Heptalene Synthesis by Addition of Aryl Acetylenes to Azulenes

Aryl acetylenes bearing electron-withdrawing groups have been found that can add to azulenes and yield 1,2-substituted heptalenes. Theoretical studies of the reaction mechanism helped to design the candidate molecules that have then been tested in the synthetic work. New heptalenes are obtained by reacting methyl (4-nitrophenyl)propiolate with either 4,6,8-trimethylazulene or guaiazulene, as well as 3-(4-nitrophenyl)-2-propyn-1-ol with guaiazulene. This opens a new synthetic route to 1-aryl-substituted heptalenes.