Process for the preparation of 4-alkoxy-3-hydroxypicolinic acids

Patent metadata

Field	Value
Publication number	US-9951018-B2
Application number	US-201715443446-A
Country	US
Kind code	B2
Filing date	Feb 27, 2017
Priority date	Feb 29, 2016
Publication date	Apr 24, 2018
Grant date	Apr 24, 2018

Abstract

4-Alkoxy-3-hydroxypicolinic acids may be conveniently prepared from 2-hydroxypicolinonitrile in a series of chemical steps selected from chlorination, chloro substitution, nitrile hydrolysis and chloro reduction.

First claim

What is claimed is:

1. A process for the preparation of the compound of Formula A

wherein R 1 is a C 1 -C 3 alkyl;
from the compound of Formula B

which comprises the following steps:
a) creating a first mixture by combining together the compound of Formula B and a chlorinating agent;
b) isolating a compound of Formula C from the first mixture;

wherein R is H or Cl;

c) creating a second mixture containing an alkali metal alkoxide of Formula D
MOR 1    D

wherein M is Na or K, and R 1 is a C 1 -C 3 alkyl;

and the compound of Formula C;
d) isolating a compound of Formula E from the second mixture

wherein R is H or Cl and R 1 is a C 1 -C 3 alkyl;

e) creating a third mixture containing the compound of Formula E, water, and one of a mineral acid and a strong base;
f) heating the third mixture;
g) isolating a compound of Formula F from the third mixture

wherein R is H or Cl and R 1 is a C 1 -C 3 alkyl;

h) creating a fourth mixture containing the compound of Formula F and a reducing agent; and
i) isolating the compound of Formula A from the fifth mixture;

wherein R 1 is a C 1 -C 3 alkyl.

2. The process of claim 1 wherein the solvent for the first mixture is selected from the group including water, acetonitrile, sulfolane, DMSO and xylene.

3. The process of claim 1 wherein the chlorinating agent is selected from the group including chlorine, sulfuryl chloride and 1,3-dichloro-5,5-dimethylhydantoin.

4. The process of claim 1 wherein R 1 is CH 3 .

5. The process of claim 1 wherein the mineral acid is sulfuric acid.

6. The process of claim 1 wherein the strong base is sodium hydroxide or potassium hydroxide.

7. The process of claim 1 wherein the reducing agent is comprised of hydrogen and a transition metal catalyst.

8. The process of claim 7 wherein the hydrogen is hydrogen gas and the transition metal catalyst is comprised of palladium on carbon.

Assignees

• Dow Agrosciences Llc

Inventors

• Hanley Patrick S
• Choy Nakyen
• Siddall Thomas L
• Whiteker Gregory T

Classifications

• C07D213/803 Primary

  Processes of preparation · CPC title

• C07D213/84

  Nitriles · CPC title