Synthetic approaches toward biologically important 1,4-benzothiazine derivatives: A review

One of the main goals of organic chemistry is development of novel reaction protocols. 1,4-benzothiazine and its derivatives play a key role in the pharmaceutical industry. Consequently, there have been various pharmacological effects of 1,4-benzothiazine and its derivatives, such as anti-hypertensive, anti-HIV, anti-inflammatory, antimicrobial, anti-rheumatic, ATP-sensitive potassium channel opener, cardiovascular, cytotoxic, immunomodulator, neuroprotective, antioxidant, antimalarial, and aldose reductase inhibitor, etc. Apart from the above, the 1,4-benzothiazine moiety constitutes the skeleton of numerous naturally occurring pigments, dyestuffs, and is also available in different types of natural product skeletons, including melanin, pheomelanin, etc. Synthetic chemists have identified numerous methods for synthesizing different moieties of 1,4-benzothiazine, which demonstrate significant pharmacological activity through multiple mechanisms. This review article aims to summarize various synthetic strategies related to bioactive heterocycles of 1,4-benzothiazine derivatives in an organized manner.