Benzoquinone acetic acid

Benzoquinone Acetic acid/acetate buffer (pH 5.4) 50 per cent MeOH + 0.15... 

Excess substrate inhibited the oxidation of the p-hydroxyphenyl-pyruvate as did also benzoquinone acetic acid. This could be prevented by adding large amounts of ascorbic acid or small amounts of reduced 2,6-dichlorophenolindophenol. The latter was seven hundred times as effective as ascorbic acid with the purified enzyme 214), Zannoni and LaDu speculate that a product formed from p-hydroxyphenylpyruvate is the true inhibiting agent of the reaction. 

Pungent odour. Formic acid, acetic acid, acetyl chloride, acetic anhydride, benzoyl chloride, benzyl chloride, pyridine. Benzoquinone (when warmed with water). 

Dimethoxy-l,4-benzoquinone [530-55-2] M 168.1, m 256 . Crystd from acetic acid. Sublimes in a vacuum. 

Various 2,6-di8ubstituted p-benzoquinones have been prepared by oxidation of the corresponding 2,6-disubstituted phenols with potassium nitrosodisulfonate or lead dioxide in formic acid. Oxidative coupling of 2,6-disubstituted phenols to poly-2,6-disubstituted phenylene ethers followed by treatment of the polymers in acetic acid with lead dioxide is reported to give low yields of the corresponding 2,6-disubstituted p-benzoquinones. 

The Nenitzescu process is presumed to involve an internal oxidation-reduction sequence. Since electron transfer processes, characterized by deep burgundy colored reaction mixtures, may be an important mechanistic aspect, the outcome should be sensitive to the reaction medium. Many solvents have been employed in the Nenitzescu reaction including acetone, methanol, ethanol, benzene, methylene chloride, chloroform, and ethylene chloride however, acetic acid and nitromethane are the most effective solvents for the process. The utility of acetic acid is likely the result of its ability to isomerize the olefinic intermediate (9) to the isomeric (10) capable of providing 5-hydroxyindole derivatives. The reaction of benzoquinone 4 with ethyl 3-aminocinnamate 35 illustrates this effect. ... 

The next major obstacle is the successful deprotection of the fully protected palytoxin carboxylic acid. With 42 protected functional groups and eight different protecting devices, this task is by no means trivial. After much experimentation, the following sequence and conditions proved successful in liberating palytoxin carboxylic acid 32 from its progenitor 31 (see Scheme 10) (a) treatment with excess 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) in ie/t-butanol/methylene chloride/phosphate buffer pH 7.0 (1 8 1) under sonication conditions, followed by peracetylation (for convenience of isolation) (b) exposure to perchloric acid in aqueous tetrahydrofuran for eight days (c) reaction with dilute lithium hydroxide in H20-MeOH-THF (1 2 8) (d) treatment with tetra-n-butylammonium fluoride (TBAF) in tetrahydrofuran first, and then in THF-DMF and (e) exposure to dilute acetic acid in water (1 350) at 22 °C. The overall yield for the deprotection sequence (31 —>32) is ca. 35 %. 

In a 250-ml., three-necked flask fitted with a mechanical stirrer, a thermometer, and a 25-ml., graduated, pressure-equalizing dropping funnel are placed 7.60 g. (0.050 mole) of phenoxyacetic acid [Acetic acid, phenoxy-] (Note 1), 5.40 g. (0.050 mole) of 1,4-benzoquinone [2,5-Cyclohexadiene-l,4-dioneJ (Note 2), 1 g. (0.006 mole) of silver nitrate [Nitric acid silver(l +) salt] (Note 3), and 125 ml. of water (Note 4). The mixture is then stirred and heated to 60-65° by means of a heating mantle until dissolution is complete. The resulting solution is stirred... 

Rizk et al. [3] used 2,3-dichloro-5,6-dcyano-/)-benzoquinone as a redox titrant in the aqueous titration of penicillamine. Finely ground tablets were mixed with H20 and the mixture was filtered. The filtrate (or an injectable solution) was diluted with H20 and acidified with H3PO4 before titration with the redox titrant. The titration was conducted in anhydrous acetic acid using thiethylperazine dihydrochloride as the indicator. The endpoint was detected by a color change to green, and recoveries of penicillamine were 98.4-100.5%. 

