- Iodine-catalyzed tandem oxidative aromatization for the synthesis of meta-substituted alkoxybenzenes
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A rapid method for the synthesis of meta-substituted alkoxybenzenes is achieved by oxidation of cyclohexenones. This one-pot transformation is catalyzed by molecular iodine with DDQ as an oxidant in the presence of alcohols. Diverse cyclohexenones with aryl or alkyl substitutes are well tolerated to the mild oxidative conditions affording desired products in up to 92% yield. These oxidizing processes were applicable to the efficient synthesis of useful meta-substituted phenolic products which are difficult to obtain by traditional electrophilic substitutions.
- Jiang, Dahong,Jia, Xicheng,Zhang, Shuhua,Zhang, Zhihua,Li, Lei,Qiao, Yanhui
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- Access to Functionalized Quaternary Stereocenters via the Copper-Catalyzed Conjugate Addition of Monoorganozinc Bromide Reagents Enabled by N, N-Dimethylacetamide
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Monoorganozinc reagents, readily obtained from alkyl bromides, display excellent reactivity with β,β-disubstituted enones and TMSCl in the presence of Cu(I) and Cu(II) salts to synthesize a variety of cyclic functionalized β-quaternary ketones in 38-99% yields and 9:1-20:1 diastereoselectivities. The conjugate addition features a pronounced improvement in DMA using monoorganozinc bromide reagents. A simple one-pot protocol that harnesses in situ generated monoorganozinc reagents delivers comparable product yields.
- Fulton, Tyler J.,Alley, Phebe L.,Rensch, Heather R.,Ackerman, Adriana M.,Berlin, Cameron B.,Krout, Michael R.
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p. 14723 - 14732
(2018/11/23)
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- Rhodium-catalyzed tandem aldol condensation-Robinson annulation between aldehydes and acetone: Synthesis of 3-methylcyclohexenones
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A simple catalytic, redox-neutral access to 3-methylcyclohexenones has been developed via rhodium catalysis in the presence of an amine additive and Ag2CO3. This process utilized simple aldehydes and acetone as substrates and tolerates a variety of functional groups. Disubstituted phenols were isolated in moderate yields when Cu(OAc)2 was employed as an oxidant.
- Wang, Fen,Liu, Yuchen,Qi, Zisong,Dai, Wei,Li, Xingwei
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supporting information
p. 6399 - 6402
(2014/12/10)
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- The synthesis of cyclohexenone using l-proline immobilized on a silica gel catalyst by a continuous-flow approach
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A facile and convenient method for the synthesis of cyclohexenone compounds was developed using an l-proline immobilized silica gel catalyst combined with a continuous-flow approach. Because of the mild reaction conditions, ease of catalyst recyclability, and product isolation, this reaction approach can potentially be used in a facile scale-up reaction or in industrial applications. the Partner Organisations 2014.
- Zhi, Cong,Wang, Jiaqing,Luo, Bin,Li, Xinming,Cao, Xueqin,Pan, Yue,Gu, Hongwei
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p. 15036 - 15039
(2014/04/17)
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- D-Aminoacylase-initiated cascade Aldol condensation/Robinson annulation for synthesis of substituted cyclohex-2-enones from simple aldehydes and acetone
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As an important building block, developing efficient and green synthesis strategy of cyclohex-2-enones is of great importance. In this present work, a general approach to the mild synthesis of substituted cyclohex-2-enones derivatives starting fro m simple aldehydes and acetone have been achieved via D-aminoacylase-initiated Aldol condensation/Robinson annulation cascade reaction using imidazole as an additive in organic media. The influences of reaction conditions including solvents, enzyme concentration, additives type, molar ratio of enzyme to additive, and substrate scopes were systematically investigated. Furthermore, some experiments were designed to explore the catalytic roles of D-aminoacylase and imidazole in the multistep cascade process, and one possible mechanism was proposed.
- Xiang, Ziwei,Liang, Yiru,Chen, Xiang,Wu, Qi,Lin, Xianfu
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p. 1929 - 1937
(2014/08/05)
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- L-Lysine/imidazole-catalyzed multicomponent cascade reaction: Facile synthesis of C5-substituted 3-methylcyclohex-2-enones
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A facile and simple route for the direct preparation of substituted 3-methylcyclohex-2-enone via Aldol-Robinson cascade reaction of aldehydes and acetones catalyzed by the new catalytic system of L-lysine/imidazole in n-heptane with 0.5% water was reporte
- Xiang, Ziwei,Liu, Zhiqiang,Liang, Yiru,Wu, Qi,Lin, Xianfu
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p. 997 - 1002
(2013/09/02)
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- Effects of dendritic interface on enantioselective catalysis by polymer-bound prolines
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Dendritic effects have been observed in the past for a number of metal-based catalysts, but only rarely for organocatalysts, and particularly chiral organocatalysts. In the current study, l-proline was immobilized as an ester or amide on polyether dendritic spacers attached to polystyrene. The ester-including catalysts showed a remarkable positive dendritic effect on yield, but even more so on enantioselectivity, in the aldol reaction of acetone with aromatic aldehydes. The positive dendritic effect of the aforementioned catalytic systems on the yield, diastereo- and enantioselectivity of a three-component Mannich reaction was of an even greater magnitude. A series of experiments marked the possibility of catalysis by homogenous l-proline, detached from the resin during the reaction, highly unlikely. Model comparative studies with catalysts equipped with linear or only partially dendritic spacers emphasized the superiority of the fully dendritic spacer architecture.
