- Lithium(1+)-catalyzed nazarov-type cyclization of 1-arylbuta-2,3-dien-1- ols: Synthesis of benzofulvene derivatives
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Lithium hexafluorophosphate proved to be an effective catalyst for a Nazarov-type cyclization of 1-arylbuta-2,3-dien-1-ols to afford benzofulvenes, valuable as building blocks for functional materials and bioactive compounds. Georg Thieme Verlag Stuttgart New York.
- Sai, Masahiro,Matsubara, Seijiro
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- Lewis Acid Catalyzed Ring-Opening Reaction of Cyclobutanones towards Conjugated Enones
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An unprecedented Fe-catalyzed ring-opening reaction of simple cyclobutanones is developed, which provides access to conjugated enones with good functional group tolerance in high yields under mild conditions. The product derivatization and gram-scale expe
- Gao, Jiqiang,Guo, Ziteng,Li, Zhongjuan,Liu, Chunhui,Liu, Yu,Qiu, Tingtian,Zhang, Min,Zhao, Jinbo
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p. 6111 - 6114
(2021/12/16)
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- Alcohol Dehydrogenases and N-Heterocyclic Carbene Gold(I) Catalysts: Design of a Chemoenzymatic Cascade towards Optically Active β,β-Disubstituted Allylic Alcohols
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The combination of gold(I) and enzyme catalysis is used in a two-step approach, including Meyer–Schuster rearrangement of a series of readily available propargylic alcohols followed by stereoselective bioreduction of the corresponding allylic ketone intermediates, to provide optically pure β,β-disubstituted allylic alcohols. This cascade involves a gold N-heterocyclic carbene and an enzyme, demonstrating the compatibility of both catalyst types in aqueous medium under mild reaction conditions. The combination of [1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene][bis(trifluoromethanesulfonyl)-imide]gold(I) (IPrAuNTf2) and a selective alcohol dehydrogenase (ADH-A from Rhodococcus ruber, KRED-P1-A12 or KRED-P3-G09) led to the synthesis of a series of optically active (E)-4-arylpent-3-en-2-ols in good yields (65–86 %). The approach was also extended to various 2-hetarylpent-3-yn-2-ol, hexynol, and butynol derivatives. The use of alcohol dehydrogenases of opposite selectivity led to the production of both allyl alcohol enantiomers (93->99 % ee) for a broad panel of substrates.
- González-Granda, Sergio,Lavandera, Iván,Gotor-Fernández, Vicente
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p. 13945 - 13951
(2021/04/22)
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- Highly Enantioselective Iridium-Catalyzed Hydrogenation of Conjugated Trisubstituted Enones
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Asymmetric hydrogenation of conjugated enones is one of the most efficient and straightforward methods to prepare optically active ketones. In this study, chiral bidentate Ir-N,P complexes were utilized to access these scaffolds for ketones bearing the stereogenic center at both the α- and β-positions. Excellent enantiomeric excesses, of up to 99%, were obtained, accompanied with good to high isolated yields. Challenging dialkyl substituted substrates, which are difficult to hydrogenate with satisfactory chiral induction, were hydrogenated in a highly enantioselective fashion.
- Peters, Bram B. C.,Jongcharoenkamol, Jira,Krajangsri, Suppachai,Andersson, Pher G.
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supporting information
p. 242 - 246
(2021/01/13)
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- Cobalt-Catalyzed Asymmetric 1,4-Hydroboration of Enones with HBpin
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Herein, a series of new 8-OIQ cobalt complexes were synthesized and used for cobalt-catalyzed chemo- and enantioselective 1,4-hydroboration of enones with HBpin to access chiral β,β-disubstituted ketones with good to excellent chemo- and enantioselectivties. This protocol is operationally simple and shows a broad substrate scope.
- Ren, Xiang,Lu, Zhan
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supporting information
p. 8370 - 8374
(2021/11/01)
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- Catalytic Asymmetric Transfer Hydrogenation of trans-Chalcone Derivatives Using BINOL-derived Boro-phosphates
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Chiral phosphoric-acid-catalyzed asymmetric reductions of trans-chalcones have been investigated in this work. A BINOL-derived boro-phosphate-catalyzed asymmetric transfer hydrogenation of the carbon-carbon double bond of trans-chalcone derivatives employing borane as a hydride source was realized. This methodology provides a convenient procedure to access chiral dihydrochalone derivatives in high yields and with high enantioselectivities under mild conditions.
