Biphenylene synthesis

Only a few building blocks are available for the synthesis of ester-containing rigid mesogenic units, namely dihydroxy-, dicarboxy-, or (hydroxy, carboxy)-l,4-phenylenes, 4,4,-biphenylenes, and 2,6-, 1,4-, or 1,5-naphthylenes (Table 2.15). 

In 1996, Wegner et al. published the synthesis of poly(oligophenylenevinyle-ne)s (96), consisting of biphenylene-, terphenylene- and quinquephenylene moieties as aromatic building blocks, via Suzuki-type aryl-aryl cross coupling of AA/BB-type monomers [121]. By judicious choice of the arylene moieties, the optical properties of the resulting polymers can be tailored within a wide range. 

Harris and Hsu modified the structure of the rigid-rod poly(pyro-mellitimides) so they would display solubility in common organic solvents [59]. The approach involved the synthesis of 3,6-diphenylpyromellitic dianhydride and its polymerization with various pendent 4,4 -biphenylene diamines. The polymers, represented by structure XIV, were prepared in refluxing m-cresol... 

Chlorexolone as diuretic, 1, 174 Chlorides synthesis, 1, 448 Chlorin, 4, 370 metal chelates, 4, 391 Chlorin, dihydroxy-, 4, 393 Chlorin e6, 4, 404 trimethyl ester, 4, 398 synthesis, 4, 416 Chlorination pyridazines, 3, 20, 21 Chlorine trifluoride bonding, 1, 564 Chlorin-phlorin, 4, 398 Chlorins, 4, 378 absorption spectra, 4, 389 formation, 4, 394 molecular structure, 4, 385 oxidation, 4, 395 Chlorisondamine chloride as hypertensive agent, 1, 176 Chlormethiazoles metabolism, 1, 235 Chlormethiuron against ectoparasites veterinary use, 1, 217 Chlormezanone as antidepressant, 1, 169 Chlorocruoroheme, 4, 380 Chlorofucin conformation, 7, 703 Chloronium iodide, biphenylene-reactions, 1, 566... 

Iodonium tetrafluoroborate, biphenylene-X-ray structures, 1, 566 Iodopropenylation alkyl halides, 1, 469 Ionenes uses, 1, 289 Ion exchange resins pyridine polymers and, 1, 308-309 Ionization potentials pyridines, 2, 135 cts- 3-Ionol synthesis, 3, 666 cis-/3-Ionone... 

A representative selection of [2]catenanes synthesized by this route is given in Table 10.1[14b, 15a, 16]. It is remarkable to note that the first [2]catenane synthesized (entry 2, Table 10.1) could be isolated in 74% yield [14,16], The final entry in the table is an example of an expanded version of the tetracationic macrocycle which incorporates a biphenylene spacer between the paraquat residues and can accommodate two n-stacked aryl rings within its cavity. The reaction results in the isolation of the [3]catenane product in 25% yield with very little (2%) [2]catenane isolated [16p]. A spectacular demonstration of the power of this approach by Stoddart and coworkers was the iterative synthesis of a [5] catenane which the authors dubbed Olympiadane after its resemblance to the Olympic rings [17]. 

The low-yield (14%) Wittig-type synthesis of the unusual compound 53 [Eq. (3)] is noteworthy, since this compound was the first known heterocyclic analog of biphenylene.58... 

An example of the systematic nomenclature for compounds in this group is cyclobuta[l,2-Z> 3,4-//jdipyridine in this review this compound will be named as an aza analogue of biphenylene, that is, 1,8-diazabiphenylene. The only structural types found in the literature are those described below although there seems no reason why other variants are unknown. No record of unsuccessful attempts at synthesis were revealed. 

Experiments, based on the hypothesis that the behaviour of suitably chosen (our italics) aromatic molecules on vigorous pyrolysis should closely or even exactly parallel the fragmentations of the corresponding molecular ions in the mass spectrometer , have led to an improved synthesis of biphenylene (R. F. C. Brown and Solly, 1966). The mass spectra of polycarbonyl compounds (29-31) were used as a guide to the selection of suitable precursors of biphenylene and its derivatives by... 

Figure 45 Synthesis of polymers with alternating binaphthylene and biphenylene units. (From Ref. 212.)...

Benzocyclobutadienes.3 Cobalt-catalyzed cotrimerization provides a short synthesis of the tetrasilylbenzo[3.4]cyclobuta[l,2-fc]biphenylene 1, which can be desilylated to the... 

The ease of performance and the reaction stereoconservation led to the synthesis of a large variety of compounds such as functionahsed biphenylenes [75], biphenanthrenes [76] and octahydro-binaphthyl [77]. 

The tetrazotization of m-phenylenediamine has been described also, under special conditions (nitrosylsulfuric acid in glacial acetic acid) a similar conversion of the ortho isomer has been accomplished. This procedure has been adaf>ted to the tetrazotization of certain naphthalene diamines. The simultaneous diazotization of two amino groups in the biphenyl series is illustrated by the synthesis of 4,4 -biphenylene-fejs-diazonium chloride and its 3,3 "dimethyl analog. ... 

The availability of benzocyclobutenes from cocycloadditions of 1,5-hexadiynes and hindered alkynes has been elaborated into an iterative synthesis of a variety of novel polycyclic biphenylene derivatives. 

Aiiiino-4-phenylthiazoles, from o-diazo-acetophenone and thiourea, 231 2-Amino-5-phenylthiazole, diuretic prope ties of Schiffs bases of, 167 synthesis of, by condensation of ammonia with At(ary 1-1,3-oxathiol-2-yIidine) tertiary iminium salts. 300 2-(p-Ammophenyl) thiazoles, syntheses of, 4,5-disubstituted derivatives of, 191 2-Amino5-substituted thiazoles, from o-haloaiddiydes and thiourea, 224, 225 /V,At -bis (2-Amino-4 substituted thiazolyl)-p biphenylene, from p-biphenylene dithiourea and o-halocarbonyl compounds, 243... 

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