<BR> <P> PROCEDURE FOR SYNTHESIS OF N-[2[[[5-(dialkylamino)methyl]-2-furanyl]methyl]thio]ethyl]N '-alkyl-2- nitrol, l alkenediamines and their hydrochlorides Field of technique to which the invention belongs Suggested invention is related to the area of organic chemical technology, specificly to the process of obtaining of therapeutically active products N-2 5- (dialkylamino) methyly-2-furanyly methyly thiof ethyly-N-alkyl-2-nitro 1,1 alkenediamine of formula (I) and their hydrochlorides of formula (II), where Ri, R2 and R3 are alkyl groups (Cl-C4), and X is nitro-alkene group, which are applied in pharmaceutical industry as blockers of histamine H2 receptors. One of them which is well known is N--[2[[[5- [(dimethylamino)methyl]-2-furanyl] methyl] thio] ethyl] - N-methyl-2-nitro- 1,1-ethendiamine (Ranitidine), as well as its hydrochloride (Ranitidine hydrochloride).

Technical problem There was a need to find a new, technologically better process for production of furanic derivatives, primarily Ranitidine and its hydrochloride, with high yield and high purity, which enables their application in pharmaceutical industry, wherein it is used for curing of ulcus duodendi and as hstamine antagonists (H2 receptors). This invention has solved the problem of using of 2 5-(dimethylamino) methyl-2-furanyly methylythiof-ethanamine (Cistofur base), which is unstable, viscous, difficult for supplying, using 2///- (dimethylamino) methyl-2-furanyly methylythiof-ethanamine hydrochloride (Cistofur hidrochloride) which is stable and exists on the market as a powdered substance.

Condition of technique There are several known processes for synthetical production of Ranitidine and its hydrochloride.

Thus, a process for poduction of Ranitidine is described in ES 497,386 where the fundamental substances are chlorhydrate 5- (dimethylamino) methyl-2- chlormethylfuran and N- (2-mercaptoethyl)- N'-methyl-2-nitro-1, 1- ethendiamine. The reaction is carried out in methanol in presence of sodium or potassium hydroxide.

American patent US 4,347,191 provides the process for obtaining of 5- dimethylaminomethyl-2-furanmethanol starting from 2-furanmethanol.

In Spanish patent ES 500,986 a process for obtaining of furanic derivatives is described and according to it 5-dimethylaminomethyl-furan-2- methanol is converted to 5- (dimethylamino) methyl-2-chlormethylfuran in the form of chlorhydrate. In inert environment, obtained product is converted to corresponding mercaptan which, by means of condensation, with previously prepared 2- (2-hidroxyethylamine)-2,2-bis-dimethylthio-nitroethylene gives the final product.

Ger. off. DE 2,734,070 describes te procedure for synthesis of Ranitidine, and according to it, Ranitidine is obtained by reaction of N-methyl- 1- (methylthio)-2-nitroethenamine (1) with 2- 5- (dimethylamino)-methyl-2- furanyl-methyl-thio-ethanamine (2). The reaction is carried out by instillation of compound (2) into aqueous suspension of compound (1) at temperature of 45- 50°C for 4-5 hours, reaction continues for 3,5 hours and after that the temperature increases while the reaction mixture is under the reflux for 30 minutes. Removing of water is carried out by azeotropic distillation while products of degradation are formed for the reason of increased temperature, which significantly lowers the yield and quality of obtained Ranitidine.

In ES 496,919 the process for obtaining of alkyl-furan is described, which with scondary amine gives 5-dialkylaminomethyl-2-mercaptomethyl- furan. The compound obtained this way is converted to thioether by reaction with N-alkyl-N'-2-bromethyl-urea, which is finally nitrated.

ES 495,493 recomends the process for obtaining of Ranitidine, where in the first phase 2 (2-furanyl) methyl] thio] ethanoamine reacts with 1,1- bis (methylthio)-2-nitroethen, and in further reaction with methylamine, N- 2- (2-furanyl) methyl] thio] ethyl-N'-methyl-2-nitro-1,1-ethendiamine is obtained, which at the end reacts with formaldehyde and dimethilamine and gives desired product.

There are processes described in literature, according to which Ranitidine can be obtained from the corresponding aldehyde (EP 0055625) or by methylation of corresponding isothiourea, and then by nitration of obtained compound (EP 0055626) or it can be obtained starting from the corresponding thiol and nitro derivative.

In the Swiss patent CH 650,505 synthesis of Ranitidine from cistofur and 1-nitro-2,2-bis- (methylthioethan) is suggested.

According to DOS 74071 Ranitdine is obtained by reaction of 5- (dimethylamino)-methyl-2-furyl-mercaptan with 1-methylamino-1'- (2 chloroethylamino)-2-nitroethan.

Description of solution of the technicalproblem with examples of performance The process according to this invention avoids the defaults of the known processes, primarily of the process given in patent Ger. off. DE 2,734,070. The simpler way for obtaining of N-2 5-(dialkylamino) methyl7-2- furanylymethylythiojethyl/-N-alkyl-2-nitro 1, 1 alkendiamine of formula (I) and their hydrochlorides of formula (II) is provided, as well as usage of cheaper fundamental substances with higher level of their utilization.

