SU715018A3 - Method of preparing dl-cysteine - Google Patents

Abstract

Prodn. of D,L-cysteine and its salts by reaction of 2-substd. -thiazolines with hydrogen cyanide to form the corresp thiazolidine-4-carbonitriles and reaction of these with mineral acids in the presence of water. Process produces D,L-cysteine in excellent yields, with purity sufficiently high to be used directly in the food industry and by a process suitable for industrial scale prodn. known processes give only average yields and use costly starting materials.

Description

(54) METHOD OF OBTAINING DL-CYSTEIN, but with t-4 carbon atoms, which can form a closed ring, cyclopsyl or .aloyl, preliminarily up to 6 carbon atoms, arl, aryl ;. or a1 k llaryl, preferably containing 1-4 carbon atoms in each of the alkyl crystals (Rj and R2 cannot both be hydrogen) can be easily obtained by limestone techniques, nagfimer by reacting dehydrated mercaptoacetal with oxo compound ml and ammonia or halogen acetaldehyde with oxo-salt gens, metal sulfides and ammonia. Hydroxy hydrogen may be primed in gaseous or liquid form, as a solution in water shwx org solutions or it will be obtained from a compound, for example, from crystalline metals, by means of food, food, 1H: with acids. lg:;: G; - worked out / d and the code code ir (; dod - ;: li liueda solvent, r-sprkmer of water or TiepTU.j) i: i organic raszortgeli such as spetszty, complex simple esters aliphatic shgi aromatic, if necessary, halogenated TeMiiepawpR reaction hydrocarbons depends on the nature of the reaction 11 x reagent; and solvent. The most temperature range of T; P ::: l-l ;; s is the temperature of 10-50 ° C 1i: 13i ...- 4-; a1p60 GITrSH DIRECT HiOT JB reaction mixture; iianpiavjep, oy its dependence by distilling off M ;; hoort; a, if the reaction is carried out in an iast ortstg medium, or in the form of a salt, hydrochloride. For long DL-JorcTSHHa mo syo predniKDYu PG / S LIEF, -carbonitrile, g-carbohydrate Proteus i of acid ,. sing I1; AND HZLOGSNBODO 10–40% hydrochloric acid, h; Gyo l ;; g {O; Bzov: 1 stoichomics to and 10 equivalents of acid. The temperature, of which hydro LIZ is carried out, depends on the nature of the reagents, successful in peaKiULH, and the ratio between. It is most preferable to carry out the reaction at 50-11 () ° C. temperature, and then as the reaction proceeds, you can change it in. The pressure can be varied in the Hirokhnx limit , but j 3- -iuie virovo, roliz at a spherical, pressure. At 1: using volatile substances, it is necessary to work at a pressure of low pressure, corresponding to the temperature at which 1 the reaction is formed. DL-cysteine can be separated from the resulting mixture in various ways N in the form of a salt or free base. Nagfimer, distilling off the solvent (if necessary under reduced pressure), extracting the residue with preferably aliphatic alcohol, in particular methanol, ethanol or progan-2-ol, and evaporating the extract (in If necessary, under reduced pressure) p, L-cysteine is obtained in the form of a mineral acid salt. When the extract is neutralized with a base, for example, triethylamine, it is necessary to remove free DL-distein from it. This forms a C L-cysteine of such high purity that it can be directly, without further purifying HpHMeimTjj for any purpose. Example 1. Through a mixture consisting of 103 g (0.7 mol) of mercalto-de-aldehyde and 116 g (2.0 mol) of acetone, is passed to complete pacTBopei-fflH aldehyde and then for 30 min. Ammonia gas, maintaining the temperature for 15 minutes. 25 ° C. Two phases are obtained, more of which contains 2,2-dimethylthiazolin-3. It is separated by a cable fixer, b.p. 40-42 ° C / 16 mbar. To a solution of 115 g (1.0 mol) 2,2-dimethylshazols-1a-3 in 250 svm of diethyl ether was added dropwise 30 g (1.1 mol) of liquid hydrogen cyanide. When added and for the next 60 minutes, the temperature is maintained at 10-20 ° C. Then, while cooling to 5-10 ° C, hydrogen chloride is passed through the mixture until the resulting 2,2-dimethylthiazolide {-1N-4-carbonitrile. does not precipitate as hydrochloride. Receive half-free crystals, so pl. 125-128 C. Yield 170 g (95% (taazolin). 160 g (0.9 mol) of 2,2-dimethylhaazolidin-4-carbonitra hydrochloride is mixed with 500 ml of concentrated hydrochloric acid, boiled for 12 hours with reverse using a refrigerator without air oxygen (purging with nitrogen), decolorize with activated carbon and evaporate to dryness under reduced pressure. The residue is extracted with methanol. Hryethyl / sh to pH 5.0 is added to the extract. D, L-HHCteine is precipitated. 85 g (78% of the original hydrochloride), t.d. 210-.217 ° C, the product does not contain impurities. Example 2. Mix the solution 67 g (1.2 mol) sodium hydrodisulfide in 100 ml of water, 87 tons (1.5 moU) of acetosh, 175 g of a 45% aqueous solution of loracetaldehyde (1.0 mol) are added dropwise and the ammonia is simultaneously passed, maintaining the temperature at 15-25 ° C. The flow of ammonia is continued until the heat production ceases due to the reaction.

Claims (4)

1. The method of producing D L-cysteine from thiazoline derivatives using the hydrolysis reaction in the presence of mineral acids, characterized in that, in order to simplify the process and increase the yield and quality of the target product, thiazoline-3 substituted in position 2 is treated with hydrogen cyanide at a temperature preferably 10-50 ° C and the obtained thiazolidine-4-carbonitrile is subjected to hydrolysis. 2. The method according to claim 1, on the basis of the fact that hydrogen cyanide is used as 1.1-1.5 mol per 1 mol of thiazoline. 3. The method according to claim 1, on the basis of the fact that 3-10 equivalents of mineral acid are taken per 1 mol of thiazolidine-4-carbonigryl. 4. The method according to claims 1 to 3, characterized in that sulfuric, phosphoric or hydrochloric acid is used as a mineral acid.