Catalytic aminomethylation of alkenes in a dimethylformamide medium

Article abstract of DOI:10.1134/S096554411203005X

The hydroaminomethylation of alkenes with dimethylamine catalyzed by rhodium and ruthenium complexes in a dimethylformamide medium under synthesis-gas pressures of 2 MPa has been studied. It has been shown that the combined use of these metals leads to a significant increase in the rate of formation of amines and selectivity for n-alkyldimethylamine. It has been found that the reaction can proceed with dimethylformamide used as an aminating agent without the addition of dimethylamine. Pleiades Publishing, Ltd., 2012.

Full text of DOI:10.1134/S096554411203005X

ISSN 0965ꢀ5441, Petroleum Chemistry, 2012, Vol. 52, No. 3, pp. 179–185. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © E.A. Karakhanov, E.A. Runova, Yu.S. Kardasheva, D.V. Losev, A.L. Maksimov, M.V. Terenina, 2012, published in Neftekhimiya, 2012, Vol. 52, No. 3, pp. 204–210.
Catalytic Aminomethylation of Alkenes
in a Dimethylformamide Medium
E. A. Karakhanov, E. A. Runova, Yu. S. Kardasheva, D. V. Losev, A. L. Maksimov, and M. V. Terenina
Faculty of Chemistry, Moscow State University, Moscow, Russia
eꢀmail: kar@petrol.chem.msu.ru
Received September 23, 2011
Abstract—The hydroaminomethylation of alkenes with dimethylamine catalyzed by rhodium and rutheꢀ
nium complexes in a dimethylformamide medium under synthesisꢀgas pressures of 2 MPa has been studied.
It has been shown that the combined use of these metals leads to a significant increase in the rate of formation
of amines and selectivity for nꢀalkyldimethylamine. It has been found that the reaction can proceed with dimꢀ
ethylformamide used as an aminating agent without the addition of dimethylamine.
DOI: 10.1134/S096554411203005X
Dimethylalkylamines with ten or more atoms in the current environmental protection requirements
the hydrocarbon chain are the main type of feedstock
for the synthesis of cationic and nonionic surfactants
necessitate a search for new methods of manufacturꢀ
ing these products from the basic petrochemical feedꢀ
stock, i.e., olefins. One of these methods is hydroamiꢀ
nomethylation.
based on
Nꢀoxides. Conventional manufacturing
routes for these amines involve either highꢀtemperaꢀ
ture transformations of alcohols and dimethylamine
on heterogeneous catalysts or the production of
monochlorinated derivatives via the radical hydroꢀ
chlorination of olefins [1]. In the latter case, the secꢀ
ond stage of the process includes the reaction with
dimethylamine, which gives hydrochloride, and the
isolation of dimethylalkylamine. The multistage
This process is a sequence of reactions that includes
the hydroformylation of an unsaturated compound
and the subsequent reductive amination of the resultꢀ
ing aldehydes. The general reaction scheme, which
covers the formation of both the main products
(amines) and byproducts, can be represented as folꢀ
nature of the processes and their noncompliance with lows:
hydrogenation product
NR2R3
H
O
HNR2R3
H2
R1
isomerized
product
CO/H2
R1
H2
H
CO/H2
HNR2R3
H2
R1
R1
NR2R3
R1
O
O
linear product
CO/H2
H
HNR2R3
R1
NR2R3
enamine
R1
R1
isomerization product
–H2O
H2
R1
R1
OH
alcohol
aldol condensation
product
General scheme of the hydroaminomethylation of alkenes.
179

