Regioselective substitution of phenols with trifluoroacetaldehyde ethyl hemiacetal

Phenol did not react directly with trifluoroacetaldehyde ethyl hemiacetal. In the presence of catalytic amounts of anhydrous potassium carbonate, however, the reaction readily occurred. The p-substituted product 4-(2,2,2-trifluoro-1-hydroxyethyl)phenol predominated. In contrast, the reaction catalyzed by zinc halide predominantly produced the o-substituted product. Corresponding reactions of several phenols were studied under the same catalytic conditions.