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.