Abstract
In several cases, the occurrence of methylation on oxygen site of an organic molecule is not a straightforward process. Most of the O-methylations take place with hydroxyl groups of carboxylic acids, phenols, and alcohols, affording methyl esters, aryl methyl ethers, and alkyl methyl ethers, respectively. Polysaccharides are polyhydric alcohols that have received special interest for methylation purpose. A number of methylating agents have been employed to affix methyl group to molecule matrix via oxygen atom, and are, to cite but a few, methanol, methyl iodide, diazomethane, dimethyl sulfate, dimethyl carbonate, methyl triflate, tetramethylammonium salts and trimethyl phosphate. To the variety of existing OH-substrates and methylating agents, the myriad of organic and inorganic substances that play key roles in catalyzing the methylation reactions are added. The odd-even effect of acidic/basic character of a catalyst promotes the selectivity of methylation, hence the desired product. In most cases, every couple of catalyst/methylating agent brings about the O-methylation of the substrate through a unique mechanism.
Keywords: Alcohols, carboxylic acids, methylation, methylating agents, phenols, polysaccharides.
Graphical Abstract
Call for Papers in Thematic Issues
Catalytic C-H bond activation as a tool for functionalization of heterocycles
The major topic is the functionalization of heterocycles through catalyzed C-H bond activation. The strategies based on C-H activation not only provide straightforward formation of C-C or C-X bonds but, more importantly, allow for the avoidance of pre-functionalization of one or two of the cross-coupling partners. The beneficial impact of ...read more
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