- Radical-polar crossover reactions of vinylboron ate complexes
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Vinyl boronic esters are valuable substrates for Suzuki-Miyaura cross-coupling reactions. However, boron-substituted alkenes have drawn little attention as radical acceptors, and the radical chemistry of vinylboron ate complexes is underexplored. We show here that carbon radicals add efficiently to vinylboron ate complexes and that their adduct radical anions undergo radical-polar crossover: A 1,2-alkyl/aryl shift from boron to the α-carbon sp2 center provides secondary or tertiary alkyl boronic esters. In contrast to the Suzuki-Miyaura coupling, a transition metal is not required, and two carbon-carbon bonds are formed. The valuable boronic ester moiety remains in the product and can be used in follow-up chemistry, enlarging the chemical space of the method. The cascade uses commercial starting materials and provides access to perfluoroalkylated alcohols, γ-lactones, γ-hydroxy alkylnitriles, and compounds bearing quaternary carbon centers.
- Kischkewitz, Marvin,Okamoto, Kazuhiro,Mück-Lichtenfeld, Christian,Studer, Armido
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p. 936 - 938
(2017/03/15)
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- A new synthesis of γ-butyrolactones via AuCl3- or Hg(II)-catalyzed intramolecular hydroalkoxylation of 4-bromo-3-yn-1-ols
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An efficient conversion of 4-bromo-3-yn-1-ols to γ-butyrolactones via AuCl3-catalyzed electrophilic cyclization (hydroxyl-assisted regioselective hydration) in wet toluene is described. Various secondary and tertiary alcohols including benzylic systems were found to be equally reactive with moderate to excellent yields obtained in all cases.
- Reddy, Maddi Sridhar,Kumar, Yalla Kiran,Thirupathi, Nuligonda
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supporting information; experimental part
p. 824 - 827
(2012/04/05)
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- Unprecedented rearrangement of a 4-alkoxy-5-bromoalk-2-en-1-ol to a cyclopentenone via an iso-nazarov cyclization process
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(Chemical Equation Presented) We report the structure determination of the product 9 of the rearrangement of the allylic alcohol 3 under very mild conditions, probably promoted by an acidic substance, and propose a reasonable mechanism for its formation.
- Jung, Michael E.,Yoo, Dongwon
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p. 8565 - 8568
(2008/02/13)
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- A new synthesis of lactones from tertiary alkenylcarbinols by cobalt-catalyzed photocarbonylation under ambient conditions
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In the presence of a Co catalyst, tertiary vinyl-, propenyl-, and allylcarbinols were chelatively cycloadded to carbon monoxide to produce lactones by xanthone-sensitized photoreaction in tetrahydrofuran, under CO at 1 atmosphere and at room temperature.At lower temperatures the isomerization of alkenyl-carbinols was suppressed and lactones were obtained with improved selectivity.The photoprocess was facilitated by addition of pyridine or hydrogen and retarded in presence of amines or phosphines.Mechanistic interpretations for the process and the accompanying effects are discussed.Key words: chelative carbonylation, photocarbonylation, carbonylation of olefins, lactones synthesis from alkenylalcohols.
- Chow, Yuan L.,Huang, Yu-Jin,Dragojlovic, Veljko
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p. 740 - 742
(2007/10/02)
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- C-C Bond Cleavage of 2-Acylimidazolium Salts in a Sequence involving a New Ester Homoenolate Equivalent. A Synthesis of γ-Lactones
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Reaction of the anion of 2-(1-tri-isopropylsiloxyallyl)-N-methoxymethylimidazole with ketones and aldehydes proseeds regioselectivity to give the enol silyl ethers of 2-acylimidazoles which suffer cleavage to γ-lactones after desilylation, N-methylation, and base treatment.
- Davies, D. Huw,Hall, Jonathan,Smith, Edward H.
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p. 837 - 838
(2007/10/02)
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- The evaluation of dicyclopentadienylsamarium as a reagent in organic synthesis
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SmCp2, which is easily prepared from SmI2, has been screened as a reducing agent for organic chemistry. In particular, SmCp2 promotes the pseudo-Barbier reaction between carbonyl compounds (aldehydes and ketones) and aliphatic or allylic halides more efficiently than does SmI2.
- Namy,Collin,Zhang,Kagan
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- METHYL 3-PHENYLSULPHONYL ORTHOPROPIONATE: AN EFFICIENT REAGENT FOR THE SYNTHESIS OF γ-LACTONES AND BUTENOLIDES
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Treatment of methyl 3-phenylsulphonyl orthopropionate with n-BuLi gives the corresponding carbanion which reacts with aldehydes or ketones to yield β-phenylsulphonyl-γ-lactones.Base-catalysed elimination yields α,β or β,γ-butenolides.
- Carretero, Juan Carlos,Lombaert, Stephane De,Ghosez, Leon
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p. 2135 - 2138
(2007/10/02)
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- Cyclodepsipeptides from Beauveria bassiana. Part 3. The Isolation of Beauverolides Ba, Ca, Ja, and Ka
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Beauverolides Ja and Ka are shown to be the cyclotetradepsipeptides cyclo- and the 3-hydroxy-4-methyldecanoyl homologue, respectively.Pairs of beauverolides differing only in the hydroxy-acid residue are readily separated by high-pressure liquid chromatography and beauverolides Ba and Ca have been isolated using this technique.
- Grove, John Frederick
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p. 2878 - 2880
(2007/10/02)
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