Hoechst Aktiengesellschaft

Otto E Schweikert

Karl E Mack

Walter Reimann

Adolf Heinz Linkies

Dieter Bernd Reuschling

Werner Wykypiel

Wolfgang Ebertz

Joachim Schutz

Acetoacetamide-N-sulfonic acid and its salts are cyclized with at least approximately the equimolar amount of SO.sub.3 in short times, preferably in special apparatus, to give 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide. In the case where more than the equimolar amount of SO.sub.3 is used, the latter compound is produced as an SO.sub.3 adduct which then needs to be hydrolyzed; the hydrolysis also takes place in short times and, particularly advantageously, in apparatus of the same type as for the cyclization. The non-toxic salts, especially the potassium salt - of 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide are valuable synthetic sweeteners.

Process for the preparation of

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 SO.sub.3 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 SO.sub.3 is employed, working up is effected by adding aqueous sulfuric acid when the cyclization reaction is complete; in the event that the amount of SO.sub.3 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 SO.sub.3 -adduct is hydrolyzed by adding water or ice, whereby sulfuric acid is formed from the SO.sub.3 combined in the SO.sub.3 -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.

The non-toxic salts of 6-methyl-3,4-dihydro-1,2,3-oxothiazin-4-one 2,2-dioxide are prepared by cyclizing 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, hydrolyzing the 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide obtained in the form of the SO3-adduct after the cyclization reaction, in the event that the amount of SO3 employed is more than equimolar, purifying the organic phase (which has separated out) by extraction with a small volume of water or dilute aqueous sulfuric acid, preferably only with water, and isolating, by neutralization with bases, the non-toxic salts of the 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one 2,2-dioxide from the organic phase thus purified. The said salts are obtained in this process in an extremely pure form; they are valuable synthetic sweetening agents. The potassium salt is known as acesulfam (K).

The invention relates to a process for the preparation of 2-hydroxy-(9H)-carbazole. In this process, 1,2,3,4-tetrahydro-7-hydroxy-(9H)-carbazole is dehydrogenated in an inert organic solvent.

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Kelkheim, Germany

Otto E Schweikert