Process for preparing phosphorus-containing alpha-aminonitriles

Abstract

The present invention relates primarily to processes for preparing particular phosphorus-containing -aminonitriles of the formulae (Ia) and (Ib) defined hereinafter from corresponding phosphorus-containing cyanohydrin esters and to the use thereof for preparation of glufosinate or of glufosinate salts. The present invention further relates to a process for preparing glufosinate or glufosinate salts.

Claims

1. A process for preparing a mixture comprising at least one compound of the formula (Ia) and at least one compound of the formula (Ib) ##STR00007## wherein a compound of the formula (II) ##STR00008## is reacted with NH.sub.3, using a total of 2.0-3.5 molar equivalents of NH.sub.3, based on the amount of compounds of the formula (II) used, where in each case: R.sup.2 is (C.sub.1-C.sub.12)-alkyl, (C.sub.1-C.sub.12)-haloalkyl, (C.sub.6-C.sub.10)-aryl, (C.sub.6-C.sub.10)-haloaryl, (C.sub.7-C.sub.10)-aralkyl, (C.sub.7-C.sub.10)-haloaralkyl, (C.sub.4-C.sub.10)-cycloalkyl or (C.sub.4-C.sub.10)-halocycloalkyl, R.sup.5 is (C.sub.1-C.sub.12)-alkyl, (C.sub.1-C.sub.12)-haloalkyl, (C.sub.6-C.sub.10)-aryl, (C.sub.6-C.sub.10)-haloaryl, (C.sub.7-C.sub.10)-aralkyl, (C.sub.7-C.sub.10)-haloaralkyl, (C.sub.4-C.sub.10)-cycloalkyl or (C.sub.4-C.sub.10)-halocycloalkyl.

2. The process of claim 1, wherein R.sup.2 is (C.sub.3-C.sub.6)-alkyl, R.sup.5 is (C.sub.1-C.sub.4)-alkyl, (C.sub.6-C.sub.8)-aryl or (C.sub.5-C.sub.8)-cycloalkyl.

3. The process of claim 1, wherein R.sup.2 is (C.sub.4-C.sub.5)-alkyl, R.sup.5 is methyl, ethyl or isopropyl.

4. The process of claim 1, wherein a total amount of 2.0 to 3.0 molar equivalents of NH.sub.3 is used, based on the amount of compounds of the formula (II) used.

5. The process of claim 1, wherein a total amount of 2.3 to 2.8 molar equivalents of NH.sub.3 is used, based on the amount of compounds of the formula (II) used.

6. The process of claim 1, wherein the NH.sub.3 used is essentially anhydrous and the water content in the NH.sub.3 used is not more than 1% by weight.

7. The process of claim 1, wherein the reaction is effected without addition of ammonium chloride (NH.sub.4Cl).

8. The process of claim 1, wherein one or more compounds of the formula (II) as defined in claim 1 are initially charged in liquid form, and NH.sub.3 is added thereto.

9. The process of claim 1, wherein the reaction is effected at a temperature in the range from 0 to 70 C.

10. The process of claim 1, wherein the reaction is effected at a temperature in the range from 15 to 50 C.

11. The process of claim 1, wherein the reaction is effected at an absolute pressure of not more than 5 bar.

12. A process for preparing glufosinate ##STR00009## or glufosinate salts, wherein, in this process, a mixture comprising at least one compound of the formula (Ia) and at least one compound of the formula (Ib) is used ##STR00010## where R.sup.2 has the definition given in claim 1, and the mixture is prepared by the process of claim 1.

13. A process for preparing glufosinate or glufosinate salts comprising the following steps (a) and (b): (a) preparing a mixture prepared by a process in claim 1 and comprising at least one compound of the formula (Ia) and at least one compound of the formula (Ib) as defined in claim 1, and (b) converting the mixture prepared in step (a) and comprising at least one compound of the formula (Ia) and at least one compound of the formula (Ib) to glufosinate or to glufosinate salts.

14. The process of claim 13, wherein, in step (b), an acidic hydrolysis of the nitrile group and the phosphinic ester group of the compound of formula (Ia) and an acidic hydrolysis of the nitrile group of the compound of formula (Ib) are effected.

15. The process of claim 1, wherein the reaction is effected at a temperature in the in the range from 10 to 60 C.

16. The process of claim 1, wherein the reaction is effected at a temperature in the range from 20 to 45 C.

17. The process of claim 1, wherein the reaction is effected at an absolute pressure of not more than 4 bar.

18. The process of claim 1, wherein the reaction is effected at an absolute pressure in the range from 970 mbar to 3 bar.

19. The process of claim 14, wherein the hydrolyses are effected with a mineral acid.

20. The process of claim 19, wherein the mineral acid is aqueous HCl (hydrochloric acid).

Description

EXAMPLES

(1) All data are based on weight unless otherwise stated.

