1,1 -dibromo-2,6-diphenyl-4-

PCBs and PCTs are particularly troublesome liquids because of their toxicity and persistence in the environment. They are defined as polychlorinated biphenyls, polychlorinated terphenyls, monomethyl-dibromo-diphenyl metliane, monomethyl-dichloro-diphenyl metliane or monomethyl-tetrachlorodiphenyl methane. With low electrical conductivity and heat resistance they found wide use as dielectric fluids and were formerly used as hydraulic fluids. PCBs have not been made in the UK since 1977 and whilst most new uses for the substance are banned in most countries, around two-thirds of the 1.5 million tonnes manufactured in Europe and the US prior to 1985 still remain in equipment such as transformers. PCTs have been used in the past in a restricted range of specialist industrial applications. 

In the photolysis of. -dibromo-diphenyl-diazomethane in toluene the geminate pair effect is observed 87). However, it is accompanied by the enhanced emission by the escape product 7. This means that the carriers of the original polarization were the free radicals, whose lifetime is obviously shorter than the nuclear relaxation time. 

Tellurane(IV) Dibromo-diphenyl-E12b, 539 [Ar4Sn + TeBr4), 541 (Ar2Te2 + Ar-N /CuBr2), 542 (Ar2Te2 + Ar-TeBr3)... 

The primary dihydro product (3) can be obtained by reduction of the quinoid (4). Compound 3, in which Ri = CeH= -CH= and Rj CgH can also be obtained by direct condensation of benzylidene selenosemicar-bazone with 2.3-dibromo-l,4-diphenyl-l,4-butanedione (Scheme 49). 

Chroman-4-one, 3-bromo-2-hydroxy-synthesis, 3, 856 Chroman-4-one, 2-/-butyl- H NMR, 3, 583 Chroman-4-one, 3-/-butyl- H NMR, 3, 583 Chroman-4-one, 2,3-dibromo-dehydrobromination, 3, 828 Chroman-4-one, 3,3-dibromo-dehydrobromination, 3, 828 Chroman-4-one, 2,3-dihalogeno-synthesis, 3, 856 Chroman-4-one, 2,2-dimethyl-mass spectra, 3, 617 Chroman-4-one, 2,2-diphenyl-synthesis, 3, 852 Chroman-4-one, 3-hydroxy-synthesis, 3, 856... 

B. l,l-Diphenyl-2-bromo-Z-acetoxy- -j>ropene. A 250-ml. flask equipped with a condenser is charged with 17.6 g. (0.050 mole) of 1,1-dibromo-2,2-diphenylcyclopropane, 12.5g. (0.075 mole) of silver acetate [Acetic acid, silver(l +) salt] (Note 4), and 50 ml. of glacial acetic acid, then immersed in an oil bath at 100-120° for 24 hours (Note 5). After cooling, the mixture is diluted with 200 ml. of ether and filtered. The ethereal filtrate is washed with two 100-ml. portions of water, two 100-ml. portions of aqueous saturated sodium carbonate, and finally with two 100-ml. portions of water. After drying over anhydrous sodium sulfate, the ether is removed on a rotary evaporator. Distillation of the resulting residue under reduced pressure yields 12.0 g. (72%) of the product, b.p. 142-145° (0.15 mm.), 1.6020-1.6023 (Note 6). 

The thermal solid-to-solid cyclization reaction of diallene derivatives also proceeds stereospecifically. Reaction of 1,6-diphenyl-1,6-di(p-tolyl)hexa-2,4-diyne-l,6-diol (113) with HBr gave meso- (114) and rac-3,4-dibromo-l,6-di-... 

Lewis, T. W. Curtin, D. Y. Paul, I. C. Thermal, photochemical and photonucleated thermal dehydration of /j-hydroxytriary I methanols in the solid state. (3,5-Dimethyl-4-hydroxyphenyl)diphenyl methanol and (3,5-dibromo-4-hyrdoxyphenyl)di phenyl methanol X-ray crystallography of (4-hydroxyphenyl)diphenyl methanol and its 3,5-dimethyl derivative. J. Am. Chem. Soc. 1979, 101, 5717-5725. 

Independently Volpin17 synthesized diphenyl cyclopropenone from diphenyl-acetylene and dibromo carbene (CHBr3/K-tert.-butoxide). This reaction principle of (2 + 1) cycloaddition of dihalocarbenes or appropriate carbene sources ( caibenoids ) to acetylenic triple bonds followed by hydrolysis was developed to a general synthesis... 

Attempts were reported119,129 to synthesize the ortho-linked diphenyl cyclo-propenone phenanthreno cyclopropenone 173 by dehydrohalogenation of the dibromo derivative 174 of dibenzo cyclohepta-l,3-diene-6-one. The only product isolated was the anhydride 175 of phenanthrene-9-carboxilic acid, which was shown not to arise from 173l29 ... 

After partial deary lation of the product obtained, using HBr, stereogenic germanium atoms are generated giving the d, l and meso forms of 1,2-diphenyl-1,2-dibromo-digermane, 102. 

Attempts to directly iodinate quinoxaline failed, and the synthesis of 2,3-diphenyl-5,8-dibromoquinoxaline is somewhat more involved (Scheme 9) [61]. Starting from ort/zo-phenylenediamine, reaction with SOCI2 gives benzothia-diazole in high yield. Bromination in HBr furnishes 4,7-dibromobenzothiadi-azole, which can be alkynylated or directly reduced [62]. Reduction of the dibromide with sodium borohydride leaves the halide substituents unmolested but opens the ring to furnish l,4-dibromo-2,3-diaminobenzene. Reaction of this intermediate with a 1,2-dione furnishes a 2,3-disubstituted 5,8-dibromo-quinoxaline. Pd-catalyzed alkynylation finishes the sequence off and removal of the TMS groups yields the desired 5,8-diethynylquinoxaline monomers (Table 9, entries 13,14). 

Bromination of the phenyl group in 5-(4-nitrophenyl)-2-phenyl-l,3,4-oxadiazole in the presence of potassium bromate yielded o- (16%), m- (14%), and /)-bromo (26%) products, together with low yields of dibromo products <84JCR(S)382>. Similar results were obtained on nitration of 2,5-diphenyl-1,3,4-oxadiazole with fuming nitric acid to give dinitro products. The ratio of o- w-.-/ -nitration... 

Propanone, 1,3-dibromo-l,3-diphenyl- (8,9) (958-79-2) Cyclopentadiene 1,3-Cyclopentadiene (8,9) (542-92-7) CH3CHBrCOCBr(CH3)2 3-Pentanone, 2,4-dibromo-2-methyl-... 

PENTAMETHYL-, 56, 1 Cyctopentane, acetyl-, 55, 25 Cyclopentane, 1-cyano-l-phenyl-, 55, 94 Cyclopentane, methyl, 55, 62 Cyclopentanol p-toluenesulfonate, 55, 112 Cyclopentene, 56, 34, 58, 73 2-Cyclopenten-l-one, 2,5-dialkyl- 58, 62 CYCLOPENTENONES, 58, 56 Cyclopropane, 1 -acetyl-1 -phenyl-, 55, 94 Cyclopropane, 1, l-dibromo-2,2-diphenyl-, 56, 32... 

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