- Synthetic and Mechanistic Studies on the Rhodium-Catalyzed Redox Isomerization of Cyclohexa-2,5-dienols
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We report the application of cyclohexa-2,5-dienols in a catalytic redox isomerization: a rhodium-catalyzed desymmetrization for the synthesis of Υ,Υ-disubstituted cyclohexenones. The reaction generates products which are useful intermediates in organic sy
- Kress, Steffen,Johnson, Thomas,Weisshar, Florian,Lautens, Mark
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- Rhodium-Catalyzed Desymmetric Arylation of γ,γ-Disubsituted Cyclohexadienones: Asymmetric Synthesis of Chiral All-Carbon Quaternary Centers
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The desymmetric arylation of prochiral cyclohexadienones with ArZnCl in the presence of an (R)-segphos-rhodium catalyst gave high yields of the corresponding cyclohexenones, which contain a chiral arylated carbon center at the β-position and a chiral all-carbon quaternary center at the γ-position, with high diastereo- and enantioselectivities. This catalytic system was also applied to the arylation of spirocarbocyclic cyclohexadienones and afforded the corresponding cyclohexenones bearing a chiral spiro quaternary carbon with high dr and ee.
- Qiao, Yu,Bai, Shiming,Wu, Xiao-Feng,Yang, Ying,Meng, He,Ming, Jialin
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p. 1556 - 1560
(2022/02/23)
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- The Silicon-Hydrogen Exchange Reaction: A Catalytic σ-Bond Metathesis Approach to the Enantioselective Synthesis of Enol Silanes
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The use of chiral enol silanes in fundamental transformations such as Mukaiyama aldol, Michael, and Mannich reactions as well as Saegusa-Ito dehydrogenations has enabled the chemical synthesis of enantiopure natural products and valuable pharmaceuticals. However, accessing these intermediates in high enantiopurity has generally required the use of either stoichiometric chiral precursors or stoichiometric chiral reagents. We now describe a catalytic approach in which strongly acidic and confined imidodiphosphorimidates (IDPi) catalyze highly enantioselective interconversions of ketones and enol silanes. These "silicon-hydrogen exchange reactions"enable access to enantiopure enol silanes via tautomerizing σ-bond metatheses, either in a deprotosilylative desymmetrization of ketones with allyl silanes as the silicon source or in a protodesilylative kinetic resolution of racemic enol silanes with a carboxylic acid as the silyl acceptor.
- Zhou, Hui,Bae, Han Yong,Leutzsch, Markus,Kennemur, Jennifer L.,Bécart, Diane,List, Benjamin
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supporting information
p. 13695 - 13700
(2020/08/24)
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- Strong and Confined Acids Control Five Stereogenic Centers in Catalytic Asymmetric Diels–Alder Reactions of Cyclohexadienones with Cyclopentadiene
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We describe a highly enantioselective Diels–Alder reaction of cross-conjugated cyclohexadienones with cyclopentadiene, in which five stereocenters are effectively controlled by a strongly acidic and confined imidodiphosphorimidate catalyst. Our approach provides tricyclic products in excellent stereoselectivity. We also report methods to convert the obtained products into useful intermediates and a computational study that aids in gaining deeper insight into the reaction mechanism and origin of stereoselectivity.
- Bistoni, Giovanni,Das, Sayantani,De, Chandra Kanta,Ghosh, Santanu,Leutzsch, Markus,List, Benjamin,Neese, Frank,Yepes, Diana
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supporting information
p. 12347 - 12351
(2020/03/23)
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- Nickel-Catalyzed Desymmetric Hydrogenation of Cyclohexadienones: An Efficient Approach to All-Carbon Quaternary Stereocenters
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Nickel-catalyzed desymmetric hydrogenation has been achieved. With the Ni(OTf)2/(S,S)-Ph-BPE system, a series of ?,?-disubstituted cyclohexadienones were transformed to the corresponding cyclohexenones with a chiral all-carbon quaternary center at the γposition in high yields (92-98%) and excellent enantioselectivities (92%-99% ee). This catalytic system can also tolerate the desymmetric reaction of spirocarbocyclic cyclohexadienones to produce the corresponding cyclohexenones bearing a chiral spiro quaternary carbon with high yields (94%-98%) and ee values (96%-99% ee). Furthermore, this methodology provides an efficient and concise synthetic route to the intermediate of natural products cannabispirenones A and B.
