Methoxymethyl ether
In organic chemistry, a methoxymethyl ether is a functional group with the formula {{chem2|ROCH2OCH3}}, abbreviated MOM. The group is usually derived from chloromethyl methyl ether, a kind of chloroalkyl ether which is, like its congeners, often employed in organic synthesis to protect alcohols.{{cite book|last1=Wuts|first1=P. G. M.|last2=Greene, T.W.|year=2006|title=Greene's Protective Groups in Organic Synthesis|doi=10.1002/0470053488|isbn= 9780470053485|publisher=J. Wiley|location=NY}}{{Cite journal|last1=Enders|first1=Dieter|last2=Geibel|first2=Gunter|last3=Osborne|first3=Simon|date=2000-04-17|title=Diastereo- and Enantioselective Total Synthesis of Stigmatellin A|journal=Chemistry – A European Journal|language=en|volume=6|issue=8|pages=1302–1309|doi=10.1002/(SICI)1521-3765(20000417)6:8<1302::AID-CHEM1302>3.0.CO;2-J|pmid=10840951 }} Closely related to MOM ethers are methoxyethoxymethoxy (MEM) protecting groups, introduced using 2-methoxyethoxymethyl chloride. The MEM protecting groups are more easily installed and more easily removed.
Protection
Typically, the alcohol to be protected is deprotonated with a non-nucleophilic base such as N,N-diisopropylethylamine (DIPEA) in dichloromethane followed by addition of the chloromethyl reagent.{{cite journal |doi=10.15227/orgsyn.096.0312|title=Preparation of (R)-3-(3,5-Bistrifluoromethylphenyl)-1,1'-bi-2-naphthol |year=2019 |last1=Kobayashi |first1=Yusuke | first2=Atsushi|last2=Matsuda |first3=Tomoya |last3=Ushimaru |first4=Toshiro |last4=Haradaournal=Organic Syntheses |journal=Organic Syntheses |volume=96 |pages=312–332 |doi-access=free }}<
Although not relevant to protecting groups, MOM groups are installed by reaction of chloromethyl ethers with methoxide{{cite journal |doi=10.15227/orgsyn.075.0177|title=Selective Protection of 1,3-Diols at the More Hindered Hydroxy Group: 3-(Methoxymethoxy)-1-Butanol |journal=Organic Syntheses |year=1998 |volume=75 |page=177|author=William F. Bailey, Matthew W. Carson, Lyn M. J. Zarcone }} and by the acid-catalyzed reaction of alcohols with dimethoxymethane.{{cite journal |doi=10.15227/orgsyn.073.0094|title=Regio- AND Stereoselective Intramolecular Hydrosilylation of a-Hydroxy Enol Ethers: 2,3-syn-2-Methoxymethoxy-1,3-nonanediol |journal=Organic Syntheses |year=1996 |volume=73 |page=94|author=Kohei Tamao, Yoshiki Nakagawa, and Yoshihiko Ito }}
Deprotection
The MOM and the MEM protecting groups can be cleaved with a range of Lewis and Bronsted acids.{{Cite journal|last1=Amano|first1=Seiji|last2=Takemura|first2=Noriaki|last3=Ohtsuka|first3=Masami|last4=Ogawa|first4=Seiichiro|last5=Chida|first5=Noritaka|date=1999-03-26|title=Total synthesis of paniculide A from d-glucose|journal=Tetrahedron|volume=55|issue=13|pages=3855–3870|doi=10.1016/S0040-4020(99)00096-4}}
Safety
Chloromethyl methyl ether and chloromethoxyethoxymethane, like other chloroalkyl ethers, are strong alkylating agents with attendant dangers. These compounds are human carcinogen.[https://ntp.niehs.nih.gov/ntp/roc/content/profiles/bis_chloromethyletherandtechnical-gradechloromethylmethylether.pdf Bis(chloromethyl) Ether and Technical-Grade Chloromethyl Methyl Ether CAS Nos. 542-88-1 and 107-30-2], Report on carcinogens, Eleventh edition
References
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