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  • C-C coupling  (11)
  • Radicals  (11)
  • Wiley-Blackwell  (22)
  • American Chemical Society
  • Blackwell Publishing Ltd
  • 2000-2004  (22)
  • 1940-1944
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Keywords
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  • Wiley-Blackwell  (22)
  • American Chemical Society
  • Blackwell Publishing Ltd
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Ring Closure Reactions of Disubstituted 4-Penten-1-oxyl Radicals - Towards a Stereoselective Synthesis of allo-Muscarine (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1677-1683 
    Details
    ISSN: 1434-193X
    Keywords: Radicals ; Cyclizations ; Pyridinethione ; Tetrahydrofurans ; Asymmetric synthesis ; Thiazolethione ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The trisubstituted functionalized tetrahydrofurans 10, 11, 16, 18, and 19 were photochemically prepared from 2,3-syn- and 2,3-anti-configuredN-(3-benzoyloxy-5-hexen-2-oxy)thiazole-2(3H)-thione anti-6, pyridinethiones 7, anti-8, and BrCCl3. The formation of tetrahydrofurans was achieved by an efficient and highly regioselective alkoxyl radical cyclization (5-exo-trig). The 2,3-anti substituted intermediates 9 and 12 cyclize stereoselectively whereas a 2,3-syn-configured O-radical affords both possible diastereomeric addition products in equal amounts. The cyclized tetrahydrofuryl methyl radicals were trapped with the bromine atom donor BrCCl3 to afford the bromomethyl-substituted cyclic ethers 10, 11, 18, and 19 in excellent yields. The utility of this reaction was stressed by conversion of one of the newly prepared tetrahydrofurans in a two-step synthesis into (+)-allo-muscarine (+)-20.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99590_s.pdf or from the author.
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  • 2
    Electronic Resource
    Electronic Resource
    Changing the Reactivity of Enediynes by Metal-Ion Coordination (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 381-385 
    Details
    ISSN: 1434-193X
    Keywords: Enynes ; Macrocycles ; Coordination chemistry ; Crown compounds ; Radicals ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The complex molecular structure and interesting activation mechanisms of naturally occurring enediynes have inspired the synthesis of a variety of simpler model systems to mimic their properties. While in most model compounds nucleophilic attack, isomerization or bioreduction are used to activate the unsaturated system for diradical cyclization, some attempts have been made to employ metal-ion coordination for this purpose. Significant enhancement of the thermal reactivity has been achieved by metal-ion induced conformational and electronic changes of suitably substituted enediynes, such as 1, 5, 6, 17 and 18. Enediyne activation by stoichiometric or catalytic formation of vinylidene complexes, such as 22, from terminal alkynes has also been investigated. This paper summarizes recent results pursuing the activation of enediyne diradical cyclization by metal ions.
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  • 3
    Electronic Resource
    Electronic Resource
    Studies Towards the Synthesis of Aplykurodins - Synthesis of 17,18-Dihydro-3,9-di-epi-aplykurodinone B (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 439-448 
    Details
    ISSN: 1434-193X
    Keywords: Aplykurodins ; Marine steroids ; C-C coupling ; Cyclic peroxides ; Lactonization ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---An approach to the synthesis of aplykurodins, ichthyotoxic marine lactones, is presented. The carbon framework was derived from vitamin D3 by conversion of the readily accessible allyl alcohol 13 to the protected Grundmann's hydroxy ketone 22 and subsequent introduction of the C2 side chain through a Pd0-promoted coupling. Highly stereoselective hetero Diels-Alder reaction with O21 produced the key intermediate peroxide 25. Functional group transformations, coupled with a series of chemo- and stereoselective reactions, finally resulted in the synthesis of the unnatural analogue 17,18-dihydro-3,9-di-epi-aplykurodinone B (6).
    Additional Material: 2 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    A Radical-Based Strategy for the Synthesis of Higher Homologues of Sinefungin (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 627-631 
    Details
    ISSN: 1434-193X
    Keywords: Complex nucleoside ; Antibiotics ; Radicals ; Zn-Cu couple ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Homosinefungin 5, which can be considered as an analogue of S-adenosylmethionine (SAM) and of S-adenosylhomocysteine (SAH), has been synthesized by means of a sequence in which the key step was the addition of a radical, produced by the simple treatment of an iodide precursor with a zinc-copper couple, to suitably activated olefins.
