- Synthesis and intramolecular hydrogen bonding of syn -9-hydroxy-18- substituted [3.3]metacyclophanes
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Various anti-9-methoxy[3.3]metacyclophane-2,11-diones are exclusively obtained by the coupling reaction of the corresponding 1,3-bis(bromomethyl) benzenes and 2,6-bis[2-isocyano-2-(tolylsulfonyl)ethyl]-4-tert-butylanisole in dimethylformamide (DMF) with an excess of sodium hydride, from which the corresponding syn-[3.3]metacyclophanes (MCPs) are synthesized via anti/syn-isomerization during the Wolff-Kishner reduction. Demethylation of syn-9-methoxy[3.3]MCPs with BBr3 afforded the corresponding syn-9-hydroxy[3.3]MCPs in good yields. The existence of the strong intramolecular hydrogen bonding between the 9-hydroxy group and the 18-substituents, such as F, OH, and OMe groups at the opposing aromatic rings, are observed in solution and in the solid state. A distinct low-field shift of the phenolic OH proton was observed in the 1H NMR spectrum compared with that of the 18-unsubstituted analog. Furthermore, O-H...F through-space coupling was observed.
- Tazoe, Kazuya,Feng, Xing,Sharma, Bigyan,Miyamoto, Shinpei,Yamato, Takehiko
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- Nucleophilic aryl fluorination and aryl halide exchange mediated by a CuI/CuIII catalytic cycle
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Copper-catalyzed halide exchange reactions under very mild reaction conditions are described for the first time using a family of model aryl halide substrates. All combinations of halide exchange (I, Br, Cl, F) are observed using catalytic amounts of Cus
- Casitas, Alicia,Canta, Merce,Sola, Miquel,Costas, Miquel,Ribas, Xavi
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supporting information; experimental part
p. 19386 - 19392
(2012/01/15)
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- Mechanism of aromatic hydroxylation in a copper monooxygenase model system. 1,2-methyl migrations and the NIH shift in copper chemistry
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The NIH shift mechanism appears to be operative in a copper monooxygenase model system involving dicopper ion complex mediated O2 hydroxylation of an arene substrate. Previous studies have shown that when a dicopper(I) complex containing two tridentate PY2 units (PY2 = bis[2-(2-pyridyl)ethyl]amine) which are linked by a m-xylyl group, i.e., [Cu2(XYL-H)]2+ (1), is reacted with dioxygen, a Cu2O2 intermediate forms and hydroxylation in the intervening 2-xylyl position occurs. Here, corresponding reactions of 2-methyl substituted analogues [Cu2(Me2XYL-CH3)]2+ (4) and [Cu2(XYL-CH3)]2+ (5) are described in detail. Oxygenation of these causes xylyl hydroxylation reactions producing new phenol products, with concomitant 1,2-migration of the methyl group, loss of one PY2 ligand arm, and formaldehyde formation. Manometric O2 uptake experiments and an 18O2 labeling study confirm that the stoichiometry of these reactions are consistent with that observed for monooxygenases. A reaction carried out using a dinucleating ligand which has been deuterated in benzylic positions confirms that the CH2O product is derived from this carbon atom, a result also consistent with migration of the 2-methyl group. A small yield of methylbis[2-(2-pyridyl)ethyl]amine (MePY2) is consistently obtained, and experiments suggest this may be derived from the reduction of an intermediate iminium salt [CH2=N[CH2CH2PY]2]+ (PY = 2-pyridyl). The hydroxylation induced 1,2-methyl migrations observed here are reminiscent of the NIH shift reactions previously observed only in iron hydroxylases and suggest that the copper ion mediated reactions proceed by the electrophilic attack of a Cu2O2 intermediate upon the proximate aromatic substrate. A detailed mechanism is proposed and discussed in terms of the known O2 reactivity and structure of these dinuclear copper complexes. The biological relevance and significance of this monooxygenase model system is also discussed.
- Nasir, M. Sarwar,Cohen, Brett I.,Karlin, Kenneth D.
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p. 2482 - 2494
(2007/10/02)
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- Metacyclophanes and Related Compounds. Part 16. Preparation of 8-Fluoro-t-butylmetacyclophanes and their Treatment with Aluminium Chloride-Nitromethane in Benzene
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The preparation of 8-fluoro-t-butylmetacyclophanes (5) are described.Dithiametacyclophane (3) and metacyclophane bis(sulphones) (4) were obtained as a mixture of transoid and cisoid conformers, but metacyclophanes (5) were exclusively obtained as the transoid conformer after pyrolysis of the sulphones (4).AlCl3-MeNO2-Catalyzed trans-t-butylation of 8-fluoro-16-methyl-5,13-di-t-butylmetacyclophane (5a) in benzene under a variety of conditions faild to give 8-fluoro-16-methylmetacyclophane (32) but, instead, the tetrahydropyrenes (33) and/or (34) were obtained depending upon the conditions used.Internally substituted metacyclophanes were isomerized to the strainless metacyclophanes and these were then oxidized to the tetrahydropyrene (33).
- Yamato, Takehiko,Arimura, Takashi,Tashiro, Masashi
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