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In this article, we applied ultrasonic irradiation as an ecofriendly, green, efficient approach for the synthesis of a new 1,3-thiazoles and 1,3,4-thiadiazines under solvent-free conditions. Thus, thiocarbohydrazide condenses with N-(thiazol-2-yl)acetamide (2) in different molar ratios under ultrasonic irradiation afforded mono and bis thiocarbohydrazons 3a,b, respectively. Thiocarbohydrazones were reacted with α-haloketone, α-haloester as well as hydrazonoyl halides under ultrasonic conditions afforded 1,3-thiazole 4, 1,3-thiazolinone 5 and 1,3,4-thiadiazines 6 and 11a–c, respectively. The reaction of monohydrazone 3a with phthalic anhydride derivatives afforded phthalazines 7a,b in a good yield. Ultrasonic irradiation has benefits such as greater purity, lower cost, high yields, and simple workups compared to the conventional methods. All the new compounds were screened for antimicrobial activity against different tested microbes. Most of the newly synthesized compounds exhibited potent to moderate activities toward the tested microbes. Compounds that exhibited potent antimicrobial activities were selected to measure their MIC and MBC values. The results revealed that compounds 3a, 3b, 8, 10, and 11a showed lower MIC against Staphylococcus aureus with the values of 39.06, 78.13, 9.77, 39.06 and 39.06 µg/ml, respectively. Meanwhile, the MBC values were found to be acceptable for 3a and 10 of 156 and 312, respectively.

Quantitative structure-activity relationship (QSAR) analysis has been performed in order to predict the antifungal activity of dihydroindeno and indeno thiadiazines against toxigenic fungus Aspergillus flavus. The studied compounds were classified according to their lipophilicity using the principal component analysis (PCA). The partial least square regression (PLSR) was used to distinguish the most important molecular descriptors for non-linear modeling. Artificial neural networks (ANNs) were applied for the antifungal activity prediction. The best QSAR models were validated by statistical parameters and graphical methods. High agreement between the observed and predicted antifungal activity values indicated the good quality of the derived QSAR models. The obtained QSAR-ANN models can be used to predict the antifungal activity of dihydroindeno and indeno thiadiazines and of structurally similar compounds. The modeling of the antifungal activity can contribute to the synthesis of new antifungal agents with better ability to protect food and feed from the mycotoxins.

A series of Ethyl 2-[2-(2,5-disubstituted-1H-indol-3-yl)-4-oxothiazolid-3-ylamino]-5,6-dihydro-5-oxo-4H-1,3,4-thiadiazine-6-carboxylates (4a–g) were synthesized from cyclocondensation of Ethyl 2-{(2E)-2-[(2,5-disubstituted-1H-indol-3-yl) methy leno] hydrazine}-5-oxo-5,6-dihydro-4H-1,3,4-thiadiazine-6-carboxylates (3a–g) with thioglycolic acid in the presence of the catalytic amount of zinc chloride. The compounds 3a–g were obtained from the reaction of Ethyl 2-hydrazinyl-5,6-dihydro-5-oxo-4H-1,3,4-thiadiazine-6-carboxylate (2) with various substituted indole-3-carboxaldehydes 1a–g. Newly synthesized compounds were characterized by using IR, 1H NMR, Mass spectral and analytical data. Title compounds were evaluated for their in vitro antimicrobial activities against various microbial strains and selected compounds were tested for their analgesic and anti-inflammatory activities. Some of the newly synthesized Indolyl 4-thiazolidinone analogues displayed significant activity towards antimicrobial, analgesic and anti-inflammatory activities.

Synthesis of [3,4-b][1,3,4]thiadiazines from the condensation of 4-amino-6-methyl-3-thioxo-1,2,4-triazine-5(2H)-one (AMTTO) or 4-amino-1,4-dihydro-5-methyle-1,2,4-triazole-5-thione (AMTT) with phenacyl bromide in the presence of a catalytic amount of various heteropolyacids (HPAs) under refluxing conditions is reported. DOI: http://dx.doi.org/10.4314/bcse.v28i1.8

The 3,5-disubstituted tetrahydro-2H-1,3,5-thiadiazine-2-thione scaffold has found many applications in recent years. This review is aimed at highlighting the most important aspects of these compounds: Synthesis, spectroscopic characterization and biological activities. How the chemical nature of N-substituents influences the overall activity and cytotoxicity profile will also be discussed.

Substituted thiadiazines exert a reliable therapeutic effect in treating stress, and a schematic description of their ability to influence all aspects of a stress response has been depicted. This study was conducted to pharmacologically evaluate compound L-17, a substituted thiadiazine, (2-morpholino-5-phenyl-6H-1,3,4-thiadiazine, hydrobromide) for possible anti-psychotic/antidepressant activity. Compound L-17 was synthesized by cyclocondensation of α-bromoacetophenone with the original morpholine-4-carbothionic acid hydrazide. Pharmacologic evaluations were conducted using methods described by E.F. Lavretskaya (1985), and in accordance with published guidelines for studying drugs for neuroleptic activity. Compound L-17 was evaluated for various possible mechanisms of action, including its effects on cholinergic system agonists/antagonists, dopaminergic neurotransmission, the adrenergic system, and 5-HT3 serotonin receptors. One or more of these mechanisms may be responsible for the beneficial effects shown by thiadiazine compounds in experiments conducted to evaluate their activity in models of acute stress and acute myocardial infarction.