STABLE ARYLPALLADIUM IODIDES AND REACTIVE ARYLPALLADIUM TRIFLUOROMETHANESULFONATES IN THE INTRAMOLECULAR HECK REACTION

The reactions of 1-iodo-2-(3-butenyl)benzene and of two side-chain ether analogs with [1,1'-bis(diphenylphosphino)ferrocene](eta(2)-cyclooctatetraene)palladium gave the expected (eta(1)-aryl)-(eta(1)-iodo)palldium adducts, the 2-oxa-3-butenyl complex being characterized by X-ray crystallography. The alkene does not interact directly with palladium. Restricted rotation about the aryl-palladium bond was observed on the NMR time scale in all cases, since the methylene group(s) of the side chain were diastereotopic. The complexes were stable, but on treatment with silver trifluoromethanesulfonate in acetone at low temperature an unstable species was identified by H-1 and P-31 NMR in two of the three cases. Spectral observations were consistent with the formation and subsequent rearrangement of an intermediate along the pathway of an intramolecular Heck cyclisation with structure o-C6H4OC(CH3)(Pd[dppf]OTf).