Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1999-10-04
2001-04-10
Vollano, Jean F. (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S141000, C549S480000, C546S308000
Reexamination Certificate
active
06215024
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to novel process for the production of amides from amines using carboxylic acids as the acylating agents and natural/modified montmorillonite clays as catalysts.
This invention particularly relates to an ecofriendly process for the production of amides from aromatic, aliphatic, cyclic, acyclic and heterocyclic amines having carbon atoms in the range of C
1
to C
20
using carboxylic acids as the acylating agents and montmorillonite clays as catalysts and dispensing with the use of expensive corresponding anhydride as a reagent and corrosive, toxic sulfuric acid, hydrochloric acid, sulfonic acids as catalysts. This process totally eliminates the disposal of salts formed consequent to the neutralisation of H
2
SO
4
or sulfonic acids and the use of expensive anhydrides.
BACKGROUND OF THE INVENTION
These amides belong to a very important class of chemicals having applications as intermediates for pharmaceuticals, azo and sulfur dyes, fine chemicals, drugs, as stabilizers for hydrogen peroxide, as photographic chemicals and as antioxidants. N-acetyl p-amino phenol (APAP), commonly known as acetaminophen or paracetamol, is known for a wide variety of uses. Its medicinal use is very well known, notably as a non-prescription analgesic and anti-pyretic agent with properties similar to aspirin. It is also a major component in over 200 other drug formulations.
Amide formation is generally performed with acyl chlorides or anhydrides in presence of bases, 4-dimethylaminopyridine, 4-pyrrolidinopyridine, trimethylamine etc. Lewis acids such as zinc chloride, cobalt chloride, scandium trifluoromethanesulphonate which are good in the acetylation of amines with acetic anhydride generates one molecule of carboxylic acid for every molecule of anhydride consumed and therefore renders the process very expensive. To optimise the yields of ester/amide formation 2-15 molar equivalents of condensing agents such as sulfuric acid, tosylchloride, trifluoroacetic anhydride, polyphosphate ester, N, N
1
-dicyclohexylcarbodiimide, graphite etc., are generally employed. Heterogeneous acidic and superacid catalysts have proved to be useful in some reactions because of their activity, selectivity, reusability, non-corrosivity and virtual absence of effluent treatment which usually is associated with the homogeneous catalysts.
U.S. Pat. No. 2,462,221 Feb. 22, 1949 describes a process wherein acetanilide is prepared by heating aniline with 20% excess of acetic acid in the presence of 2-5% by wt of benzene. The reaction mixture was heated in the range of 130-200° C. Toluidine is acetylated in similar way to get very good yields. U.S. Pat. No. 2,551,047 May 1, 1951 describes a process wherein N-aryl acetamides are prepared by heating an arylamine with up to 25% excess of acetic acid in presence of up to 5% of AcOR, which acts as entrainer of water. The reaction temperatures are in the range of 130-200° C. and the reaction time is 21 hrs for acetanilide preparation. The drawbacks in the above-described processes are that reactions are of quite long duration and the reaction temperatures used are very high. U.S. Pat. No. 4,288,592 Sep. 8, 1981 describes a process wherein the amides are prepared by reacting amines with acid halides or anhydrides in an inert organic diluent, in the presence of molecular sieves. The drawbacks in the above-described processes are that acid halides or anhydrides are used as acylating agents and all the reactions are performed in nitrogen atmosphere.
A communication in J. Chem. Soc., Chem. Commun., 1987,114 discloses the acetylation of amines in presence of acetic anhydride as the acetylating agent and cobalt(II) chloride as catalyst. The drawbacks in the above process are in the use of expensive acetic anhydride.
A communication in J. Chem. Soc., Chem. Commun.,1997,1389, discloses the use of montmorillonite K-10 and KSF catalysts for the acetylation of primary and secondary amines in presence of acetic anhydride the acetylating agent and finds that the results are remarkable. The drawbacks in the above process are the use of an expensive acetic anhydride as acetylating agent. Also, the reactions are not selective i. e., both the functional groups are acetylated in the case of 2-aminophenol, depending upon the molar ratios of the substrate and the acetic anhydride used. Moderate yields are obtained in this process.
In almost all the U.S. Pat. Nos. 4,264,526; 4,264,525; 4,565,890; 3,076,030; 3,341,587 and 5,155,269, the acetylation of p-amino phenol was performed in presence of acetic anhydride/acetic anhydride in aqueous solvent system. U.S. Pat. No. 4,264,526, Apr. 28, 1981 describes a process for the production of aminophenols and N-acetyl p-aminophenol (APAP) comprising alkaline hydrolysis of halonitrobenzene to nitrophenol and from nitrophenols to aminophenols using a borate ion additive during hydrogenation to eliminate undesirable by-products and colour formation. CS Patent 223,945 (Cl. C07C 91/44) Nov. 15, 1985 discloses a process wherein the acetylation of aminophenols with acetic anhydride in ethyl acetate or AcOH gives moderate yields of acetaminophen. The drawbacks in the above processes are the use of acetic anhydride as acetylating agent and the yields are moderate.
U.S. Pat. No. 4,670,589, Jun. 2, 1987 describes a process for the production of APAP by hydrogenation of p-nitrophenol to p-amino phenol (PAP), and concurrently acetylating the PAP with acetic anhydride. U.S. Pat. No. 5,648,535, Jul. 15, 1997, describes a process for the production of N-acylaminophenols by the concurrent hydrogenation of a nitrophenol to an aminophenol and the acylation of the aminophenol with acyl anhydride on a continuous basis in a stirred tank reactor. The drawbacks in the above processes are the use of excess acetic anhydride as acetylating agent/solvent system, difficulty of mono-acetylating the amino group, longer reaction times, oligomerization of the hydroxyl aromatic amine, and color body formation.
Obviously different approaches have been employed both on laboratory and commercial scale to prepare the industrially useful amides, and the traditional homogeneous catalysed reactions are being less favoured owing to the problems of separation and reuse. The present trend is to develop solid acids from cheaply available sources, and especially of clays.
OBJECTS OF THE INVENTION
The main object of the present invention is to provide a novel process for the production of amides from amines, which obviates the drawbacks as detailed above.
Another object of the invention is to provide a process wherein the use of expensive reactants such as anhydrides is obviated.
It is yet another object of the invention to provide a process for the production of amides from amines wherein the formation of excessive effluents is avoided.
Still another object of the present invention is the usage of non-corrosive and cheaply available heterogeneous solid acid catalysts for the first time for easy adaptability in a continuous process.
Still another object of the present invention is to provide a process for the production of amides from amines wherein at least some of the reactants can be recovered by distillation and reused.
It is another object of the invention to provide a process for the formation of amides from amines wherein maximum yields of amides are obtained.
Still another object of the present invention is to provide the process wherein a wider range of amines as starting material can be utilised.
Still another object of the present invention is to provide a process for the production of amides from amines wherein the reaction takes place at lower temperatures.
Yet another object of the present invention is to accomplish the process in short time and in an inexpensive manner.
SUMMARY OF THE INVENTION
These and the other objects of the present invention are achieved by the process of the present invention for the production of amides from amines using a carboxylic acid selected from the group consisting of acetic acid, propionic acid, butyric acid etc
Bhaskar Veldurthy
Choudary Boyapati Manoranjan
Kantam Mannepalli Lakshmi
Raghavan Kondapuram Vijaya
Rao Kottapalli Koteswara
Council of Scientific and Industrial Research
Ladas and Parry
Vollano Jean F.
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