Synthesis of a Dicyclopenta[a, e]pentalene by [6 + 2]-Cycloaddition of 1,3-Di-tert-butyl-5-vinylidenecyclopentadiene and Consecutive 8π-Electrocyclic Reaction

The first non-benzenoid, linearly annelated, tetracyclic system with [4n + 2]-perimeter and [4n]-partial structures was obtained by dimerization of the allene derivative 1 via [6 + 2]-cycloaddition. Subsequent 8π-electrocyclization yielded a tetraquinane, which could be dehydrogenated to the title compound 2