Production of primary and secondary amines by reaction of ammonia with conjugated diene in the presence of Pd/phosphine catalyst and primary or secondary aliphatic alcohol solvent medium

Short chain, unsaturated primary and secondary amines are prepared by reaction of ammonia and conjugated dienes in a primary or secondary aliphatic alcohol solvent medium and in the presence of a catalyst system comprising a palladium compound co-catalyzed with a phosphine ligand containing 2 to 4 phosphorus atoms.

BACKGROUND OF THE INVENTION 
This invention relates to the palladium-catalyzed amination of conjugated 
dienes with ammonia to produce relatively short chain unsaturated primary 
and secondary amines. 
Organic amines find a wide range of commercial usage such as paper and 
rubber chemicals, plasticizer intermediates, herbicide intermediates, 
surfactants, water treatment chemicals and extractants. Because prior 
methods of preparation are multi-step and sometimes non-selective, amines 
are a relatively expensive class of chemicals. 
The direct addition of ammonia or amines to olefins is a potentially lower 
cost method of preparing amines. However, such direct addition has been 
hindered by the high reaction temperatures necessary to meet the 
activation energy requirements of the reaction and the unfavorable 
equilibrium thermodynamics for the reactions at these temperatures. One 
method of overcoming these obstacles is to find a catalyst to lower the 
energy of activation required and thus allow the reaction to proceed at 
temperatures where the equilibrium is more favorable. 
Direct amination of olefins with amines using soluble palladium catalysts 
has been reported heretofore by several investigators, for example, 
Takahashi, Bull. Chem. Soc. Japan 41, 454-60 (1968) and in U.S. Pat. Nos. 
3,350,451; 3,444,202; 3,530,187; and British Patent No. 1,178,812. 
However, the disclosed reactions do not involve ammonia itself and thus do 
not have the potential for producing primary amines as distinguished from 
secondary and tertiary amines. 
Tsuji and co-workers reported the use of a palladium catalyst system which 
gives amination of butadiene with ammonia, Chem. Comm. (Japan), 345 
(1971). The reaction is described as taking place in acetonitrile solvent 
and in the presence of palladium acetate and triphenyl phosphine. However, 
in the hands of the present inventors, the Tsuji reaction gave only low 
yields at slow rates. 
Recently, in application Ser. No. 697,900, filed June 21, 1976, the present 
inventors disclosed an improved homogeneous palladium-based catalyst 
system which facilitates the amination of butadiene with either ammonia or 
amines with excellent yields and rates under mild conditions. These 
catalysts, however, give long chain secondary and tertiary octadienyl 
amines as a result of multiple alkylation of ammonia and telomerization of 
butadiene. The relatively shorter chain butenylamines desired herein were 
not produced by the catalyst system. 
Preparation of the shorter chain butenylamines by reaction of primary and 
secondary amines with butadiene using a preformed palladium-diphosphine 
complex catalyst has been described by Takahashi et al., Bull. Chem. Soc. 
Japan 45, 1183-91 (1972). However, the reactivity of the amine reactants 
is reported to be associated with the amine basicity, with the more 
strongly basic amines being more active. No disclosure of the more weakly 
basic ammonia is provided by Takahashi. Moreover, the Takahashi reaction 
requires use of a co-catalytic amount of phenol to provide a suitable 
reaction rate. 
BRIEF SUMMARY OF THE INVENTION 
In accordance with the present invention, short chain primary and secondary 
unsaturated amines are produced by reaction of ammonia and conjugated 
dienes in a primary or secondary aliphatic alcohol solvent medium and in 
the presence of a catalyst comprising a palladium compound co-catalyzed 
with a phosphine ligand containing from 2 to 4 phosphorus atoms. 
DETAILED DESCRIPTION OF THE INVENTION 
The novel palladium-based catalyst system of this invention comprises a 
palladium compound co-catalyzed with a phosphine ligand containing from 2 
to 4 phosphorus atoms such as a bidentate or tridentate ligand. 
The preferred palladium compounds are salts with readily displaceable 
anions such as, for example, acetate, nitrate, cyanide and 
acetylacetonate. The most preferred of these is palladium acetate. It will 
be appreciated that mixtures of these and other such palladium compounds 
also can be used. Salts with strongly bound anions such as Cl.sup.- or 
Br.sup.- are substantially less effective in the catalyst system of this 
invention. 
