DE1010969B - Process for the preparation of new 2-imidazolones - Google Patents

Description

Process for the preparation of new 2-imidazolones The present invention relates to a process for the preparation of new 2-imidazolones of the general formula in which R1 is hydrogen, a lower alkyl or alkoxy radical, a halogen or a nitro group, R2 is a phenyl, lower monoalkylphenyl, lower monoalkoxyphenyl, monohalophenyl, mononitrophenyl, lower alkyl or cycloalkyl radical, R3 is hydrogen, a lower alkyl radical or denote a lower alkanoyl radical.

The new 2-imidazolones are characterized in that they at least in the 1-position of the imidazolone nucleus and in some cases also in the 3-position are substituted. As examples of substituents in the 1-position of the imidazolone nucleus the benzhydryl, a-ethylbenzyl, a- (n-propyl) benzyl, p-methylbenzhydryl, p-methoxybenzhydryl, p, p'-dimethoxybenzhydryl, p-nitrobenzhydryl or the a-cyclohexylbenzyl radical. As examples of substituents that may be present in the 3-position are Residues such as the methyl, ethyl, n-butyl, acetyl or propionyl radical are mentioned. However, the 3-position can also be insubstituted.

The 1-benzhydryl-3- (lower-alkyl) -2-imidazolones represent a particularly interesting group of compounds The preferred compound of this group is 1-benzhydryl-3-methyl-2-imidazolone.

Another interesting group of compounds are the 1- (a- [lower] - alkylbenzyl) -3- [lower] - alkyl-2-imidazolones of which 1- (a-ethylbenzyl) -3-methyl-2-imidazolone is the preferred compound represents.

The new 2-imidazolones are available as therapeutics, especially as anticonvulsants, usable. 1-benzhydryl-3-methyl 2-imidazolone e.g. B. shows in pharmacological Investigation in comparative experiments one compared to known ones, more epileptic in therapy Diseases of used preparations have a significantly better effect.

According to the invention, the new 2-imidazolones of the formula I are prepared in such a way that a compound of the general formula in which R1 and R2 have the above meaning, R4 is a lower alkyl radical and R3 'is hydrogen or a lower alkyl radical, is heated in an acidic medium, whereupon the compound obtained, if R3' is hydrogen, is heated with an acid anhydride of a lower alkanecarboxylic acid can.

The starting materials of the formula II can be used in accordance with the following equation get in a simple manner by reacting an ester of isocyanic acid of the formula III with an aminoacetaldehyde-di- (lower-alkyl) -ac6tal of the formula IV and thus a 1- (a-substituted benzyl) -3- (formylmethyl) -urea-di- (lower-alkyl) acetal of the formula II, e.g. B. generated by heating the combined reaction components.

A process for the preparation of compounds of the formula II in which R1 denotes hydrogen, R2 denotes the phenyl radical, R3 'and R4 denote a lower alkyl radical, ie of compounds of the formula II a, is 4,4-diphenyl-2,5-oxazolidinedione (Formula V) to react with a (lower) alkylaminoacetaldehyde-di- (lower-alkyl) -acetal (formula IV a). This general procedure can be illustrated by the following equation No protection is sought for the production of the starting materials of the claimed process in the context of the present patent.

Example 1 1-Benzhydryl-3-methyl-2-imidazolone A solution of 195.7g 1-Benzhydryl-3-methyl-3- (formylmethyl) urea dimethylacetal in 400 cm3 alcohol and 227 cm 3 of 1.98 N hydrochloric acid was refluxed for 25 minutes. To Cooling down and adding 200 cm3 of water became the crystallized product, viz 1-Benzhydryl-3-methyl-2-imidazolone, filtered off and washed with aqueous alcohol. The product showed after recrystallization by dissolving in absolute alcohol and Addition of petroleum ether has a melting point of 166 °. The yield was 92%.

The 1-benzhydryl-3-methyl- 3- (formylmethyl) used as the starting compound urea dimethylacetal can be obtained by the following two methods.

