Hydrochloric Acid → 2-Chloro-6-fluorobenzene-1-carbothioamide

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Reaction Steps

Into a 250-mL 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 (45 mL), 2-chloro-6-fluorobenzonitrile (15.5 g, 0.1 mol), triethylamine (13.4 g, 18.6 mL, 0.133 mol), and sodium sulfide hydrate (36.0 g, 0.15 mol). The temperature of the resulting solution was lowered to approximately 5° C. using an ice bath. To the stirred slurry was added dropwise concentrated hydrochloric acid (25.8 g, 0.266 mol). The rate of addition of the hydrochloric acid was such that the temperature of the reaction mixture did not exceed 25° C. with an addition time of 20 min. The cooling bath was removed and the slurry was allowed to warm to RT and to stir over night. An additional 40 grams of sodium sulfide and 50 mL of hydrochloric acid was added to the mixture and allowed to stir over night. An additional 40 grams of sodium sulfide and 50 mL of hydrochloric acid was added and the mixture allowed to stir over the weekend. The mixture was poured into water (2 L) and was extracted with ether. The ether layer was washed with dilute sulfuric acid, water, brine, dried (MgSO4), and the solvent removed in vacuo to give 16.1 g of crude product which was recrystallized from ethyl acetate to give 2-chloro-6-fluoro-benzthioamide as light yellow crystals: mp 156-158° C.

Provenance & Evidence