- Synthesis of γ-Haloesters and γ-Ketoesters by Homolytic Addition of Carbon Radicals Generated by α-Haloesters and Triethylborane to Alkenes and Silyl Enol Ethers
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An efficient synthesis of γ-haloesters has been achieved, under very mild conditions, by addition of electrophilic carbon radicals CH(R)CO2Et (R=H, Me, CO2Et) generated by XCH(R)CO2Et (X=Br, I)/BEt3/air in DMSO to alkenes and cycloalkenes.The synthesis of γ-ketoesters is also possible when silyl enol ethers are used as the substrates.
- Baciocchi, Enrico,Muraglia, Ester
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- Photoredox-Catalyzed Isomerization of Highly Substituted Allylic Alcohols by C?H Bond Activation
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Photoredox-catalyzed isomerization of γ-carbonyl-substituted allylic alcohols to their corresponding carbonyl compounds was achieved for the first time by C?H bond activation. This catalytic redox-neutral process resulted in the synthesis of 1,4-dicarbonyl compounds. Notably, allylic alcohols bearing tetrasubstituted olefins can also be transformed into their corresponding carbonyl compounds. Density functional theory calculations show that the carbonyl group at the γ-position of allylic alcohols are beneficial to the formation of their corresponding allylic alcohol radicals with high vertical electron affinity, which contributes to the completion of the photoredox catalytic cycle.
- Guo, Kai,Huang, Jun,Li, Anding,Li, Yuanhe,Yang, Zhen,Zhang, Zhongchao
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p. 11660 - 11668
(2020/05/25)
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- Photocontrolled Cobalt Catalysis for Selective Hydroboration of α,β-Unsaturated Ketones
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Selectivity between 1,2 and 1,4 addition of a nucleophile to an α,β-unsaturated carbonyl compound has classically been modified by the addition of stoichiometric additives to the substrate or reagent to increase their “hard” or “soft” character. Here, we demonstrate a conceptually distinct approach that instead relies on controlling the coordination sphere of a catalyst with visible light. In this way, we bias the reaction down two divergent pathways, giving contrasting products in the catalytic hydroboration of α,β-unsaturated ketones. This includes direct access to previously elusive cyclic enolborates, via 1,4-selective hydroboration, providing a straightforward and stereoselective route to rare syn-aldol products in one-pot. DFT calculations and mechanistic experiments confirm two different mechanisms are operative, underpinning this unusual photocontrolled selectivity switch.
- Beltran, Frédéric,Bergamaschi, Enrico,Funes-Ardoiz, Ignacio,Teskey, Christopher J.
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p. 21176 - 21182
(2020/09/17)
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- First and Highly Stereoselective Synthesis of Both Enantiomers of Octahydroindole-2-phosphonic Acid (OicP)
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We report the first stereoselective synthesis of (2R,3aR,7aR)- and (2S,3aS,7aS)-octahydroindole-2-phosphonic acid 2 (OicP derivatives). The key points are the highly diastereoselective synthesis of cis-fused bicyclic (3aR,7aR)- and (3aS,7aS)-pyrrolidin-2-ones 4 through a dynamic kinetic resolution of racemic γ-keto acid (±)-5 with (R)- and (S)-phenylglycinol via Meyers' bicyclic lactams, and the highly diastereoselective addition of trimethyl phosphite to the N-acyliminium ions 3 obtained from 4.
- Viveros-Ceballos, José Luis,Martínez-Toto, Erick Iván,Eustaquio-Armenta, César,Cativiela, Carlos,Ordó?ez, Mario
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p. 6781 - 6787
(2017/12/07)
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- Biocatalytic access to nonracemic γ-oxo esters: Via stereoselective reduction using ene-reductases
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The asymmetric bioreduction of α,β-unsaturated γ-keto esters using ene-reductases from the Old Yellow Enzyme family proceeds with excellent stereoselectivity and high conversion levels, covering a broad range of acyclic and cyclic derivatives. Various strategies were employed to provide access to both enantiomers, which are versatile precursors of bioactive molecules. The regioselectivity of hydride addition on di-activated alkenes was elucidated by isotopic labeling experiments and showed strong preference for the keto moiety as activating/binding group as opposed to the ester. Finally, chemoenzymatic synthesis of (R)-2-(2-oxocyclohexyl)acetic acid was achieved in high ee on a preparative scale combining enzymatic reduction followed by ester hydrogenolysis.
