DE861845C - Process for the preparation of ª ‡ -pyrrolidones - Google Patents

Description

Process for the preparation of α-pyrrolidones It has been found that α-pyrrolidones are obtained if γ-nitrocarboxylic acids or their esters or amides are used catalytically reduced and, if the ring closure has not occurred immediately, the The resulting y-amino acids, esters or amides are heated until the ring closes is.

The γ-nitrocarboxylic acids used and their esters or amides are z. B. by the method of patents 851342 and 855 256 available. The transformation into the a-pyrrolidones is carried out using the for the reduction of nitro to Amino groups usual catalysts and working conditions. The IVIit usage of solvents is often beneficial.

It is known that γ-aminocarboxylic acids when heated to higher temperatures converted into α-pyrrolidones with elimination of water. It is opposite Surprisingly, that in the catalytic reduction of γ-nitrocarboxylic acids, but also of their esters and amides at relatively low temperatures, e.g. B. 3o to 50 °, generally readily formed α-pyrrolidones; if instead of y-aminocarbonic acids or their esters or amides are formed, they can be converted into α-pyrrolidones by heating.

The a-pyrrolidones are valuable intermediates, especially for pharmaceutical purposes. The parts used in the following examples are parts by weight.

EXAMPLE 100 parts of ethyl i-nitrocyclohexyl-i-propionate are dissolved in 100 parts of methanol and, after the addition of 5 parts of Raney nickel, at 30 ° to 50 ° and 100 atm. Reduced hydrogen pressure in the autoclave. When the uptake of hydrogen has ceased, the reaction solution is freed from the catalyst by filtration. The crystalline residue remaining after evaporation of the methanol can be used for further purification, e.g. B. from methylcyclohexane are recrystallized. It consists of the 5-spiro-cyclohexyl-2-pyrrolidone of the formula from melting point 132 to 133 °. The yield is practically quantitative. The same product is obtained if the amide of i-nitrocyclohexyl-i-propionic acid is used as the starting material instead of the ethyl ester.

Example 2 50 parts of γ-nitro-γ-methylpimelic acid dimethyl ester Dissolved in zoo parts of methanol and after adding 3 parts of Raney nickel at 3o to 40 ° below 100 atm. Reduced hydrogen pressure in the autoclave. One receives after - the Filter and distill off the methanol to leave a residue at 6 mm pressure boils at 186 to 185 °. The distillate solidifies quickly; after recrystallization from a little benzene, the yield obtained in this way in about 20% of the yield melts 5-Methyl-2-pyrrolidone-5-propionic acid methyl ester at 63 to 65 °.

Example 3 100 parts of i-nitrocyclohexyl-i-succinic acid dimethyl ester are reduced as in Example i after the addition of 150 parts of methanol and 5 parts of Raney nickel. After cooling, the contents of the autoclave have solidified in a crystalline manner. The mixture is brought into solution with heating, the catalyst is filtered off and allowed to cool again. The 5-spiro-cyclohexyl-2-pyrrolidone-q.-carboxylic acid methyl ester crystallizes from melting point 187 to 18g ° in approximately the calculated amount.

Example q.

20 parts of i-nitrocyclohexyl-i-propionic acid are dissolved in 100 parts of methanol dissolved and in the autoclave after adding 2 parts of Raney nickel at 50 ° with 100 atm. Hydrogen pressure reduced. After the uptake of hydrogen has ceased, the hot The methanol solution is freed from the catalyst by filtration. The one after vaporizing of the methanol remaining residue gives the same product on distillation as in example i.

Example 5 75 parts of γ-nitrobutyric acid ethyl ester are used in 100 parts Dissolved methanol and 15 parts of a palladium hydroxide-calcium carbonate catalyst shaken in a stream of hydrogen. When the uptake of hydrogen is complete, the catalyst becomes filtered off and the reaction mixture is distilled. 39 parts of α-pyrrolidone are obtained in this way with a melting point of 27 ° and a boiling point of 128 ° at a pressure of 10 mm.

Claims (1)

PATENT CLAIM: Process for the production of a-pyrrolidones, thereby characterized in that γ-nitrocarboxylic acids, their esters or amides are reduced catalytically and, if ring closure has not occurred immediately, any resulting y-amino acids, esters or amides heated until the ring closure has occurred. Dressed Publications: Beilstein, Handbook of Organic Chemistry, q .. Aufl., Vol. XXI, Pp. 236 and 237.