Synthesis
The general procedure for the synthesis of 1-methylpyrrolidin-2-thione from N-methylpyrrolidone was as follows: N-methylpyrrolidone (0.75 mmol) was dissolved in tetrahydrofuran (THF, 5 mL) in a microwave reaction flask, followed by the addition of phosphorus pentasulfide/aluminum oxide (P2S5/Al2O3, 0.53 g, equivalent to 0.90 mmol of P2S5). After sealing the reaction vial, the suspension was placed in a CEM Discover? microwave reactor and heated by microwave radiation at 60 °C and 60 W power with stirring and air cooling. After 5 min of reaction, the completion of the reaction was confirmed by thin layer chromatography (TLC) monitoring. The reaction solution was cooled and quickly filtered through a short silica gel column. The reaction was first eluted with hexane to remove non-polar impurities, followed by a solvent mixture of hexane/ethyl acetate (EtOAc) to recover the target product 1-methylpyrrolidine-2-thione. Finally, the solvent was removed by distillation under reduced pressure to afford pure 1-methylpyrrolidine-2-thione in 92% yield.
References
[1] Organic Letters, 2012, vol. 14, # 2, p. 440 - 443
[2] Organic Syntheses, 1984, vol. 62, p. 158 - 158
[3] European Journal of Medicinal Chemistry, 1991, vol. 26, # 7, p. 687 - 697
[4] Tetrahedron, 1984, vol. 40, # 11, p. 2047 - 2052
[5] Tetrahedron Letters, 2011, vol. 52, # 40, p. 5131 - 5132