The use of a nitrogen nucleophile in the side chain (as an amide) also leads to an intramolecular 1,4-addition under the standard conditions for the palladium-catalyzed 1,4-oxidation reactions52. Nitrogen nucleophiles employed for this reaction comprise tosy-lamides, carboxamides, carbamates and ureas. The reactions are run in acetone-acetic acid with p-benzoquinone (BQ) as the oxidant. In most cases highly stereo- and regioselective reactions were obtained and some examples are given in Table 3. 

In a stoichiometric reaction the 6jr-allyl)palladium complex 66 was isolated and characterized5815. In a subsequent reaction the jr-allyl complex was reacted with benzoquinone in acetic acid to give an allylic acetate, which was hydrolyzed and oxidized to theaspirone. Interestingly, a quite high diastereoselectivity for the turns methyl isomer was obtained in the palladium-mediated spirocyclization (equation 28). 

The only case of this type reported in the literature concerns the preparation of the substituted hydroxy-thiazolo [3,2 -a -benzimidazole 408 from 2-aminothiazole 407 and 1,4-benzoquinone in glacial acetic acid (Equation 185)... 

An excess of tetrachloro-p-benzoquinone (chloranil) in o-dichlorobenzene is added to 2 moles of 3-amino-N-ethylcarbazol and dry sodium acetate, which acts as an acid trap. The mixture is stirred for 6 hours at 60°C, then within 5 hours heated to 115°C under vacuum, after which benzenesulfochloride is added at the same temperature. Cyclization is achieved by increasing the temperature to 175-180°C. The reaction mixture is agitated until no more acetic acid appears in the distillation receiver (for 4 to 8 hours). The reaction product is vacuum filtered, residual o-dichlorobenzene removed by steam distillation, the product washed, and dried. A patent which was issued in 1980 claims a much improved yield if the reaction is performed in the presence of only a slight excess of chloranil, provided 0.15 to 1.8 wt% water is added to the reaction mixture [5],... 

Stereo- and regioselective palladium-catalyzed oxidation of 1,3-dienes in acetic acid to give l,4-diacetoxy-2-alkenes has been accomplished using Mn02 and catalytic amounts of p-benzoquinone (BQ)11. The reaction can be made to take place with cis- or trans-1,4-diacetoxylation across the diene in cyclic systems as shown in equation 6. 

Using a similar approach, l-acetoxy-4-diethylamino-2-butene and l-acetoxy-4-benzylamino-2-butene were prepared. Treatment of 1,3-butadiene with LiCl-LiOAc in the presence of Pd(OAc)2 and p-benzoquinone in acetic acid gave 91% l-acetoxy-4-chloro-2-butene (E/Z = 90/10). Subsequent allylic amination with diethylamine, catalyzed by Pd(PPh3)4 in THF, produced mainly ( )-l-acetoxy-4-diethylamino-2-butene13. 

Addition of 7-amino-2,2-dimethylchromene 107 to 2-methyl-1,4-benzoquinone 108 in acetic acid/water leads to the 2-arylamino-5-methyl-1,4-benzoquinone 109 in moderate yield (Scheme 34). Oxidative cyclization of compound 109 using a stoichiometric amount of palladium(II) acetate in acetic acid under reflux provides pyrayaquinone A 110 [42,132]. 

To 5.7 g (0.0527 mol) of p-benzoquinone is added 10 g (approximately 0.072 mol) of tin amalgam and 50 ml of glacial acetic acid. The mixture is heated on a steam bath. After 3 minutes green crystals of quinhydrone precipitate but soon dissolve to give a Ught yellow solution. After 0.5 hour the solution is filtered, the solvent is removed in vacuo, and the residue is recrystallized from benzene-acetone to give 5.0g (88%) of hydroquinone, m.p. 169-190°. 

Palladium acetate (1.12 g, 0.005 mol), benzoquinone (2.16 g, 0.02 mol), manganese dioxide (10.44 g, 0.12 mol) and anhydrous acetic acid (250 iriL) (Note 1), are placed in a 1-L, round-bottomed flask equipped with a reflux condenser and magnetic stirring bar. This heterogeneous mixture is equilibrated by efficient stirring for 30-60 min. Cycloheptene (9.61 g, 0.1 mol) (Note 2) is added, and the stirring is continued at 60°C for 28 hr (Note 3). After the solution is cooled to room temperature, 250 mL of pentane/ether (1 1) is added and the mixture is stirred for another 30 min. The two-phase mixture is... 

