NEW SYNTHETIC APPLICATIONS OF WATER-SOLUBLE ACETATE PD TPPTS CATALYSTGENERATED IN-SITU - EVIDENCE FOR A TRUE PD(0) SPECIES INTERMEDIATE/

Studies on the sp-sp intermolecular coupling reactions with the pallad ium water-soluble catalyst prepared in situ from palladium(II) acetate and sulfonated triphenylphosphine P(C6H4-m-SO3Na)(3) (TPPTS) in a hom ogeneous acetonitrile-water system, without Cu(I) promotor, afford diy nes with moderate yields (45-65%). Under the same conditions, the sp(2 )-sp coupling of 2-iodophenols or 2-iodoanilines and terminal alkynes followed by intramolecular cyclization gives indolic and furanic produ cts in good yields (60-99%). Under these aqueous conditions, an effici ent and short synthesis of eutypine illustrated the synthetic potentia lity of the coupling. Furthermore, through a series of kinetic and P-3 1 NMR experiments, we have demonstrated that a mixture of Pd(OAc)(2) a nd TPPTS affords spontaneously a palladium(0) complex, through formati on of bivalent complex Pd(OAc)(2)-(TPPTS)(2). A detailed mechanism of the reaction has been investigated thoroughly and the pertinent rate c onstants measured. The resulting palladium(0) complex reacts with phen yl iodide via an oxidative addition. This complex is considerably less reactive than the corresponding complex generated from PPh(3), probab ly due to steric effects.