Aryltrifluoromethyl ketones

Aryltrifluoromethyl ketones are prepared by reaction of an aryl-lithium with a,a,a-trifluoro-N,N-dimethylacetamide. 2-Acyloxypyridines and N-acylimidazoles, " in conjunction with trifluoroacetic acid, acylate arenes in good yield without the need for a classical Friedel-Crafts catalyst or a preformed mixed anhydride. However, imidazole in trifluoroacetic anhydride is reported to form 2-aryl-Af,JV -diacyl-4-imidazolines with arenes reactive towards electrophilic attack. These adducts are readily hydrolysed by sodium hydroxide to the corresponding aldehyde [equation (14)]. This sequence may offer advantages over the Vilsmeier method of formylation, in that the aldehyde is introduced in a protected form. 

The bromoesters (56) are converted to cycloalkanes (57) in reasonable yield by the addition of LDA, (Hetero)aryltrifluoromethyl ketones are synthesized in variable yield by the reaction of an appropriate aryl-lithium with 1,1,1-trifluorodimethylacetamide. ... 

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