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US 8,476,452 B2Granted
Process for preparing 1,2-benzoisothiazoline-3-one
AssigneeTitan Chemicals Limited
InventorsCarsten Berg, Sangita Singh
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Abstract
Sodium sulfide hydrate is at least partially dehydrated by heating with N-methyl 2-pyrrolidone. 2-chlorobenzamide is added to the mixture which is heated further. The mixture is cooled and treated with aqueous hydrogen peroxide to give the sodium salt of 1,2-benzoisothiazoline-3-one in good yield. Acidification if desired gives rise to the free 1,2-benzoisothiazoline-3-one.
Claims3
A process for preparing the sodium salt of 1,2-benzoisothiazoline-3-one comprising the steps of
- i) heating a mixture of sodium sulfide hydrate and N-methyl 2-pyrrolidone
- ii) distilling from said mixture water and optionally a portion of said N-methyl-2-pyrrolidone to leave a water-depleted mixture of sodium sulfide and said N-methyl-2-pyrrolidone,
- iii) adding at least one benzamide substituted at the 2-position with a good leaving group to the water-depleted mixture of sodium sulfide and N-methyl 2-pyrrolidone to give a mixture comprising 2-mercaptobenzamide and
- iv) subjecting the mixture comprising 2-mercaptobenzamide to oxidative cyclisation.
1 more element
Dependencies are inferred from the claim text.