Cyanoethylation of cycloaliphatic vicinal primary diamines

Details Cyanoethylation of cycloaliphatic vicinal primary diamines Cyanoethylation of cycloaliphatic vicinal primary diamines

2000-08-09

2001-06-12

McKane, Joseph K. (Department: 1626)

Organic compounds -- part of the class 532-570 series

Organic compounds

Nitriles

C558S431000

Reexamination Certificate

active

06245932

ABSTRACT:

BACKGROUND OF THE INVENTION
Processes for the reaction of primary and secondary amines with acrylonitrile to form corresponding cyanoethylamines are well-known. Products that result from the cyanoethylation of organic amines are of industrial importance because they have broad utility in a variety of applications. For example, cyanoethylated amines can be used as coupling components in the preparation of azo dyes for paper and synthetic fibers and so forth. Also, the pendant nitrile groups can be reduced to the amine and thereby generate polyfunctional amines for use as epoxy and isocyanate curatives.
In general, amines add to acrylonitrile more easily than many organic compounds, but the ease of the addition to amines varies considerably. For example, primary amines having two active hydrogen atoms can add one or two acrylonitrile molecules. Addition of the first acrylonitrile molecule to a primary amine may occur at relatively low temperature while addition of the second acrylonitrile molecule may require heating and the use of more rigorous conditions. Stereochemistry between primary or secondary amines and the complexity of the amine also affect the rate of addition of acrylonitrile to the amine.
The following patents represent processes for the cyanoethylation of primary and secondary amines:
U.S. Pat. No. 3,231,601 discloses the cyanoethylation of aromatic amines and points out that primary and secondary aromatic amines are more difficult to cyanoethylate than their aliphatic counterparts. Cyanoethylation of the aromatic amine is effected in good yield by carrying out the reaction in an aqueous medium, i.e. water as the sole solvent, and in the presence of salts of aromatic amines and strong acids as catalysts. The patentees also point out that primary amines are more easily reacted than secondary amines and that steric hindrance of the amine group can affect reactivity, e.g., o-toluidine is less reactive than p-toluidine. Examples of strong acids suited for the catalytic reaction include sulfuric, phosphoric, hydrochloric, p-toluene sulfonic, and trifluoroacetic.
U.S. Pat. No. 3,496,213 discloses the mono-N-cyanoethylation of aromatic amines by reacting the aromatic amine with acrylonitrile in the presence of zinc chloride carried in an aqueous reaction medium. In the process one mole of acrylonitrile is reacted with one mole of monoamine.
U.S. Pat. No. 4,153,567 discloses a process for producing additives for lubricants and fuel which are based on the reaction of the acrylonitrile and vicinal cyclohexanediamine followed by reaction with a heterocyclic imide. In the process, cyanoethylation is effected by reacting 1,2 diaminocyclohexane with acrylonitrile in the presence of an acid catalyst. One and two moles of acrylonitrile are reacted with the vicinal cyclohexylamine to give both the monocyanoethylated product, i.e., N-(2-cyanoethyl)-1,2-diaminocyclohexane and the dicyanoethylated product, i.e., N,N′-di-(2-cyanoethyl)-1,2-diaminocyclohexane. Acid catalysts that may be used include p-toluene-sulfonic acid and acetic acid. Following cyanoethylation the nitrile is reduced to the amine by a catalytic hydrogenation using Raney nickel or other transition metals as catalysts.
U.S. Pat. No. 4,321,354 discloses the production of cycloaliphatic polyamines, particularly the polyamine derived from 1,2-diaminocyclohexane. As in '567, 1,2diaminocyclohexane is reacted with one or two moles acrylonitrile respectively in the presence of an acetic acid catalyst to produce N,N′-di-(2-cyanoethyl)-1,2-diaminocyclohexane. The resultant cyanoethylated diaminocyclohexanes are reduced with hydrogen to form the polyfunctional amines.
BRIEF SUMMARY OF THE INVENTION