Method A. A solution of 86g methylaminoacetaldehyde dimethylacetal (Kermack et al., J. Chem. Soc., 121, p. 1884, [1922]) in 500 cm3 of benzene slowly added to a solution of 151 g of benzhydryl isocyanate in 500 cm 'of benzene. The resulting solution was refluxed for 15 minutes. To the product To bring to crystallize, 1.51 petroleum ether (boiling range: 30 to 60 °) added. The product was filtered off and washed with petroleum ether. To Recrystallization from toluene and petroleum ether showed the product, namely 1-benzhydryl-3 -methyl-3- (formylmethyl) -urea - dimethylacetal, a melting point of 111 to 111.5 °. Method B. A solution of 11.35 g of methylaminoacetaldehyde dimethylacetal and 24.10 g of 4,4-diphenyl-2,5-oxazolidinedione (U.S. Patent 2,578,293) in 20 cm3 of dry dioxane was refluxed for 3 hours at the boiling point - heated. After cooling, the product began to crystallize. The crystallization was completed by adding 70 cm3 of petroleum ether (boiling range: 30 to 60 °). The product, 1-benzhydryl-3-methyl-3- (formylmethyl) urea dimethylacetal, became filtered off and washed with petroleum ether.

Example 2 1- (a-Ethylbenzyl) -3-methyl-2-imidazolone 15.2 g of 1- (a = ethylbenzyl) -3-methyl-3- (formylmethyl) urea dimethylacetal were mixed with 28 cm3 of ethanol and 70 cm3 1 N hydrochloric acid mixed. After refluxing for 5 minutes, the solution was cooled, causing the product, 1- (α-ethylbenzyl) -3-methyl-2-imidazolone, to crystallize out. The product was filtered off and washed with aqueous ethanol. M.p. 107 °. The yield was 87 % .

The 1- (a-ethylbenzyl) -3 -methyl-3- used as the starting compound (Formylmethyl) urea dimethylacetalk can be prepared as follows.

A solution of 49.2 g of 2-phenylbutyric acid in 30 cm3 of thionyl chloride was heated on the water bath for 2 hours. The excess thionyl chloride was removed by distillation and the residue was fractionally distilled in vacuo became. The product, 2-phenylbutyryl chloride, had a bp of 109 ° at 13 mm.

A solution of 49.8 g of 2-phenylbutyryl chloride in 100 cm3 of benzene was used on a steam bath for 11/2 hours together with 21.3 g of according to R. Adams, Organic Reactions, Vol. 3, p. 382 (1946), heated sodium azide under reflux. That Mixture of sodium salts was filtered off and the filtrate was fractionated in vacuo was distilled. Part of the fraction boiling at 105 to 106 ° / 17 mm, the a-ethylbenzyl isocyanate, was used for the following stage.

A solution of 11.3 g of a-ethylbenzyl isocyanate with a boiling point of 105 to 106 ° / 17 mm and 8.33 g of methylaminoacetaldehyde dimethylacetal in 35 cm3 of benzene was during Heated under reflux for 30 minutes. Concentration in vacuo gave a syrup of 1- (a-Ethylbenzyl) -3-methyl-3- (formylmethyl) urea dimethylacetal obtained, the was used directly for the reaction described in the example.

Example 3 1- (α-methylbenzyl) -2-imidazolone 20.2 g of 1- (α-methylbenzyl) -3- (formylmethyl) -urea-dimethyl-acetal were treated with a mixture of 100 cm3 alcohol and 100 cm3 1N hydrochloric acid for 25 Heated under reflux for minutes. When 250 cm3 of water were added and cooled, it crystallized 1- (a-methylbenzyl) -2-imidazolone.

The product melted at 125 to 126.5 ° and after recrystallization from xylene at 128 to 129 '. The yield was 88%.

The 1- (a-methylbenzyl) -3- (formylmethyl) urea dimethylacetal used as the starting material can be prepared as follows: A solution of 50 g of a-methylbenzylamine in 500 cm3 of toluene was saturated with hydrogen chloride. After adding 250 cm3 of toluene phosgene was passed through the suspension of the chlorohydrate while at the same time was refluxed for 4 hours. The resulting clear solution was distilled in vacuo. It became a mainly α-methylbenzyl isocyanate containing fraction boiling at 92 to 95 ° / 17 mm.