In fact, by the process according to the invention, specificly realized is the derivative: N-[2 [[[5-(dimethylamino)methyl]-2-furanyl]methyl]thio]ethyl]-N'- methyl-2-nitro 1, 1 ethendiamine of formula (I-a), with the following characteristics: -structural formula -molecular formula: C13H22N403S -molecular weight: 314,24 -melting point: 67-70°C and its hydrochloride of formula (II-a), with the following characteristics: -structural formula -molecular formula: C13H22N403S x HC1 -molecular weight: 350,86 -melting point: 134-140°C.

The advantages of the suggested process are: -the simplicity of the process of performance, -instillation time is reduced to 20 to 60 minutes, -instillation is carried out at the room temperature, -using of intermediates (III) in the form of hydrochloride, which is more stable than the basic form and more available, -avoiding azeotropic distillation, -good yield and high quality of products, -formed salts which are derived from the starting intermediates do not have any influence on the further course of the reaction as well as on the quality of the final product of formula (II-a).

The suggested process is primarily regarded to the synthesis of Ranitidine where 2-5- (dimethylamino) methyl-2-furanylJmethylJthioJethanamine hydrochloride of formula (III) in excess of 10-30% without prior conversion to base (which simplifies the process of synthesis itself) in presence of aqueous solution of bases such as: NaOH, NH40H, KOH, and primarily NaOH, is instillated at the room temperature, for 20-60 minutes (which is significantly shorter time in comparison to other processes) into the aqueous suspension of the compound N-methyl-I- (methylthio)-2- nitroethenamine of formula (IV) with releasing of methyl mercaptan.

After heating, extraction with an organic solvent is carried out (which avoids removing of water by azeotropic distillation), organic layer is treated with activated char-coal, washed with water (while formed salts derived from the starting intermediates are removed and do not have any influence on the further course of the reaction and on quality of the final product). After that, evaporation, crystalization and filtration are carried out, and finally, wanted compound N-[2[[[5-[(dimethylamino)methyl]-2-furanyl]methyl]thio]ethyl ]-N- methyl-2-nitro 1, 1 ethendiamine of formula (I-a) is obtained.

Hydrochlorination of the compound of formula (I-a) gives desired product N-[2[[[5-[(dimethylamino)methyl]-2-furanyl]methyl]thio]ethyl ]-N'-methyl-2- nitro 1,1 ethendiamine hydrochloride of formula (II-a), which is characterized by good yield, exceptionally high purity and high quality of the product.

The following examples are given for illustration.

Example 1.

N-[2[[[5-[(dimethylamino)methyl]-2-furanyl]methyl]thio]et hyl]-N'-methyl-2- nitro 1,1 ethendiamine of formula (I-a) Solution of 41,33g (0,165 mol) of 2-5- (dimethylamino)-methyl-2- furanyl]methyl]thio]-ethanamine-hydrochloride, 12g (0,3mol) of sodium hydroxide and water, is instillated at the room temperature for 30 minutes into aqueous suspension of 22,2g (0,15 mol) N-methyl-l-(methylthio)-2- nitroethenamine. Reaction is carried out with agitation and heating for 3,5 hours at 45-50°C, afterwards the temperature is elevated and reaction mixture is under the reflux for 30 minutes, get cooled and formed N-2 -5- (dimethylamino) methyly-2-furanyl methylythiovethyly-N-methyl-2-nitro 1, 1 ethendiamine is extracted with chloroform.

Chloroform layer is washed with water, passed through anhydrous sodium sulphate, treated with activated char-coal, filtered and evaporated to the constant mass at 45°C.

Oily base is resuspended at the room temperature in 4-methyl pentane-2- on 1: 2-5 (m/v) and with agitation and cooling, crystalization is carried out.

After filtration and drying, 38,5g of N-2 -5-(dimethylamino) methyl7- 2furanylymethylythiojethyl7-N-methyl-2-nitro 1, 1 ethendiamine of formula (I-a) is obtained, as almost white powder, melting point 67-70°C (yield 74,25%).

Example 2.

N-[2 [[[-5-[(dimethylamino)methyl]-2-furanyl]methyl]thio]ethyl]-N '-methyl-2- nitro 1,1 ethendiamine hydrochloride of formula (II-a) Dissolve 8,169g (0,026 mol) of compound of formula (I-a) in ethanolic solution containing 0,026 equivalents of hydrogen chloride. Formed Ranitidine chloride is precipitated by instillation of ethyl acetate with cooling and agitating.

After crystalization (2 hours) the precipitate is filtered, washed with ethyl acetate and dryed at 50°C. 7,94g (0,0226 mol) of the compound (11-a) is obtained as almost white powder, characterized with high pharmacopoeic purity, with melting point Tt=134-140°C (yield 87,03%).