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  • Cyclizations  (12)
  • Wiley-Blackwell  (12)
  • Blackwell Publishing Ltd
  • Elsevier
  • 2000-2004  (12)
Collection
Keywords
Publisher
  • Wiley-Blackwell  (12)
  • Blackwell Publishing Ltd
  • Elsevier
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    A New Route to 2,7- and 7-Functionalized Labdanes (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1609-1615 
    Details
    ISSN: 1434-193X
    Keywords: Terpenoids ; Natural products ; Total synthesis ; Cyclizations ; Rearrangements ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A new route for the synthesis of 2,7- and 7-functionalized labdanes starts from (R)-carvone (1). 11-Nordrim-7-en-9-one (15) is an appropriate starting material for the total synthesis of hispanone (21), a biologically active furolabdane isolated from the Mediterranean medicinal plant Ballota saxatilis.
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  • 2
    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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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    Inter- and Intramolecular Crotyltitanation of Acetals: A Novel and Effective Route to Three- to Five-Membered Vinylcycloalkanes and Bicyclic Fused Compounds (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1483-1488 
    Details
    ISSN: 1434-193X
    Keywords: Titanium ; Acetals ; Cyclizations ; Synthetic methods ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---η3-Crotyltitanocenes react with acetals to produce homoallylic ethers. The intramolecular coupling involving tethered dienyl acetals provides a convenient access to vinylcycloalkanes and bicyclic fused compounds. This new cyclization reaction proceeds with a total regioselectivity in the exo fashion, and with good to excellent diastereoselectivity depending especially on the tether chain length.
    Additional Material: 3 Tab.
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  • 5
    Electronic Resource
    Electronic Resource
    1-Alkyl- and Azeto[1,2-a][1,5]benzodiazepine Derivatives in the Reaction of o-Phenylenediamine with 3-(Dimethylamino)propiophenones (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1973-1976 
    Details
    ISSN: 1434-193X
    Keywords: Benzodiazepines ; Heterocycles ; Azeto[1,2-a]-1,5-benzodiazepines ; Cyclizations ; Cycloadditions ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The reaction of o-phenylenediamine (4) with one, two or three equivalents of p-substituted 3-dimethylaminopropiophenone hydrochlorides 5a-e was studied. 4-Aryl-2,3-dihydro-1H-1,5-benzodiazepine derivatives 6a-e were obtained in good yields, along with the 1:2-adducts 7c-e and the unexpected 1:3-adducts rac-8c-e. The type of adduct formed is determined by the molar ratio of the reactants 4 and 5 and by the nature of the substituent in the para position of the propiophenone 5.
    Additional Material: 1 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Efficient Preparation of a Highly Strained Eleven-Membered Ring (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 155-163 
    Details
    ISSN: 1434-193X
    Keywords: Macrocycles ; Cyclizations ; Strained compounds ; Ketophosphonate ; Iodoalkyne ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Two strategies have been explored to build the highly strained eleven-membered ring 2, a potential precursor for the biosynthetic key intermediate of the protoilludane family: an intramolecular Horner-Wadsworth-Emmons olefination and an intramolecular Nozaki-Hiyama-Kishi type-ring closure.
    Additional Material: 4 Tab.
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  • 7
    Electronic Resource
    Electronic Resource
    Fluorine-Sacrificial Cyclizations as an Access to 5-Fluoropyrazoles (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 823-828 
    Details
    ISSN: 1434-193X
    Keywords: Fluorine-containing heterocycles ; Methyl trifluoropyruvate ; Fluoride elimination ; Cyclizations ; Hydrazone ; Hydrazine tautomerism ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Methyl 3-methoxy-2-trifluoromethylacrylate 1, readily prepared by Wittig reaction from methyl 3,3,3-trifluoropyruvate, has been treated with a number of aryl- (or hetaryl-) hydrazines. Under mild base-catalysis, the resulting 3-hydrazinoacrylates 6 undergo consecutive hydrogen fluoride elimination and intramolecular nucleophilic addition to afford methyl 1-(het)aryl-5-fluoropyrazole-4-carboxylates 7. 5-Aminopyrazoles 8 have been obtained by direct reaction of the ester 7a with a lithium amide, whereas 5-fluoro-1-phenylpyrazole-4-carboxamides 10 have been formed by condensation of the 5-fluoro-1-phenylpyrazole-4-carboxylic acid 9 with amines.
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  • 8
    Electronic Resource
    Electronic Resource
    Deoxyhydantocidin: Synthesis by Base-Catalyzed Spiro Cyclization and Interconversion with the 1′-Epimer (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1831-1840 
    Details
    ISSN: 1434-193X
    Keywords: Cyclizations ; Spiro compounds ; Nucleosides ; Isomerizations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Syntheses of the spiro nucleosides 2′-deoxyhydantocidin 3a and its 1′-epimer 3b are described. The newly developed route involves a Horner-Wadsworth-Emmons condensation of the phosphonate 16 with the erythrose derivative 15 affording a mixture of six isomers which was fully assigned by NMR spectroscopy. The mixture was directly converted into the final compounds in an efficient base-catalyzed cyclization reaction. A base-catalyzed interconversion between the two isomers was observed.
