Single-electron entrapment of [8]annulyne, biannulenylenes, and an annulenoannulene

The low-temperature (-100 degrees C) dehydrohalogenation of bromocyclooctatetraene followed by immediate electron-transfer yields a stable solution of the 8]annulyne anion radical. If the unstable 8]annulyne is reacted with itself, cyclobutadiene, or benzyne, the respective bi-8]annulenylene, 6]annuleno8]annulene, or 6]-8]annulenylene can be trapped as their anion radicals via one-electron transfer. These condensation products were all obtained from simple 2 + 2] cycloaddition reactions. B3LYP/6-31G geometry optimizations were carried out, and the calculated spin densities were compared to the EPR spectral results obtained for the anion radicals of 6]annuleno8]annulene, 8]annulyne, bi8]annulenylene, and 6]-8]annulenylene, and excellent agreement has been realized. This simple "one-pot" approach should be applicable to a wide range of such systems.