- Na, Fei,Lopez, Susana S.,Beauseigneur, Alice,Hernandez, Lucas W.,Sun, Zhuoxin,Antilla, Jon C.
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supporting information
p. 5953 - 5957
(2020/08/12)
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- Capturing the Monomeric (L)CuH in NHC-Capped Cyclodextrin: Cavity-Controlled Chemoselective Hydrosilylation of α,β-Unsaturated Ketones
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The encapsulation of copper inside a cyclodextrin capped with an N-heterocyclic carbene (ICyD) allowed both to catch the elusive monomeric (L)CuH and a cavity-controlled chemoselective copper-catalyzed hydrosilylation of α,β-unsaturated ketones. Remarkably, (α-ICyD)CuCl promoted the 1,2-addition exclusively, while (β-ICyD)CuCl produced the fully reduced product. The chemoselectivity is controlled by the size of the cavity and weak interactions between the substrate and internal C?H bonds of the cyclodextrin.
- Bistri-Aslanoff, Olivia,Derat, Etienne,Leloux, Sébastien,Leyssens, Tom,Ménand, Micka?l,Meijide Suárez, Jorge,Riant, Olivier,Roland, Sylvain,Sollogoub, Matthieu,Xu, Guangcan,Zhang, Pinglu,Zhang, Yongmin
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supporting information
p. 7591 - 7597
(2020/03/23)
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- Chemo-Enzymatic Oxidative Rearrangement of Tertiary Allylic Alcohols: Synthetic Application and Integration into a Cascade Process
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A chemo-enzymatic catalytic system, comprised of Bobbitt's salt and laccase from Trametes versicolor, allowed the [1,3]-oxidative rearrangement of endocyclic allylic tertiary alcohols into the corresponding enones under an Oxygen atmosphere in aqueous media. The yields were in most cases quantitative, especially for the cyclopent-2-en-1-ol or the cyclohex-2-en-1-ol substrates without an electron withdrawing group (EWG) on the side chain. Transpositions of macrocyclic alkenols or tertiary alcohols bearing an EWG on the side chain were instead carried out in acetonitrile by using an immobilized laccase preparation. Dehydro-Jasmone, dehydro-Hedione, dehydro-Muscone and other fragrance precursors were directly prepared with this procedure, while a synthetic route was developed to easily transform a cyclopentenone derivative into trans-Magnolione and dehydro-Magnolione. The rearrangement of exocyclic allylic alcohols was tested as well, and a dynamic kinetic resolution was observed: α,β-unsaturated ketones with (E)-configuration and a high diastereomeric excess were synthesized. Finally, the 2,2,6,6-tetramethyl-1-piperidinium tetrafluoroborate (TEMPO+BF4?)/laccase catalysed oxidative rearrangement was combined with the ene-reductase/alcohol dehydrogenase cascade process in a one-pot three-step synthesis of cis or trans 3-methylcyclohexan-1-ol, in both cases with a high optical purity. (Figure presented.).
- Brenna, Elisabetta,Crotti, Michele,De Pieri, Matteo,Gatti, Francesco G.,Manenti, Gabriele,Monti, Daniela
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supporting information
p. 3677 - 3686
(2018/06/04)
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- Copper(II)-Catalyzed Tandem Decarboxylative Michael/Aldol Reactions Leading to the Formation of Functionalized Cyclohexenones
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This work describes the development of a new single-pot copper(II)-catalyzed decarboxylative Michael reaction between β-keto acids and enones, followed by in situ aldolization, which results in highly functionalized chiral and achiral cyclohexenones. The achiral version of this Robinson annulation features a hitherto unprecedented Michael reaction of β-keto acids with sterically hindered β,β′-substituted enones and provides access to all carbon quaternary stereocenter-containing cyclohexenones (11 examples, 43-83% yield). In addition, an asymmetric chiral bis(oxazoline) copper(II)-catalyzed single-pot Robinson annulation has been devised for preparing chiral cyclohexenones, including some products that contain vicinal stereocenters (5 examples, 65-85% yield, 84-94% ee). This latter protocol has been successfully applied to the enantioselective formation of the oxygenated 10-nor-steroid core from readily available starting materials.
