THIOPHENOLS FROM PHENOLS 2-NAPHTHALENETHIOL

Submitted by Melvin S. Newman and Frederick W. Hetzel Checked by W. Schilling, R. Keese, and A. Eschenmoser 

The reaction mixture is made alkaline with 50 ml. of 10% potassium hydroxide solution and is shaken three times with 100-ml. portions of benzene. The organic layers are combined, washed with a saturated sodium chloride solution, and dried by filtration through anhydrous magnesium sulfate. The solvent is removed by distillation to give the crude product that is crystallized from 75 ml. of absolute methanol to yield 23.5-25.2 g. (68-73%) of colorless crystals of 0-2-naphthyldimethyl-thiocarbamate, m.p. 90-90.5°. 

2-Naphthalenethiol. In a 250-ml. flask, fitted with a diffusion tube and swept with nitrogen, is placed 23.1 g. (0.10 mole) of 0-2-naphthyldimethylthiocarbamate (Note 4). The flask is heated at 270-275° for 45 minutes in a salt bath (Note 5). After cooling, a solution of 8.4 g. (0.15 mole) of potassium hydroxide in 10 ml. of water and 75 ml. of ethylene glycol is added to the flask. The diffusion tube is replaced by a condenser, and the mixture is heated at reflux for 1 hour (Note 6). The cooled reaction mixture is poured onto 150 g. of ice. After the ice has melted, the mixture is shaken two times with 150-ml. portions of chloroform. The chloroform layers are discarded, and the aqueous layer is cautiously acidified with concentrated hydrochloric acid (Note 7) and shaken three times with 75-ml. portions of chloroform. The organic layers are combined and dried by filtration through anhydrous magnesium sulfate. The solvent is removed by distillation to yield 13-15 g. of crude product. Distillation yields 10.3-12.8 g. (71-80%) of pure 2-naphthalene-thiol, b.p. 92-94° (0.4 mm.), m.p. 80-81° (Note 8). 

Practical 2-naphthol, obtained from Matheson Coleman and Bell, was recrystallized twice from benzene to m.p. 123-124°. 

Dimethylthiocarbamyl chloride can be prepared as described in Org. Syn., Coll. Vol. 4, 310 (1963), or by rapidly adding 740 g. (10.5 moles) of chlorine dissolved in 3 1. of carbon tetrachloride to a stirred refluxing suspension of 2400 g. (10 moles) of tetramethylthiram disulfide (Note 9) in 5 1. of carbon tetrachloride. After the addition is complete, approximately onc-half of 

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