GENERAL METHODS: (Z)-2-Amino-5-(4-hydroxybenzylidene)thiazol-4(5H)-one was synthesized from p-hydroxybenzaldehyde and pseudothioglycolide. The procedure was as follows: a mixture of p-hydroxybenzaldehyde (300 mg), pseudothioglycolide (1.1 eq.) and sodium acetate (3.0 eq.) was heated and refluxed for 3 to 7 hours under acetic acid (4 mL/1 g sodium acetate) as a solvent. Upon completion of the reaction, the reaction mixture was cooled and water was added to precipitate the product. The precipitate was collected by filtration and washed with water, dichloromethane and/or ethyl acetate depending on the physical properties of the starting material to finalize the target product. The product was an orange solid with a reaction time of 3 hours, a yield of 61.8% and a melting point of over 300 °C. The structure of the product was determined by 1H NMR (500 MHz, DMSO-d6) δ 10.10 (s, 1H), 9.29 (brs, 1H), 9.04 (s, 1H), 7.49 (s, 1H), 7.40 (d, 2H, J = 9.0 Hz), 6.88 (d, 2H, J = 8.5Hz); 13C NMR (100 MHz, DMSO-d6) δ 181.4, 176.1, 159.6, 132.1, 130.2, 126.0, 125.5, 116.8; and mass spectrometry (ESI) m/z 219 ([M-H]-) were confirmed.
