PROCESS FOR PREPARING 6-METHYL-3,4-DIHYDRO-1,2,3-OXATHIAZIN-4-ON-2,2-DIOXIDE

摘要

6-Methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide is prepared by cylcizing acetoacetamide-N-sulfonic acid or its salts with an at least approximately equimolar amount of SO3 in the presence of a water-immiscible, inert organic solvent and, if appropriate, also an inert, inorganic solvent. In the event that an equimolar amount of SO3 is employed, working up is effected by adding aqueous sulfuric acid when the cyclization reaction is complete; in the event that the amount of SO3 employed is more than equimolar, the 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide obtained in the form of the SO3-adduct is hydrolyzed by adding water or ice, whereby sulfuric acid is formed from the SO3 combined in the SO3-adduct. The inert, organic solvent is then removed from the resulting multi-phase mixture by distillation, and the 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide is obtained in a pure form from the remaining aqueous sulfuric acid phase by crystallization. Additionally, quite generally, crude 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide is purified by recrystallization from aqueous sulfuric acid. The non-toxic salts of 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2 dioxide-in particular the potassium salt-are valuable synthetic sweetening agents.