- Lee, Jeonghyo,Wang, Sibin,Callahan, Miranda,Nagorny, Pavel
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p. 2067 - 2070
(2018/04/16)
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- The synthesis of non-racemic β-alkyl-β-aryl-disubstituted allyl alcohols and their transformation into allylamines and amino acids bearing a quaternary stereocenter
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A synthesis of non-racemic β-alkyl-β-aryl allyl alcohols and their transformation into allylamines bearing a quaternary stereogenic center is reported. The allyl alcohols were prepared either by Cu-catalyzed enantioselective reduction of enones or by sequ
- Narczyk, Aleksandra,Pieczykolan, Micha?,Stecko, Sebastian
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supporting information
p. 3921 - 3946
(2018/06/08)
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- Chiral 1,3,2-Diazaphospholenes as Catalytic Molecular Hydrides for Enantioselective Conjugate Reductions
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Secondary 1,3,2-diazaphospholenes have a polarized P?H bond and are emerging as molecular hydrides. Herein, a class of chiral, conformationally restricted methoxy-1,3,2-diazaphospholene catalysts is reported. We demonstrate their catalytic potential in asymmetric 1,4-reductions of α,β-unsaturated carbonyl derivatives, including enones, acyl pyrroles, and amides, which proceeded in enantioselectivities of up to 95.5:4.5 e.r.
- Miaskiewicz, Solène,Reed, John H.,Donets, Pavel A.,Oliveira, Caio C.,Cramer, Nicolai
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supporting information
p. 4039 - 4042
(2018/03/13)
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- Highly efficient synthesis of chiral aromatic ketones: Via Rh-catalyzed asymmetric hydrogenation of β,β-disubstituted enones
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A succinct and efficient protocol was developed for the synthesis of chiral aromatic ketones via asymmetric hydrogenation of β,β-disubstituted enones with rhodium catalysts based on chiral bisphosphine thiourea ligands. A series of substrates (17 examples) was smoothly catalyzed to afford the corresponding chiral aromatic ketones in high conversions (>99%) with excellent enantioselectivities (up to 96% ee).
- Zhang, Tao,Jiang, Jun,Yao, Lin,Geng, Huiling,Zhang, Xumu
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p. 9258 - 9261
(2017/08/22)
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- Rearrangement Reactions Leading to Optically Active α,α-Disubstituted Primary Allylamines
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Synthetic routes to α,α-disubstituted allylamines have been examined. Racemic compounds were conveniently prepared by thermal Overman rearrangements of primary allylic alcohols with trisubstituted double bonds, but rearrangement of these substrates using
- Hennum, Martin,Odden, Hege Hortemo,Gundersen, Lise-Lotte
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p. 846 - 860
(2017/02/15)
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- Enantioselective NiH/Pmrox-Catalyzed 1,2-Reduction of α,β-Unsaturated Ketones
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The enantioselective 1,2-reduction of α,β-unsaturated ketones was achieved using a NiH catalyst in the presence of pinacolborane. This mild process represents a general method to access a wide variety of structurally diverse α-chiral allylic alcohols in excellent yields and enantioselectivity, as well as very high levels of ambidoselectivity for 1,2- over 1,4-reduction. Furthermore, for reactions on a 10 mmol scale, catalyst loadings as low as 0.5 mol % could be employed to deliver product without any detrimental effect on the yield, enantio-, or ambidoselectivity.
- Chen, Fenglin,Zhang, Yao,Yu, Lei,Zhu, Shaolin
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supporting information
p. 2022 - 2025
(2017/02/15)
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- Tuning the Reactivity of Functionalized Diallylic Alcohols: Br?nsted versus Lewis Acid Catalysis
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The chemodivergent reactivity of bifunctional, enol thioether-containing diallylic alcohols in acidic medium is disclosed, highlighting the difference between strong Lewis acid and mild Br?nsted acid catalysis. In the presence of bismuth(III) triflate, allylic alcohol activation affords diversely substituted cyclopentenones in a Nazarov-type electrocyclization, whereas activation of the thioenol ether by p-toluenesulfonic acid provides an entry to α-sulfenylated β,γ-unsaturated ketones. Both methods represent a facile access to the corresponding products under mild conditions, using inexpensive and non-toxic catalytic systems.
