Efficient synthesis of β-amino alcohols by regioselective ring opening of epoxides with amines catalyzed by CuFe2O4 nanoparticles

Article abstract of DOI:10.1007/s13738-013-0241-5

A simple and efficient method has been developed for the synthesis of β-amino alcohols by regioselective ring opening of epoxides with amines in the presence of CuFe₂O₄ nanoparticles as a heterogeneous recyclable catalyst at room temperature in high yields.

Full text of DOI:10.1007/s13738-013-0241-5

J IRAN CHEM SOC
DOI 10.1007/s13738-013-0241-5
ORIGINAL PAPER
Efficient synthesis of b-amino alcohols by regioselective ring
opening of epoxides with amines catalyzed by CuFe2O4
nanoparticles
•
Seyed Meysam Baghbanian Maryam Farhang
Received: 13 November 2012 / Accepted: 13 February 2013
Ó Iranian Chemical Society 2013
Abstract A simple and efficient method has been
developed for the synthesis of b-amino alcohols by regio-
selective ring opening of epoxides with amines in the
presence of CuFe2O4 nanoparticles as a heterogeneous
recyclable catalyst at room temperature in high yields.
boiling points when elevated temperature is necessary [12].
Several Lewis acids or Bronsted acids as a useful activator
have been reported; that is, high to excellent regioselectivity
of aminolysis of epoxides has been observed with Zn(OAc)2
[14], sulfamic acid [15], Al(OTf)3 [16], Er(OTf)3 [17],
InCl3 [18], BiCl3 [19], SbCl3 [20], ZnCl2 [21], InBr3 [22],
CoCl2 [23], Cu(BF4)2 [24], Al2O3 [25], ionic liquids [26],
silica [27, 28], sulfated zirconia [29] and Y(NO3)3Á6H2O
[30]. However, most of the existing methods involve toxic
metal ions and solvent, high cost, high catalyst loading,
corrosive reagents and cumbersome work-up procedures.
Consequently, new procedures that address these draw-
backs are desirable. Magnetic nanoparticles are of great
interest for researchers from a wide range of disciplines,
including magnetic fluids [31], catalysis [32, 33], data
storage, [34] and environmental remediation [35, 36].
Magnetic separation is an attractive alternative to filtration
or centrifugation as it prevents the loss of catalyst and
enhances reusability, making the catalyst to have beneficial
cost and to be promissory for industrial applications. In this
work, we have focused our attention to CuFe2O4 nanopar-
ticles [37] as heterogeneous catalysts in the ring opening of
epoxides with amines.
Keywords CuFe2O4 nanoparticle Á Epoxides ring
opening Á Regioselectivity Á b-Amino alcohols
Introduction
b-Amino alcohols are used as intermediates in the synthesis
of wide range of biologically active natural,
b-blockers as well as insecticidal agent and synthetic
products [1–3] unnatural amino acids [4, 5] and asymmetric
synthesis as chiral auxiliaries [6]. The nucleophilic ring
opening of epoxides with amines group is a well known
route for the synthesis of b-amino alcohols [7–11]. Classical
method for the synthesis of b-amino alcohols involves the
heating of epoxides with an excess of amines at elevated
temperature, which is not only unfavorable to certain
functional groups, but also to the control of regioselectivi-
ties [12, 13]. This classical method has a number of limi-
tations, such as the requirement of an excess of inorganic
base, longer reaction times, low nucleophilicityin the case
of deactivated aromatic amines, and in some cases low
Results and discussion
In this letter, we have described a mild and efficient
method for the nucleophilic ring opening of epoxides with
amines in the presence of CuFe2O4 nanoparticles to afford
the corresponding b-amino alcohols in excellent yields
(Scheme 1).
S. M. Baghbanian (&)
Department of Chemistry, Ayatollah Amoli Branch,
Islamic Azad University, Amol, Iran
e-mail: s.m.baghbanian@iauamol.ac.ir
Initially, in an effort to develop better reaction condi-
tions, different solvents were screened for the preparation
of 1-phenoxy-3-(phenylamino)propan-2-ol 2 from the
M. Farhang
Faculty of Chemistry, Mazandaran University, Babolsar, Iran
123

