Dibenzo biphenylene

Synonyms AI3-00039 AIDS-18166 (l,r-Biphenyl)-2,2 -diyl oxide Biphenylene oxide 2,2 -Biphenylene oxide CCRIS 1436 CPD-926 Dibenzo[Ac/ furan Dibenzol[Ac/ furan Diphenylene oxide EINECS 205-071-3 NSC 1245. 

The currently accepted name for (1) in Chemical Abstracts is dibenzothiophene, although biphenylene, diphenylene, or biphenylylene sulfide are still used, especially in the Russian literature. Occasionally 9-thia-fluorene is used and recently, in one instance, dibenzo[6,d]thiophene. An alternative numbering system for (1) is met with on occasions in which C-4 is taken as C-1, as in carbazole. In the absenee of moleeular diagrams this system must be detected by reference to the chemistry described. For example, in a few dyestuff patents 2,7-diaminodibenzothiophene 5,5-dioxide is referred to and this is obviously the 3,7-diamino compound, also known as benzidine sulfone. 

Ein Dibenzo-cycloheptadien-System (Dibenzo[a.c]cyclohepten-System) liegt bei den einfach und doppelt verbriickten Biphenylen der allgemei-nen Struktur 16 und 17 (X = CRg) vor. Diese Verbindungsklasse bean-spruchte im Zusammenhang mit der Atropisomerie der Biphenyle 4a>4 >. 

Yamashiro S (1941), Bull. Chem. Soc. Japan 16 6-15. Studies on the derivatives of biphenylene oxide. V. Bromoderivatives of biphenylene oxide" van Zorge JA., van Wijnen JH., Theelen RMC, Olie K., van den Berg M (1990), Chemosphere, 19 1881-1895. Assessment of the Toxicity of Mixtures of Halogenated Dibenzo-p-dioxins and Dibenzofurans by Use of Toxicity Equivalency Factors (TEF) . 

Synonyms 2,2 -Biphenylene oxide 2,2 -bipheny-lylene oxide dibenzo(B,D)furan diphenylene oxide... 

Biphenylene 56 is formally the dibenzo derivative of cyclobutadiene. However, because of its unusual physical and chemical properties, it is more accurately viewed... 

Table 2. Calculated ringcurrent intensities and chemical shifts in benzene, biphenylene, bcnzo[a]biphenylenc, bcnzo[i>]biphcnylenc and dibenzo[a, cjbiphenylene9 ci...

Benzyne is a necessary intermediate in the diazotization of 2-[(2-acetoxyethyl)sulfinyl(and sulfonyl)]anilines 107 and 116, but a detailed study of the way it is formed gave some surprises . Products from the aprotic diazotization of 107 included biphenylene 67 and dibenzo-l,4-thioxin 112. EPR evidence for radical intermediates was obtained. Formation of 112 requires cleavage of the S—O bond, most probably via benzoxathiete 110 as shown. Although yields of 67 and 112 were low, when the diazotization was carried out in the presence of benzyne traps such as diphenylisobenzofuran or anthracene, respectable yields (30-40%) of the corresponding benzyne cycloadducts were obtained. 

An alternative route to benzyne from 107 might involve formation and decomposition of 1,2,3-benzthiadiazole-l-oxide 114. However, independent synthesis of 114 showed that it is remarkably stable its thermal decomposition requires a temperature of 135 C Consequently 114 cannot be an intermediate in the room-temperature diazotizations. This is in sharp contrast with 1,2,3-benzothiazole-1,1-dioxide 115, which is a well-known benzyne precursor at 0 °C and which explodes spontaneously in the solid state. It is a plausible intermediate in the diazotization of 116, which affords biphenylene and dibenzo-... 

Biphenylene(I), the dibenzo derivative of cyclobutadiene, has been known for more than forty years as a stable crystalline solid. 

The benzyne involving reactions have been employed in the s)mthesis of various biphenylenes. Namely, 3-amino-2-naphthoic acid (524) was converted to the corresponding diazonium salt 525 with isopentyl nitrite in the presence of a catalytic amount of trifluoroacetic acid in 76% yield. The latter was decomposed in boiling 1,2,3-trichloropropane to give dibenzo[Z),/i]biphenylene (526) in 2.7% isolated yield [95], Scheme 51. 

Low MW polymer at 490°C produces benzene, phenol, benzaldehyde, 4-hydroxybenzaldehyde, diphenyl ether, biphenylene, benzophenone, series of -H, -OH and -CHO terminated chain fragments containing < 8 aromatic units and fragments containing dibenzo ran units. 

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