Pd–benzothiazole carbene catalysed carbonylation of aryl halides in ionic liquids

The carbonylations of aryl halides with the Pd–carbene catalyst 1 were studied both in molecular solvents and in ionic liquids (ILs). Among the ILs, tetrabutylammonium bromide (TBAB) was found to give better results. Under these conditions the catalyst, when recovered and reused, did not show a significant decrease of activity. The role of TBAB on the catalyst stability is discussed.