A mixture of 14.7 g of a-methylbenzyl isocyanate and 10.5 g of aminoacetaldehyde dimethylacetal in 200 cm3 benzene was refluxed for 20 minutes. By distance the solvent in vacuo became 1- (a-methylbenzyl) -3- (formylmethyl) urea dimethylacetal obtained in the form of an oil.

Example 4 1- (a-Ethylbenzyl) -3-ethyl-2-imidazolone 13.7g 1- (a-ethylbenzyl) -3-ethyl-3- (formyhmethyl) urea dimethyl acetal 60 cm3 of alcohol and 59 cm3 of 1N hydrochloric acid were added. The mixture was during Heated under reflux for 40 minutes. The resulting solution was distilled in vacuo and provided a crystallizing fraction with a boiling range of 148 to 152 ° at 0.6 mm. After pressing on a porous plate, the product was made 130 cm3 petroleum ether (boiling range: 70 to 90 °) recrystallized. The thus obtained 1- (a-Ethylbenzyl) -3-ethyl-2-imidazolone had a melting point of 63 ° to 65 °. the Yield was 9111/0.

The 1- (a-ethylbenzyl) -3-ethyl-3 - used as starting material - (Formylmethyl) urea dimethylacetal can be made as follows: A Mixture of 350 g of ethylamine, 600 cm3 of methanol and 112 g of chloroacetaldehyde dimethylacetal was heated in an autoclave at 140 to 146 ° for 24 hours. The solvent was removed on the steam bath at atmospheric pressure, whereupon the oily residue treated with four times its volume of ether, 200 cm3 of water and was saturated with anhydrous potassium carbonate. The ethereal layer has been separated whereupon the aqueous layer was extracted four times with 200 cm3 of ether. The United Ether extracts were dried over potassium carbonate and then distilled. The at The fraction boiling from 153 to 156 ° with a refractive index yaö = 1.4120 was N-ethylamino-acetaldehyde-dimethylacetal.

A mixture of 9.45 g of a-ethylbenzyl isocyanate, 7.85 g of N-ethylamino-acetaldehyde dimethylacetal and 30 cm3 of benzene was refluxed for 30 minutes. The solvent was removed in vacuo. The syrupy product, 1- (a-ethylbenzyl) -3-ethyl-3- (formylmethyl) urea dimethylacetal, was used directly for the reaction described.

Example 5 1-Benzhydryl-2-imidazolone 63.3 g of 1-benzhydryl-3- (formylmethyl) urea dimethylacetal were refluxed with 50 cm3 of ethanol and 232 cm3 of 1N hydrochloric acid. The received 1-Benzhydryl-2-imidazolone was recrystallized from 11 50% aqueous ethanol. M.p. 214 to 215 °. The yield was 90%.

The 1-benzhydryl-3- (formylmethyl) urea dimethylacetal used as the starting material can be prepared as follows: 53.3 g of benzhydryl isocyanate and 26.3 g of aminoacetaldehyde dimethylacetal are refluxed in benzene. Something that melts at 140 to 141 'is obtained 1-Benzhydryl-3- (formylmethyl) urea dimethylacetal. Example 6 1- (α-Cyclohexylbenzyl) -2-imidazolone A solution of 2.21 g of 1- (α-cyclohexylbenzyl) -3- (formylmethyl) urea dimethylacetal in 15 cm3 alcohol, 7 cm3 water and 6.9 cm3 1N hydrochloric acid was on the steam bath heated for 25 minutes. The product crystallized out on cooling. It was washed with aqueous alcohol. After recrystallization from a mixture of ethanol and water, the product had a melting point of 206 ° to 208 °. The yield was 86 ° / o.

The 1- (a-cyclohexylbenzyl) -3 - (formylmethyl) used as starting material -urea dimethylacetal can be prepared as follows A mixture of 1.08 g of a-cyclohexylbenzyl isocyanate, 0.525 g of aminoacetaldehyde dimethylacetal and 5 cm3 Benzene was heated on the steam bath for 10 minutes. The product was through Cooling and adding 15 cm3 of petroleum ether crystallized out and then filtered off. The 1- (α-cyclohexylbenzyl) -3- (formylmethyl) urea dimethylacetal was obtained by recrystallization from a mixture of benzene and petroleum ether obtained from m.p. 136 to 137 °.