180
KARAKHANOV et al.
Hydroaminomethylation is mediated by transition temperature program of 100–230°С and helium as a
metal complexes with phosphorusꢀcontaining ligands, carrier gas. The products were identified by mass specꢀ
mostly alkyl and aryl phosphines. Rhodiumꢀcontainꢀ trometry using a Finnigan MAT ITDS GC–MS
ing catalyst systems are most widely used; they make it instrument. The ionization energy was 70 eV; the
possible to implement hydroaminomethylation for source temperature was 220°С. The mixture compoꢀ
terminal alkenes with a short and long carbon chain, nents were separated on a 30ꢀm SEꢀ30 capillary colꢀ
aliphatic unsaturated compounds with different funcꢀ umn with an inner diameter of 0.25 mm using temperꢀ
tional groups in their structure, styrenes, diphenylethꢀ ature programming from 100 to 300
ylenes, and internal olefins [2–4]. The process was
°С.
conducted in various solvents (THF, toluene, methaꢀ
RESULTS AND DISCUSSION
nol) in order to increase the homogeneity of the sysꢀ
tem. The tandem hydroaminomethylation of higher
terminal alkenes with the participation of an aqueous
solution of dimethylamine under conditions of a twoꢀ
phase catalysis was also studied in [5–9]. It was shown
that the formation of amines can proceed at a high rate
and with a high selectivity.
Hydroaminomethylation Mediated
by RhodiumꢀContaining Catalyst Systems
The hydroaminomethylation was carried out using
a dimethylamine solution in DMF under synthesis gas
pressures of up to 4 MPa at a temperature of 80–
160°C with Rh(acac)(CO)2 as a rhodium source.
It should be noted that in all these cases, one of the
main limitations to the implementation of the reaction
was a low solubility of dimethylamine in nonpolar
media and, accordingly, a low efficiency of mass transꢀ
fer between the aqueous solution of dimethylamine
and alkene in twoꢀphase systems. The use of toluene or
methanol as solvents requires significant energy conꢀ
sumption for the isolation of reaction products.
In this study, we propose a modified hydroamiꢀ
nomethylation system that involves a dimethylamine
solution in dimethylformamide (DMF) as a reagent.
This solvent provides an easy mixing of reagents and is
the product of the carbon monoxide reaction with
dimethylamine. During the course of the hydroamiꢀ
nomethylation reaction, equilibrium between dimethꢀ
ylamine, DMF, and synthesis gas is established in the
system and, as such, can significantly increase the effiꢀ
ciency and adaptability of the proposed process.
Triphenylphosphine was used as a phosphorusꢀconꢀ
taining ligand. In the case of hydroaminomethylation
of noneneꢀ1 catalyzed by Rh(acac)(CO)2 with large
excess PPh3, the complete conversion of the substrate
is observed even at 80°С (Table 1). Aldehydes, isoꢀ
meric ꢀalkenes, and nitrogen compounds, i.e.,
n
enamines and tertiary amines with a branched and linꢀ
ear alkyl substituent, are formed during the reaction.
The amount of unreacted aldehydes in the amination
hardly depends on the syngas pressure at this temperꢀ
ature. The predominance of enamine in the nitrogenꢀ
containing products is apparently attributed to a low
rate of hydrogenation of the internal double bond in its
molecule under the experimental conditions.
A significant increase in the yield of amines is
observed at 130°С: the reaction products have almost
no aldehydes after 6 h of the process under 2.0 MPa.
The maximum yield of amines (73%) was recorded
when the pressure was increased to 4.0 MPa; in this
case, the selectivity for nꢀdecyldimethylamine was
EXPERIMENTAL
58%, and that for the products formed from
hyde was 61%.
nꢀaldeꢀ
(Acetylacetonato)dicarbonylrhodium(I) (Rh(acac)
(CO)2) synthesized as described in [10] was used as a
source of rhodium. Triruthenium dodecacarbonyl
Ru3(CO)12 was prepared according to [11]. Noneneꢀ1,
octeneꢀ1, deceneꢀ1, dodeceneꢀ1, and triphenyl phosꢀ
phite were distilled under vacuum in an argon stream.
DMF was dried over calcinated molecular sieves 3A
and then distilled in an argon stream.
A further increase in temperature leads to an
increase in the olefinꢀtoꢀamine conversion rate; at
170°С, the yield is 53% for nꢀdecyldimethylamine and
20% for isoamines within 3 h (Fig. 1). In addition,
enamines are almost absent from the mixture as well as
aldehydes. The amount of the product nonane signifiꢀ
cantly increases at 150–170°С.
The hydroaminomethylation reaction was run in a
Parr Instrument autoclave (volume of 0.1 L) equipped
with a turbine stirrer (1500 rpm), a pressure sensor,
and temperature control devices under a synthesis gas
pressure of 0.6 to 4 MPa (H2/CO = 1) at a temperature
A study of the dependence of the yields of
hydroaminomethylation products on the reaction
time at 150°С and a pressure of 2.0 MPa showed that
under these conditions, the main amount of amines is
formed within 1 h and an increase in the experiment
time has almost no effect on the ratio of enamines and
amines (Table 2). Apparently, the hydrogenation of
of 80–170°С. The reaction was conducted under conꢀ
stant stirring for a predetermined time (0.5 to 6 h).
Gas–liquid chromatographic analysis was perꢀ enamines can be considered the rateꢀdetermining step
formed using the internal standard method with a of the process. An increase in the hydrogen concentraꢀ
Hewlett Packard chromatograph with a FID and a 30ꢀm tion up to a ratio of H2 : CO = 2 makes it possible to
capillary column coated with the SEꢀ30 phase with a significantly increase the reaction rate; in this case, the
PETROLEUM CHEMISTRY Vol. 52
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2012

