- Synthesis of Cyclic β-Silylalkenyl Triflates via an Alkenyl Cation Intermediate
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Trimethylsilylalkyne derivatives are transformed into cyclic β-silylalkenyl triflates through cationic cyclization and subsequent trapping of the alkenyl cation by a triflate anion. β-Silylcyclohexenyl triflates and 3-trimethylsilyl-1,4-dihydronaphth-2-yl
- Lee, Craig J.,Swain, Manisha,Kwon, Ohyun
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p. 5474 - 5477
(2018/09/13)
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- A New Route to Phenols: Palladium-Catalyzed Cyclization and Oxidation of γ,δ-Unsaturated Ketones
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We report a new strategy for the synthesis of phenols from acyclic unsaturated ketones in one pot. The reaction proceeds by palladium-catalyzed carbopalladation of an alkene with the enol form of the tethered ketone, generating a substituted cyclohexanone. Upon introduction of a terminal oxidant a palladium-catalyzed oxidation ensues to give the desired phenol. This approach allows the programming of phenol substituents on the acyclic substrate and therefore circumvents the limitations inherent in traditional syntheses of phenols.
- Samadi, Sadaf,Orellana, Arturo
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p. 2472 - 2475
(2016/08/25)
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- Cooperative Palladium/Proline-Catalyzed Direct α-Allylic Alkylation of Ketones with Alkynes
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The cooperative palladium/l-proline-catalyzed direct α-allylic alkylation of ketones with alkynes is achieved. This reaction exhibits high atom economy since a leaving group is not liberated and a stoichiometric amount of extra oxidant is not needed. A br
- Yang, Chi,Zhang, Kaifan,Wu, Zijun,Yao, Hequan,Lin, Aijun
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supporting information
p. 5332 - 5335
(2016/11/02)
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- Regioselective aerobic oxidative Heck reactions with electronically unbiased alkenes: Efficient access to α-alkyl vinylarenes
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Branched-selective oxidative Heck coupling reactions have been developed between arylboronic acids and electronically unbiased terminal alkenes. The reactions exhibit high catalyst-controlled regioselectivity favoring the less common branched isomer. The reactions employ a catalyst composed of Pd(TFA)2/dmphen (TFA = trifluoroacetate, dmphen = 2,9-dimethyl-1,10-phenanthroline) and proceed efficiently at 45-60 °C under 1 atm of O2 without requiring other additives. A broad array of functional groups, including aryl halide, allyl silane and carboxylic acids are tolerated.
- Zheng, Changwu,Stahl, Shannon S.
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supporting information
p. 12771 - 12774
(2015/08/18)
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- Pd(0)-catalyzed 1,1-diarylation of ethylene and allylic carbonates
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An efficient protocol for the one-step synthesis of biologically relevant 1,1-diarylalkanes has been described. This reaction introduces two different aryl groups across the terminal end of simple feedstock alkenes such as ethylene and allylic carbonates.
- Saini, Vaneet,Liao, Longyan,Wang, Qiaofeng,Jana, Ranjan,Sigman, Matthew S.
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supporting information
p. 5008 - 5011
(2013/10/22)
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- Preparation of bicyclic 1,2,4-trioxanes from γ,δ-unsaturated ketones
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(Chemical Equation Presented) Treatment of γ,δ-unsaturated ketones with hydrogen peroxide and acid provides a rapid entry into the medicinally important 1,2,4-trioxane structure. Alkene substitution that stabilizes carbocationic intermediates proved to be important for the success of this transformation.
- Ramirez, Armando P.,Thomas, Andrew M.,Woerpel
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supporting information; experimental part
p. 507 - 510
(2009/08/07)
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- Lewis acid/CpRu dual catalysis in the enantioselective decarboxylative allylation of ketone enolates
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The addition of a Lewis acidic metal triflate salt Mg(OTf)2 as co-catalyst in the CpRu-catalyzed decarboxylative allylation of in situ-generated ketone enolates allows the reaction to proceed at lower temperature with higher regio- and enantios
- Linder, David,Austeri, Martina,Lacour, Jerome
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scheme or table
p. 4057 - 4061
(2009/12/06)
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- Dual palladium-and proline-catalyzed allylic alkylation of enolizable ketones and aldehydes with allylic alcohols
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The dual Pd/proline-catalyzed α-allylation reaction of a variety of enolizable ketones and aldehydes with allylic alcohols is described. In this reaction, the choice of a large-bite angle ligand Xantphos and proline as the organocatalyst was essential for generation of the crucial π-allyl Pd intermediate from allylic alcohol, followed by nucleophilic attack of the enamine formed in situ from the corresponding enolizable carbonyl substrate and proline.
