KR100426534B1 - An improved synthetic method of azelastine - Google Patents

Abstract

The present invention relates to an improved method for synthesizing azelastine, and more particularly to a method for obtaining azelastine with improved yields under milder reaction conditions. In the present invention, the step of obtaining 2- ( p -chlorophenylacetyl) -benzoic acid from phthalic anhydride via 4-chlorobenzalphthalide (first step); Adding acid to 1-methyl-2-pyrrolidinone to obtain 4-methylaminobutyric acid hydrochloride (second step); Obtaining N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine from the second compound (third step); Adding t-butyloxypotassium to the third compound to obtain 1-methyl-hexahydroazin-4-one hydrochloride (fourth step); Adding benzoylhydrazine to the fourth compound to obtain 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine (step 5); And in the method of synthesizing azelastine comprising the step of obtaining azelastine by reacting the first step compound with the fifth step compound (sixth step), in particular, improving the third, fifth and sixth steps. Thus, an improved method for synthesizing azelastine, which greatly improves the yield under simpler and milder reaction conditions, is provided.

Description

Improved Synthesis of Azelastine {AN IMPROVED SYNTHETIC METHOD OF AZELASTINE}

The present invention relates to an improved method for synthesizing azelastine, and more particularly to a method for obtaining azelastine with improved yields under milder reaction conditions.

Azelastine {C ₂₂ H ₂₄ ClN ₃ O; 4-[(4-chlorophenyl) methyl] -2- (hexahydro-1-methyl-1H-azin-4-yl) -1 (2H) -phthalazinone (4-[(4-chlorophenyl) methyl ] -2- (hexahydro-1-methyl-1H-azepin-4-yl) -1 (2H) -phthalazinone)} is a compound having the structure of Formula 1 below.

Azelastine mainly H ₁ having oral activity-histamine receptor antagonist (H ₁ -histaminic receptor antagonist) to a functional, as well as the histamine is a primary causative agent of allergic diseases, asthma, severe Chemistry of allergic diseases such as rhinitis, chronic By suppressing leukotrienes, which acts as an important factor, it is known to have an effect on not only bronchial asthma and allergic rhinitis, but also allergic skin diseases such as dimples, eczema and atopic dermatitis.

The synthesis of azelastine is described by Arch. Pharm, 321 (4), 205-8 (1988); Am. Chem. Soc., 71, 896-900 (1949); J. Am. Chem. Soc., 73, 2371-3 (1951), and other patent documents, such as GB 1,412,377 (1974), USP 5,760,221 (1998), USP 4,841,047 (1989).

The synthesis methods of azelastine shown in each of the literatures and patents have much in common in the synthetic route, but they show differences in specific reactants, intermediates, and reaction methods, and may also be called via the same synthetic route. In addition, there are significant differences in the results such as yield depending on the reaction conditions and the materials used.

An object of the present invention is to provide an optimal method for synthesizing azelastine with improved yield with simpler and milder reaction conditions by selecting an economical and easy synthetic route in terms of reactants or process progress.

In particular, it is an object of the present invention to provide a synthesis method that can significantly lower the production cost compared to the conventional method by increasing the yield of the step of high cost-weight.

In the present invention, a step of obtaining 2- ( p -chlorophenylacetyl) -benzoic acid (2- ( p- chlorophenylacetyl) benzoic acid) from 4-phthalic anhydride via 4-chlorobenzalphthalide ( First step); Adding acid to 1-methyl-2-pyrrolidinone to obtain 4-methylaminobutyric acid hydrochloride (second step); N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine (N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine) was obtained from the second compound. Obtaining (third step); Tert- butylate was added to the third compound to obtain 1-methyl-hexahydroazpin-4-one hydrochloride (1-methyl-hexahydro-azepin-4-one HCl) Fourth step); Benzoylhydrazine was added to the fourth step compound to form 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine (1-benzoyl-2- (hexahydro-1-). obtaining methylazepin-4-yl) hydrizine) (step 5); In the method for synthesizing azelastine comprising the step (6th step) of reacting the first step compound with the fifth step compound to obtain azelastine (azelastine), in particular, the third, fifth and sixth steps Improved method for the synthesis of azelastine, which greatly improves the yield under simpler and more mild reaction conditions, is provided.

Hereinafter, the improved synthesis method of the present invention will be described in each step.

First step

This step is represented by Scheme 1 below.

4-chlorophenylacetic acid and sodium anhydride were added to phthalic anhydride, followed by reaction in a phenyl ether solvent to obtain 4-chlorobenzalphthalide as a reaction intermediate, followed by refluxing with dilute sodium hydroxide aqueous solution, and cooling with aqueous hydrochloric acid. Acidification and recrystallization yields 2- ( p -chlorophenylacetyl) -benzoic acid.