The preferred ligands employed in this invention are alkyl-, aryl-, and 
arylalkyl phosphines containing from two to four phosphorus atoms. Aralkyl 
compounds, especially arylalkyl phosphines containing alkyl or alkenyl 
chains of from two to four carbons separating the phosphorus atoms are 
most preferred. Specific examples of these compounds are: 
1,2-bis(diphenylphosphino)ethane, 
1,3-bis(diphenylphosphino)propane, 
1,4-bis(diphenylphosphino)butane, 
1,2-bis(diphenylphosphino)ethylene, 
2,3-O-isopropylidene-2,3-dihydroxy-1,4-bis(diphenylphosphino)butane, 
1,2-bis(O-anisylphenylphosphino)ethylene, 
2,3-bis(diphenylphosphino)-2,3-dimethylbutane, 
1,1,1-tris(diphenylphosphinomethyl)ethane, and 
bis(2-diphenylphosphinoethyl)phenylphosphine. 
The amount of ligand used can vary somewhat but best results are obtained 
with a phosphorus/palladium mole ratio of about 2 to 4. The preferred 
ratio is about 2.9. In various examples of the invention, increasing the 
ligand/palladium ratio gave slightly faster reaction rates with the 
tridentate ligand in contrast to the slower rates observed with higher 
ligand/palladium ratios using the bidentate 
1,2-bis(diphenylphosphino)ethane. Arsine ligands are substantially less 
effective than the foregoing phosphino ligands. 
Examples of conjugated dienes which can be appropriately aminated with 
ammonia by the aforesaid catalyst system of this invention are compounds 
having from four to about eight carbon atoms and containing conjugated 
double bonds, for example, 1-3-butadiene, isoprene, 1,3-pentadiene, 
2,4-hexadiene, 2,3-dimethylbutadiene and the like compounds. Amination of 
1,3-butadiene is preferred. 
The mole ratio of ammonia to conjugated diene used in the palladium 
catalyzed reaction of this invention can vary widely, for example, from 
about 1:3 to about 24:1. The preferred range is from about 3:1 to about 
12:1. 
It has been found that the use of a primary or secondary aliphatic alcohol 
solvent medium for the disclosed catalyst system is important for 
obtaining high yields of product. The preferred aliphatic alcohols have 
from 1 to 10 carbon atoms. Illustrative of such solvents are methanol, 
ethanol, propanol, isopropanol, butanol, hexanol, cyclohexanol, octanol 
and decanol. 
Although the inventors are not to be bound by theory, it is believed that 
the primary or secondary aliphatic alcohol solvent must be present in an 
amount sufficient to reduce the palladium from the divalent to the 
zerovalent state as shown in the following illustrative reaction: 
##STR1## 
By way of comparison, the heretofore disclosed phenol does not provide the 
necessary aliphatic hydrogens for such reaction. 
Reaction temperatures can vary from about 50.degree. C. to about 
200.degree. C., but the preferred range is from about 100.degree. C. to 
about 145.degree. C. 
Addition of trifluoroacetic acid to the reaction mixture, while not 
necessary to the invention, increases the rate of reaction. It thereby 
enables the carrying out of the reaction at lower temperatures with better 
reaction rates than those obtained when no acid is used. For example, 
addition of about 0.005 mole of ammonium trifluoracetate to about one-half 
mole of reactants (six parts butadiene to one part ammonia) allowed the 
palladium-catalyzed reaction to be run at 100.degree. C. vs. the 
145.degree. C. preferred when run without the ammonium trifluoroacetate. 
The primary amines obtained by the novel process of this invention can be 
represented by the general structure 
##STR2## 
wherein R.sup.1 and R.sup.2 can be hydrogen or alkyl radicals of from one 
to four carbon atoms, such as methyl, ethyl, propyl, isopropyl and butyl. 
The secondary amines can be represented by the general structure 
##STR3## 
wherein R.sup.1 and R.sup.2 are as stated above. 
The chain length in these primary and secondary amines is the same as the 
chain length in the reactant conjugated diene. 