    Additional Material: 1 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and Crystal Structure of Bis(2,3-dihydro-3-methylbenzothiazole-2-ylidene)palladium(II) Diiodide: The First Palladium Complex with Benzothiazole Carbene Ligands Suitable for Homogeneous Catalysis (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 869-871 
    Details
    ISSN: 1434-193X
    Keywords: Benzothiazole carbene ; Palladium complex ; Homogeneous catalysis ; C-C coupling ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The first diiodo palladium complex with nucleophilic benzothiazole carbenes as ligands has been synthesized and characterized. The complex, which is extraordinarily stable towards heat, oxygen, and moisture, has been found to show good catalytic activity in the Heck coupling reaction.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New Approach to β-Lactam-Fused Enediynes (“Lactenediynes”) by Stereoselective Pinacol Coupling (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 939-946 
    Details
    ISSN: 1434-193X
    Keywords: Enediynes ; Vanadium ; C-C coupling ; Macrocycles ; Lactams ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A short synthesis of unfunctionalized lactenediyne 3 by closure of the ten-membered ring at the double bond site is reported. After failure of the known methodologies, this closure was eventually successfully achieved thanks to a highly stereoselective, vanadium(II)-mediated pinacol coupling of bis(alk-2-ynal) 7.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/99471_s.pdf or from the author.
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  • 7
    Electronic Resource
    Electronic Resource
    Photoaddition of Aliphatic Ethers to 4-Methyl-1,2,4-triazoline-3,5-dione: Application to the Synthesis of Functionalized Crown Ethers and Mechanism (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 617-626 
    Details
    ISSN: 1434-193X
    Keywords: Radicals ; Photochemistry ; Aliphatic ethers ; Hydrogen abstraction ; Urazolyl radical ; α-Alkoxy-alkyl radical ; Diones ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The photoaddition of 4-methyl-1,2,4-triazoline-3,5-dione (4-MTAD) with a wide variety of acyclic, cyclic and crown aliphatic ethers has been investigated. Monochromatic (λ = 514.5 nm) or polychromatic (λ ≥ 310 nm) irradiations give identical mono-urazolyl ethers as reaction products. Unsymmetrical acyclic ethers afford a mixture of the two α and α′ mono-urazolyl ethers. In the case of 12-crown-4, mono and di-substituted products are obtained. ESR experiments and quantum calculations at the AM1 and 6-31G* levels were performed and a possible reaction mechanism is proposed in which the most probable photochemical process is the H-abstraction leading to a urazolyl radical.Supporting information for this article is available on the WWW under //http://www.wiley-vch.de/contents/jc_2046/2000/099269_s.pdf or from the author.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    1,2,3,4-Tetra-tert-butyl-4-trimethylsilyl-4-sila-2-cyclobuten-1-yl: A Quantum Mechanical and ESR Study (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1107-1112 
    Details
    ISSN: 1434-193X
    Keywords: Photochemistry ; Radicals ; EPR spectroscopy ; Quantum mechanical calculations ; Silicon compounds ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Trisilane 7 has been synthesized as a potential photochemical precursor of tetra-tert-butylsilatetrahedrane (5) and/or tetra-tert-butylsilacyclobutadiene (6). Astonishingly, only one Si,Si bond is broken upon irradiation of 7 and the silacyclobutenyl radical 9 can be identified as the reaction product. The structure of radical 9, which in the absence of oxygen is persistent even at room temperature, has been elucidated by comparison of its experimental and calculated ESR spectra.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis of 5-Methylbenzo[b]thieno[2,3-c]isoquinolines and5-Methylbenzo[b]seleno[2,3-c]isoquinolines (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1353-1357 
    Details
    ISSN: 1434-193X
    Keywords: Heterocycles ; Rearrangements ; C-C coupling ; C-C coupling ; Cyclizations ; Isoquinolines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -5-Methylbenzo[b]thieno[2,3-c]isoquinolines and 5-methylbenzo[b]seleno[2,3-c]isoquinolines 11b,c have been prepared by Bischler-Napieralski cyclization of 2-acetamido-3-phenylbenzo[b]heteroarenes.
    Additional Material: 4 Tab.
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  • 10
    Electronic Resource
    Electronic Resource
    Isolation of Macrocyclic Metacyclophanes From the Attempted Synthesis of [7.0]Metacyclophanes of the Myricanone Series by Thorpe-Ziegler - Intramolecular Cyclization of Diaryls Substituted by ω-Cyanoalkyl Chains (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1527-1533 
    Details
    ISSN: 1434-193X
    Keywords: Cyclophanes ; Myricanone ; Diaryls ; C-C coupling ; Dinitriles ; Condensation reactions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The syntheses of the diaryls 14 and 21, substituted by two ω-cyanoalkyl chains (one on each ring), are described. Treatment of the unsymmetrical diaryl 14 with NaN(Me)Ph in a Thorpe-Ziegler reaction failed to give any definite product. Under the same conditions the symmetrical diaryl 21 led to an isomeric mixture of dimeric enaminonitriles 24. Mild acidic hydrolysis of the latter yielded the isomeric β-ketonitriles 25, whereas more drastic hydrolytic conditions led to the macrocyclic diketone 26.
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