- Lempenauer, Luisa,Du?ach, Elisabet,Lemière, Gilles
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supporting information
p. 10285 - 10288
(2017/08/07)
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- Traceless OH-Directed Wacker Oxidation-Elimination, an Alternative to Wittig Olefination/Aldol Condensation: One-Pot Synthesis of α,β-Unsaturated and Nonconjugated Ketones from Homoallyl Alcohols
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A new method for one-pot synthesis of β-substituted and β,β-disubstituted α,β-unsaturated methyl ketones from homoallyl alcohols by sequential PdCl2/CrO3-promoted Wacker process followed by an acid-mediated dehydration reaction has been developed. Remarkably, internal homoallyl alcohols delivered regioselectively nonconjugated unsaturated carbonyl compounds under the same protocol. A new starting material-based synthesis of α,β-unsaturated and nonconjugated methyl ketones is demonstrated.
- Bethi, Venkati,Fernandes, Rodney A.
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p. 8577 - 8584
(2016/09/28)
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- Highly enantioselective hydrogenation of steric hindrance enones catalyzed by Ru complexes with chiral diamine and achiral phosphane
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An asymmetric hydrogenation of sterically hindered β,β- disubstituted enones has been well-established by using a ruthenium complex composed of an achiral diphosphane and a chiral diamine as catalyst, wherein the carbonyl group was selectively hydrogenated to give a wide range of chiral allylic alcohols with high levels of enantioselectivity and complete chemoselectivity.
- Chen, Xiangning,Zhou, Han,Zhang, Kunyu,Li, Jiawen,Huang, Hanmin
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supporting information
p. 3912 - 3915
(2014/08/18)
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- Enantioselective synthesis of boron-substituted quaternary carbon stereogenic centers through NHC-catalyzed conjugate additions of (pinacolato)boron units to enones
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The first examples of Lewis base catalyzed enantioselective boryl conjugate additions (BCAs) that generate products containing boron-substituted quaternary carbon stereogenic centers are disclosed. Reactions are performed in the presence of 1.0-5.0 mol %
- Radomkit, Suttipol,Hoveyda, Amir H.
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supporting information
p. 3387 - 3391
(2014/04/03)
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- A multicomponent Ni-, Zr-, and Cu-catalyzed strategy for enantioselective synthesis of alkenyl-substituted quaternary carbons
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The availability of enantiomerically enriched carbonyl-containing compounds is essential to the synthesis of biologically active molecules. Since catalytic enantioselective conjugate addition (ECA) reactions directly generate the latter valuable class of molecules, the design and development of such protocols represents a compelling objective in modern chemistry. Herein, we disclose the first solution to the problem of ECA of alkenyl groups to acyclic trisubstituted enones, an advance achieved by adopting an easily modifiable and fully catalytic approach. The requisite alkenylaluminum reagents are synthesized with exceptional site- and/or stereoselectivity by a Ni-catalyzed hydroalumination process, and the necessary enones are prepared through a site- and stereoselective zirconocene-catalyzed carboalumination/acylation reaction. The all-catalytic procedure is complete within four hours, furnishing the desired products in up to 77 % overall yield and 99:1 enantiomeric ratio. One-two-three punch: Ni-catalyzed alkyne hydroalumination, Zr-catalyzed alkyne carbometalation/acylation, and Cu-catalyzed enantioselective conjugate addition are combined for accessing acyclic organic molecules that contain an alkene-substituted quaternary carbon stereogenic center. The entire process takes less than four hours and affords products in up to 77 % overall yield and 99:1 enantiomeric ratio. Copyright
- McGrath, Kevin P.,Hoveyda, Amir H.
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supporting information
p. 1910 - 1914
(2014/03/21)
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- Catalytic stereospecific allyl-allyl cross-coupling of internal allyl electrophiles with allylB(pin)
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Application of internal electrophiles in catalytic stereospecific allyl-allyl cross-coupling enable the rapid construction of multisubstituted 1,5-dienes, including those with all carbon quaternary centers. Compounds with minimal steric differentiation ca
- Le, Hai,Batten, Amanda,Morken, James P.
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supporting information
p. 2096 - 2099
(2014/05/06)
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- Enantioselective synthesis of quaternary carbon stereogenic centers through copper-catalyzed conjugate additions of aryl- and alkylaluminum reagents to acyclic trisubstituted enones
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Acyclic quaternary carbons by conjugate addition: The first examples of catalytic enantioselective conjugate additions of aryl and alkyl units that generate acyclic all-carbon quaternary stereogenic centers have been developed (see scheme). The requisite
- Dabrowski, Jennifer A.,Villaume, Matthew T.,Hoveyda, Amir H.
