- Regioselective Synthesis of α-Perfluoroalkylated Ketals via Double Michael Addition of Alcohols to Activated Alkynes
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An efficient method was developed for the synthesis of alkyl 3,3-dialkoxy-3-(perfluoroalkyl)propanoates from ethyl 3-(perfluoroalkyl)propynoates and alcohols using a base-catalyzed double Michael addition reaction (which was accompanied by transesterification in the case of MeOH, EtOH, PrOH, and BuOH). This method provides easy access to the product α-perfluoroalkyl ketals with reasonable to good yields with total regioselectivity. This procedure does not require the use of expensive supplementary additives for the preparation of α-perfluoroalkyl ketals which are very sensitive to acidic conditions. Georg Thieme Verlag Stuttgart.
- Ndong, Ella,Judicael, Guy,Parrain, Jean Luc,Abarbri, Mohamed
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- Five Roads That Converge at the Cyclic Peroxy-Criegee Intermediates: BF3-Catalyzed Synthesis of β-Hydroperoxy-β-peroxylactones
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We have discovered synthetic access to β-hydroperoxy-β-peroxylactones via BF3-catalyzed cyclizations of a variety of acyclic precursors, β-ketoesters and their silyl enol ethers, alkyl enol ethers, enol acetates, and cyclic acetals, with H2O2. Strikingly, independent of the choice of starting material, these reactions converge at the same β-hydroperoxy-β-peroxylactone products, i.e., the peroxy analogues of the previously elusive cyclic Criegee intermediate of the Baeyer-Villiger reaction. Computed thermodynamic parameters for the formation of the β-hydroperoxy-β-peroxylactones from silyl enol ethers, enol acetates, and cyclic acetals confirm that the β-peroxylactones indeed correspond to a deep energy minimum that connects a variety of the interconverting oxygen-rich species at this combined potential energy surface. The target β-hydroperoxy-β-peroxylactones were synthesized from β-ketoesters, and their silyl enol ethers, alkyl enol ethers, enol acetates, and cyclic acetals were obtained in 30-96% yields. These reactions proceed under mild conditions and open synthetic access to a broad selection of β-hydroperoxy-β-peroxylactones that are formed selectively even in those cases when alternative oxidation pathways can be expected. These β-peroxylactones are stable and can be useful for further synthetic transformations.
- Vil, Vera A.,Gomes, Gabriel Dos Passos,Ekimova, Maria V.,Lyssenko, Konstantin A.,Syroeshkin, Mikhail A.,Nikishin, Gennady I.,Alabugin, Igor V.,Terent'Ev, Alexander O.
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p. 13427 - 13445
(2018/11/02)
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- INHIBITORS OF HIV REPLICATION
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The present invention relates to novel 2,3,4-substituted 5,6,7,8-tetrahydro[1]benzothieno[2,3-b]pyridine compounds and pharmaceutically acceptable salts thereof, to compositions containing such compounds and to the use of such compounds as inhibitors of HIV replication.
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Page/Page column 23
(2012/06/01)
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- Introduction of a carboxyl group through an acetal as a new route to carboxylic acid derivatives of sugars
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A new class of carboxylic acid derivatives of sugars is described. Acetalation of mono- and disaccharides with a functionalized vinylic ether or a diethoxybutanoate afforded mono- and diacetals bearing an ester group. Their saponification led to the corresponding carboxylic acid acetals in which the length of the acetal side chain can be modulated. Copyright (C) 1999 Elsevier Science Ltd.
- Carbonnel, Sylvie,Fayet, Catherine,Gelas, Jacques
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- Photoreactions of Biacetyl with Electron-rich Olefins. An Extended Mechanism
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The photoreactions of biacetyl (1) with various electron-rich olefins have been investigated.Oxetanes and allyl alcohols are formed upon irradiation with λ = 400 - 480 nm (n?* excitation of biacetyl) depending on the nature of the olefin.An unusual relationship between the rate constants of luminescence quenching of biacetyl by olefins (log kq) and the free enthalpies of electron transfer (ΔG2) indicate formation of an exciplex first.A reasonable good fit between experimental results of log kq and ΔG2 has been obtained on the basis of a mechanistic model which includes the exciplex intermediate as well as an ionic photodissociation pathway and some empirical adjustment of the parameters.Complete electron transfer as a consecutive process has been proven for some strong electron-donating olefins by means of ESR spectroscopy and scavenging of the radical cations.The solvent dependence of the product quantum yields further confirms the competition between ionic photodissociation and product formation.The preferred formation of allyl alcohols (reduction products) with strong electron-donating olefins and the highly regioselective oxetane formation with ketene acetal are discussed in terms of exciplexes of strong CT character or even contact ion pairs and dipolar intermediates.
- Mattay, Jochen,Gersdorf, Joachim,Buchkremer, Karl
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p. 307 - 318
(2007/10/02)
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- THERMAL AND PHOTOCHEMICAL REACTIONS OF BIACETYL WITH 1,1-DIETHOXYETHENE. "UMPOLUNG" OF THE REACTIVITY OF BIACETYL BY PHOTOCHEMICAL INDUCED ELECTRON TRANSFER.
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The thermal and photochemical reactions of biacetyl 1 and 1,1-diethoxyethene 2 are totally complementary: 1 and 2 exclusively form the 2,2-diethoxyoxetane 4 in polar solvents at room temperature.Contrary to the literature this thermal cycloaddition proceeds uncatalyzed. 1 and 2 react photochemically under exclusive formation of the regioisomer oxetane 3 - preferably in nonpolar solvents.The inversion ("Umpolung") of the reactivity of 1 is caused by the photoinduced electron transfer.
- Mattay, Jochen,Gersdorf, Joachim,Freudenberg, Ulrich
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p. 817 - 820
(2007/10/02)
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- The efficiency of diphenylalkylsulfonium salts as alkylating agents
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A series of the title reagents have been used for the alkylation of a number of nucleophiles including iodide, cyanide, thiocyanate and fluoride ions as well as ethyl acetoacetate, phenylacetonitrile and a variety of nitrogen heterocyclic compounds.The results compared favorably with literature methods.
- Badet, Bernard,Julia, Marc,Lefebvre, Christian
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p. 431 - 434
(2007/10/02)
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- Regioselectivity of the Alkylation of Ambident Anionic Species on Alumina or in the Presence of 'Solid Hexamethylphosphoric Triamide'
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C-Alkylation of the acetoacetate anions and of sodium naphthoxide is highly favoured on alumina, while O-alkylation of the acetoacetate anion predominates in tetrahydrofuran in the presence of solid hexamethylphosphoric triamide.
- Bram, Georges,Geraghty, Niall,Nee, Gerard,Seyden-Penne, Jacqueline
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p. 325 - 326
(2007/10/02)
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