The ring expansion synthesis of cycloundacene from cyclooctene Is described» Addition of dlbromocarbene, elimination/rearrangement by n-BuLl to an aliene, and Na/NH reduction results In the formation of the next larger cycloolefin. The synthesis and rearrangements of the title compounds n-7-1 are discussed. Compound 7 rearranges exclusively to 3-methylene-1,4-cyclononadiene. Compounds 9 & 1 rearrange to 4-methylenebicyolo. Compound 8 rearranges to a 1-2 mixture of 3-methylene-l-4-cyclodecadiene and 4-methylenebicyclo deca-2-ene respectively. This is the slowest material to rearrange requiring sixteen hours at xylene reflux whereas the others rearrange within several hours in toluene reflux.