    Additional Material: 2 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis of New Seven-Membered Ring Cyclic Dipeptides From Functionalized β-Amino Acids (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 251-255 
    Details
    ISSN: 1434-193X
    Keywords: Amino acids ; coupling ; N-Substituted amide ; Cyclizations ; Cyclic dipeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---A short synthesis of new, functionalized seven-membered ring cyclic dipeptides is described. After the coupling of N-protected β-amino acids to N-substituted α-amino tert-butyl esters, the protective groups of the terminal functions were removed and the cyclization took place diastereoselectively in the presence of the coupling agent BOP. Amide substitution was found to be effective in promoting the cyclization of linear dipeptides.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis of Benzotri(benzonorbornadienes) (BTBNDs): Rigid, Cup-Shaped Molecules with High Electron Density within the Cavity (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1965-1971 
    Details
    ISSN: 1434-193X
    Keywords: Cup-shaped PAHs ; Host-guest compounds ; Host-guest chemistry ; Cyclizations ; Semiempirical calculations ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Cyclotrimerisation of benzo-polycyclic bromostannylalkenes 8a-d with Cu(NO3)2·3H2O in THF affords benzotri(benzonorbornadienes) 3a-d as a mixture of the syn and anti isomers. The ratio of syn to anti is close to the 1:3 statistical value in most cases (i.e. in cyclotrimers 3a,b,d), but highly in favour of the anti isomer in 3c, where steric hindrance by the methoxy groups plays an important role in the stereochemistry of the cyclotrimerisation. The substrates for the cyclotrimerisation, i.e. the bromostannyl alkenes 8a-d, were prepared from bromoalkenes 7a-d by treatment with base (LDA) and quenching with trimethyltin chloride. In turn, bromoalkenes 7a-d were prepared from alkenes 5a-d by radical bromination-elimination. The reaction conditions used were designed to minimise Wagner-Meerwein rearrangements that would lead to unwanted bromo isomers. The cup-shaped syn cyclotrimers 3a-d exhibit high electron density within the cavity as determined by AM1 semiempirical calculations of their electrostatic potential surfaces and are valuable substrates for supramolecular chemistry. As an example, it is shown that fullerene C60 is drawn into solution in acetonitrile by complexation with both the syn and anti trimer of benzonorbornadiene 3a.
    Additional Material: 1 Tab.
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  • 11
    Electronic Resource
    Electronic Resource
    Asymmetric Synthesis of 1,4-Disubstituted Tetrahydroioquinolines (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1319-1325 
    Details
    ISSN: 1434-193X
    Keywords: Asymmetric synthesis ; Tetrahydroisoquinolines ; Cyclizations ; Diastereoselective alkylation of Amides ; Phenylglycinol ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Bischler-Napieralski cyclisation of optically active β-substituted phenylethylamines 4a-c followed by diastereoselective reduction led to 1,4-disubstituted tetrahydroisoquinolines 6a-c and 8a-c. The same methodology afforded the 4-benzyl pyrroloisoquinolines 10.
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  • 12
    Electronic Resource
    Electronic Resource
    Reactions of Cadmium(II) Acetate with Acetoacetanilide and Methylacetoacetate Thiosemicarbazones: A Cyclization Process Leading to a Pyrazolone - The Molecular and Crystal Structures of the Free Ligands and the Complex [CdL2Py] (HL = 2-[Amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolone, Py = Pyridine) (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 83-89 
    Details
    ISSN: 1434-1948
    Keywords: Cadmium(II) pyrazolonates ; Thiosemicarbazones ; Cyclizations ; 2-[Amino(thioxo)methyl]-3-pyrazolone ; 1H-, 13C-, 113Cd-NMR spectra ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Acetoacetanilide- and methylacetoacetate thiosemicarbazones (HTSC1 and HTSC2, respectively) react with cadmium(II) acetate in methanol, giving complexes containing the ligand 2-[amino(thioxo)methyl]-5-methyl-2,3-dihydro-1H-3-pyrazolonate (L-). An X-ray diffraction study of the structures of HTSC1, HTSC2, HL, and [CdL2Py], identified the main structural changes in the cyclization process. Additionally, the coordination of the metal in the complexes [CdL(AcO)] · 2 MeOH and [CdL2] · 3 H2O was analyzed using IR spectroscopy in the solid state and 1H-, 13C-, and 113Cd-NMR spectroscopy in solution. On reaction with aqueous trifluoroacetic acid, both complexes releases the free pyrazolone, which can be easily isolated.
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