Hoechst Aktiengesellschaft

Hartmut Pietsch

Erwin Schmidt

Harald Jensen

Karl Clauss

Rudolf Pistorius

Michael Mitzlaff

Jurgen Cramer

Klaus Dehmer

N-Vinyl-N-alkyl-carboxylic acid amides are prepared, starting from N-ethyl-carboxylic acid amides, in a 3-stage process consisting of the following stages:

Process for the preparation of N-vinyl-N-alkyl-carboxylic acid amides

Process for preparing acetoacetamide-N-sulfofluoride by reacting amidosulfofluoride at a temperature of from 50.degree. to 100.degree. C with diketene, optionally in the presence of inert solvents or diluents.

Process for preparing acetoacetamide-N-sulfofluoride

3-Sulfohalides of 6-methyl-2H-1,3-oxazin-2,4(3H)-dione of the formula I ##STR1## in which X represents fluorine or chlorine are prepared by reacting fluorosulfonyl isocyanate or chlorosulfonyl isocyanate, at a temperature of from -35.degree. to +70.degree. C, optionally in the presence of an inert solvent, with diketene, acetoacetyl fluoride, acetoacetyl chloride, acetoacetic acid or an isopropenyl ester of the formula CH.sub.2 =C(OOCR)-CH.sub.3 in which R represents an alkyl radical having from 1 to 4 carbon atoms, a substituted or unsubstituted phenyl or benzyl radical.

6-Methyl-2H-1,3-oxazin-2,4(3H)dione-3-sulfohalides

Compounds of the formula ##SPC1## In which R represents an alkyl radical having from 1 to 4 carbon atoms and Hal stands for fluorine or chlorine are prepared by reacting at a temperature of from -40.degree. to +20.degree. C an i-propenylalkanoic acid ester of the formula ##EQU1## with an isocyanate of the formula

.beta.-Acyloxy-crotonic acid amide-N-sulfohalides and a process for

6-Methyl-3,4-dihydro-1,2,3-oxathiazin-4-one-2,2-dioxide or the nontoxic salts thereof is prepared by reacting 6-methyl-2,3-dihydro-1,3-oxazin-2,4-dione-3-sulfo-fluoride of the formula ##EQU1## with at least 1 mole water per mole of fluoride to obtain acetoacetamide-N-sulfo-fluoride with splitting off of CO.sub.2, treating the acetoacetamide-N-sulfofluoride with an aqueous and/or alcoholic base and isolating the oxathiazinone or the salts thereof.

Process for the manufacture of

The potassium salt practically free of fluoride of 6-methyl-3,4-dihydro-1,2,3-oxathiazin-4-one-2,2-dioxide is prepared by cyclization of acetoacetamide-N-sulfofluoride with at least two moles potassium hydroxide, potassium methylate or a mixture of potassium hydroxide and potassium methylate per mole of sulfofluoride in methanol as solvent containing less than 50 % by weight of water at a temperature of from -20.degree. to +60.degree.C and separating the crystalline potassium salt of the oxathiazinone dioxide from the reaction solution. The compound obtained has a pure sweet taste.

Process for the manufacture of the potassium salt of

6-Methyl-3,4-dihydro-1,2,3-oxathiazin-4-one-2,2-dioxide and the nontoxic salts thereof are prepared by reacting acetone and fluorosulfonyl isocyanate in a molar proportion of from 14:1 to 150:1 at a temperature of from 0.degree. to 60.degree.C, distilling off the excess acetone from the reaction mixture with acetoacetamide-N-sulfofluoride and bringing about cyclization by a treatment with bases at a pH of from 5 to 12. The oxathiazinone derivatives are used as sweeteners.

6-Methyl-3,4-dihydro-1,2,3-oxathiazin-4-one-2,2-dioxide and the nontoxic salts thereof are prepared by reacting acetoacetic acid with fluorosulfonyl isocyanate at a temperature of from -20.degree.C to +50.degree.C in the presence of from 0.5 to 2 moles, calculated on the FSI used, of an alkali methal fluoride or a tertiary amine of the formula

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Hofheim, Taunus, Germany

Hartmut Pietsch