Daicel Chemical Industries, Ltd.

Yuki Ishiguro

Yasushi Yamamoto

Akira Saito

A high quality 3,4-dihydro-1,2,3-oxathiazin-4-one-2,2-dioxide compound or a salt thereof is obtained easily and efficiently. When the compound represented by the following formula (2) [Formula 2] (wherein, R, R, and Rare hydrogen atom or an organic group inert to the reaction, and X is hydrogen atom) or a salt thereof is produced by cyclization of a mixture of &#x3b2;-ketoamide-N-sulfonic acid represented by the following formula (1)[Formula 1] or a salt thereof and an inert solvent and a mixture of acid anhydride and an inert solvent, and by subsequent hydrolysis of the product, a step of (A) hydrolyzing the reaction product obtained by the cyclization by mixing with an aqueous solution of sulfuric acid so as a concentration of sulfuric acid in an aqueous phase after the hydrolysis would become 30% by weight or more, and then separating an organic phase and an aqueous phase, or a step of (B) washing the organic phase liquid after the hydrolysis with an aqueous solution of sulfuric acid with a concentration of 30% by weight or more is at least carried out.

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Myoko, Japan

Yuki Ishiguro