- Synthesis and elaboration of all-cis-1,2,4,5-tetrafluoro-3- phenylcyclohexane: A polar cyclohexane motif
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A stereocontrolled synthesis of all-cis-1,2,4,5- tetrafluoro-3- phenylcyclohexane is developed as the first functionalised example of this polar cyclohexane motif. The dipolar nature of the ring, arising due to two 1,3-diaxial C-F bonds, is revealed in the solid-state (X-ray) structure. The orthogonal conformation of the aryl and cyclohexyl rings in all-cis-1,2,4,5- tetrafluoro-3-phenylcyclohexane, and in an ortho-nitro derivative, result in intramolecular 1hJHF and 2hJCFNMR couplings relayed through hydrogen bonding. The aryl group of all-cis-1,2,4,5-tetrafluoro-3-phenylcyclohexane is elaborated in different ways to demonstrate the versatility of this compound for delivering the motif to a range of molecular building blocks. A stereocontrolled synthesis of all-cis-1,2,4,5-tetrafluoro-3-phenylcyclohexane is developed as the first functionalised example of this polar cyclohexane motif. The dipolar nature of the cyclohexane ring is explored and the aryl ring is elaborated in different ways to demonstrate its versatility as a molecular building block (see figure).
- Durie, Alastair J.,Fujiwara, Tomoya,Cormanich, Rodrigo,Buehl, Michael,Slawin, Alexandra M. Z.,O'Hagan, David
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- 3-tert-Butyl-Substituted Cyclohexa-1,4-dienes as Isobutane Equivalents in the B(C6F5)3-Catalyzed Transfer Hydro-tert-Butylation of Alkenes
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Cyclohexa-1,4-dienes with a tert-butyl group at C3 are shown to function as isobutane equivalents when activated by the strong boron Lewis acid tris(pentafluorophenyl)borane. The hitherto unprecedented transfer hydro-tert-butylation from one unsaturated hydrocarbon to another is achieved with 1,1-diarylalkenes as substrates, thereby presenting itself as a new way of incorporating tertiary alkyl groups into carbon frameworks. Transient carbocation intermediates give rise to competing reaction pathways that could not be fully suppressed.
- Keess, Sebastian,Oestreich, Martin
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supporting information
p. 5925 - 5928
(2017/05/05)
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- Substituent effects on the dehydration of arene hydrates in aqueous solution
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Rate constants have been determined by UV spectrophotometry at 25 °C for the acid-catalyzed dehydration of different types of monocyclic arene hydrates including those substituted at the 1-, 2- or 3-positions. General acid catalysis was not observed, and linear plots of pseudo-first-order rate constants for dehydration against hydronium concentration were obtained. A Hammett plot of the second-order rate constants for acid-catalyzed dehydration, kH (M-1s-1), of unsubstituted- (8a), 3-substituted (8b, 8c, 8d, 8e) and 1-substituted-benzene hydrates (14f and 14h) shows an excellent correlation with σ+ values and yields a large negative ρ-value of -6.5. The results are consistent with rate-determining formation of a benzenium ion in which direct mesomeric interaction with the substituent occurs, presumably permitted by the coplanar arrangement of the diene and carbocation centre in the intermediate. Data points for 2-substituted arene hydrates (13f, 13g, 13h, 13i) deviate negatively from the Hammett plot as direct mesomeric interaction with the substituent is not possible in the corresponding benzenium intermediates. Copyright 2013 John Wiley & Sons, Ltd. A large negative ρ-value of -6.5 is obtained in a correlation of rate constants for the acid-catalyzed dehydration of arene hydrates with σ+ values. Copyright
- O'Mahony, Michelle J.,More O'Ferrall, Rory A.,Boyd, Derek R.,Lam, Casey M.,O'Donoghue, Annmarie C.
