Hydrochloric Acid → ethyl (4R)-2-oxo-1,3-thiazolidine-4-carboxylate

Participants

Reaction Steps

To the solution comprising 2 liters of water containing 180 g of sodium hydroxide was dissolved 175.6 g of L-cysteine monohydrochloride monohydrate under ice-cooling and under nitrogen atmosphere. To the solution was added dropwise 700 ml of a 1,4-dioxane solution containing 118.7 g of triphosgene at 25° C. to 29° C. over 1 hour and 30 minutes, and further stirred at the same temperature for 3 hours. To the reaction mixture was added conc. hydrochloric acid to adjust the mixture to weak acidic solution, and then, the solvent was removed under reduced pressure. To the concentrated residue was added 200 ml of toluene, and the solvent was removed again under reduced pressure. To the concentrated residue was added 700 ml of ethanol, 131 g of thionyl chloride was added to the mixture under ice-cooling over 40 minutes, and the resulting mixture was stirred for 19 hours while raising the temperature to room temperature. The solvent was removed under reduced pressure, and then, the concentrated residue was dissolved in 1 liter of ethyl acetate, and the mixture was successively washed with 700 ml of water, 300 ml of an aqueous saturated sodium bicarbonate solution and 500 ml of saturated brine. After the mixture was dried over anhydrous magnesium sulfate, and the solvent was removed under reduced pressure to give 162 g of ethyl (4R)-2-oxothiazolidin-4-carboxylate as oily product.

Provenance & Evidence