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

Participants

Reaction Conditions

Reaction Steps

A mixture of 5-(pyrazin-2-yl)-1,2-dithiole-3-one (2 g.) and phosphorus pentasulphide (2.3 g.) in dioxan (35 cc.) is heated for 15 minutes at 100° C., whilst stirring. The red suspension obtained is diluted whilst hot with acetonitrile (35 cc.). The solution is decanted and the precipitate obtained is taken up with a hot mixture (2 × 50 cc.) of dioxan and acetonitrile (50:50 by volume). The combined organic phases are filtered hot, diluted with distilled water (250 cc.), and the requisite amount of a 4N aqueous ammonia solution to adjust the pH to 7. The brown precipitate formed is filtered off, washed with distilled water (2 × 25 cc.) and then with diethyl ether (2 × 10 cc.) and dried. 5-(Pyrazin-2-yl)-1,2-dithiole-3-thione (1.87 g.) melting at 200°-201° C. is thus obtained.

Provenance & Evidence