Phenyl-1,3-butadienes, structure

The structure of the T -butadiene complexes 23 has been established by an X-ray investigation on a monocrystal of 23b. The phenyl-butadiene ligand coordinates in a predominant ri -7i-fashion but with significant a -K-contribution [10]. 

Poly(2-phenylbutadienes) with a high cis content are also produced with the triisobuthyl-aluminum/titanium tetrachloride catalysts [349]. Phenyl-1,3-butadienes can also be considered as vinyl-substituted styrenes, which explains the effects on activities and microstructures. Poly(2-phenyl butadienes) occur in trans-, A, cw-1,4, 3,4, and 1,2 structures. Maximum conversions are achieved with a molar Al/Ti ratio of 1, which leads to the formation of 73% cis-, A and 27% 1,2 structures. At higher Al/Ti ratios the d -1,4 content goes up to 96%. The molecular weights are low, ranging from 2000 to 18,000. 

However, when 6-bromo-4-phenylpyrimidine reacts with lithium piperi-dide/piperidine instead of potassium amide/liquid ammonia, it was surprisingly found that the corresponding 4-phenyl-6-piperidinopyrimidine was not obtained. Rather, the product was a compound whose structure was established to be a Z/E mixture of 2-aza-4-cyano-3-phenyl-l-piperidino-1,3-butadiene (2) (70RTC129). The presence of a cyano group in structure... 

Phenylmethylsilanediol, synthesis, 42 155 Phenylsilanetriol, monosodium salts, 42 169 4 -Phenyl-2,2 6, 2 -terpyridine bis nickel complex, 30 74 molecular structure, 30 74 PhjtfluorenyllSiOH, 42 197 (Ph(Me2N)C-=Nli], 37 59-65 orientation of imino ligand, 37 61-63 (PhMe SiljCSiH OH, 42 244-245, 248 (PhMe SiljCsiMeHlOH), 42 191 Phosphaalkenes acyclic, 33 338-353 butadienes, 33 346-349 cumulenes, 33 352... 

Figure 1.2.5 Chemical structures of cis- and trans-1-phenyl-1,3-butadiene and their normal melting point, Tm, specific gravity, df, and the refractive index, nf.

The membrane structures and their preparation described above are just two examples. There are many variations of the basic preparation procedure resulting in slightly different products. Instead of styrene, often substituted styrenes such as methylstyrene or phenyl-acetate are used instead of divinylbenzene monomers such as divinylacetylene or butadiene are used. 

The configuration of all the previously described double Diels -Alder adducts has not been determined, although addition of the second diazene group to the cyclohexadiene moiety of the intermediate adducts is expected to occur anti to the cyclohexadiene substituent. In fact, a single an/7-bisadduct 6 was isolated from the reaction of 1,1,4,4-tetraphenyl-1,3-butadiene and 4-phenyl-3//-l,2,4-triazole-3,5(4//)-dione and the structure was inferred from H- and 13C-NMR studies10. 

Phenyl and alkenyl (—CH=CH2) substituents are electron releasing but they stabilize the product anions by resonance, and so styrene and butadiene can undergo both cationic and anionic polymerizations. Anionic mechanisms are more important, however, since they provide better control over the polymer structure (Chapter 9). 

In reality, the second possibility occurred (57), and the same was true for the adducts containing other olefins. Finally, we verified the presence of hydroxyl in structure (IV) through reaction with phenyl isocyanate. Thus, the convincing experiments of Hoffmann, Middleton, and R. Adams were confirmed by our decisive evidence, so that 7T-structures were condemned to fade from the scene for these compounds. However, to emphasize the behavioristic similarity with the 77-complcxes, I suggested the term quasicomplex for the compounds which are formed from metallic salts and olefins or acetylenes through addition to the 7T-bond. A number of such quasi-complex compounds were obtained and studied by us. In particular, we showed that butadiene or its homologs, contrary to the earlier opinion of Sand, also formed the quasi-complex adducts in water, e.g.,... 

In contrast, Rieke magnesium reacts with ( , )-1,4-diphenyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, isoprene, myrcene, or 2-phenyl-1,3-butadiene in tetrahydrofuran (THF) at ambient temperature to afford the corresponding substituted (2-butene-1,4-diyl)magnesium complexes in near quantitative yields. The structures of these complexes have not yet been determined except for (l,4-diphenyl-2-butene-l,4-diyl)magnesium, which has been shown to be a five-membered ring metallocycle [5]. Accordingly, the most likely structures for these complexes are five-membered metallocycles or oligomers. It is also possible that an equilibrium exists between these various forms. 

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