- Kehat, Tzofit,Goren, Kerem,Portnoy, Moshe
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experimental part
p. 394 - 401
(2012/03/22)
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- Cyclic 2:1 and 1:2 aldehyde-to-acetone byproduct adducts in aldol reactions promoted by supported proline-incorporated catalysts
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Significant amounts of cyclic byproducts of aldol addition with stoichiometry deviating from a regular 1:1 addition pattern were formed when the reaction of acetone with aromatic aldehydes was promoted by polymer-supported proline-incorporated catalysts.
- Tuchman-Shukron, Lital,Kehat, Tzofit,Portnoy, Moshe
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scheme or table
p. 992 - 996
(2009/07/26)
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- An efficient synthesis of some 5-substituted-3-methyl-2-cyclohexen-1-ones using microwaves
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3-Methyl-2-cyclohexenone and its 5-substituted-derivatives are prepared in high yields and short duration of time, using the microwave irradiation technique by the condensation of ethyl acetoacetate with eight different aldehydes and piperazine.
- Jyothi, Divya,Hari Prasad
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p. 630 - 632
(2008/09/19)
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- Recyclization of 1,4-dihydropyridine derivatives in acidic medium
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The recyclization of 1,4-dihydropyridines in aqueous-alcoholic hydrochloric acid medium proceeds with cleavage of a C-N bond and pyridine ring opening. Cyclohexenone derivatives are formed as a result of the subsequent intramolecular crotonic condensation of the acyclic intermediate. The leaving carbonyl substituents depart simultaneously with recyclization, depending on the acidity of the reaction medium.
- Stupnikova,Petushkova,Muceniece,Lūsis
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- Gold(I) catalyzed isomerization of 5-en-2-yn-1-yl acetates: An efficient access to acetoxy bicyclo[3.1.0]hexenes and 2-cycloalken-1-ones
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The gold(I) catalyzed rearrangement of 5-en-2-yn-1-yl acetates into functionalized acetoxy bicyclo[3.1.0]hexenes is described. The mild reaction conditions employed allow the efficient and rapid synthesis of a variety of such bicyclic compounds via a sequence of two gold(I)-catalyzed isomerization steps. Acetoxy bicyclo[3.1.0]hexenes products can be further transformed to 2-cycloalkenones by simple methanolysis. Copyright
- Buzas, Andrea,Gagosz, Fabien
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p. 12614 - 12615
(2008/02/03)
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- Enantioselective aldol cyclodehydrations catalyzed by antibody 38C2.
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[formula: see text] Aldolase antibody 38C2 catalyzes the enantioselective aldol cyclodehydration of 4-substituted-2,6-heptanediones (3) to give enantiomerically enriched 5-substituted-3-methyl-2-cyclohexen-1-ones (4). Yields, enantioselectivities, and pro
- List,Lerner,Barbas 3rd.
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- 5-aryl-3-methyl-2-cyclohexen-1-ones from 4-aryl-1, 4-dihydropyridines (hantzsch esters)
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Reductive cyclization of 2,6-dimethyl-3,5-dicarboxyethyl-4-aryl-1,4- dihydropyridines using sodium and methanol as solvent produces the 5-aryl-3- methyl-2-cyclohexen-1-ones.
- Martinez, Roberto,Mendoza, Hector M.,Angeles, Enrique
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p. 2813 - 2820
(2007/10/03)
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- Aldol Reaction and Robinson-Type Annelation Catalyzed by Lanthanoid Triisopropoxides
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Lanthanoid triisopropoxides are active catalysts for aldol reactions.Aldehydes give the corresponding β-hydroxyaldehydes at low temperatures in good yields, whereas ketones are less reactive, but form condensation products at high temperatures.Exceptionally, γ- or δ-diketones easily undergo condensation to give five- and six-membered unsaturated ketones in high yields.The lanthanoid propoxides, catalyzing the Michael addition of ketones to α,β-unsaturated ketones, which give δ-diketones, are also good catalysts for the Robinson-type annelation.In these reactions, the catalytic activity of the lanthanum propoxide is higher than those of the heavy lanthanoid propoxides, and is almost comparable to that of sodium isopropoxide.Since aluminum triisopropoxide shows poor activity, the lanthanoid propoxides are considerably basic for trivalent metal alkoxides.
- Okano, Tamon,Satou, Yoshikazu,Tamura, Motoshi,Kiji, Jitsuo
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p. 1879 - 1886
(2007/10/03)
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- A New Annulation Reagent, 2-Oxo-3-alkenylphosphonates. Reactions with Carbonyl-Stabilized Carboanions or Silyl Enol Ethers Leading to Cyclohexanones
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The reactions of 2-oxo-3-alkenylphosphonates with carbonyl-stabilized carbanions directly lead to 2-cyclohexen-1-ones through a sequence of Michael reaction and intramolecular Horner-Emmons olefination.On the other hand, the Lewis acid-mediated reactions with silyl enol ethers produce 1,5-diketones as Michael adducts, which then undergo cyclization on treatment with sodium hydride or triethylamine/zinc (II) bromide to afford 2-cyclohexen-1-ones or 2-phosphinyl-2-cyclohexen-1-ones, respectively.
- Wada, Eiji,Funakoshi, Junji,Kanemasa, Shuji
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p. 2456 - 2464
(2007/10/02)
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- LATENT ACETONYLATION OF α,β-ENONES WITH ALLYLTRIMETHYLSILANE OR 2-METHYL-2-PROPENYLTRIMETHYLSILANE: SYNTHESIS OF 1,5-DIKETONES AND ANNELATION TO FUSED CYCLOHEXENONES
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Acetonylation of α,β-enones can be achieved by either with (2-methyl-2-propenyl)trimethylsilane or with allyltrimethylsilane followed by oxidative cleavage of the double bond or by the Wacker reaction, respectively.Annelation of the 1,5-diketones is also
- Hosomi, Akira,Kobayashi, Hiroshi,Sakurai, Hideki
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p. 955 - 958
(2007/10/02)
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