYSED ARYLATION OF CHROM-3-EN-4-OL ACETATES VIA THEIR TRIBUTYLTIN ENOLATES
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Arylation of in situ generated chrom-3-en-4-ol tributyltin enolates with aryl bromide in the presence of a catalytic amount of PdCl22 gives moderate to good yields of the corresponding isoflavanones.
- Donnelly, Dervilla M.X.,Finet, Jean-Pierre,Stenson, Paul H.
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- Use of Nitrile Oxides in Synthesis. A Novel Synthesis of Chalcones, Flavanones, Flavones and Isoflavones
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Novel methodology is developed for a three-step synthesis of chalcones, flavanones, flavones and isoflavones. 1.Salicylaldoxime is chlorinated to the corresponding hydroxamoyl chloride in the presence of pyridine, and cycloadded to styrene and phenylacetylene. 2.The isoxazole derivatives formed are reductively cleaved over Raney-Ni to β-hydroxyketones or 1,3 diketones. 3.Acid-catalyzed cyclization gives the flavonoids.Use of ω-methoxy- or ω-dialkylamino-substituted styrenes (enamines) leads regioselectively to 4-aryl-substituted isoxazoles and derived isoflavones.
- Thomsen, Ib,Torssell, Kurt B. G.
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p. 303 - 308
(2007/10/02)
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- Reaction of Dimethyl Sulphoxide and Acetic Anhydride with 3-Substituted 4-Hydroxycoumarins
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The DMSO-Ac2O reagent reacts with 4-hydroxy-3-phenylcoumarin to give 3-(2-hydroxyphenyl)-2-phenyl-1-thiomethylpropan-3-one (1a) and 6H,11H-benzopyranobenzopyran-11-one (3).A similar reaction of 3-allyl-4-hydroxycoumarin gives 2-allyl-3-(2-hydroxyphenyl)-1-thiomethylpropan-3-one (1b).However, the same reagent, when modified by prior heating, reacts with 6H,7H-7-(4-hydroxy-3-coumaranyl)benzopyranobenzopyran-6-one (7a) to give dicoumarol, 7-thiomethyl-6H,7H-benzopyranobenzopyran-6-one (8) and 4-hydroxy-3-methylthiomethoxy-2H-benzopyran-2-one (10).
- Khan, Khaliquz Zaman,Tasneem, Khalida,Rahman, Mujeebur,Prakash, Satya,Zaman, Asif
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