Molten salts (ionic liquids) to improve the activity, selectivity and stability of the palladium catalysed Trost-Tsuji C-C coupling in biphasic media

The Trost-Tsuji C-C coupling between ethyl cinnamyl carbonate and ethyl acetoacetate catalysed by a water soluble Pd/TPPTS catalyst (TPPTS = triphenylphosphine trisulphonate, sodium salt) and possible side reactions have been investigated in several biphasic media at 60-80 degrees C. The use of the ionic liquid 1-butyl-3-methylimidazolium chloride as the catalytic layer brings definitive advantages over an aqueous catalytic phase: Palladium chloride may be used as the catalyst precursor, the solubility of the organic reagents is much higher which leads to faster reaction rates, the formation of cinnamyl alcohol is suppressed and common organic layers such as alkanes can be used with no noticeable catalyst deactivation. The yields in the C-C product up to 90% with TOF number, of 23 h(-1) may, thus, be achieved. (C) 1999 Elsevier Science B.V. All rights reserved.