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supporting information
p. 989 - 996
(2014/01/06)
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- 4-biphenylylcalcium iodide and 9-phenanthrylcalcium bromide: Grignard-type reagents of polycyclic aromatic hydrocarbons
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Reduced to the max: Halogenated polycyclic hydrocarbons can be reduced with calcium via two different pathways yielding radical anions due to electron transfer into the π*-orbital or Grignard-type reagents due to insertion of Ca into the carbon-halogen bo
- Koehler, Mathias,Langer, Jens,Fischer, Reinald,Goerls, Helmar,Westerhausen, Matthias
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supporting information
p. 10497 - 10500
(2013/08/23)
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- Preparation of 1-phenylcyclohexa-2,5-diene-1-carboxylates and their use in free-radical mediated syntheses
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Synthetic routes to pure 1-phenylcyclohexa-2,5-diene-1-carboxylic acid and derived esters were developed. Esters containing appropriately unsaturated side chains generated the corresponding alkenyl radicals and hence gave good yields of 5-exo ring closure products in organotin-free reactions. Extrusion of phenyl radicals from the intermediate cyclohexadienyl type radicals was not observed, and this alternative β-scission did not compete under any conditions. Yields from alkylations of olefins in analogous intermolecular processes were, however, poor. As a spin-off from the research, it was found that 1-phenylcyclohexa-2,5-diene-1-carboxylic acid (6) was a useful source of hydroxyformyl (formate) radicals in organic solvents.
- Baguley, Paul A.,Jackson, Leon V.,Walton, John C.
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p. 304 - 309
(2007/10/03)
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- Dehalogenation of aromatic halides using metallic calcium in ethanol
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The scope and limitations of the dehalogenation of aromatic halides 1 and 4a-p using metallic calcium in ethanol at room temperature were revealed. The cleavage of the carbon-chlorine bond on the aromatic ring bearing electron-donating group was difficult compared to the one bearing electron-withdrawing group. Moreover, we applied this method to the dechlorination of polychlorinated biphenyls (PCBs) in transformer oil. It was also found that the dechlorination took place easily under mild conditions. The existence of PCBs residue in the reaction at room temperature was less than 0.04% according to the GC-MS analysis. The chlorine was identified as calcium chloride.
- Mitoma,Nagashima,Simion,Simion,Yamada,Mimura,Ishimoto,Tashiro
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p. 4145 - 4148
(2007/10/03)
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- Thermal and Photochemical Electron-Transfer Reactions of 4-Chlorobiphenyl with Lithium Diisopropylamides and Diisopropylamine
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A reaction of 4-chlorobiphenyl with lithium diisopropylamide in a polar solvent gave 3- and 4-(diisopropylamino)biphenyl together with biphenyl, similar to the case of photoinduced reactions of 4-chlorobiphenyl with diisopropylamine.A common electron-transfer mechanism is proposed.
- Tanaka, Yoshio,Tsujimoto, Kazuo,Ohashi, Mamoru
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p. 788 - 790
(2007/10/02)
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- Photokondensation in Benzoldampf durch einzelne UV-Laserblitze
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Benzene vapour was photolysed with single pulses of an Excimer laser at wavelength of 248 nm.The formation of aerosol could be followed using Laser light absorption and scattering, gaseous products were analysed by gas-chromatography (and GC-MS).At low laser energies mainly biphenyl and phenylcyclohexadiene are formed, from laser energies of about 30 mJ/(pulse cm2) upward multiphotonabsorption becomes important and C2H2 formation increases strongly.At the conditions applied aerosol is formed mainly via condensation of biphenyl and phenylcyclohexadiene.At approximately constant degree of photolysis an increase of temperature reduces the supersaturation of these two compounds, and the formation of aerosol decreases; it also decreases when the laser energies and benzene concentrations are reduced.An increase of total pressure and of benzene partial pressure up to a certain level increase the aerosol formation.The growth with time of particle number density and size is described. - Keywords: Benzene photolysis / Photocondensation / Aerosol / Excimer laser / Ignition
- Kauer, M.,Wagner, H. Gg.
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p. 109 - 128
(2007/10/02)
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