3-(3h-Pyrazol-3-One)-2-(Disubstituted Aminomethyl)indoles and Pharmaceutical Preparations

The present invention relates to new 3-substituted-2-(dialkylaminomethyl)indoles. More particularly, the invention relates to new compounds of the formula ##STR1## and acid addition salts thereof, and to a method for production of the foregoing compounds; where R.sup.1 and R.sup.2 are lower alkyl groups, R.sup.3 is hydrogen, a lower alkyl group, halogen or a lower alkoxy group and A is C(C.sub.6 H.sub.5).sub.2 CN or ##STR2## where R.sup.4 is lower alkyl. The preferred compounds are those wherein R.sup.3 is hydrogen, R.sup.1 and R.sup.4 are methyl and R.sup.2 is methyl or butyl.

The term "lower alkyl" is intended to mean an alkyl group of from one to six carbon atoms, such as methyl, ethyl, butyl, and isopentyl and the term "lower alkoxy" is intended to mean lower alkyl-O--. The term "acid addition salt" is intended to mean a salt such as the hydrochloride, sulfate, acetate, benzoate, citrate, hydrobromide, nitrate, etc. preferably the pharmaceutically acceptable salts such as the hydrochloride, sulfate, citrate, etc.

The term "halogen" is intended to mean chlorine, fluorine, iodine or bromine.

In accordance with the invention, the foregoing compounds of formula I can be prepared by reacting a compound of the formula ##STR3## with the anion of a compound of the formulae ##STR4## wherein R.sup.1, R.sup.2, R.sup.3 and R.sup.4 are as previously defined in formula I and X is lower alkylsulfate, bromine, chlorine or iodine, preferably iodine. The anion is formed in dimethylformamide using about an equivalent molar amount of sodium hydride. While equamolar quantities of the reactants may be employed, a small excess of either component may be used. This reaction may be carried out in an inert polar solvent such as a dimethylformamide, dimethylacetamide or mixtures thereof at temperatures of from about 50.degree. C. to about 125.degree. C. for periods of from fifteen minutes up to two days. The reaction is preferably conducted on a steam bath for a period of about one hour. The addition of an acid, such as hydrochloric acid converts the above formed free base to its acid addition salt.

Compounds of the formula II are prepared by reacting a compound of the formula ##STR5## with a compound of the formula

wherein R.sup.1, R.sup.2 and R.sup.3 are as previously defined. The reaction is conducted in a polar solvent. When employing an alkyl iodide, a rapid reaction takes place at room temperature in an acetone solvent; however, using alkyl chlorides and bromides usually requires higher reaction temperatures utilizing pressure vessels and reaction times of up to twenty-four hours.

Compounds of the formula III are prepared by reducing a compound of the formula ##STR6## according to procedures reported in the Journal of Organic Chemistry 25(1960)1133 which is incorporated by reference.

The compounds of the invention are new chemical compounds of value as central nervous system depressants. More specifically, the compounds when administered intraperitoneally to rodents, such as mice, at a dose of 100 mg./kg., sedation is produced.

The invention is further illustrated by the following examples.

A solution of 2-n-Butyl-1,2,3,4-tetrahydropyrrolo[3,4-b]indole, 8.6 g., and methyl iodide, 2.6 ml. in dimethylformamide is stirred fifteen minutes, and then added all at once to a solution of the anion of the pyrazolone, prepared from 6.96 g. of 2-phenyl-5-methyl-3H-pyrazol-3-one and 2.0 g. fifty percent sodium hydride in dimethylformamide at 10.degree.-20.degree. C. The mixture is heated on a steam bath for one hour, then stirred at room temperature for sixteen hours. The reaction mixture is next poured into water, precipitating the product, 8.6 g., m.p. about 180.degree.-200.degree. with decomposition. Recrystallization from methanol gives 6.3 g., m.p. 195.degree.-200.degree. with decomposition.

The above named compound is obtained by utilizing the procedure of Example 1 after substituting in the place of 2-n-butyl-1,2,3,4-tetrahydropyrrolo[3,4-b]indole methiodide, the following compound; 2-methyl-1,2,3,4-tetrahydropyrrolo[3,4-b]indole methiodide.

A slurry of 2-n-butyl-1,2,3,4-tetrahydropyrrolo[3,4-b]indole, 4.3 g., in dimethylformamide, 30 ml. is treated with methyl iodide, 4.3 g. The solids dissolve and the solution warms. After one-half hour, excess methyl iodide is removed in vacno. Meanwhile, a solution of the anion of diphenylacetonitrile in tetrahydrofuran is prepared by reaction of 3.9 g. of diphenylacetonitrile with 0.9 g. of fifty-seven percent sodium hydride. The methiodide solution is then added rapidly to the anion. A solid precipitates with the color changing from purple to light brown. After stirring twenty-four hours at room temperature, the mixture is poured into water and extracted with ethyl ether to give 8.1 g. of crude product. Recrystallization from methanol returns 5.1 g. of product, m.p. 122.degree.-125.degree.. A second crop is also obtained, 3.1 g., m.p. 115.degree.-119.degree..

