2.2.4. Synthesis of 4-(4-pyridyl)-1,3-dithiol-2-one (**4**)

**3** (4.9 g,19 mmol) was dissolved in 7.5 mL conc. H2SO4, and the resulting black solution was heated to 50 ◦C for 30 min. The solution was poured into 200 mL of H2O, neutralized by NaHCO3, and extracted with dichloromethane. The solvent was dried with MgSO4 and evaporated to obtain a brown solid. This solid was recrystallized with EtOH to get a brown crystalline solid. 1H NMR (500 MHz, CDCl3, 298 K, ppm) δ 8.70 (d, 2H), 7.33 (d, 2H), 7.18 (s, 1H).
