Aromatic Ring-Opening Metathesis

Aromatic compounds have found paramount utility on account of their stability, characteristic interactions, defined molecular shape and the numerous synthetic approaches for their synthesis, which include a diversity of cyclization reactions. In contrast, the cleavage of the inert aromatic carbon-carbon bonds remained largely unfeasible due to the unfavourable energetics of disrupting aromaticity in the formation of ring-opened products. For non- aromatic structures, alkene metathesis catalysed by transition metal alkylidenes is established as one of the most versatile carbon-carbon bond-forming and breaking reactions. However, despite remarkable advancements, strategies to open aromatic compounds by metathesis remained elusive. Herein we disclose the feasibility of aromatic ring-opening metathesis (ArROM) to cleave a diversity of aromatic rings, including tetraphene, naphthalene, indole, benzofuran and phenanthrenes by employing Schrock- Hoveyda molybdenum alkylidene catalysts. The reactions for each of the ring systems thereby proceed through unique alkylidene intermediates. We further show the possibility for stereoselective aromatic ring-opening metathesis with exquisite catalyst control over the configuration of atropisomers. Aromatic ring-opening metathesis is therefore a viable and efficient approach to catalytically transform and interconvert various aromatics without the requirement for any reagents or photoexcitation.