- A simple synthetic method of cyclophanes by Lanthanoid-mediated coupling of bis(bromomethyl)benzenes
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The coupling of bis(bromomethyl)benzenes with iodized samarium, cerium or misch metal gives cyclophanes in satisfactory yields in a short time.
- Takahashi, Senji,Mori, Nobuo
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- Samarium(II) Diiodide Mediated Coupling of Bis(bromomethyl)arenes. Facile Synthesis of n>Cyclophanes without using High-Dilution Techniques
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In the presence of samarium(II) diiodide (Sml2), coupling of 1,3- and 1,4-bis(bromomethyl)benzenes proceeds smoothly to give their cyclic and acyclic oligomers.Use of 1.2 equiv. of Sml2 gives 1,2-bis(3- and 4-bromomethylphenyl)ethanes, respectively, in 95percent yield, and the use of 5.0 equiv. of Sml2 affords n>metacyclophanes and n>paracyclpphanes (n = 2, 3 and 4), respectively, in satisfactory yields.By using 5.0 equiv. of Sml2, 2-bromo- and 2-methoxy-1,4-bis(bromomethyl)benzenes and 1,4- and 2,6-bis(bromomethyl)naphthalenes each give only one of several expected isomeric cyclophanes as the major cyclic oligomer.
- Takahashi, Senji,Mori, Nobuo
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p. 2029 - 2032
(2007/10/02)
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- Preperations and Reactions of Symmetrical Dimethylenebiphenyl Dianions; Conformations of -o-Cyclophanes. A Simple NMR method for Determining Twist Angles in Biphenyls
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With n-butyllithium / potassium tert-butoxide, a proton is removed from each methyl group of the symmetrical dimethylbiphenyls to give dianions in good yield.The reactions of these dianions with alkyl halides, dialkyl sulfates, trimethylchlorosilane, trimethylchlorogermane, α,ω-dihalides, and oxidizing agents were found to provide the best routes to many symmetrically substituted biphenyls, including - and cyclophanes.NMR and molecular mechanical studies of some of these cyclophanes gave information on their preferred conformations.An NMR method for determining the angle of twist in biphenyls from the chemical shifts of the ortho hydrogens is developed.
- Bates, Robert B.,Camou, Fernando A.,Kane, Vinayak V.,Mishra, Prasana K.,Suvannachut, Kessara,White, James J.
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p. 311 - 317
(2007/10/02)
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