Bismuth(III) trifluoromethanesulfonate and trifluoroacetate as convenient and efficient catalysts for regio- and chemoselective ring opening of epoxides in reactions with anilines

Article abstract of DOI:10.1007/s11178-005-0016-2

Bismuth(III) trifluoromethanesulfonate and trifluoroacetate are highly efficient and practical catalysts for oxirane ring opening in reactions of epoxides with substituted anilines. The reactions are characterized by high chemoselectivity and good to exce

Full text of DOI:10.1007/s11178-005-0016-2

Russian Journal of Organic Chemistry, Vol. 40, No. 9, 2004, pp. 1332–1336. From Zhurnal Organicheskoi Khimii, Vol. 40, No. 9, 2004, pp. 1379–1383.
Original English Text Copyright © 2004 by Khosropour, Khodaei, Ghozati.
Bismuth(III) Trifluoromethanesulfonate
and Trifluoroacetate as Convenient and Efficient
Catalysts for Regio- and Chemoselective Ring Opening
of Epoxides in Reactions with Anilines*
A. R. Khosropour, M. M. Khodaei, and K. Ghozati
Department of Chemistry, Razi University, Kermanshah, 67149 Iran
e-mail: arkhosropour@razi.ac.ir
Received October 20, 2003
Abstract—Bismuth(III) trifluoromethanesulfonate and trifluoroacetate are highly efficient and practical
catalysts for oxirane ring opening in reactions of epoxides with substituted anilines. The reactions are
characterized by high chemoselectivity and good to excellent yields of the products.
β-Amino alcohols are universal synthons which
are widely used in organic chemistry. Some β-amino
alcohols are starting compounds for the synthesis of
dihydrooxazoles which were proposed as protecting
groups [1]. β-Amino alcohols exhibit insecticide pro-
perties and are used as chiral ligands in asymmetric
syntheses [2–4]. In addition, the β-amino alcohol frag-
ment is a very important functional group in some
physiologically active natural compounds, e.g.,
Sphingosine, which is an intracellular secondary mes-
senger [5]. Therefore, elaboration of simple and eco-
logically clean procedures for the synthesis of β-amino
alcohols constitutes a field of extensive research in
organic synthesis.
require the use of expensive reagents, long reaction
time, and severe conditions; they are characterized
by poor yields (especially in reactions with aliphatic
epoxides) and are accompanied by side processes
involving polymerization and rearrangements of initial
oxiranes. Acid-catalyzed opening of the oxirane ring in
epoxy compounds has received a limited application,
and careful control of the acidity of the medium is
necessary to prevent side reactions. Therefore, deve-
lopment of new efficient procedures for the above
transformations remains an important problem.
In a series of recent publications it was noted that
the use of bismuth compounds in organic reactions
is ecologically friendly [16–19]. Moreover, bismuth
derivatives are widely used in medicine [20–23].
A number of bismuth salts are commercially available,
cheap, easy to handle with, and relatively stable in air
in the presence of a small amount of moisture [24–26].
Despite diverse pharmacological activity and syn-
thetic applications, little attention was given to
methods of synthesis of β-amino alcohols. The most
important procedures are based on opening of epoxy
derivatives with amines in the presence of Lewis acids
[6–14] or ionic liquids [15]. These procedures often
Taking into account our interest in bismuth(III)
salts [27–30] as ecologically clean reagents for organic
Scheme 1.
Bi(OTf)3 or Bi(TFA)3, MeCN,
room temperature or reflux
O
R2
+
H2N
R1
R2
NH CH2
CH R1 or R2
OH
NH CH CH2OH
R1
R = Ar, Alk; R' =H, Me, Br.
* The original article was submitted in English.
1070-4280/04/4009-1332 © 2004 MAIK “Nauka/Interperiodica”

