Process for Preparing Substituted 1,2,4-Triazole Derivatives

This invention relates to new 1-alkyl-3,5-disubstituted-1,2,4-triazole derivatives of following formula I and to processes for their manufacture: ##STR2## wherein R may represent phenyl; phenyl substituted by a radical selected from (C.sub.1-4) alkyl, e.g. methyl, ethyl, propyl, isopropyl, butyl, sec.butyl, isobutyl or tert.-butyl, (C.sub.1-4)alkoxy, e.g. methoxy, ethoxy, propoxy, butoxy, isobutyloxy or tert.-butoxy, fluoro, chloro, bromo, nitro, amino, cyano, carbamoyl, carboxy, hydroxymethyl, methylenedioxy and trifluoromethyl; dichlorophenyl, dimethoxyphenyl; 3,4,5-trimethoxyphenyl;

R.sub.1 may represent phenyl; phenyl substituted by a radical selected from (C.sub.1-4)alkyl as above defined, (C.sub.1-4)alkoxy as above defined, fluoro, chloro, bromo, hydroxymethyl, (C.sub.2-4)aliphatic acyloxy-methyl, e.g. acetoxymethyl, propionyloxymethyl or butyryloxymethyl, carbamoyloxymethyl, bromomethyl and dimethylaminomethyl; dimethylphenyl; dimethoxyphenyl; phenyl contemporaneously substituted by o-hydroxymethyl and chloro;

R.sub.2 represents a (C.sub.1-4)alkyl group as above defined; with the proviso that R and R.sub.1 cannot simultaneously represent phenyl; with the further proviso that, when R is phenyl, R.sub.1 cannot be p-chlorophenyl.

The compounds of the invention have CNS depressant utility. They are especially useful as sedative and hypnotics. Some of the compounds of the invention are also useful as anxiety relieving means.

A preferred group of compounds comprises those compounds of formula I wherein R and R.sub.2 are defined as above and R.sub.1 is the radical ##STR3## wherein R.sub.3 may represent hydrogen or hydroxy.

A most preferred group of compounds comprises those compounds of formula I wherein R represents phenyl; phenyl substituted by a radical selected from methyl, methoxy, fluoro, chloro, nitro and methylenedioxy; dichlorophenyl; dimethoxyphenyl or 3,4,5-trimethoxyphenyl;

R.sub.1 is the radical ##STR4## wherein R.sub.3 is hydroxy, and R.sub.2 stands for a methyl group. A second most preferred group of compounds comprises those compounds of formula I wherein R represents phenyl; phenyl substituted by a radical selected from methyl, methoxy, trifluoromethyl, methylenedioxy, chloro and amino; dimethoxyphenyl or 3,4,5-trimethoxyphenyl,

R.sub.1 is the radical ##STR5## wherein R.sub.3 represents hydrogen and R.sub.2 stands for a methyl radical.

A general method for preparing the 1,2,4-triazoles of this invention comprises either reacting a compound of formula ##STR6## with a compound of formula

or reacting a compound of formula ##STR7## with a compound of formula

in the above formulas II thru V the radicals R, R.sub.1 and R.sub.2 have the previously indicated meanings, CX is a functional group selected from carboxy, dithiocarboxy, carbonyl halide, carboxy anhydride, orthoester, imidate, thioimidate, imidoyl halide, amidino and cyano, Y is NH, and, when a compound R-CX is employed wherein the group CX contains a nitrogen atom, it represents oxygen or sulfur.

The process essentially consists in a condensation reaction, during which, depending on the nature of the reacting groups CX and Y, water, hydrogen sulfide, hydrogen halide, ammonia, alkanols, carboxylic acids or mixtures thereof are formed as by-products. The reaction is illustrated by the following scheme: ##STR8## A tipical method for carrying out the condensation reaction involves heating the pair of reagents of formulas II and III or IV and V in the absence of solvent at a temperature of from about 80.degree. to about 150.degree. C. for several hours. An excess of the compound R.sub.1 CX or R--CX may be advantageously employed to speed up the reaction. In those instances where the two components can not be melted without decomposition, a high boiling inert organic solvent may be used, such, for instance, xylene, halogenated aromatic hydrocarbons, N,N-dimethylformamide and the like. Catalytic amounts of acids such as p-toluenesulfonic acid or hydrogen halides, as well as imidate or amidine acid salts may be advantageously added to speed up the cyclization rate.

