2.6- Dimethyl-l,4-benzoquinone

II. USE OF DIPOTASSIUM NITROSODISULFONATE (FREMY S SALT) 4,5-DIMETHYL-l,2-BENZOQUINONE... 

The reaction mixture from acidified dihydroxyacetone also included a series of seven di- and tri-hydroxybenzenes (see Scheme 4), namely, 2,3-dihydroxytoluene (16), pyrocatechol (17), 3,4-dihydroxy toluene (19), 3,5-dimethyl-l,2-benzenediol (20), 1,2,3-trihydroxybenzene (pyrogallol) (21), 1,2,4-trihydroxy benzene (22), 3,4,5,6-tetrahydroxy-2-methy 1-acetophe-none, and 2,3-dihydroxy-5,6-dimethyl-p-benzoquinone. Many of these same phenolic compounds are present after hexoses are similarly treated... 

Several products were also detected in base-degraded D-fructose solution acetoin (3-hydroxy-2-butanone 62), l-hydroxy-2-butanone, and 4-hydroxy-2-butanone. Three benzoquinones were found in the product mixture after sucrose had been heated at 110° in 5% NaOH these were 2-methylbenzoquinone, 2,3,5-trimethylbenzoquinone, and 2,5-dimethyl-benzoquinone (2,5-dimethyl-2,5-cyclohexadiene-l,4-dione 61). Compound 62 is of considerable interest, as 62 and butanedione (biacetyl 60) are involved in the formation of 61 and 2,5-dimethyl-l,4-benzenediol (63) by a reduction-oxidation pathway. This mechanism, shown in Scheme 10, will be discussed in a following section, as it has been proposed from results obtained from cellulose. 

DBPO DBU DCC DDQ DEAD DET DIBAL-H DIPT DMAP DMB DME DMF DMPU DMSO EDDA Eu(dppm)3 Eu(fod)3 dibenzoyl peroxide 1.8- diazabicyclo [ 5.4.0] undec-7-ene dicyclohexylcarbodiimide 2.3- dichloro-5,6-dicyano-l,4-benzoquinone diethyl azodicarboxylate diethyl tartrate diisobutylaluminium hydride diisopropyl tartrate iMM-dimethylaminopyridine 3.4- dimethoxybenzyl 1.2- dimethoxyethane dimethylformamide 1.3- dimethyl-3,4,5,6-tetrahydro-2(lH)pyrimidinone dimethyl sulfoxide ethylene diammonium diacetate di(perfluoro-2-propoxypropionyl)methanato europium 6.6.7.7.8.8.8- heptafluoro-2,2-dimethyl-3,5-octanedionato... 

A mixture of 4-triphenylmethyl-l,2-benzoquinone, dimethyl phosphite, and dry benzene refluxed 2 hrs. dimethyl (5,6-dihydroxy- ,-a, -triphenyl-m-tolyl)phos-phonate. Y 90%. F. e., also reaction at oxygen with trialkyl phosphites, s. M. M. Sidky and F. H. Osman, Tetrahedron 29, 1725 (1973). 

C H5)2C0H + 2,5-dimethyl-l,4-benzoquinone------ (2,5-dimethyl-...semiquinone) -I- (C6Hs)2CO... 

Photochemical reaction of 2-alkenoyl-3,5-dimethyl-l,5-benzoquinones with alcohol, Chem. Lett., 1343-1346, 1984 (d) Maruyama, K., Muraoka, M., and Naruta, Y., Photo-oxygenation of 2-aIkenoyl-l,4-quinones by atmospheric oxygen. Formation of stable cyclic peroxides, J. Chem. Soc., Chem. Comm., 1282-1284, 1980 (e) Miyagi, Y., Maruyama, K., and Yoshimoto, S., The chemical conversion of the photo-dimer of 2-acetyl-5-methyl-l,4-benzoquinone. The determination of the regiochemistry of the dimer. Bull. Chem. Soc. Jpn., 53, 2962-2965, 1980 (f) Maruyama, K. and Narita, N., Photochemical dimerization of 2-acyl-1,4-benzoquinones in the presence of rose bengal,... 

Treatment of 5,6-dichloro-2,3-dimethyl- -benzoquinone with sodium sulfide followed by oxidation with nitric acid yields the thianthrene derivative (60). Sulfur extrusion from 60 with peracetic acid leads to 2,3,7,8-tetramethyl-l,4,6,9-dibenzothiophene tetrone (61) (overall yield 57%). ... 

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). 

Dihydroxy-l-tetralone Diisoprene 2,3-Dimethoxy-5,6-dimethyl-l,4-benzoquinone Isosclerone ( )-Limonene Aurantiogliocladin... 

The formation of the substituted dibenzofuran-l,4-dione (405) from 5,5 -dimethyl-2,2 -di-p-benzoquinone (406) can be achieved thermally or by photolysis in hydroxylic solvents such as methanol or acetic acid,421 and a related cyclization has been observed in dinaphtha-quinones.422 A dibenzofuran derivative (407) is also obtained on irradiation of the conjugated dione (408) the intermediate (409) can be isolated by maintaining a temperature of 6° in the reaction flask.423 A mechanism for the photorearrangement of 2-acetyl-3-furyl-p-benzoquinones to derivatives of isobenzofuran has been proposed424 [Eq. (109)]. 

Simple, direct and regioselective allylation of 1,4-benzoquinones is an important objective in the synthesis of many isoprenoid quinones such as plastoquinone-1 and vitamin Ki, which play important roles in cellular metabolism and photosynthesis. In a new procedure where the use of a strongly coordinating solvent was found to play an important role, it was shown that reaction of 3 equivalents of (3-methyl-2-butenyl)trifluorosilane with one equivalent of 2,3-dimethyl-l,4-benzoquinone in formamide in the presence of 5 equivalents of FeCl3.6H20 for 23 hours at 40°C gave plastoquinone-1 1, in 90% yield. 

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