Pyrocatechol, 4-Methyl

Preparationbyreactionofchloroaceticacidon3-methyl-pyrocatechol with phosphorous oxychloride in refluxing benzene (28%) [4631]. 

Diazo coupling involves the N exocyclic atom of the diazonium salt, which acts as an electrophilic center. The diazonium salts of thiazoles couple with a-naphthol (605). 2-nitroresorcinol (606), pyrocatechol (607-609), 2.6-dihydroxy 4-methyl-5-cyanopyridine (610). and other heteroaromatic compounds (404. 611) (Scheme 188). The rates of coupling between 2-diazothicizolium salts and 2-naphthol-3.6-disulfonic acid were measured spectrophotometrically and found to be slower than that of 2-diazopyridinium salts but faster than that of benzene diazonium salts (561 i. The bis-diazonium salt of bis(2-amino-4-methylthiazole) couples with /3-naphthol to give 333 (Scheme 189) (612). The products obtained from the diazo coupling are usuallv highly colored (234. 338. 339. 613-616). 

The results of the complexation study of Cu(II), Pb(II), Zn(II), Fe(III), Hg(II), Cd(II), Sn(IV), Zr(IV), Ti(IV) with arsenazo III, sulfonazo III, SPADNS, Eriochrome T, Acid Chrome Dai k Blue, Xylenol Orange, Methyl Thymol Blue, Pyrocatechol Violet, Chrome Azurol S, Eriochrome Cyanin R, Basic Blue K, Methyl Violet, Brilliant Green, Rhodamine C and Astraphoxin in solid phase. The obtained data ai e used for the working out of a new method of metal determination. 

Redox titrants (mainly in acetic acid) are bromine, iodine monochloride, chlorine dioxide, iodine (for Karl Fischer reagent based on a methanolic solution of iodine and S02 with pyridine, and the alternatives, methyl-Cellosolve instead of methanol, or sodium acetate instead of pyridine (see pp. 204-205), and other oxidants, mostly compounds of metals of high valency such as potassium permanganate, chromic acid, lead(IV) or mercury(II) acetate or cerium(IV) salts reductants include sodium dithionate, pyrocatechol and oxalic acid, and compounds of metals at low valency such as iron(II) perchlorate, tin(II) chloride, vanadyl acetate, arsenic(IV) or titanium(III) chloride and chromium(II) chloride. 

Reaction of pyrocatechol dichloromethylene acetaP (133) with dibenzothiophene in the presence of titanium tetrachloride yields o-hydroxjrphenyl-2-dibenzothiophenecarboxylate (134) (100%). This reaction is closely related to the Rieche formylation of dibenzothiophene (Section VI,F, 1) in which a mixture of 2- and 4-dibenzothiophene-carboxaldehyde was obtained. The complete absence of the 4-isomer in this reaction may be due to steric effects at the 4-position between the sulfur atom and the bulky reagent. Hydrolysis of 134 yields 2-dibenzo-thiophenecarboxylic acid (70%). 4-Methyl-3-dibenzothiophenecar-... 

In the presence of trace amounts of water, the tetrameric p,2-oxo complex (182) in 1,2-dimethoxyethane is transformed into a p, -oxo tetrameric complex (183 equation 254), characterized by an X-ray structure.574 In contrast, (182) 572,575 is inactive towards the oxidation of phenols. The reaction of N,N,N, AT -tetramethyl-l,3-propanediamine (TMP) with CuCl, C02 and dioxygen results in the quantitative formation of the /z-carbonato complex (184 equation 255).s76 This compound acts as an initiator for the oxidative coupling of phenols by 02. 6 Such jz-carbonato complexes, also prepared from the reaction of Cu(BPI)CO with 02 [BPI = 1,3 bis(2-(4-methyl-pyridyl)imino)isoindoline],577 are presumably involved as reactive intermediates in the oxidative carbonylation of methanol to dimethyl carbonate (see below).578 Upon reaction with methanol, the tetrameric complex (182 L = Py X = Cl) produces the bis(/z-methoxo) complex (185 equation 256), which has been characterized by an X-ray structure,579 and is reactive for the oxidatiye cleavage of pyrocatechol to muconic acid derivatives.580,581... 

Tsuji and coworkers reported that copper(I) chloride in the presence of pyridine, methanol and dioxygen promotes the stoichiometric oxidation of pyrocatechol to methyl muconate.606 Labeling lg02 studies have shown that only one atom of the dioxygen molecule is incorporated in the substrate, while the other one is transformed into water as in enzymic monooxygenases (equation 275)607 (and not as in dioxygenases, viz. pyrocatechase). This reaction has been shown by Rogic et al. to proceed via two steps (equation 276).580,58 ... 

Dafemer M, Anke T, Hellwig V, Steglich W, Sterner O (1998) Strobilurin M, Tetrachloro-pyrocatechol and Tetrachloropyrocatechol Methyl Ether New Antibiotics from a Mycena Species. J Antibiot 51 816... 