In the present invention, by using phenyl ether as a solvent in this step reaction, the reaction can proceed under more uniform conditions and the crystallization process becomes easier. In the Example, the yield of this step was found to be 78.0%, m.p. of the product was 142 ℃.

2nd step

This step is represented by Scheme 2 below.

After reacting by adding acid to 1-methyl-2-pyrrolidinone at room temperature, toluene is added and distilled again to obtain 4-methylaminobutyric acid hydrochloride. As in the present invention, since toluene is used after the reaction is completed, the water removal effect is increased, and thus recrystallization is facilitated, thereby simplifying the process. In Example, the yield of this step was found to be 89.0%, m.p. was 123.4 ~ 124.4 ℃.

3rd step

This step is represented by Scheme 3 below.

Ethanol was added to 4-methylaminobutyric acid hydrochloride, which is the second step compound, and 3 equivalents of sodium metal was added thereto, and ethyl acrylate was reacted at room temperature to give N- (2-carbethoxyethyl) -N- ( 3-carbethoxypropyl) methylamine is obtained. In the present invention, by reacting the third step compound with 3 equivalents of metal sodium and ethyl acrylate, it was possible to shorten the reaction process in one step and to proceed the reaction under milder conditions. In the Example, the yield of this step was 92.0%.

This step is described in J. Org. Compared to the method described in Chem ., 19 (1954, p. 1855-1861), the method in the literature first reacts methylamine with an alcohol solution of ethyl methacrylate to give ethyl 3-methylaminopropanoate (I). And then reacted with ethyl acrylate to obtain methyl (2-ethoxycarbonylethyl) (2-ethoxycarbonylpropyl) amine (II), which proceeds in two steps.

4th step

This step is represented by Scheme 4 below.

In this step, N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine, which is the third step compound, and t-butyloxypotassium are mixed in a reaction solution using benzene and toluene together. Reaction gives 1-methyl-hexahydroazin-4-one hydrochloride. When benzene and toluene are used together, ethanol is also removed when the benzene is distilled, so ethanol is efficiently removed without a separate mechanism for distilling ethanol. In this step, there was no improvement in yield compared to the conventional method, but the process was simplified and the progress was advantageous. The yield of this step in the Example was 60.8%, m.p. was 167.4 ~ 168.3 ℃.

5th step

This step is represented by Scheme 5 below.

This step can be performed in the following two ways.

5-A step

Reaction of benzoylhydrazine with 1-methyl-hexahydroazin-4-one, which is the fourth step compound, at room temperature, yields 2-benzoyl-1- (hexahydro-1-methyl-1H-ase as a mixture without recrystallization. Pin-4yl) -hydrazine is obtained. The yield of the mixture was at least 100%, and in this example the yield of this step was 102%.

5-B step

The benzoylhydrazine was reacted with 1-methyl-hexahydroazin-4-one, which is the fourth step compound, at room temperature, and 2-benzoyl-1- (hexahydro-1-methyl-1H- was purified using column chromatography without recrystallization. Azepin-4yl) -hydrazine is obtained. The yield of this step was 85.0% or more, 88.0% in the Example.

Comparing this step with patent USP 4,841,047 (1989), which has a similar reaction pathway, the patent discloses that N-benzylazine-on- (4) -hydrochloride and benzoyl hydrazine are mixed with methanol and then concentrated and recrystallized. Through the process, 1-benzoyl-2- (hexahydro-1-benzylazin-4yl) -hydrazine is obtained, and the yield is very low at 35.0% (mp: 176 to 180 ° C).

6th step

This step is represented by Scheme 6 below.

2- ( p -chlorophenylacetyl) -benzoic acid obtained in step 1 was added to 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine obtained in step 5. The reaction is carried out at pH 7, 45 ° C. in equivalent weight to obtain azelastine hydrochloride in high yield. In the case of proceeding step 6 through 5-A step as a starting material, 1-methyl-hexahydroazin-4-one, the fourth step compound, the integrated yield of the two steps is 45.7% and step 6 through 5-B. In the case of proceeding, the integrated yield of two steps was 44.0%, and mp was 223∼224 ° C.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the scope of the present invention is not limited by the following examples, and those skilled in the art to which the present invention pertains should be within the equivalent scope of the technical concept of the present invention and the claims to be described below. Of course, various modifications and variations are possible.

