Intermolecular [5+2] Annulation between 1-Indanones and Internal Alkynes by Rhodium-Catalyzed C-C Activation

Herein, we report a [5+2] cycloaddition between readily accessible 1-indanones and internal alkynes through Rh-catalyzed activation of less strained C-C bonds. The reaction is enabled by a strongly sigma-donating NHC ligand and a carefully modified temporary directing group. A wide range of functional groups is tolerated, and the method provides straightforward access to diverse benzocycloheptenones that are hard to access otherwise. DFT studies of the reaction mechanism imply the migration insertion as the turnover-limiting step and suggest beneficial pi-pi interactions in the transition states.

Automated summary

The study presents a [5+2] cycloaddition reaction catalyzed by Rh, which activates C-C bonds to enable the cyclization of 1-indanones and internal alkynes. The reaction demonstrates tolerance towards various functional groups and provides a direct route to diverse benzocycloheptenones. DFT studies suggest that migration insertion is the turnover-limiting step, with beneficial pi-pi interactions in the transition states.