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.