otto (Hive Bee)
04-07-02 09:34
No 293714
      quinones as starting material II  Bookmark   

dear bees,

has somebody access to Zh. obsch. chim.? actually otto is looking for an article about halogenation of benzoquinone.
in Zh. obsch. chim. 30, 1960, p. 2316 they react benzoquinone with bromine in conc. HBr to yield 2,5-dibromo-1,4-hydroquinone, the same in conc. HCl yields 2-bromo-5-chloro-1,4-hydroquinone.
these two molecules can serve as excellent precursors to the 2-CX-family.

otto
 
 
 
 
    hest
(Hive Bee)
04-07-02 09:42
No 293716
      It's an easy synth. Disolve your quinone into ...  Bookmark   

It's an easy synth. Disolve your quinone into AcOH, then add 2mole Br2 to the solution (slow).
Let it stir for some houers, ad alot of wather, ekstract tree times with some nonpolar, combine the nonpolar, wash 8-10 times with pure wather, then ekstract 2-3 with 2M NaOH(aq), combine the NaOH(aq), and make it acid, you can now filter off your dibromohydroquinon.
 
 
 
 
    foxy2
(Distinctive Doe)
04-07-02 22:50
No 294074
      benzoquinones to hydroquinones
(Rated as: excellent)
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These papers have details on converting Br substituted benzoquinones to hydroquinones with Sodium dithionite (Na2S2O4).


Synthesis of 2,5-Disubstituted 3,6-Diamino-1,4-benzoquinones
Louis S. Hegedus, Roy R. Odle, Peter M. Winton, and Paul R. Weider
J. Org. Chem., 47, 2607-2613 (1982)

Abstract
A general synthetic approach to a wide variety of 2,5-disubstituted 3,6-diamino-l,4-benzoquinones was developed. Bromanil was diaminated with ammonia, and adjacent NH2 and OH groups were protected as benzoxazoles by treatment with a carboxylic acid chloride followed by a polyphosphate ester cyclization-dehydration. The resulting 2,5-dibromobenzobis(oxazoles) were monolithiated by halogen-metal exchange with n-butyllithium and then reacted with a variety of electrophiles. The remaining bromide was replaced in a similar fashion. Alternatively the second bromide was replaced by reaction with H allylnickel halide complexes. The benzoxazole protecting group could be hydrolyzed with zinc(II) chloride/HCl-aqueous ethanol under an inert atmostphere. Air oxidation of the resulting hydroquinone under neutral conditions gave the desired 2,5-disubstituted 3,6-diamino-1,4-benzoquinone in good to excellent overall yield. This method was used to synthesize precursors to the basic ring system of the mitomycin antineoplastic antibiotics. Acid hydrolysis of the benzoxazole protecting group under oxidizing conditions resulted in the production of 2,5-disubstituted 3,6-dihydroxy-1,4-benzoquinone. Methylation followed by reaction with ammonia gave the desired diaminoquinone.


Experimental
Preparation of 2,5-Diamino-3,6-dibromohydroquinone (1)
2,5-Diamino-3,6-dibromoquinone (2 g, 6.76 mmol) was mixed with Na2S2O4 (2.8 g, 16.1 mmol) in 60 mL of H2O and warmed under nitrogen until the red color of the starting material had disappeared. The mixture was fiitered, and the off-white crystals were washed with H2O and ethanol and air dried to give 1.81 g (90%) of the desired product. This material could be used without further purification.




J. Org. Chem., 50(22), 4282-8 (1985)



Here is another paper, although its probably less relevant due to the reagents used.


Reactions of some 5,6-dihalo-2-cyclohexene-1,4-diones (1,4-benzoquinone dihalides) in boron trifluoride diethyl etherate.    
Norris, R. K.; Sternhell, S., Aust. J. Chem., 26(2), 333-43 (1973)

Abstract
Treatment of five 1,4-benzoquinone dihalides in BF3.Et2O gives isomeric dihalohydroquinones.  With the exception of the conversion of 5,6-dichloro-2-cyclohexene-1,4-dione into 2,3-dichlorohydroquinone, which is a true keto-enol isomerization, these products arise through elimination of hydrogen halides followed by readdn.


