Benzoquinone 5,6-dimethoxy-3- methyl

Coenzyme Qo (2,3-Dimethoxy-5-methyl-l,4-benzoquinone, 3,4-dimethoxy-2,5-tolu-quinone, fumigatin methyl ether), colchicine and colchicoside see entries in Chapter 6. 

Coenzyme Q4 (Ubiquinone-4, 2,3-dimethoxy-5-methyl-6-[3,7,ll,15-tetrametbyl-hexadeca-2/,6/,10/,14-tetraenyl]-[l,4]benzoquinone [4370-62-l]M 454.7, m 30 , 33-45 , A (275nm) 185. A red oil purified by TLC chromatography on Si02 and eluted with Et20-hexane. Purity can be checked by HPLC (silica column using 7% Et20-hexane). It has A- ax 270 nm (e 14,800) in pet ether. [NMR and MS Naruta J Org Chem 45 4097 1980 cf Morton Biochemical Spectroscopy (Adam Hilger, London, 1975) p 491]. It has also been dissolved in MeOH/EtOH (1 1 v/v) and kept at 5 until crystals appear [Lester and Crane Biochim Biophys Acta 32 497 1958]. 

In a search for allelopathic agents from common weeds, Amaranthus palmerl S. Wats (Palmer amaranth) and Ambrosia artemisiifolia L. (Louisiana annual ragweed) have been analysed for their organic natural products. From A. palmerl phytol, chondrlllasterol, vanillin, 3-methoxy-4-hydroxynitrobenzene and 2,6-dimethoxy- benzoquinone were isolated. From the roots of Ambrosia artemisiifolia four polyacetylenes, a mixture of sesquiterpene hydrocarbons, methyl caffeate, and a mixture of 8-sitosterol and stlgmasterol were obtained. 

Commercial 2,3-dimethoxy-5-methyl-1,4-benzoquinone (Aldrich Chemical Company, Inc.) was used without further purification. 

Ubiquinone-1 p-Benzoquinone, 2,3-dimethoxy-5-methyl-6-(3-methyl-2-butenyl)- (8) 2,5-Cyclohexadiene-1,4-dione, 2,3-dimethoxy-5-methyl-6-(3-methyl-2-butenyl)- (9) (727-81-1)... 

In the case of benzoquinone monoacetals 61, the two substituents at the 4-position are equal, and side-selective addition Re versus Si face) creates a single stereocenter (Scheme 7.17(a)). In the (S, R, R)-18/Cu(OTf)2-catalyzed 1,4-addition, depending on the nature of the R2Zn reagent and the size of the acetal moiety, enantioselectivities ranging from 85-99% were found (Table 7.4). The highest ees are provided by a combination of a small acetal moiety and Me2Zn 99% ee was obtained with 4,4-dimethoxy-5-methyl-2-cyclohexenone, for example. 

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). 

One of the carbazole-l,4-quinones, 3-methoxy-2-methylcarbazole-l,4-quinone (941), required for the total synthesis of carbazomycin G (269), was already used as a key intermediate for the total synthesis of carbazoquinocin C, and was obtained by the addition of aniline (839) to 2-methoxy-3-methyl-l,4-benzoquinone (939), followed by oxidative cyclization with catalytic amounts of palladium(II) acetate (545,645) (see Schemes 5.124 and 5.125). Similarly, in a two-pot operation, 4-meth-oxyaniline (984) was transformed to 3,6-dimethoxy-2-methylcarbazole-l,4-quinone... 

Cyclohexadienes are available by the methodology of Birch, and the reactions of l-methoxy-, 1,3-dimethoxy-, l,3-bis(trimethyl-silyloxy)-, and l-methoxy-4-methyl-l,3-cyclohexadiene with a number of 1,4-benzoquinones have been investigated. Acid treatment of the adducts and subsequent dehydrogenation provides a synthesis of 2-dibenzofuranols. Thus the adduct 159 (Scheme 41) from 1,4-benzoquinone and 1,3-dimethoxy-1,3-cyclohexadiene, on treatment with a trace of concentrated hydrochloric acid in ethanol at room temperature, affords the tetrahydrodibenzofuranone 161. When the adduct 159 is heated under reflux in aqueous methanol, the reaction can be arrested at the dihydrodibenzofuran 160. The tetrahydrodibenzofuranone 161 on dehydrogenation with palladized charcoal affords 2,7-dibenzofurandiol. ... 

Dimethoxy-5-methyl-l,4-benzoquinone see Coenzyme Qo entry in Chapter 5. 

Fumigatin [484-89-9] (3-hydroxy-2-methoxy-5-methyl-/>-benzoquinone) is isolated from metabolism of Aspergillusjumigatus and is used as an antimicrobial. 5-Allyl-l,6-dimethoxy-2,3-methylenedioxybenzene (dillapiole) (62) is a synergist for pyrethrum. Derivatives have been prepared and evaluated (216). 

H-l,4-Benzoxazine 2,3-Dimethoxy-carbonyl-4-hydroxy-6-methyl-E9a, 145 (1,2-Benzoquinon-oxim/ Cu + ROOC-C = C —COOR) Kohtensaure tert.-Butylperoxyes.ter-phthalimidoester E13/1, 255 (C-Cl -> C-O-OR) 1,2-Oxazol rro i-3,5-Dimethoxycar-bonyl-4-phenyl-4,5-dihydro- -2-oxid E14b, 927 (R-N02 + R-CHO)... 

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