Example 7 1- (α-Cyclohexylbenzyl) -3-methyl-2-imidazolone A mixture of 2.35 g of 1- (a-cyclohexylbenzyl) -3-methyl-3- (formylmethyl) urea dimethylacetal with 14 cm3 of 0.5N hydrochloric acid and 14 cm3 of ethanol were refluxed for 15 minutes heated. 1- (α-Cyclohexylbenzyl) -3-methyl-2-imidazolone crystallized on cooling from, which had a m.p. of 198 to 199 °. The yield was 88%.

The 1- (a-cyclohexylbenzyl) -3-methyl-3- used as starting material (Formylmethyl) urea dimethylacetal can be prepared as follows 2,54 g of α-cyclohexylbenzyl isocyanate and 1.41 g of N-methylaminoacetaldehyde dimethylacetal in 10 cm3 of benzene are mixed in the manner described in Example 6 for Brought reaction. 1- (a-Cyclohexylbenzyl) -3-methyl-3- (formylmethyl) urea dimethylacetal is obtained, after recrystallization from a mixture of benzene and petroleum ether at 98 to 99 ° melts.

Example 8 1- (α-Cyclohexylbenzyl) -3-ethyl-2-imidazolone By hydrolyzing of 2.31 g of 1- (a-cyclohexylbenzyl) -3-ethyl-3- (formylmethyl) urea dimethylacetal with 6.65 cm31 of N hydrochloric acid and 8 cm3 of alcohol for 35 minutes, 1- (α-cyclohexylbenzyl) -3-ethyl-2-imidazolone was obtained obtained after recrystallization from a mixture of benzene and petroleum ether melted at 146 to 147 °. The yield was 88%.

The 1- (a-cyclohexylbenzyl) -3-ethyl-3- used as the starting compound (Formylmethyl) urea dimethylacetal can be prepared as follows: Avg Reaction of 2.15 g of α-cyclohexylbenzyl isocyanate with 1.33 g of N-ethylaminoacetaldehyde dimethylacetal in the manner described in Example 6, 1- (a-cyclohexylbenzyl) -3-ethyl-3- (formylmethyl) urea-dimethylacetal which melted at 75 ° obtain.

Example 9 1- (p-chlorobenzhydryl) -2-imidazolone A mixture of 7.53 g 1- (p-chlorobenzhydryl) -3- (formylmethyl) urea diethyl acetal, 20 cm -1 N hydrochloric acid and 20 cm 3 ethanol was used during Heated under reflux for 25 minutes. On cooling, 1- (p-chlorobenzhydryl) -2-imidazolone crystallized out, melted at 222 to 224 ° and, after recrystallization from ethanol, had a melting point of 226 to 227 °. The yield was 83 % . The 1- (p-chlorobenzhydryl) = 3 - (formylmethyl) - urea - diethylacetal used as the starting compound can be prepared as follows: A mixture of 9.74 g of p-chlorobenzhydryl isocyanate, 5.32 g of aminoacetaldehyde diethyl acetal and 400 cm3 of benzene was refluxed for 40 minutes. When 150 cm3 of petroleum ether was added, the 1- (p-chlorobenzhydryl) -3- (formylethyl) urea diethyl acetal, which melted at 128 to 129 °, crystallized out.

Example 10 1- (p-Chlorobenzhydryl) -3-methyl-2-imidazolone 14.3 g 1- (p-Chlorobenzhydryl) -3- (formyhmethyl) -3-methylurea-dimethyl acetal were dissolved in 50 cm3 of ethanol and 50 cm3 of 1N hydrochloric acid, whereupon the solution during Was refluxed for 30 minutes. On cooling, 1- (p-chlorobenzhydryl) -3-methyl-2-imidazolone crystallized from, which after recrystallization from ethyl acetate and petroleum ether (boiling range: 70 to 90 °) melted at 116.5 to 117.5 °. The yield was 89%.

