- Acid fluorides and 1,1-difluoroethyl methyl ethers as new organic sources of fluoride for antimony pentachloride-catalyzed halogen-exchange reactions
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1,1-Difluoroethyl methyl ethers such as the commercial veterinary anesthetic methoxyflurane (2,2-dichoro-1,1-difluoroethyl methyl ether, 6) decompose in the presence of a catalytic amount of antimony pentachloride. The rate of decomposition is dependent upon the number and position of halogen atoms in the ether: a high degree of halogenation at the methyl group or at the 2-position of the ethyl group makes the ether less prone to decomposition. The decomposition products are acid fluorides and halogenated methanes. The fate of the antimony pentachloride is conversion to a fluorochloroantimony species which can be used in situ to selectively fluorinate a polychlorinated substrate. Thus, 1,2,2,2-tetrachloro-1-fluoroethyl methyl ether (1) is converted cleanly to the anesthetic compound 2,2,2-trichloro-1,1-difluoroethyl methyl ether (2) using 6 as the fluoride source, exploiting the difference in stability of 2 and 6 to the pentavalent antimony species. It is also demonstrated that the acid fluorides obtained from decomposition of the 1,1-difluoroethyl methyl ethers are fluoride sources for halex reactions.
- Ramig, Keith,Kudzma, Linas V.,Lessor, Ralph A.,Rozov, Leonid A.
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