Process for preparing phosphorus containing cyanohydrins

1. Process for preparing a compound of formula (I)

comprising reacting a compound of formula (II)

with a cyanohydrin of formula (III)

at a temperature in a range from 50 to 105° C.,

where in each case:

R 1 is (C 1 -C 12 )-alkyl, (C 1 -C 12 )-haloalkyl, (C 6 -C 10 )-aryl, (C 6 -C 10 )-haloaryl, (C 7 -C 10 )-aralkyl, (C 7 -C 10 )-haloaralkyl, (C 4 -C 10 )-cycloalkyl or (C 4 -C 10 )-halocycloalkyl,

R 2 is (C 1 -C 12 )-alkyl, (C 1 -C 12 )-haloalkyl, (C 6 -C 10 )-aryl, (C 6 -C 10 )-haloaryl, (C 7 -C 10 )-aralkyl, (C 7 -C 10 )-haloaralkyl, (C 4 -C 10 )-cycloalkyl or (C 4 -C 10 )-halocycloalkyl,

R 3 and R 4 are in each case independently of one another hydrogen, (C 1 -C 4 )-alkyl, phenyl or benzyl,

X is oxygen or sulphur, and

n is 0 or 1.

2. Process according to claim 1 , wherein the reacting takes place at a temperature in a range from 60 to 95° C.

3. Process according to claim 1 , wherein the reacting takes place at a temperature in a range from 65 to 90° C.

4. Process according to claim 1 , wherein a compound of formula (IIa)

is reacted with an acrolein cyanohydrin of formula (IIIa)

where:

R 1 is (C 1 -C 6 )-alkyl, (C 1 -C 6 )-haloalkyl, (C 6 -C 8 )-aryl, (C 6 -C 8 )-haloaryl, (C 7 -C 10 )-aralkyl, (C 7 -C 10 )-haloaralkyl, (C 5 -C 8 )-cycloalkyl or (C 5 -C 8 )-halocycloalkyl,

R 2 is (C 1 -C 6 )-alkyl, (C 1 -C 6 )-haloalkyl, (C 6 -C 8 )-aryl, (C 6 -C 8 )-haloaryl, (C 7 -C 10 )-aralkyl, (C 7 -C 10 )-haloaralkyl, (C 5 -C 8 )-cycloalkyl or (C 5 -C 8 )-halocycloalkyl.

5. Process according to claim 1 , wherein the reacting is carried out with aid of a radical-forming radiation source or in the presence of one or more radical-forming substances.

6. Process according to claim 1 , wherein the reacting takes place in the presence of one or more radical initiators of formula (IV)

where

R 5 is methyl, ethyl, 2,2-dimethylpropyl or phenyl,

R 6 independently at each occurrence is (C 1 -C 10 )-alkyl and

R 7 is hydrogen or (C 1 -C 10 )-alkyl.

7. Process according to claim 6 , wherein the reacting takes place in the presence of one or more radical initiators selected from the group consisting of tert-butyl peroxypivalate, tert-amyl peroxypivalate, tert-butyl peroxyneodecanoate, 1,1,3,3-tetramethylbutyl peroxyneodecanoate, tert-butylperoxy-2-ethylhexanoate, 1,1,3,3-tetramethylbutyl peroxy-2-ethylhexanoate, tert-amyl peroxyneodecanoate, cumyl peroxyneodecanoate, cumyl peroxyneoheptanoate, and cumyl peroxypivalate.

8. Process according to claim 6 , wherein R 6 independently at each occurrence is (C 1 -C 4 )-alkyl and R 7 is hydrogen or (C 1 -C 4 )-alkyl.

9. Process according to claim 1 , wherein the molar ratio of the total amount of the phosphorus-containing reactant (II) used to the total amount of the cyanohydrin of the formula (III) used is in a range from 2:1 to 8:1.

10. Process according to claim 6 , wherein the radical initiator or initiators of the formula (IV) or a portion of the radical initiators of the formula (IV) is premixed with a portion or the entirety of compound (II), and this mixture is metered into the reaction vessel simultaneously with the compound of the formula (III).

11. Process according to claim 1 , wherein R 1 is methyl, R 2 is n-butyl, R 3 and R 4 are hydrogen, n is 1 and X is oxygen.

12. Process according to claim 1 , further comprising preparing one or more glufosinate and/or glufosinate salts

wherein the compound of formula (I) comprises a compound of formula (Ib) comprising:

reaction of a compound of the formula (Ib) to give a corresponding compound of formula (V),

where R 2 is in each case either n-butyl or n-pentyl, and reacting a compound of formula (V) to give the glufosinate or a salt thereof.

13. Process according to claim 12 , wherein the preparation of compound (V) takes place by reaction of compound (Ib) with NH 3 .