Biphenyl derivatives structures

The knowledge acquired from stoichiometric experiments on the ortho effect allowed a series of new sequential reactions leading to biphenyl-derived structures to be worked out. 

Scott et al. [45] prepared diimine derivatives of 2,2 -diamino-6,6 -dimethyl-biphenyl (as structure 37 in Scheme 19) as copper chelates for the catalyzed cyclopropanation reaction. All catalysts were active in this reaction but enan-tioselectivities varied importantly according to the substitution pattern of the imine aryl group only ortho-substituted ligands (by chloride or methyl groups) led to products with measurable enantioselectivity for the model test reaction (up to 57% ee with 37). 

Reported structures for homobifunctional aryl azides include a biphenyl derivative and a naphthalene derivative (Mikkelsen and Wallach, 1976), a biphenyl derivative containing a central, cleavable disulfide group (Guire, 1976), and a compound containing a central l,3-diamino-2-propanol bridge between phenyl azide rings that are nitrated (Guire, 1976). The only commercially available homobifunctional photoreactive crosslinker is BASED. 

In contrast to binaphthyls, chiral biphenyl derivatives are challenging systems because their twist ability shows a strong dependence on the molecular structure, which does not conform to the empirical correlation rule described above. In fact, homochiral biphenyls 33-40 are characterized by P helicity along the biphenyl axis. In spite of this common feature, the twisting power spans from a highly positive value for 33-45 to a relatively negative value... 

Pyrazoline derivatives have attracted considerable attention, and their electrochemical oxidation, studied in aqueous277,278 and nonaqueous media,279-290 led to different products, depending on the structure of the starting pyrazoline and the media. The intermediate bis(pyrazolinyl-l)biphenyl derivatives are further oxidized at the applied potential to bis(pyrazolyl-l)-biphenyl derivatives. 

As is readily noted from the results summarized in Table 8E.13, enantioselectivity is very sensitive to a variety of factors such as the nucleophile and the nature of the allylic system as well as the ligand used. As expected, the enantioselectivity varied greatly with the structure of the nucleophile. Higher enantioselectivities were consistently obtained from the reactions of 2-cyclopentenyl phenyl ether than from the corresponding reactions of 2-cyclohexenyl ether. The biphenyl-derived DiPHEMP (7a) proved to be more effective than closely related BINAP (4) for this reaction. 

The alkali melt of lunarine gives, in addition to spermidine (87), the two biphenyl derivatives 92 and 93 (88). Although all but two carbon atoms of lunarine are accounted for by these results, a skeletal rearrangement has occurred during the formation of 92 from 91, which complicated the structural elucidation of this alkaloid [for discussion of this rearrangement, see Warnhof (89)]. 

Internal perfluoroalkenes react with trimethyl(perfluorophenyl).silanc under more forcing conditions than terminal alkenes. The reactions can also give biphenyl derivatives. An interesting dependence of the reaction results on the structure in the case of perfluorophenylation of isomeric perfluoro(methylpentenes) has been identified. Perfluoro(2-methylpent-2-ene) is transformed into pcrfluoro(2-methyl-3-phenylpent-2-cnc) (4) perfluoro(4-methylpent-2-cnc) forms pcrfluoro( 1.1,3-triinethy lindan) (6) as well as perfluoro(4-inethyl-2-phciiylpen t-2-ene) (5). 

Although biphenyl is slightly twisted, the angle of twist is small, therefore, conjugation between the rings is not affected. Biphenyl thus shows a very intense absorption band at 252 run (K-Band). Biphenyl derivatives with bulky substituents in the ortho positions are more stable in twisted conformations than in the planar conformation, which suffers serious non-bonded compressions from the juxtaposed substituents. The loss of conjugation in the twist conformation of 2,2-dimethylbiphenyl is reflected in its UV spectral data, which now structurally is like two moles of o-xylene. 

History and Concepts. A complementary approach for molecular structure calculations is available, and it is referred to as the molecular methanics or force field method it is also known as the Westheimer method. In 1946, twenty years after the impressive development of quantum theory, three papers appeared in the literature which applied classifical mechanical concepts to problems of chemical interest. Westheimer investigated the racemization of some optically active biphenyl derivatives. His work demonstrated the potential usefulness of molecular mechanics. The other two papers were attempts to tackle more complex problems. 

Almenningen, A., Bastiansen, O., Fernholdt, L., Cyvin, B. N., Cyvin, S. J., and Samdal, S. Structure and barrier of internal rotation of biphenyl derivatives in the gaseous state. Part I. The molecular structure and normal coordinate analysis of normal biphenyl and perdeuterated biphenyl. J. Molec. Struct. 128, 59-76 (1985). 

Aromatic sulfenamides give cation radicals that dimerize to biphenyl derivatives. The latter compound can suffer further oxidation, during which the N-S bond is cleaved, leading to a quinoid structure that can be oxidized to the corresponding cation radical [231] ... 

Sometimes the interactions typical for 1.2-disubstituted arenes have a formal correspondence in the decompositions of 2.2 substituted biphenyl derivatives. Thus the highly specific piperidine eliminations from 14330 as well as the formation of 146 correspond to the fragmentations of structurally analogous benzene derivative. 

The radical anion derived from 2-cyanodiphenyl ether underwent reversible dimerization resulting in a dianion relatively resistant towards further chemical reaction. The products observed after electrolysis were mainly phenol, diphenyl ether and 2, 4-dicyano-3-phenoxy biphenyl. The structure of the isolated biphenyl suggested that the radical anion dimerization had occurred via 2-4 coupling. 

Structurally Specific Interaction of Halogenated Dioxin and Biphenyl Derivatives with Iodothyronine-5 -deiodinase in Rat Liver... 

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