Example 1

First step: 2- ( p -Chlorophenylacetyl) -benzoic acid

169.0 g (1.141 mol) of phthalic anhydride, 214.1 g (1.255 mol) of 4-chlorophenyl acetic acid, 0.9 g of sodium acetate anhydride, and 575 g of phenyl ether were reacted at 245-250 degreeC for 5 hours. After completion of the reaction, the reaction mixture was recrystallized from 1,278 g of hexane, filtered and dried to obtain 4-chlorobenzalphthalide as an intermediate, and then diluted with sodium hydroxide aqueous solution and refluxed for 2 hours. After cooling, the resulting crystals were acidified with an aqueous solution of hydrochloric acid, and the resulting crystals were filtered under reduced pressure, washed with water and dried to obtain a crude product, recrystallized with toluene, and then dried in vacuo to give 241.3 g (879) of 2- ( p -chlorophenylacetyl) -benzoic acid. Mole). Yield: 78.0%, mp: 142 ° C.

Second Step: Preparation of 4-methylaminobutyric acid hydrochloride

268.8 g of concentrated hydrochloric acid was added to 123.7 g (1.248 mol) of 1-methyl-2-pyrrolidinone at room temperature, followed by heating under reflux for one night. After completion of the reaction, the reaction mixture was concentrated under reduced pressure, and then toluene was added and distilled again. 385 g of acetone was added to the residue, and the residue was filtered and dried at room temperature to obtain 170.6 g (1.111 mol) of 4-methylaminobutyric acid hydrochloride. Yield: 89.0%, m. P .: 123.4-124.4 ° C.

Third Step: Preparation of N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine

1,012 g of ethanol was added to 170.6 g (1.111 mol) of 4-methylaminobutyric acid hydrochloride, and 76.7 g (3.336 mol) of sodium metal was added thereto. 116.8 g (1.167 mol) of ethyl acrylate was added dropwise to the reaction mixture, followed by stirring at room temperature. After completion of the reaction, concentrated sulfuric acid was added and heated for 3 hours. After cooling, the mixture was basified, extracted with dichloromethane, dehydrated with anhydrous magnesium sulfate, and distilled under reduced pressure to give 250.7 g of N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine. 1.022 mol). Yield: 92.0%.

Fourth Step: Preparation of 1-methyl-hexahydroazin-4-one hydrochloride

149.7 g (1.334 mol) of t-butyloxy potassium was added to the reactor, and 2,557 g of anhydrous toluene was added thereto, followed by heating to reflux. A solution of 218.0 g (0.889 mole) of N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine and 923 g of anhydrous benzene was added dropwise to the reactor under nitrogen for 3 hours. The reaction mixture in the reactor was further reacted for 0.5 hours. 1,013 g hydrochloric acid was added to the reaction mixture and the mixture was separated. The obtained acid solution was heated to reflux, basified with sodium hydroxide, extracted with dichloromethane, and dehydrated with anhydrous magnesium sulfate. After distillation under reduced pressure, the solution was dissolved in 2-propanol, passed through hydrochloric acid gas to obtain colorless crystals, and then filtered and dried to obtain 88.4 g (0.540 mol) of 1-methyl-hexahydroazin-4-one hydrochloride. Yield: 60.8%, m.p .: 167.4-168.3 ° C.

Step 5-A: Preparation of 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine

88.4 g (0.540 mole) of 1-methyl-hexahydroazin-4-one hydrochloride was added to the reactor at room temperature, dissolved in 304 g of methanol, and 78.6 g (0.575 mole) of benzoylhydrazine was added thereto. 29.2 g of potassium hydroxide was slowly added dropwise while maintaining the reactor temperature at 4 ° C and stirred at room temperature. After completion of the reaction, 37.9 g of sodium borohydride was added at 4 ° C. for 1 hour, followed by stirring at room temperature. Methanol was distilled and water was added, followed by extraction with dichloromethane, dehydrated with anhydrous magnesium sulfate, filtered and concentrated to 2-benzoyl-1- (hexahydro-1-methyl-1H-azepin-4yl) -hydro 136.3 g (0.551 mol) of lysine were obtained. Yield of mixture: 102%

Step 5-B: Preparation of 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine

88.4 g (0.540 mole) of 1-methyl-hexahydroazin-4-one hydrochloride was added to the reactor at room temperature, dissolved in 304 g of methanol, and 78.6 g (0.575 mole) of benzoylhydrazine was added thereto. 29.2 g of potassium hydroxide was added and stirred at room temperature. After completion of the reaction, 37.9 g of sodium borohydride was added for 1 hour, followed by stirring at room temperature. Methanol was distilled and water was added, followed by extraction with dichloromethane, dehydration with anhydrous magnesium sulfate, filtration and concentration, then 2-benzoyl-1- (I) using column chromatography (EA / Hexane = 2/1 MeOH). 117.6 g (0.475 mol) of hexahydro-1-methyl-1H-azin-4yl) -hydrazine were obtained. Yield: 88.0%

