Hydroxyl-Directed Rh(III)-Catalyzed C-H Functionalization: Access to Benzo[de]chromenes

A cascade oxidative annulation reaction of heterocyclic ketene aminals (HKAs) with internal alkynes catalyzed by [Cp*RhCl2]2 and oxidized by Cu(OAc)2 center dot H2O was developed to efficiently synthesize highly functionalized benzo[de]chromene derivatives in good to excellent yields. The reaction proceeded by the sequential cleavage of C(sp2)-H/O-H and C(sp2)-H/ C(sp2)-H bonds. These multicomponent cascade reactions were highly regioselective. In addition, all of the benzo[de]chromene products exhibited intense fluorescence emission in the solid state, and they demonstrated concentration-dependent quenching in the presence of Fe3+, indicating that these compounds could be used in the recognition of Fe3+.

Automated summary

A cascade oxidative annulation reaction of heterocyclic ketene aminals (HKAs) with internal alkynes catalyzed by [Cp*RhCl2]2 and oxidized by Cu(OAc)2·H2O was developed for the efficient synthesis of highly functionalized benzo[de]chromene derivatives in good to excellent yields. The reaction proceeded through sequential cleavage of C(sp2)-H/O-H and C(sp2)-H/C(sp2)-H bonds, and exhibited high regioselectivity. Additionally, the resulting benzo[de]chromene products showed intense fluorescence emission in the solid state and concentration-dependent quenching in the presence of Fe3+, indicating their potential for Fe3+ recognition.