The products of the palladium catalyzed reaction using, for example, 
1,3-butadiene as the diene are predominately primary butenylamines, with 
lesser amounts of secondary butenylamines, although the reaction can 
easily be modified to produce predominately the latter. The primary 
butenylamines consist of 2- butenylamine and .alpha.-methallylamine having 
the structures: 
##STR4## 
The amine products of the reactions of the invention are useful as acid 
scavengers, rubber and paper chemicals and, in their cationic form, as 
fungicides. They can also be copolymerized with acrylonitrile to give 
polymers having improved dye retention. These products also can be 
polymerized with other monomers through the amine function with the 
pendant ethylenic function and then reacted to produce a cross-linked 
polymer. The unsaturated ethylenic linkages in these products can be 
hydroxylated or hydrated to form useful alcohol derivatives from which 
esters or ethers are prepared. The ethylenic linkage can serve as a 
dienophile in Diels-Alder condensations and as an active site in 
polymerization processes. Hydrogenation of the ethylenic linkage also can 
occur to give saturated amines.

The following detailed examples with further illustrate the invention 
although it will be appreciated that the invention is not limited to these 
specific examples. 
EXAMPLE 1 
A reaction illustrating the invention was run in a 45-ml, stainless steel 
autoclave equipped with a stirrer and a pressure gauge. In the reaction, 
1.67 grams (7.4 millimoles) of palladium acetate, 4.13 g of 
1,2-bis(diphenylphosphino)ethane (DIPHOS) and 33 ml of ethanol were 
charged into the autoclave under a nitrogen atmosphere. A partial vacuum 
was applied to the autoclave which was cooled in a Dry Ice bath. Ammonia 
(54.4 g, 3.2 moles) and then 1,3-butadiene (28.7 g, 0.53 mole) were 
condensed into the autoclave from calibrated reservoirs. The reaction 
mixture was heated to 145.degree. C. and stirred for one hour during which 
time the autogenous pressure dropped from approximately 1100 psig to 1000 
psig. The liquid product was filtered from the solid catalyst residue 
(about one gram) and then distilled at reduced pressure through a 
short-path head to separate it from any dissolved catalyst. This 
distillate was then fractionally distilled to separate the various 
products. Identification of products was made on the basis of VPC, proton 
nuclear magnetic resonance, VPC/mass spectroscopy and elemental analysis. 
VPC of the reaction product showed that 90% of the butadiene had been 
converted to a mixture of monobutenyl amines (49%), dibutenyl amines 
(27%), tributenyl amines (8%), a trace of C.sub.16 amine, and butadiene 
dimers (16%). The monobutenyl amines consisted of .alpha.-methallylamine 
(62%), trans-2-butenylamine (30%), and cis-2-butenylamine (8%). The 
dibutenylamines consisted of N-2-butenyl-.alpha.-methallylamine (about 
50%), bis(2-butenyl)amine (50%), and a trace of 
bis(.alpha.-methallyl)amine. Boiling points and elemental analysis are 
shown in the following Table I: 
TABLE I 
__________________________________________________________________________ 
Product Boiling Points and Elemental Analysis Data 
__________________________________________________________________________ 
Boiling Point 
Elemental Analysis, Cald'd (Found) 
Compound .degree. C, mm Hg 
C H N 
__________________________________________________________________________ 
##STR5## 61-62(750) 
67.55(67.55) 
12.75(12.75) 
19.67(19.70) 
##STR6## 81-82(750) 
67.55(67.55) 
12.78(12.75) 
19.66(19.70) 
##STR7## 84-85(750) 
67.35(67.55) 
12.81(12.75) 
19.73(19.70) 
##STR8## 142-144(750) 
76.66(76.74) 
12.07(12.07) 
11.16(11.19) 
##STR9## 74(27) 76.73(76.74) 
12.05(12.07) 
11.07(11.19) 
__________________________________________________________________________ 
*isomer ratio determined by VPC. 
In the following Examples 2 through 10, essentially the same procedure, 
conditions and reactants as in Example 1 were employed except that various 
other bidentate or tridentate ligands were substituted for the DIPHOS in 
the catalyst system in Example 1. The percent butadiene converted to the 
various amine products is set forth in the following Table II: 
TABLE II 
__________________________________________________________________________ 
Effect of Liqand Structure 
C.sub.4 H.sub.6 + NH.sub.3 + Pd(OAc).sub.2 + Ligand + 
EtOH; 1 hr, 145.degree. C 
% C.sub.4 H.sub.6 Converted to: 
Charged Total 
Ammonia 
.alpha.-meth- 
2- Mono- 
Di- Monobutenyl 
Ex. Butadiene 
allyl- 
butenyl- 
butenyl 
butenyl 
C.sub.12 
Total 
Amines Butadiene 
No. 
