Nitrogen sulphur containing heterocycles have specific properties due to which they can be used as a potential material in a different type of industries such as medicinal/pharmaceutical, paint, packing and textile, required for various chemical, physical operations and their use as products. Especially dyes, paint, agrochemicals, medicine, etc. make them more significant. In present days, Nitrogen-Sulfur heterocycles are repeatedly attracting the interest of chemists due to their exceptional bioactive behavior. The present study is a review of the work carried out by a chemist in the discovery of new, effective, medicinally important heterocyclic compounds. The present review basically focused on nitrogen-sulfur heterocycles of potential therapeutic interest, especially with thiazole, thiazine, pyrimidine, morpholine and piperazine heterosystems, benzothiazines, pyrazole-benzothiazines, morpholine-benzothiazines, piperazine-benzothiazines and pyrimidine-benzothiazoles, mainly due to their unique structural features, which enable them to exhibit a number of biological and pharmacological activities. Due to a novel mode of action, a broad spectrum of activity, lesser toxicity towards mammalian cells, and suitable profiles towards humans have triggered the use of Nitrogen Sulphur containing heterocycles in designing and synthesizing their derivatives with better properties. The overall objective of the review is to discuss the importance of novel biodynamic structurally diverse heterocycles of potential therapeutic interest: pyrimidine, morpholine, piperazine, pyrozole, benothiazoles, pyrimidobenzothiazoles, 4H-1,4-benzothiazines, pyrazolyl-benzothiazines, morpholinyl-benzothiazines and piperazinylbenzothiazines in order to have access to important commercial molecules for the search of better future.

N-bridged heterocycles, 2-methyl-4H-pyrimido[2,1-b]benzothiazol-4-ones, have been synthesized in quantitative yield by the reaction of 2-aminobenzothiazoles with ethylacetoacetate in the presence of polyphosphoric acid involving dehydrative condensation followed by cyclization. The possibility of the formation of 4-methyl-2H-pyrimido[2,1-b]benzothiazol-2-ones has been excluded on the basis of spectral studies.

4-Phenyl-2H-pyrimido[2,1-b]benzothiazol-2-ones have been synthesized in quantitative yields by the reaction of 2-aminobenzothiazoles with alkynoic acid. The antimicrobial activity of the synthesized compounds was tested against bacterial species, Bacillus coagulans, Bacillus subtilis, Staphylococcus aureus, and Pseudomonas aeruginosa. The synthesized compounds have shown significant activity against microorganisms which can be correlated with the fused heterocyclic systems.

In this work, 4H-1,4-benzothiazines were synthesized by an efficient synthetic method in a single step involving heterocyclization of substituted 2-aminobenzenethiols with b-ketoester. The structures of the synthesized compounds were confirmed by their analytical and spectral data. The synthesized compounds were evaluated for their antimicrobial activity against bacterial species; E. coli and Bacillus cereus. The synthesized compounds showed significant activity against microorganisms, which can be correlated with the privileged heterocyclic structural scaffolds.

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: Aziridines are the saturated three-membered cyclic amines that constitute an important group of synthetic intermediates. These could act as a precursor for diverse organic compounds owing to the reactivity due to the ring strain associated with them. The outstanding property of aziridines is their high reactivity towards various nucleophilic and electrophilic reagents to acquire more stable ring-opened or ring-expanded amines that could be obtained from the release of strain energy intrinsic in a small ring. As such, aziridines could be used in the synthesis of 4-7 membered heterocycles of biological and industrial significance, such as azetidines, imidazoles, thiazoles, pyrazines, pyrimidines, benzothiazines, benzodiazepines, etc. Earlier synthesis of aziridines was considered a laborious task due to their instability. However, various synthetic approaches leading to the formation of aziridines are now available in the literature. Recently, green, cost-effective and approaches based on simpler work-up for these reactions have attracted researcher's attention. This review article deals with synthetic routes of aziridines and aziridine applications in organic synthesis.

Indoles constitute a widely occurring functional group in nature and are present in an extensive number of bioactive natural products and medicinally important compounds. As a result, exponential increases in the development of novel methods for the formation of indole core along with site-specific indoles have been established. Conventional methods for the synthesis of indoles are getting replaced with green methods involving ionic liquids, water as a solvent, solid acid catalyst, microwave irradiation and the use of nanoparticles under solvent-free conditions. In addition, there are immense applications of the substituted indoles in diverse fields.

At present, heterocyclic compounds and their derived forms have become strong reflection in medicinal research field because of their positive pharmacological and biological properties. Heterocycles are prosperous in nature and have expanded additional importance because their structural subunits are established in many natural products such as antibiotics, vitamins, and hormones. Thiazine moieties present in compounds have multiplicity of medicinal activities such as antihypertensive, antitumor, antimicrobial, antibacterial, anticoagulant, antifungal, anticancer, and antiviral. This review article mainly based on thiazines and their derivatives with potential antimicrobial activities that are at this time in advancement.