Processes for the diazotization of 2,5-dichloroanilines

Patent metadata

Field	Value
Publication number	US-9878978-B2
Application number	US-201715619711-A
Country	US
Kind code	B2
Filing date	Jun 12, 2017
Priority date	Dec 18, 2013
Publication date	Jan 30, 2018
Grant date	Jan 30, 2018

Abstract

The present disclosure relates, in general, to processes for converting 2,5-dichloroaniline compounds to the corresponding 2,5-dichlorobenzenediazonium compounds, and further relates to processes for the preparation of 2,5-dichlorophenol which is a key intermediate used in the manufacture of dicamba.

First claim

What is claimed is:

1. A process for the preparation of a compound corresponding in structure to Formula (VI):

or a salt thereof, the process comprising:
contacting a compound corresponding in structure to Formula (III-a):

or a salt thereof, with a diazotizing agent in a reaction medium comprising sulfuric acid and an organic acid selected from the group consisting of C 2 -C 6 -alkanoic acids and halo-C 1 -C 6 -alkanoic acids to generate a diazonium product mixture comprising a compound corresponding in structure to Formula (IV-a):

or a salt thereof;
hydrolyzing the compound or salt of Formula (IV-a) to generate a phenol product mixture comprising a compound corresponding in structure to Formula (V-a):

or a salt thereof; and
carboxylating the compound or salt of Formula (V-a) to generate a carboxylated product mixture comprising a compound corresponding in structure to Formula (V-b):

or a salt thereof; and
converting the compound or salt of Formula (VI-b) to the compound or salt of Formula (VI), wherein the converting step comprises:
methylating the compound or salt of Formula (V-b) to generate a methylated product mixture comprising a compound corresponding in structure to Formula (V-c):

or a salt thereof; and
selectively demethylating the compound or salt of Formula (V-c) to generate a dicamba product mixture comprising the compound or salt of Formula (VI); or the converting step comprises:
selectively methylating the compound or salt of Formula (V-b) to generate a dicamba product mixture comprising the compound or salt of Formula (VI).

2. The process of claim 1 , wherein the converting step comprises:
methylating the compound or salt of Formula (V-b) to generate a methylated product mixture comprising a compound corresponding in structure to Formula (V-c):

or a salt thereof; and
selectively demethylating the compound or salt of Formula (V-c) to generate a dicamba product mixture comprising the compound or salt of Formula (VI).

3. The process of claim 1 , wherein the converting step comprises:
selectively methylating the compound or salt of Formula (V-b) to generate a dicamba product mixture comprising the compound or salt of Formula (VI).

4. The process of claim 2 , wherein the process comprises concurrently introducing the diazotizing agent and a solution comprising the organic acid and the compound or salt of Formula (III) into the reaction medium.

5. The process of claim 2 , wherein
the process comprises:
forming a reaction medium comprising sulfuric acid; an organic acid selected from the group consisting of C 2 -C 6 -alkanoic acids and halo-C 1 -C 6 -alkanoic acids; and the compound or salt of Formula (III-a); and
introducing into the reaction medium a diazotizing agent to generate a diazonium product mixture comprising the compound or salt of Formula (IV-a).

6. The process of claim 2 , wherein
the process comprises:
forming a reaction medium comprising sulfuric acid; an organic acid selected from the group consisting of C 2 -C 6 -alkanoic acids and halo-C 1 -C 6 -alkanoic acids; and, optionally, a first amount of the compound or salt of Formula (III-a); and
introducing into the reaction medium a second amount of the compound or salt of the compound of Formula (III), and a diazotizing agent, to generate a diazonium product mixture comprising the compound or salt of Formula (IV-a).

7. The process of claim 2 wherein the organic acid is selected from the group consisting of acetic acid and trifluoroacetic acid.

8. The process of claim 7 wherein the organic acid is acetic acid.

9. The process of claim 2 wherein the diazotizing agent introduced into the reaction medium is nitrosylsulfuric acid.

10. The process of claim 2 wherein the diazotizing agent introduced into the reaction medium is an alkali metal nitrite.

11. The process of claim 10 wherein the diazotizing agent comprises sodium nitrite or calcium nitrite.

12. The process of claim 2 wherein the process comprises concurrently introducing the diazotizing agent, the organic acid, and the compound or salt of Formula (III-a) into the reaction medium.

13. The process of claim 2 wherein the molar ratio of the organic acid to the sulfuric acid is from about 30:1 to about 1:10.

14. The process of claim 2 wherein the process further comprises adding a quenching agent to the diazonium product mixture in an amount sufficient to decompose any remaining diazotizing agent prior to the hydrolyzing step.

15. The process of claim 2 wherein the compound or salt of Formula (IV-a) is not isolated from the diazonium product mixture prior to being hydrolyzed, and the process comprises hydrolyzing the compound or salt of Formula (IV-a) contained in the diazonium product mixture to generate a phenol product mixture comprising the compound or salt of Formula (V-a).

16. The process of claim 2 wherein the hydrolyzing step comprises subjecting the diazonium product mixture to steam distillation to generate the phenol product mixture comprising the compound or salt of Formula (V-a).

17. The process of claim 16 wherein the phenol product mixture resulting from the steam distillation is a distillate comprising the organic acid, water, and the compound or salt of Formula (V-a).

18. The process of claim 17 wherein the process further comprises recovering the organic acid from the distillate and recycling the recovered organic acid to a prior process step.

19. The process of claim 2 wherein the process further comprises recovering sulfuric acid from the hydrolysis step and recycling the recovered sulfuric acid to a prior process step.

20. The process of claim 2 wherein the process further comprises reducing a compound corresponding in structure to Formula (II):

or a salt thereof, to generate the compound or salt of Formula (III-a).

21. The process of claim 20 wherein the reducing step is conducted in a solvent comprising the organic acid used in the diazotizing step.

22. The process of claim 20 wherein the process further comprises recovering the organic acid from the hydrolyzing step and recycling the recovered organic acid to the reducing step.

Assignees

• Monsanto Technology Llc

Inventors

• De Kort Bruno
• Mcreynolds Matthew D
• Parlow John J
• Woerndle Rhonda S

Classifications

• C07C245/20 Primary

  Diazonium compounds · CPC title

• C07C209/365

  by reduction with preservation of halogen-atoms in compounds containing nitro groups and halogen atoms bound to the same carbon skeleton · CPC title

• C07C51/09

  from carboxylic acid esters or lactones · CPC title

• A01N37/40

  having at least one carboxylic group or a thio analogue, or a derivative thereof, and one oxygen or sulfur atom attached to the same aromatic ring system · CPC title

• C07C37/045

  by substitution of a group bound to the ring by nitrogen · CPC title