By extension , any pentadienyl cation regardless of its origin is capable of undergoing a Nazarov cyclization . It have been a large number of examples published where the requisite cation is arrived at by a variety of rearrangements . One such example involves the silver catalyzed cationic ring opening of allylic dichloro cylopropanes . The silver salt facilitates loss of chloride via precipitation of insoluble silver chloride .