5-Fluoroisatin (CAS number 443-69-6), a fluorinated indole derivative, contains a fluorine (5-position) and two carbonyls (2,3-positions). The carbonyl group at 3-position reacts with amines or hydrazines for imines or hydrazones that function as Schiff bases. The Schiff base based on 5-fluoroisatin coordinates to cobalt, yielding Co-isatin complexes. The metal complexes catalyze oxidative condensation reaction in air by generating singlet oxygen under sunlight. A macromolecule with donor-acceptor-donor system can be synthesized with 5-fluoroisatin and a diamine building block. The OLED device based on the macromolecule shows external quantum efficiency of 0.0515% with emission of 630 to 700 nm.
The 5-membered ring of 5-fluoroisatin can be expanded, forming isatoic anhydride through Baeyer-Villiger oxidation with mCPBA (meta-chloroperoxybenzoic acid). 5-Fluoroisatin can also be reshaped to a quinoline under Pfitzinger reaction, providing a platform for post-modification of the isatin derivatives.