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 sulphur and n is 0 or 1, in the presence of one or more free-radical-forming substances (IV), wherein a metered stream (D1) is metered into the reactor, which comprises one or more compounds of formula (II) and one or more free-radical-forming substances (IV), and wherein metered stream (D1) comprises 25-100 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the reaction.

2. Process according to claim 1, wherein two separate metered streams (D1) and (D2) are metered into the reactor and these metered streams (D1) and (D2) have the following composition: metered stream (D1) comprises one or more compounds of formula (II) and one or more free-radical-forming substances (IV), wherein metered stream (D1) comprises 25-100 ml % of the amount of the free-radical-forming substances (IV) altogether employed in the reaction and metered stream (D2) comprises one or more compounds of formula (III) and also optionally one or more compounds of formula (II) and optionally one or more free-radical-forming substances (IV).

3. Process according to claim 1, wherein metered stream (D1) comprises 30-100 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the reaction, optionally by preference 40-100 mol %, optionally 50-100 mol %, optionally 60-100 mol %, optionally 70-100 mol %, optionally 80-100 mol %, optionally 90-100 mol % and optionally 95-100 mol %.

4. Process according to claim 2, wherein metered stream (D1) comprises 90-100 wt %, optionally (D1) comprises 95-100 wt %, optionally 100 wt %, of the entirety of the amount of compounds of formula (II) altogether employed in the metered streams (D1) and (D2).

5. Process according to claim 2, wherein metered stream (D2) comprises 80-100 wt %, optionally 90-100 wt %, optionally 95-100 wt %, optionally 100 wt %, of the entirety of the amount of compounds of formula (III) altogether employed in the metered streams (D1) and (D2).

6. Process according to claim 2 metered stream (D1) comprises 40-100 mol %, optionally 50-100 mol %, optionally 60-100 mol %, optionally 70-100 mol %, optionally 80-100 mol % and optionally 90-100 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the metered streams (D1) and (D2) and/or metered stream (D2) comprises 0-60 mol %, optionally 0-50 mol %, optionally 0-40 mol %, optionally 0-30 mol %, optionally 0-20 mol % and optionally 0-10 mol % of the entirety of the amount of the free-radical-forming substances (IV) altogether employed in the metered streams (D1) and (D2).

7. Process according to claim 1, wherein the entirety of the compounds (II) and (IV) in the metered stream (D1) 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 metered stream (D1).

8. Process according to claim 2, wherein the metered streams (D1) and (D2) are metered into the reactor predominantly simultaneously, optionally simultaneously.

9. Process according to claim 2, wherein the metering of the metered streams (D1) and (D2) 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, by preference (C.sub.1-C.sub.6)-alkyl, preferably (C.sub.1-C.sub.4)-alkyl, R.sup.7 represents hydrogen or (C.sub.1-C.sub.10)-alkyl, by preference hydrogen or (C.sub.1-C.sub.6)-alkyl, preferably 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 preferably 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 comprise methyl and Wherein production of the compound of formula (Ib) is effected by a process of claim 1.

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

Description

EXAMPLES

[0213] All data are based on weight unless otherwise stated.

[0214] Abbreviations used:

[0215] MPE: methanephosphonous acid mono-n-butyl ester

[0216] ACA: acrolein cyanohydrin acetate

[0217] ACM: n-butyl (3-cyano-3-acetoxypropyl)methylphosphinate

Example 1

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

[0218] Discontinuous Mode of Operation

[0219] A temperature-controllable, cylindrical glass reactor was filled with a portion of the required MPE to adequately cover the stirring means and the reactor contents were brought to reaction temperature (typically 85 C.). In the experiments with a pumped circulation system/circulation loop, the circulation loop including the associated pump was also filled with MPE. Commixing of the reactor contents was accomplished via a six-blade disc stirrer in combination with four baffles. The reactor contents were always blanketed with nitrogen and the reactor was operated without application of superatmospheric pressure.

[0220] To ensure reliable starting of the reaction (i.e. reliable initiation), 5 minutes before commencement of the metering of the reactants into the reactor a small amount of initiator (0.9-1.0 mL, corresponding to about 0.8-0.9 g) was injected into the initially charged MPE previously heated to reaction temperature (and possibly also circulating through the circulation loop). The time interval of 5 minutes corresponds approximately to the half-life of the free-radical initiator tert-butyl perneodecanoate at 85 C. Toward the end of the metering time of 4 hours (i.e. more than 40 half-lives of the employed free-radical initiator) the initially injected amount of tert-butyl perneodecanoate had fallen to <10.sup.12 parts of the starting amount and thus had no appreciable further relevance for any subsequent experiments (for example the ACM production in the continuous mode of operation).

