PALLADIUM-CATALYZED ANNULATION OF VINYLIC CYCLOPROPANES AND CYCLOBUTANES

Aryl iodides substituted in the ortho position by OH, CH2OH, NH2, NHTs and CH(CO(2)Et)(2) groups react with vinylic cyclopropanes and cyclob utanes in the presence of a palladium catalyst and an appropriate base to afford good yields of heterocycles and carbocycles. The annulation products apparently arise by (1) palladium(0) formation and insertion into the carbon-iodine bond of the aryl iodide to generate an arylpal ladium intermediate,(2) arylpalladium addition across the carbon-carbo n double bond of the alkene, (3) ring-opening of the cyclopropane or c yclobutane by carbon-palladium beta elimination, (4) rearrangement of the resulting unsaturated alkylpalladium compound to a pi-allylpalladi um compound by a series of reversible palladium hydride beta eliminati on and readdition steps, (5) anion formation by removal of a proton fr om the functional group present on the arene, and (6) nucleophilic sub stitution of the palladium by the resulting anion.