 
 
 
 
    foxy2
(Distinctive Doe)
04-07-02 23:54
No 294110
      2,5-dibromo-1,4-hydroquinone synthesis
(Rated as: excellent)
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Low-oxidation-potential conducting polymers: alternating substituted para-phenylene and 3,4-ethylenedioxythiophene repeat units.    
Irvin, Jennifer A.; Reynolds, John R.
Polymer  (1998),  39(11),  2339-2347.

Relevant Procedures:

2,5-dibromo-1,4-hydroquinone synthesis
Hydroquinone (0.968 mol) was combined with glacial acetic acid (500ml) and methylene chloride.  A solution of Bromine (1.88 mol) in methylene chloride (100ml) was added dropwise over 2 hours at room temperature.  After approx. half the bromine was added, all solids had dissolved.  The solution was stirred at room temperature for 15 hours at which time the precipitate was collected by filtration and dried under vacuum over NaOH pellets.  Recrystallization from isopropanol yeilded a white crystalline solid (m.p. 191-192C, 42% yeild)

1,4-dibromo-2,5-dimethoxybenzene synthesis
A solution of KOH (0.077 mol) in ethanol (100ml) was added slowly to a solution of 2,5-dibromo-1,4-hydroquinone (0.035 mol) in THF (200ml) under argon.  The solution was stirred at room temperature for 3 hours, and then a solution of iodomethane (0.077mol) in THF (100ml) was added slowly with stirring.  The mixture was stirred at 50C for 24 hours, then precipitated into water.  The product was collected by filtration and recrystallized from ethanol to give a white crystalline solid (m.p. 144-147C, (lit. m.p. 142-143C), 86% yeild)


Internal rotation about aromatic carbon-oxygen bond.  I.  Preparation of sterically overcrowded polysubstituted phenol derivatives.    
Boehm, Jaroslaw; Zamlynski, Waclaw.
Rocz. Chem.  (1967),  41(4),  707-16. (In Polish)   
CAN 67:53816    AN 1967:453816 
Abstract
Tosyl and Me ethers of tri- and tetra substituted m-hydroxybenzoic acid, resorcinol, and hydroquinone derivs. did not appear in stereoisomeric forms which proved that the rotation of RO groups was not restricted.  The ir spectra of tosylates confirmed the linear relation of the sym. and unsym. stretching frequencies of SO2 vibrations.  Two polymorphic forms of 2,4,6-tribromo-3-methoxybenzoic acid (I) were isolated.  Thus, a soln. of 14 g. m-hydroxybenzoic acid in 550 ml. H2O and 35 ml. 48% HBr in 65 ml. 30% H2O2 kept 12 hrs. afforded 16.48 g., in the first crop, of 2,4,6-tribromo-3-hydroxybenzoic acid (II), m. 147-8.  The filtrate treated with 5 ml. HBr and 10 ml. H2O, gave in the second crop 16.86 g. II.  A soln. of 10 g. resorcinol and MeONa in MeOH (prepd. from 12 g. metallic Na in 150 ml. MeOH) was autoclaved during 10 hrs. at 190/70 atm., then acidified and steam distd. to give in the residue 7.5 g. crude product (recrystd. from C6H6), which when chromatographed on Al2O3 and eluted with: C6H6-ligroine, yielded 70% 2,4,6-trimethylresorcinol, m. 151-2.  A boiling suspension of 27.5 g. hydroquinone in 300 ml. CCl4 was treated dropwise, during 3 hrs., with 160 g. Br in 150 ml. CCl4, then refluxed 10 hrs., cooled, washed with Na2SO3, and evapd. to give 85.5 g. of a crystn. ppt.  The pptd. extd. with hot water afforded 22 g. 2,5-dibromohydroquinone, m. 186-7.  The water insol. residue recrystd. successively from AcOH, EtOH, and EtOH-Et2O consisted of a mixt., m. 247-57, of tetrabromohydroquinone and tetrabromoquinone.  Redn. of 8.5 g. of the mixt. in 250 ml. 80% AcOH, under reflux, with 10 g. Na2S2O4 in 100 ml. H2O gave quant. tetrabromohydroquinone, m. 244-6.  Redn. of the appropriate quinone with Na2S2O4 in 80% AcOH afforded 91% duroquinone, m. 234-5, and 96% tetrachlorohydroquinone, m. 232-4.  Tosylation was carried out either in aq. KOH or in pyridine.  A soln. of 7.4 g. II and 2.24 g. KOH in 100 ml. H2O stirred 12 hrs. with 3.8 g. p-MeC6H4SO2Cl (III) in 50 ml. C6H6, after sepn. of the aq.
layer and work up, afforded 3.84 g. II tosylate, m. 189-91.  Similarly, resorcinol yielded 92% di-tosyl deriv., m. 82-3.  A soln. of 3.91 g. 2,4,6-tribromo-3,5-dihydroxybenzoic acid (IV) in 100 ml. 3.5% aq. KOH was stirred during 20 hrs. with 5.7 g. III in 30 ml. C6H6.  When acidified the aq. layer afforded a resin, which when washed with CHCl3 gave 1.63 g. of the starting material.  When recrystd. from dil. EtOH, the CHCl3-insol. solid afforded 2.74 g. IV mono-tosylate, m. 207-9.  A general procedure for tosylation in pyridine at the molar ratio 1:3 phenol-III was given.  A soln. of 0.01 mole corresponding phenol in 20 ml. anhyd. pyridine was treated dropwise at room temp. with 0.03 mole III in 20 ml. pyridine, the mixt. was kept 30 min. at 60 and poured into water to give the following tosylates (Ts = tosyl) (compd., m.p., and % yield given): 1,3-(OTs)2-2,4,6-Br3C6H, 224-7, 94; 1-(OH)-3-(OTs)-2,4,6-Br3C6H, 163-7, 31.6; 1,3-(OTs)2-2,4,6-Me3C6H, 134-6, 88; 1-(OH)-3-(OTs)-2,4,6-Me3C6H, 88-9, 10; 1,3-(OTs)2-2,4,6-I3C6H, 263-5, 95; 1,4-(OTs)2-2,3,5,6-Br4C6, 272-3, 88; 1,4-(OTs)2-2,3,5,6-Me4C6, 274-5, 72.  Etherification of II with CH2N2 gave I (Ia), m. 65-7 (cyclohexane).  Another polymorphic form of I (Ib), m. 153-5, was prepd. either by alk. hydrolysis of I Me ester or methylation of II with Me2SO4.  When seeded with Ib the lower m. polymorph Ia gave Ib.  The reverse transformation failed.  Two cryst. alkaloid salts of Ib were reported: Ib brucine salt, m. 168-70, [a]205800 -25.23 (c 0.48, CHCl3); Ib quinidine salt, m. 215-16, [a]20580 124.6 (c 0.634, CHCl3).  In all cases the fractional crystn. and column chromatog. showed the presence of only one deriv., and thus the lack of stereosiomerism.