The 1- (p-chlorobenzhydryl) - 3 - (formylmethyl) used as starting material - 3 - methyl - urea - dimethylacetal can be prepared as follows A Mixture of 12.2 g of p-chlorobenzhydryl isocyanate, 5.95 g of N-methyl-aminoacetaldehyde-dimethylacetal and 50 cm3 of benzene was refluxed for 30 minutes. By evaporation of the benzene in vacuo became 1- (p-chlorobenzhydryl) -3- (formylethyl) -3-methylurea-dimethylacetal received in the form of a syrup. That from a mixture of benzene and petroleum ether The product which crystallized out had a melting point of 97 ° to 98 °.

Example 11 1- (p-Chlorobenzhydryl) -3-ethyl-2-imidazolone A mixture of 1.13 g of 1- (p-chlorobenzhydryl) obtained in accordance with paragraph 2 in this example - 3 - ethyl-3- (formyhnethyl) -urea-dimethylacetal, 4 cm3 ethanol and 3 cm3 1 Normal hydrochloric acid was refluxed for half an hour. 1- (p-Chlorobenzhydryl-3-ethyl-2-imidazolone crystallized out on addition of water and melted at 94 to 95 °. The yield was 87%.

The 1- (p-chlorobenzhydryl) - 3 - ethyl- 3 - (formylmethyl) urea dimethylacetal can be prepared as follows A mixture of 2.44 g of p-chlorobenzhydryl isocyanate, 1.33 g of N-ethyl-aminoacetaldehyde-dimethylacetal and 10 cm3 of benzene was refluxed for 30 minutes. The product, 1- (p-Chlorobenzhydryl) -3-ethyl-3- (formylmethyl) urea dimethylacetal was by Addition of petroleum ether (boiling range: 70 to 90 °) brought to crystallize and recrystallized from a mixture of benzene and petroleum ether. M.p. 84 to 85 °.

Example 12 1- (p-bromobenzhydryl) -3-methyl-2-imidazolone A mixture of 4.07g 1- (p-bromobenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal, 25 cm3 of ethanol and 10 cm3 of 1N hydrochloric acid were refluxed for 30 minutes heated. On addition of 25 cm3 of water and cooling, the 1- (p-bromobenzhydryl) -3-methyl-2-imidazolone crystallized the end. The product was filtered off and washed with 50 ° / olgem aqueous ethanol. It was recrystallized from a mixture of ethanol and water and then exhibited has a melting point of 135.5 to 136.5 °. The yield was 82 ° / a. That as the starting material used 1- (p-bromobenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal can be prepared as follows: A mixture of 11.5 g of p-bromobenzhydryl isocyanate, , 4.76 g of N-methyl-aminoacetaldehyde-dimethylacetal and 20 cm3 of benzene was during Heated under reflux for 30 minutes. On cooling, 1- (p-bromobenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal crystallized from which was washed with petroleum ether. The product was made from benzene and petroleum ether recrystallized. It then had a melting point of 122 to 123 °. Example 13 1- (p-Bromobenzhydryl) -3-ethyl-2-imidazolone A mixture of 4.21 g of 1- (p-bromobenzhydryl) -3-ethyl-3- (formylmethyl) urea dimethylacetal, 25 cm3 of ethanol and 10 cm3 of N hydrochloric acid were refluxed for 30 minutes. Upon addition of 10 cm3 of water and cooling, the 1- (p-bromobenzhydryl) -3-ethyl-2-imidazolone crystallized the end. After recrystallization from 50% aqueous methanol, the product had a M.p. from 118.5 to 119.5 °. The yield was 840%.

The 1- (p-bromobenzhydryl) -3-ethyl-3- (formylmethyl) urea dimethylacetal used as the starting compound can be prepared as follows: A mixture of 11.5 g of p-bromobenzhydryl isocyanate, 5.32 g of N-ethyl-aminoacetaldehyde-dimethylacetal and 20 cm3 of benzene were added during 30 Heated under reflux for minutes. When cooling and adding 100 cm3 of petroleum ether (Boiling range: 30 to 60 °) crystallized 1- (p-bromobenzhydryl) -3-ethyl-3- (formylethyl) urea dimethyl acetal from, whose melting point was 86 to 87.5 °.

Example 14 1- (p-Methylbenzhydryl) -3-methyl-2-imidazolone A mixture of 1.03 g of 1- (p-methylbenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal, 4 cm3 of ethanol and 3 cm3 of N hydrochloric acid were refluxed for 30 minutes. The 1- (p-methylbenzhydryl) -3-methyl-2-imidazolone was obtained by concentrating the solution in vacuo obtained in the form of a glassy mass. The yield was 87%.

