Title of Invention

A PROCESS FOR PREPARING A METHYL 1-5(3METHYLPIPERDINE PEDTAMINIE

Abstract

ABSTRACT 462/MAS/96 "A process for preparing a methvl-5-(3-methvlpiperidino)pentanamine" The present invention relates to a process for preparing a methyl-5-(3-methylpiperidino)pentanamine of the formula wherein one of the two radicals R1 and R2 is hydrogen and the other is methyl, or a mixture of two of such methyl-5-(3-methylpiperidino)pentanamines, characterized in that, in a first stage, 2-methylglutaronitrile, with or without addition of 3-methylpiperidine, is reacted with hydrogen in the presence of a first catalyst to give a mixture of the isomeric methyl-5-(3-methylpiperidino)pentanonitriles of formula wherein R' and R^ are as defined above, which is, in a second stage, hydrogenated in the presence of a second catalyst to give a mixture of the isomeric methyl-5-(3-methylpiperidino)pentanamines (la/Ib) and, if desired, this is separated into the two structural isomers. The compounds are suitable as catalysts in the production of polyurethanes.

Full Text

This invention relates to a process for preparing a methyl-5-(3-methylpiperi(iino)pentanamine. The present invention relates to new piperidino-pentanamines, both individually and as a mixture, namely 2-methyl-5-(3-inethylpiperidino)pentanamine and the iso¬meric 4-methyl-5-(3-methylpiperidino)pentanamine, which can be represented by the common formula In this formula, in both cases, one of the two radicals R1 and R1 is hydrogen and the other is methyl. In the case of 2-methyl-5-(3-methylpiperidino)pentanamine (la), R1 = methyl and R1 = H, in the case of 4-methyl-5-(3-methylpiperidino)pentanamine (lb), R1 = H and R1 = methyl. Each of the two compounds can exist in four , different stareoisomeric forms (two diastereomeric pairs) . Here and in the following, the formulae and the "associated names of compounds represent all possible stereoisomers in each case. The invention further relates to a process for preparing the abovementioned compovmds from 2-methyl-glutaronitrile and the use of the compounds as catalysts for producing polyurethanes from polyisocyanates and polyols. Polyurethanes are customarily produced using nitrogen bases, in particular tertiary amines such as l,4-diazabicyclo[2.2.2] octane (DABCO®), cyclic amidines such as 1, 8-diazabicyclo [5 .4 . O] undec-7-ene ("DBU") or guanidine derivatives such as tetrsmethylguanidine as catalysts. Decisive for the suitability as catalyst are, inter alia, the basicity, solubility behaviour and volatility. While the basicity primarily determines the catalytic effectiveness, solubility behaviour and volati¬lity are likewise important, for the processing proper- ties. For example, volatility which is too high can lead to irritation or danger to people as a result of libera¬tion into the atmosphere during the production of the polyurethanes or during their use. It is an object of the present invention to provide new amines which are suitable as catalysts for producing polyurethanes, have favourable use properties and can be prepared simply and inexpensively. According to the invention, the object is achieved by means of the piperidinopentanamines according to Claim 1 cind the preparation process according to Claim 4. It has been found that the 2-methylglutaronitrile formed as by-product in adiponitrile production can be reacted with hydrogen in the presence of a catalyst in one stage to give, apart from other products, a mixture of the two isomeric methyl-5-(3-methylpiperidino) pentano- where one of the two radicals R1,R1 is hydrogen and the other is methyl, which can be hydrogenated in a second stage in the presence of a second catalyst to give the mixture of the two isomeric methyl-5-(3-methylpiperi-dino)pentancunines la and lb. The isomer mixture la/Ib can, if desired, be separated by distillation or chromatography into the two structural isomers la and lb, but is preferably used as such. The catalyst used for the first stage is prefer¬ ably a supported palladivim catalyst, particular prefer¬ ence being given to palladivim on aluminium oxide. The reaction of the 2-methylglutaronitrile with hydrogen is preferably carried out at a temperature of from 100 to 250oC and a pressure of from 20 to 70 bar. It has been found to be advantageous to add some 3-methylpiperidine to the 2-methylglutaronitrile. The 3-methylpiperidine is preferably added in an amount of from 1 to 5 mol per 1 mol of 2-methylglutaronitrile. This significantly increases the selectivity of the reaction. 