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p. 8156 - 8159
(2013/08/23)
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- Pd-catalyzed asymmetric hydrogenation of C=C bond of α,β- unsaturated ketones
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Homogenous palladium-catalyzed asymmetric hydrogenation of C=C double bond of ,-unsaturated ketones has been -developed by using palladium(II) trifluoroacetate/(S)-7,7-bis-[di(4-methoxyphenyl]phosphino)-1,1-spirobiindane complex [Pd(OCOCF3)2-(S)-An-SDP] as the catalyst under ambient hydrogen pressure and room temperature with up to 89% ee. Georg Thieme Verlag Stuttgart · New York.
- Wang, Duo-Sheng,Wang, Da-Wei,Zhou, Yong-Gui
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supporting information; experimental part
p. 947 - 950
(2011/06/17)
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- Features of the chromatography-mass spectrometric identification of condensation products of the carbonyl compounds
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By the example of the condensation products of acetone with the simplest aromatic carbonyl compounds it was shown that the joint interpretation of mass spectrometric and chromatographic data in conjunction with a priori assumptions about the nature of the chemical structure allows the detection of the components of reaction mixtures that were not previously characterized by standard mass spectra or by retention indices on standard stationary phases. A necessary condition for solving such problems is creating a hypothesis about the sample composition that is possible for the expected products of the known organic reactions.
- Zenkevich,Ukolov
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experimental part
p. 1818 - 1828
(2012/01/07)
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- IBS-catalyzed oxidative rearrangement of tertiary allylic alcohols to enones with oxone
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A 2-iodoxybenzenesulfonic acid (IBS)-catalyzed oxidative rearrangement of tertiary allylic alcohols to enones with powdered Oxone in the presence of potassium carbonate and tetrabutylammonium hydrogen sulfate has been developed.
- Uyanik, Muhammet,Fukatsu, Ryota,Ishihara, Kazuaki
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supporting information; experimental part
p. 3470 - 3473
(2009/12/05)
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- Highly chemo- And enantioselective hydrogenation of linear α,β-unsaturated ketones
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A study was conducted to report the synthesis of sulfoximine-derived P,N-ligands and their applications in indium-catalyzed asymmetric hydrogenation reactions. Investigations were conducted using linear β,β- disubstituted 1,3-diphenyl-2-butenone as model substrate and iridium, having a ketonic phenyl group and two alkyl substituents at the olefinic β-positions. Methyl ketone with β-methyl and β-phenyl substituent was also applied in the investigations.
- Lu, Sheng-Mei,Bolm, Carsten
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supporting information; experimental part
p. 7513 - 7516
(2009/09/06)
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- Preparation and decarboxylative rearrangement of (Z)-enyne esters
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A method to assemble (Z)-enyne esters via palladium-catalyzed cross coupling reactions of enol tosylates is reported. A base-mediated one-pot decarboxylative rearrangement of the enynes to enones is described. The scope of this process is examined.
- Woo, Jacqueline C.S.,Walker, Shawn D.,Faul, Margaret M.
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p. 5679 - 5682
(2008/02/10)
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- Highly enantioselective transfer hydrogenation of α,β- unsaturated ketones
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We describe an efficient and highly enantioselective conjugate transfer hydrogenation of α,β-unsaturated ketones that is catalyzed by a salt made from tert-butyl valinate and a recently introduced powerful chiral phosphoric acid catalyst (TRIP). Copyright
- Martin, Nolwenn J. A.,List, Benjamin
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p. 13368 - 13369
(2007/10/03)
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- Asymmetric conjugate reduction of α,β-unsaturated ketones and esters with chiral rhodium(2,6-bisoxazolinylphenyl) catalysts
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New asymmetric conjugate reduction of β,β-disubstituted α,β-unsaturated ketones and esters was accomplished with alkoxylhydrosilanes in the presence of chiral rhodium(2,6-bisoxazolinylphenyl) complexes in high yields and high enantioselectivity. (E)-4-Phenyl-3-penten-2- one and (E)-4-phenyl-4-isopropyl-3-penten-2-one were readily reduced at 60°C in 95% ee and 98 % ee, respectively, by 1 mol % of catalyst loading. (EtO) 2MeSiH proved to be the best hydrogen donor of choice. tert-Butyl (E)-β-methylcinnamate and β-isopropylcinnamate could also be reduced to the corresponding dihydrocinnamate derivatives up to 98% ee.