CATALYTIC AMINOMETHYLATION OF ALKENES
181
Table 1. Hydroaminomethylation of noneneꢀ1 in the presence of a Rh catalyst system (H2/CO = 1, [Rh] = 2.8 mmol/L,
substrate/catalyst = 160, [PPh3]/[Rh] = 214)
Yield, wt %
Pressure,
MPa
Converꢀ
sion, %
Time, h
aldehydes
1
enamines
2
amines
3
olefins
80°C
0.6
2
99
98
98
57
57
51
47
41
33
22
27
32
22
27
32
2
5
5
2
19
11
12
3
3
5
5
4
130°C
0.6
2
97
12
8
15
12
27
27
54
1
3
6
98
99
99
24
16
1
13
9
11
22
19
10
16
–
48
51
69
44
45
51
17
11
11
–
4
3
99
7
4
12
2
73
58
8
Note: (1) nꢀdecanal; (2) deceneꢀ1ꢀylꢀdimethylamine; and (3) nꢀdecyldimethylamine.
yield of amines is 80%, and the selectivity for tions, the solution mostly contains rhodium comꢀ
decyldimethylamine remains the same (81%).
plexes with dimethylamine, which do not exhibit
activity in hydroformylation. An increase in the phosꢀ
phorus ligand concentration leads to a shift in the
equilibrium in the solution in the direction of phosꢀ
phineꢀcontaining complexes which are active species.
It should be noted that all these results were
obtained under conditions of excess triphenylphosꢀ
phine. In the absence of a phosphorusꢀcontaining
ligand at 80°С, the reaction does not occur; at 150°С,
the conversion is 35% and the main products are
isononenes (16%) and nonane (17%).
The hydroaminomethylation of noneneꢀ1 also
occurs in the presence of a rhodium catalyst system
with tri(
оꢀtolyl)phosphine, tricyclohexylphosphine,
An increase in the P/Rh ratio leads to an increase and triphenyl phosphite (Fig. 2). In the case of excess
in the substrate conversion and to a change in the triphenylphosphine, an almost complete conversion
chemoselectivity of the process: the yield of amines of the substrate was observed; however, large amounts
increases. This is most clearly evident at 150°С (Table 3). of the byproducts isononenes (27%) and nonane
Apparently, at low triphenylphosphine concentraꢀ (16%) are formed along with amines (39%). The cataꢀ
60
Isoaldehydes
50
Deceneꢀ1ꢀylꢀ
dimethylamine
40
30
20
10
0
Isoenamines
Isoamines
Decanal
Decyldimethylamine
70
120
170
Temperature, °C
Fig. 1. Hydroaminomethylation of noneneꢀ1 at different temperatures ([Rh] = 2.8 mmol/L; [PPh ]/[Rh] = 214.2 MPa;
3
H /CO = 1.3 h).
2
PETROLEUM CHEMISTRY Vol. 52
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2012

