Synthesis
General procedure for the synthesis of thiophene-2-thioformamide from 2-thiophenecarboxamide: 2-thiophenecarboxamide (1 g, 7.86 mmol) was dissolved in dry 1,2-dimethoxyethane (30 mL). Lawesson's reagent (1.6 g, 3.9 mmol) was added and the reaction was protected under nitrogen. The reaction mixture was stirred at room temperature for 12 hours and then filtered. Subsequently, the solvent was removed by distillation under reduced pressure and the residue was purified by silica gel column chromatography (eluent: petroleum ether/ethyl acetate = 10:1 to 2:1) to afford thiophene-2-thiocarboxamide (1.0 g, 88.8% yield, white solid). Thiophene-2-carbothioamide can be used directly in the subsequent reaction without further purification.
References
[1] Patent: EP2708534, 2014, A1. Location in patent: Paragraph 0055
[2] ACS Medicinal Chemistry Letters, 2013, vol. 4, # 10, p. 904 - 908
[3] Journal of Medicinal Chemistry, 2017, vol. 60, # 17, p. 7512 - 7523
[4] Chemistry - A European Journal, 2013, vol. 19, # 29, p. 9655 - 9662
[5] Journal of Chemical Research, 2010, # 3, p. 151 - 153