Ligand mole ratio 
amine 
amine 
Amines 
Amines 
Amines 
Amines 
Total 
Oligomers 
__________________________________________________________________________ 
Bidentate Ligands: 
2 .phi..sub.2 PCH.sub.2 P.phi..sub.2 
6 9 4 12 13 4 48.sup.a 
.25 34 
3 .phi..sub.2 P(CH.sub.2).sub.2 P.phi..sub.2 (DIPHOS) 
6 27 17 44 24 7 76 .58 9 
4 .phi..sub.2 P(CH.sub.2).sub.3 .phi..sub.2 
6 25 26 51 34 5 90 .57 6 
5 .phi..sub.2 P(CH.sub.2).sub.4 P.phi..sub.2 
6 27 11 38 18 11 69 .55 23 
6 cis-.phi..sub.2 PCHCHP.phi..sub.2 
6 40 8 48 15 1 68 .71 5 
7 .phi..sub.2 PCCP.phi..sub.2.sup.b 
6 7 0 7 4 0 12 .58 15 
##STR10## 6 29 9 38 19 8 69 .55 22 
Tridentate Ligands: 
9 CH.sub.3 C(CH.sub.2 P.phi..sub.2).sub.3.sup.b 
6 39 14 54 26 2 82 .66 11 
10 .phi..sub.2 P(CH.sub.2).sub.2 P.phi.(CH.sub.2).sub.2 P.phi..sub.2 
1 5 0 5 4 14 43.sup.a 
.12 14 
(TRIPHOS) 
.phi..sub.2 P(CH.sub.2).sub.2 P.phi..sub.2 (DIPHOS) 
1 10 6 16 22 15 58 .39 13 
(for comparison) 
__________________________________________________________________________ 
.sup.a Includes significant conversion to C.sub.16 and C.sub.20 amines. 
.sup.b Gave almost completely homogenous products. 
EXAMPLE 11 
Example 1 was essentially repeated except that butanol was substituted for 
ethanol with substantially similar total conversion and product 
distribution. 
EXAMPLE 12 
Butadiene (0.48 mole), ammonia (0.08 mole), palladium acetate (1.1 mmol), 
DIPHOS (1.6 mmol), 0.005 mmol ammonium trifluoroacetate and 5 ml of 
ethanol were reacted for 1 hour at 100.degree. C. in a manner similar to 
that of Example 1. The conversion to amines was 36% (based on butadiene). 
In order to further demonstrate the unique properties of the present 
catalyst system for the production of monobutenylamines by reaction of 
ammonia with butadiene, a series of comparative tests were run in which 
prior art palladium bidentate-phosphine catalyst systems were substituted 
for the present catalyst system. Thus, the combination of the preformed 
palladium-diphosphine complex, PdBr.sub.2 (Ph.sub.2 PCH.sub.2 CH.sub.2 
PPh.sub.2).sub.2, where Ph.dbd.phenyl, with sodium phenoxide and phenol 
has been disclosed heretofore as an effective catalyst system for the 
reaction of amines with butadiene. In test A, below, this palladium-based 
catalyst system containing the bromide anion and a phenolic co-catalyst 
was found ineffective for the production of monobutenylamines by reaction 
of ammonia with butadiene. 
Use of palladium acetate and a bidentate-phosphine ligand, Ph.sub.2 
PCH.sub.2 CH.sub.2 PPh.sub.2, also has been described heretofore as 
effective for the reaction of active hydrogen compounds with butadiene. In 
tests B, C and D, below, this catalyst by itself was found to be 
relatively ineffective for the production of monobutenylamines by reaction 
of ammonia and butadiene. 
Use of phenol has been reported heretofore to enhance the catalytic 
activity of the reaction of amines and butadiene using palladium acetate 
and Ph.sub.2 PCH.sub.2 CH.sub.2 PPh.sub.2 ligand. However, when ammonia 
was reacted with butadiene using the catalytic system of the present 
invention as shown in tests E and F below, no enhancement in the 
production of the desired monobutenylamines was obtained by the added 
presence of phenol. 