- Kanazawa, Yoshinori,Tsuchiya, Yasunori,Kobayashi, Kazuki,Shiomi, Takushi,Itoh, Jun-Ichi,Kikuchi, Makoto,Yamamoto, Yoshihiko,Nishiyama, Hisao
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- Highly stereoselective anti SN2′ substitutions of (Z)-allylic pentafluorobenzoates with polyfunctionalized zinc-copper reagents
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(Matrix presented) Allylic substitution reactions of zinc-copper organometallics on (Z)-allylic pentafluorobenzoates proceed with very high regioselectivity and excellent anti selectivity. The high fidelity in transfer of stereochemical information allowed a short synthesis of (+)-ibuprofen (97% ee).
- Harrington-Frost, Nicole,Leuser, Helena,Calaza, M. Isabel,Kneisel, Florian F.,Knochel, Paul
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p. 2111 - 2114
(2007/10/03)
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- Scope and limitation of the nickel-catalyzed coupling reaction between lithium borates and mesylates
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Coupling reaction of aryl borates and mesylates derived from phenols and enols was studied. Mesylates with an electron-with-drawing group or ring were highly reactive at room temperature in the presence of NiCl2(PPh3)2 to furnish the coupling products in good yields.
- Kobayashi, Yuichi,William, Anthony D.,Mizojiri, Ryo
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- Stereoselective intermolecular oxymercurations of trisubstituted allylic ethers
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Trisubstituted allylic ethers undergo intermolecular oxymercurations with good to excellent diastereoselectivity compared to the corresponding allylic alcohols. (C) 2000 Published by Elsevier Science Ltd.
- Cormick, Richard,Perlmutter, Patrick,Selajarern, Walailak,Zhang, Hua
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p. 3713 - 3716
(2007/10/03)
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- The utilization of supercritical carbon dioxide in the palladium- catalyzed hydroarylation of β-substituted-α,β-enones
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The utilization of supercritical carbon dioxide (scCO2) has a beneficial effect on the palladium-catalyzed reaction of acyclic β- substituted-α,β-enones with aryl iodides and hydroarylation (formal conjugate addition) products were isolated in good to high yields. The hydroarylation to vinylic substitution ratio is usually high.
- Cacchi, Sandro,Fabrizi, Giancarlo,Gasparrini, Francesco,Pace, Paola,Villani, Claudio
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p. 650 - 652
(2007/10/03)
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- Reactivity in acid-catalyzed carbon-carbon heterolysis
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Equilibrium and rate constants have been determined for the acid-catalyzed heterolysis of two alcohols, 9-xanthydrol and p-anisyldiphenylmethanol, and two sulfides, (9-xanthyl) methyl sulfide and (7-tropyl) methyl sulfide. These data together with literature information are compared with rate constants for acid-catalyzed C-C heterolysis of several (9-xanthyl) compounds, (7-tropyl) compounds, a set of 3-arylcyclobutanones, and two 2-arylnitrocyclopropanes, all of which fragment to carbocations plus a carbon-centered nucleofuge. The fragmentation mechanisms are shown to be A1 or A1(ion pair) except for the 2-arylnitrocyclopropanes which cleave in trifluoroacetic acid by a concerted mechanism. Rate comparisons among several unstrained substrate sets indicate that O-centered nucleofuges undergo acid-catalyzed heterolysis ca. 103-104 faster than S-centered nucleofuges and ca. 109-1014 faster than the C-centered nucleofuges used here. Factors assisting C-C heterolysis (and their effectiveness) include the acidity of the medium (strong); the basicity and nucleofugality of the nucleofuge (moderate); the stability of the electrofugic carbocation (strong); and relief of ring strain (enormous). Compared with acyclic cleavages, rate accelerations worth ca. 15 kcal/mol (for cyclobutanones) and ca. 27 kcal/mol (for nitrocyclopropanes) are found. These effects are discussed in terms of transition-state structure, aided by computational evidence.
- Cao, Weiguo,Erden, Ihsan,Grow, Richard H.,Keeffe, James R.,Song, Jiangao,Trudell, Mary B.,Wadsworth, Teri L.,Xu, Fu-Pei,Zheng, Ji-Bin
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p. 1009 - 1034
(2007/10/03)
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- Synthesis of functionalized 4a-methyl-1,2,3,4,4a,9,10,10a- octahydrophenanthrenes
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The title compounds were constructed by a Heck reaction of functionalized aryl halides with homoallylic alcohols followed by Michael addition and subsequent cyclocondensation.
