Dibromo benzene

Terephthalic acid has been obtained from a great many /)-disubstituted derivatives of benzene or cyclohexane by oxidation with permanganate, chromic acid, or nitric acid. The following routes appear to have preparative value from />-toluic acid, />-methylacetophenone,2 or dihydro-/)-tolualdehyde by oxidation with permanganate from f>-cymene by oxidation with sodium dichromate and sulfuric acid from />-dibromobenzene or from /i-chloro- or -bromobenzoic acid by heating at 250° with potassium and cuprous cyanides and from />-dibromo-benzene, butyllithium, and carbon dioxide. ... 

HC— C(Br) CH mw 276.95, N 15.18% yel ndls (from acet, ale or benz), mp 62°, probably explodes when heated rapidly to higher temps v sol in eth sol in hot ale si sol in w prepd by introducing NH into 2,4-Dibromo-benzene-l-diazonium tetrachloroiodide in the cold ( Refs 1 2). The 2,4-Dicblorophenyl Azide explodes when heated rapidly or when sharply struck (See Vol 2 of Encycl, p B44-R) Refs 1) Beil 5, 278 [2091 2) F.D. 

Dinitro 4,6-dibromobenzene, mp 117° yel dimorph stable form, rhmb crysts, d 2.295 sol in common solvs and mecastable form, monoclinic prisms (from a cooled saturated in eth + a little ale or by seeding a saturated soln in eth acet) prepd by nitrating m-dibromobenzene or l-nitro-2,4-dibromo-benzene with mixed acid (Ref 5)... 

Adams platinum oxide catalyst is readily prepared from chloroplatinio acid or from ammonium chloroplatinate, and is employed for catalytio hydrogenation at pressures of one atmosphere to several atmospheres and from room temperature to about 90°. Reduction is usually carried out with rectified spirit or absolute alcohol as solvents. In some cases (e.g., the reduction of benzene, toluene, xylene, mesitylene, cymene and diphenyl ), the addition to the absolute alcohol solution of 2-5 per cent, of the volume of rectified spirit which has been saturated with hydrogen chloride increases the effectiveness of the catalyst under these conditions chlorobenzene, bromobenzene, o-, m- and p-bromotoluenes, p-dichloro- and p-dibromo-benzene are reduced completely but the halogens are simultaneously eliminated. Other solvents which are occasionally employed include glacial acetic acid, ethyl acetate, ethyl acetate with 17 per cent, acetic acid or 8 per cent, of alcohol. In the actual hydrogenation the platinum oxide Pt02,H20 is first reduced to an active form of finely-divided platinum, which is the real catalyst allowance must be made for the consumption of hydrogen in the process. 

Heiss, C. Marzi, E. Schlosser, M. Buttressing effects rerouting the deprotonation and functionalization of 1,3-dichloro- and 1,3-dibromo-benzene. Eur J. Org. Chem. 2003, 4625 -629. Murahashi, S.-I. Naota, T. Tanigawa, Y. Palla-dium-phosphine-complex-catalyzed reaction of organometallic compounds and alkenyl halides (Z)-/j-[2-( N,. -di rn ethyl ami no) pheriyl]-styrene. Org. Synth. 1990, Coll. Vol. VII, 172— 176. 

Uchida et al. [793] have described a method for determination of selenium in river and sea water by gas chromatography with electron-capture detection. The specific reaction of l,2-diamino-3,5-dibromo-benzene with selenium(IV) is used, the product (4,6-... 

Many dihalobenzenes afford disubstitution products when they react with PhS ions and little, if any, monosubstitution products are formed. For instance, ra-chloroiodo, />-chloroiodo, m- and / -dibromo benzenes gave the disubstitution products2823, whereas m-fluoroiodobenzene gave 96% of the monosubstitution product270. However, with other sulphanions, the ratio of mono- to disubstitution varies, depending on the nature of the nucleophile and the haloarenes279. Thus, the sulphanions 221-225 were studied in the photostimulated reaction with chloroiodobenzenes. 

The products predicted to result from the bromination of the ortho-, meta-, and paz-a-isomers of dibromo benzene are as follows ... 

Kanbara has since generated a family of poly(iminoarene)s by reaction of 1,3-dibromo-benzene, 4,4-dibromodiphenyl ether, 2,6- and 3,5-dibromopyridines, 2,4-dibromothiophene, and l,l -dibromoferrocene with a variety of bifunctional arylamines [229]. In many cases, no polymer was obtained, but for polymerizations involving dibromobenzene and 2,6-dibromopyridine, materials with JVfn values of over 10,000 were obtained. Spectral data were provided for poly(2,6-aminopyridine) and a polymer made from dibromobenzene and a dia-rylamino sulfone. These authors have also investigated nickel catalysts for the polymerization of diamines with dichloroarenes, but the materials generated had molecular weights below 10,000 in most cases [230]. 

