- New and Efficient Lewis Acid Catalysts in Intramolecular Ene Reactions
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The thermal or Lewis acid catalyzed intramolecular ene reaction of the Knoevenagel adduct 3 from citronellal and dimethyl malonate affords the two diastereoisomeric dimethyl (5-methyl-2-trans-isopropenylcyclohexyl)malonates 4a and 4b.Anhydrous iron(III) c
- Tietze, Lutz F.,Beifuss, Uwe
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- Stereoselective Festphasensynthese von Cyclopentanen und Cyclohexanen durch Mehrkomponenten-Domino-Reaktion - Aufbau einer Substanzbibliothek durch kombinatorische Chemie
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Keywords: En-Reaktionen; Festphasensynthesen; Kaskadenreaktionen; Kombinatorische Chemie; Mehrkomponentenreaktionen
- Tietze, Lutz F.,Steinmetz, Adrian
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p. 682 - 683
(2007/10/03)
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- Surface-Mediated Reactions. 6. Effects of Silica Gel and Alumina on Acid-Catalyzed Reactions
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Absorption of a variety of acids to chromatographic silica gel results in substantial enhancement of their catalytic activity-affording easily prepared, environmentally benign heterogeneous acids that are highly effective in mediating a number of processes.This was shown for the isomerization of allene 1 and dimerization of the corresponding 1,3-diene 2; cyclization of (R)-citronellal (5), the related diester 10, and 1,5-cyclooctadiene (15); Rupe rearrangement of alkynol 18; and Friedel-Crafts cyclodehydration of alcohols 21.By contrast, commercially available Nafion-H was significantly less effective as a heterogeneous acid catalyst.Chromatographic alumina displayed enigmatic behavior, showing enhanced acidity on the adsorption of HCl but little or no acidity on the adsorption of a variety of other types of acid.The results are discussed in terms of the surface structures of silica gel and alumina.
- Kropp, Paul J.,Breton, Gary W.,Craig, Stephen L.,Crawford, Scott D.,Durland, William F.,et al.
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p. 4146 - 4152
(2007/10/02)
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- The Acid-Catalyzed Cyclization of Unsaturated Carbonyl Compounds Utilizing Silica Gel at High Pressure
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The ene-like cyclizations of a series of unsaturated carbonyl compounds have been studied using silica gel at high pressure (15 kbar) as a new catalytic system.This new method is general for forming 5- and 6-membered ring carbocycles.The mildness of this
- Dauben, William G.,Hendricks, Robert T.
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p. 603 - 606
(2007/10/02)
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- Asymmetric Induction in Intramolecular Ene Reactions of Chiral 1,7-Dienes: A Diastereo- and Enantioselective Synthesis of Substituted Cyclohexanes
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The asymmetric induction in intramolecular thermal and Lewis acid catalyzed ene reactions of chiral 1,7-dienes 9 activated by two electron-withdrawing groups on the enophile is studied.The cycloadducts resulting from intramolecular ene, sequential ene, an
- Tietze, Lutz F.,Beifuss, Uwe,Ruther, Michael
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p. 3120 - 3129
(2007/10/02)
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- ASYMMETRIC INDUCTION IN INTRAMOLECULAR ENE REACTIONS OF 1,7-DIENES
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Chiral, double-activated enophiles in 1,7-dienes 6a-d undergo thermal and Lewis-acid catalyzed intramolecular ene reactions yielding trans-cyclohexanes 7a-d and 8a-d.The extent of diastereoselectivity depends on the reaction temperature.The 1,7-dienes 6 a
- Tietze, Lutz F.,Beifuss, Uwe
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p. 1767 - 1770
(2007/10/02)
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