- You, Cai,Li, Xiuxiu,Gong, Quan,Wen, Jialin,Zhang, Xumu
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supporting information
p. 14560 - 14564
(2019/10/11)
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- Asymmetric Synthesis of Remote Quaternary Centers by Copper-Catalyzed Desymmetrization: An Enantioselective Total Synthesis of (+)-Mesembrine
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Catalytic asymmetric syntheses of remote quaternary stereocenters have been developed by copper-catalyzed 1,4-hydrosilylation of ?,?-disubstituted cyclohexadienones. A variety of cyclohexenones have been synthesized in good yield and excellent enantioselectivity. Versatile 2-silyloxy diene intermediates bearing ?,?-disubstituted all carbon stereogenic centers can be isolated from the mild reaction conditions. The utility of this strategy is exemplified in a catalytic asymmetric total synthesis of (+)-mesembrine.
- Bokka, Apparao,Mao, James X.,Hartung, John,Martinez, Steven R.,Simanis, Justin A.,Nam, Kwangho,Jeon, Junha,Shen, Xiaoqiang
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supporting information
p. 5158 - 5162
(2018/09/13)
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- Palladium-Catalyzed α-Arylation of Vinylogous Esters for the Synthesis of γ,γ-Disubstituted Cyclohexenones
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A palladium-catalyzed α-arylation of cyclic vinylogous esters to form products that are converted in one step to γ-alkyl-γ-aryl-substituted cyclohexenones is reported. This Pd-catalyzed reaction proceeds at room temperature, is generally high-yielding, and uses an amount of a commercially available catalyst as low as 0.25 mol %. The scope of aryl bromides is particularly broad, and alkenyl bromides can also be used. This two-step protocol, comprising α-arylation and reductive transposition, can be performed in one pot and is applicable to gram-scale synthesis.
- Johnson, Thomas,Pultar, Felix,Menke, Friedericke,Lautens, Mark
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p. 6488 - 6491
(2016/12/23)
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- Asymmetric Induction at Remote Quaternary Centers of Cyclohexadienones by Rhodium-Catalyzed Conjugate Hydrosilylation
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The enantioselective desymmetrizing conjugate hydrosilylation of prochiral differently γ,γ-disubstituted cyclohexadienone derivatives 2 to furnish the corresponding cyclohexenones 4 with a remote chiral all-carbon quaternary center at the γ position is de
- Naganawa, Yuki,Kawagishi, Mayu,Ito, Jun-Ichi,Nishiyama, Hisao
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p. 6873 - 6876
(2016/06/13)
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- Palladium-catalyzed γ-arylation of β,γ-unsaturated ketones: Application to a one-pot synthesis of tricyclic indolines
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(Chemical Equation Presented) Indolines in short order: A catalyst system which allows for efficient γ-arylation of β,γ-unsaturated ketones is described (see scheme; dippf = 1,1′-bis(diisopropylphosphanyl) ferrocene, dba = trans,transdibenzylideneacetone). This method can be applied to a one-pot, two-step synthesis of polycyclic indolines from simple starting materials.
- Hyde, Alan M.,Buchwald, Stephen L.