- Dyker, Gerald,Grundt, Peter
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p. 588 - 596
(2007/10/03)
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- A Stereoselective Synthesis of (E)-α,β-Unsaturated Ketones Involving the Reactions of Organocerium Reagents with Secondary β-Enamino Ketones
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Stereoselective construction of trisubstituted alkenes has wide applicability to the synthesis of many natural products.Specifically, β-disubstituted enones are important functionalized trisubstituted alkene targets.The reaction of organocerium reagents with secondary β-enamino ketones affords β-disubstituted α,β-unsaturated ketones in fairly good yields.This process shows considerable stereoselectivity, and α,β-unsaturated ketones of (E) configuration are predominantly observed.Organolithium-derived cerium reagents display better stereoselectivity than organomagnesium-based ones.The mechanism of the reaction varies with nitrogen substitution: N-phenyl groups give 1,2-addition products, whereas substitution products are observed with N-alkyl groups.When organocerium reagents were used with β-enamino ketones bearing secondary alkyl groups at the nitrogen atom, a lack of reactivity was observed. - Keywords: assymetric substitution; cerium reagents; enamino ketones; regioselectivity; synthetic methods
- Bartoli, Giuseppe,Marcantoni, Enrico,Petrini, Marino,Sambri, Letizia
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p. 913 - 918
(2007/10/03)
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- Synthesis of β-Disubstituted Enones from Ynones. An Alternative Route to 1,4-Addition of Cuprate to the Ynone System
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A one-pot reaction of 4-phenyl-3-butyn-2-one with hydrogen iodide generated in situ gave a hydroiodinated product that underwent cross coupling with organozinc compounds in the presence of palladium catalyst to provide a simple preparation of 4-disubstituted-3-alken-2-ones in fair to good yields. - Key Words 4-Phenyl-3-butyn-2-one; Cross coupling; Organozinc compounds; Palladium catalyst.
- Luo, Fen-Tair,Hsieh, Li-Chen,Fwu, Shiang-Long,Hwang, Wen-Shu
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p. 605 - 608
(2007/10/03)
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- Highly Stereoselective Synthesis of α,β-Unsaturated Ketones by CeCl3 Mediated Addition of Grignard Reagents to β-Enamino Ketones
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A stereoselective synthesis of α,β-unsaturated ketones by direct addition of Grignard reagents to β-enamino ketones, mediated by dry cerium(III) chloride, is described and a trans relationship between the introduced framework and the carbonyl group is predominantly observed.
- Bartoli, Giuseppe,Cimarelli, Cristina,Marcantoni, Enrico,Palmieri, Gianni,Petrini, Marino
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p. 715 - 716
(2007/10/02)
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- The aldol condensation of acetone with acetophenone
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The kinetics and equilibria involved in the aldol condensation of acetone, acting as carbon acid, and acetophenone have been studied in aqueous alkaline solution.The enone isolated is the E isomer.The reactions are all first order in hydroxide, with rate and equilibrium constants (defined for E-enone as initial compound) of k12 = (5.55 +/- 0.17)*10-6M-1s-1, k21 = (8.00 +/- 0.40) * 10-6M-1s-1, K21 = (1.44 +/- 0.55) (ketol to E-enone), K24 = 0.160 +/- 0.033 (ketol to Z-enone), K32 = (1.89 +/- 0.26) * 10-3M-1 (acetone plus acetophenone to ketol), k23 = 0.180 +/- 0.005 M-1s-1, k32 = (3.41 +/- 0.49) * 10-4M-2s-1.There is an equilibration of the two enones in base that is faster than hydration to the ketol: k14 = (3.14 +/- 0.84) * 10-5M-1s-1; k41 = (2.81 +/- 0.61) * 10-4M-1s-1; K14 = 0.112 +/- 0.019.To analyze the behavior of the enone:ketol equilibrium system in acid we simultaneously fitted analytical data for all three species (E-enone, Z-enone, and ketol) to a kinetic model, so that the rate constants were determined by the best fit to all of the data for an experiment.
