7,7′‐Bi(dispiro[2.0.2.l]heptylidene)—the Perspirocyclopropanated Bicyclopropylidene

Abstract

That intermediate cyclopropyl cations with two α-spirocyclopropane groups can undergo reaction without ring opening has been proven. The reaction of title compound 1 with electrophiles like HBr and Br2 leads to addition to the central double bonds and not to rearrangements. Compound 1 was prepared in three steps from 7-cyclopropylidenedispiro-[2.0.2.l]heptane (2). Compared to other bicyciopropylidenes the target molecule shows an unusually low → ionization energy of 8.20 eV.