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US 4,229,583 AGranted
Process for preparing thio-indigo dyestuffs
AssigneeHoechst Aktiengesellschaft
InventorsErnst Spietschka, Manfred Urban
Life of this patent
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Abstract
Thioindigo and its derivatives are obtained in high yield and excellent purity by oxidizing corresponding 3-hydroxythionaphthenes with peroxo-disulfate in an aqueous alkaline solution.
Claims6
In a process for preparing a thioindigo compound by oxidation of a corresponding 3-hydroxy-thionaphthene or benzothionaphthene with an aqueous alkaline solution of an ammonium or alkali metal peroxo-disulfate, the improvement comprising performing the oxidation at a temperature of -20.degree. to +50.degree. C.
Dependencies are inferred from the claim text.