Catechol derivative mixture

Synonyms catechol derivative mixture rhus toxicodendron... 

Mixture B K[SiPh(3-fcat)2 and K[SiPh(dbcat)2] (3-fcat 2,3-dihydroxybenzaldehyde, dbcat 3,5-di-f-butylcatechol) contained two complexes with asymmetric catechols. Each complex showed the presence of two resonances due to the isomerism described above. The equilibrated mixtures showed the presence of two further species (Figure 9). These are attributed to isomers of the [SiPh(3-fcat) (dbcat)]- anion. Equilibrium was not established even after 8 weeks, whereupon decomposition prevented a more quantitative kinetic analysis. Flowever, it is apparent from the two experiments described that the kinetics of redistribution of ligands between complexes varies dramatically according to the cate-cholate involved. It is reasonable to conclude that the rate of redistribution decreases as the strength of the catecholate derivative increases. The nonstatistical distribution of complexes in a mixture indicates a thermodynamic stability of the complexes in Me2SO. The likely explanation lies in the electronic rather than the steric effects in the complex, since the live-coordination imposes little steric constraint. 

Attempts to hydrolyse the ester 2 with either KOH/IfyO/MeOH at 50°C or LiOH/THF/IfyO at reflux or AcOH in quinoline at 120°C were unsuccessful, and the starting material was recovered unchanged. Use of KO Bu/DMSO at 40-60°C for 4 hours, however, followed by aqueous acid gave a mixture of four products, the major of which (80%) was shown to be the acid 3. Ether cleavage of 3 with BBr3/CH2Cl2 at room temperature proceeded rapidly (5 min), and while the catechol derivative could be isolated and characterised spectroscopically, it was rapidly oxidised in air to 4, the potent benzodiazepine agonist miltirone. 

A series of catecholate derivatives 189 and 190 were prepared from the parent dichloro complexes by reaction with o-catechol or tetrachloro-o-catechol and Me3N in hot methanol.83 The corresponding reaction with an unsymmetrical catechol, 3,5-di-ferf-butylcatechol produced a mixture of isomers 191a and 191b. The related dioxolene complexes 192 and the amidophenolate complexes 193 were also prepared by the same method. An X-ray crystal structure on the latter complex shows that the phenolate oxygen is trans to the aryl carbon atom. 

Stable pentacoordinated allylsiliconates have been employed in aldehyde addition reactions. These reagents require no activation by Lewis acids or Lewis bases, but have found only limited applications in synthesis to date. The use of these agents in addition to aldehydes was first described in 1987 by Corriu [59] and Hosomi [60] and by Kira and Sakurai [61] in 1988. In these reactions, the addition of a catechol or 2,2 -biphenol-derived allylsiliconate to an achiral aldehyde led to the highly regio- and stereoselective formation of homoallylic alcohols. For example, the addition of the catechol-derived 2-butenylsiliconate 81 (90/10 E Z) provided a diastereomeric mixture of homoallylic alcohols 74 and 75 in a 90/10 ratio (Scheme 10-33) [60c]. 

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. 

Fig. 106. Separation of methoxyphenylpropane derivatives (4 (xg of each) on a silica gel G layer, using benzene. S-chamber 10 cm run, lasting 35 min spray reagent molybdophosphoric acid solution (No. 168). T Desaga test mixture 1 safrole 2 methylchavicol S myristicin 4 apiole 5 eugenol methyl ether 6 asarone 7 tetra-methoxyallylbenzene 8 elemol 9 catechol G mixture (2 [xg of each)...

Urushi is a Japanese traditional natural paint. The main component of urishi is urishiol (Scheme 12.21), whose structure is a catechol derivative with unsaturated hydrocarbon chains consisting of a mixture of monoenes, dienes and trienes at the meta or para position of catechol. Kobayashi and co-workers [204] have carried out laccase-catalysed crosslinking reactions with urishiolanalogues to prepare urishi. The HRP-catalysed polymerisation of w-ethynylphenol (HO-Cf H4-C=CH), containing more than one polymerisable group, showed that the phenol moiety was chemoselectively polymerised when an acetylene or methacryl group were present [205]. 

Urushiol, the first constituent mentioned, is a mixture of 3-substituted catechol derivatives with a 15 or 17 carbon chain having a olefin number 0-3253,5. The average number of olefins in the side chain of urushiol is 2.0-2.5. Constituents of this Japanese lacquer urushiol are seen to be the same as those of urushiol in poison ivy of U.S.A.5... 

C and obtain the symmetrical regioisomer 39 as the major product. Unlike the regioisomeric mixtures of catechol-derived products shown in Scheme 1.10, those pinacol-derived triborylated benzenes could be separated. Thus, compound 39 could be obtained in pure form and submitted to various couplings to give oligoaryls 41 to 46. 

The oriental lacquer is prepared from the sap of the varnish tree" Rhus verni-ciflua, which is an emulsion of an aqueous phase and an organic phase called urushi-ol. The urushi fraction consists of a mixture of catechol derivatives substituted in 3-po-sition with aliphatic C- 5 or C- 7 side chains. About 60% of these side chains are trie-nes. The structure of the trienes is similar to that in linseed or tung oil and is essential for the effectiveness of the oxidative curing of oriental lacquer. We have utilized new techniques and used combinations of modern techniques to analyze the urushiol mixtures and to characterize and identify each individual compound. We have also developed ultraviolet stabilizers for oriental lacquer, stabilizers that could be incorporated into the polymerizing mixture during the curing process to result in ultraviolet stabilized oriental lacquer. 

The difference between the oriental lacquer trees of the Rhus variety and the rubber tree is that the rubber trees have polyisoprene as the desirable ingredient while the urushi components are mixtures of substituted catechol derivatives. 

DISCUSSION. Caution should be exercised when interpreting chromatograms from a complex mixture of aromatic compounds in urine. This is especially true when excretion of the catechols is very high. When the derivatives of the compound extracted from urine of patients with phenylketonuria are prepared decomposition products of the large amounts of phenylpyruvic acid present give rise to peaks which interfere with and resemble HVA. When difficulties of this type are suspected, differential extraction of the urine can be performed. When alkaptonuria urine is extracted with dichloromethane, homovanillic acid is extracted preferentially, leaving the spurious compounds behind. 

Adamic and Bartak [6] used high pressure aqueous size exclusion chromatography with reverse pulse amperometric detection to separate copper(II) complexes of poly(amino carboxylic acids), catechol and fulvic acids. The commercially available size exclusion chromatography columns were tested. Columns were eluted with copper(II) complexes of poly(aminocarboxylic acids), citric acids, catechol and water derived fulvic acid. The eluent contained copper(II) to prevent dissociation of the labile metal complexes. Reverse pulse electrochemical measurements were made to minimise oxygen interferences at the detector. Resolution of a mixture of DTP A, EDTA and NTA copper complexes was approximately the same on one size exclusion chromatography column as on Sephadex... 

Derivatives of phenol or aniline can be oxidized to quinones, the yield and ease of oxidation depending on the substituents. If an amino or hydroxyl group is in the para position, the reaction proceeds readily, as illustrated by the synthesis of quinone from hydroquinone by oxidation with a sodium chlorate-vanadium pentoxide mixture (5>6%) or with chromic-sulfuric acid mixture (92%). A para halogen atom usually has a favorable effect. Any group in the para position is eliminated or oxidized. o-Quinones are usually prepared from the corresponding catechols. A survey of procedures for the synthesis of benzoquinones by oxidation has been made. ... 

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