The above named compound is obtained by utilizing the procedure of Example 3 after substituting in the place of 2-n-butyl-1,2,3,4-tetrahydropyrrolo[3,4-b]indole methiodide, the following compound; 2-methyl-1,2,3,4-tetrahydropyrrolo[3,4-b]-indole methiodide.

The hydrochloride salt of the above named compound is obtained by dissolving said compound in isopropanol and adding to it an ether solution of hydrogen chloride.

Methyl iodide, 37 ml., is added in a single portion to a warm, vigorously stirred solution of 2-methyl-1,2,3,4-tetrahydropyrrolo[3,4-b]indole, 51.6 g., in dry acetone, 700 ml. A heavy crystalline precipitate of the title compound starts to separate almost immediately, and after 15 minutes of stirring is collected and washed thoroughly with additional acetone, giving 80-85 g. The product is essentially pure, and can be used directly.

2-Methyl-1,4-dihydropyrrolo[3,4-b]indol-3(2H)-one, 1.7 g., and LiAlH.sub.4, 2.3 g., are heated in refluxing dioxane, 300 ml., for five hours. The mixture is cooled and carefully hydrolyzed with excess water. Solids are filtered away and washed with dioxane, after which the filtrate is concentrated to dryness giving 1.4 g. of a crude brown product, m.p. 110.degree.-120.degree. C. Since the crude product is sensitive to air oxidation (darkens rapidly on standing), it is not further purified before methiodide preparation.

1-Methyl-4-carbomethoxy-2,3-dioxopyrrolidine, 8.5 g., is heated on the steam bath for about 45 minutes to one hour in 150 ml. of a twenty percent aqueous hydrochloric acid solution. The resulting solution is cooled to room temperature and filtered. Sodium acetate is next added to neutralize the mixture to a pH of 4 to 5. Water is added as necessary to keep most of the solids in solution. Phenylhydrazine, 5.9 g., is then washed into the solution with a little methanol. A solid material precipitates immediately and is collected and washed with water. This crude phenylhydrazone is taken up in 100 ml. warm acetic acid and treated with 30 ml. concentrate hydrochloric acid. A vigorous reaction ensued after which the mixture is refluxed for 10 minutes. Cooling precipitates crude title compound, 16.7 g., m.p. about 300.degree. (dec.). Recrystallization from a large volume of methanol raised the m.p. to 303.degree.-6.degree. (dec.).

A slurry of 4.3 g. of 2-n-butyl-1,2,3,4-tetrahydropyrrolo[3,4-b]indole in dimethylformamide, 30 ml., is treated with methyl iodide, 4.3 g. After thirty minutes excess methyl iodide is removed using reduced pressure.

2-n-Butyl-1,4-dihydropyrrolo[3,4-b]indol-3(2H)-one, 20 g., in dry tetrahydrofuran, 400 ml., is added slowly to a slurry of LiAlH.sub.4, 14 g., in tetrahydrofuran, 250 ml. After refluxing twenty hours, the reaction mixture is hydrolyzed with 30 ml. of water, and filtered. After the solvent is removed, one obtains 20.1 g. of a reddish-brown solid. Recrystallization from methanol, 200 ml., gives 11 g. of the title compound, m.p. 151.degree.-2.degree..

1-n-Butyl-4-carbomethoxy-2,3-dioxopyrrolidine, 107 g., [Southwick and Owellen, J. Org. Chem. 25(1960)1133]is heated to boiling in a mixture of 600 ml. of a twenty percent aqueous hydrochloric acid solution and about 100 ml. of ninty-five percent ethanol. Solids dissolved in about ten minutes to give a yellow solution. After one hour of heating, the flask is cooled to about room temperature. Sodium acetate is then added to neutralize the reaction mixture to a pH of 4-5. In addition about 500 ml. of water is added during the neutralization to insure that most materials will remain in solution. Phenylhydrazine, 54 g., is then washed into the stirred mixture with methanol, 20 ml. The phenyl hydrazone starts to separate immediately, and is collected after 10 minutes of cooling and stirring. The material is dissolved in 200 ml. of acetic acid at 65.degree. and treated with 100 ml. of concentrated hydrochloric acid. A strong exotherm takes the temperature up to about 110.degree. which causes vigorous refluxing. Filtration of the cooled slurry yields 78 g. of the title compound, m.p. 215.degree.-218.degree. sinters at 210.degree.. Dilution of the filtrate with water gives additional product, 7 g., m.p. after recrystallization from methanol: 216.degree.-218.degree..