182
KARAKHANOV et al.
Table 2. Effect of reaction time on the composition of noneneꢀ1 hydroaminomethylation products (H2/CO = 1.2 MPa;
150 C; [Rh] = 2.8 mmol/L; substrate/catalyst = 160; [PPh3]/[Rh] = 214)
°
Reaction mixture composition, wt %
Converꢀ
sion, %
Time, h
aldehydes
1
enamines
2
amines
3
isononenes nonane
0.5
1
73
93
95
95
99
99
21
5
15
2
17
17
15
14
17
4
17
5
17
53
55
57
58
80
16
40
42
46
47
65
7
7
8
8
8
7
11
11
11
11
14
8
2
6
2
6
3
5
2
3
6
2
2
3
3*
–
–
–
Note: (1) nꢀdecanal; (2) deceneꢀ1ꢀylꢀdimethylamine; and (3) nꢀdecyldimethylamine.
Table 3. Hydroaminomethylation of noneneꢀ1 at different [PPh3]/[Rh] ratios (H2/CO = 1.2 MPa; 3 h; [Rh] = 2.8 mmol/L;
substrate/catalyst = 160)
Reaction mixture composition, wt %
Converꢀ
No.
P/Rh
sion, %
aldehydes
1
enamines
2
amines
3
isononenes nonane
80
°
C
1
2
3
0
20
1
3
–
–
–
–
–
1
–
1
–
1
–
1
–
–
7
1
1
2
214
98
57
41
27
150
27
5
5
°
C
4
5
6
7
0
35
51
71
95
–
–
–
5
–
–
–
–
3
–
–
–
3
2
34
58
57
2
16
5
17
9
5
20
25
2
43
46
4
7
214
2
14
8
11
Note: (1)
nꢀdecanal; (2) deceneꢀ1ꢀylꢀdimethylamine; and (3) nꢀdecyldimethylamine.
lyst system with triphenyl phosphite exhibited a low (Table 4) show that at 80°С, the introduction of a
activity; this can be attributed to a partial hydrolysis of
the ligand under the reaction conditions.
ruthenium compound into the catalyst system has litꢀ
tle effect on the results of hydroaminomethylation;
only the yield of enamines increases from 27 to 38%
within a reaction time of 3 h (Table 4, rows 1, 6). At the
same time, both the total yield of amines and the
selectivity for the normal product significantly
Hydroaminomethylation Mediated by Mixed
Rhodium–Ruthenium Catalyst Systems
An alternative to an increase in the hydrogen presꢀ
sure relative to carbon monoxide for increasing the
hydrogenation rate of enamines can be doping the sysꢀ
tem with metal complexes that are more active in
hydrogenation in the presence of amines than rhodꢀ
ium compounds. Published data [12–14] show that
one of the most promising components of a catalyst
system can be ruthenium; its compounds with donor
nitrogenꢀcontaining ligands are known catalysts for
the hydrogenation of functional compounds. We
increase at 150
amines with the selectivity for
of 80–86% is observed even for 1 h (Table 4, rows 9–
14). Experiments with additional hydrogen supply
(Table 4, rows 10, 11) showed that the maximum
°
С
. The predominant formation of
nꢀdecyldimethylamine
selectivity for nꢀamine (86%) in this case was observed
under a pressure of 2.0 MPa, and the yield of amine
increased to 92% under 4.0 MPa (selectivity of 80%).
The admixture of water to the reaction system led to a
selected Ru3(CO)12 as a source of ruthenium. Our data decrease in the yield of amines, whereas the selectivity
PETROLEUM CHEMISTRY Vol. 52
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2012