- Turrini, Nikolaus G.,Cioc, Rǎzvan C.,Van Der Niet, Daan J. H.,Ruijter, Eelco,Orru, Romano V. A.,Hall, Mélanie,Faber, Kurt
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p. 511 - 518
(2017/08/14)
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- NOVEL COMPOUNDS
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Disclosed are novel retinoid-related orphan receptor gamma (RORγ) modulators and their use in the treatment of diseases mediated by RORγ.
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Page/Page column 52
(2015/12/17)
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- Electrochemical reduction of 1-bromomethyl-2-oxocycloalkane-1-carboxylates at silver cathodes in dimethylformamide: One-carbon ring-expansion reactions
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Cyclic voltammetry and controlled-potential (bulk) electrolysis have been employed to investigate the separate electrochemical reductions of methyl 1-bromomethyl-2-oxocyclopentane-1-carboxylate (1) and ethyl 1-bromomethyl-2-oxocyclohexane-1-carboxylate (2) at silver cathodes in dimethylformamide (DMF) containing 0.10 M tetramethylammonium tetrafluoroborate (TMABF4). Oneelectron reductive cleavage of the carbon-bromine bond of each substrate yields a radical intermediate that undergoes a ring-expansion reaction, followed by hydrogen-atom abstraction from the solvent, to afford methyl 3-oxocyclohexane-1-carboxylate (3a) and ethyl 3-oxocycloheptane-1-carboxylate (3b), respectively, in good yield. Each substrate gives rise to three other products: (a) a debrominated analogue of each starting material, (b) a dimeric species formed via radical coupling, and (c) a species possessing an ester group extended by one carbon atom. Electrolyses of 1 and 2 done in the presence of D2O have revealed that carbanion intermediates result in small amounts from two-electron cleavage of carbon-bromine bonds. A mechanistic scheme, involving both radicals and carbanions, is proposed to account for the formation of the various products.
- Wappes, Ethan A.,Mubarak, Mohammad S.,Peters, Dennis G.
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p. G122 - G127
(2015/04/14)
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- Fragmentation of tertiary cyclopropanol compounds catalyzed by vanadyl acetylacetonate
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Tertiary cyclopropanol compounds react with a catalytic amount of vanadyl acetylacetonate in the presence of oxygen affording β-hydroxyketones and β-diketones. For 3-substituted-bicyclo[4.1.0]alkanols, peroxides are obtained, as are the β-hydroxyketones. Conversely, 2- ethoxycarbonylcyclopropyl silyl ethers produce ethyl γ-oxocarboxylate derivatives given the same reaction conditions.
- Kirihara, Masayuki,Kakuda, Hiroko,Ichinose, Motohiro,Ochiai, Yuta,Takizawa, Shinobu,Mokuya, Asuka,Okubo, Kumiko,Hatano, Akihiko,Shiro, Motoo
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p. 4831 - 4839
(2007/10/03)
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- (4, 5, 6, 7-TETRAHYDRO-1-H-INDOL-7-YL) ACETIC ACID DERIVATIVES FOR TREATMENT OF ALZHEIMER'S DISEASE
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Compounds of formula: (I); are disclosed. The compounds are useful in treating or preventing diseases associated with deposition of Aβ in the brain.
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Page/Page column 50
(2008/06/13)
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- 1,4-Conjugate addition of the Reformatsky reagent to α-nitrostyrenes: A new synthesis of γ-nitroesters
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α-Nitrostyrenes react with the Reformatsky reagent to yield the corresponding 1,4-addition products. The reaction represents a practical and convenient route to ethyl 3-aryl-4-nitrobutanoates.
