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

Area of Science:

• Organic Chemistry
• Catalysis
• Materials Science

Background:

• Heterocyclic ketene aminals (HKAs) are versatile building blocks.
• Benzo[de]chromene derivatives possess interesting photophysical properties.
• Efficient synthesis of functionalized benzo[de]chromenes remains a challenge.

Purpose of the Study:

• To develop a novel cascade oxidative annulation reaction for benzo[de]chromene synthesis.
• To explore the catalytic system using [Cp*RhCl2]2 and Cu(OAc)2·H2O.
• To investigate the potential applications of the synthesized compounds.

Main Methods:

• Cascade oxidative annulation reaction of HKAs with internal alkynes.
• Rhodium(III)-catalyzed C-H activation and annulation.
• Copper(II)-mediated oxidation.

Main Results:

• Efficient synthesis of highly functionalized benzo[de]chromene derivatives in good to excellent yields.
• Sequential cleavage of C(sp2)-H/O-H and C(sp2)-H/C(sp2)-H bonds observed.
• Synthesized compounds exhibited intense solid-state fluorescence.
• Demonstrated concentration-dependent quenching in the presence of Fe3+.

Conclusions:

• A novel and efficient rhodium-catalyzed cascade reaction for benzo[de]chromene synthesis was established.
• The synthesized benzo[de]chromene derivatives possess valuable fluorescent properties.
• These compounds show promise for selective Fe3+ ion recognition.