BISMUTH(III) TRIFLUOROMETHANESULFONATE AND TRIFLUOROACETATE
1333
Table 1. Reactions of epoxy derivatives with aromatic amines in the presence of Bi(TFA)3 and Bi(OTf)3
Catalyst Bi(OTf)3
amount reaction
of catalyst, time,
Catalyst Bi(TFA)3
Run
no.
Producta
amount reaction
of catalyst, time,
yield,b
%
yield,b
%
mmol
0.02
0.01
0.03
0.02
0.01
0.02
0.02
0.01
0.03
0.02
0.01
0.03
0.02
0.01
0.03
0.02
0.02
0.03
0.02
0.02
0.03
min
c30c
30
c45c
c15c
c15c
c15c
30
mmol
0.04
0.03
0.07
0.04
0.03
0.04
0.04
0.03
0.07
0.04
0.03
0.07
0.04
0.03
0.07
0.04
0.04
0.04
0.04
0.04
0.1
min
c35c
60
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
17
18
19
20
21
trans-2-Phenylaminocyclohexanol
trans-2-p-Tolylaminocyclohexanol
trans-2-p-Bromophenylaminocyclohexanol
PhNHCH(Ph)CH2OH
96
90
99
93
90
92
95
94
90
89
85
88
83
95
98
85
92
89
88
85
92
90
93
90
89
88
82
86
78
83
70
72
70
72
79
70
73
85
80
70
75
80
c45c
c25c
c15c
c15c
30
p-MeC6H4NHCH(Ph)CH2OH
p-BrC6H4NHCH(Ph)CH2OH
PhNHCH2CH(OH)CH2OPh
p-MeC6H4NHCH2CH(OH)CH2OPh
p-BrC6H4NHCH2CH(OH)CH2OPh
PhNHCH2CH(OH)CH2OCH2CH=CH2
p-MeC6H4NHCH2CH(OH)CH2OCH2CH=CH2
p-BrC6H4NHCH2CH(OH)CH2OCH2CH=CH2
PhNHCH2CH(OH)(CH2)5CH3
30
40
60
30
40
45
45
60
85
75
20
35
p-MeC6H4NHCH2CH(OH)(CH2)5CH3
p-BrC6H4NHCH2CH(OH)(CH2)5CH3
PhNHCH2CH(OH)CH2O(CH2)3CH3
p-MeC6H4NHCH2CH(OH)CH2O(CH2)3CH3
p-BrC6H4NHCH2CH(OH)CH2O(CH2)3CH3
PhNHCH2CH(OH)CH2Cl
40
60
90
65
60
80
60
70
90
1000
60
75
p-MeC6H4NHCH2CH(OH)CH2Cl
p-BrC6H4NHCH2CH(OH)CH2Cl
70
85
75
85
a
b
c
All compounds were characterized by the IR, 1H and 13C NMR, and mass spectra.
Yield of the isolated product.
At room temperature.
synthesis, we have already reported that bismuth(III)
trifluoroacetate Bi(TFA)3 and trifluoromethanesulfo-
nate Bi(OTf)3 are very effective catalysts for the trans-
formation of epoxides into thiiranes [31] and 1,3-di-
oxolanes [32]. In continuation of our studies on the
application of bismuth(III) salts in organic synthesis,
the present communication describes a mild and
efficient procedure of oxirane ring opening in epoxy
compounds by the action of aromatic amines in aceto-
nitrile in the presence of Bi(TFA)3 and Bi(OTf)3
(Scheme 1). The catalytic nature and wide potential of
these reagents makes the proposed procedure an attrac-
tive alternative to the existing methods of preparation
of β-amino alcohols.
ence of a catalytic amount of Bi(III) salts. The reac-
tions were carried out at room temperature or at the
boiling point of the mixture, and the corresponding
β-amino alcohols were isolated in good yields. The
results are summarized in Table 1. The observed high
reactivity and selectivity are analogous to those re-
ported for the reactions in the presence of strong Lewis
acids [6–14]. Epoxycyclohexane (as model compound)
readily reacted with aromatic amines in the presence
of Bi(TFA)3 and Bi(OTf)3 within a short time (15–
100 min) and with excellent yields (Table 1, run
nos. 1–3). Unlike the other oxiranes, 1,2-epoxy-1-
phenylethane reacted with aromatic amines (Table 1,
run nos. 4–6) to afford the corresponding β-amino
alcohols as a result of attack on the α-carbon atom with
high yield and regioselectivity. The data in Table 1
show that opening of the oxirane ring in epoxides by
Various epoxides containing both activated and
inactivated groups were brought into reaction with
aniline, p-toluidine, and p-bromoaniline in the pres-
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 9 2004