The foregoing cyclization reaction may also be effected in two steps when the group CX in the compounds of formulas III and V corresponds to an acyl halide. Thus, for instance, a molecular amount of 3-chlorobenzimidic acid 2-methylhydrazide, i.e., the compound of formula (II) wherein R is 3- chlorophenyl, R.sub.2 is methyl and Y is NH, is stirred for 15-25 hours at room temperature in an halogenated lower hydrocarbon solution and in the presence of an excess over the equimolecular proportion of a tertiary organic base, with a molecular amount of 2,6-dimethoxybenzoyl chloride, i.e., the compound of formula (III) wherein R.sub.1 is 2,6-dimethoxyphenyl and CX corresponds to carbonyl chloride. After washing with aqueous NaHCO.sub.3 and evaporating the solvent, the intermediate 2-methyl-2-(2,6-dimethoxybenzoyl)hydrazine of 3-chlorobenzimidic acid is obtained. This latter compound is cyclized by heating in an inert organic solvent at a temperature from about 80.degree. to about 150.degree. C. for several hours. A catalytic amount of a base such as an alkali metal hydroxide or an alkali metal alkoxide preferably sodium methoxide or ethoxide, may be used to improve the reaction rate. In some case, the obtained 1,2,4-triazole can be further transformed by generally known chemical reactions into another derivative which is encompassed by the general formula (I). As an example, the phenyl radicals R and R.sub.1 may be chemically modified by introducing new substituents or by transforming a pre-existing substituent into a different functional group. If a triazole of formula I is desired wherein R.sub.1 represents phenyl substituted by an o-hydroxymethyl groups, or phenyl contemporaneously substituted by o-hydroxymethyl and chloro, a further suitable method for preparing the inventive compounds involves a novel rearrangement of the hydrazones of 4-hydrazino-1H-2,3-benzoxazines of formula VI, as indicated by the following scheme: ##STR9## wherein R and R.sub.2 are as above defined and R.sub.5 is hydrogen or chloro.

It is quite apparent that, in this case, further chemical transformations of the obtained compounds are possible. In particular, the o-hydroxymethyl group may be transformed by known chemical procedures such as, for instance, hydrogenation, substitution, acylation and the like, into another functional group such as methyl, bromomethyl, dimethylaminomethyl, (C.sub.2-4)aliphatic acyloxy-methyl or carbamoyloxymethyl. According to the novel rearrangement process, hydrazones of benzaldehyde or substituted benzaldehydes with 4-hydrazino-1H-2,3-benzoxazines, when heated in an organic solvent which is advantageously selected from lower alkanols in the presence of an acidic catalyst, such as for instance, hydrogen chloride or p-toluene sulfonic acid, rearrange to 1,2,4-triazoles.

The final compounds are easily recovered by filtration or by evaporation of the solvent. The starting hydrazones are prepared according to the procedure described in British Pat. No. 1,227,490. The hydrazones which undergo the rearrangement may also be used in a crude state without any particular purification.

As stated before, the compounds of the invention have CNS depressant utility. More exactly, the compounds of Examples 1,2,3,5-10, 14, 31(42), 32(56), 34, 35 and 45(55) are useful as sedatives and hypnotics. These pharmacological properties were ascertained by following the operative scheme and the manipulation procedure described by S. Irwin in Psychopharmacologia (Berl.), 13, 222, 1968. Especially, there were studied the biological effects of the compounds on two of the parameters which are closely related to the above properties, namely the "spontaneous activity" and the "righting reflex". The effects of the compounds on these two parameters were expressed as ED.sub.50 values ie., the amount of compound tested which reduces the spontaneous activity and righting reflux scores of test animals to 50% of those of the controls. The scores are the same as those reported by S. Irwin in the cited paper. For each compound it was also determined the minimal dosis which produces complete hypnosis of the test animals (MHD).

The obtained results are summarized in the following table, which also reports the toxicities of the tested substances, expressed as LD.sub.50 values. For comparison purposes, also the activity of two known compounds was determined, The known compounds are 1-methyl-3,5-diphenyl-1,2,4-triazole (Compound A, Atkinson et al. Journ. Chem. Soc., 1954, 141, 1954) and 1-methyl-3-phenyl-5-(p-chlorophenyl)-1,2,4-triazole (Compound B, Huisgen et al., Journ. Org. Chem., 24, 892, 1959).

