Method for preparing acrolein cyanohydrins

Patent metadata

Field	Value
Publication number	US-10214484-B2
Application number	US-201815936868-A
Country	US
Kind code	B2
Filing date	Mar 27, 2018
Priority date	Apr 21, 2017
Publication date	Feb 26, 2019
Grant date	Feb 26, 2019

Abstract

The present invention relates to an improved method for preparing acrolein cyanohydrins from hydrocyanic acid and the corresponding acroleins. The method is characterized in that the acrolein cyanohydrins obtained have a very low hydrocyanic acid content or are free of hydrocyanic acid and are therefore particularly well suited as intermediates for the synthesis of glufosinates.

First claim

The invention claimed is:

1. A method for preparing a compound of formula (I)

the method comprising:
(a) reacting at least one compound of the formula (II)

with hydrocyanic acid and at least one base B, whereby a crude product CP comprising the compound of formula (I) and hydrocyanic acid is obtained; and
b) at least partially removing hydrocyanic acid from the crude product CP by subjecting the latter to stripping, whereby a pure product comprising the compound (I) is obtained, wherein the pure product has a reduced content of hydrocyanic acid compared to CP,
wherein the stripping is carried out at a pressure of <1 bar,
wherein optionally an inert stripping gas is used in countercurrent flow, and
wherein R 1 and R 2 are each independently hydrogen, an alkyl group, phenyl, or benzyl.

2. The method according to claim 1 , wherein
R 1 and R 2 are each independently hydrogen, an alkyl group having 1 to 6 carbon atoms, phenyl, or benzyl.

3. The method according to claim 1 , wherein
R 1 and R 2 are each hydrogen.

4. The method according to claim 1 , wherein
the base B is at least one member selected from the group consisting of ammonia, a trialkylamine, and an ammonium salt.

5. The method according to claim 1 , wherein
said a) reacting is conducted at a temperature of from 50° C. to 80° C.

6. The method according to claim 1 , wherein
the hydrocyanic acid in said a) reacting is present in an amount of >1 molar equivalent, based on the amount of all compounds of the formula (II) present in said a) reacting.

7. The method according to claim 1 , wherein
the amount of base B in said a) reacting is 0.01 to 5% by weight, based on the sum of the weights of hydrocyanic acid present in said a) reacting and all compounds of the formula (II) present in step said a) reacting.

8. The method according to claim 1 , wherein
the crude product CP is mixed prior to the at least partially removing of b) with at least one acid so that, after mixing with the acid, CP has a pH of <6.9.

9. The method according to claim 8 , wherein
the at least one acid has a pKa of ≤1.

10. The method according to claim 8 , wherein
the acid is at least one member selected from the group consisting of mineral acid, an alkylcarboxylic acid, and an aromatic sulfonic acid.

11. The method according to claim 1 , wherein
a temperature of ≤85° C. is maintained during the stripping in the at least partially removing of b).

12. The method according to claim 1 , wherein
the crude product CP during the stripping in the at least partially removing of b) is passed at least partially over a bed of packing elements or over a structured packing.

13. The method according to claim 1 , further comprising, after b):
c) reacting the pure product comprising the compound (I) obtained in b), wherein the pure product has a reduced content of hydrocyanic acid compared to CP, with a compound of the formula (IV)

to obtain a compound of the formula (III)

wherein R 3 , R 4 are each independently an (halo)alkyl group, an (halo)aryl group, a (halo)aralkyl group, or a (halo)cycloalkyl group,
wherein X is oxygen or sulfur, and
wherein n=0 or 1.

14. The method according to claim 13 , wherein the reaction in said c) reacting is conducted at a temperature of 50° C. to 105° C.

15. The method according to claim 13 , wherein
each of R 3 and R 4 is, independently, a (halo)alkyl group having 1 to 12 carbon atoms, a (halo)aryl group having 6 to 10 carbon atoms, a (halo)aralkyl group having 7 to 10 carbon atoms, or a (halo)cycloalkyl group having 4 to 10 carbon atoms.

16. The method according to claim 13 , wherein
at least one free-radical-forming substance is present in said c) reacting.

17. The method according to claim 16 , wherein
the free-radical-forming substance is a free-radical initiator of the formula (V)

wherein R 5 is methyl, ethyl, 2,2-dimethylpropyl, or phenyl,
wherein R 6 , R 7 are each independently an alkyl group having 1 to 10 carbon atoms, and
wherein R 8 is hydrogen or an alkyl group having 1 to 10 carbon atoms.

Assignees

• Evonik Degussa Gmbh

Inventors

• Omeis Marianne

Classifications

• C07F9/3211

  Esters of acyclic saturated acids which can have further substituents on alkyl · CPC title

• C07C253/10 Primary

  to compounds containing carbon-to-carbon double bonds · CPC title

• C07C253/34

  Separation; Purification · CPC title

• C07C409/38

  the —O—O— group being bound between a >C=O group and a carbon atom, not further substituted by oxygen atoms, i.e. esters of peroxy acids · CPC title

• C07C29/14

  of a —CHO group · CPC title