Methoxy hydroquinone

Nonni et al. [42] subsequently confirmed the validity of these model compound experiments when they found methoxy hydroquinone (1) in the spent peroxide bleaching liquors of a thermomechanical pulp (TMP) mill. Holah and Heitner [43] showed, at long reaction times and with a large excess of peroxide, that an absorption band with = 320 nm was removed. They attributed this to slow removal of a-carbonyl... 

Using neutral (pH 7) hydrogen peroxide Oki et al. [44] isolated methoxy hydroquinone and methoxy benzoquinone from the reaction of vanillin and acetovanillone with hydrogen peroxide. Other p-hydroxybenzaldehydes were degraded in a similar way. Hirashima and Sumimoto [45] obtained evidence for the presence of quinones in mechanical pulps, using a photochemical reaction with acetaldehyde. 

COCH3 Preparation by Fries rearrangement of 2-methoxy-hydroquinone diacetate,... 

Vinyl ethers and a,P unsaturated carbonyl compounds cyclize in a hetero-Diels-Alder reaction when heated together in an autoclave with small amounts of hydroquinone added to inhibit polymerisation. Acrolein gives 3,4-dihydro-2-methoxy-2JT-pyran (234,235), which can easily be hydrolysed to glutaraldehyde (236) or hydrogenated to 1,5-pentanediol (237). With 2-meth5lene-l,3-dicarbonyl compounds the reaction is nearly quantitative (238). 

Reaction of 2,3-dihydro-3-hydroxy-3-methyl- 240 (R = Me), or a mixture of 2,3-dihydro-3-hydroxy-3-aryl-57/-pyrido[l,2,3-dfe]-l,4-benzoxazin-5-ones 240 (R = Ar) and (8-aroylmethoxy)quinolin-2(l//)-ones 241 (R = Ar) with ethyl 2-(bromomethyl)acrylate in the presence of activated Zn and hydroquinone gave 8-[(2,3,4,5-tetrahydro-4-methylidene-5-oxo-2-furanyl)-methoxy]quinolin-2(l//)-ones (242) (97HCA1161). 6,7-Dihydro derivatives of 240 reacted similarly (00HCA349). 

CiiHijNO, 3SS4J-4J-7) see Carboquone 2-(2-aminocarbonyloxy-l-methoxyethyl)-S-methyl-hydroquinone dimethyl ether (CjjHiijNOj 38843-63-9) see Carboquone [6U-[6a,7a,7(iJ )])-3-[[(aminocarbonyl)oxyJmethyl]-7-[[5-carboxy-S-[[(4-methylphenyl)sulfonyl]amino]-l-oxo-pentyl]amino]-7-methoxy-8-oxo-5-thia-l-azabicy-clo[4.2.01oct-2-ene-2-carboxylic acid compd. with A-cyclohexylcyclohexanamine (1 1)... 

In a high-pressure autoclave, arranged for agitation by shaking or rocking, are placed 286 g. (336 ml., 4.08 moles) of croton-aldehyde, 294 g. (5.06 moles) of methyl vinyl ether, and 1.1 g. of hydroquinone (Notes 1 and 2). The autoclave is heated to 200° (Note 3) and held there for 12 hours. The autoclave is cooled and vented, and the black product is distilled through a 1 by 60 cm. helix-packed column. The yield of 3,4-dihydro-2-methoxy-... 

To a mixture of 1-methoxy-l,3-butadiene (1 55.3 g, 0.66 mol) [43] and n-butyl glyoxylate (86.0 g, 0.66mol) [44], 0.1 g hydroquinone was added and the solution was refluxed at 100°C for 6 h under argon. Distillation at 88°-90°C/0.5 tonr gave 2 (R = Bu) (91.6 g, 65%) as a pale-yellow liquid with a faint odor. By gas chromatography this product is a mixture of cis and trans (ca. 7 3) isomers. Treatment of the isomer mixture in dichloro-methane solution with p-toluenesulfonic acid or zinc chloride for 2 h leads to an almost pure trans-isomer (ca. 95%). 

Carboxybenzyl aryl ketones are formed together with the isocoumarin when homophthalic anhydride (isochroman-l,3-dione) is used to acylate aromatic molecules under Friedel-Crafts conditions (51JOC1064) and the 7-methoxy derivative behaves in a similar fashion (66JIC615). Some care in the choice of Lewis acid is necessary in view of the formation of the tropone derivative (504) in the acylation of hydroquinone (Scheme 181) (55JCS2244). 

Complex polyfunctional molecules can often be assembled efficiently by short, spectacular sequences of reactions, an example of which is the preparation of the pentasubstituted benzofuran 1. Thus, addition of l-lithio-l-methoxy-3-(trimethylsilyl)-l,2-hexadiene to 3,4-dimethoxycyclobut-3-ene-l,2-dione gave the expected keto alcohol in 70% yield. This alcohol was heated at reflux temperature in toluene for 4 hours to give a 2,3,5,6-tetrasubstituted hydroquinone in 90% yield. Oxidation of the hydroquinone with silver oxide and potassium carbonate in anhydrous benzene (90%) followed by reaction of the quinone thus obtained with TFA in methylene chloride at 0°C then at room temperature for two days gave 1 in 75% yield. 

Allyl-2-methoxy phenol. (10) Hydroquinone monomethyl ether. 

In solid HPC film methoxy-p-benzoquinone Q shows absorption maximum at 352 nm (figure 5) ascribable to a nn transition [12]. The weak band observed at 530 nm is likely due to the dibenzofurane-l,4-quinone F formed in small yield during the preparation of the film. After 30 min irradiation, the bands of the quinone chromophore disappear completely (Figure 5) giving rise to absorption similar to that of hydroquinone A irradiated for one hour (Figure 1). Such behaviour is also observed, as is shown below, when D is adsorbed on filter paper. 

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