The compounds of Examples 34 and 45(55) are also useful as anxiety relieving means. This property was investigated on the basis of the secondary response avoidance test, which was performed as described by G. Maffii, Journ. Pharm. Pharmacol., 11, 192, 1959. It has been found that the compounds of Examples 34 and 45(55) display a remarkable antianxiety effect in rats at a dose of 20 mg/kg i.p.

While the preferred routes of administration of these compounds are by mouth or parenterally, other routes may be useful employed. For oral administration the substances are embodied in pharmaceutical dosage forms such as tablets, capsules, elixirs, solution and the like. The dosage unit may contain the usual excipients such as, for example, starch, gums, alcohols, sugars, fatty acids, etc. For parenteral administration, the compounds are administered in the form of aqueous solution, admixed with conventional antioxidant, preservative, chelating and buffering agents such as, for examples, sodium formaldehyde sulfoxylate, benzyl alcohol, ethylenediaminetetraacetic acid derivatives, sodium acetate, etc. The daily dosage range is from about 1 to about 50 mg/kg of body weight, preferably administered in divided doses.

The following non-limitative examples describe in detail representative compounds of this invention and methods for their preparation.

A suspension of 1.2 g. of 4-(2-benzylidene-1-methylhydrazino)-1H-2,3-benzoxazine in 12 ml. of ethanol and 12 ml. of aqueous 5% HCl is heated on a water bath for three hours. The ethanol is removed by distillation and the residue, neutralized with aqueous NaHCO.sub.3, is cooled to about 0.degree. C. The precipitate is filtered and crystallized from ethanol. M.p. 122.degree. C. Yield 96%.

Pursuant to the method described in Example 1, the following compounds are prepared:

0.5 Grams of 5-(2-hydroxymethylphenyl)-1-methyl-3-(4-nitrophenyl)-1,2,4-triazole are heated on a steam bath for 3 hours with 5 ml. of acetic anhydride and the residue obtained after evaporation to dryness is crystallized from 20 ml. of ethanol. Yield 88%. M.p. 126.degree.-127.degree. C.

Dry halogen chloride is bubbled for 30 minutes at about 0.degree.-5.degree. C. into a suspension of 2.8 g. of 1-methyl-3-(o-tolyl)-5-(2-hydroxymethylphenyl)-1,2,4-triazole and 1.82 g. of sodium cyanate in 50 ml. of chloroform. After standing for 15 minutes at room temperature, the solution is evaporated and the residue dissolved in diethyl ether. After washing the ether solution with aqueous sodium bicarbonate and drying over Na.sub.2 SO.sub.4, the solvent is evaporated and the crude product is crystallized from benzene. M.p. 126.degree.-128.degree. C. Yield 68%.

According to the procedure described in Example 19, the following compounds are prepared:

To 300 ml. of dichloromethane saturated with dry hydrogen bromide 7 g. of 1-methyl-3-phenyl-5-(2-hydroxymethylphenyl)-1,2,4-triazole are added. The solution is allowed to stand at room temperature for a night and after washing with aqueous sodium bicarbonate and then with water it is dried over sodium sulfate. Evaporation of the solvent and crystallization from hexane afford the title compound. M.p. 83.degree.-85.degree. C. Yield 84%.

By operating as in Example 25, the following compounds are prepared starting from their corresponding 2-hydroxymethyl derivatives:

(26) 5-(2-bromomethylphenyl)-1-methyl-3-(m-tolyl)-1,2,4-triazole. M.p. 116.degree.-117.degree. C. Yield 85%.

(27) 5-(2-bromomethylphenyl)-1-methyl-3-(3-chlorophenyl)-1,2,4-triazole. M.p. 126.degree.-128.degree. C. Yield 71%.

(28) 5-(2-bromomethylphenyl)-1-methyl-3-(4-nitrophenyl)-1,2,4-triazole. M.p. 285.degree. C. Yield 42%.

2.81 Grams of 1-methyl-3-(o-tolyl)-5-(2-hydroxymethylphenyl)-1,2,4-triazole and 0.365 g. of dry hydrogen chloride in 100 ml. of ethanol are hydrogenated in the presence of 1 g. of 10% palladiated charcoal as a catalyst.

After taking up of one molecular amount of hydrogen, the catalyst is filtered off and the filtrate evaporated to dryness. The residue is taken up with a NaHCO.sub.3 solution and extracted with diethyl ether; after drying and evaporation of the solvent, the title compound is distilled at 170.degree. C./0.08 mm Hg. Yield 76%.

