Preparation method of Acemi

1. Acetylacetamide, sulfur trioxide, and KOH as raw materials
Firstly, acetylacetamide sulfonic acid is synthesized in an inert organic-inorganic solvent, and SO3 is passed into acetylacetamide for cyclic condensation. Then extract and separate it, and react it with KOH to obtain the product. For example, at -60 ℃, add 5.1g (50mmol) of acetylacetamide dissolved in 50mL of CH2Cl2 dropwise to 8mL (200mmol) of liquid SO3 dissolved in 50mL of CH2Cl2, stir for 2 hours, and then add 50mL of ethyl acetate and 50mL of water to the solution. Separate the organic phase after extraction. Extract the aqueous phase twice with ethyl acetate, and combine the obtained organic liquid into the organic phase. Dry on anhydrous Na2SO4 and evaporate to recover ethyl acetate. The residue was dissolved in methanol and neutralized with KOH solution to precipitate acesulfame. After drying, 3.1g of product was obtained with a recovery rate of 31% of the theoretical amount. The disadvantage of this method is that the reaction needs to be carried out at a relatively low temperature and the yield is not high.
2. Using amino sulfonic acid, triethylamine, dienone, SO3, and KOH as raw materials
Add 9.7g (0.1mol) of aminosulfonic acid to 16mL (0.12mol) of triethylamine, stir until completely dissolved, then add 8mL of dienone dropwise at 0 ℃ and stir at room temperature until the reaction is complete. Add hexane to precipitate and refine. After removing the solvent under reduced pressure, a slurry was obtained with a yield ranging from 95.7-99.0%. At -30 ℃, add the slurry and 5-6 equivalents to a container containing CH2Cl2 and stir continuously for 1-5 hours. Remove the solvent under reduced pressure, treat the residue with KOH solution, control the pH at 8-10, and remove the solvent and dry to obtain acesulfame with a yield of 69%. The advantage of this method is that the raw materials are easy to obtain, the process conditions are relatively mild, but the process is complex.
3. Using amino sulfonyl fluoride, diketone, potassium carbonate, and KOH as raw materials
At 0 ° C, adding dienone dropwise to an acetone solution of H2NSO2F and K2CO3 produces the potassium salt of ethylhexyl phthalimide N-sulfophthalein fluoride. It is then reacted with CH3OH and KOH solution to produce acesulfame. For example, dissolve 76g (0.55mol) of K2CO3 powder in 500mL of acetone, add 57.8mL (1.0mol) of H2NSO2F, add 84.3mL (1.1mol) of dienone dropwise within 15 minutes, stir and mix at 0 ℃ for 30 minutes, and an exothermic reaction will occur. Control the temperature below 30 ℃ until CO2 is completely released, and then stop the reaction. Filter the reaction mixture by suction and wash with a small amount of acetone. The colorless crystalline potassium salt of N-acetylamino-N-sulfophthalein fluoride is obtained. Stir this potassium salt with 4-6 mol of methanol solution to cyclize it into acesulfame. The yield is 93% of the theoretical amount.