[0221] The metered streams (D1) and (D2) were then separately metered into the reactor until the desired fill-level had been achieved, taking into account the respective stoichiometries.

[0222] 142.0 g of MPE (98% purity) were initially charged and heated to 85 C. 5 min before commencement of the metered streams (D1) and (D2), 1.0 ml (about 0.9 g) of the free-radical initiator tert-butyl perneodecanoate (98% purity) was added. The following metered streams (D1) and (D2) were then simultaneously metered into the reactor over a period of 4.0 h:

[0223] metered stream (D1) was a mixture of MPE (102.1 g, 98% purity) and tert-butyl perneodecanoate (3.0 g, 98% purity), metered stream (D2) was composed of 57.0 g of ACA (99% purity).

[0224] The concentration of the free-radical initiator was accordingly 1.0 wt % based on the overall mixture.

[0225] The employed ACA had reacted completely; the yield for the reaction of ACA to afford ACM was 98-99%. After expiry of the metering time the discontinuous batch had reached its endpoint and it was possible to switch to the continuous mode of operation (see Example 2 herein below).

Example 2

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

[0226] Continuous Mode of Operation

[0227] The reactor was initially charged with a mixture produced by the discontinuous mode of operation according to hereinabove-reported example 1. The reaction conditions and the apparatus parameters were the same as those from example 1. At a reaction temperature of 85 C., the metered streams (D1) and (D2) were then simultaneously and separately metered into the reactor.

[0228] At 85 C., metered stream (D1), a mixture of MPE and free-radical initiator tert-butyl perneodecanoate, was added to the reactor at 63 mL/h and metered stream (D2), ACA, was added to the reactor at 14 mL/h, the content of the free-radical initiator in the MPE (1.2 wt %) being chosen such that a content of 1.0 wt % of free-radical initiator in the overall mixture in the reactor was achieved. Commixing of the reactor contents was accomplished via a six-blade disc stirrer in combination with four baffles.

[0229] Corresponding to the supplied volume flows, an adequately large volume flow of the reactor mixture was withdrawn from the reactor to keep the fill-volume in the reactor constant. The fill-volume in the reactor and the supplied/discharged volume flows resulted in an average hydrodynamic residence time of 4.0 hours in the reactor.

[0230] Once a steady-state had been achieved, samples of the reactor contents were withdrawn and a yield of 95-96% for the reaction of ACA to afford ACM was determined.

Example 3

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

[0231] Equipment: 500 ml jacketed stirred vessel fitted with a thermometer, impeller stirrer and bottom outlet valve; two pumps.

[0232] 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 100.0 g of a reaction mixture from an earlier reaction batch (composition as per GC: 36% MPE and 56.7% ACM) and heated to 85 C. 1.0 g (0.00405 mol) of the free-radical initiator t-butyl peroxyneodecanoate was added thereto.

[0233] The following metered streams (D1) and (D2) were then simultaneously uniformly metered into the jacketed stirred vessel from two balances by means of two pumps over a period of 135 minutes, the internal temperature being held at 85 C.:

[0234] Metered stream (D1) was a mixture of 25.0 g (0.18 mol) of MPE (99% purity) and 0.9 g of the free-radical initiator t-butyl peroxyneodecanoate (98% purity) and metered stream (D2) was composed of 10.0 g (0.079 mol) of ACA (99% purity).

[0235] This metering procedure was then repeated once more under the same conditions with the same amounts of the identically composed metered streams (D1) and (D2).

[0236] The reaction mixture obtained after termination of the reaction was clear and pale-yellow and no longer contained any ACA according to analysis. After cooling the reaction mixture (171.5 g) was analyzed (GC and NMR), it comprised 39% MPE and 54.7% ACM. The yield corresponded to 96% of theory based on the employed amount of ACA. Separation of MPE and ACM was then effected via short path thin-film distillation under vacuum.

Comparative Example 1

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

[0237] The materials, conditions and equipment described in Example 1 were employed unless otherwise stated.

[0238] 97.7 g of MPE (98% purity; 0.703 mol) were initially charged and heated to 85 C. under nitrogen. After addition of a drop of the free-radical initiator t-butyl peroxyneodecanoate, at the same temperature a mixture of 23.6 g of ACA (98% purity; 0.1848 mol) and 1.2 g of t-butyl peroxyneodecanoate (0.005 mol) was then metered via a syringe pump into the reactor over 4 hours at a constant rate with vigorous stirring. After a postreaction time of 15 min the mixture was cooled to 20 C.

[0239] According to GC analysis the obtained reaction mixture comprised 36.1% of the desired product ACM, corresponding to 91.6% of theory.