The 1- (p-methylbenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetalk used as the starting material can be prepared as follows: A mixture of 7.31 g of p-methylbenzhydryl isocyanate, 3.9 g of N-methyl-aminoacetaldehyde-dimethylacetal and 30 cubic meters of benzene were added during 45 Heated under reflux for minutes. When cooling and adding 60 cm3 of petroleum ether (Boiling range: 30 to 60 °) the product crystallized, 1- (p-methylbenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal, the end. The filtered crystals melted at 78 to 79 °.

Example 15 1- (p-Nitrobenzhydryl) -3-methyl-2-imidazolone 2.15g 1- (p-Nitrobenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal were dissolved in 8 cm3 of ethanol and 5.75 cm3 of 1N hydrochloric acid. The solution was during Heated under reflux for 45 minutes. 1- (p-Nitrobenzhydryl) -3-methyl-2-imidazolone was obtained by evaporating the solvents. The yield was 840%.

The 1- (p-nitrobenzhydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal used as the starting material can be prepared as follows: a mixture of 2.43 g of p-nitrobenzhydryl isocyanate, 1.14 g of N-methyl-aminoacetaldehyde dimethylacetal and 10 cm3 benzene was refluxed for 30 minutes. After evaporation of the solvent the product was crystallized from a mixture of benzene and petroleum ether and recrystallized. The product obtained had a melting point of 60 ° to 62 °.

Example 16 1- (p-Methoxybenzhydryl) -3-methyl-2-imidazolone A mixture of 9; 12g 1- (p-methoxybenzhydryl) -3 - methyl - 3 - (formylmethyl) .- urea - dimethylacetal, 25 cm3 of ethanol and 25.5 cm3 of 1N hydrochloric acid were added for 35 minutes heated to reflux. When the solution was evaporated, the imidazolone was in shape obtained a varnish-like mass. The yield was 89%.

The 1- (p-methoxybenzhydryl) -3 -methyl-3- used as starting material (Formylmethyl) urea dimethylacetal can be prepared as follows: A mixture of 11.1 g of p-methoxybenzhydryl isocyanate, 5.35 g of N-methyl-aminoacetaldehyde dimethylacetal and 50 cc of benzene was refluxed for 35 minutes. When adding 200 cm 'petroleum ether (boiling range: 30 to 60 °) crystallized asl- (p-methoxyben7, hydryl) -3-methyl-3- (formylmethyl) urea dimethylacetal the end. M.p. 76 to 77 °.

Example 17 1- (p-Methoxybenzhydryl) -3-ethyl-2-imidazolone A mixture of 14.88 g of 1- (p-methoxybenzhydryl) -3-ethyl-3- (formylmethyl) urea dimethylacetal, 28 cm3 of ethanol and 40 cm3 Normal hydrochloric acid was refluxed for 1 hour. On cooling, the 1- (p-methoxybenzhydryl) -3-ethyl-2-imidazolone crystallized out. It was filtered off and washed with water. After recrystallization from a mixture of benzene and petroleum ether, the product melted at 117 to 118 °. The yield was 89 % .

The 1- (p-methoxybenzhydryl) -3-ethyl-3- (formylmethyl) urea dimethylacetal used as the starting material can be prepared as follows: A mixture of 15 g of p-methoxybenzhydryl isocyanate, 8.35 g of N-ethyl-aminoacetaldehyde-dimethylacetal and 50 cm3 of benzene were added during 35 Heated under reflux for minutes. 1- (p-Methoxybenzhydryl) -3-ether-3- (formylmethyl) urea dimethylacetal crystallized on addition of petroleum ether. After recirculation from one A mixture of benzene and petroleum ether (boiling range: 30 to 60 °) gave the product a M.p. from 74 to 75 °.