Pursuant to the procedure described in Example 29 and starting from their corresponding 2-hydroxymethylphenyl compounds, the following derivatives are prepared:

(30) 1-Methyl-3-(o-tolyl)-5-phenyl-1,2,4-triazole. B.p. 170.degree. C./0.1 mm Hg. Yield 80%.

(31) 1-Methyl-5-(o-tolyl)-3-phenyl-1,2,4-triazole, B.p. 160.degree. C./0.1 mm Hg. Yield 76%.

(32) 1-Methyl-3-(m-tolyl)-5-(o-tolyl)-1,2,4-triazole. M.p. 80.degree.-81.degree. C. Yield 86%.

(33) 1-Methyl-3-(p-tolyl)-5-(o-tolyl)-1,2,4-triazole. M.p. 139.degree.-140.degree. C. Yield 78%.

(34) 1-Methyl-3-(3-aminophenyl)-5-(o-tolyl)-1,2,4-triazole. M.p. 128.degree.-130.degree. C. Yield 51%. In this case the compound is prepared by using as a starting material 1-methyl-3-(3-nitrophenyl)-5-(2-hydroxymethylphenyl)-1,2,4-triazole and hydrogenating in a single step the nitro and the hydroxymethyl group.

(35) 1-Methyl-3-(3-methoxyphenyl)-5-(o-tolyl)-1,2,4-triazole B.p. 190.degree. C./0.03 mm Hg. Yield 79%.

(36) 1-Methyl-3-(3,5-dimethoxyphenyl)-5-(o-tolyl)-1,2,4-triazole. M.p. 104.degree.-105.degree. C. Yield 72%.

(37) 1-Methyl-3-(3,4-methylenedioxyphenyl)-5-(o-tolyl)-1,2,4-triazole. M.p. 96.degree.-97.degree. C. Yield 63%.

(38) 1-Methyl-3-(3,4,5-trimethoxyphenyl)-5-(o-tolyl)-1,2,4-triazole. M.p. 175.degree.-176.degree. C. Yield 70%.

To a solution of 4. g. of 1-methyl-3-(3-chlorophenyl)-5-(2-bromomethylphenyl)-1,2,4-triazole in 50 ml. of anhydrous benzene, 8.8 ml. of a benzene solution containing 20% of dimethylamine are added maintaining the temperature of about 5.degree.-10.degree. C. The mixture was maintained under stirring for 16 hours and then washed with 10% sodium hydroxide and with an aqueous solution of sodium chloride. The organic solution is dried over sodium sulfate and then evaporated. The crude product is purified by distillation at 175.degree. C./0.07 mm Hg. Yield 86%.

The following compounds are prepared according to the method described in Example 39 by employing their corresponding 2-bromomethylphenyl derivatives as the starting materials:

(40) 1-methyl-5-(2-dimethylaminomethylphenyl)-3-phenyl-1,2,4-triazole. B.p. 180.degree. C./0.07 mm Hg. Yield 96%.

(41) 1-methyl-5-(2-dimethylaminomethylphenyl)-3-(m-tolyl)-1,2,4-triazole. B.p. 180.degree. C./0.01 mm Hg. Yield 95%.

1-Methyl-5-(o-tolyl)-3-phenyl-1,2,4-triazole

A mixture of 0.56 g. of benzimidic acid 2-methylhydrazide hydrochloride and 3.8 g. of o-toluic acid chloride is heated under stirring at about 120.degree. C. After cooling and addition of diethyl ether, the hydrochloride of the triazole is collected on filter and then suspended in a sodium bicarbonate aqueous solution. The free base is extracted with diethyl ether and the organic phase, after drying over sodium sulfate, is evaporated. The crude compound is purified by distillation at 160.degree. C./0.1 mm Hg. Yield 76%.

The following triazoles are prepared in accordance with the method described in Example 42 by using the corresponding acid chlorides and benzimidic acid hydrazides:

The benzimidic acid hydrazides employed as the starting materials for preceding Examples 42-53 are prepared according to the method described by N. R. Atkinson in J. Chem. Soc. 3319 (1954). The following were so prepared:

o-toluimidie acid 2-methylhydrazine hydrochloride M.p. 85.degree.-88.degree. C. with decomposition

m-trifluoromethylbenzimidic acid 2-methylhydrazide M.p. 57.degree.-61.degree. C.

m-chlorobenzimidic acid 2-methylhydrazide M.p. 110.degree.-112.degree. C.

m-toluimidic acid 2-methylhydrazide M.p. 79.degree.-81.degree. C.

