Silver-Catalyzed Decarboxylative Trifluoromethylation of Aliphatic Carboxylic Acids

The
silver-catalyzed decarboxylative trifluoromethylation of aliphatic
carboxylic acids is described. With AgNO3 as the catalyst
and K2S2O8 as the oxidant, the reactions
of aliphatic carboxylic acids with (bpy)­Cu­(CF3)3 (bpy = 2,2′-bipyridine) and ZnMe2 in aqueous acetonitrile
at 40 °C afford the corresponding decarboxylative trifluoromethylation
products in good yield. The protocol is applicable to various primary
and secondary alkyl carboxylic acids and exhibits wide functional
group compatibility. Mechanistic studies reveal the intermediacy of –Cu­(CF3)3Me, which undergoes reductive
elimination and subsequent oxidation to give Cu­(CF3)2 as the active species responsible for the trifluoromethylation
of alkyl radicals.