Hydrochloric Acid → 2,6-Difluorobenzene-1-carbothioamide

Participants

Reaction Steps

Into a 3 L three necked round bottom flask equipped with a mechanical stirrer, dry ice condenser, dropping funnel, and outlet to a trap filled with bleach was added pyridine (550 mL), 2,6-difluorobenzonitrile (208 g, 1.50 mol), triethylamine (202 g, 279 mL, 2.0 mol), and sodium sulfide hydrate (521 g, 2.17 mol, broken into pieces small enough to fit into the flask). The temperature of the stirred mixture was lowered to approximately 5° C. and to the slurry was added dropwise concentrated hydrochloric acid (143 g, 288 mL, 3.99 mol). An exotherm was noted and the rate of addition of the hydrochloric acid was such that the temperature of the reaction mixture did not exceed 25° C. for a total addition time of 75 min. The cooling bath was removed and the slurry was allowed to warm to RT and to stir over night. The mixture was poured into water (2 L) and was extracted with ether (3×500 mL). The ether layer was washed with dilute sulfuric acid, water, brine, dried (MgSO4), and the solvent removed in vacuo to give 232 grams of crude product. The starting material was removed from the product via bulb-to bulb distillation to give 197 g (76%) of 2,6-difluorobenzenethioamide. This material was used without further purification.

Provenance & Evidence