- Influence of alkyl substitution on the gas-phase stability of 1-adamantyl cation and on the solvent effects in the solvolysis of 1-bromoadamantane
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1-Adamantyl cations having three methyl groups or one, two, or three isopropyl groups on the 3-, 5-, and 7-positions were found by FT ICR to be more stable than the 1-adamantyl cation and that the stability increases with the number of isopropyl group. The relative stabilities calculated by PM3 were in good agreement with the experimental results. In contrast, the sequence of the rates for the solvolysis in nonaqueous solvents are 3,5,7-(Me)3-1-AdBr 3-1-AdBr 3-1-AdBr. The rates of solvolysis of 3,5,7-(i-Pr)3-1-AdBr and 3,5,7-(n-Pr)3-1-AdBr relative to 1-AdBr at 25 °C are 15 and 3.8 in EtOH, respectively, but markedly decreases with the increase in the amount of added water, reaching 0.84 and 0.15, respectively, in 60% EtOH. Reflecting these effects of water, the Grunwald-Winstein (GW) relationship for 3,5,7-(i-Pr)3-1-AdBr and 3,5,7-(n-Pr)3-1-AdBr against YBr is linear for nonaqueous alcohols (EtOH, MeOH, TFE-EtOH, TFE, 97% HFIP), but marked downward deviations are observed for aqueous organic solvents, in particular, aqueous ethanol and aqueous acetone. The effect of the alkyl substituents to diminish relative solvolytic reactivity in EtOH-H2O mixtures may be ascribed to a blend of steric hindrance to Bronsted base-type hydration to the β-hydrogens and hydrophobic interaction of the alkyl groups with ethanol to make the primary solvation shell less ionizing. The introduction of one nonyl group to the 3-position showed much smaller deviations in the GW relationship than the case of 3,5,7-(n-Pr)3-1-AdBr. The markedly decelerated solvolysis of alkylated 1-bromoadamantanes in aqueous organic solvents is a kinetic version of anomalously diminished dissociation of alkylbenzoic acids in aqueous ethanol and aqueous tert-butyl alcohol that was demonstrated by Wepster and co-workers a decade ago and ascribed to hydrophobic effects.
- Takeuchi,Okazaki,Kitagawa,Ushino,Ueda,Endo,Notario
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p. 2034 - 2043
(2007/10/03)
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- Selective C-H activation of alipathic hydrocarbons under phase-transfer conditions
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Bromination of alipathic hydrocarbons with NaOH/CBr4 under phase-transfer conditions selectively gives the tertiary bromide. In the absence of a tertiary C-H bond in the molecule, a secondary bond will be activated (see reaction equation). This conceptionally new system for alipathic C-H activation very likely relies on the initiation of single-electron transfer followed by a radical substitution with unusually high regioselectivity.
- Schreiner, Peter R.,Lauenstein, Oliver,Kolomitsyn, Igor V.,Nadi, Suad,Fokin, Andrey A.
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p. 1895 - 1897
(2007/10/03)
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- Reaction of Adamantane Alcohols with Bromine
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1-Hydroxyadamantane and 1-hydroxy-3,5,7-trimethyladamantane in the medium of liquid bromine are converted, correspondingly, into 1-bromoadamantane and 1-bromo-3,5,7-trimethyladamantane by substitution of the hydroxy group with molecular bromine. 1-Hydroxyalkyl derivatives of adamantane afford alkyl bromides by means of substitution of the hydroxy groups for bromine with both molecular bromine and, possibly, hydrogen bromide formed upon oxidation of alcohols with bromine. A scheme of substitution of the hydroxy group with molecular bromine is suggested.
- Baklan,Khil'chevskii,Kukhar'
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p. 498 - 505
(2007/10/03)
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- Contribution a l'etude des reactions d'alkylation et de polyalkylation de l'adamantane et de ses homologues
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A method for preparing alkyl derivatives of cage-structure compounds is proposed.It relies on the use of Grignard reactions with a high boiling point solvent.The reactions take place at atmospheric pressure.Methylation of adamantane, diamantane, and homoadamantane occurs with quantitative yield.With other primary alkyl groups, yields are better than 60percent.Competition between alkylation and secondary reactions is discussed on the basis of a free radical mechanism.
- Molle, G.,Dubois, J. E.,Bauer, P.
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p. 2428 - 2433
(2007/10/02)
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Liquid bromine as an electrophilic medium gives rise to skeletal rearrangements in a series of substrates: The Beckmann rearrangement of methyl 1-adamantyl ketone oxime to 1-acetamidoadamantane; the pinacone-pinacoline rearrangement; the cyclization of me
- Baklan, V. F.,Antipenkova, L. S.,Zakharchenko, L. I.,Fesenko, T. E.,Kukhar, V. P.
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p. 1102 - 1105
(2007/10/02)
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- High-Yield Direct Synthesis of a New Class of Tertiary Organolithium Derivatives of Polycyclic Hydrocarbons
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For the first time, 1- and 2-adamantyllithium, 1-diamantyllithium, 3,5,7-trimethyl-1-adamantyllithium, 1-twistyllithium, 3-methyl-7-noradamantyllithium, 1-triptycyllithium, and 3-homoadamantyllithium have been directly synthesized from the reaction of an organic halide and lithium metal.By use of certain experimental parameters, the phenomena at the metal-solution interface are controlled, thereby resulting in exceptionally high yields of this new class of organometallic compounds (>75percent, except in the case of 3-homoadamantyllithium).Competition between formation of the organometallic compound and formation of solvent-attack byproducts is determined by the degree of adsorption of the transient species (anion radical RX-. or radical pair R..Li) generated at the metal surface during attack by the halogenated derivative.
- Molle, G.,Bauer, P.,Dubois, J. E.
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p. 2975 - 2981
(2007/10/02)
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- Structure-Anti-Parkinson Activity Relationships in the Aminoadamantanes. Influence of Bridgehead Substitution
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A limited series of bridgehead alkyl-, dialkyl- and trialkyl-substituted amantadines was synthesized and tested for potential anti-Parkinson activity as dopamine (DA) agonists.The compounds were evaluated using a battery of three murine bioassays, including stimulation of locomotor activity, induction of circling in animals with unilateral striatal lesions, and reversal of reserpine/α-methyltyrosine induced akinesia.Apparent mechanistic differences were seen between the methyl-substituted series and the ethyl-substituted series.While activities in both series increase with increasing liphophilicity, the methyl series (1b-d), as well as amantadine itself (1a) exhibits only indirect DA agonist activity, as evidenced by ipsilateral rotation in the circling model and no significant difference from control in reversal of akinesia.The ethyl series (1e,f) exhibits weak but reprodicible direct DA agonist activity, as shown by contralateral rotation in the circling assay for 1e and reversal of akinesia by 1e and 1f.The 3-n-propyl derivative (1g) was devoid of any DA agonist activity.
- Henkel, James G.,Hane, Jeffrey T.,Gianutsos, Gerald
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