The more recent synthesis for lasoxifene (74) takes a very different course. The first step comprises displacement of one of the halogens in 1,4-dibromo-benzene by the alkoxide from A -2-hydroxyethylpyrrolidine 75 in the presence of 18-crown ether to afford 76. Condensation of the lithium salt from 76 with 6-methoxytetralone (77) followed by dehydration of the initially formed carbinol yields intermediate 78, which incorporates the important basic ether. Reaction of this compound with pridinium bromide perbromide leads to displacement of the vinylic proton by halogen and formation of the bromide 79. Condensation of this product with phenylboronic acid in the presence of a palladium catalyst leads to coupling of the phenyl group by formal displacement of bromine. The product (79), is then taken on to 74 as above. 

The present procedure has also been used by the submitters to prepare the following thioethers l,4-bis-( -butylthio)benzene, pale yellow oil, b.p. 142°/0.S mm., Mq 1.5726, from -dibromo-benzene and cuprous -butylmercaptide (yield 68-74%) 1,2-bis(phenylthio)benzene, white ciystals, m.p. 42.5-44.5°, b.p. 190°/1 mm., from o-dibromobenzene and cuprous phenylmer-captide (see below) (yield 79-83%), or from i>-dichlorobenzene (see below) and cuprous phenylmercaptide (yield 58-71%) l,4-bis(phenylthio)benzene, white crystals, m.p. 82-83°, from / -dibromobenzene and cuprous phenylmercaptide (yield 80-84%), or from -dichlorobenzene (see below) and cuprous phenylmercaptide (yield 59-72%). The same method can be applied to the preparation of many other thioethers. 

The spectra of the intermediate transients formed in the reaction of OH with dichloro- and dibromo-benzenes and chloro- and bromo-toluenes exhibited absorption maxima around 325-330 nm with both ortho- and w to-isomers of dichlorobenzenes, dibromobenzenes, and bromotoluenes (Fig. 6). The transients were assigned to the isomeric OH adducts formed from the addition of OH to the benzene ring. A blue shift was observed in the absorption maximum of -bromotoluene (315 nm) when compared to its ortho- and meta-isomers which have maxima at 330 nm. Such a behavior was also seen in the absorption spectra of OH adducts of 0- and w-chlorotoluenes (325-330 nm) and w-xylenes (326-328 nm) as compared to their... 

DinitTO 2,3 dibromobenzene, ndls (from CS2, glac acet ac or ale), mp 119-20° obtd with, other isomers by nitrating p-dibromo-benzene with mixed acid (Ref 2)... 

NOTE No higher nitrated derivs of Dibromo-benzene were found in Beil or in CA thru 1961... 

Problem 10.8 You have three bottles containing the three isomeric dibromo-benzenes they have the melting points + 87 ", + 6", and - T By a great deal of work, >... 

Reactions of this type have been used in the synthesis of indoles on a solid phase [143, 144]. Yamazaki et al. described a combination of palladium-catalyzed amination and Heck reaction in a synthesis of indole [145]. One indole synthesis is performed by a Heck reaction of N-acyl dehydroalanine immobilized on REM resin (24) -with 1-2 halobenzenes (26). In the case of 2-N-acyl-aminocinnamoyl esters, the N-acetyl groups gave higher yields than CBz-groups and 1,2-dibromo-benzene (78%) was more efficient than l-bromo-2-triflyloxybenzene (41%) (Scheme 3). 

B is( -butylthio)benzene and 1,4-bis( -butylthio)benzene have been prepared from the corresponding dibromobenzene and cuprous w-butylmercaptide, using a mixture of quinoline and pyridine as solvent.6, l,2-Bis(phenylthio)benzene and 1,4-bis(phenylthio)benzenehave been prepared from the corresponding dichloro- or dibromobenzenes and cuprous phenylmercaptide, using a mixture of quinoline and pyridine as solvent.5 1,4-Bis(phenylthio)benzene has also been prepared from -dibromo-benzene or -bromophenyl phenyl sulfide and lead phenylmercaptide 7 and from diazotized 4-aminophenyl phenyl sulfide and sodium phenylmercaptide.8... 

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