Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-09-27
2001-06-05
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
Reexamination Certificate
active
06242646
ABSTRACT:
The present invention is described in the German priority application No. DE 198 13 886.5, filed Mar. 27, 1998, which is hereby incorporated by reference as is fully disclosed herein.
BACKGROUND OF THE INVENTION
The present invention relates to a process for preparing 2,4-dichloro-5-hydroxyacetanilide, said process being an advance on the prior art.
2,4-Dichloro-5-hydroxyacetanilide is an important intermediate in the preparation of crop protection agents (WO 85/01939).
2,4-Dichloro-5-hydroxyacetanilide can be prepared by chlorination of 3-hydroxyacetanilide, which is obtainable by acetylation of 3-aminophenol.
The reaction of 3-hydroxyacetanilide with gaseous chlorine in glacial acetic acid described in WO 86/00072 on page 25 under Example III Step B leads to a yield of only 30.4% of theory, based on 3-hydroxyacetanilide employed.
With reference to Example 2 Step B, WO 85/01939 describes, on page 27 under Example 3 Step B, the reaction of 3-hydroxyacetanilide with sulfuryl chloride in glacial acetic acid. According to the specifications on page 25 Example 2 Step B, in the preparation of 2,4-dichloro-5-methylacetanilide, the reaction mixture is, after the addition of sulfuryl chloride to 3-acetamidotoluene, allowed to stand at room temperature for approximately 60 hours and subsequently heated, until a stirrable material is formed, and then stirred for approximately 5 hours more. The 2,4-dichloro-5-hydroxyacetanilide prepared in accordance with Example 3 Step B in a similar manner to Example 2 Step B is obtained in a yield of 43.5%, based on 3-hydroxyacetanilide employed.
The yields of 2,4-dicholor-5-hydroxyacetanilide obtained in the two examples described above are comparatively low, and the processes are therefore not to be recommended for industrial realization.
SUMMARY OF THE INVENTION
It was therefore the object to develop a process which on the one hand can be realized industrially in a simple manner and which additionally makes available, at reasonable cost, 2,4-dicholor-5-hydroxyacetanilide, in high yields and at the same time in high purity.
DESCRIPTION OF THE PREFERRED EMBODIMENT
This object is achieved by a process for preparing 2,4-dichloro-5-hydroxyacetanilide by reacting 3-hydroxyacetanilide with sulfuryl chloride in the presence of from 3 to 30 parts by weight of an aliphatic carboxylic acid having from 1 to 6 carbon atoms per part by weight of 3-hydroxyacetanilide with vigorous mixing at from 20 to 100° C., removing gaseous components from the reaction mixture, setting a ratio of from 1.0 to 6 parts by weight of aliphatic carboxylic acid per part by weight of 3-hydroxyacetanilide employed and removing 2,4-dichloro-5-hydroxyacetanilide as a solid.
With a view to the preparation of 2,4-dichloro-5-hydroxyacetanilide described in WO 85/01939 under Example 3 Step B, it is very surprising that the process according to the invention affords the desired 2,4-dicholor-5-hydroxyacetanilide in a yield of from 80 to 85% and more, based on the 3-aminophenol required for preparing 3-hydroxyacetanilide. The process can be realized without any particular technical expense even at relatively low temperatures and short reaction times. The acetic acid which is separated off during the operation according to the invention can be recycled as solvent/suspending medium into the reaction.
In general, from 1.5 to 5, in particular from 1.8 to 2.5, preferably from 1.9 to 2.2, mol of sulfuryl chloride are employed per mole of 3-hydroxyacetanilide.
Based on 3-hydroxyacetanilide, the aliphatic carboxylic acid is added in such an amount that sufficient mixing of the reaction mixture is ensured during the reaction.
In a large number of cases this is ensured by carrying out the reaction of 3-hydroxyacetanilide with sulfuryl chloride in the presence of from 4 to 15, in particular from 4.5 to 13, preferably from 5 to 10, particularly preferably from 5 to 7, parts by weight of aliphatic carboxylic acid per part by weight of 3-hydroxyacetanilide.
