Thiourea (19 g, 0.25 mol) and acetylacetone (25.8 mL, 0.25 mol) were mixed in 125 mL of ethanol in a reaction flask. The reaction mixture was refluxed in a water bath for 2 hours. After cooling slightly, 33.5 mL of concentrated hydrochloric acid was added slowly through a funnel and the reflux heating was continued until the reaction was completed. At the end of the reaction, yellow crystals were obtained by filtration. After removing the solvent, the remaining solution was heated and dissolved with 10% NaOH solution. The pH of the solution was adjusted to about 7, and then cooled at room temperature to obtain 4,6-dimethylpyrimidine-2-thiol as pale yellow acicular crystals with 80.22% yield and melting point of 209-211 °C (literature value 210 °C).
[1] Bollettino chimico farmaceutico, 2004, vol. 143, # 7, p. 275 - 279
[2] Patent: CN105585538, 2016, A. Location in patent: Paragraph 0024
[3] Patent: CN105859693, 2016, A. Location in patent: Paragraph 0021
[4] Patent: CN105622599, 2016, A. Location in patent: Paragraph 0022
[5] Zeitschrift fur Anorganische und Allgemeine Chemie, 2015, vol. 641, # 7, p. 1301 - 1306
