Phenyl group, introduction into

The most commonly used siloxane modifiers are those having phenyl, trifluoro-propyl and cyanopropyl substituents. Introduction of phenyl units into the polydimethylsiloxane backbone either in the form of methylphenylsiloxane or diphenyl-siloxane increases the thermal and oxidative stability, glass transition temperature and the organic solubility characteristics of the resulting copolymers. At low levels (5-10 percent by weight) of incorporation, bulky phenyl groups also break up the regularity of polydimethylsiloxane chains and inhibit the crystallization (Tc... 

The viabihty of this synthetic approach to the introduction of a carboxylic acid fimction at C2 has been demonstrated in two ways. Following lithium diphenylcuprate addition to 564, the newly introduced phenyl group is subsequently degraded by ozonolysis to provide 567. Alternatively, reaction of 564 with diethylaluminium cyanide in toluene gives 568 which is also conveniently transformed into 567... 

Introduction of an oxygen bridge into the triphenylmethane dye molecule leads to the xanthene dyes. The color is shifted from blue to red. The restricted rotation of the phenyl groups inhibits radiationless de-excitation and gives rise to very strong fluorescence. Rhodamine B (14) is used for dyeing paper [11] and as a laser dye. 

Introduction of a phenyl group into the 6-position of thieno- or pyrrolo[c[-tropylium ions (e.g., transition from 228 to 230) shifts the 5- and 7-methyl protons to high field (0.4 ppm) consequently, noncoplanarity of the 6-phenyl ring and heterocyclotropylium system must be concluded (68-ZOR907). 

Complex 49 catalyzes, among other reactions, the addition of morpholine to methylacrylonitrile giving the amination product with modest selectivity (37% ee) (Scheme 35). In order to obtain catalytically active species with palladium, complex 48 was converted into dicationic derivatives of the general type [Pd(NCCH3)(PCP)](PF6)2. Using this catalyst, the addition of morpholine to methylacrylonitrile could be achieved with 47% ee. Further improvement in selectivity was obtained by the introduction of methyl substituents at the 3- and 5-positions of the phenyl groups in diphenylphosphanyl derivative leading to ee s of over 70% [94]. 

Successive introduction of phenyl groups into positions-2 and -6 (entries 1-3 of Table XIX) increases the rate by factors of 3.4 and 5.3, respectively. An... 

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