PROCESS FOR PRODUCING PHOSPHORUS-CONTAINING CYANOHYDRIN ESTERS

Abstract

The present invention primarily relates to a process for producing certain phosphorus-containing cyanohydrin esters of formula (I) and the use thereof for producing glufosinate/glufosinate salts. The present invention further relates to a process for producing glufosinate/glufosinate salts.

Claims

1. Process for producing a compound of formula (I) ##STR00015## wherein a compound of formula (II) ##STR00016## is reacted with a compound of formula (III) ##STR00017## wherein in each case: R.sup.1 represents (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.2 represents (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.3 and R.sup.4 each independently of one another represent hydrogen, (C.sub.1-C.sub.4)-alkyl, phenyl or benzyl, R.sup.5 represents (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, X represents oxygen or sulfur and n is 0 or 1, in the presence of one or more free-radical-forming substances (IV), wherein two separate mixtures (G1) and (G2) are metered into the reactor and these mixtures (G1) and (G2) have the following composition: mixture (G1) comprises one or more compounds of formula (II) and one or more free-radical-forming substances (IV) and mixture (G2) comprises one or more compounds of formula (III), one or more compounds of formula (II) and optionally one or more free-radical-forming substances (IV).

2. Process according to claim 1, wherein mixture (G1) comprises 10-90 wt % of the entirety of the amount of compounds of formula (II) altogether employed in the mixtures (G1) and (G2).

3. Process according to claim 1, wherein mixture (G1) comprises 20-80 wt % of the entirety of the amount of compounds of formula (II) altogether employed in the mixtures (G1) and (G2).

4. Process according to claim 1, wherein mixture (G1) comprises 25-75 wt % of the entirety of the amount of compounds of formula (II) altogether employed in the mixtures (G1) and (G2).

5. Process according to claim 1, wherein mixture (G1) comprises one or more compounds of formula (II) and 20-100 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the mixtures (G1) and (G2), and mixture (G2) comprises one or more compounds of formula (III), one or more compounds of formula (II) and 0-80 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the mixtures (G1) and (G2).

6. Process according to claim 1, wherein mixture (G1) comprises 25-100 mol %, optional 30-100 mol %, optionally 40-100 mol %, optionally 50-100 mol %, optionally 60-100 mol %, optionally 70-100 mol % and optionally 80-100 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the mixtures (G1) and (G2), and/or mixture (G2) comprises 0-75 mol %, optionally 0-70 mol %, optionally 0-60 mol %, optionally 0-50 mol %, optionally 0-40 mol %, optionally 0-30 mol % and optionally 0-20 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the mixtures (G1) and (G2).

7. Process according to claim 1 the entirety of the compounds (II) and (IV) in the mixture (G1) is 75 to 100 wt %, optionally 80 to 100 wt %, optionally 85 to 100 wt %, optionally 90 to 100 wt %, in each case based on the total weight of the mixture (G1).

8. Process according to claim 1, wherein the mixtures (G1) and (G2) are metered into the reactor predominantly simultaneously, optionally simultaneously.

9. Process according to claim 1, wherein the metering of the mixtures (G1) and (G2) into the reactor is effected substantially continuously, optionally continuously.

10. Process according to claim 1, wherein one, more than one or all of the free-radical-forming substances (IV) conform to formula (V) ##STR00018## wherein R.sup.6 independently at each occurrence represents hydrogen, (C.sub.1-C.sub.10)-alkyl, optionally (C.sub.1-C.sub.6)-alkyl, optionally (C.sub.1-C.sub.4)-alkyl, R.sup.7 represents hydrogen, (C.sub.1-C.sub.10)-alkyl, optionally hydrogen or (C.sub.1-C.sub.6)-alkyl, optionally hydrogen or (C.sub.1-C.sub.4)-alkyl, and R.sup.8 represents methyl, ethyl, 2,2-dimethylpropyl or phenyl.

11. Process according to claim 1, wherein the reaction is effected at a temperature in the range from 40 C. to 120 C., optionally at a temperature in the range from 50 C. to 110 C., optionally at a temperature in the range from 55 C. to 100 C. and optionally at a temperature in the range from 60 C. to 95 C.

12. Process according to claim 1, wherein the molar ratio of the entirety of the employed compound of formula (II) to the entirety of the employed compound of formula (III) is in the range from 8:1 to 1:1, optionally in the range from 5:1 to 2:1.

