Acetoxy group
In organic chemistry, the acetoxy group (abbr. AcO or OAc; IUPAC name: acetyloxy[1]), is a functional group with the formula −OCOCH3 and the structure −O−C(=O)−CH3. As the -oxy suffix implies, it differs from the acetyl group (−C(=O)−CH3) by the presence of an additional oxygen atom. The name acetoxy is the short form of acetyl-oxy.
Functionality
[edit]An acetoxy group may be used as a protection for an alcohol functionality in a synthetic route although the protecting group itself is called an acetyl group.
Alcohol protection
[edit]There are several options of introducing an acetoxy functionality in a molecule from an alcohol (in effect protecting the alcohol by acetylation):
- Acetyl halide, such as acetyl chloride in the presence of a base like triethylamine[2]
- Activated ester form of acetic acid, such as a N-hydroxysuccinimide ester, although this is not advisable due to higher costs and difficulties.[3]
- Acetic anhydride in the presence of base with a catalyst such as pyridine with a bit of DMAP added.[4]
An alcohol is not a particularly strong nucleophile and, when present, more powerful nucleophiles like amines will react with the above-mentioned reagents in preference to the alcohol.[5]
Alcohol deprotection
[edit]For deprotection (regeneration of the alcohol)
- Aqueous base (pH >9)[6]
- Aqueous acid (pH <2), may have to be heated[7]
- Anhydrous base such as sodium methoxide in methanol. Very useful when a methyl ester of a carboxylic acid is also present in the molecule, as it will not hydrolyze it like an aqueous base would. (Same also holds with an ethoxide in ethanol with ethyl esters)[8]
See also
[edit]References
[edit]- ^ Nomenclature of Organic Chemistry : IUPAC Recommendations and Preferred Names 2013 (Blue Book). Cambridge: The Royal Society of Chemistry. 2014. p. 805. doi:10.1039/9781849733069-00648. ISBN 978-0-85404-182-4.
The systematic name 'acetyloxy' is preferred to the contracted name 'acetoxy' that may be used in general nomenclature.
- ^ Ouellette, Robert J.; Rawn, J. David (2019). "22 - Carboxylic Acid Derivatives". Organic Chemistry (2nd ed.). pp. 665–710. doi:10.1016/C2016-0-04004-4. ISBN 978-0-12-812838-1. Retrieved 2024-05-08.
- ^ Cali, Khasim; Tuccori, Elena; Persaud, Krishna C. (2020-08-19). "Chapter Eighteen - Gravimetric biosensors". In Pelosi, Paolo; Knoll, Wolfgang (eds.). Odorant Binding and Chemosensory Proteins. Methods in Enzymology. Vol. 642. pp. 435–468. doi:10.1016/bs.mie.2020.05.010. ISSN 0076-6879. Retrieved 2024-05-08.
{{cite book}}: CS1 maint: date and year (link) - ^ Nishihara, Shoko; Angata, Kiyohiko; Aoki-Kinoshita, Kiyoko F.; Hirabayashi, Jun, eds. (2021). Glycoscience Protocols (GlycoPODv2). Saitama (JP): Japan Consortium for Glycobiology and Glycotechnology. PMID 37590565.
- ^ Wall, Leo A.; Pummer, Walter J.; Fearn, James E.; Antonucci, Joseph M. (1963-09-01). "Reactions of polyfluorobenzenes with nucleophilic reagents" (PDF). Journal of Research of the National Institute of Standards and Technology. 67A (5): 481. doi:10.6028/jres.067A.050. ISSN 0022-4332. PMC 5319811. PMID 31580596.
- ^ Matyjaszewski, Krzysztof; Möller, Martin (2012). "8.03 - Photoresists and Advanced Patterning". Polymer Science: A Comprehensive Reference. Vol. 8. Elsevier Science. pp. 37–76. doi:10.1016/B978-0-444-53349-4.00201-6. ISBN 978-0-08-087862-1.
- ^ Howard, Kyle T.; Chisholm, John D. (2016-01-02). "Preparation and Applications of 4-Methoxybenzyl Esters in Organic Synthesis". Organic Preparations and Procedures International. 48 (1): 1–36. doi:10.1080/00304948.2016.1127096. ISSN 0030-4948. PMC 4989276. PMID 27546912.
- ^ Banyikwa, Andrew Toyi; Miller, Stephen E.; Krebs, Richard A.; Xiao, Yuewu; Carney, Jeffrey M.; Braiman, Mark S. (2017-10-31). "Anhydrous Monoalkylguanidines in Aprotic and Nonpolar Solvents: Models for Deprotonated Arginine Side Chains in Membrane Environments". ACS Omega. 2 (10): 7239–7252. doi:10.1021/acsomega.7b00281. ISSN 2470-1343. PMC 6645140. PMID 31457300.