- Organocatalytic synthesis of polysubstituted tetrahydrofurans from alkenes
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A novel, organocatalytic and environmentally friendly protocol for the synthesis of polysubstituted tetrahydrofurans from trivial starting materials has been described. By employing 2,2,2-trifluoroacetophenone-mediated oxidation, which utilizes H2O2 as a green oxidant, we introduce a sustainable procedure that embraces the principles of green chemistry for the production of substituted tetrahydrofurans in high to excellent yields and tolerates a wide range of substitution patterns.
- Theodorou, Alexis,Kokotos, Christoforos G.
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supporting information
p. 670 - 674
(2017/08/18)
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- Breaking the dichotomy of reactivity vs. chemoselectivity in catalytic SN1 reactions of alcohols
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The inability to decouple Lewis acid catalysis from undesirable Bronsted acid catalysed side reactions when water or other protic functional groups are necessarily present has forced chemists to choose between powerful but harsh catalysts or poor but mild
- Hellal, Malik,Falk, Florian C.,Wolf, Elena,Dryzhakov, Marian,Moran, Joseph
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supporting information
p. 5990 - 5994
(2014/08/05)
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- Tertiary alkoxyl radicals from 3-alkoxythiazole-2(3H)-thiones
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This study deals with the synthesis of tert-O-alkyl thiohydroxamates and their use as tert-alkoxyl radical precursors. tert-Alkoxyl radicals were applied in mechanistic studies to determine rate constants of (i) p-chlorocumyloxyl radical addition to bicyclo[2.2.1]heptene (k=1×107 M -1 s-1), (ii) 2-phenylhex-5-en-2-oxyl radical 5-exo-trig-cyclization (kcis=3×109 s-1, ktrans=1×109 s-1), and (iii) 2-methyl-5-phenylpent-2-oxyl to 2-hydroxy-2-methyl-5-phenylpent-5-yl radical isomerization (1,5-H-atom shift; k=0.4-1.5×108 s-1). The reactions pose key steps in synthesis of 2,2,5-substituted tetrahydrofurans and 2-bromo-3-alkoxybicyclo[2.2.1]heptanes. Stereoselectivity in 5-exo-trig cyclization (2,5-cis) and intermolecular addition (exo/endo>99:1), originates from torsional strain in transition structures of alkoxyl radical reactions.
- Schur, Christine,Becker, Nina,Bergstr??er, Uwe,Gottwald, Thomas,Hartung, Jens
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experimental part
p. 2338 - 2347
(2011/04/22)
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- Cyclopropylmethyl- and cyclobutylmethyllithium by an arene-catalyzed lithiation. Stability and reactivity
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The reaction of (chloromethyl)cyclopropane 5 and (bromomethyl)cyclobutane 8 with lithium and a substoichiometric amount of DTBB, in the presence of different carbonyl compounds as electrophiles, in THF at -78 °C leads, after hydrolysis, to the corresponding cycloalkyl alcohols 6 and 9, respectively. However, when the same starting materials are lithiated using naphthalene as catalyst in diethyl ether and at higher temperature (0 or 25 °C), and then react with the same electrophiles, the final hydrolysis yields the corresponding unsaturated alcohols 7 and 10, respectively.
- Pe?afiel, Itziar,Pastor, Isidro M.,Yus, Miguel
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experimental part
p. 2928 - 2935
(2010/06/16)
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- Easy selective generation of (lithiomethyl)cyclopropane or homoallyllithium by a chlorine-lithium exchange
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The reaction of (chloromethyl)cyclopropane 5 with lithium and a catalytic amount of DTBB (5 mol %) in the presence of different carbonyl compounds [Et2CO, n-Pr2CO, (c-C3H5)2CO, (CH2)5CO, PhCOMe, t-BuCHO, i-PrCHO, PhCHO] as electrophiles in THF at -78 °C leads, after hydrolysis with water, to the corresponding cyclopropyl alcohols 6. However, when the same starting material is lithiated using naphthalene as the arene catalyst in ether at 0 °C and then reacts with the same series of electrophiles, the final hydrolysis with water yields the corresponding unsaturated alcohols 7.
- Pastor, Isidro M.,Pe?afiel, Itziar,Yus, Miguel
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scheme or table
p. 6870 - 6872
(2009/04/07)
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- Dibromomethane as one-carbon source in organic synthesis: A versatile methodology to prepare the cyclic and acyclic α-methylene or α-keto acid derivatives from the corresponding terminal alkenes
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Ozonolysis of mono-substituted alkenes A-1 followed by reacting with a preheated mixture of CH2Br2-Et2NH affords α-substituted acroleins A-2 in good yields. Under very mild reaction conditions, these α-substituted acroleins A-2 can be easily converted to α-methylene esters A-4, which could be further converted to the corresponding α-keto esters A-5. This methodology can be also applied to the preparation of α-methylene lactones B-4, α-methylene lactams, and α-keto lactones B-5 with various ring sizes.
- Hon, Yung-Son,Liu, Yu-Wei,Hsieh, Cheng-Han
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p. 4837 - 4860
(2007/10/03)
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- Samarium-mediated Barbier reaction of carbonyl compounds
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Samarium metal in the presence of catalytic amounts of iodine was found to be effective for the Barbier reaction of carbonyl compounds.
- Basu, Manas K.,Banik, Bimal K.
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p. 187 - 189
(2007/10/03)
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- Oxymetallation. Part 24. Preparation of cyclic peroxides by cycloperoxymercuriation of unsaturated hydroperoxides
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Seventeen unsaturated hydroperoxides have been converted by treatment with mercury(II) acetate and/or mercury(II) nitrate into nineteen new mercuriated cyclic peroxides and by subsequent demercuriation with alkaline sodium borohydride, six new mercury-free peroxides have been isolated. The results greatly extend the range of such reactions and provide information about the stereoselectivities and relative ease of several different modes of cycloperoxymercuriation. It is suggested that the reactions with mercury(II) acetate are kinetically controlled whereas those with mercury(II) nitrate show a component of thermodynamic control of product distribution.
- Bloodworth,Curtis,Spencer,Tallant
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p. 2729 - 2750
(2007/10/02)
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- A Convenient Large-Scale Synthesis of Cyclobutyl Halides
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An improved method for the preparation of multigram quantities of cyclobutyl halides is described.The Grignard reactivity of these halides is also discussed.
- Dupont, Andrea C.,Audia, Vicki H.,Waid, Philip P.,Carter, J. Paul
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p. 1011 - 1021
(2007/10/02)
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