J IRAN CHEM SOC
NHR2
Table 1 Screening of various solvents for the reaction of glycidyl
phenyl ether with aniline
O
10 mol % Nano CuFe2O4
R2-NH
HO
+
2
R1
r.t
CH2Cl2
R1
Entry Catalyst
(mol%)
Solvent
Time
(h)
Yield
(%)a
Scheme 1 Ring opening of epoxides with amines
1
2
10
10
10
3
CH3CN
EtOH
3
70
5
85
95, 92b
reaction of glycidyl phenyl ether 1 with aniline in the
presence of different amounts of CuFe2O4 nanoparticles
under different conditions (Scheme 2) and the results are
summarized in Table 1.
3
CH2Cl2
CH2Cl2
CH2Cl2
H2O/r.t.
H2O/r.t.
H2O/60 °C
H2O/80 °C
1.5
3
4
85
5
6
2.5
5
90
6
5
10
Among the different solvents studied, the highest yields
were achieved in CH2Cl2 at room temperature (Table 1,
entry 3). Other solvents, such as EtOH and CH3CN gave
the desired products in low yield (Table 1, entries 1–2).
Unfortunately, the corresponding yields were not high with
H2O as a solvent (Table 1, entry 6–10).
7
10
10
10
10
5
25
8
4
40
9
3
55
10
H2O –5 mol%
CTABc
4
65
We have treated the glycidyl phenyl ether with aniline in
the presence of catalytic amount of CuFe2O4 nanoparticles,
under different conditions. When we used a 1:1 mol ratio of
phenyl glycidyl ether and aniline with 10 mol% of catalyst in
CH2Cl2 at room temperature after 1.5 h, 95 % yield of the
corresponding b-amino alcohol was obtained 3a. This suc-
cess encouraged us to examine the generality of this reaction
with various epoxides and amines (Scheme 1), and the
results are summarized in Table 2. The scope of the reaction
was explored using a variety of epoxides and amines of
diverse structures could be used with the results collected in
Table 2. These data indicate that the reaction is highly effi-
cient for all types of substrates. In a similar manner epoxides
(1a–d) reacted smoothly with aromatic and aliphatic amines
to afford the corresponding b-amino alcohols in very good
yields with high regioselectivity. Reaction of phenyl glyc-
idyl ether with p-chloroaniline and p-toluidine lead to reg-
ioselective formation of corresponding b-amino alcohols in
excellent yields (Table 2, entries 2–3). As seen from the
results, a number of aromatic amines have been employed for
the cleavage of glycidyl phenyl ether particularly deacti-
vated amines, such as p-nitroaniline (Table 2, entry 4) which
showed a limited success for the cleavage of epoxides with
other catalysts. In the case of glycidyl phenyl ether, ring
opening takes place in a regioselective manner with prefer-
ential nucleophilic attack at the less hindered carbon atom of
the epoxide (Table 2, entries 1–7), but the reaction of styrene
epoxide with aromatic amines ring opening takes place by
nucleophilic attack at the benzylic carbon (Table 2, entries
8–11), which could be due to the localized positive charge on
the more highly substituted benzylic carbon [43].
Reaction condition: glycidyl phenyl ether (1 mmol), aniline (1 mmol),
catalyst (10 mol%), r.t
a
Isolated yield
b
Yield after the five cycles
c
CTAB (N-cetyl-N,N,N-trimethylammonium bromide)
In addition, allyl epoxy (Table 2, entries 13–17) and
aliphatic alkyl oxirane (Table 2, entries 18–22) reacted
with aromatic and aliphatic amines to give the corre-
sponding b-amino alcohols in very good yields in regio-
selective manner preferentially by terminal attack of the
nucleophile (except for deactivated amines).
An interesting feature of this procedure is that all the
productswereobtainedselectivelyasasingleisomerwithhigh
purity. All the b-amino alcohols prepared were known com-
pounds and their structures were confirmed by their physical
properties and 1H and 13C NMR spectra and comparison with
authentic samples. The catalyst was separated from the reac-
tion mixture by applying external magnetic field and reused
five times without significant loss of catalytic activity.
Experimental
General procedure for synthesis of nano CuFe2O4
CuFe2O4 nanoparticles were prepared by thermal decom-
position of Cu(NO3)2 and Fe(NO3)3 in water in the pres-
ence of sodium hydroxide. In brief, to a solution of
Fe(NO3)3Á9H2O (3.34 g, 8.2 mmol) and Cu(NO3)2Á3H2O
(1 g, 4.1 mmol) in 75 ml of distilled water, 3 g (75 mmol)
of NaOH dissolved in 15 ml of water was added at room
temperature over a period of 10 min, during which reddish
black precipitate was formed. Then, the reaction mixture
was warmed to 90 °C and stirred. After 2 h, it was cooled
to room temperature and the magnetic particles so formed
were separated by a magnetic separator. It was then washed
OH
O
10 mol % Nano CuFe2O4
CH2Cl2
PhNH2
O
NHPh
O
r.t
Ph
Ph
2
1
Scheme 2 Ring opening of glycidyl phenyl ether with aniline
123

