Conversion into catechol

Nitrite during conversion of 2-nitrotoluene into catechol (An et al. 1994), 2,4-dinitrotoln-ene into 4-nitrocatechol (Spanggord et al. 1991), and 1,3-dinitrobenzene to 4-nitrocatechol (Dickel and Knackmuss 1991). 

Cyclic carbonates. For conversion of catechol into phenylenecarbonate, " 1 mole of the phenol li dlisolved under nitrogen in a deaerated solution of 2.2 moles of, 011... 

Similar protocol was applied in the first total synthesis of KDN from non-carbohydrate sources [138]. Catechol derivative 228 was transformed into protected tetraol 235, according to the literature method [139] (Scheme 51). This, in turn, underwent smooth ozonolytic cleavage to give after reductive work-up the ester alcohol, which was converted, over three steps, into the unstable D-mannose derivative 236. Reaction of compound 236 with pyruvate anion equivalent gave a syn product 237, accompanied by the another isomer (3 2). Conversion into KDN was performed in two steps involving ozonolytic cleavage of the double bond, then deprotection with concomitant cyclization using TFA-water mixture. 

The brief duration of bronchodllation is a result of facile metabolic Inactivation. Upon reaching systemic circulation isoproterenol is rapidly accumulated into extraneuronal cells, perhaps by an uptake-2 process (13), where, except in the gut, it is inactivated in a reaction catalyzed by catechol 0-methyltransferase (COMT) which methylates the meta-OH group (14). Isoproterenol s lack of activity following oral administration is a consequence of its metabolic conversion into readily excreted meta- or para-ethereal sulfates by sulfoklnases in the Intestine (15). 

Carboxylic acids are not reduced by NaBHa. The conversion into primary alcohols can be achieved by using NaBHa in combination with powerful Lewis acids, Sulfuric Acid, Catechol Trifluoroacetic Acid or In these cases the... 

Figure 5. The biocatalytic pathway (boxed arrows) created for microbial conversion of D-glucose into cis, cw-muconate from the perspective of the biochemical pathways from which the enzymes were recruited. Conversion of D-glucose into DHS requires transketolase (tkt) from the pentose phosphate pathway and DAHP synthase (aroF, aroG, aroH)y DHQ synthase aroB and DHQ dehydratase aroD) from the common pathway of aromatic amino acid biosynthesis. Conversion of DHS into catechol requires DHS dehydratase (aroZ, enzyme A) from hydroaromatic catabolism, protocatechuate decarboxylase aroY, enzyme B), and catechol 1,2-dioxygenase (caM, enzyme C) from the benzoate branch of the p-ketoadipate pathway. (Adapted and reproduced with permission from ref. 21.)...

The purpose of this work was to increase the A3 selectivity at low conversion through a catalyst modification. Previous studies of phenol alkylation with methanol (the analogue reaction) over oxides and zeolites showed that the reaction is sensitive to acidic and basic properties of the catalysts [3-5]. It is the aim of this study to understand the dependence of catalyst structure and acidity on activity and selectivity in gas phase methylation of catechol. Different cations such as Li, K, Mg, Ca, B, incorporated into y-Al203 can markedly modify the polarisation of the lattice and consequently influence the acidic and basic properties of the surface [5-8] which control the mechanism of this reaction. 

In independent experiments, 4 g phenol (PHE) was dissolved in 50 mL water, the solution mixed with 0-2.0 mL H2O2, and injected immediately into GC system to measure the apparent conversion of PHE as well as yields of catechol (CAT), hydroquinone (HQ), and para-benzoquinone (BQ). Ethanol was used as the inner standard. [Reproduced by permission of Elsevier from Ma, N. Ma, Z. Yue, Y. H. Gao, Z. J. Mol. Catal. A 2002,184, 361-370.]... 

Corey and J. E. Anderson154 have described a useful method for the conversion of alcohols into iodides by employing the reagent 120, which is readily prepared from catechol and phosphorus trichloride. Reaction of 120 in ether solution with an alcohol in the presence of pyridine affords the corresponding phosphite 121. Treat-... 

This reaction is catalysed by enzyme methyl-transferases (catechol-o-methyl-transferase) and generally uses S-adenosylmethionine as a methyl donor. Examples are conversion of norepi-nephrine into normetanephrine, which has less than one percent of the vasoconstrictor activity of the parent compound. 

With tyrosinase, on the contrary, a two-electron oxidation occurs, as no EPR signal was detected in the catechol oxidation at pH 5.3 Melanins are polymerization products of tyrosine, whereby tyrosinase catalyses the first steps the formation of dopa (3,4-dihydroxyphenylalanine) and of dopaquinone, leading to an indolequi-none polymer The peroxidase mechanism for the conversion of tyrosine into dopa in melanogenesis was not substantiated In natural and synthetic melanins free radicals of a semiquinone type were detected by EPR 4-10 x 10 spins g of a hydrated suspension (the material was modified on drying and the number of free spins increased). The fairly symmetrical EPR signal had a g-value of 2.004 and a line-width of 4-10 G The melanins seem to be natural radical scavengers. 

Apart from nitrophenols, 4-nitrocatechol and nitrobenzoquinone have also been detected as nitro derivatives [54,79,100]. They are secondary photoproducts and are thought to originate from the nitration of catechol and hydroquinone, in the latter case followed by the oxidation of nitrohy-droquinone [54,100]. 4-Nitrocatechol might in principle derive from catechol nitration or from 4-nitrophenol hydroxylation. However, the conversion of 4-nitrophenol into 4-nitrocatechol upon nitrate photolysis is rather limited [109] and cannot account for the observed time evolution starting from phenol [54]. 

---