Hydrogen Sulfide → 2-Chloro-6-fluorobenzene-1-carbothioamide

Participants

Reaction Conditions

Reaction Steps

2-Chloro-6-fluorobenzonitrile (1230 g, 7.91 mol) was weighed into a 22 L jacketed glass reactor (without bottom drain), along with Et3N (1.5 L, 10.76 mol) and pyridine (2.4 L, 29.67 mol) and the stirring solution was cooled to −18° C. under a blanket of N2. The reactor N2 purge mineral oil bubbler was vented to a carboy containing 16 L of 12% bleach solution. Hydrogen sulfide gas (407 g, 11.94 mol) was introduced below the surface of the cold reactor solution over a period of 5.5 hrs. During this time the reactor temperature rose from −18 to −4° C. The solution was stirred overnight at −7° C. (16 hrs), sampled by GC to ensure complete conversion of 2,6-CFBN, then quenched by vacuum transfer of the reactor solution into a second 22 L flask containing 14 L of cold water stirring at 300 RPM (Note: Quenching into a well-stirred tank of cold water produces small white particles of easily filtered product). After the vacuum transfer was completed, another 2 L of cold water was added to the stirring slurry. The light yellow slurry of white solid was drained from the quench tank into bottles, and the solid product was collected by filtration through a course glass buchner funnel, followed by washing of the solid product with an excess of de ionized water. The white solid was air suction dried for 3 h, air dried in a glass pan overnight, then dried in a vacuum oven at 50° C. at 0.3 mm Hg for 8 hrs to give 1004 g (67%) of dry 2-chloro-6-fluorobenzenecarbothioamide, m.p. 153-157° C.

Provenance & Evidence