Singly and Doubly Twisted [36]Annulenes: Synthesis and Calculations

A cyclophane with a [36]annulene periphery, including four anthrylene and two phenylene units, was synthesized in a four-step sequence using a McMurry cyclization. Upon crystallization from different solvents, four different conformations were determined by X-ray structure analysis. Two conformations exhibit a double twist (Huckel topology) and two structures include a single twist (Mains topology). By using DFT calculations a conformation with a triple twist (Mobius) was located. However, our calculations and the NMR spectroscopy data do not provide evidence for aromaticity (for Mobius structures) or antiaromaticity (for Huckel structures).