Three-Component Synthesis of Fluorescent 1,4-Benzothiazin-2-ones Through Thiol-Free Iodine-Catalyzed Cyclization

A convergent synthesis of 2H-benzo[b][1,4]thiazin-2-one was achieved via iodine-catalyzed three-component reaction. This strategy involves the formation of two new C-S bonds and a C-N bond from the readily available precursors - aryl methyl ketones, p-anisidine, and elemental sulfur to generate the desired heterocycle in moderate to good yields. As the synthesized benzothiazine-2-ones are fluorescent under UV light, photophysical properties like solid-state emission, solvatochromism, Aggregation Induced Emission (AIE), and the relative quantum yields of the compounds were measured which proves them to be a potential candidate for the development of optoelectronic devices. A Convergent, thiol- and metal-free strategy for the synthesis of benzothiazine-2-one derivatives were developed from readily available precursors such as aryl ketone, aromatic amine and elemental sulfur. This reaction involves the formation of two new C-S bonds and one new C-N bond in single step employing environmentally benign iodine as the catalyst. Photophysical properties like quantum yield, solid-state emission, solvatochromism, Aggregation Induced Emission were also explored. Moreover, HOMO-LUMO gap was calculated for few compounds which suggests the possibility of Intramolecular charge transfer. image