Hydrochloric Acid → 2-(3,4-Dichloro-phenylamino)-ethanethiol hydrochloride

Participants

Reaction Conditions

Reaction Steps

A 3-necked 2 L round bottomed flask equipped with an overhead stirrer, temperature probe and reflux condenser with Dean-Stark trap was charged with 100.0 grams (0.617 mol) of 3,4-dichloroaniline and 500 mL of toluene. The resulting solution was then treated with 64.4 mL (0.927 mol, 1.5 equivalents) of mercaptoacetic acid. The solution was heated to reflux (130° C.), while collecting water in the Dean-Stark trap for 20 hours, then cooled to room temperature. Ethyl acetate (250 mL) was then added followed by 123 mL of 1N hydrochloric acid. The layers were separated and the organic layer washed with 250 mL of water then 500 mL of saturated aqueous sodium bicarbonate and concentrated under vacuum to a volume of approximately 200 mL. After addition of 200 mL of toluene, the solution was again concentrated to approximately 200 mL, diluted with 1 L of tetrahydrofuran and filtered. This filtrate was added dropwise to a nitrogen-purged 3-necked 5 L round bottomed flask containing 1.73 L (1.73 mol, 2.80 equivalents) of 1N borane-tetrahydrofuran complex while maintaining a temperature of 10-15° C. Some gassing was observed. The reaction mixture was warmed to room temperature and stirred overnight then cooled to 10° C. A solution of 252 grams (6.91 mol, 11.2 equivalents) of anhydrous hydrogen chloride in 840 mL of ethanol was added at 10-15° C. during which time significant gas evolution was observed and solids precipitated. After stirring for 1 hour at 5-10° C. the solids were collected by filtration, washed with tetrahydrofuran, and dried under vacuum to yield 100.0 grams (62.6% yield) of the title compound as a white solid, mp 185-188° C. 1H NMR (DMF-d7) δ7.20 (d, J=8.7 Hz, 1H), 7.01 (d, J=2.7 Hz, 1H), 6.78 (dd, J=2.7, 8.7 Hz, 1H), 3.18 (dd, J=6.4, 7.7 Hz, 2H) 2.61 (br s, 2H), 2.37 (br s, 1H). 13C NMR (DMF-d7) δ146.02, 132.94, 134.90, 122.70, 118.09, 117.19, 50.05, 23.07. HRMS (FAB) calcd for C8H9Cl2NS: 221.9911; found: 221.9893.

Provenance & Evidence