Potassium dodecatungstocobaltate trihydrate (K5CoW 12O40·3H2O) as an efficient catalyst for aminolysis of epoxides

Article abstract of DOI:10.1081/SCC-200032411

Aminolysis of epoxides using various amines was catalyzed with potassium dodecatungstocobaltate trihydrate in a convenient and efficient method with good selectivities.

Full text of DOI:10.1081/SCC-200032411

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Potassium
Dodecatungstocobaltate
Trihydrate
(K5CoW12O40 · 3H2O) as
an Efficient Catalyst for
Aminolysis of Epoxides
E. Rafiee a , Shahram Tangestaninejad a , M. H.
Habibi a & V. Mirkhani a
a Department of Chemistry, University of Isfahan,
Isfahan, 81746‐73441, Iran
Version of record first published: 19 Apr 2010.
To cite this article: E. Rafiee , Shahram Tangestaninejad , M. H. Habibi & V.
Mirkhani (2004): Potassium Dodecatungstocobaltate Trihydrate (K5CoW12O40 · 3H2O)
as an Efficient Catalyst for Aminolysis of Epoxides, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry,
34:20, 3673-3681
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SYNTHETIC COMMUNICATIONSw
Vol. 34, No. 20, pp. 3673–3681, 2004
Potassium Dodecatungstocobaltate
.
Trihydrate (K5CoW12O40 3H2O) as an
Efficient Catalyst for Aminolysis of Epoxides
*
E. Rafiee, Shahram Tangestaninejad, M. H. Habibi,
and V. Mirkhani
Department of Chemistry, University of Isfahan, Isfahan,
81746-73441, Iran
ABSTRACT
Aminolysis of epoxides using various amines was catalyzed with potas-
sium dodecatungstocobaltate trihydrate in a convenient and efficient
method with good selectivities.
Key Words: Aminolysis; Epoxides; Potassium dodecatungstocobaltate
trihydrate.
Aminolysis of epoxides is an excellent synthetic tool for construction
of b-amino alcohols and has been well exploited for the synthesis of
*
Correspondence: E. Rafiee, Department of Chemistry, University of Isfahan,
Isfahan, 81746-73441, Iran; Tel.: þ98-311-7932705; Fax: þ98-311-6689732;
E-mail: e.rafiee@sci.ui.ac.ir.
3673
DOI: 10.1081/SCC-200032411
0039-7911 (Print); 1532-2432 (Online)
www.dekker.com
Copyright # 2004 by Marcel Dekker, Inc.

3674
Rafiee et al.
pharmacologically interesting compounds.[1] A wide variety of catalysts have
already been applied to the aminolysis of epoxides, including CoCl2,[2] Ti (O-
i-Pr)4,[3] SmI2,[4] metal triflates,[3,5–8] basic metal amides,[9] diisopropoxyalu-
minum trifluoroacetate,[10] TaCl5,[11] CeCl3,[12] and montmorillonite.[13]
However, some of the drawbacks of these methods are the long reaction
times, the use of large amounts of expensive catalysts, and low chemo-
regio- and stereoselectivity. Hence, the development of new catalysts with
more efficiency and better selectivity is of interest.
.
Potassium dodecatungstocobaltate (K5CoW12O40 3H2O) is apparently
a perfect outer-sphere one-electron oxidant,[14] due to the presence of a
sheath of chemically inert oxygen atoms, which protect the central ion
from undesired inner-sphere substitution reactions. For this reason, electron
.
transfer with (K5CoW12O40 3H2O) typically leads to selective reactions
and clean chemistry. This advantage has encouraged us to continue our inves-
[15,16]
.
tigation of applications of (K5CoW12O40 3H2O) in organic synthesis.
We wish to describe here that aminolysis of epoxides can be effectively
catalyzed by a cheap and easily prepared cobalt heteropoly compound
.
(K5CoW12O40 3H2O) (Sch. 1).
We first examined the reaction of some representative epoxides with
.
aniline and (K5CoW12O40 3H2O) (5 mole%) in acetonitrile to give the corre-
sponding amino alcohols in 93–98% yields (Table 1). Ring opening of epox-
ides occurs with very high regioselectivity, and only one product was obtained
in these cases (except for 1,2-octeneoxide) (Table 1).
This success encouraged us to exploit the generality of the reaction to a
few other amines. Treatment of epoxides with sterically hindered aromatic
amines, such as 2-chloroaniline or 2-methoxyaniline and other amines,
affords the corresponding amino alcohols in good yields.
The reaction rates depend on the structures of the amines and the epox-
ides. With nonaromatic epoxides, the primary carbon is much more reactive
toward amines than the secondary one. Interesting to note is that aliphatic sec-
ondary amines also responded well, with excellent yields. We believe that due
to the protection of the central cobalt ion with inert oxygen atoms, aliphatic
amines, even those with strong complexation ability, could not attach the
Scheme 1.

