METHOD FOR PRODUCING 3,4-DIHYDRO-1,2,3-OXATHIAZIN-4-ONE-2,2-DIOXIDE COMPOUND OR SALT THEREOF

摘要

Disclosed is a method for simply and efficiently producing a high-quality 3,4-dihydro-1,2,3-oxathiazin-4-one-2,2-dioxide compound or a salt thereof. Specifically, when a compound represented by the formula (2) below or a salt thereof is produced by subjecting a mixed solution of a ß-ketoamide-N-sulfonic acid represented by the formula (1) below or a salt thereof and an inert solvent as well as a mixed solution of an acid anhydride and an inert solvent to a cyclization reaction and then to a hydrolysis reaction, there is performed at least a step (A) wherein a reaction product obtained by the cyclization reaction is mixed with an aqueoussulfuric acid solution and hydrolyzed so that the water layer after hydrolysis has a sulfuric acid concentration of not less than 30% by weight, and then the organic layer and the water layer are separated, or a step (B) wherein the organic layer after the hydrolysis reaction is cleaned with an aqueous sulfuric acid solution having a concentration of not less than 30% by weight. (In the formula, R<SUP>1</SUP>, R<SUP>2</SUP> and R<SUP>3</SUP> represent a hydrogen atom or an organic group which is inert to the reaction; and X represents a hydrogen atom.)