Sodium Hydroxide → 2,4-Dichloro-6-fluoro-7-hydrazinobenzothiazole

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Reaction Steps

14.7 g 7-amino-2,4-dichloro-6-fluorobenzothiazole was dissolved in 128 ml concentrated hydrochloric acid and the mixture stirred for 30 minutes at room temperature. It was then cooled to -5° C. and, very slowly, a solution of 4.5 g sodium nitrite in 9.5 ml water was added, dropwise. The mixture was stirred for one hour and cooled to -15° C. At this temperature, a solution of 31.5 g tin (II) chloride in 19 ml concentrated hydrochloric acid was added, dropwise at a rate that the temperature did not rise above -8° C. The mixture was stirred for one hour, made alkaline using caustic soda, whilst cooling, and extracted with dichloromethane. The extract was dried over magnesium sulfate and concentrated. Yield: 7.8 g=50% of theory m.p.: 162°-180° C.

Provenance & Evidence