3-Methylpiperidine can be prepared by known methods, likewise from 2-methylglutaronitrile (WO 90/00 546). The reaction of the 2-methylglutaronitrile with hydrogen is preferably carried out continuously in a fixed-bed reactor. The hydrogenation of the methyl-5-(3-methyl-piperidino)pentanonitriles II to give the methyl-5-(3-methylpiperidino)pentanamines la/Ib is advantageously carried out in the presence of ammonia so as to suppress undesired secondary reactions. Catalysts which can be used for this second stage are essentially all catalysts which are suitable for the hydrogenation of nitriles to amines, i.e. for example palladium, platinxim, rhodium, cobalt, nickel or nickel boride. The catalyst used for the second stage' is prefer¬ably a supported rhodium catalyst, particular preference being given to rhodium on activated carbon. The hydrogenation of the methyl-5T(3-methyl-piperidino)pentanonitriles II over a supported rhodiuam catalyst is preferably carried out at a temperature of from 5 to l100oC and a pressure of from 1 to 50 bar. Solvents which can be used for the second stage are the solvents customary for the hydrogenation of nitriles to amines. Preference is given to using alcohols such as ethanol or tert-butyl alcohol. The methyl-5-(3-methylpiperidino)pentanamines la/Ib of the invention can, as already mentioned in the introduction, be used as catalysts for producing polyurethanes. Accordingly, the present invention provides a process for preparing a methyl-5-(3-methylpiperidino)pentanamine of the formula wherein one of the two radicals R1 and R1 is hydrogen and the other is methyl, or a mixture of two of such methyl-5-(3-methylpiperidino)pentanamines, characterized in that, in a first stage, 2-methylglutaronitrile, with or without addition of 3-methylpiperidine, is reacted with hydrogen in the presence of a first catalyst to give a mixture of the isomeric methyl-5-(3-methylpiperidino)pentanonitriles of formula wherein R1 and R1 are as defined above, which is, in a second stage, hydrogenated in the presence of a second catalyst to give a mixture of the isomeric methyl-5-(3-methylpiperidino)pentanamines (la/Ib) and, if desired, this is separated into the two structural isomers. The following examples illustrate the preparation and use of the compounds of the invention. Example: Example 1 A reactor (13 mm 0) was charged with 3 g of Pd/Al203 catalyst (1% Pd, particle size 0.315-1.0 mm). The reactor was heated to the reaction temperature of 150 °C in a stream of hydrogen (120 ml/min, based on atmospheric pressure) at 50 bar. A mixture of 3-methyl-piperidine and 2-methylglutaronitrile in a molar ratio of 2:1 was then metered into the hydrogen. The throughput was 2.1 g of starting material per g of catalyst and hour. The product mixture after leaving the reactor and separating off the hydrogen contained, according to GC, 44 . 8% of 2 (4) -methyl-5- (3-methylpiperidino) pentanitrile (isomer mixture), 30.2% of 3-methylpiperidine and 24.4% of 1,5-bis(3-methylpiperidino)-2-methylpentane and 0.6% of unidentified products. The mixture was collected over a reaction time of 2 60 hours and subsequently fractionated under reduced pressure. At 87°C/2.5 mbar, the methyl-5-(3rmethylpiperi-dino)pentanonitrile distilled over in a purity of 99.5% (GC) . According to NMR analysis, this was a mixture of 85% of 2-methyl compound and 15% of 4-methyl compound. methylpiperidine, 6% of 1,5-bis (3-methylpiperidino)-2-methylpentane, 1% of 2-methylglutaronitrile and 3% of unidentified products. The mixture was collected over a reaction time of 2 84 hours and subsequently fractionated under reduced pressure. At 87oC/2.5 mbar, the methyI-5-(3-methylpiperi¬dine)pentanonitrile distilled over in a purity of 99.3% (GC) . According to NMR analysis, this was a mixture of 86% of the 2-methyl compound and 14% of the 4-methyl com¬pound. Example 3 A reactor (13 mm 0) was charged with 3 g of a Pd/MgCl2/Al203 catalyst (1% Pd, 1.2% Mg, particle size 0.315-1.0 mm). The reactor was heated to the reaction temperature of 160oC in a stream of hydrogen (120 ml/min, based on atmospheric pressure) at 50 bar. 99.8% strength 2-methylglutaronitrile was then metered into the hydro¬gen. The throughput was 2.1 g of starting material per g of catalyst and hour. According to GC, the product stream contained 25.8% of 2(4)-methyl-5-(3-methylpiperidino)-pentanonitrile (isomer mixture),-' 52.1% of l,5-bis(3-methylpiperidinp)-2-methylpentane, 3.7% of 3-methylpiper¬idine and 18.4% of unidentified products. The selectivity of the reaction to give the desired nitriles was significantly lower tham in Examples 1 and 2 (with addition of 3-methylpiperidine) . Example 4 Ammonia was passed into 100 g of dry tert-butyl alcohol while cooling until a concentration of 13.7% of NH3 had been reached. A 100 ml autoclave having a magnet¬ically driven stirrer was flushed with nitrogen and pre-Gooled, 30 g of the solution of ammonia in tert-butyl alcohol, 4 g of rhodium/activated carbon (5% Rh) and 30 g of the mixture of methyl-5-(3-methylpiperidino)pentano-nitriles from Example 1 were then introduced. The autoclave was closed and heated while stirring. It was pressurized with hydrogen to 10 bar at room temperature, then the