- Usui, Ippei,Schmidt, Stefan,Breit, Bernhard
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supporting information; experimental part
p. 1453 - 1456
(2009/09/30)
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- Enantioselective CpRu-catalyzed carroll rearrangement - Ligand and metal source importance
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The addition of unstabilized carbonyl nucleophiles to unsymmetrical allyl-metal fragments still represents a challenge to generate stereogenic centers enantio- and regioselectively. In this context, the decarboxylative Carroll rearrangement of allyl β-keto esters is particularly interesting, since chiral γ,δ-unsaturated ketones are obtained. Herein, we show that CpRu half-sandwich complexes can, with selected enantio-pure pyridine-monooxazoline ligands, catalyze this transformation and afford complete conversions along with good levels of regioselectivity and enantioselectivity. Even more challenging (electron-poor) substrates react (up to 86% ee, branched/linear ratio ≥ 97:03). In addition, the use of an air-stable metal precursor, namely [CpRu(η6-naphthalene)][PF6], allows the reaction to be carried out reproducibly even in non-anhydrous THF with a catalyst loading as low as 2 mol-%. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Linder, David,Buron, Frederic,Constant, Samuel,Lacour, Jerome
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supporting information; scheme or table
p. 5778 - 5785
(2009/06/18)
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- Sequenced Reactions with Samarium(II) Iodide. Domino Epoxide Ring-Opening/Ketyl Olefin Coupling Reactions
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A new sequential reductive coupling process promoted by samarium(II) iodide is described. Cascade epoxide ring opening and ketyl radical olefin cyclization leads to a variety of cis-1,3-cyclopentanediols and cis-1,3-cyclohexanediols in good yields and with high diastereoselectivity.
- Molander, Gary A.,Losada, Carlos Del Pozo
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p. 2935 - 2943
(2007/10/03)
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- Photoreactions of Phenyl-Substituted N-(Pent-4-enyl-1-oxy)pyridine-1(1H)-thiones
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A series of hitherto unknown N-(pent-4-enyl-1-oxy)pyridine-2(1H)-thiones (6) were prepared from substituted pent-4-enyl tosylates or benzylic chlorides.On irradiation with incandescent light heterocycles 6 liberated alkoxy radicals 2, which were studied for rearrangement reactions.Surprisingly, all transformations involving the 1-phenylpent-4-enyl-1-oxy radical (2a), for example, to give the substituted thioether 8, 2-bromomethyl-5-phenyltetrahydrofuran (11), or the tetrahydrofuran 14a, were not stereoselective.On the other hand 2-, 3-mono-, and 1,5-disubstituted pent-4-enyl-1-oxy radicals 2d-e and 2g cyclized in good yields and with good to excellent stereoselectivities to give the corresponding 2,4-cis- and 2,3-trans-phenyltetrahydrofurfuryl radicals 3d-e, and the trans-2-benzyl-5-methyl substituted intermediate 3g.The major reaction mode of the 4-phenylpent-4-enyl-1-oxy radical (2f) was the 6-endo cyclization, which afforded 3-phenyltetrahydropyran (13f) as the major product (endo:exo=93:7) after trapping with hydrogen donors.According to the experimental data of the present study, the unusual reactivity of the 1-phenylpent-4-enyl-1-oxy radical (2a) in 5-exo-trig ring closures could be caused by a coplanar arrangement of the benzyloxy moiety in the transition state of the cyclization.This interaction would lock the radical center in 2a in a preferred conformation, which would result in similar steric effects for both cis- and trans-cyclizations. - Keywords: alkoxy radicals; cyclizations; pyridinethiones; radicals; tetrahydrofurans
- Hartung, Jens,Hiller, Margit,Schmidt, Philipp
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p. 1014 - 1023
(2007/10/03)
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- Stereoselective synthesis of 4- or 5-substituted 2-benzyl- and 2-benzoylpyrrolidines by means of anodic oxidation of δ-alkenylamines
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The anodic oxidation of the lithium amides of δ-alkenylamines 6a, 6b, 6c, 10a, and 10b gave stereoselectively cis-5-substituted 2-benzyl-1-methylpyrrolidines (7a, 7b, 7c) and 4-substituted 2-benzyl-1-methyl-pyrrolidines (11a, 11b) in high yields. The anod
- Tokuda,Miyamoto,Fujita,Suginome
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p. 747 - 756
(2007/10/02)
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