Replacement of Cl by CF3 in Aromatics and Heteroaromatics

The palladium–catalysed trifluoromethylation of aryl chlorides has recently been published ( E J Cho et al, Science, 2010, 328, 1679-1681) by the group of Buchwald at MIT.  Wheaeas there have been previous publications on replacement of aryl iodides with trifluoromethyl, this is the first general method.  The procedure is catalysed by various palladium complexes and uses Triethylsilyltrifluoromethane as reagent in dioxane at 120 ^oC for 6-20 hours in the presence of dry (spray-dried) KF.  The process is compatible with a wide range of functional groups including both electron-rich and electron-poor (esters, amides, nitriles, acetals, nitro, but not ketones and aldehyde, nor unprotected amines and phenols).  In addition to phenyl rings, indoles, carbazoles, quinolines and benzofurans could be used.  Yields are in the range 70-94%