Potassium Dodecatungstocobaltate Trihydrate
3675
Table 1. Aminolysis of epoxides in the presence of potassium dodecatungstocobal-
tate trihydrate.
St. no.
Epoxide
Amine
Aniline
Time (h)
%Yielda
1
2
Cyclohexeneoxide
3
93
93
94
92
95
94
91
93
60
80
98
93
96
98
97
97
98
98
64
74
93
98
93
99
97
93
98
98
85
76
98
93
93
96
94
99
90
93
74
2-Chloroaniline
4-Ethylaniline
3
3
3
4
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4-Methylpiperidine
Aniline
2.5
3.5
2.5
3.75
3.25
7
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
7
Styreneoxide
3.5
3.5
1.5
2
2-Chloroaniline
4-Ethylaniline
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4-Methylpiperidine
Aniline
1.75
2.5
4
1
6
6
1-Allyloxy-2,3-
epoxypropane
4
2-Chloroaniline
4-Ethylaniline
4
2
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4-Methylpiperidine
Aniline
2.5
3.75
4
4
3.5
6
6
2,3-Epoxypropyl-
isopropyl ether
4
2-Chloroaniline
4-Ethylaniline
2
2.5
2
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4
3.75
4.75
2.25
7
(continued)

3676
Rafiee et al.
Table 1. Continued.
St. no.
Epoxide
Amine
Time (h)
%Yielda
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
4-Methylpiperidine
Aniline
7
76
96(96/4)b
1,2-Octeneoxide
3.5
4
2-Chloroaniline
4-Ethylaniline
95(61/39)b
2.5
4
92(74/26)b
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4-Methylpiperidine
Aniline
97(78/22)b
1.5
4
98(64/36)b
98(67/33)b
6
86(81/19)b
5
98(92/8)b
7
45(89/11)b
7
54(89/11)b
93
98
2,3-Epoxypropyl-
phenyl ether
4.5
4
2-Chloroaniline
4-Ethylaniline
1
98
97
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4-Methylpiperidine
Aniline
1.75
3.5
3
98
98
4
98
98
0.75
7
75
78
6
Epichlorohydrine
4
95
92
2-Chloroaniline
4-Ethylaniline
3.5
2
89
97
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4-Methylpiperidine
Aniline
2.5
3
96
96
4.5
6
92
99
5.5
7
98
98
6
Buthyl glycidyl ether
3.5
3.25
1.75
1.5
4.25
3.5
5.5
2.5
7
98
98
2-Chloroaniline
4-Ethylaniline
98
99
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
98
94
98
98
94
(continued)

Potassium Dodecatungstocobaltate Trihydrate
3677
Table 1. Continued.
St. no.
Epoxide
Amine
Time (h)
%Yielda
80
81
82
83
84
85
86
87
88
89
90
4-Methylpiperidine
Aniline
7
98
96
96
97
98
99
99
99
98
98
97
Epibromohydrine
1
2-Chloroaniline
4-Ethylaniline
1.5
1
4-Methylaniline
2-Methoxyaniline
3-Methoxyaniline
4-Methoxyaniline
4-Bromoaniline
3-Methylpiperidine
4-Methylpiperidine
2.5
3
3
2.5
2.5
6
6
aDetermined by GLC analysis of crude product.
bRatio of (major/minor) product.
cobalt ion and deactivate it. However, such deactivation has been previously
reported for metal triflate, TaCl5 and CeCl3 as catalysts. With 1,2-octeneoxide,
the regioselectivity is lower, but the attack on the less-hindered side of the
epoxide remains preponderant.
.
In conclusion, (K5CoW12O40 3H2O) can be regarded as an efficient cat-
alyst for ring opening of epoxide with amines of low nucleophilicity. All
b-amino alcohols are obtained in good yields with high regioselectivity.
EXPERIMENTAL
.
The (K5CoW12O40 3H2O) was prepared according to the previously
reported procedures.[15,16] All products were identified by comparison of
their physical and spectroscopic data with authentic samples prepared in
accordance with the procedures in the literature.[2,5,10,13,17]
General Procedure for the Preparation of b-Amino Alcohols
A solution of the epoxide (1.0 mmol) in acetonitrile (2.5 ml) was treated
.
with (K5CoW12O40 3H2O) (0.02 mmol) and the amine (2 mmol). The mixture
was stirred at reflux until completion [monitored by gas chromatography (GC)
or thin-layer chromatography (TLO)]. The catalyst was filtered, and the
reaction mixture was washed with water. Diethyl ether was added, and after

3678
Rafiee et al.
separation of phases, the organic layer was dried over Na2SO4 and purified on
silica-gel plates or silica-gel column.
SPECTROSCOPIC DATA OF SOME OF THE
b-AMINOALCOHOLES
trans-2-(4-Ethylanilino)cyclohexan-1-ol (Entry 3): viscous liquid, IR
1
(KBr, cm21): 3487–3299 (NH and OH), 1587, 1516, 1069, H-NMR
(CDCl3, 200 MHz) d 0.9–1.0 (m, 1H), 1.2 (t, J ¼ 4.65, 3H),
1.25–1.5 (m, 3H), 1.7–1.8 (m, 2H), 2.16–2.20 (m, 2H), 2.9 (s, 1H),
3.21–3.47 (m, 3H), 3.55–3.8 (m, 1H), 6.79 (t, J ¼ 4.5 Hz, 1H), 6.90
(d, J ¼ 9 Hz, 2H), 7.25 (t, J ¼ 4.5 Hz, 2H). Analysis calculated
for C14H21NO; C, 76.67; H, 9.65; N, 6.39. Found: C, 76.75; H, 9.70;
N, 6.45.
trans-2-(4-Bromoanilino)cyclohexan-1-ol (Entry 8): yellow solid,
m.p. 126–1288C (lit. 125–1278C), IR (KBr, cm21): 3497–3286
(NH and OH), 1580, 1506, 1063, H-NMR (CDCl3, 200 MHz) d 1.09
1
(m, 1H), 1.38 (m, 3H), 1.72 (m, 2H), 1.92–2.23 (m, 2H), 2.94–3.2
(ddd, J ¼ 10.9, 9.4, 3.8 Hz, 1H), 3.22–3.42 (ddd, J ¼ 10.1, 10.1,
4.3 Hz, 1H), 3.51–4.07 (bs, 2H), 6.49 (d, J ¼ 10.3 Hz, 2H), 7.22
(d, J ¼ 10.3 Hz, 2H). 13C-NMR (CDCl3, 200 MHz) d 24.6, 25.3,
31.8, 33.7, 60.9, 74.8, 110.6, 116.5, 132.5, 146.9.
2-(4-Ethylanilino)-1-phenylethanol (Entry 11): viscous yellow liquid,
IR (KBr, cm21): 3500–3140 (NH and OH), 1557, 1510, 1089,
1H-NMR (CDCl3, 200 MHz) d 1.90 (br s., 1H, OH, D2O exch.),
3.80 (dd, J ¼ 6.9, 10.7 Hz, 1H), 3.85 (dd, J ¼ 4.1, 10.7 Hz, 1H),
4.60 (dd, J ¼ 6.9, J ¼ 10.7 Hz, 1H), 6.50 (d, J ¼ 8.3 Hz, 2H), 6.80
(t, J ¼ 8.0 Hz, 1H), 7.25 (t, J ¼ 8.1 Hz, 2H), 7.30–7.45 (m, 5H).
Analysis calculated for C14H15NO; C, 78.87; H, 7.04; N, 6.57.
Found: C, 77.75; H, 7.10; N, 6.45.
1-Anilino-2-octanol (Entry 41): viscous liquid; IR (NaCl, cm21): 3598–
1
3100 (NH and OH), 1592, 1495, H-NMR (CDCl3, 200 MHz) d 0.92
(t, J ¼ 7 Hz, 3H), 1.24–1.86 (m, 10H), 3.21 (dd, J ¼ 10, 10 Hz, 2H),
3.32 (dd, J ¼ 8, 4 Hz, 1H), 3.91 (m, 1H), 6.68–7.35 (m, 5H), 13C-
NMR (CDCl3, 200 MHz) d 14.5, 23.0, 26.0, 29.8, 32.2, 35.5, 51.0,
70.7, 114.0, 118.7, 129.7, 151.6, Analysis calculated for C14H23NO;
C, 75.97; H, 10.47; N, 6.33. Found: C, 75.71; H, 10.66; N, 6.48.
1-Anilino-3-chloro-2-propanol (Entry 61): viscous liquid; IR (NaCl,
cm21): 3504–3100 (NH and OH), 1594, 1497, 1090, 1H-NMR

Potassium Dodecatungstocobaltate Trihydrate
3679
(CDCl3, 200 MHz) d 3.24 (m, 2H), 3.45 (dd, J ¼ 10.1, 4.8 Hz, 1H),
3.72 (d, J ¼ 8 Hz, 2H), 4.12 (m, 1H), 6.74 (m, 3H), 7.19 (m, 2H),
13C-NMR (CDCl3, 200 MHz) d 47.7, 48.1, 70.2, 113.9, 118.9, 129.9,
148.0, Analysis calculated for C9H12ClNO; C, 58.23; H, 6.51; N,
7.54. Found: C, 58.02; H, 6.68; N, 7.69.
ACKNOWLEDGMENT
We thank the University of Isfahan Research Council for support of this
work.
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Received in the UK December 12, 2003