Abstract: Dispiro [2.2. 2.2] deca-4, 9-diene (1) was prepared in five steps from diethyl succinate. This particular cyclopropylethylene exhibits a relatively large bathochromic shift of the absorption maximum (222 nm) in UV and a marked lowering of the ionization potential (7.23 eV) compared to cis-1, 2-dicyclopropylethylene (203.5 nrn in UV and IP 7.70 eV). The chemical shift of the olefinic protons, however, does not suggest the existence of cyclic ...