For the first time, application of sequential Diels-Alder reactions to an in situ-generated 2,3-dimethylenepyrrole was shown with various dienophiles 548 to afford 2,3,6,7-tetrasubstituted carbazoles (549). This novel tandem Diels-Alder reaction leads to carbazole derivatives in two steps, starting from pyrrole 547 and 2 equivalents of a dienophile, and is followed by 2,3-dichloro-5,6-dicyano-l,4-benzoquinone (DDQ) oxidation of the intermediate octahydrocarbazole. Mechanistically, the formation of the intermediate octahydrocarbazole appears to involve two sequential [4+2] cycloadditions between the exocyclic diene generated by the thermal elimination of acetic acid and a dienophile (529) (Scheme 5.17). 

Condensation of the aminochromenes 1039 and 1041 with 2-methyl-l,4-benzoquinone (841) afforded 2-(2,2-dimethyl-2H-chromen-7-ylamino)- (1042) and 2-(2,2-dimethyl-2H-chromen-5-ylamino)-5-methyl-l,4-benzoquinone (1043), along with the corresponding 6-methyl isomers. Finally, reaction of the benzoquinones 1042 and 1043 with stoichiometric amounts of palladium(II) acetate in acetic acid under reflux furnished pyrayaquinone A (175) and B (176) in 78% and 50% yield, respectively (623) (Schemes 5.157 and 5.158). 

Methoxy-6-propyl-l,4-benzoquinone (170, Scheme 43) with hydrogen chloride undergoes dimerization and yields the biquinone 171 and the di-benzofuran 172. 2-Hydroxy-3,6-dimethyl-1,4-benzoquinone (173, Scheme 44), however, on treatment with boron trifluoride etherate in ether, or with concentrated sulfuric acid in acetic acid at room temperature, yields the extended quinone 174, which on reductive acetylation affords the dibenzo-furan 175. 

Dibenzofuran is highly stable to oxidizing agents. 2-Dibenzofuranol is oxidized to 2-(2-hydroxyphenyl)-l,4-benzoquinone by sodium periodate in aqueous acetic acid, whereas reaction of 1-dibenzofuranol or 4-dibenzo-furanols with Fremy s salt produces the dibenzofuran-l,4-quinones. The oxidation of dibenzofuran with microorganisms has been studied. A mutant strain of a Beijerinckia bacterium oxidizes dibenzofuran to a mixture of cis-2,3-dihydroxy-2,3-dihydrodibenzofuran and cis-l,2-dihy-droxy-l,2-dihydrodibenzofuran. The former compound was found to be too... 

Under suitable conditions, further oxidation of the coupled products produces isolable dimer cation radicals. Thus treatment of 9-alkylcarbazoles with lead tetracetate in acetic acid-perchloric acid, or with 2,3-dichloro-5,6-dicyano-p-benzoquinone in acetic acid-perchloric acid, or with tris-(p-bromophenyl)ammoniumyl perchlorate in methylene chloride, or with nitrosonium borofluoride in acetonitrile all gave isolable cation radical perchlorates such as 17. These were reducible with aqueous sodium dithi-onite to the corresponding bicarbazoles the dimer cation radicals could be produced again by reoxidation of the dimer using 2,3-dichloro-5,6-dicyano-p-benzoquinone in acid solution. ... 

Trinitro-3-hydroxy-azobenzene, H0.C6H2(N02)2N N.C6H4.N02 red ndls (from acet ac + w), mp 179° was prepd by heating benzoquinone-( 1,4)-oxime-4,6-dinitro-3-hy droxy-phenylhydrazone with nitric acid (d 1.39) acetic acid (Refs 1 3). No expl props are reported... 

Preparation of 2,5-diazido-l,4-benzoquinone from sodium azide, acetic acid, and 1,4-benzoquinone [65]. 

Poly(cthylcne-co-carbon monoxide) was also prepared by Kwon et al. (1) using acetic acid and water as the reaction solvent. It was also prepared by Taniguchi et al. (2) using 1,3-bis [bis(2-methoxy-5-phenyl)phosphino]-propane, (II), with palladium acetate and 1,4-benzoquinone. 

Several Pd-catalyzed oxidations with different reoxidants have been developed. In these reactions PdCl2 or Pd(OAc)2 in acetic acid is usually employed, with tert-BuOOH and Te02,699 or p-benzoquinone and MnO2 70°... 

---