Processes for the reaction of primary and secondary amines with acrylonitrile to form corresponding cyanoethylamines are known. The 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. 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 are more reactive with acrylonitrile than many other classes of organic compounds, but the ease of the addition among 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 may require heating and the use of more rigorous conditions. Stereochemistry between primary and 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 (Peterli, 1966) discloses the cyanoethylation of aromatic amines 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. Examples of strong acids suited for the reaction include sulfuric, phosphoric, hydrochloric, p-toluene sulfonic, and trifluoroacetic.
U.S. Pat. No. 3,496,213 (Ross, 1970) 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.
U.S. Pat. No. 4,153,567 (Kluger et al., 1979) 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,Nxe2x80x2-di-(2-cyanoethyl)-1,2-diaminocyclohexane. Examples of suitable acid catalysts for the reactions are reported to be p-toluene-sulfonic acid and acetic acid salts. It is also reported that, following cyanoethylation, the nitrile can be reduced to the amine by a catalytic hydrogenation using Raney nickel or other transition metals as catalysts.
U.S. Pat. No. 4,321,354 (Kluger et al., 1982) discloses the production of cycloaliphatic polyamines, particularly the polyamine derived from 1,2-diaminocyclohexane. As in ""567, 1,2-diaminocyclohexane is reacted with one or two moles acrylonitrile respectively in the presence of an acetic acid catalyst. The resultant cyanoethylated diaminocyclohexanes can be reduced with hydrogen to form the polyfunctional amines.
A method of cyanoethylation of substituted cycloaliphatic vicinal primary amines to produce a compound with three or four amine substitutions has not been shown.
This invention is directed to new compounds represented by the structural formula below and to the method of making the compounds.
R1 represents H, C1 to C4 alkyl, or substituted C1 to C4 alkyl; R2 represents H or a cyanoethyl; n is an integer of 1 to 6, and y is 1 or 2. In preferred compounds, n is 4, y is 1, R1 is methyl, and R2 is H or a cyanoethyl.
The compounds are produced by cyanoethylation of a cycloaliphatic vicinal diamine in the presence of water and a catalytic amount of an acid having a pKa of xe2x88x923 to 7.5, preferably acetic acid. The use of a catalytic amount of an acid and water results in:
production of heretofore unknown products in good yield;
production of little or no unwanted byproducts; and
ability to immediately hydrogenate the polynitriles to polyamines without separation and/or purification of the products.
In a preferred method of making the compounds of this invention, and for purposes of illustration, o-methylcyclohexyldiamines (H6OTD) can be reacted with acrylonitrile in the presence of a stoichiometric amount of water and a catalytic amount of acetic acid to produce three products of structures A, B, and C (shown below), with little or no unwanted byproducts. 
In the method of making the novel compounds of this invention, acrylonitrile is reacted with a cycloaliphatic vicinal diamine, in an amount of water equivalent to the diamine and a catalyic amount of an acid having a pKa of xe2x88x923 to 7.5, to produce a product of general structure I below:
R1 represents H, C1 to C4 alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, and t-butyl, or substituted C1 to C4 alkyl, wherein the substitution can be hydroxalkyl, carboxylic acid, amide, and amino; R2 represents H or a cyanoethyl; n is an integer of 1 to 6, and y is 1 or 2. In preferred compounds, n is 4, y is 1, R1 is methyl, and R2 is H or a cyanoethyl.
In the current method, one mole of acrylonitrile is reacted with one equivalent of of one or more cycloaliphatic vicinal diamines, in the presence of water and a catalytic amount of an acid having a pKa of xe2x88x923 to 7.5; preferably 1 to 6. The molar concentration of water per mole of cycloaliphatic diamine can range from 0.1 to 10:1, preferably from about 1:1 to 2:1.
Examples of cycloaliphatic vicinal diamines commonly used in the cyanoethylation process are 1,2-diaminocyclohexane; 1-methyl-2,3-diaminocyclohexane, 1-methyl-3,4-diaminocylcohexane, a mixture of 1-methyl-2,3-diaminocyclohexane and 1-methyl-3,4-diaminocylochexane, t-butyldiaminocylcohexane, ethyldiaminocylcohexane, and isopropyldiaminocyclohexane.
By catalytic amount of acid is meant an amount which will noticeably increase the rate of reaction. Typically the amount of catalyst ranges from 0.1 to 1.0 mole per mole of cycloaliphatic diamine. Acetic acid is the preferred acid.
The temperature for effecting the reaction between acrylonitrile and the cycloaliphatic vicinal amine generally ranges from about 25 to 150xc2x0 C., preferably 50 to 80xc2x0 C. Pressure for the reaction can range from atmospheric to 60 psig. Atmospheric pressure is preferred.
The combination of water and acid unexpectedly leads to a product containing substantial amounts of compounds having 3 and 4 cyanoethyl substitutions on the amine nitrogens and little or no byproducts.
The product of the cyanoethylation reaction can be used in a catalytic hydrogenation reaction without purifying or separating the product.
USPTO Backgrounds
USPTO Backgrounds