Sulfuric Acid → Methyl 3-hydroxy-4-phenylthiobenzoate

Participants

Reaction Conditions

Reaction Steps

3-Amino-4-phenylthiobenzoic acid (110.27 g) is added to a heated solution of conc. sulfuric acid (81 ml) in water (400 ml), and the mixture is heated with stirring for 2 hours and then cooled to -5° C. with an ice-sodium chloride bath. To the mixture is added a solution of sodium nitrite (36.25 g) in water (80 ml) which is previously ice-cooled over a period of about one hour. The mixture is further stirred at 0°-5° C. for 30 minutes. To the mixture is added urea (2 g), and the mixture is stirred for 30 minutes to decompose the unreacted nitrous acid. The resulting mixture is gradually added with stirring to a mixture of conc. sulfuric acid (121 ml), anhydrous sodium sulfate (168 g) and water (112 ml) at 100°-110° C. over a period of one hour and 15 minutes. After the addition, the mixture is stirred at the same temperature for one hour. The reaction mixture is cooled, and the resulting brown granular precipitate is separated by filtration, washed with water, and dried at 50° C. overnight. The product is added to a mixture of methanol (1.4 liter) and conc. sulfuric acid (70 ml), and the mixture is refluxed with stirring for 2 hours. After the reaction is completed, the reaction mixture is concentrated under reduced pressure, and to the residue is added water (1.5 liter), and the mixture is extracted with ethyl acetate (500 ml×3). The combined extracts are dried over anhydrous sodium sulfate and concentrated under reduced pressure. The residue is extracted with heated hexane (4.2 liter), and the extract is cooled. The resulting yellow precipitate is separated by filtration to give methyl 3-hyroxy-4-phenylthiobenzoate (49.37 g).

Provenance & Evidence