A mixture of 1.14 g. of o-toluimidic acid ethyl ester, 1.14 g. of 1-methyl-1-benzoylhydrazine and 0.1 g. of o-toluimidic acid ester hydrochloride, as a catalyst, is heated at about 100.degree. C. for three hours under reduced pressure (about 200 mm Hg) and then at about 120.degree. C. for five hours. The raw material is taken up with diethyl ether and the organic solution is washed with aqueous sodium bicarbonate and then dried over Na.sub.2 SO.sub.4. After evaporation of the solvent, the product is distilled at 170.degree. C./0.1 mm Hg. Yield 32%.

A mixture of 6.85 g. of 1-methyl-1-(o-toluyl)-hydrazine, 13.8 g. of m-chlorobenzimidic acid ethyl ester and 1.8 g. of the hydrochloride of m-chlorobenzimidic acid ethyl ester is heated with stirring under vacuum for 18 hours and simultaneously ethanol and m-chlorobenzonitrile are distilled off. Then, maintaining the temperature at about 65.degree. C., 40 ml. of ethanol are added followed by a sodium ethylate solution prepared from 0.336 g. of sodium and 20 ml. of ethanol. The mixture is refluxed for 6 hours and after standing over night, the insoluble precipitate is filtered off. The filtrate is evaporated to dryness. The residue is dissolved in 100 ml. of diethyl ether and after washing the organic layer successively with aqueous 5% Na.sub.2 CO.sub.3, 5% HCl and water, the solution is dried over sodium sulfate. The crude product obtained by evaporation of the diethyl ether solution is crystallized from ethanol. Yield 66%. M.p. 77.degree.-78.degree. C.

By following the procedure of Example 55, the following triazoles are prepared:

(56) 1-methyl-3-(m-tolyl)-5(o-tolyl)-1,2,4-triazole. M.p. 80.degree.-81.degree. C., by reacting 1-methyl-1-(o-toluyl)hydrazine with m-toluimidic acid ethyl ester and its corresponding hydrochloride as a catalyst.

(57) 1-methyl-5-(3-chlorophenyl)-3-(o-tolyl)-1,2,4-triazole

M.p. 86.degree.-88.degree. C., by reacting 1-methyl-1-(3-chlorobenzoyl)-hydrazine with toluimidic acid ethyl ester and its corresponding hydrochloride as a catalyst.

To a solution of 5.08 g. of 3-chlorobenzimidic acid 2-methyl-hydrazide and 4.3 ml. of triethylamine in 85 ml. of dichloromethane, 5.6 g. of 2,6-dimethoxybenzoyl chloride in 50 ml. of dichloromethane are added under stirring. The agitation is continued for about 20 hours. The solution is then washed with diluted sodium bicarbonate and with water and dried over Na.sub.2 SO.sub.4. The solvent is evaporated and the product crystallized from 1,2-dimethoxyethane. M.p. 172.degree.-173.degree. C. Three grams of the so obtained 1-methyl-1-(2,6-dimethoxybenzoyl)-2-(3-chlorobenzimidoyl)-hydrazine is added to a solution of 0.06 g. of sodium in 37 ml. of n-pentanol and the mixture is heated at 150.degree. C. for 6 hours. The solvent is then distilled off and the crude product, after treatment with water, is collected on a filter. Crystallization from diisopropyl ether affords a product which melts at 147.degree.-148.degree. C. Overall yield 47%. This compound has been prepared also through a one-step process according to the method described in Example 54 by reacting 3-chlorobenzimidic acid ethyl ester with 1-methyl-1-(2,6-dimethoxybenzoyl)hydrazine. The starting imidates of Examples 55 to 57 and the corresponding salts are prepared according to literature methods. (Pinner, "Die Imidoaether und Ihre Derivate" - R. Oppenheim, Berlin, 1892; L. Weintraub et al., J. Org. Chem., Vol. 33, No. 4, page 1679, 1968). The starting 1-methyl-1-benzoylhydrazines are prepared according to the method described by A. R. MacCarthy et al. In J.C.S.(B) 1185 (1969) for 1-methyl-1-benzoylhydrazine. The following new compounds have been so prepared:

1-methyl-1-(o-toluyl)hydrazine hydrochloride. M.p. 190.degree.-191.degree. C.

1-methyl-1-(3-chlorobenzoyl)hydrazine. B.p. 130.degree.-140.degree. C./0.05 mm Hg.