Thiophosgene → 6-fluoro-5-isothiocyanato-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-2(3H)-benzothiazolone

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Reaction Steps

A mixture of 5-amino-6-fluoro-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-2(3H)-benzothiazolone (1.33 g), dichloromethane (10 ml) and ice (10 g) was prepared. To this mixture was added thiophosgene (0.7 g), and then portionwise added sodium bicarbonate at a temperature of 5° to 10° C. so as to make the mixture slightly alkaline. The mixture was stirred for 20 minutes, and tested to confirm whether the mixture was alkaline (if the mixture was acidic, then a further amount of sodium bicarbonate was added). The dichloromethane layer was separated, and the aqueous layer was extracted with fresh dichloromethane (10 ml×2). The dichloromethane layers were gathered together, washed with water, and distilled to remove the dichloromethane solvent therefrom. The resulting solid residue was recrystallized from a toluene-hexane solvent mixture, so that the aimed compound, i.e. 6-fluoro-5-isothiocyanato-3-(5-methyl-1,2,4-oxadiazol-3-ylmethyl)-2(3H)-benzothiazolone (1.49 g) was obtained. m.p. 168°-170° C.

Provenance & Evidence