Test A 
When ammonia (0.1 mole), 1,3-butadiene (0.15 mole), 
bis[1,2-bis(diphenylphosphino)ethane] palladium dibromide (0.25 mmole), 
sodium phenate (2.5 mmoles) and phenol (2.5 mmoles) were heated for 1 hour 
at 145.degree. C., less than 5% of the ammonia was converted to 
monobutenylamines, while at least 37% of the butadiene was converted to 
butadiene dimers. Approximately 2% of the ammonia was converted to C.sub.8 
to C.sub.16 amines. 
Test B 
When ammonia (0.48 mole), 1,3-butadiene (0.08 mole), palladium acetate (1.1 
mmole), and 1,2-bis(diphenylphosphino)ethane (2.78 mmoles) were heated 
above 135.degree. C., the pressure generated could not be contained, the 
temperature being higher than the critical temperature of ammonia. When 
the above reactants were heated for 1 hour at 128.degree. C., no 
monobutenylamines were detected in the product. 2.6% of the butadiene had 
been converted to dibutenylamines while 0.1% had been converted to 
C.sub.12 H.sub.21 N amines. 
Test C 
When ammonia (0.1 mole), 1,3-butadiene (0.15 mole), palladium acetate (1.1 
mmole), and 1,2-bis(diphenylphosphino)ethane (2.78 mmoles) were heated for 
one hour at 145.degree. C., no monobutenylamines and only traces of 
dibutenylamines were found. 0.8% of the ammonia was converted to C.sub.12 
H.sub.21 N-amines. 4.3% of the butadiene was converted to butadiene 
dimers. 
Test D 
When ammonia (0.1 mole), 1,3-butadiene (0.15 mole), palladium acetate (1.1 
mmole) and 1,2-bis(diphenylphosphino)ethane (0.28 mmole) were heated for 
one hour at 145.degree. C., no monobutenylamines were detected. Only 
traces of C.sub.8 to C.sub.12 amines were seen while 58% of the butadiene 
was converted into a mixture of butadiene oligomers. 
Test E 
0.25 gram (1.1 millimole) of palladium acetate, 0.62 gram (1.6 millimole) 
of 1,2-bis(diphenylphosphine)ethane, 8.16 grams (0.48 mole) of ammonia and 
4.3 grams (0.08 mole) of 1,3-butadiene were stirred in 5 ml. of ethanol 
for one hour at 1.45.degree. C. VPC of the reaction product showed that 
27% of the butadiene had been converted to .alpha.-methallylamine, 17% to 
2-butenylamine, 24% to dibutenylamines, 7% to tributenylamines and 17% to 
butadiene oligomers. 
When the above reaction was carried out in the added presence of 0.1 gram 
(1.1 millimole) of phenol, VPC of the reaction product showed that 28% of 
the butadiene had been converted to .alpha.-methallylamine, 16% to 
2-butenylamine, 18% to dibutenylamines, 4% to tributenylamines and 9% to 
butadiene oligomers. 
When the same reaction was carried out in the added presence of 0.4 gram 
(4.4 millimoles) of phenol, VPC of the reaction product showed that 27% of 
the 1,3-butadiene had been converted to .alpha.-methallylamine, 19% to 
2-butenylamine, 19% to dibutenylamines, 2% to tributenylamines and 9% to 
butadiene oligomers. 
Test F 
0.25 gram (1.1 millimole) of palladium acetate, 0.62 gram (1.6 millimole) 
of 1,2-bis(diphenylphosphino)ethane, 1.12 gram (0.08 mole) of ammonia, and 
13.0 grams (0.24 mole) of 1,3-butadiene were stirred in 5 ml of ethanol 
for 15 minutes at 145.degree. C. VPC of the reaction product showed that 
28% of the ammonia had been converted to .alpha.-methyallylamine, 14% to 
dibutenylamines, 21% to tributenylamines, 12% to C.sub.12 amines and 3% to 
C.sub.20 amines. 
When the above reaction was carried out in the presence of 0.1 gram (1.1 
millimole) of phenol, VPC of the reaction product showed that 20% of the 
ammonia had been converted to .alpha.-methallylamine, 18% to 
dibutenylamines, 29% to tributenylamines, 16% to C.sub.16 amines and 4% to 
C.sub.20 amines. 
Various other examples will be apparent to the person skilled in the art 
after reading the present diclosure without departing from the spirit and 
scope of the invention. All such other examples are included within the 
scope of the appended claims.