Aromatic ring-opening metathesis.

Aromatic compounds are used across chemistry and materials science as a result of their stability, characteristic interactions, defined molecular shape and the numerous synthetic approaches for their synthesis by a diversity of cyclization reactions. In contrast, the cleavage of inert aromatic carbon-carbon bonds remained largely unfeasible due to the unfavourable energetics of disrupting aromaticity on ring opening. 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. Here, we report aromatic ring-opening metathesis (ArROM) for the cleavage of aromatic rings, including tetraphene, naphthalene, indole, benzofuran and phenanthrene by employing Schrock-Hoveyda molybdenum catalysts. The reactions for each of the ring systems 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.