Phosphorus sulfide (P2S5) → 5-Pyrazin-2-yldithiole-3-thione

Participants

Reaction Conditions

Reaction Steps

3,3-bis-Methylthio-1-(pyrazin-2-yl)-prop-2-en-1-one (2.26 g.) is added in the course of about one minute to a boiling suspension of phosphorus pentasulphide (7.1 g.) in anhydrous xylene (140 cc.). Heating under reflux is continued for one hour after the end of the addition, and the reaction mixture is then cooled to a temperature of about 20° C. An insoluble product is filtered off and washed with 1,2-dichloroethane (200 cc.). The filtrate is concentrated to dryness under reduced pressure and the residue obtained is taken up in 1,2-dichloroethane (100 cc.). An insoluble product is filtered off and washed with 1,2-dichloroethane (4 × 50 cc.). The filtrate is extracted successively with a 10% aqueous sodium carbonate solution (100 cc.) and with water (2 × 100 cc.) and is then dried over magnesium sulphate. After filtration of the dried solution, and concentration to dryness under reduced pressure (30 mm Hg), the residue obtained is suspended in carbon disulphide (50 cc.). The insoluble product is filtered off and taken up in boiling 1,2 -dichloroethane (25 cc.). The boiling suspension is filtered and then cooled. A product precipitates and is filtered off and then washed with 1,2-dichloroethane (2 × 2 cc.). After drying, 5-(pyrazin-2-yl)-1,2-dithiole-3-thione (0.36 g.) melting at 196° C. is obtained.

Provenance & Evidence