Monodentate Transient Directing Group Enabled Distal C─H Bond Functionalization in Ferrocenecarboxaldehyde

Heteroannular palladium migration on stacked molecules is one of the keys for achieving distal C-H activation by avoiding the template design. However, the possibility of migration is only realized when a relatively stable palladacycle is formed at a distal position with the aid of a transient directing group. Herein, we have revealed that heteroannular palladium migration facilitated by a monodentate transient directing group, along with an additional ligand, can help to fine-tune the desired bite angle for palladium migration. The developed reaction effectively demonstrates 23 examples of distal heteroannular C-H functionalization of ferrocenecarboxaldehydes, a process that has been less extensively studied compared to the homoannular cyclopentadienyl (Cp) ring C-H activation. Furthermore, the control experiments have been performed to understand monodentate transient directing group (TDG)-enabled heteroannular palladium migration, favored by the monodentate TDG and ligand.