Dearomative Ring Expansion of Polycyclic Arenes

Benzocycloheptenes constitute a common structural motif embedded in many natural products and biologically active compounds. Herein, we report their concise preparation from non-activated polycyclic arenes using a two-step sequence involving dearomative [4+2]-cycloaddition with arenophile in combination with palladium-catalyzed cyclopropanation, followed by cycloreversion-initiated ring expansion. The described strategy provides a working alternative to the Buchner reaction, which is limited to monocyclic arenes. Overall, this methylene-insertion molecular editing approach enables rapid and direct conversion of simple (hetero)arenes into a range of substituted (aza)benzocycloheptatrienes, which can undergo a myriad of downstream functionalizations.

Automated summary

In this study, a concise method for the preparation of benzocycloheptenes from non-activated polycyclic arenes is reported, providing an alternative to the Buchner reaction. This methylene-insertion molecular editing approach enables rapid conversion of (hetero)arenes into substituted (aza)benzocycloheptatrienes, which can undergo various functionalizations downstream.