Benzoyl chloride → 2-(2'-Fluorophenoxy)-6-isothiocyanobenzothiazole

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An amount of 17 g of ammonium rhodanide is dissolved in 200 ml of absolute acetone; an addition is then made to the solution, with stirring, of 31 g of benzoyl chloride. The reaction mixture is allowed to boil with refluxing for 5 minutes; a solution is then added of 57 g of 2-(2'-fluorophenoxy)-6-aminobenzothiazole (obtained from 2-(2'-fluorophenoxy)-6-nitrobenzothiazole by catalytic hydrogenation, cp. Example 6) in 400 ml of acetone. Stirring is continued for 2 minutes at the boiling temperature, and the mixture then poured, with stirring, into 5000 ml of ice water. Filtration is performed, the filter residue washed with water, and suspended in 350 ml of 10% sodium hydroxide solution. The suspension is quickly brought to boiling temperature and allowed to boil for a further 2 minutes. Cooling is then rapidly carried out in an ice bath; the suspension is neutralised with 2-n hydrochloric acid, and the pH-value adjusted with 2-n ammonia to 8. Filtration is again performed, the filter residue washed wth water until neutral, and dried at 80° in vacuo. The finely powdered material is suspended in 500 ml of anhydrous chlorobenzene and refluxed for 14 hours. After the solvent has been evaporated off, the residue is chromatographed through aluminium oxide with methylene chloride as the eluant. The obtained 2-(2'-fluorophenoxy)-6-isothiocyanobenzothiazole melts at 115° - 117°.

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