Bromination of phenols by use of benzyltrimethylammonium tribromide.    
Chem. Lett.  (1987),   (4),  627-30.
Abstract
The reaction of phenols with benzyltrimethylammonium tribromide in CH2Cl2-MeOH for 1 h at room temp. gave polybromophenols in good yields.


Reaction of thionyl bromide with dihydric phenols.
Saraf, S. D.; Malik, Z. A.; Bhatti, Z.
Pak. J. Sci. Ind. Res.  (1972),  15(3),  160-1. (In English)   
Abstract
Pyrocatechol reacted with SOBr2 to give the 4,5-dibromo deriv.; hydroquinone with SOBr2 gave the 2,5-dibromo deriv.  Resorcinol gave a high m.p. solid which was not identified.  A possible reaction mechanism was described.


We need some Chinese Bee's!!!
Wonder if this works for HBr + HNO3???

Improvement of methods for synthesis of dihalogeno-1,4-benzoquinones.    
Guan, Xiaopei; Sun, Li; Yan, Hong; Su, Zhuang.      
Beijing Gongye Daxue Xuebao  (1997),  23(1),  35-38.
ISSN: 0254-0037.(In Chinese)  CAN 128:34554  AN 1998:10205   
Abstract
The method for synthesis of 2-bromo-, 2,5-dibromo-1,4-hydroquinone, 2,5-dibromo-, 2,5-dichloro-, 2,3-dichloro-1,4-benzoquinones was improved.  E.g., 2,5-dichloroquinone was prepd. in 51.7% yield by treating quinone with HCl and HNO3.
 
