- The copper-catalyzed selective monoalkylation of active methylene compounds with alkylsilyl peroxides
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A novel method for a mild copper-catalyzed selective monoalkylation of active methylene compounds with various alkylsilyl peroxides has been developed. The reaction has a broad substrate scope and our mechanistic studies suggest the participation of radical species in this alkylation reaction.
- Lv, Jiamin,Xu, Weiping,Lu, Hanbin,Kato, Terumasa,Liu, Yan,Maruoka, Keiji
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supporting information
p. 2658 - 2662
(2021/04/07)
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- Blue light-promoted photolysis of aryldiazoacetates
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Aryldiazoacetates can undergo photolysis under blue light irradiation (460-490 nm) at room temperature and under air in the presence of numerous trapping agents, such as styrene, carboxylic acids, amines, alkanes and arenes, thus providing a straighforward and general platform for their mild functionalization.
- Jurberg, Igor D.,Davies, Huw M. L.
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p. 5112 - 5118
(2018/06/12)
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- On the most powerful chemical traps for bis(methoxycarbonyl)carbene (=2-methoxy-1-(methoxycarbonyl)-2-oxoethylidene)
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The efficiency and validity of different chemical substrates for trapping bis(methoxycarbonyl)carbene (=2-methoxy-1-(methoxycarbonyl)-2-oxoethylidene; 1) is dependent on the conditions of carbene generation. On conventional photolysis of dimethyldiazomalonate (=2-diazopropanedioic acid dimethyl ester; 2) by long-wave UV light (through a Pyrex filter, λ > 290 nm), the most powerful trap for carbene 1 in the series of substrates Me2S, MeOH, cyclohexane, and pyridine is Me2S (with an efficiency ratio of ca. 6 :4 : 2 : 1, resp.). When short-wave decomposition of diazomalonate 2 is employed (through a quartz filter, λ > 210 nm), more reliable and useful chemical traps for bis(methoxycarbonyl)carbene (1) are pyridine and cyclohexane, whose adducts with 1 are rather stable under short-wave-irradiation conditions. Application of alcohols for the trapping of 1 proves to be preferential when simultaneous monitoring of carbene and oxoketene formation during photolysis is necessary.
- Shevchenko, Vladimir V.,Zhegalova, Natalya G.,Borzenko, Andey O.,Nikolaev, Valerij A.
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experimental part
p. 501 - 509
(2009/02/07)
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- Unsaturated esters
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The present invention relates to new α,β-unsaturated esters of formula I. The new compounds exhibit an intense, very long lasting fruity-pineapple odor with green galbanum-type undertones.
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- 1,3-Stereoinduction in radical reactions: Radical additions to dialkyl 2-alkyl-4-methyleneglutarates
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Tin hydride-mediated radical additions to a series of α-methylene-glutarates 1, furnishing 2;4-dialkyl-substituted glutarates 3 are reported. The diastereoselectivity of hydrogen transfer to the intermediate adduct radicals 2, possessing a stereogenic center in γ-position, was disappointing in the temperature range of -78 to 80 °C. However, the reactions proved to be able to proceed with excellent 1,3-diastereoselectivities under chelation-controlled conditions, depending on the steric impacts of 2- and 4-alkyl substituents as well as on the ester-alkyl moiety and choice of Lewis acid. Using MgBr2·OEt2 as additive, syn-selectivities of 98:2 were achieved upon initial tert-butyl radical addition at -78 °C. High anti-diastereoselectivities were observed in the MgBr2·OEt2-controlled pathway at 70 °C when smaller alkyl radicals such as cyclohexyl, ethyl, and methyl were applied. Interesting and uncommon temperature dependences were observed in the temperature range of -78 to 100 °C, revealing strong entropic effects in the transition states. A model that accounts for the opposed stereochemical outcomes under chelation-controlled conditions is presented.
- Hayen,Koch,Saak,Haase,Metzger
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p. 12458 - 12468
(2007/10/03)
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- Mn(III)-mediated in-cell electrochemical addition of active methylene compounds to olefins: synthetic and mechanistic aspects
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The Mn-mediated in-cell electrochemical addition of active methylene compounds is an interesting alternative to usual chemical methods notably with respect to the amount of manganese salt used.The electrochemical approach however requires the reagent to be readily oxidized in order to be associated with an efficient in situ anodic regeneration process.We have used amperometric measurements to show that the rate constants for the Mn(III)-oxidation of active methylene compounds at 60 deg C range between 10-2 and 1.2 L mol-1 s-1.In this study we show that the addition reaction occurs in the coordination sphere of Mn; this requires the active methylene compound and the olefin to be coordinated to the Mn salt.This aspect can be critical in the electrochemical process insofar as the catalytic manganese salt can sometimes be fully coordinated by only one reagent, either the active methylene compound (eg, 2,4-pentanedione) or the olefin (eg, styrene). - Key words: electrochemistry; manganese(III); addition reaction; free radical
- Nedelec, Jean-Yves,Lachaise, Isabelle,Nohair, Khaddouj,Paugam, Jean Paul,Hakiki, Marjouba
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p. 843 - 849
(2007/10/02)
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- LIQUID CRYSTALLINE PROPERTIES OF 2-(trans-4-n-ALKYLCYCLOHEXYL)-PROPANE-1,3-DIOLS
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The liquid crystalline properties of the homologous series of 2-(trans-4-n-alkylcyclohexyl)propane-1,3-diols 1 is described.These compounds exhibit thermotropic and after addition of small amounts of water also lyotropic liquid crystalline properties.The phase behaviour is described and explained by a general model, whereby hydrogen-bonding and hydrophobic interactions are considered.
- Tschierske, C.,Altmann, H.,Zaschke, H.,Brezesinski, G.,Kuschel, F.
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p. 295 - 300
(2007/10/02)
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- Measurement of Deuterium Kinetic Isotope Effects in Organic and Biochemical Reactions by Natural Abundance Deuterium NMR Spectroscopy
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Natural abundance deuterium NMR spectroscopy is a powerful and convenient tool for the estimation of deuterium kinetic isotope effects in organic reactions, obviating in many cases the preparation of isotopically enriched reactants for such measurements.Determinations of the primary or secondary kinetic isotope effects for a broad variety of reaction types are described to illustrate this technique.
- Pascal, Robert A. Jr.,Baum, Mary W.,Wagner, Carol K.,Rodgers, Lauren R.,Huang, Ded-Shih
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p. 6477 - 6482
(2007/10/02)
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