Cycloadditions of Pentalene and Azulene—A Facile Heptalene Synthesis

Abstract

The two lowest homologs of the annulene series, i. e. cyclobutadiene and benzene, are known to undergo either thermally or photochemically induced [2 +4] and [2 + 2] cycloadditions with reactive alkynes to give cyclobutene derivatives.