- Guthrie, J. Peter,Wang, Xiao-Ping
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p. 1055 - 1068
(2007/10/02)
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- REACTIONS OF ARYLAZO ARYL SULFONES WITH α,β-UNSATURATED ESTERS AND KETONES CATALYZED BY PALLADIUM(0) COMPLEX
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The palladium(0) catalyzed reactions of arylazo aryl sulfones (1) with α,β-unsaturated esters in benzene give aryl-substituted esters as major products and hydroarylated esters as minor products.The reactions of 1 with acyclic α,β-unsaturated ketones give considerable amounts of hydroarylated ketones and aryl-substituted ketones under similar conditions, whereas the reactions of 1 with cyclic α,β-unsaturated ketones afforded selectively hydroarylated compounds and no formation of aryl-substituted ketones was found.A plausible reaction mechanism is proposed.Key words: Arylazo aryl sulfones; palladium(0) catalyst; arylation; α,β-unsaturated carbonyl compounds; diarylpalladiumII) intermediate; catalytic cycle.
- Kamigata, Nobumasa,Satoh, Akira,Yoshida, Masato
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p. 121 - 130
(2007/10/02)
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- A FACILE, STEREOSELECTIVE PREPARATION OF (Z)-2,4-PENTADIENOATES BY FAVORSKII REARRANGEMENT
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Reaction of 1,3,4-tribromo-2-alkanones, efficiently prepared by direct bromination of the parent enone, with methanolic sodium methoxide gives methyl (Z)-2,4-pentadienoates with high (Z) selectivity about the α,β-double bond.
- Engler, Thomas A.,Falter, Wolfgang
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p. 4115 - 4118
(2007/10/02)
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- THE REGIOSELECTIVE PREPARATION OF 1-ALKEN-3-ONES BY THE REACTION OF 3-(1-IMIDAZOLYL)-2-ALKEN-1-ONES WITH ORGANOMETALLIC COMPOUNDS
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3-(1-Imidazolyl)-2-alken-1-ones, having substituent on the C-3 carbon, reacted with organometallic compounds to afford 3-(1-imidazolyl)-2-alken-1-ols.By the treatment of the products with sulfuric acid, 1-alken-3-ones, which were the positional isomers of the Michael addition products, was obtained regioselectively in good yields under mild conditions.Sodium borohydride reduction was also investigated.
- Kashima, Choji,Hibi, Shigeki,Shimizu, Masao,Tajima, Tadakuni,Omote, Yoshimori
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p. 429 - 436
(2007/10/02)
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- CROSS-COUPLING REACTION BETWEEN ENOL PHOSPHATES AND ORGANOALUMINIUM COMPOUNDS IN THE PRESENCE OF PALLADIUM(0) CATALYST.
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The title reaction in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium(0) affords alkylative coupling products in good to excellent yields in 1,2-dichloroethane at room temperature. This coupling reaction under C(sp**2)-O cleavage proceeds stereospecifically. The reaction does not affect a coexisting vinyl sulfide group. This feature enables 1,2- and 1,3-carbonyl transposition with or without alkylation via phenylthio-substituted enol phosphates.
- Takai,Sato,Oshima,Nozaki
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p. 108 - 115
(2007/10/02)
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- A CONVENIENT ROUTE TO α,β-UNSATURATED METHYL KETONES APPLICATION TO RETINAL ANALOGUE SYNTHESIS
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Deprotonated ketimines 1a,b add to aldehydes and ketones to provide tri- and tetra-substituted α,β-unsaturated methyl ketones 2a,b with substantial percentage of Z-geometry which are not readily accessible by other methods.
- Croteau, Allan A.,Termini, John
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p. 2481 - 2484
(2007/10/02)
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- Pd(O) PROMOTED ALKYLATION OF ENOL PHOSPHATES WITH ORGANOALUMINIUM COMPOUNDS AND ITS SYNTHETIC APPLICATIONS
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Keto carbonyl 1,2- and 1,3-transpositions with and without alkylation of the substrate are described together with ketone synthesis from thiocarboxylic S-ester.
- Sato, Mitsuyoshi,Takai, Kazuhiko,Oshima, Koichiro,Nozaki, Hitosi
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p. 1609 - 1612
(2007/10/02)
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- The Conjugate Addition of a Silyl Group to Enones and its Removal with Copper(II) Bromide: A Protecting Group for the αβ-Unsaturation of αβ-Unsaturated Ketones
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Silyl-lithium reagents mixed with copper(I) salts react with enones, including esters and aldehydes, to give β-silyl carbonyl compounds in good yield.The β-silylketones can be used in synthesis without risk to the silyl group and the enone group can be restored by bromination-desilylbromination with copper(II) bromide.The principle is illustrated with syntheses of carvone and dihydrojasmone.
- Ager, David J.,Fleming, Ian,Patel, Shailesh K.
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p. 2520 - 2526
(2007/10/02)
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