- Menicagli, Rita,Samaritani, Simona
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p. 1425 - 1432
(2007/10/03)
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- Radical cyclization using a thioacetal group for radical generation
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The generation and cyclization of several heterocyclic radicals were investigated. The hydrogen abstraction from 1,3-dithiane, 1,3-dithiolane, and 1,3-oxathiane rings by a benzophenone triplet generated the corresponding heterocyclic radicals, which gave the cyclized products by intramolecular addition to α,β-unsaturated esters. Diastereoselective radical cyclization using chiral acetals was also investigated.
- Nishida, Atsushi,Kawahara, Norio,Nishida, Mayumi,Yonemitsu, Osamu
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p. 9713 - 9734
(2007/10/03)
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- Sequenced reactions with samarium(II) iodide. Tandem intramolecular nucleophilic acyl substitution/intramolecular barbier cyclizations
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Samarium(II) iodide has been employed to promote a tandem intramolecular nucleophilic acyl substitution/ intramolecular Barbier cyclization sequence, generating bicyclic and tricyclic ring systems in excellent yield and high diastereoselectivity. Additionally, a highly versatile ring expansion - cyclization sequence allows entry into several different naturally occurring tricyclic ring systems containing seven- and eight-membered rings.
- Molander, Gary A.,Harris, Christina R.
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p. 3705 - 3716
(2007/10/02)
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- Ring-Chain Tautomerism Provides a Route to 7a-Hydroxy-3a-methyl-2,7-dioxoperhydrobenzofuran. Synthesis of the Hydroxy γ-Lactone Substructure of Myrocin and Other Bioactive Natural Products
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(2-Oxocyclohexyl)acetic acid 10 was converted into bicyclic alkoxy γ-lactones 12a-d via intermediate chloro lactone 11 and alkanolysis.Similarly, lactones 15a,b and 18 were prepared.In contrast, simple ring-chain tautomerism directly afforded the title heterocycle 28, a crystalline, stable and welldefined compound.The angular methyl group seems essential for the spontaneous lactonization. 5,5-Dialkoxy-4-oxocarboxylic acids 26a, b without an angular methyl group did not cyclize to bicyclic hydroxy γ-lactones. - Key Words: Hydroxy lactone, 5-membered, (lactol) tautomer / 4-Oxocarboxylic acids / Keto-cyclol tautomerism.
- Langschwager, Wolf,Hoffmann, H. Martin R.
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p. 797 - 802
(2007/10/02)
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- Facile Control of Regioselectivity in the Reaction of Tin Enolates with α-Halogeno Carbonyls by Additives
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Tin enolates 1 reacted with α-halogeno ketones 2 and esters 10 to give a variety of 1,4-diketones 3 and γ-keto esters 11, respectively, in the presence of appropriate additives such as hexamethylphosphoric triamide (HMPT), tributylphosphine oxide and tetrabutylammonium bromide, while complexation of these additives with tributyltin bromide allowed catalytic production of β-keto oxiranes 4 instead of 3.The reaction mechanism for the preparation of 1,4-diketone 3 is discussed.
- Yasuda, Makoto,Oh-hata, Tatsuhiro,Shibata, Ikuya,Baba, Akio,Matsuda, Haruo
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p. 859 - 866
(2007/10/02)
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- Synthesis and evaluation of cardiotonic activity of simple butenolides II
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Three 3-(2-hydroxy-2-methylcyclohexylmethyl)butanolides were synthesized and checked for inotropic activity.Very weak effects were observed for all of them. cardenolide analogues/ butanolides/ inotropic effects
- Medarde, M.,Caballero, E.,Tome, F.,Garcia, A.,Montero, M.J.,et al.
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p. 887 - 892
(2007/10/02)
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- The alkylation of silyl enol ethers with SN1-unreactive iodides in the presence of silver trifluoroacetate
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Silyl enol ethers can be effectively alkylated with primary n-alkyl iodides in the presence of silver trifluoro-acetate to give monoalkyl ketones.
