A rapid, efficient, and one-pot protocol has been developed for the synthesis of cyclized 2,6-dimethyl-5-substituted-thiazolo[3,2-b]-s-triazoles (3a–c) through the interaction of 5-methyl-1H-s-triazole-3-thiol (1) with aliphatic ketones (2a–d) in refluxing acetic acid in the presence of a catalytic amount of sulfuric acid (AcOH/H⁺) while with aromatic ketones (5a–d), a mixture of uncyclized 3-methyl-s-triazolylthioacetophenone derivatives (6a–d) and cyclized 6-aryl-2-methyl-thiazolo[3,2-b]-s-triazoles (7a–d) has been produced. With this catalytic system, inexpensive sulfuric acid was utilized as a catalyst, which prevented the production of poisonous and irritating halo carbonyl compounds. On the other hand, the interaction of s-triazole 1 with cyano compounds (9a,b) afforded the corresponding 6-amino-2-methyl-5-substituted-thiazolo[3,2-b]-s-triazoles (10a,b). Similarly, treatment of 4-amino-3-methyl-s-triazole-5-thiol (12) with aliphatic and aromatic ketones (2c and 5a–e) afforded directly 3-methyl-7H-s-triazolo[3,4-b]-1,3,4-thiadiazines (13a and 14a–e). Further, reaction of 12 with cyano compounds (9a,b) under the same reaction conditions yielded the corresponding 3-methyl-s-triazolo[3,4-b]-1,3,4-thiadiazole derivatives (15a,b). The reaction mechanism was studied, and the structures of all novel compounds were verified using spectroscopy and elemental analysis. Moreover, the potential application of the synthesized compounds toward heavy metal ions and inorganic anion removal from aqueous solution has been investigated. The removal effectiveness for metal ions reached up to 76.29%, while for inorganic anions it reached up to 100%, indicating that such synthesized compounds are promising adsorbents for water remediation.