Chitosan@Tannic Acid-Supported Fe 3 O 4 Magnetic Bionanocomposite as Green and Recyclable Catalyst for the Synthesis of Benzo[ g ]thiazolo[3,2- a ]quinolones Based on Nitroketene N , S -Acetal

To prepare an efficient magnetic bionanocomposite and to protect ferrite nanoparticles from oxidation and aggregation, the prepared Fe 3 O 4 was supported by chitosan and tannic acid as the first and second coating layers respectively, and the presence of empty orbitals of Fe 3 O 4 and multiple phenol groups on the surface of bionanocomposite leads to the activation of raw materials in acid catalyst reactions. Fe 3 O 4 @chitosan-tannic acid was fully characterized by FT-IR, TGA, EDX, VSM, FESEM, and TEM. To examine the catalytic activity, it was applied for the first time for the synthesis of a series of 4-nitro-5-phenyl-1,2-dihydro-5 H -benzo[ g ]thiazolo[3,2- a ]quinolines-6,11-dione with potent antitumor activity from β -nitro-thiazolidine, 2-hydroxy-1,4-naphthoquinone and various aromatic aldehydes via an aza-ene reaction followed by intramolecular cyclization. Some of this procedure’s prominent advantages include obtaining the products in short reaction times with high yields, the environmentally benign character of the catalyst, and the facility of catalyst separation and recycling of it due to the existence of the superparamagnetic core. Graphical Abstract