- Gold-Mediated Isomerization of Cyclooctyne to Ring Fused Olefinic Bicycles
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Isomerization reactions of cyclooctyne mediated by N-heterocyclic carbene supported gold(I) leading to ring-contraction and the formation of 5/5-fused bicyclic alkenes have been observed. Isolation and complete characterization, including X-ray structural data of the cationic gold(I) complexes featuring the precursor alkyne and the product alkenes are also described. Gold catalyzes the isomerization of cyclooctyne leading to alkenes featuring two fused five-membered rings.
- Das, Animesh,Hua, Yuanda,Yousufuddin, Muhammed,Cundari, Thomas R.,Jeon, Junha,Dias, H.V. Rasika
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p. 995 - 1001
(2016/03/15)
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- Functionalization of saturated hydrocarbons. High temperature bromination of octahydropentalene. Part 19
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The synthesis and thermal bromination of octahydropentalene was studied. The reaction afforded 1a,3a,4b,6b-tetrabromo-1,2,3,4,5,6-hexahydropentalene (14) with remarkable regio- and stereospecificity. The structure of the product was determined by 1H and 13C NMR data and single X-ray structural analysis. The treatment of octahydropentalene with tenfold bromine gave the octabromopentalene derivative. The formation mechanism of the products is discussed.
- Günba?, Duygu D.,Algi, Fatih,H?kelek, Tuncer,Watson, William H.,Balci, Metin
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p. 11177 - 11183
(2007/10/03)
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- Cyclooctatetraene dianion from 1,5-cyclooctadiene. A synthesis in the presence of naphthalene radical anion
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A novel synthesis of cyclooctatetraene dianion from 1,5-cyclooctadiene (1,5-COD) is described. The reaction of the potassium-naphthalene adduct with 1,5-COD proceeds at room temperature over 3 days in heptane/tetrahydrofuran to produce the target compound.
- Simons, Leslie H.,Lagowski
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p. 1771 - 1773
(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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- Reactions of enaminones with 1-nitroolefins. Scope and limitations of a polyquinane synthesis
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The reaction of several 2-aminocyclohex-2-en-1-ones with cyclic nitroolefins has been explored as a possible synthetic approach to polyquinanes. 2-Pyrrolidino, 2-piperidino and 2-morpholinocyclohex-2-en-1-one react with 1-nitrocyclopentene to provide substituted triquinanes. Reactions involving 5,5-dimethyl-2-morpholinocyclohex-2-en-1-one were unseccessful as were those using 4,4-dimethyl-1-nitrocyclopentene. 5-Methyl-2-morpholinocyclohex-2-en-1-one and 1-nitrocyclopentene provide the corresponding triquinane, plus a by-product in which the amino substituent has been lost. The reactions of other selected nitroolefins have been carried out, and the products are described. The results of these reactions are rationalized in terms of an inverse electron demand Diels-Alder reaction to afford an intermediate oxazine N-oxide, which then undergoes further transformations to afford the observed products.
- Huffman,Cooper,Miburo,Pennington
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p. 8213 - 8228
(2007/10/02)
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- Differential Bridging in the Solvolysis of Epimeric Bicyclic Sulfonates. Norbornanes, Part 17
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The solvolysis rates and products of the 2-exo- and 2-endo-norbornyl, bicyclooct-8-yl, bicyclonon-2-yl, bicyclooct-6-yl, bicyclooct-2-yl and bicyclonon-6-yl p-toluenesulfonates 10-15, respectively, are reported.The exo/endo rate ratios for these epimeric secondary tosylates in 80percent EtOH varied from 1125 for 11 to 1.6 for 15.The relative rates varied between 2278 for exo-10 and 4E-3 for endo-11.The hydrolysis products were mainly rearrenged alcohols and olefins.The unrearrenged alcohols from the exo-tosylates were formed with complete or predominant retention of configuration, whereas those derived from the endo-tosylates were mostly inverted.These results confirm the hypothesis that relative rates, as well as products, are largely determined by the degree of bridging between the cationic center and a dorsal C-atom in the transition state and in the resulting ion pairs.Since bridging is a directed bonding interaction, it is subject to the same angle and conformational strains as ordinary covalent bonds.But bridging requires less geometrical change than the formation of normal bonds and of nonclassical ions.
- Grob, Cyril A.,Waldner, Adrian,Zutter, Ulrich
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p. 717 - 729
(2007/10/02)
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- The Metallation-Elimination Reaction, II. Monocyclic Anions and Polyanions
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Equimolar mixtures of n-butyllithium and potassium tert-amyloxide effect metallation and metal hydride elimination of cyclic olefins directly to give conjugated anions and polyanions in a single operation. 1-Methyl-1-cycloalkenes or methylenecycloalkanes are particularly well suited and give highly unsaturated products.Odd-membered rings eliminate better than their even-membered counterparts, and eight-membered rings eliminate particularly slowly.Reactions with methyl iodide and trimethylsilyl chloride proceed smoothly in high yield.
- Wilhelm, Dieter,Clark, Timothy,Friedl, Thomas,Schleyer, Paul von Rague
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p. 751 - 760
(2007/10/02)
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- Photolysis of the Cyclooctadienyl Anion
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Visible or long-wavelength ultraviolet excitation of alkali metal salts of cyclooctadiene leads to electron exchange.Primary photoinduced electron transfer has been used to initiate the geometrical isomerization of cis-stilbene and the photosubstitution of aryl halides.Mechanistic details for these reactions are presented.Electron exchange so dominates the excited-state reactivity of this pentadienyl anion that neither potential pericyclic reaction (i.e., electrocyclization or sigmatropic shifts) nor photoinduced cis-trans isomerization can be detected.
- Fox, Marye Anne,Singletary, Nancy J.
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p. 3412 - 3421
(2007/10/02)
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- Hydrogenation Reactions over Catalysts of Very Strong One-Electron Donor Properties
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The results of studies on simple alkenes and conjugated double bonds systems hydrogenation reactions over the catalysts with very strong one-electron donor properties have been presented.The catalysts have been obtained by evaporation of alkali metals onto magnesium oxide surface.High catalytic activity and selectivity of the systems under investigation have been observed.
- Kijenski, Jacek
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