CATALYTIC AMINOMETHYLATION OF ALKENES
183
100
90
Nonane
80
Isononenes
Amines
70
60
50
40
30
20
10
0
Enamines
Aldehydes
Selectivity for
P (oꢀtol)3 PPh3
PCy3 P (OPh)3
n
ꢀamine
Ligands
Fig. 2. Hydroaminomethylation of noneneꢀ1 in the presence of different ligands ([Rh] = 2.8 mmol/L; [PPh ]/[Rh] = 214.2 MPa;
3
H /CO = 1.3 h).
2
did not decrease (Table 4, rows 12, 9). Thus, ruthenium conclusion that the rateꢀlimiting step for the overall
additives in this system give the possibility to signifiꢀ
cantly increase the rate of formation of amine.
hydroaminomethylation reaction under these condiꢀ
tions is the hydrogenation of enamines. Thus, an optiꢀ
mum combination of activity and selectivity is
An increase in the total reaction rate and the prevꢀ
alence of amines in the reaction products confirm the achieved using the Rh(acac)(CO)2 + Ru3(CO)12
+
Table 4. Hydroaminomethylation of noneneꢀ1 in the presence of the Ru/Rh catalyst system (H2/CO = 1.2 MPa; [Rh] =
2.8 mmol/L; substrate/catalyst = 160; [PPh3]/[Rh] = 214)
Reaction mixture composition, wt %
Converꢀ
No.
Ru/Rh Time, h
sion, %
aldehydes
1
enamines
2
amines
3
isononenes nonane
80°C
1
2
3
4
5
6
7
3
98
99
89
97
99
91
97
57
39
46
45
24
41
40
41
19
18
25
15
29
21
27
35
32
20
33
38
29
27
34
32
20
33
38
29
5
21
5
5
7
1
3
3
2
2
2
2
2
3
4
3
3
3
0
6
16
3
3
6
6
6a
25
37
7
23
34
7
3
12
6
23
21
150°C
8
9
0
1
1
1
1
1
1
1
93
99
99
99
99
99
99
5
–
–
–
2
2
17
2
5
–
–
–
–
–
–
53
83
84
92
78
83
83
40
69
72
74
65
67
67
7
6
5
2
7
6
5
11
8
3
–
10
11
12
13
14
3a
3a,b
3c
6
–
–
2
8
2
3
2
3
9
–
–
–
–
2
8
12
3
8
170°C
15
3
1
93
0
2
0
73
59
8
10
a
b
c
H /CO = 2; 4 MPa; Experiment with the addition of water (H O/HNMe = 2).
2
2
2
Note: (1)
nꢀdecanal; (2) deceneꢀ1ꢀylꢀdimethylamine; and (
3) nꢀdecyldimethylamine.
PETROLEUM CHEMISTRY Vol. 52
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184
KARAKHANOV et al.
experiments on the decomposition of DMF in a synꢀ
thesis gas medium in the presence of Rh(acac)(CO)2
and Rh(acac)(CO)2 + PPh3 at a temperature of 150°С:
Table 5. Hydroaminomethylation of linear alkenes (H2/CO =
1.2 MPa; 150 C; 1 h; [Rh] = 2.8 mmol/L; substrate/cataꢀ
lyst = 160; [PPh3]/[Rh] = 214)
°
the dimethylamine concentration was 12% within 3 h.
Alkene Conversion, % Yield of amines, % S*, %
In the case of reaction conducted under 0.6 MPa at
Octeneꢀ1
98
82
83
80
91
87
83
85
84
80
°
С, the formation of amination products, i.e.,
Noneneꢀ1
Deceneꢀ1
99
deceneꢀ1ꢀylꢀdimethylamine and amines (
nꢀdecyldiꢀ
99
99
methylꢀ and isoamines), was observed (Table 6, rows 1–
3). An increase in temperature leads to an increase in
their yield: at 130°С, their yields were as high as 16 and
Dodeceneꢀ1
* Selectivity for
n
ꢀalkylamines.
30%, respectively, within 6 h (4 MPa) (Table 6, row 7).
In the case of the Ru–Rh catalyst system, we managed
to increase the yield of amines to 43% (of which
PPh3 bimetallic system in the process at 150
H2/CO = 2), Ru/Rh = 3, and P/Rh = 214.
High yields of amines with a linear alkyl substituent
were also recorded under these conditions for some
С8–С12 terminal alkenes (Table 5), with the length of
the hydrocarbon chain having no effect on the reacꢀ
tion rate.
°
С, 2 MPa
nꢀdecyldimethylamine made 38%) (Table 6, rows 8, 9).
(
Thus, it can be concluded that the combined use of
a bimetallic rhodium–ruthenium catalyst system leads
to a significant increase in both the rate of formation
of amines and selectivity for nꢀalkyldimethylamine. It
has been found that the reaction can proceed with
DMF as an aminating agent without the addition of
dimethylamine.
Hydroaminomethylation with DMF as Aminating Agent
Taking into account that DMF can be decomposed
into dimethylamine and carbon monoxide in the presꢀ
ence of platinum group metal complexes according to
published [15–17], we studied the reaction of noneneꢀ
ACKNOWLEDGEMENTS
This work was performed under the 2009–2013
1 with synthesis gas in a DMF medium without the Federal Target Program “ScientificꢀResearch and
addition of dimethylamine. Table 6 shows the results Academic Personnel for Innovative Russia (item 1.2.2
obtained using the Rh(acac)(CO)2 + PPh3 catalyst sysꢀ of the Program: Macromolecular Chemistry. Petroꢀ
tem. The formation of free amine was confirmed in leum Chemistry. Catalysis).
Table 6. Reaction of noneneꢀ1 with synthesis gas in a DMF medium (H2/CO = 1; 150°C; 3 h; [Rh] = 2.8 mmol/L; subꢀ
strate/catalyst = 160; [PPh3]/[Rh] = 214)
Yield, wt %
Pressure, Conversion,
No.
MPa
%
aldehydes
1
enamines
2
amines
3
80°C
1
2
3
0.6
2
99
84
89
86
64
65
60
3
1
3
3
1
3
6
7
7
6
7
7
99
99
4
130
°
C
C
4
5
6
7
0.6
2
95
99
98
96a
21
57
61
35
13
39
35
13
11
10
12
16
11
10
12
16
20
17
16
30
19
16
14
24
4
150°
8
9
4
98a
99b
34
20
6
7
7
6
9
35
43
29
38
16
a
b
6 h; 6 h, [Ru]/[Rh] = 6.
Note: ( ꢀdecanal; ( ) deceneꢀ1ꢀylꢀdimethylamine; and (
1)
n
2
3)
nꢀdecyldimethylamine.
PETROLEUM CHEMISTRY Vol. 52
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2012

CATALYTIC AMINOMETHYLATION OF ALKENES
185
10. Yu. S. Varshavskii and T. G. Cherkasova, Zh. Neorg.
Khim. , 1701 (1967).
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