DE1059910B - Process for the production of piperidines - Google Patents

Description

Process for the preparation of piperidines It has been found that one Piperidine is obtained when you switch to glutaraldehyde or a glutaraldehyde, the by one or more alkyl, cycloalkyl, aralkyl or aryl groups. substituted is ammonia or a nitrogenous base that contains a primary amino group, at low temperatures, in particular between 0 and 10 ° C, can act and the reaction mixture obtained in the presence of a hydrogenation catalyst with hydrogen Treated as starting materials are other than glutaraldehyde, its substitution products, the one or more identical or different alkyl, cycloalkyl, aralkyl or Carry aryl groups. You get them z. B. by condensation of acroleins with vinyl alkyl ethers and subsequent acidic hydrolysis.

Suitable nitrogenous bases are, for example, ammonia and especially primary amines, such as methylamine, ethylamine, dodecylamine, ethanolamine, Benzylamine, cyclohexylamine, aniline or aminohexanol, or asymmetrically substituted Hydrazines.

The reaction is expediently carried out in aqueous solution or in the presence of organic solvents, such as methanol, ethanol, acetone, dioxane, tetrahydrofuran. For example, the primary amine can be quickly introduced into the glutaraldehyde solution cooled to about 0 to 10 ° C. and allowed to act for some time. The amount of the amine can fluctuate within wide limits and is at least the amount equivalent to the dialdehyde that is required for the reaction in the sense of the equation given for β-methylglutaraldehyde and methylamine is theoretically necessary, so per mole of glutaraldehyde at least 2 moles of amine. It is advantageous to use about twice the calculated amount.

The conversion into the piperidines is expediently carried out without isolation the reaction products after the addition of a conventional hydrogenation catalyst, e.g. B. one Nickel or cobalt supported or skeleton catalyst, a copper-chromium catalyst or a noble metal catalyst, with hydrogen. It is advantageous to first hydrogenate at room temperature and 100 at, until there is no more pressure decrease, and increases the temperature then gradually up to 150 ° C under increased pressures of 10 to 150 at.

The parts given in the examples are parts by weight.

Example 1 To an aqueous solution of ß-methylglutaraldehyde cooled to about 10 ° C, that of 426 parts of a-ethoxy-y-methyl-a, ß-dihydro-y-pyran by heating for 2 hours was obtained at 80 ° C with 2160 parts of water and 1 to 2 parts of hydrochloric acid, leaves as quickly as possible, with stirring and cooling, 460 parts of a cold 25 per cent Pour in aqueous ammonia solution. the Solution is then in one _ Antoklav.-xhit 200 parts of Raney cobalt paste and hydrogen up to one Pressure of 100 at pressed on. The temperature is increased during the hydrogenation. increased, if there is no more hydrogen uptake at room temperature; - you can still walk ' At 100 to 150 ° C, then allowed to cool and let the vessel relax. The hydrogenated mixture is freed from the catalyst and the filtrate is distilled for as long as there is in the distillate after the addition of solid potassium hydroxide, an oily precipitate can still be seen. That Total distillate is then supersaturated with potassium hydroxide and hexahydro-y-picoline failed. After drying and fractional distillation, 150 is obtained Parts with a boiling point of 125 ° C.

Example 2 In a solution, cooled to about 5 ° C., of 260 parts of β-methylglutaraldehyde 366 parts of ethanolamine are left in 2160 parts of water with stirring as quickly as possible flow in. After stirring for 1 hour at room temperature, the reaction mixture becomes mixed with 200 parts of Raney cobalt paste and, as described in Example 1, hydrogenated. When there is no more uptake of hydrogen, the catalyst is filtered off with suction and distilled the hydrogenated mixture under reduced pressure at 12 to 16 mm. After another Fine distillation gives 135 parts of N- (ß-oxyethyl) -hexahydro-γ-picoline (bp. 1B = 101 ° C). Example 3 In a solution of ß-methyl-glutaraldehyde, which, as in the example l described by acid hydrolysis of 426 parts - a-ethoxy-y-methyl-a, ß-dihydro-y-pyran obtained in 2160 parts of water and after neutralizing with about 1000 parts Methanol has been diluted, 488 parts are left at about -10 ° C. with stirring Add the ethanolamine as quickly as possible. If after several hours of stirring room temperature is reached, the reaction mixture is mixed with 200 parts of Raney cobalt paste and, as described in Example 1, hydrogenated. After the hydrogen uptake has ended is, the catalyst is filtered off with suction and the hydrogenated mixture is distilled under reduced pressure Print at 12 to 16 mm. Another fine distillation gives 144 parts N- (ß-Oxyethyl) -hexahydro-y-picoline.

Claims (1)

PATENT CLAIM: Process for the production of piperidines, thereby characterized in that one on glutaraldehyde or a glutaraldehyde, which by one or more alkyl, cycloalkyl, aralkyl or aryl groups is substituted, Ammonia or a nitrogenous base that contains a primary amino group, at low temperatures, in particular between 0 and 10 ° C, can act and the reaction mixture obtained in the presence of a hydrogenation catalyst with hydrogen treated.