J IRAN CHEM SOC
Table 2 Ring opening of epoxides with various amines at room
temperature
Table 2 continued
a
Yield (%)
Entry Epoxide, R1
Amine, R2
Product
a
Yield (%)
[Ref.]
Entry Epoxide, R1
Amine, R2
Product
[Ref.]
OH
H
N
O
O
OH
NH2
H
N
O
Cl
15
NH2
Cl
O
80 [39]
1
95[38]
3o
3a
OH
H
N
N
O
H
N
N
O
NH2
O
OH
16
2
3
O
Cl
Cl
90 [39]
3b
95 [42]
90 [42]
3p
OH
H
O
N
NH2
O
H
N
OH
Me
Me
90 [39]
40 [38]
17
18
3c
3q
3r
NH2
OH
H
O
O
N
O
O2N
OH
H
4
5
NH2
O2N
N
3d
82 [39]
N
O
NH2
H
OH
O
OH
80 [38]
95 [41]
H
3e
N
NH2
19
Me
Me
N
N
H
N
O
OH
OH
90 [39]
80 [39]
6
O
3s
3f
OH
H
N
NH2
20
Cl
O
O
H
Cl
N
7
8
80 [41]
90 [26]
3t
3g
3h
N
H
N
O
N
OH
NH2
H
21
22
N
3u
O
O
H
95 [41]
80 [41]
H
N
H
N
OH
NH2
9
Me
O
H
Me
Cl
O
3v
90 [39]
90 [39]
3i
a
Isolated yield
H
N
O
NH2
10
Cl
O
H
with water (3 9 30 ml) and catalyst was kept in air oven
for overnight at 80 °C. Then, the catalyst was ground in a
mortar pestle and kept in a furnace at 700 °C for 5 h (step
up temperature 20 °C/min) and then cooled to room tem-
perature slowly. 820 mg of magnetic CuFe2O4 nanoparti-
cles were obtained.
3j
N
H
N
O
OH
11
90 [40]
70 [40]
3k
OH
OH
H
N
NH2
12
13
3l
Catalyst characterizations
H
N
O
NH2
The systematic characterization of CuFe2O4 catalyst was
carried out on X-ray diffraction (XRD), scanning electron
microscope (SEM) and transmission electron microscope
(TEM). The X-ray diffraction analysis was done in a
Philips PW 1830 X-ray diffractometer with CuKa source
90 [39]
90 [39]
3m
OH
H
N
O
NH2
Me
14
Me
˚
(k = 1.5418 A) in a range of Bragg’s angle (5–60°) at
room temperature. The X-ray diffraction pattern of the
3n
123

J IRAN CHEM SOC
specified period. After completion of the reaction, the
catalyst was separated from the reaction mixture with an
external magnet and the catalyst was washed several times
with Et2O. The reaction mixture was concentrated under
reduced pressure to afford the crude product. If necessary,
the product was purified by column chromatography over
silica gel or by bulb to bulb distillation to afford the cor-
responding pure b-amino alcohols in excellent yields. The
physical data (IR, NMR) of known compounds were found
to be identical with reported in the literature. Spectroscopic
data for selected examples are shown below.
Fig. 1 X-ray diffraction pattern of CuFe2O4 nanoparticles
calcined sample (Fig. 1) perfectly matches with the
expected cubic spinel structure of CuFe2O4. The average
crystallite size (L) was calculated from X-ray line broad-
ening using (3 1 1) peak and Debye–Sherrer’s equation;
L = 0.89k/bcosh; b is the FWHF and k is the wavelength
of the radiation and was found to be L = 10.3 nm. