Steric effects in the catalytic amination of γ-, δ-, and ε-glycols

Article abstract of DOI:10.1134/S1070428016120071

The amination of butane-1,4-diol, isomeric dipropylene glycols, and cyclohexane-1,4-diyldimethanol in the presence of nickel/copper/chromium catalysts has been studied. The effect of the initial glycol structure on the reaction selectivity has been estima

Full text of DOI:10.1134/S1070428016120071

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2016, Vol. 52, No. 12, pp. 1756–1761. © Pleiades Publishing, Ltd., 2016.
Original Russian Text © A.F. Timofeev, A.G. Bazanov, N.G. Zubritskaya, 2016, published in Zhurnal Organicheskoi Khimii, 2016, Vol. 52, No. 12,
pp. 1765–1770.
Steric Effects in the Catalytic Amination
of γ-, δ-, and ε-Glycols
A. F. Timofeev, A. G. Bazanov,* and N. G. Zubritskaya
“Applied Chemistry” Russian Research Center, ul. Krylenko 26A, St. Petersburg, 193232 Russia
*
e-mail: agbazanov@mail.ru
Received May 5, 2016
Abstract—The amination of butane-1,4-diol, isomeric dipropylene glycols, and cyclohexane-1,4-diyldi-
methanol in the presence of nickel/copper/chromium catalysts has been studied. The effect of the initial glycol
structure on the reaction selectivity has been estimated.
DOI: 10.1134/S1070428016120071
Aliphatic and alicyclic diamines are widely used in
the manufacture of polyamides, polyurethanes, and
corrosion inhibitors, as well as curing agents for epoxy
resins [1, 2]. Diamines with exclusively primary amino
groups are necessary for the synthesis of diisocyanates
that are very important intermediate products. How-
ever, reactions of even simple monohydric alcohols
with ammonia over solid catalysts do not stop at the
stage of formation of the corresponding primary amine
formation of 5- and 6-membered nitrogen heterocycles
is a specific side reaction in the amination of diols,
especially of those containing 4 and 5 carbon atoms
between the functional groups [8–10]. On the other
hand, the corresponding diamines would be the most
promising for the synthesis of diisocyanates.
Most diamines are traditionally produced from
dichloroalkanes. Well known disadvantages of this
method are corrosion of the equipment by the action of
liberated hydrogen chloride and difficulties in disposal
of large amounts of sodium chloride. In some cases,
the corresponding dinitriles are used as starting mate-
rials for large-scale production of primary aliphatic
diamines [11].
(
Scheme 1).
Scheme 1.
ROH
+
NH3
ROH
ROH
RNH2
+
+
H O
2
RNH2
+
R NH
2
H O
2
R NH
2
+
R N
+
+
H O
3
2
Comparison of different methods for the synthesis
of diamines with respect to accessibility of starting
materials, environmental safety, corrosion of the
equipment, and the possibility of extending the product
series showed that catalytic amination of diols de-
serves keen attention. The main obstacle on the way to
wider application of this method is its insufficient
exploration.
2
RNH2
R NH
2
+
NH3
R NH
2
+
RNH2
R N
3
NH3
It is known that the heat of formation of a primary
amine is close to zero and that further alkylations to
secondary and tertiary amines are weakly exothermic
(
7 kcal/mol for each stage) [3]. Assuming that the
entropy contribution is minimum, the transformation
of primary amine to secondary and then to tertiary is
thermodynamically favorable. The reduced selectivity
for primary amine in consecutive reversible reactions
may be proved by using larger ammonia-to-alcohol
ratios and/or recycling secondary and tertiary amines.
The goal of the present work was to study hetero-
geneous catalytic amination of some γ-, δ-, and
ε-glycols with essentially different structures so as to
elucidate the effect of steric factors on the reaction
selectivity. As substrates we selected linear butane-1,4-
diol, dipropylene glycol (a mixture of three isomers),
and alicyclic cyclohexane-1,4-diyldimethanol.
The amination process becomes more complicated
when the starting compounds are diols [4–10]. Among
a variety of concomitant processes, cyclization with
The reactions of glycols with ammonia were carried
out in a flow reactor over nickel/copper/chromium
1
756

STERIC EFFECTS IN THE CATALYTIC AMINATION OF γ-, δ-, AND ε-GLYCOLS
1757
a
Table 1. Amination of butane-1,4-diol (1) with ammonia over nickel/copper/chromium catalyst
Catalyst composition, %
Selectivity, mol %
Temperature,
Conversion
of 1, %
3
Ratio NH –1
°C
Ni
Cu
12
Cr
2
O
3
3
4
5
6
7
3
8
50
180
18:1
29:1
29:1
42:1
54:1
42:1
42:1
42:1
28:1
42:1
77.3
81.1
18.7
82.6
82.1
94.0
38.1
55.2
56.7
78.4
–
−
25.7
41.9
44.1
61.1
59.7
69.2
41.5
64.3
52.3
65.1
17.0
07.0
03.1
05.2
05.9
05.5
05.7
05.9
06.7
02.1
26.6
20.7
21.1
06.9
05.7
04.8
14.2
10.1
14.1
07.6
23.1
1
1
1
1
2
80
60
80
80
00
16.4
12.1
06.4
06.8
04.7
05.5
04.0
05.2
03.4
−
−
−
−
6
0
20
20
130
05.6
03.8
20.2
01.5
1
1
1
40
40
50
a
–1
–1
Volume rates; 1, 0.13 h ; hydrogen, 250 h ; pressure 20.0 MPa.
catalysts that are commonly used in the amination of
monohydric alcohols [12–14]; in addition, hydrogen
was supplied to prevent deactivation of the catalyst
and formation of by-products (imines, enamines, and
nitriles) [7, 8]. From the reaction mixtures obtained in
the amination of butan-1,4-diol (1) under different
ucts, 4-(pyrrolidin-1-yl)butanamine (5), 4-(pyrrolidin-
1-yl)butan-1-ol (6), and butane-1,4-diyldipyrrolidine
(7) (Table 1). Thus, the catalytic amination of butane-
1,4-diol with ammonia can be represented as shown in
Scheme 2.
We then proceeded with catalytic amination of iso-
meric dipropylene glycols constituting a commercially
available product, 1,1′-oxydipropan-2-ol (8a, 27.2%),
conditions (130–200°C, NH -to-1 ratio 18:1 to 54:1)
3
we isolated and identified several products (Table 1),
but no targeted butane-1,4-diamine (2) was detected.
2
2
-(2-hydroxypropoxy)propan-1-ol (8b, 57.2%), and
,2′-oxydipropan-2-ol (8c, 25.6%).
Only in a few cases, at a relatively low temperature
and in the presence of excess ammonia, we succeeded
in detecting partial amination product, 4-aminobutan-
The reactive hydroxy groups in all isomers 8a–8c
are separated by a five-atom chain. The isomers differ
only by the position of the methyl groups that are
located either in the α-position with respect to the
reaction center (8c) or attached directly thereto (8a).
1
-ol (3); the conversion of diol 1 increased as the tem-
perature rose. The main reaction direction was cycliza-
tion of 3 to pyrrolidine (4) and its N-alkylation prod-
Scheme 2.
NH3
NH
–
2H O
–C H N
4 9
2
4
–
H O
2
NH3
OH
NH2
HO
HO
–
H O
2
NH3
1
3
NH2
N
–
H O
2
5
NH
H O
OH
N
NH –NH3
–
2
6
NH
H O
N
N
–
2
7
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 12 2016

1
758
TIMOFEEV et al.
a
Table 2. Amination of dipropylene glycol isomers 8a–8c with ammonia over nickel/copper/chromium catalyst
Selectivity, mol %
Temperature,
Dipropylene glycol
isomer
Conversion
of 8a–8c, %
°C
diamine
amino alcohol
dimethylmorpholine
1
1
1
2
70
80
90
00
8a
41.3
41.3
38.5
40.9
70.5
70.0
66.3
69.5
85.4
83.3
80.9
83.5
94.3
93.9
95.0
94.2
18.4
03.5
−
80.6
43.8
09.5
47.6
46.3
35.8
01.0
33.2
40.0
31.7
−
−
8
8
8
b
51.5
86.3
42.9
−
c
a–8c
07.0
53.0
02.9
−
8a
8
8
8
b
54.1
98.0
46.2
03.7
59.0
99.9
49.7
50.8
87.5
99.8
c
a–8c
16.1
55.4
02.9
−
8a
8
8
8
b
c
a–8c
16.7
28.4
01.5
−
35.0
17.7
10.8
−
8a
8
8
8
b
c
a–8c
08.6
11.0
79.4
a
–1
–1
Catalyst composition, mol %: Ni, 38; Cu, 12; Cr
hydrogen pressure 20.0 MPa.
2
O
3
, 50; molar ratio NH
3
–8 86:1; volume rates: 8a–8c, 0.13 h ; hydrogen, 250 h ;
One methyl group in isomeric diol 8b shields the
reaction center, while the other is distant from the
hydroxy group. These structural differences between
isomers 8a–8c were clearly reflected in the directions
of their reactions with ammonia (Scheme 3, Table 2).
propylene glycol 8c which lacks steric hindrances (no
methyl group on the reaction center) was converted
almost completely into cyclic 3,5-dimethylmorpholine
(11c). The corresponding cyclization product, 2,6-di-
methylmorpholine (11a), was formed from sterically
hindered glycol 8a only at elevated temperature,
whereas the major products were 2-(2-aminopropoxy)-
1-methylethan-1-amine 9a and 1-(3-aminopropoxy)-
propan-2-ol (10a). Dipropylene glycol 8b having one
primary hydroxy group reacted with ammonia to give
As follows from the data in Table 2 and Scheme 3,
the reaction gives three types of products: target di-
amines 9a and 9b, isomeric amino alcohols 10a–10d,
and cyclization products, isomeric dimethylmorpho-
lines 11a–11c. Like linear butane-1,4-diol (1), di-
Scheme 3.
R1
R4
R1
R4
R1
R4
NH3
NH3
O
O
O
HO
OH
–H O
HO
NH2
–H O
H N
NH2
2
2
2
R2
R3
R2
R3
R2
R3
8
a–8c
10a–10d
9a, 9b
–
H O
2
R2
R1
O
R3
N
H
R4
1
1a–11c
1
4
2
3
1
3
2
4
1
4
2
3
1
3
2
4
R = R = Me, R = R = H (a); R = R = Me, R = R = H (b); R = R = H, R = R = Me (c); R = R = H, R = R = Me (d).
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 12 2016

STERIC EFFECTS IN THE CATALYTIC AMINATION OF γ-, δ-, AND ε-GLYCOLS
1759
Table 3. Effect of the catalyst composition on the selectivity of amination of dipropylene glycol isomers 8a–8c
Catalyst
Selectivity, mol %
amino
Run
no.
Tempera-
ture, °C
Conversion
of 8, %
mole fraction, %
Isomer
Ni/Cu
ratio
dimethyl-
diamine
alcohol
morpholine
Ni
38
Cu
12
2 3
Cr O
1
50
3:1
180
8a
70.5
70.0
66.3
69.5
73.4
68.7
56.8
68.1
78.0
77.2
69.8
76.3
89.2
86.9
81.1
86.6
87.9
87.1
81.6
53.0
02.9
−
46.3
35.6
1.0
−
8
8
8
b
54.1
98.0
46.2
03.2
64.1
98.1
52.9
37.2
83.1
99.9
73.8
30.0
79.4
99.0
69.2
0.
c
a–8c
16.1
48.8
03.9
−
33.2
44.6
30.0
−
2
60
20
20
3:1
170
8a
8
8
8
b
c
a–8c
15.5
34.2
01.9
−
29.3
25.0
13.9
−
1
80
8a
8
8
8
b
c
a–8c
10.4
32.4
01.8
−
14.8
28.9
18.7
−
3
4
44
33
6
50
34
7:1
1:1
180
170
8a
8
8
8
b
c
a–8c
09.8
49.9
02.8
−
18.6
50.0
38.3
−
33
8a
8
8
8
b
57.2
98.6
48.1
c
a–8c
86.5
15.2
35.4
a
–1
–1
Molar ratio NH
3
–8a–8c 86:1; volume rates: 8a–8c, 0.13 h ; hydrogen, 250 h ; pressure 20.0 MPa.
mainly 2,5-dimethylmorpholine (11b) and a mixture
of 1-(1-aminopropan-2-yloxy)propan-2-ol (10b) and
was observed at a Ni/Cu ratio of 1:1 (Table 3, run
no. 4); this selectivity was retained up to a Ni/Cu ratio
of 3:1 (run nos. 1, 2). Further raising the nickel frac-
tion to a Ni/Cu ratio of 7:1 (run no. 3) sharply reduced
the selectivity to 32%. Increase of the overall nickel
and copper content of the catalyst, the Ni/Cu ratio
being the same, almost did not affect the selectivity for
the diamine.
2
-(2-aminopropoxy)propan-1-ol (10d).
The conversion of dipropylene glycol isomers in-
creased at elevated temperature (Table 2). The tem-
perature dependence of the selectivity for diamines
displayed a maximum at 180–190°C, whereas the
selectivity for amino alcohols was higher at lower
temperature. It was found that decrease of the NH –1
The above relations were used to choose optimal
catalyst composition and temperature conditions for
the amination of cyclohexane-1,4-diyldimethanol (12).
Diol 12 (a solid under normal conditions) was fed into
the reactor as a solution in water.
3
molar ratio from 86:1 to 43:1 leads to reduction of the
selectivity for diamines 9 and amino alcohols 10 and
increase of the selectivity for dimethylmorpholines.
With the amination of dipropylene glycol as model
substrate we examined how the composition of the
Ni/Cu/Cr catalyst affects the reaction direction
Apart from external factors, positive results were
anticipated taking into account primarily the structure
of diol 12 where the hydroxy groups are separated by
six carbon atoms. In this case, cyclization of interme-
diate amino alcohol would give rise to a seven-mem-
bered azepane ring which is less favorable than pyr-
rolidine and morpholine. Furthermore, like methyl
(
Table 3). It is known [15] that nickel and copper form
a solid solution whose composition determines
physicochemical properties of the catalyst and, prob-
ably, the selectivity of the process. The results showed
that the maximum selectivity for the diamine (~50%)
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 12 2016

1
760
TIMOFEEV et al.
Scheme 4.
–
H O
2
NH3
NH3
OH
NH2
NH2
NH
–
H O
2
–H O
–NH3
HO
HO
2
H N
2
1
2
13
14
15
groups in dipropylene glycol 8a, methylene groups of
the cyclohexane ring should create steric hindrances to
the cyclization. Finally, the chair conformation typical
of cyclohexane does not favor cyclization, though this
factor is likely to be insignificant since the chair→boat
transition readily occurs at elevated temperature.
gramming from 75 to 225°C). Dipropylene glycol [16]
and reaction mixtures obtained therefrom were
analyzed using a 2000×3-mm column packed with
15% of Carbowax 20M on Chezasorb AW (oven tem-
perature programming from 120 to 180°C.
The nickel/copper/chromium catalysts were pre-
pared according to the procedure described in [17, 18],
which allowed variation of the composition and
physicochemical properties of the reduced catalysts.
As expected, the reaction mixtures obtained by
amination of cyclohexane-1,4-diyldimethanol con-
tained target cyclohexane-1,4-diyldimethanamine (13)
as the major product (up to 75% selectivity), a small
amount of partial amination product, 4-(aminomethyl)-
cyclohexan-1-ylmethanol (14), and cyclization product,
The amination of diols was carried out in standard
3
flow setups consisting of a 200-cm stainless steel
reactor equipped with an electrical heating jacket and
3
-azabicyclo[3.2.2]nonane (15) (Scheme 4, Table 4).
a thermocouple pocket. The reactor was charged with
3
Thus, factors hampering cyclization of intermediate
1
00–200 cm of the catalyst (grain size 1.5–3.0 mm)
amino alcohols in the amination of glycols, primarily
steric hindrances at the reaction centers, favor forma-
tion of the corresponding diamines. The relations
found may be useful for proper choice of initial diols
and conditions for the synthesis of diamines.
which was reduced with a hydrogen–nitrogen gas mix-
ture over a period of 12 to 24 h at a temperature of up
to 400°C. When the reduction was complete, the reac-
tor was adjusted to a required temperature and a hydro-
gen pressure of 20.0 MPa, and hydrogen and ammonia
were supplied at a flow rate of 25–50 and 60–400 L/h,
respectively; the corresponding diol or its aqueous so-
lution was then fed at a flow rate of 13–40 mL/h.
EXPERIMENTAL
The initial diols and amination products were
analyzed by GLC on a Tsvet-500 chromatograph
equipped with a thermal conductivity detector. The
reaction mixtures obtained by amination of butane-
The products were analyzed by GLC. After GLC
analysis, the reaction mixtures were subjected to frac-
tional distillation, and the isolated nitrogen-containing
compounds were identified by their known physical
constants, as well as by titration [19]. Elemental com-
positions were determined for the newly synthesized
compounds.
1
,4-diol and cyclohexane-1,4-diyldimethanol were
analyzed using a 2000×3-mm column packed with
2% of PFMS-4 (polyphenylmethylsiloxane) on Poli-
khrom-1 (carrier gas helium; oven temperature pro-
1
a
Table 4. Amination of cyclohexane-1,4-diyldimethanol (12) with ammonia over nickel/copper/chromium catalyst
Selectivity, mol %
Temperature,
Concentration of 12 in
Conversion
°C
aqueous solution, %
of 12, %
1
3
14
15
1
1
1
1
1
90
90
90
80
90
50
50
70
70
70
80.1
76.6
87.4
67.0
72.8
12.0
17.0
03.1
16.0
70.2
74.5
68.1
75.2
71.0
73.1
2.3
1.7
3.5
2.9
4.1
a
–1
–1
Catalyst composition, mol %: Ni, 60; Cu, 20; Cr
2 3 3
O , 20; molar ratio NH –12 86:1; volume rates: 12, 0.13 h ; hydrogen, 250 h ;
hydrogen pressure 20.0 MPa.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 52 No. 12 2016

STERIC EFFECTS IN THE CATALYTIC AMINATION OF γ-, δ-, AND ε-GLYCOLS
1761
1
-(2-Aminopropoxy)propan-2-amine (9a). bp 74–
8. Baiker, A. and Kijenski, J., Catal. Rev.: Sci. Eng.. 1985,
vol. 27, p. 653.
7
5°C (10 mm). Found, %: C 54.5; H 12.3; N 21.1.
Calculated, %: C 54.5; H 12.2; N 21.2.
9. Wulff-Doring, J., Hesse, M., Melder, J.P., Buskens, P.,
and Voit, G., EP Patent Appl. no. 963975, 1999; Chem.
Abstr., 2000, vol. 132, no. 13313y.
Amino alcohols 10a–10d (mixture of isomers).
bp 99–102°C (10 mm). Found, %: C 54.2; H 11.3;
N 10.6. Calculated, %: C 54.1; H 11.4; N 10.5.
1
0. Kliger, G.A., Glebov, L.S., Lesik, O.A., and Lok-
tev, S.M., Neftekhimiya, 1991, vol. 31, p. 221.
