Ring‐Expanding Rearrangement of Benzo‐Fused Tris‐Cycloheptenylenes towards Nonplanar Polycyclic Aromatic Hydrocarbons

Abstract

AbstractA strongly twisted benzo‐fused tris‐cycloheptenylene, containing three dibenzosuberenone units fused to a common benzene ring, was subjected to Ramirez olefination and subsequent palladium‐catalyzed Suzuki‐Miyaura cross‐coupling with 4‐substituted phenylboronic acids. The high steric demand within the overcrowded, benzene‐rich benzo‐fused tris‐cycloheptenylenes enforced an unprecedented 1,2‐rearrangement upon π‐extension during the Suzuki coupling reaction. According to crystal structure analysis, the resulting negatively curved polycyclic aromatic hydrocarbons consist of two heptagons and one octagon surrounding a central benzene ring as a result of strain release. In the solid state, the materials exhibit a blue to blue‐green fluorescence with increased quantum yields and a hypsochromic shift of the emission maxima compared to their respective solutions.