DE928529C - Process for the preparation of ª-amino-ª-ketocaproic acid and derivatives thereof - Google Patents

Description

Process for the preparation of 8-amino-γ-ketocaproic acid and their Derivatives In the patent go6,697 is a process for the preparation of s-amino-y-ketocaproic acid described, wherein after kata'l'ytischer hydrogenation of the nitro group of a-nitro-y ketocap, ronic acid is the hydrogenation product at normal or slightly elevated temperatures either by adding oxalic acid as the primary oxalate or directly by adding it is separated from organic precipitants.

It has now been found that the hydrogenation is proceeding significantly more rapidly is possible when working in the autoclave under increased hydrogen pressure. At a hydrogen pressure From 5o to 100 at one can the uptake of 3 mol of hydrogen, which for the reduction of the nitro group are needed per mole of s-nitro-y-ketocaproic acid, even in a few Minutes to reach.

Above all, the various non-precious metal catalysts are suitable as catalysts, which are deposited on porous carriers, whereby, also the carrier substance itself can be involved in the catalytic effect. Is z. B. one on activated Alumina precipitated palladium catalyst.

It is particularly advantageous to carry out the hydrogenation in aqueous solution, since it runs smoother under these circumstances and becomes more uniform Reaction product leads. Here is predominantly the primary amine formed and the formation of a secondary product largely suppressed.

It has. has now shown that the primary reaction product is very sensitive to alkalis and elevated temperatures, e.g. For example, deamination easily occurs under these conditions, which is why the hydrogenation should preferably be carried out at room temperature or not above 40 to 50 ° and with a hydrogen ion concentration if possible - not above pH 5.

It. is therefore expedient., the hydrogenation mixture before the hydrogenation weakly acidic or the hydrogenation solution before work-up, z. B. by Evaporate, add some acid. There can be numerous inorganic and organic Acids are used.

So z. B. by adding formic acid during evaporation of the hydrogenation solution decomposition of the hydrogenation product is significantly reduced.

It has been shown that hydrochloric acid has a special protective effect on the easily cleavable amino group, since the reaction product is easy forms stable hydrochloride .-- In this way it is possible, after adding enough Hydrochloric acid to the hydrogenation solution to carry out evaporation even at (higher temperatures, without the hydrogenation product decomposing. The primary hydrochloride In the end, the amine separates out as a white crystalline mass in the form of needles with good properties Yield from and can be unicrystallized from isopropyl alcohol.

In order to avoid decomposition during the hydrogenation, the hydrochloric acid can also be added before the hydrogenation.

According to all indications, the hydrogenation product is present in this procedure in an oxylactone form, since neither a free keto group nor a carboxyl group can be detected. On the other hand, according to von S fyke, the amino group can be completely determined. After chromatography on paper, the hydrogenation product shows a yellow spot after heating with ninhydrin solution. Example i 35 g of s-nitro-y-ketocaproic acid are dissolved in 500 ccm of water and, after adding 8 g of finely powdered Pd-Al 2 03 catalyst (with 50/0 palladium), in an r-1 autoclave at a hydrogen pressure of 70 atm shaken at room temperature. When the pressure has dropped by about 30 at to 40 at, the hydrogenation of the N 02 group is complete, which takes place within about 1/2 hour.

After filtering off the catalyst, the pale yellow color Solution mixed with 25 cem concentrated hydrochloric acid and evaporated in vacuo at about 70 °.

The primary amine hydrochloride. separates as a white crystal mass which can best be recistallized from isopropyl alcohol.

Fine needles from 112 to 115 °. Examples 7 g e-nitro-y-ketocaproic acid are dissolved in 100 ccm of 20/0 salt fringes and in the presence of Pd-A12 03 catalyst (with 5 "/ o palladium) poured in a 2oo ccm autoclave at 100 atm. hydrogen pressure, according to

After uptake of 3 11M1 of hydrogen, which was reflected in the drop in pressure at about 70 at, the hydrogenation is stopped and the catalyst filtered off and the solution evaporated in vacuo on a water bath.

The white residue, which from the hydrodhloride of the primary amine consists, is recrystallized from isopropanol. F. 112 to 115o.

Claims (4)

PATENT CLAIMS: i. Process for the preparation of α-aminoy-ketocaproic acid according to patent 9o6 697, characterized in that a-nitro-y-ketocaproic acid in the presence is hydrogenated by noble metal catalysts at room temperature under pressure. 2. Process according to Claim i, characterized in that the solvent is water is used. 3. The method according to claim i and 2, characterized in that that inorganic or organic acids are added to the hydrogenation solution. 4th Process according to claim i to 3, characterized in that the hydrogenation solution is before or added hydrochloric acid after the hydrogenation and the hydrogenation product through Evaporation is deposited as the hydrochloride.