- Highly Efficient Gold(I)-Catalyzed Regio- and Stereoselective Hydrocarboxylation of Internal Alkynes
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We report the highly efficient gold-catalyzed hydrocarboxylation of internal alkynes that operates under solvent- and silver-free conditions. This new, simple, and eco-friendly protocol allows for the synthesis of a wide variety of functionalized aryl and
- Dupuy, Stéphanie,Gasperini, Danila,Nolan, Steven P.
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- Enantioselective Iodine(III)-Mediated Synthesis of α-Tosyloxy Ketones: Breaking the Selectivity Barrier
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The development of practical methods to access chiral nonracemic α-substituted ketones is of particular importance due to their ubiquitous nature. Unprecedented levels of enantioselectivity are reported for the synthesis of α-tosyloxy ketones, using enol esters and chiral iodine(III) reagents. The reaction can be performed under both stoichiometric and catalytic conditions. These results suggest widely different reaction mechanisms for the reaction of ketones versus enol esters, supporting recent computational insights.
- Basdevant, Benoit,Legault, Claude Y.
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- Stereochemistry of the Acetoxymercuration of Alkynes. A Synthesis of Vinyl Acetates
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The stereochemistry of acetoxymercuration of 3-hexyne has been established as antarafacial on the basis of an X-ray crystallographic study.Acetoxymercuration of diphenylacetylene afforded (Z)-α-acetoxy-β-(acetoxymercuri)stilbene by a suprafacial addition of Hg(OAc)2.A simple method for the in situ acetoxymercuration-demercuration of dialkyl-substituted alkynes to afford vinyl acetates is described.The sodium borohydride reduction of vinyl mercurials was shown to produce divinyl mercurials while demercuration with zinc dust in acetic acid provided a useful method for the preparation of vinyl acetates.
- Bach, Robert D.,Woodard, Robert A.,Anderson, Thomas J.,Glick, Milton D.
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- Addition of carboxylic acids to alkynes catalysed by ruthenium complexes
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The addition of carboxylic acids to alkynes has been found to be catalyzed by Ru3(CO)12 as well as by dimeric ruthenium carboxylate complexes of general structure 2.The reaction yields vinyl esters.It was found to be general with respect
- Rotem, Michal,Shvo, Youval
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p. 189 - 204
(2007/10/02)
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- Electron-Transfer Photosensitized Oxygenation of Stilbene and Naphthalene Derivatives in the Presence of Acetate Ion. Controlling the Reaction of the Cation Radicals by Weak-Nucleophilic Salts
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The 9,10-Dicyanoanthracene (DCA)- or 9-cyanoanthracene-sensitized photooxygenation of trans-stilbene derivatives gave benzaldehyde derivatives efficiently in the presence of weak-nucleophilic salts, such as Et4NOAc and KOAc/18-crown-6 ether.The product distribution of this photooxygenation was apparently different from that of each photooxygenation in the presence of Mg(ClO4)2 and Et4NBF4 or in the absence of the salt.The DCA-sensitized photooxygenation of 2-methylnaphthalene gave phthalic acid and 4-methylphthalic acid in the presence of Nt4NOAc.These products were different from the products generated from each photooxygenation in the presence of Et4NBF4 and KClO4 or in the absence of the salt.Also, such ring-oxygenation occurred in the DCA-sensitized photooxygenation of 2,3-dimethylnaphthalene and naphthalene in the presence of Et4NOAc.These photooxygenations in the presence of Et4NOAc proceeded by the addition of an acetate ion to the cation radical of the substrate generated by a photochemical electron transfer from the substrate to the sensitizer and the subsequent reaction with O2 and the related oxygen species.
- Yamashita, Toshiaki,Tsurusako, Taiji,Nakamura, Nobuya,Yasuda, Masahide,Shima, Kensuke
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p. 857 - 862
(2007/10/02)
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- The Palladium-Catalyzed Cross-Coupling Reaction of Enol Acetates of α-Bromo Ketones with 1-Alkenyl-, Aryl-, or Alkylboron Compounds; A Facile Synthesis of Ketones and Their Enol Acetates
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The synthesis of stereodefined enol acetates of ketones is readily accomplished by palladium-catalyzed cross-coupling reaction between alkyl-, aryl-, or 1-alkenylboron reagents with enol acetates of α-bromo ketones.Hydroboration of alkene with 9-BBN, followed by coupling with (Z)-2-ethoxy-1-bromoethene gives the enol ether of aldehyde.These enol acetates and ethers are readily deprotected to give corresponding ketones and aldehydes in high yields.
- Abe, Shigeru,Miyaura, Norio,Suzuki, Akira
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p. 2863 - 2865
(2007/10/02)
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- SYNTHESIS OF ENOL ESTERS FROM TERMINAL ALKYNES CATALYZED BY RUTHENIUM COMPLEXES
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Regioselective enol ester formation results from the addition of saturated and unsaturated carboxylic acids to phenylacetylene in the presence of RuCl3, RuCl3/2PR3 or RuCl2(PMe3)(arene) catalysts.
- Ruppin, Christophe,Dixneuf, Pierre H.
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p. 6323 - 6324
(2007/10/02)
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- CESIUM FLUORIDE-PROMOTED REACTION OF ALDEHYDES WITH S-(2-BENZIMIDAZOLYL)ALKANETHIOATES A NEW METHOD FOR THE PREPARATION OF ENOL ESTERS
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Aldehydes are converted to the corresponding enol esters in good yields by treatment with S-(2-benzimidazolyl)alkanethioates in the presence of cesium fluoride.
- Mukaiyama, Teruaki,Murakami, Masahiro,Yamaguchi, Masahiko
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p. 529 - 532
(2007/10/02)
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- Regio- and Stereo-selectivity of Acetoxymercuration of Acetylenes
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Acetoxymercuration of alkylphenylacetylenes (PhCCR; R = Me, Et, Prn, or Bun) (1) in acetic acid at 20 - 60 deg C proceeds completely in a trans-fashion to afford a regioisomeric mixture of two vinylmercury(II) compounds, Ph(OAc)C=C(HgCl)R (2) and Ph(HgCl)C=C(OAc)R (3), the extent of attack of Hg at the carbon α to alkyl group to form (2) being increased upon increasing the carbonyl chain length of the alkyl group .A bridged mercurinium ion intermediate in which phenyl and alkyl groups are bent toward the attacking side of acetate anion is proposed for explaining a marked dependence of the isomer ratio (2):(3) on the kind of alkyl groups.Similar treatment of diphenylacetylene at 20 - 95 deg C gives only the cis-adduct as reported previously, while that of diethyl-acetylene affords the trans-adduct and a mixture of trans- and cis-adduct at 20 deg C and at 65 deg C, respectively.The NaBH4 reduction of (2, R = Me) in neutral condition produces a mixture of (Z)- and (E)-1-acetoxy-1-phenylpropene (ca. 3-5:1) in contrast to the reduction of thallium analogue of (2) which gives only the Z-isomer.
- Uemura, Sakae,Miyoshi, Haruo,Okano, Masaya
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p. 1098 - 1103
(2007/10/02)
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