Versatile syntheses of 5-imino or 5-acylidene substituted 1,3-thiazolidin-4-one derivatives are reported from alpha-dioxothiazole systems and phosphoranes via Wittig reactions. Antimicrobial and antioxidant activity of the compounds were evaluated. 5-Carbonylmethylene substituted 2-thioxo-1,3-thiazolidines have better antioxidant properties than the 5-arylimino substituted ones. The % inhibition value of the compound 3 (90.8%) was near to that of standard BHT (93.6%) at the same concentration. Compounds 5 and 15, which have the alkyliden-amide group at the C-5 position of the 1,3-thiazolidine ring showed the highest antimicrobial activities among the synthesized compounds. (C) 2015 Elsevier Ltd. All rights reserved.