Phenolic hydroxyl group Etherification

Properties. Vanillin is a colorless crystalline solid mp 82-83 °C) with a typical vanilla odor. Because it possesses aldehyde and hydroxyl substituents, it undergoes many reactions. Additional reactions are possible due to the reactivity of the aromatic nucleus. Vanillyl alcohol and 2-methoxy-4-methylphenol are obtained by catalytic hydrogenation vanillic acid derivatives are formed after oxidation and protection of the phenolic hydroxyl group. Since vanillin is a phenol aldehyde, it is stable to autoxidation and does not undergo the Cannizzarro reaction. Numerous derivatives can be prepared by etherification or esterification of the hydroxyl group and by aldol condensation at the aldehyde group. Several of these derivatives are intermediates, for example, in the synthesis of pharmaceuticals. 

Etherification by alkylation of an alcoholic or phenolic hydroxyl group... 

Although the esterifiction of phenols and also their etherification (considered in the next chapter) can be regarded as protective methods for the phenolic hydroxyl group there have been few developments in this aspect of phenolic chemistry. The definitive text on this topic remains relevant (ref,59). 

The reactions of the phenolic aldehydes may be conveniently grouped under etherification of the phenolic hydroxyl group, replacement of the aldehyde group and condensation reaction of the latter. 

Hydroxyl protection. Useful variations in chemoselectivity for the etherification of compounds containing different types of hydroxyl groups use TrCl and l-BuMe2SiCl. Thus, o-hydroxybenzyl alcohol is silylated at the aliphatic moiety but tritylated at the phenolic oxygen. 

One of the low temperature reaction products of phenol and formaldehyde is sodium trimethylolphenol Etherification at the phenolic hydroxyl, by an alkyl halide, retards resinification and makes methylol groups available for a number of other reactions. 

Most derivatizations for gas chromatography are esterifications or etherifications. For example, analytes containing carboxyl groups are often converted into methyl [156], [161], pentafluorobenzyl [255]-[258], or triethyl esters [259]-[261], Analytes containing acidic hydroxyl groups (phenols, chlorophenols, glycol ethers) or amino groups (e.g.. aniline) can be derivatized with such per-fluorinated compounds as heptafluorobutyric anhydride, pentafluoropropionic anhydride [169], or pentafluorobenzoyl chloride [262]. 

Phenolic resins are well known for their contribution in improving hardness, gloss, and water and chemical resistance in oleoresinous varnishes. Those based on p-alkyl-substituted phenols and with heat-reactive methylol groups have also been incorporated into alkyd resins. The reaction has not been well smdied. Presumably, the methylol group would react with the unsaturation functionality on the fatty acid chain to form the chroman stmcture, similar to what is believed to have occurred in the varnish. Etherification between the methylol group and free hydroxyl of the alkyd resin, catalyzed by the residual acidity in the resin, would be another possible reaction. 

Scheme 3.2 shows per-functionalized pillar[5]arene derivatives prepared from per-hydro)ylated pillar[5]arene 3.6 as a starting compound. Applying an efficient organic reaction is required for the perfect introduction of functional groups at all 10 reaction sites. A straightforward and efficient functionalization process for per-hydroxylated pillar[5]arene is etherification, which has been used for functionalization of the lower rims of phenolic moieties in calix[ ]arene derivatives. Various functionalized pillar[5]arene derivatives can be obtained by etherification of per-hydroxylated pillar[5]-arene with an alkyl-halide in the presence of appropriate bases, such as NaH and K2CO3. Introduction of the substituents can change various physical... 

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