4
-Aminobutan-1-ol (3). bp 95–99°C (10 mm),
1
1. Luyken, H., Volt, G., Basster, P., Rehfinger, A., and
2
0
20
mp 16–17°C, d = 0.964, n = 1.4612; published data
4
D
Fischer, R., US Patent no. 6207851, 2001; Chem.
Abstr., 2001, vol. 133, no. 205233m.
2
4
0
[20]: bp 97– 99°C (10 mm), mp 16–18°C, d = 0.963,
2
0
n = 1.4610.
D
12. Huang, J.-M., Monatsh. Chem., 2013, vol. 144, p. 1187.
20
20
D
1
3. Haese, F., Boettcker, A., Strein, B., Reif, W., and
Melder, J.-P., Int. Patent Appl. no. WO 110869; Chem.
Abstr., 2006, vol. 144, no. 8394u.
Pyrrolidine (4). bp 85–88°C, d4 = 0.8528, n
.443; published data [21]: bp 87–88°C, d = 0.852,
=
2
0
1
4
2
D
0
n = 1.4431.
1
4. Yurchenko, E.N., Kramareva, G.E., Zubritskaja, N.G.,
and Gaidei, T.P., React. Kinet. Catal. Lett., 1995,
vol. 55, p. 425.
4
-(Pyrrolidin-1-yl)butan-1-amine (5). bp 204°C;
published data [17]: bp 205°C.
4
-(Pyrrolidin-1-yl)butan-1-ol (6). bp 107–109°C
15. Kornilov, I.I., Matveeva, N.M., Pryakhina, L.I., and
Polyakova, R.S., Metallokhimicheskie svoistva elemen-
tov periodicheskoi sistemy (Metallochemical Properties
of Elements of the Periodic System), Moscow: Nauka,
1966, p. 225.
2
0
20
(
[
10 mm), d4 = 0.9428, nD = 1.476; published data
18]: bp 103–104°C (7 mm), d = 0.943, n = 1.4705.
2
4
0
20
D
Dimethylmorpholines 11a–11c (mixture of iso-
mers). bp 145°C, d = 0.935, n = 1.4470; published
data [23]: bp 146°C, d = 0.9348, n = 1.4460.
2
0
20
D
4
2
4
0
20
D
16. Cuillemonal, A., Peiffer, G., and Traynard, J.C., Bull.
Soc. Chim. Fr., 1968, p. 1369.
4
-(Aminomethyl)cyclohexan-1-yl methanol (13).
1
7. Zubritskaya, N.G., Kozlova, O.V., Korol’kova, O.G.,
Firsov, O.P., and Yurchenko, E.N., RU Patent
no. 2050196, 1995; Ref. Zh., Khim., 1996, no. 15L98P.
2
0
bp 128–132°C (10 mm), n = 1.498; published data
25]: bp 127–130°C (10 mm), n = 1.4985.
D
2
0
[
D
Cyclohexane-1,4-diyldimethanamine (14).
18. Zubritskaya, N.G., Kozlova, O.V., Korol’kova, O.G.,
Yurchenko, E.N., and Firsov, O.P., RU Patent
no. 2050197, 1995; Ref. Zh., Khim., 1996, no. 16L86P.
2
0
20
bp 108–112°C (10 mm), d4 = 0.9425, nD = 1.4945;
2
4
0
published data [24]: bp 106–111 (10 mm), d
=
2
0
1
9. Siggia, S. and Hanna, J.G., Quantitative Organic
Analysis via Functional Groups, New York: Wiley,
0
.9419, n = 1.4941.
D
3
-Azabicyclo[3.2.2]nonane (15). mp 185°C; pub-
1
979, 4th ed. Translated under the title Kolichestvennyi
lished data [26]: mp 190°C.
organicheskii analiz po funktsional’nym gruppam,
Moscow: Khimiya, 1983, p. 405.
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