Example 18 1-Benzhydryl-3-ethyl-2-imidazolone 12.5 g of 1-benzhydryl-3-ethyl-3- (formylmethyl) urea dimethyl acetal 50 cm3 of alcohol and 50 cm3 of N hydrochloric acid were added. The mixture was during heated on the steam bath for half an hour. After removing the solvents the oily residue was in a Soxhlet apparatus with petroleum ether (boiling range: 30 to 60 °) extracted. When the petroleum ether evaporated, a semi-crystalline one remained 1-Benzhydryl-3-ethyl-2-imidazolone residue, which is obtained from petroleum ether (boiling range: 70 to 90 °) was recrystallized. After a second recrystallization from petroleum ether with a boiling range of 70 to 90 °, the melting point of the product was 84 up to 85 °. The yield was 90%.

The 1-benzhydryl-3-ethyl-3- (formylmethyl) urea dimethylacetal used as the starting material was prepared as follows: A mixture of 10.81 g benzhydryl isocyanate, 6.9 g N-ethyl-aminoacetaldehyde-dimethylacetal and 30 cm3 benzene was added for 15 minutes heated to reflux. The product obtained was 1-benzhydryl-3-ethyl-3- (formylmethyl) urea dimethylacetal.

Example 19 1- (p, p'-Dimethoxybenzhydryl) -2-inidazolone A mixture of 2.81 g of 1- (p, p'-dimethoxybenzhydryl) - 3 - (formylmethyl) - urea - diethylacetal with 10: cm3 ethanol and 7 cm- '1 N hydrochloric acid was refluxed for 30 minutes heated. When adding 25 cm3 of water, the 1- (p, p'-dimethoxybenzhydryl) -2-imidazolone fell the end. After recrystallization from ethyl acetate, the product had a melting point. from 199 ° to. The yield was 88%.

The 1- (p, p'-dimethoxybenzhydryl) -3- (formylmethyl) urea diethyl acetal used as the starting material can be prepared as follows: a mixture of 2.69 g of p, p'-dimethoxybenzhydryl isocyanate, 1.33 g of aminoacetaldehyde diethyl acetal and 15 cm3 of benzene were added for 20 minutes heated to reflux. When cooling down and adding 15 cm3 of petroleum ether (boiling range: 30 to 60 °) the 1- (p, p'-dimethoxybenzhydryl) -3- (formylmethyl) urea diethylacetal crystallized the end. M.p. 138 to 139 °.

Example 20 1-Benzhydryl-3-acetyl-2-imidazolone A mixture of 12.7 g of 1-benzhydryl-2-imidazolone and 180 cm 3 of acetic anhydride was refluxed for 30 minutes. After the excess acetic anhydride had evaporated, the reaction product was dissolved in 75 cm3 of ethanol. The 1-benzhydryl-3-acetyl-2-imidazolone crystallized out on cooling the solution in a bath of dry ice and acetone. The product was washed with cold ethanol and petroleum ether. After recrystallization from 70 cm3 of ethanol, the product had a melting point of 130 to 131 ' . The yield was 86 "/ o.

Example 21 1-Benzhydryl-3-propionyl-2-imidazolone The propionyl compound was analogous to the acetyl compound according to Example 20 from 10 g of 1-benzhydryl-2-imidazolone and 100 cm3 of propionic anhydride. The 1-benzhydryl-3-propionyl-2-imidazolone was crystallized from ethanol. The product had an mp 98 to 99 ° and was obtained in a yield of 840 / ".

Claims (1)

PATENT CLAIM: Process for the preparation of new 2-imidazolones of the general formula in which R1 is hydrogen, a lower alkyl or alkoxy radical, a halogen or a nitro group, R2 is a phenyl, lower monoalkylphenyl, lower monoalkoxyphenyl, monohalophenyl, mononitrophenyl, lower alkyl or cycloalkyl radical, R3 is hydrogen, a lower alkyl radical or denote a lower alkanoyl radical, characterized in that a compound of the general formula in which R1 and R2 have the above meaning, R4 is a lower alkyl radical and R3 'is hydrogen or a lower alkyl radical, is heated in an acidic medium, whereupon the compound obtained, if R3' is hydrogen, is heated with an acid anhydride of a lower alkanecarboxylic acid can, Publications considered: Ber. German chem. Ges., 25, p. 2354 (1892); Journ. amer. chem. soc., 68, p. 2350 (1946); U.S. Patent No. 2,460,747; J. Pediatria, 34, p. 273 (1949).