This invention relates to an improvement in a process for the cyanoethylation of vicinal cycloaliphatic diamines. The cyanoethylation of the vicinal cycloaliphatic primary amines is carried out in the presence of catalytically effective amount of water and in the substantial absence of inorganic or organic promoters such as acidic compounds. The cyanoethylated cycloaliphatic diamines are represented by this structure
wherein R represents CH
2
and n is an integer from 1 to, 4 for forming a ring and preferably 1 or 2 thereby forming rings of 5 and 6 carbon atoms; R
1
represents H or alkylene groups or substituted alkylene groups having from 1 to 4 carbons atoms, hydroxyalkyl, carboxylic acid, amide, amino, etc., or a fused ring and y is an integer of from 1 to 2 when R
1
is other than hydrogen; and R
2
is H or and, further, at least one R
2
is represented by the formula: —CH
2
—CH
2
—CN.
Vicinal diaminocyclohexanes and derivatives are preferred as the substrate.
There are significant advantages associated with the cyanoethylation process and they include:
an ability to produce the N-(2-cyanoethyl) and N,N′-di-(2-cyanoethyl) vicinal cycloaliphatic diamines in high selectivity;
an ability to effect the cyanoethylation in the presence of water alone without the inclusion of inorganic or organic promoters, such as, acetic components or water-soluble amines which contribute to recovery problems;
an ability to effect the cyanoethylation in water which generates a water-insoluble product that is easily removed from the reaction medium; and,
an ability to produce the N-(2-cyanoethyl) and N,N′-di-(2-cyanoethyl) vicinal cycloaliphatic diamines while obtaining excellent reaction rates.
In a preferred reaction, and used for purposes of illustration, ortho-methylcyclohexyldiamines (H
6
OTD) is reacted with one or 2 moles acrylonitrile using water alone as the catalytic promoter. Reaction is limited to primary amine hydrogen even when molar concentrations of acrylonitrile are greater than 2:1 per mole of primary amine. The primary reaction products produced with water are designated A and B and set forth below. Analysis show that almost no compounds exhibiting secondary amine hydrogen reaction and represented by structures C and D are produced when water alone is used as the catalytic promoter.
DETAILED DESCRIPTION OF THE INVENTION
Processes for the reaction of aliphatic amines and cycloaliphatic amines with crylonitrile to produce cyanoethylated amines are known. Although each hydrogen atom of a primary amine can react with one molar equivalent of acrylonitrile, the primary amine hydrogen atom is more reactive than is a secondary amine hydrogen atom. However, even though the secondary amine hydrogen atom is less reactive it is difficult to control the degree to which secondary amine hydrogen atom reacts in many catalytic processes. Often the reaction product is a mixture of cyanoethylated amines where some of the reaction product exhibits secondary amine reaction thereby resulting in the formation of compounds represented by products of the formulas C and D.
In the current process, one mole of acrylonitrile is reacted with one equivalent of primary amine hydrogen. Thus, in contrast to prior art procedures, water alone, when added in a catalytically effective amount, catalyzes the reaction of the primary amine hydrogen atoms with acrylonitrile to the substantial exclusion of reaction with secondary amine hydrogen atoms. Not only is the reaction selective, but also the rate of cyanoethylation is significantly greater that when no catalyst is employed. Although acidic components such as acetic acid have been used as catalytic promoters, the reaction is not as selective as when water is used as the sole catalyst. Further, the presence of acidic components often leads to contamination requiring greater purification efforts. A catalytic amount of water is used in the reaction. By a catalytic amount, it is meant that the amount of water is sufficient to noticeably increase the rate of reaction. Typically, molar concentrations of water per mole of cycloaliphatic diamine range from about 0.5 to 10:1 preferably from about 1 to 2:1. Excess quantities of water offer no significant advantages.
In the practice of the process described herein, cycloaliphatic vicinal diamines where there are from about 5 to 9 carbon atoms in t

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