The thiazolo[3,2-b][1,2,4]triazole-6-one represent a bicyclic heteroatom-rich scaffold which recently, has considerably attracted the attention of medicinal chemists due to their diverse biological activities. The [2+3]-cyclocondensation reaction of substituted 1,2,4-triazole-3(5)-thiols with equivalents of electrophilic synthon [C₂]²⁺ is key synthetic approach for 5-substituted thiazolo[3,2-b][1,2,4]triazole-6-ones. The chloroacetic acid as [C₂]²⁺ synton is studied well (mostly in multicomponent reaction with aromatic/heteroaromatic aldehydes) in this reaction type meanwhile data about other ones are limited. In present work we report our studies of the interaction of 1-phenyl-1H-pyrrole-2,5-dione derivatives (N-arylmaleimides) and 3-bromodihydrofuran-2(3H)-one (α-bromo-γ-butyrolactone) as possible [C₂]²⁺ synthons with 1,2,4-triazole-3(5)-thiole targeting on synthesis of novel 5-substituted thiazolo[3,2-b][1,2,4]triazole-6-ones. According to obtained results was establish that in the above-mentioned interactions (conditions: classic heating, a wide range of solvents and reaction time) the thiol-ene click process (with N-arylmaleimides) and nucleophilic substitution (with α-bromo-γ-butyrolactone) take place, but not [2+3]-cyclocondensation reaction as could be expected. The structure of compounds was studied and confirmed using ¹H, ¹³C NMR spectroscopy, LC-MS spectrometry, and X-ray diffraction analysis. The screening of antimicrobial activity (MIC determination) for synthesized compounds was performed against Gram-positive and Gram-negative bacteria, as well as yeasts. The synthesized 1-(4-R-phenyl)-3-(2H-[1,2,4]triazol-3-ylsulfanyl)-pyrrolidine-2,5-diones were found highly active against methicillin-sensitive (MSSA) and methicillin-resistant (MRSA) strains of Staphylococcus aureus, as well as Candida albicans strains. The obtained results suggest to coming design and synthesis of new 1,2,4-triazole/pyrrolidine-2,5-dione hybrids as potential molecules with promising antimicrobial properties.