- Mechanistic Perspectives in the Regioselective Indole Addition to Unsymmetrical Silyloxyallyl Cations
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Our investigations on the reaction mechanism to account for regioselectivity on the addition of indoles to unsymmetrical silyloxyallyl cations are reported. Using both experimental and computational methods, we confirmed the significance of steric effects from the silyl ether group toward directing the inward approach of indoles, leading to nucleophilic attack at the less substituted electrophilic α′-carbon. The role of residual water toward accelerating the rate of reaction is established through stabilization of the participating silyloxyallyl cation.
- Bresnahan, Caitlin G.,Taylor-Edinbyrd, Kiara A.,Cleveland, Alexander H.,Malone, Joshua A.,Dange, Nitin S.,Milet, Anne,Kumar, Revati,Kartika, Rendy
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- Cooperative benzylic-oxyallylic stabilized cations: regioselective construction of α-quaternary centers in ketone-derived compounds
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We describe a novel reactivity of benzylic-stabilized oxyallyl cations towards regioselective construction of carbon quaternary centers. These synthetically useful intermediates were readily generated upon ionization of aryl substituted α-hydroxy methylenol ethers with catalytic, mild Bronsted acid. The emerging unsymmetrical oxyallyl cations were then directly captured by indoles and other nucleophiles with exquisite control of regioselectivity, predictably at the electrophilic carbon bearing the alkyl substituent to produce highly functionalized, value-added enol ethers.
- Dange, Nitin S.,Stepherson, Jacob R.,Ayala, Caitlan E.,Fronczek, Frank R.,Kartika, Rendy
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- Acetoacetic acid ester derivatives for the manufacture of α-hydroxycarbonyl compounds
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The invention is concerned with a novel process for the manufacture of compounds of the formula STR1 wherein R1 signifies C1-5 -alkyl, especially methyl, ethyl, propyl or isopropyl, and the radicals R2 each independently represent hydrogen or C1-5 -alkyl, especially hydrogen or methyl, ethyl, propyl or isopropyl. The process is characterized in that a compound of the formula STR2 wherein R stands for C1-4 -alkoxy, chlorine, bromine or C1-4 -alkanoyloxy, R1 and R2 have the above significance and R3 represents C1-4 -alkyl. is hydrolyzed and subjected to an aldol condensation and, where R=C1-4 -alkoxy, the reaction product is subsequently subjected to an acid treatment. The compounds I are for the most part known flavoring substances.
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- Chemistry of Singlet Oxygen. 53. Environmental Effects on the Photooxygenation of 2-Methoxy-3-methyl-2-cyclopenten-1-one
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Photooxygenation of 2-methoxy-3-methyl-2-cyclopenten-1-one (1) gives both ene and dioxetane products.The product distribution depends on temperature and solvent.In CD3OD, the photooxygenation of 1 gives solvent adducts as initial products, and the ratio of stereoisomers is very sensitive to the amount of CD3OD in the reaction mixture.The results are discussed in terms of possible intermediates for the ene and dioxetane products, especially an exciplex.
- Kwon, Byoung-Mog,Foote, Christopher S.
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p. 3878 - 3882
(2007/10/02)
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- SYNTHESIS OF DIOSPHENOL ETHERS BY MEANS OF ALKOXYTRIMETHYLSILANES
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α-Diketones may be O-alkylated with a variety of alkoxytrimethylsilanes.
- Ponaras, A. A.,Meah, Md. Younus
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p. 4953 - 4956
(2007/10/02)
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- Tobacco smoke chemistry. 1. A chemical and mass spectrometric study of tobacco smoke alkyl 2-hydroxy-2-cyclopentenones.
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A series of alkyl 2-hydroxy-2-cyclopentenones, which comprise biologically and organoleptically active compounds, have been synthesized and subjected to high resolution mass spectrometric studies to clarify structurally significant fragmentation pathways. On the basis of these results, 26 alkyl 2-hydroxy-2-cyclopentenones were identified in the weakly acidic fraction of smoke condensate from American blend type cigarettes, eighteen of which had not been detected in tobacco smoke previously. The utility for identification purposes of the corresponding quinoxaline derivatives, obtained through condensation with o-phenylenediamine, is discussed.
- Arnarp,Enzell,Petersson,Pettersson
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p. 839 - 854
(2007/10/02)
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- Process for preparing cyclopentenone derivatives
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A process for preparing cyclopentenone derivatives represented by the formula: STR1 wherein R1 is methyl or ethyl, and R2 is hydrogen, methyl or acetyl, characterized in that a 1,4-diketone derivative represented by the formula: wherein R1 and R2 are as defined above is cyclized in the presence of a basic catalyst.
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- Addition of Aldehydes to Activated Double Bonds, XXVIII. Preparations and Reactions of Alkoxy- and Acetoxy-2,5-diones
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Thiazolium salt-catalyzed addition of aliphatic ether-aldehydes and pyrancarbaldehydes leads to corresponding 1-alkoxy-2,5-alkanediones 1-11 and pyranyl-1,4-alkanediones 28 - 47.In the same manner aldehydes react with 1-acetoxy-3-buten-2-one to give 1-acetoxy-2,5-alkanediones 12 - 19, which after saponification yield the 1-hydroxy-5-alkyl-2,5-pentanediones 20 - 27.
- Stetter, Hermann,Mohrmann, Karl-Heinrich,Schlenker, Walter
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p. 581 - 596
(2007/10/02)
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