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p. 177 - 180
(2008/09/18)
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- Indazole or indole derivatives, and use thereof in human medicine and more particularly in oncology
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The present invention relates to novel compounds derived from indazoles or indoles of formula (1) or formula (2), to methods for treating tumors or cancerous cells with compounds of formula (1) or formula (2) and to pharmacaetutical compositions comprisin
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- Novel synthesis of 2-aryl or 4-arylcyclohexenones
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In anhydrous HF, 4-hydroxy-4-methylcyclohex-2-en-1-one 5 reacts with aromatics (benzene, toluene, anisole, para-bromoanisole) to yield 2 and 4 arylated ketones.Reaction with benzene yields enone 2 (73percent).With toluene, reaction affords enone 6 (24perc
- Berrier, C.,Gaillard, E.,Jacquesy, J. C.,Jouannetaud, M. P.,Kigabo, F.
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p. 537 - 543
(2007/10/02)
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- Chemistry of 2-Methoxy-2,5-cyclohexadienone. V. Photochemical Rearrangement and Oxidation of 2-Methoxy-4-methyl-4-phenyl-2-cyclohexenone and 2-Methoxy-4-methyl-4-phenyl-2,5-cyclohexadienone
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A methanolic solution of 2-methoxy-4-methyl-4-phenyl-2-cyclohexenone (I) was irradiated with a 100 W mercury lamp to give 4-methyl-4-phenyl-2-cyclohexenone (III) and 1-methoxy-5-methyl-6-phenylbicyclohexan-2-one (IV).When a benzene solution of I wa
- Matoba, Katsuhide,Noda, Hiroko,Yamazaki, Takao
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p. 2627 - 2634
(2007/10/02)
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- Intramolecular C-H Insertions of Alkylidenecarbenes. 2. Stereochemistry and Isotope Effects
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The stereochemistry of the intramolecular 1,5 carbon-hydrogen insertion reaction of alkylidenecarbenes to form cyclopentenes has been determined.The isotope effects for two intramolecular examples of insertion reactions of this class of carbenes have been
- Gilbert, John C.,Giamalva, David H.,Baze, Mark E.
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p. 2557 - 2563
(2007/10/02)
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- Diprotonation de derives phenoliques. Application a' la preparation de phenyl-3 et de phenyl-4 cyclohexenones
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Monocyclic phenols 1-3a (and their methyl ethers) react readily with benzene, in superacid SbF5-HF.In these experiments 4,4 disubstituted cyclohexenones (5, 8 and 11) are the only primary products of the reaction.Their formation is best explain
- Jacquesy, Jean-Claude,Jouannetaud', Marie-Paulf
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p. 267 - 274
(2007/10/02)
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- Geminal Acylation-Alkylation at a Carbonyl Carbon via Regiospecifically Generated Metalloenamines
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A useful procedure for effecting geminal disubstitution at the carbonyl carbon atom of aldehydes and ketones has been developed in which the sequence of reactions results in the replacement of the two carbon-oxygen bonds of the carbonyl function with an acyl group and an alkyl or hydroxyalkyl group.Of particular importance is the facile application of these procedures to the efficient construction of quaternary carbon atoms that bear alkyl appendages containing differentiated functionality.This novel methodology features the initial conversion of carbonyl compounds 1 into the substituted 2-azadienes 10 or 11 by Wittig-Horner reaction.Subsequent reaction of these 2-azadienes produced in situ with n-butyllithium results in the formation of the metalloenamines 12 and 13 (R4 = n-Bu) which undergo reactions with a wide variety of electrophiles to give, after hydrolysis of the intermediate imines, the α-substituted aldehydes 14 or the α-substituted ketones 15 in good of excellent overall yields.New procedures for the annelation of cyclopentenones such as 22 and cyclohexenones 26 at the carbonyl carbon of ketones are described as is an important variant of a directed aldol reaction, 1 --> 28.Although a number of individual manipulations are necessary to effect the geminal disubstitution of a carbonyl functional group, it is generally feasible to execute the entire sequence of reactions in single flask, thereby rendering this methodology very convenient to implement in practice.
- Martin, Stephen F.,Phillips, Gerald W.,Puckette, Thomas A.,Colapret, John A.
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p. 5866 - 5872
(2007/10/02)
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