Greener Approaches Towards 1,4-Benzothiazine Synthesis: Recent Updates and Outlook

Heterocyclic moieties are ubiquitous in nature and the exploration of heterocyclic chemistry goes centuries back, which have coalesced into the invention of greener methodologies towards the synthesis of heterocycles of potential uses. Benzothiazine is an important class of heterocyclic molecule, in which a benzene ring is fused with a six-member N, S containing ring. Amongst the three possible isomers, 1,4-benzothiazines show a wide spectrum of pharmaceutical and biological activities like anti-inflammatory, anti-rheumatic, antihypertensive, andantipathogenic roles. In search of greener protocols,metal-free catalysts, and environmentally benign reaction conditions, a lot have been unboxed to date, and many other dimensions remain yet to be deciphered. This minireview is an attempt to classify various sustainable protocols for the synthesis of 1,4-benzothiazine scaffolds over the last decade based on the reacting components and pathways, along with the consideration of plausible mechanistic insights and critical analysis.