Rare-Earth Metal-Enabled Ring-Opening Metathesis of Benzene

Abstract

Activation and transformation of inert C–C bonds within arenes are challenging and important topics in synthetic chemistry. While there have been some reports on the activation of C–C bonds in arene rings, the realm of metathesis reactions involving arene C–C bonds remains unexplored. Here, we report a rare-earth metal-enabled intramolecular metathesis reaction of one benzene C–C bond and another C–C single bond, assisted by the high reactivity and unique synergistic effect of rare-earth metallacycles. Mechanistic studies disclose an intriguing pathway that forms a fused tricyclic intermediate bearing a 4-membered ring through stepwise [2 + 2] cycloaddition, followed by stepwise [2 + 2] cycloreversion. The distinct reaction discovered here extends the reactivity of arenes and is expected to inspire the development of aromatic ring-opening metathesis reactions.