 
 
 
    foxy2
(Distinctive Doe)
04-09-02 16:44
No 294772
      Benzoquinone to 2,5-dibromo-1,4-hydroquinone
(Rated as: excellent)
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Poly(2,5-dialkoxy-p-phenylene)s - synthesis and properties
Macromol. Chem. Phys. 195, 1933-1952 (1994)
Thomas Vahlenkamp, Gerhard Wegner

Relevant Procedures:

2,5-dibromo-1,4-hydroquinone synthesis
54.0 g p-benzoquinone (0.5 mol) are dissolved in 700mL hydrobromic acid.  80 g bromine (0.5 mol) are slowly added with stirring.  After 5 hours the reaction mixture is heated to 100C and stirred for another 10 hours.  After cooling to room temperature the precipitate is filtered off and washed with water.  Recrystallization is done from boiling water (3-5 L) with addition of charcoal. Yeild 72.7 g (54%); m.p. 184C.

2,5-dibromo-1,4-dialkoxybenzene synthesis
2,5-dibromo-1,4-hydroquinone is dissolved in a solution of KOH in ethanol (1.5-2 molar equivalents KOH per phenolic hydroxy group) and heated to reflux.  The alkyl bromide(it will work with alkyl iodides) is now added under reflux (at least 1.5 equivalents in excess).  After 10 hours the mixture is cooled and the precipitate formed is filtered off and washed with methanol.  The product is dissolved in chloroform, filtered and precipitated again by adding slowly methanol.  A clean product is obtained in most cases.  Recrystallization may be done from ethanol.  Yeild is typically 80%.
2,5-dibromo-1,4-dibutoxybenzene; m.p. 66C


Water-Soluable Rigid-Rod Polyelectrolytes: A new self-doped, electroactive sulfonatoalkoxy-substituted poly(p-phenylene)
Macromolecules 27, 1975-1977 (1994)
Andrew D. Child and John R. Reynolds

2,5-dibromo-1,4-dimethoxybenzene from 1,4-dimethoxybenzene
A soution of bromine (50.0 ml. 0.094 mol, in CCl4) was added slowly with stirring to a solution of 1,4-dimethoxybenzene (7.07 g, 0.051 mol) in 100 ml CCl4.  The mixture was allowed to stir for 20 hours at room temperature, quenched with aqueaous KOH, and washed with water, and the solvent was removed. The 2,5-dibromo-1,4-dimethoxybenzene obtained was recrystallized from ethanol and dried under vacuum. (No yeild given)
 
 
 
 
    cilliersb
(Hive Bee)
04-11-02 02:44
No 295438
      2,5-diBr-1,4-DiMeO-Benzene To 4-Br-1,4-DiMeO-P2P  Bookmark   

The Product 2,5-dibromo-1,4-dimethoxybenzene can be subjected to Potassium tert-butoxide / Acetone (Acetone Enolate) in DMSO to afford the P2P of DOB.

Because of the p configuration of the Methoxies and halogens the sole product should be the one in question. I'm guessing that using a stoichiometric amount of Acetone enolate, this synth can be quite high yielding, provided there isn't much steric hinderance from the methoxy groups.





 
 
 
 
    Hellowin
(Stranger)
04-15-02 04:34
No 297161
      next  Bookmark   

The Product can be subjected to Potassium tert-butoxide / Acetone (Acetone Enolate) in DMSO to afford the P2P of DOB.
The description of process ?
please !

 
 
 
 
    Rhodium
(Chief Bee)
04-15-02 08:05
No 297185
      Acetone enolate P2P route  Bookmark   

../rhodium/chemistry /p2p.enolate.html
 
 
 
 
    halfapint
(Ubiquitous Precursor Medal Winner)
05-07-02 09:14
No 305807
      Back to the top post  Bookmark   

"benzoquinone with bromine in conc. HBr to yield 2,5-dibromo-1,4-hydroquinone, the same in conc. HCl yields 2-bromo-5-chloro-1,4-hydroquinone" from otto's title post. For synthetic ease, the mismatched halides are handy, so use the HCl. The ring bromine's a lot more labile than the ring chlorine, e.g. you could make the ringomagnesium bromide without concern for the ring chloride, which wouldn't form the Grignard under mild conditions. Yet a 4-chloro-2,5-dimethoxy phenethylamine (or isopropylamine) would bee physiologically active, in the psychedelic sense. As well as making the Grignard, the inactivity of the ring chlorine could bee exploited in the good reverend's acetone enolate synth, no doubt, to alleviate the possibility of dialkylation.

a half a pints a half a pound a half a world a half a round
Sidearm n. Flask neck tube.