The activity of the 4-alkylpyrocatechols (la), 3-alkylpyro-catechols (lb), 3,5-dialkylpyrocatechols (Ic), 3,6-dialkylpyro-catechols (II), 4,5-dialkylpyrocatechols (III), 3,4,6-trialkyl-pyrocatechol (TV), and 4,5- and 4,6-dialkyl-2-alkoxyphenols (V and VI) was studied in isotactic polypropylene at 180 =t 0.1° C. The relative activities Ar were correlated with substituent constants and redox potentials. In the la series the activity of 4-n-alkyl derivatives exceeded that of 4-tert-alkyl derivatives. The length of the main alkyl chain in la and lb and the steric effects in the latter exerted a specific favorable influence. In agreement with these effects, 3-tert-alkyl-5-methyl derivatives are the most active compounds in Series Ic compounds with other combinations of alkyls are weaker antioxidants as are the isomeric substances II and III or compound IV. Etherification of one hydroxyl group exerts an unfavorable effect influences of substitution in 2-alkoxyphenols (V and VI) are generally the same as in the pyrocatechols Z-ZZZ. 

Nonstabilized polypropylene 2 2-Ethoxy-4-methylphenol 3 2-Methoxy-4-methyl-5-tert-butylphenol 4 2-Methoxy-4-methyl-6-tert-octylphenol 5 4-tert-Amylpyrocatechol 6 3-tert-Octyl-5-tert-butylpyrotechol 7 3-Methyl-5-tert-butylpyrocatechol 8 3-Methyl-6-tert-butylpyrocatechol 9 Pyrocatechol 10 3-Methylpyrocatechol 11 4-Methylpyrocatechol 12 3-tert-Butylpyrocatechol 13 4-n-Amylpyrocatechol... 

Dialkylpyrocatechols. The influences of the nature of substi-ents were followed further with dialkyl derivatives of pyrocatechol at the same time some dependences that had been observed with monoalkyl derivatives were verified. Figure 5 shows that the sensitivity of influencing the antioxidative activity of 3,5-dialkyl derivatives (Type Ic Table V) by steric effects of substituent R1 decreases when substituent R2 increases. Plots are shown for R2 = methyl (line 2) and R2 = ferf-butyl (line 3). The mechanism of action is probably influenced by a more complicated complex of influences of both alkyl substituents. 

Methyl-3-tert-octylpyrocatechol 2 Pyrocatechol 3 4-tert-Octylpyrocatechol... 

Alkoxyphenols. Interesting dependences, again illustrating the ihfluences of the nature of pyrocatechol substitution, were found on observing the properties of 2-alkoxyphenols (Types V and VI, R = methyl, ethyl, or tert-butyl). Ethoxy derivatives were generally more active than methoxy derivatives however, all substances studied were... 

The reaction of perfluoroisobutylene with the disodium salt of pyrocatechol in dime thy lformamide yields 2-[2,2,2-trifLuoro-1 -(trifluoro-methyl)-ethylidene]-l,3-benzo[tf] dioxolane (78JFC( 12)211, 73NKK563). 

SYNS 5-ALLYL-1.3-BENZODIOXOLE ALLYL-CATECHOL METHYLENE ETHER ALLYLDIOXY-BENZENE METHYLENE ETHER l-ALLYL-3,4-METHYT.ENEniOXYBENZENE 4-AIl,YL-l,2-METHYI.ENEDIOXYBENZENE m-ALLYLPYRO-CATECHIN METHYLENE ETHER 4-ALLYI.PYRO-CATECHOL FORMALDEHYDE ACETAL ALLYL-PYROCATECHOL METHYLENE ETHER 1,2-METHYL-ENEDIOXY-4-ALLYLBENZENE 3,4-METHYL-ENEDIOXY-ALLYLBENZENE 5-(2-PROPENYL)-l,3-BENZODIOXOLE RCA WASTE NUMBER U203 RHYUNO OIL SAFROLE SAFROLE MF SHIKIMOLE SHIKOMOL... 

Storage Substances The reagent should always be freshly made up. Pyrocatechol violet Mobile phase Methyl isobutyl ketone — pyridine — glacial acetic add (97.5 + 1.5 + 1). 

In contrast to monohydric phenols, also non-alkylated pyiocatechol or hydro-quinone and their monomethyl derivatives are antioxidation effective. During the oxidation in water-alcoholic alkaline medium, 2,5-dihydroxy-l,4-benzoquinone CLII189 190,193 and 2-hydroxy-5-methyl-1,4-benzoquinone19 are formed from pyrocatechol and 4-methylpyrocatechol, respectively. The oxidation of 2-methyl-hydroquinone is more complex and more products are formed. Besides ion radicals CXXXVII and CXLI, also the ion radical CLIII was identified198 in the study of reaction mechanism. Intermediate CLIII corresponds to the formation of dimeric hydroxybenzoquinone CLIV. 

Pyrocatechol Dipropylene glycol a-Trichlorotoluene m-Nitrotoluene p-Nitrotoluene o-Anisidine Enanthic acid Methyl salicylate p-Ethylphenol 3,4-Xylenol o-Phenetidine... 

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