Methyl muconate

Fig. 9.72Structures of MCPA(4-chloro-2-methylphenoxyacetic acid (I)), its metabolites 4-chloro-o-cresol (II), 5-chloro-3-methyl catechol (III), 4-chloro-2-methyl muconic acid (IV), reagent pentafluorobenzyl bromide (V), and the derivatives VI-VIII from l-lll Source Reproduced with permission from the American Chemical Society [155]... 

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 ... 

Norite, is heated to boiling by introduction of steam, filtered through a Norite filter pad by suction, and cooled in an ice-salt bath. The muconic acid is precipitated by the addition of a large excess (1500 ml.) (sp. gr. 1.18) of concentrated hydrochloric acid to the cold solution. The acid is added in a thin stream to the well-stirred solution. After 2 hours the muconic acid is filtered, washed first with two 400-ml. portions of cold water and then with 200 ml. of methyl alcohol, and dried at 85°. The yield of nearly colorless product melting at 296-298°, with decomposition, amounts to 165-195 g. (37-43%). 

METHYL-l-METHYLENE-2-(r-METHYLETHYL)-, R,R-), 65, 81 MICHAEL ADDITION, APROTIC, 66, 37, 41 cis.cis-Monornethyl muconate (61186-96-7), 66, 180, 184 cis.cis-MONOMETHYL MUCONATE FROM 1,2-DIHYDROXYBENZENE, 66. 180... 

More extensive studies with 1 have been reported by Rogic and co-workers in connection with new synthetic approaches to caprolactam. They established that I can cleave o-quinones, catechols, and phenols under anaerobic conditions. Thus catechol, o-benzoquinone, and phenol are oxidized by 1 to m,m-muconic acid methyl ester. The paper presents several lines of evidence that oxygen docs nol... 

The enzyme catalyzes the intradiol cleavage of catechol with the insertion of 2 atoms of molecular oxygen to form e/s.c/s-muconic acid. The enzyme also catalyzes the oxidation of various catechol derivatives, including 4-methylcatechol, 4-chloro-catechol, 4-formylcatechol (protocatechualdehyde), 4,5-dichlorocatechol, 3,5-di-chlorocatechol, 3-methylcatechol, 3-methoxycatechol, and 3-hydroxycatechol (pyro-gallol). All of these substrates give products having an absorption maximum at around 260 nm characteristic of t7s-c/s-muconic acid derivatives. However, when 3-methylcatechol is used as a substrate, the product formed shows an absorption maximum at 390 nm besides that at 260 nm. These two absorption maxima are found to be attributable to two different products, 2-hydroxy-6-oxo-2,4-heptadienoic acid (7), and 5-carboxy-2-methyl-2,4-pentadienoicacid(2-methylmuconic acid), (2) [Eq. (19)]96. ... 

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... 

The second type is oxidative dicarbonylation of acetylene with PdCb in benzene, which produces chlorides of maleic, fumaric and muconic acids [130], Methyl maleate (215), fumarate (216) and muconate (217) are obtained in MeOH containing thiourea by passing acetylene and oxygen in the presence of a catalytic amount of PdCb [131]. 

The mixture of catechols was subjected to the lead tetraacetate cleavage conditions, giving the corresponding muconates (197 only shown) which were reoxidized and esterified to the corresponding C-2 methyl esters (199 only shown), again with no C-2 epimerization observed. Unfortunately, the hydrolysis with concomitant pyrone formation gave rise to a complex mixture of products, ruling out this method for the synthesis of acromelic acid B 6 (Scheme 75—major isomers only shown). 

Conjugated dienes are a special substrate for the TMM synthon because they can potentially undergo [3 + 2] as well as [4 + 3] cycloaddition. While dimethyl ( . )-muconate gives only seven-membered ring [4 + 3] adducts, methyl 2,4-pentadienoate reacts exclusively at the terminal double bond with (79) to give a vinylmethylenecyclopropane (equation 100). The diphenyl system (81) also reacts with simple 1,3-dienes to produce only diphenylidenecyclopentanes in the presence of Ni or Pd catalysts (equation 101). ... 

The choice of liquid phase can affect the course of ozonation. This has been shown with phenylindenes by Miura et al. (1985) and with lignin models by Kratzl et al. (1976), who found that 4-methylveratrole gave a higher yield of dimethyl -methyl-cis,cis-muconate in 45% aqueous acetic acid than in dichloromethane and that the yield of dimethyl oxalate from acetoveratrone was markedly dependent on the solvent. Eriksson and Gierer (1985) found that in methanol the benzene ring of vanillin is cleaved (albeit only very slowly, after acetalization has occurred), but that in nonprotic solvents, such as acetone, the initial reaction is oxidation of the aldehyde function to a carboxyl group. 

This work was repeated by several groups in the reaction of sodium dimethyl-malonate with methyl sorbate, Farmer and Metha observed small amounts of the 1,4-adduct besides the 1,6-addition product. Difficulties in conducting the transformations and analyzing the products are evident from reports on malonate additions to ethyl muconate depending on the reaction conditions, the expected 1,4-adduct (equation 4) or isomerization products formed by double bond displacement were isolated. Nucleophilic 1,4- and 1,6-addition reactions to 2,4-pentadienenitrile were also repor-... 

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