Suitable aliphatic carboxylic acids are formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid, 3-methylbutyric acid, valeric acid, n-hexanoic and isohexanoic acid. It is also possible to employ mixtures of the abovementioned carboxylic acids. The aliphatic carboxylic acids or their mixtures are employed in anhydrous form.
Particularly suitable aliphatic carboxylic acids are formic acid, acetic acid, propionic acid, n-butyric acid, isobutyric acid or mixtures of these carboxylic acids, in particular formic acid, acetic acid or propionic acid, preferably acetic acid.
In a large number of cases it was found to be advantageous to react 3-hydroxyacetanilide with sulfuryl chloride at from 25 to 70, in particular from 40 to 60 ° C.
The process can be carried out in a particularly simple manner by initially charging the 3-hydroxyacetanilide and the aliphatic carboxylic acid, and adding the sulfuryl chloride while mixing. The rate of addition of the sulfuryl chloride is chosen such that the heat of reaction and the gaseous components which are formed (SO
2
, HCl) can be drawn off. The reaction time depends essentially on the rate of addition of the sulfuryl chloride and the practicability of being able to draw off both the heat of reaction and the gaseous components (waste gases) at a sufficient rate.
During the reaction, it has to be ensured that gaseous components can escape from the reaction mixture. After the addition of sulfuryl chloride has ended, the mixture is allowed to react for a sufficient extra time to bring the reaction to completion and to remove any gaseous components which may still be present.
During the reaction, it has to be ensured that the reactants are thoroughly mixed. Efficient mixing also facilitates the required removal of gaseous components from the reaction mixture during the reaction and the extra reaction time.
The gaseous components which are still dissolved after the reaction with sulfuryl chloride, for example HCl and SO
2
, are usually removed at a pressure of from 10 mbar to atmospheric pressure, in particular from 20 mbar to 500 mbar, preferably from 50 to 250 mbar. It has to be ensured that the gaseous components are as substantially separated off from the reaction mixture as possible. Insufficient removal of the gaseous components from the reaction mixture can have disadvantageous consequences both for the yield and the purity of the end product.
In many cases, it was found to be advantageous to remove gaseous components at from 25 to 100° C., in particular from 40 to 70° C.
When separating off the gaseous components, temperature and pressure are usually chosen such that the gaseous components are removed, but not the aliphatic carboxylic acid. Thus, it is ensured that, when the aliphatic carboxylic acid is separated off by distillation, an aliphatic carboxylic acid obtained is not contaminated by HCl and SO
2
.
As already mentioned, the ratio of aliphatic carboxylic acid to 3-hydroxyacetanilide employed is set to from 1.0 to 6, in particular from 1.5 to 5, preferably from 1.5 to 4.5, particularly preferably from 2 to 4, parts by weight of aliphatic carboxylic acid per part by weight of 3-hydroxyacetanilide employed by separating off, if required, the aliphatic carboxylic acid from the reaction mixture until the abovementioned ratio is obtained, or, if required, adding an appropriate amount of aliphatic carboxylic acid. It may not be necessary to adjust this ratio separately if, in the reaction of 3-hydroxyacetanilide with sulfuryl chloride, a ratio of aliphatic carboxylic acid to 3-hydroxyacetanilide employed which is suitable for separating off 2,4-dichloro-5-hydroxyacetanilide is set at the beginning.
The ratio of aliphatic carboxylic acid to 3-hydroxyacetanilide employed should be such that, on the one hand, the 2,4-dicholor-5-hydroxyacetanilide precipitates out as a solid as completely as possible and that, on the other hand, the reaction mixture which is obtained has sufficient flowability for further work-up (filtration, centrifugation).
In a large number of cases it was found advantageous to disti
Krause Stefan
Leitung Hans-Jürgen
Sistig Frank
Barts Samuel
Clariant GmbH
Hanf Scott E.
LandOfFree
Method of producing 2,4-dichloro-5-hydroxyacetanilide does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing 2,4-dichloro-5-hydroxyacetanilide, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing 2,4-dichloro-5-hydroxyacetanilide will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2503023