13. Process according to claim 1, wherein one of the compounds or the compound of formula (II) corresponds to formula (IIa) ##STR00019## wherein R.sup.1 represents (C.sub.1-C.sub.6)-alkyl, (C.sub.1-C.sub.6)-haloalkyl, (C.sub.6-C.sub.8)-aryl, (C.sub.6-C.sub.8)-haloaryl, (C.sub.7-C.sub.10)-aralkyl, (C.sub.7-C.sub.10)-haloaralkyl, (C.sub.5-C.sub.8)-cycloalkyl or (C.sub.5-C.sub.8)-halocycloalkyl and R.sup.2 represents (C.sub.1-C.sub.6)-alkyl, (C.sub.1-C.sub.6)-haloalkyl, (C.sub.6-C.sub.8)-aryl, (C.sub.6-C.sub.8)-haloaryl, (C.sub.7-C.sub.10)-aralkyl, (C.sub.7-C.sub.10)-haloaralkyl, (C.sub.5-C.sub.8)-cycloalkyl or (C.sub.5-C.sub.8)-halocycloalkyl, and one of the compounds or the compound of formula (III) corresponds to formula (IIIa) ##STR00020##

14. Process for producing glufosinate ##STR00021## or one or more glufosinate salts, wherein in said process, a compound of formula (Ib) is employed ##STR00022## wherein R.sup.5 can also represent methyl and production of a compound of formula (Ib) is effected by said process of claim 1.

15. Process for producing one or more glufosinate/glufosinate salts, optionally glufosinate, glufosinate sodium or glufosinate ammonium, comprising: (a) producing of a compound of formula (I)/(Ib) a process of claim 1, (b) using the compound of formula (I)/(Ib) obtained in (a), for producing one or more glufosinate/glufosinate salts, optionally glufosinate, glufosinate sodium or glufosinate ammonium.

Description

EXAMPLES

[0209] All data are based on weight unless otherwise stated.

[0210] Abbreviations used:

[0211] MPE: methanephosphonous acid mono-n-butyl ester

[0212] ACA: acrolein cyanohydrin acetate

[0213] ACM: n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate

Example 1: n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate (ACM)

[0214] Equipment: 500 ml jacketed stirred vessel fitted with a thermometer, impeller stirrer and bottom outlet valve connected to a heatable stirred vessel; two HPLC pumps.

Initiator Reaction:

[0215] A 500 ml jacketed stirred vessel fitted with a thermometer, impeller stirrer (400 rpm) and closed bottom outlet valve under inertization with nitrogen was initially charged with 150 g of MPE (98% purity) and heated to an internal temperature of 85 C. with stirring. 0.9 g of t-butyl peroxyneodecanoate (98% purity, free-radical initiator) were added thereto and 47.9 g of a mixture of 52 g of ACA (98% purity) and 2.7 g of t-butyl peroxyneodecanoate (98% purity, free-radical initiator) were subsequently metered into the reactor (i.e. jacketed stirred vessel) at a constant rate over 2 h via an HPLC pump. The resulting reaction mixture was clear and pale-yellow.

Continuous Metering:

[0216] The reaction temperature was held at 85 C. At the same stirrer speed the following mixtures (G1) and (G2) were simultaneously and uniformly metered into the jacketed stirred vessel via two separate HPLC pumps over a duration of 10 hours:

[0217] Pump 1 metered mixture (G1) composed of 400 g of MPE and 9.6 g of t-butyl peroxyneodecanoate (98% purity) and pump 2 metered mixture (G2) composed of 182 g of ACA and 200 g of MPE.

[0218] Simultaneously, a total of 780 g of the resulting reaction mixture were continuously discharged into the lower stirred vessel via the bottom outlet valve so that the fill-level in the upper jacketed stirred vessel remained constant. In the lower stirred vessel the discharged reaction mixture was subjected to further stirring at 80 C. to 85 C.

[0219] Upon termination of the reaction analysis revealed that the combined total reaction mixture no longer comprised any ACA. GC analysis indicated that the combined total reaction mixture obtained comprised 47.1% MPE and 46.3% ACM. This corresponds to a yield of 447.4 g of ACM (=1.71 mol) corresponding to 95.1% of theory based on the amount of ACA employed.

Example 2: n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate (ACM)

[0220] Equipment: 500 ml jacketed stirred vessel fitted with a thermometer, impeller stirrer and bottom outlet valve connected to a heatable stirred vessel; two HPLC pumps.

[0221] GC and NMR samples were taken and analysed after every substep.

Initiator Reaction:

[0222] A 500 ml jacketed stirred vessel fitted with a thermometer, impeller stirrer (400 rpm) and closed bottom outlet valve under inertization with nitrogen was initially charged with 50 g (0.36 mol) of MPE (98% purity) and heated to an internal temperature of 85 C. with stirring. 0.8 g (0.0033 mol) of the free-radical initiator t-butyl peroxyneodecanoate (98%) were then added and the simultaneous metering of the following mixtures (G1) and (G2) was immediately commenced:

[0223] (G1)=a mixture of 50.0 g (0.36 mol) of MPE (98% purity) and 2.18 g (0.0089 mol) of the free-radical initiator t-butyl peroxyneodecanoate (98% purity) from balance 1 via pump 1 and

[0224] (G2)=a mixture of 40.5 g (0.32 mol) of ACA (99% purity) and 50.0 g (0.36 mol) of MPE (98% purity) from balance 2 via pump 2.

