反应详情

2-mercapto-5-trifluoromethylaniline hydrochloride (22.79 gm, 0.01 mol) was heated to reflux in 200 ml 95% ethanol by volume with 20 ml of 22% (by weight) aqueous potassium hydroxide and 16.0 gm (0.1 mol) of O-ethylxanthic acid, potassium salt. When hydrogen sulfide evolution had ceased, the solution was filtered, cooled and acidified with HCl. The initial precipitate was collected by filtration and discarded. The filtrate was allowed to stand to precipitate 13.79 gm (59% of theory) of desired product, with a melting point of 221°-222° C. The resulting 2-mercapto-5-trifluoromethylbenzothiazole (11.75 gm, 0.05 mol) was slurried in 50 ml of 95% ethanol, treated with 7.1 gm of triethylamine, and then refluxed 1 hour with 7.1 gm (0.05 mol) of iodomethane. The mixture was filtered hot, cooled, concentrated, and treated with water to precipitate 11.54 gm (93% of theoretical) of 2-methylthio-5-trifluoromethylbenzothiazole (melting point of 66° -69° C.). This compound (11.0 gm, 0.044 mol) was then heated to 130°-156° C. with 8.22 gm (0.044 mol) of methyl-p-toluenesulfonate for 5 minutes. After cooling, the resulting solid was washed and triturated with acetone to yield 15.05 gm (78% of theory) of 3-methyl-2-methylthio-5-trifluoromethyl-benzothiazolium p-toluenesulfonate with a melting point of 189°-191° C. This quaternary salt (4.35 gm, 0.01 mol) was dissolved with 1.91 gm (0.01 mol) of rhodanine-3-acetic acid in 20 ml of methanol. After 2.02 gm (0.02 mol) of triethylamine was added thereto, the mixture was stirred at room temperature for 4.5 hours before isolating the precipitated dye by filtration. After washing the filtered solid with methanol, 2.74 gm (54% of theoretical) of this dye was obtained.

1. filtrationthe solution was filtered
2. temperaturecooled
3. filtrationThe initial precipitate was collected by filtration
4. customto precipitate 13.79 gm (59% of theory) of desired product
5. filtrationThe mixture was filtered hot
6. temperaturecooled
7. concentrationconcentrated
8. additiontreated with water
9. customto precipitate 11.54 gm (93% of theoretical) of 2-methylthio-5-trifluoromethylbenzothiazole (melting point of 66° -69° C.)
10. temperatureAfter cooling
11. washthe resulting solid was washed
12. customtriturated with acetone