Trifluoromethoxy arenes

Perfluoroalkoxy groups and, especially, the trifluoromethoxy group, are commonly used as structural elements in pharmaceuticals (Section 4.5) and organic materials (Section 4.4). Aromatic and aliphatic perfluoroalkoxy groups are conveniently accessible via fluorodesulfuration chemistry (see also Section 2.1.5.4). Nevertheless, the technically important trifluoromethoxy arenes, in particular, are produced on a larger scale by a different method, based on chlorine-fluorine exchange with hydrofluoric acid [17] (Scheme 2.172). 

Scheme 2.172 Technical syntheses of trifluoromethoxy arenes via the trichloro-methoxy derivative or directly from the phenol [17] (X denotes 3- or 4-NO2, 4-CI, 2,4-Cl2, 3-CF3, 4-NH2, 2-F, 4-OH).

The methods that are known for introducing trifluoromethoxy groups into arenes are generally not effective. An interesting onc-pot O-alkylation of phenols followed by halogen exchange to form trifluoromethyl ethers 6 has been described227 (see also Houben-Weyl, Vol. E4, pp 626-627). 

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