Step 6: Preparation of Azelastine Hydrochloride

136.3 g (0.551 mol) of 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine obtained in step 5-A or 117.6 g (0.475 mol) obtained in step 5-B ) Was added to the aqueous solution of hydrochloric acid, heated to reflux for 5 hours, distilled under reduced pressure, and distilled again with 75 g of methanol. 167 g of methanol was added to the residue, and 256.2 g (0.823 mol) of 2- ( p -chloroacetyl) -benzoic acid was added thereto, followed by neutralization by adding 71.1 g of potassium hydroxide to the reaction solution (pH 7). ) To react. The solvent was concentrated, dissolved in water, basified with 2N sodium hydroxide, crystallized, filtered and dried in vacuo. The dried crude product was dissolved in acetone at room temperature and acidified with 2-propanol saturated hydrochloric acid. The product was filtered and dried in vacuo at room temperature to obtain 103.3 g (0.247 mole) of azelastine hydrochloride via 5-A process and 99.4 g (0.238 mole) through 5-B process. In the case of proceeding to the sixth step through 5-A step as a starting material, 1-methyl-hexahydroazin-4-one as the fourth step compound, the integrated yield of the two steps is 45.7% and the 5-B step is performed. In the case of the sixth step, the combined yield of the two steps was 44.0% and mp was 223∼224 ° C.

Example 2

In the sixth step, it was the same as in Example 1 except that the pH was 4, the amount of the first step compound was changed to 1 equivalent and the reaction temperature was heated to reflux. Yield 10.0%.

Example 3

In the sixth step, it was the same as in Example 1 except that the pH was 6, the amount of the first step compound was changed to 1 equivalent and the reaction temperature was heated to reflux. Yield: 28.0%.

Example 4

In the sixth step, it was the same as in Example 1 except for changing the pH to 8, changing the amount of the first step compound to one equivalent to the fifth step compound, and heating and refluxing the reaction temperature. Yield: 30.0%.

Example 5

In the sixth step, it was the same as in Example 1 except that the pH was set to 10, the amount of the first step compound to the fifth step compound was changed to 1 equivalent, and the reaction temperature was heated to reflux. No reaction.

Example 6

In the sixth step, it was the same as in Example 1 except for changing the amount of the first step compound to one equivalent for the fifth step compound. Yield 64.0%.

The results of Examples 1 to 6 are compared and shown in Table 1 below.

Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 pH 7 4 6 8 10 7 Temperature (℃) 45 ℃ reflux reflux reflux reflux 45 ℃ Equivalent Use of Step 1 Compound 1.5 equivalent 1 equivalent 1 equivalent 1 equivalent 1 equivalent 1 equivalent yield(%) 75.0% 10.0% 28.0% 30.0% N.R. 64.0%

As can be seen through the above examples, according to the present invention, azelastine can be synthesized in a yield more than twice higher than that of the conventional method under easier and mild reaction conditions. By increasing the yield of the sixth step, the production cost can be significantly reduced.

Claims (6)

Obtaining 2- ( p -chlorophenylacetyl) -benzoic acid from phthalic anhydride via 4-chlorobenzalphthalide (first step); Adding acid to 1-methyl-2-pyrrolidinone to obtain 4-methylaminobutyric acid (second step); Obtaining N- (2-carbethoxyethyl) -N- (3-carbethoxypropyl) methylamine from the second compound (third step); Adding t-butyloxypotassium to the third compound to obtain 1-methyl-hexahydroazin-4-one hydrochloride (fourth step); Adding benzoylhydrazine to the fourth compound to obtain 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine (step 5); In the method of synthesizing azelastine comprising the step of obtaining azelastine (sixth step) by reacting the first step compound and the fifth step compound, In the third step, the reaction is carried out in one step by reacting 3 equivalents of metal sodium with ethyl acrylate in the second step compound; The fifth step proceeds with the reaction at room temperature, and 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine in a yield of 85% or more using column chromatography without recrystallization. To obtain 2-benzoyl-1- (hexahydro-1-methyl-1H-azin-4yl) -hydrazine in the form of a mixture having a yield of 100% or more without recrystallization, and then proceed to step 6; The sixth step is the improved synthesis method of azelastine, characterized in that the reaction of the first step compound in 1.5 equivalents, pH 7, 45 ℃. The method according to claim 1, The first step is an improved method for synthesizing azelastine, characterized in that 4-chlorophenylacetic acid and sodium acetate are reacted with phthalic anhydride using phenylether as a solvent. The method according to claim 1, The second step is an improved synthesis method of azelastine, characterized in that toluene is added and distilled to facilitate recrystallization after the reaction by adding acid to 1-methyl-2-pyrrolidinone. The method according to claim 1, The fourth step is an improved synthesis method of azelastine, characterized in that benzene and toluene are used together as a reaction solution to facilitate the removal of by-product ethanol. delete delete