2-Bromo-l,4-benzoquinone

Only the 2-Bromo-l,4-benzoquinone is known, orn-yel crysts(from petr eth), mp 56.5°, sublimes when carefully heated other props methods of prepn are given in the Refs... 

Bromo-l,4-benzoquinone-4-oxime [called 2-Brom -p-chinon-oxim-(4) or 2-Brom-4-nitroso-phenol in Ger], 0 CgH3(Br) N.OH or HO.C6H3(Br).NO-See 4-Nitroso-2-bromophenol under Bromophenol and Derivative s... 

Benzoquinone 2-Methyl-1,4-benzoquinone 2-Hydroxyl-l,4-benzoquinone 0.590 2-Bromo-l,4-benzoquinone 0.715 2-Chloro-l,4-benzoquinone 0.713... 

Chloro- and bromoaminopyridines are oxidized by persulfuric acid at 0° to their nitro derivatives thus, 3-chloro-, and 3-bromo-4-aminopyridine are converted to the respective 3-halo-4-nitropyridines. However, 4-araino-3-iodo-pyridine is not oxidized under these conditions. 4-Amino-2,3,5,6-tetrafluoro-pyridine is difficult to oxidize and requires refluxing peroxytrifiuoroacetic acid for 22 hours in order to yield the 4-nitro derivative. Potassium bromate has been used to oxidize S-amino-3-methyl-2-pyridone, but the product was not a nitro compound instead 3-hydroxy-6-methyl-2-aza-l,4-benzoquinone-4-(2,6-di-hydroxy-5-methyl-3-pyridyl)imine (IX-S7) was obtained. ... 

An alternative regioselective synthesis of 2-anilino-5-methyl-l,4-benzoquinone (842) was developed using 2-bromo-6-methyl-l,4-benzoquinone (846) (route A) and 4,4-dimethoxy-2-methylcyclohexa-2,5-dienone (849) (route B) as synthetic equivalents for methyl-1,4-benzoquinone (841) (623) (Scheme 5.102). 

In a synthetic application of this double inversion sequence, tris(benzyloxy)bromo boronic ester 6 obtained in the ribose sequence (Section 1.1.2.1.3.2.) is converted to the 4-methoxyphenyl-methoxy derivative 7 in the usual way. 2,3-Dichloro-5,6-dicyano-l,4-benzoquinone cleaves the protecting group to furnish the a-hydroxy boronic ester 8. Conversion of the a-hydroxy boronic ester 8 to the methanesulfonate 9 followed by displacement of the sulfonate by phenylmethoxide yields a-benzyloxy boronic ester 10, which is a diastereomer of one of the ribose intermediates37. 

Anthraquinonecarboxamide in its Sj state will photoadd two molecules of water. The photoreactions of diphenylhomobenzoquinones in the presence of amine donors have been studied. 1-Bromo substituted diphenylhomobenzoqui-none irradiated in the presence of triethylamine induces opening of the cyclopropane ring with formation of 2-diphenylmethyl-5-methyl-l,4-benzoquinone, and with dimethylaniline, a mixture of an aminated bicyclic dione and bis(p-dimethyl-aminophenyl)methane is produced. Irradiation of boron difluoride complexes derived from 1,3-diketones can lead to a number of different types of process, in particular exciplex formation and slow cycloaddition. Evidence has now been advanced to suggest that excitation of these complexes leads directly to an exciplex without the participation of an encounter complex, and that this solvolyses to free ions. 

Benzoquinone l,4-di(bromo imine), BrN C6H4 NBi mw 263 94, N 10.62% crysts, mp expl ca 86, was claimed to have been prepd by Krause(Ref 2) by treating an aq soln of p-phenylenediamine chloride with an excess of bromine water. No an-analysis of the compd was given Refs l)Beil- not found 2)A.Krause,Ber 12,50... 

SuccBr) in CC14 affords the 4-bromoderivative 5, whereas its 6-bromo isomer 6 is prepared through direct coupling of 4-bromo-l,8-diaminonaphthalene with 2,6-di-fcrt-butyl-1,4-bcn/oquinone. When three equivalents of A -bromosuccinimide were used in the reaction with la, the tribromo derivative 7 was prepared in good yield. Another way to 7 is the condensation of 2,4,7-tribromo-l,8-diaminonaphthalene with 2,6-di-tert-buty 1-1,4-benzoquinone, 8... 

H-l,4-Benzoxazine 6-Bromo-2,3-dimethoxycarbonyi-4-hydroxy-E9a, 145 (1,2-Benzoquinon-oxim/ Cu + ROOC — C = C — COOR)... 

Chlorohenzoquinone(c eA Chlorbenzochinon or Chlorchinon in Get), 0 CgHg(Cl) 0 mw 14 2.5 3. The 2-Chloro-, 3 Chloro-, and 4-Chloro isomers are described in the literature Ref Beil 7, 630, (338, 346) [579] Diazobromochlorobenzoquinone, C H BrClN O mw 233.44, N 12.00%. Two isomers are known l Diazo 4 bromo 6 chloro 0-benzoquinone [called 6-Chlor-4-brom-o-chinon-diazid-(l) or 3 Chlor-5 brom-2-diazo-phenol in Ger], crysts, mp 115-16°, dec at 118 was obtd by slow decompn of 2,6 -dichloro-4 -bromobenzenediazonium acetate (Refs 1 4) and... 

Anhydrous HCl rapidly bubbled through a soln. of 3-bromo-2,5-di-/ r/-butyl-1,4-benzoquinone in glacial acetic acid during 1 hr., and the intermediate quinol oxidized with N2O4 in chloroform -> 2-diloro-3-bromo-5-tert-butyl-l,4-benzo-quinone. Y 75%. F. e. s. H. W. Moore et al., J. Org. Chem. 57, 1984 (1972). 

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