KHOSROPOUR et al.
1334
the oxirane ring in epoxy derivatives in reactions with
aromatic amines. It is advantageous due to mild reac-
tion conditions, high selectivity, improved yields of
the products, high rate, and experimental simplicity; in
addition, it utilizes stable and nontoxic catalysts.
the action of aromatic amines in the presence of
Bi(OTf)3 is faster than in the presence of Bi(TFA)3;
therefore, the process requires a shorter time. It should
be noted that we failed to obtain the corresponding
β-amino alcohols by reactions with p-nitroaniline,
o-phenylenediamine, and aliphatic amines under
similar conditions. A probable reason is the reduced
nucleophilicity of p-nitroaniline or strong basicity and
complexing power of the above amines with respect to
the catalyst. An analogous pattern was observed pre-
viously [13] in reactions with metal trifluoromethane-
sulfonates as catalysts.
In order to estimate intermolecular chemoselec-
tivity of the catalysts, we performed competing reac-
tions. The results are given in Table 2. No such selec-
tivity was observed previously, and this fact can be
regarded as an additional advantage of the proposed
procedure.
EXPERIMENTAL
The products were identified by comparing their
spectral parameters (1H NMR and IR) with those
reported in the literature. The 1H and 13C NMR spectra
were recorded on a Bruker Avance spectrometer
(200 MHz). The IR spectra were measured on a Shi-
madzu 470 spectrophotometer. GLC analysis was
performed on a Shimadzu Gc-8A chromatograph
equipped with a flame ionization detector. Bismuth(III)
trifluoroacetate and trifluoromethanesulfonate were
prepared by the procedures described in [33, 34].
Thus, the described method is an attractive alter-
native ensuring regio- and chemoselective opening of
Reaction of epoxy derivatives with anilines in
the presence of Bi(TFA)3 and Bi(OTf)3 (general
Table 2. Competing opening of the oxirane ring with aromatic amines in the presence of Bi(TFA)3 and Bi(OTf)3
Yield, % (reaction time, min)
Run
no.
Substrate
Amine
PhNH2
Product
a
b
Bi(OTf)3
Bi(TFA)3
O
O
1
Ph
+
85 (25)
00
80 (25)
00
HO
Cl
Ph
ClCH2
NHPh
NHPh
OH
Ph
2
PhNH2
O
+
87 (20)
08
79 (30)
05
HO
Ph
NHPh
O
O
NHPh
O
OH
3
4
PhNH2
C4H9NH2
+
O
PhO
NHPh
93 (45)c
00
82 (45)c
00
PhO
OH
PhO
N
H
OH
PhNH2
+
NHPh
p-O2NC6H4NH2
95 (30)
00
88 (45)
00
O
OH
NHC6H4NO2-p
OH
a
b
c
0.02 mmol.
0.04 mmol.
At the boiling point.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 40 No. 9 2004

BISMUTH(III) TRIFLUOROMETHANESULFONATE AND TRIFLUOROACETATE
1335
procedure). A 0.03–0.1-mol portion of Bi(TFA)3 or
a 0.01–0.04-mol portion of Bi(OTf)3 was added to
a solution of 1 mol of the corresponding epoxy deriva-
tive and 1 mmol of aniline in 2 ml of acetonitrile. The
mixture was stirred at room temperature or at the
boiling point over a period specified in Table 1. The
progress of the reaction was monitored by GLC or
TLC. When the reaction was complete, the solvent was
evaporated, the residue was washed with 25 ml of
0.5 N hydrochloric acid and extracted with methylene
chloride (3×10 ml), the organic phase was dried over
Na2SO4, the solvent was evaporated, and the crude
product was purified by column or thin-layer chrom-
atography on silica gel. The yields of pure β-amino
alcohols were 70–99%. Spectral parameters of some
β-amino alcohols are listed below.
cm–1: 3504–3100 (NH, OH), 1594, 1497, 1090.
1H NMR spectrum (CDCl3), δ, ppm: 3.24 m (2H), 3.45
d.d (1H, J = 10.1, 4.8 Hz), 3.72 d (2H, J = 8 Hz),
4.12 m (1H), 6.74 m (3H), 7.19 m (2H). 13C NMR spe-
ctrum (CDCl3), δC, ppm: 47.7, 48.1, 70.2, 113.9, 118.9,
129.9, 148.0. Found, %: C 58.02; H 6.68; N 7.69.
C9H12ClNO. Calculated, %: C 58.23; H 6.51; N 7.54.
The authors thank the Razi University Research
Council for partial financial support of this work.
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