Synthesis of a highly aromatic and planar dehydro [10]annulene derivative

Aromaticity is a phenomenon that is linked to the improved stability of organic compounds. Its occurrence is predicted by Hückel’s rule, which states that an aromatic compound must be flat, fully conjugated and have (4n + 2) π electrons. The most encountered aromatic structure is the benzenoid ring, which is observed in a wide variety of pharmaceuticals and organic materials. Expanded monocyclic structures are also of substantial interest as they would allow one to experimentally investigate the relationships between aromaticity, stability, reactivity and ring size. However, larger rings such as [10]annulene are often non-planar and non-aromatic due to angle strain present in their planar conformation. Inspired by earlier computational work, we show here that the presence of both a fused cyclopropane and an internal alkyne in a [10]annulene framework provides a planar and highly aromatic structure. The resulting dehydro[10]annulene is bench stable and can be stored for extended periods of time.