- Jefford, Charles W.,Sledeski, Adam W.,Lelandais, Patrick,Boukouvalas, John
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p. 1855 - 1858
(2007/10/02)
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- 2-Cyanoaziridinyl-(1)-2-substituted-aziridinyl-(1)-methanes
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A 2-cyanoaziridinyl-(1)-2-substituted-aziridinyl-(1)-methane STR1 wherein R is a nitrile or carbamoyl group, and R1 and R2 each independently is a hydrogen atom, an aliphatic hydrocarbon radical containing up to 10 carbon atoms optionally substituted by hydroxyl, alkoxy, amino, alkylamino, dialkylamino, alkoxycarbonyl, cyano, 1, 2 or 3 halogens, cycloalkyl, phenyl or phenoxy; nitrile, carboxyl, alkoxycarbonyl or optionally hydrogenated monocyclic heteroaryl or phenyl optionally substituted by alkyl, alkoxy, hydroxy, alkoxcarbonyl, dialkylamino, alkylthio, trifluoromethyl, nitro, carbamoyl, nitrile, sulphonamido, hydroxyalkyl, methylenedioxy, or halogen; or R1 and R2, together with the carbon atom to which they are attached, form a ring containing up to 8 ring members of which at least one may be oxygen, sulphur, SO, SO2 NH, N-alkyl, N-acyl or N-alkoxycarbonylalkyl, and which can be substituted by alkyl, alkoxy, hydroxyl, alkylenedioxy, alkoxycarbonyl, hydroxyalkyl, alkoxycarbonylalkyl, dialkylamino, oxo or 2-cyanoaziridino groups, or can be fused to 1 or 2 benzene rings or can be bridged by alkylene radicals containing up to 3 carbon atoms. The compounds are characterized by cytostatic and immune response-stimulating activity.
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- Rearrangements of Oxocyclopropanecarboxylate Esters to Vinyl Ethers. Disparate Behavior of Transition-Metal Catalysts
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Diverse transition-metal compounds catalyze the conversion of 2-alkoxycyclopropanecarboxylate esters to derivative vinyl ethers in high yield under mild conditions.With 2, PtCl2*2PhCN, or 2, structural rearrangement occurs with concurrent epimerization of the reactant cyclopropane compound, and identical isomeric mixtures of vinyl ethers are formed from either of the two stereoisomeric cyclopropane reactants.Rhodium(II) acetate catalyzed reactions occur at higher temperatures than those required with 2, epimerization of the (Z)-cyclopropane isomer, but not the E isomer, is observed, and individual stereoisomeric cyclopropane reactants produce different isomeric mixtures of vinyl ether products.The characteristics of copper bronze and copper(I) chloride catalyzed reactions are generally similar to those of Rh2(OAc)4, except with ethyl 2-methoxy-2-vinylcyclopropanecarboxylate, which undergoes rearrangement to the isomeric ethyl 3-methoxycyclopentenecarboxylates in the presence of these copper catalysts.Participation by the carbethoxy group in rhodium(I)-, platinum (II)-, and ruthenium(II)-catalyzed reactions is indicated in results from comparative reactions with nitrile and sulfone derivatives, and the mechanistic involvement of a six-membered ring metallocycle is suggested.In rhodium(II)- and copper-catalyzed reactions, metallocyclobutane intermediates are proposed to account for their contrasting results.Catalytic rearrangement of (allyloxy)cyclopropanecarboxylate esters affords 3-allyl-4-oxoalkanoate esters in good yield by a synthetic coupling of the oxocyclopropane-vinyl ether and Claisen rearrangement transformations.
- Doyle, Michael P.,Leusen, Daan van
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p. 5326 - 5339
(2007/10/02)
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- Synthesis of β-mercuri ketones by the reaction of siloxycyclopropanes with mercuric acetate and their conversion to α-methylene ketones and γ-ketoesters
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Siloxycyclopropanes were quantitatively converted to β-acetoxymercuri ketones by the reaction with mercuric acetate. Successive treatment with palladium chloride or palladium chloride/carbon monoxide gave α-methylene ketones or γ-ketoesters, respectively, in good yields.
- Ryu, Ilhyong,Matsumoto, Koichi,Ando, Masato,Murai, Shinji,Sonoda, Noboru
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p. 4283 - 4286
(2007/10/02)
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