Methoxy group
Inorganic chemistry,amethoxy groupis thefunctional groupconsisting of amethyl groupbound tooxygen.Thisalkoxy grouphas the formulaR−O−CH3.
On abenzene ring,theHammett equationclassifies a methoxy substituent at theparaposition as anelectron-donating group,but as anelectron-withdrawing groupif at themetaposition. At theorthoposition,steric effectsare likely to cause a significant alteration in the Hammett equation prediction which otherwise follows the same trend as that of theparaposition.
Occurrence
[edit]The simplest of methoxy compounds aremethanolanddimethyl ether.Other methoxy ethers includeanisoleandvanillin.Many metal alkoxides contain methoxy groups, such astetramethyl orthosilicateandtitanium methoxide.Esterswith a methoxy group can be referred to as methyl esters, and the —COOCH3substituent is called a methoxycarbonyl.[1]
Biosynthesis
[edit]In nature, methoxy groups are found on nucleosides that have been subjected to2′-O-methylation,for example in variations of the5′-cap structureknown as cap-1 and cap-2. They are also common substituents inO-methylated flavonoids,whose formation is catalyzed byO-methyltransferasesthat act onphenols,such ascatechol-O-methyl transferase(COMT). Many natural products in plants, such aslignins,are generated via catalysis bycaffeoyl-CoAO-methyltransferase.[2]
Methoxylation
[edit]Organic methoxides are often produced bymethylationof alkoxides.[3][4]Some aryl methoxides can be synthesized by metal-catalyzed methylation ofphenols,or by methoxylation ofaryl halides.[5][6]
References
[edit]- ^Streitwieser, Andrew (1992).Introduction to organic chemistry.Heathcock, Clayton H., Kosower, Edward M. (4th ed.). New York: Macmillan. pp.515.ISBN0024181706.OCLC24501305.
- ^Boerjan, Wout; Ralph, John; Baucher, Marie (2003). "Lignin Biosynthesis".Annu. Rev. Plant Biol.54(1): 519–46.doi:10.1146/annurev.arplant.54.031902.134938.PMID14503002.
- ^Scarrow, J. A.; Allen, C. F. H. (1933). "Methoxyacetonitrile".Org. Synth.13:56.doi:10.15227/orgsyn.013.0056.
- ^Cornella, Josep; Zarate, Cayetana; Martin, Ruben (2014)."Ni-catalyzed Reductive Cleavage of Methyl 3-Methoxy-2-Naphthoate".Org. Synth.91:260–272.doi:10.15227/orgsyn.091.0260.
- ^Cheung, Chi Wai; Buchwald, Stephen L. (2 August 2013)."Mild and General Palladium-Catalyzed Synthesis of Methyl Aryl Ethers Enabled by the Use of a Palladacycle Precatalyst".Organic Letters.15(15): 3998–4001.doi:10.1021/ol401796v.PMC3776604.PMID23883393.
- ^Tolnai, Gergely L.; Pethő, Bálint; Králl, Péter; Novák, Zoltán (13 January 2014). "Palladium-Catalyzed Methoxylation of Aromatic Chlorides with Borate Salts".Advanced Synthesis & Catalysis.356(1): 125–129.doi:10.1002/adsc.201300687.