Abbreviations Used

(2) ACM: 3-[n-butoxy(methyl)phosphoryl]-1-cyanopropyl acetate, compound of the formula (II)

(3) AMN: n-butyl (3-amino-3-cyanopropyl)methylphosphinate, compound of the formula (Ia)

(4) Equipment: 500 ml autoclave with internal thermometer and jacket cooling, stirrer, optionally HPLC pump and IR probe (to monitor the reaction).

Example 1

(5) The 500 ml autoclave purged with nitrogen gas was initially charged with 9.6 g of water and 9.3 g of ammonium chloride (corresponding to 0.45 molar equivalent, based on the amount of ACM used), and 57.8 g of aqueous ammonia solution (33% in water, corresponding to 2.9 molar equivalents, based on the amount of ACM used) was added while stirring (600 rpm). Subsequently, 100.92 g of ACM were pumped into the autoclave by means of an HPLC pump, in the course of which the internal temperature rose from initially 20 C. to about 22 C. After the addition of ACM had ended, the mixture was stirred for a further 20 minutes; no further change in the composition of the reaction mixture was recorded by IR probe.

(6) According to .sup.31P NMR, the proportion of the desired compounds of the formulae (Ia) and (Ib) was 90% (the ratio of the amounts of the compounds of the formulae (Ia) and (Ib) by NMR was 69:31).

(7) .sup.31P-NMR (162 MHz, D.sub.2O): (ppm)=63.06/63.05 ppm (69%) and 42.91/42.84 ppm (31%).

Example 2

(8) The water content of the NH.sub.3 used was 0.2% to 0.25% by weight.

(9) The 500 ml autoclave purged with NH.sub.3 gas was initially charged with 252.9 g of ACM (ACM content: 92%) and, at 20 C., while stirring (800 rpm), 42.3 g of NH.sub.3 gas (corresponding to 2.6 molar equivalents, based on the amount of ACM used) were passed into the autoclave within 22 minutes, in the course of which the internal temperature rose to 35 C. and was kept at 35 C. by means of jacket cooling. After 73 minutes, the reaction had ended; no further change in the composition of the reaction mixture was recorded by IR probe.

(10) The reaction mixture from the autoclave was discharged into 400 ml of 32% hydrochloric acid and the resulting mixture was stirred at 110 C. for 7 h, in the course of which volatile components such as water, acetic acid, n-butyl chloride, n-butanol and n-butyl acetate were partly distilled off. This was followed by neutralization with aqueous ammonia solution. The content of glufosinate-ammonium in the solution obtained was 15.9%, corresponding to a yield of 91.5% of theory based on the amount of ACM used.

(11) The determination of the content of glufosinate-ammonium was conducted from a sample neutralized with ammonium hydroxide solution by HPLC with glufosinate-ammonium as external standard and aqueous 0.1 molar KH.sub.2PO.sub.4 solution as eluent.

Example 3

(12) The water content of the NH.sub.3 used was 0.2% to 0.25% by weight.

(13) A 0.5 l autoclave with jacket cooling was initially charged with 252.8 g of ACM (ACM content 90.7%), and the autoclave was purged with nitrogen. At an internal temperature of 22 C., about 8 g of gaseous NH.sub.3 were injected into the solution without cooling while stirring (900 rpm). A temperature rise to 35 C. took place here. Subsequently, the internal temperature was controlled by closed-loop control via the jacket temperature at 33 to 35 C. (cooling via cryostat) and, within 38 minutes, about 34.4 g of NH.sub.3 were added as a gas (42.4 g in total, corresponding to 2.6 equivalents). The maximum internal pressure was 3.5 bar absolute pressure (corresponding to 2.5 bar gauge). At internal temperature 34 C., stirring was continued for a further 96 min, and this reaction mixture was discharged into 507 g of hydrochloric acid (32% in water, corresponding to 4.6 equivalents) (cooling via a water bath). This mixture was then stirred under reflux for 7 h and about 200 ml of distillate were distilled off. The reaction mixture was then cooled down to 22 C. and brought to a pH of 6.5 with ammonia solution (25% in water) and diluted with water (total weight of the solution 1026.2 g; content (HPLC) of glufosinate-ammonium: 16.5%, corresponding to 97% of theory based on the amount of ACM used).

(14) For isolation of glufosinate-ammonium, the procedure followed with the solution was similar to that described in CN102399240A in Example 7: For this purpose, the solution was concentrated, methanol was added, precipitated ammonium chloride was filtered off, and the mother liquor was concentrated under reduced pressure and stirred up once again with methanol and cooled down. The crystallized product was filtered off and washed with methanol. After drying, 192.8 g of solids were obtained (content (HPLC) of glufosinate-ammonium: 81.4%, corresponding to 90.3% of theory based on the amount of ACM used). To verify the content of glufosinate-ammonium, these solids were used to prepare a 50% by weight solution with water (content (HPLC) of glufosinate-ammonium: 40.9%, corresponding to 90.6% of theory).

(15) .sup.31P-NMR (162 MHz, D.sub.2O): (ppm)=56 ppm.