Hydrochloric Acid → Benzenethiol, 2-amino-3,4,6-trifluoro-, hydrochloride

Participants

Reaction Conditions

Reaction Steps

A solution of 4,5,7-trifluoro-2-methylbenzothiazole (25.0 g, 123 mmol) in ethylene glycol (310 mL, 0.4 M) and 30% aq NaOH (310 mL, 0.4 M) is degassed using a nitrogen stream and subsequently heated to a gentle reflux (125° C.) for 3 h. The solution is cooled to 0° C. and acidified to pH 3-4 using conc. HCl (appox. 200 mL). The solution is extracted with ether (750 mL) and washed with water (200 mL). The organic layer is dried over Na2SO4, filtered and treated with 2,2-di-tert-butyl-4-methylphenol (0.135 g, 0.5 mol %). After concentrating to dryness, the crude product is dissolved in anhyd methanol (200 mL) and treated with an HCl solution in 1,4-dioxane (37 mL, 4 N, 148 mmol). The resulting mixture is concentrated to dryness, triturated with isopropylether (100 mL) and filtered to give 2-amino-3,4,6-trifluorothiophenol hydrochloride (19.3 g, 73%) as a light brown solid that is used without further purification. mp. 121-124 C; Rf 0.43 (30% ethyl acetate in heptane); Anal. calcd for C6H5ClF3NS: C, 33.42; H, 2.34; N, 6.50; S, 14.87. Found C, 33.45; H, 2.27; N, 6.48; S, 14.96.

Provenance & Evidence