Studies on the oxidation addition reaction of 1,1-dibromo-1-alkenes, alpha-dehalopalladation, and the intramolecular Bis(carbopalladation) reaction of alkenes. An efficient entry to fused bicycles

Synthesis of 1,1-dihalo-1-alkenes by the conventional alkylation methods is presented. The oxidative addition reactions of 1,1-dibromo-2,2-diphenylethene or 1,1-dibromo-2-phenylpropene with a stoichiometric amount of Pd(PPh3)4 afforded 1,2-diphenylacetylene and 1-phenylpropyne, respectively indicating that alpha-dehalopallation reaction occurred to afford vinylic carbene intermediates.