Catechol monomethyl ethers

Guaiacol. One of the most favorable assay methods for peroxidases involves the oxidation of guaiacol. This compound, catechol monomethyl ether, forms part of the guaiaconic acid molecule and was first obtained by distillation from the resin. On oxidation with peroxidase and H2O2 it forms tetraguaiacol the structure of which was evaluated by Bertrand, in 1903 (61), who formulated the reaction as follows ... 

Guaiacol is the monomethyl ether of the diphenol, catechol, or ortho-dihydroxybenzene. Its constitution is—... 

Glycol monomethyl ethers Monoepoxides Hydroquinone and catechol Phenol... 

The activation parameters are similar to those for the overall reactions of quinol and its monomethyl ether (above). The pH dependence of 2 shows a gradual increase in the range pH 1-4, then a more rapid increase to a maximum at pH 8.5, followed by a rapid decrease. Kaiser and Weidman accounted for this quantitatively by assuming reactions of catechol with HsIOg and a periodate monoanion, and either reaction of catechol with or reaction of the... 

Cannon, J.G. and Qijie, P. (1991) Isomeric monomethyl ether derivatives of (RS)-9,10-dihydroxyaporphine ("isoapomorphine") as possible products of metabolism by catechol-O-m ethyl transferase. J. Med. Chem 34, 1079-1082. 

The oxidation of a catechol derivative to an o-benzoquinone is the first step in a synthesis of pyocyanine (6) introduced hy Wrede and Strack and further developed by Surrey. Pyrogallol monomethyl ether (1) is oxidized by shaking a solution in... 

Catechol is also employed for the industrial antioxidant 4-tert-butylcatechol, and its monomethyl ether, guaiacol is used for the production of vanillin (10). This account is by no means a complete summary of the applications of the dihydric phenols more of which have been listed elsewhere (ref. 38). 

An enantioselective Stetter employing a chiral NHC and Hunig s base (EtNPr-j ) in methanol at 0°C has its yield massively boosted by addition of 1 equiv of catechol (1,2-dihydroxybenzene), whereas other phenols such as isomers of catechol or its monomethyl ether have negligible effect. Studies of deuterium kinetic isotope effects suggest that initial proton transfer from catechol (97) to form the aryl anion equivalent (98) is turnover limiting. Intramolecular examples are also described, requiring subpercentage amounts of NHC, base, and catechol. 

Using methyl ethers of di- and tri-hydric phenols, selective mono-demethylation occurs, e.g. resorcinol monomethyl ether is obtained from resorcinol dimethyl ether and sodium ethanethiolate in DMF. An exception is pyrogallol trimethyl ether which afforded pyrogaUol 1-monomethyl ether in high yield. Methylene ethers, such as methylenedioxybenzene, can be quantitatively converted to catechol, via the intermediate formation of ethyl o-hydroxyphenoxymethyl sulphide . 

Quinacetophenone is similarly monomethylated with methyl iodide-potassium carbonate, but the dimethyl ether is formed with excess dimethyl sulphate and caustic soda [8]. Methyl-ation of catechol groups can be prevented by carrying out the reaction in the presence of a borate salt. A useful preparation of 3-0-methylgallic acid (17) is based on this principle [33]. 

---