temperature was increased further to 5.0oC. According to GC, after 6 hours a conversion of 99.2% and • a yield of 87.3% had been achieved. The reaction mixture was distilled under reduced pressure, giving the isomer mixture 2(4)-methyl-5-(3-methylpiperidino)pentanamine at 104°C/3 mbar in a purity of 99.5%. According to GC, the mixture contained the 2-methyl compound and the 4-methyl compound in a ratio of The isomer mixture of 2-methyl-5-(3-methylpiperi-dino)pentanamine/4-methyl-5- (3-methylpiperidino)pentan-amine (2.6:1) from Example 4 was used as polyurethane catalyst: Abbreviations: VL: Desmodur® VL from Bayer, aromatic diisocyanate containing about 3 2% of NCO D550U: Desmophen® 550U, polypropylene glycol from Bayer, trifunctional containing 10.5% of OH DBU: diazabicyclo[5.4.0]undec-7-ene MMPPA: mixture of 2-methyl- and 4-methyl-5-(3-methyl-piperidino)pentanamine (2.6:1) DBU was used as comparative catalyst. Desmophen® was initially charged together with the amine (DBU or MMPPA) and mixed well. This gave a solution. In Examples 7 and 8, water was additionally added. This gave. an. emulsion/solution. A weighed amount of isocyanate (VL) • was added at a point in time t = 0 with vigorous stirr¬ing. The points in time • at which the solution was no longer turbid, • at which significant warming could be detected, • at which the mixture became solid were noted. The results (MMPPA in comparison with DBU) are shown in Table 1 below: Examples 9-12 The polymer from Examples 5 and 6 was changed into fine flakes and in each case 4 g of these were slurried in 45 g of ethanol and agitated daily. GC was used to determine the amount of catalyst which had been leached from the polymer after one day, after one week and after three weeks. The results (MMPPA in comparison with DBU) are shown in Table 2 below. It was found that, in contrast to DBU, the new catalyst was not eluted. The experiment was then repeated using a larger amount of catalyst (Examples 11 and 12) . After one day, MMPPA could now be detected in the solution, but the amount was significantly less than in the corresponding comparative-experiment using DBU and showed virtually no increase WE CLAIM: 1. A process for preparing a methyl-5-(3-methylpiperidino)pentanamine of the formula wherein one of the two radicals R1 and R2 is hydrogen and the other is methyl, or a mixture of two of such methyl-5-(3-methylpiperidino)pentanamines, characterized in that, in a first stage, 2-methylglutaronitrile, with or without addition of 3-methylpiperidine, is reacted with hydrogen in the presence of a first catalyst to give a mixture of the isomeric methyl-5-(3-methylpiperidino)pentanonitriles of formula wherein R1 and R2 are as defined above, which is, in a second stage, hydrogenated in the presence of a second catalyst to give a mixture of the isomeric methyl-5-(3-methylpiperidino)pentanamines (Ia/Ib) and, if desired, this is separated into the two structural isomers. 2. The process as claimed in claim 1, wherein the first catalyst used is a supported palladium catalyst. 3. The process as claimed in claim 2, wherein the supported palladium catalyst used is palladium on aluminium oxide. 4. The process as claimed in claim 1 or 2, wherein the reaction of the 2-methylglutaronitrile with hydrogen is carried out at a temperature of from 100 to 250°C and a pressure of from 20 to 70 bar. 5. The process as claimed in any one of the preceding claims, wherein 1 to 5 times the molar amount of 3-methylpiperidine is added to the 2-methylglutaronitrile. 6. The process as claimed in any one of the preceding claims, wherein the reaction of the 2-methylglutaronitrile with hydrogen is carried out continuously in a fixed-bed reactor. 7. The process as claimed in any one of the preceding claims, wherein the hydrogenation of the methyl-5-(3-methylpiperidino)pentanonitriles (II) is carried out in the presence of ammonia. 8. The process as claimed in any one of the preceding claims, wherein the second catalyst used is a supported rhodium catalyst. 9. The process as claimed in claim 8, wherein the supported rhodium catalyst used is rhodium on activated carbon. 10. The process as claimed in claim 8 or 9, wherein the hydrogenation of the methyl-5-(3-methyl-piperidino)pentanonitriles is carried out at a temperature of from 5 to 100°C and a pressure of from 1 to 50 bar. 11. A process for preparing a methyl-5-(3-methylpiperidino)pentanamine substantially as herein described.

Documents:

0462-mas-1996 abstract-duplicate.pdf

0462-mas-1996 claims-duplicate.pdf

0462-mas-1996 claims.pdf

0462-mas-1996 correspondence-others.pdf

0462-mas-1996 correspondence-po.pdf

0462-mas-1996 description(complete)-duplicate.pdf

0462-mas-1996 description(complete).pdf

0462-mas-1996 form-2.pdf

0462-mas-1996 form-26.pdf

0462-mas-1996 form-4.pdf

0462-mas-1996 form-6.pdf

0462-mas-1996 others.pdf

462.1.jpg

462.2.jpg