[0225] Holding the internal temperature constant at 85 C., these two mixtures (G1) and (G2) were metered into the reactor over 2.5 hours. At the end of the metering the reaction mixture was almost colourless and clear and ACA was no longer detectable (GC, NMR).

Continuous Metering:

[0226] The internal temperature continued to be held at 85 C. Subsequently, the following mixtures (G1) and (G2) were likewise simultaneously metered into the reactor over 2.5 hours:

[0227] (G1)=a mixture of 50.0 g (0.36 mol) of MPE (98% purity) and 2.18 g (0.0089 mol) of the free-radical initiator t-butyl peroxyneodecanoate (98% purity) from balance 1 via pump 1 and

[0228] (G2)=a mixture of 40.5 g (0.32 mol) of ACA (99% purity) and 50.0 g (0.36 mol) of MPE (98% purity) from balance 2 via pump 2.

[0229] The resulting reaction mixture was meanwhile uniformly discharged into the lower stirred vessel via the bottom outlet valve so that the fill-level in the upper jacketed stirred vessel remained constant. In the lower stirred vessel the discharged reaction mixture was subjected to further stirring at 80 C. At the end of the metering time the reaction mixture obtained was pale-yellow and clear and ACA was no longer detectable (GC, NMR).

[0230] The process described in this continuous metering was subsequently repeated a further 3 times under identical conditions.

[0231] Upon termination of the reaction analysis revealed that the combined total reaction mixture no longer comprised any ACA. The combined total reaction mixture was pale-yellow and clear. GC analysis indicated that the combined total reaction mixture obtained comprised 48.1% MPE and 43.5% ACM. This corresponds to a yield of 1.55 mol of the desired product ACM, corresponding to at least 96.5% of theory based on the amount of ACA employed.

[0232] The separation of MPE and ACM was effected via a short-path, thin-film distillation under vacuum.

Example 3: n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate (ACM)

[0233] The materials, conditions and equipment described in example 1 were employed unless otherwise stated.

[0234] Similarly to example 1, in the initiator reaction 24 g of MPE were initially charged, inertized with nitrogen and heated to 76 C. After addition of 0.1 g of the free-radical initiator 1,1,3,3-tetramethylbutyl peroxyneodecanoate, the following mixtures (G1) and (G2) were simultaneously and uniformly metered from two syringe pumps into the reactor over 2 hours at constant temperature with vigorous stirring: a mixture (G1) of 18.0 g of MPE and 1.2 g of the free radical initiator 1,1,3,3-tetramethylbutyl peroxyneodecanoate and a mixture (G2) of 11.5 g of ACA and 8.0 g of MPE.

Continuous Metering:

[0235] As described hereinabove in the initial part, a mixture (G1) of 36 g of MPE and 2.4 g of the free radical initiator 1,1,3,3-tetramethylbutyl peroxyneodecanoate and a mixture (G2) of 23 g of ACA and 16 g of MPE were then simultaneously and uniformly metered into the reactor over four hours via the two pumps. An additional 48 g of MPE were simultaneously metered in via a dropping funnel.

[0236] In order to maintain a constant fill-level in the reactor, over the entire metering duration, 122 g of reaction mixture were discharged via the bottom valve into a stirred receiver held at 76 C. After a postreaction time of 15 minutes the reaction mixtures obtained were combined. The resulting reaction mixture was pale-yellow and clear. To work up the mixture the low-boiling components were distilled off via a short path evaporator.

[0237] A total of 74.3 g of crude product having an ACM content of 90.8% (GC analysis) were obtained. This corresponds to a yield of 94.8% of theory based on the amount of ACA employed. The crude product remaining in the bottoms was employed directly for further reactions, for example for producing glufosinate ammonium.

Comparative Example 1: n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate (ACM)

[0238] The materials, conditions and equipment described in example 1 were employed unless otherwise stated.

[0239] Under nitrogen, 97.7 g of MPE (98% purity, 0.703 mol) were initially charged and heated to 85 C. After addition of a drop of the free-radical initiator t-butyl peroxyneodecanoate, a mixture of 23.6 g of ACA (98% purity, 0.1848 mol) and 1.2 g of t-butyl peroxyneodecanoate (0.005 mol) were then metered into the reactor at a constant rate over 4 hours via a syringe pump with vigorous stirring at the same temperature. After a postreaction time of 15 min the mixture was cooled to 20 C.

[0240] GC analysis revealed the reaction mixture obtained to comprise 36.1% of the desired product ACM, corresponding to 91.6% of theory.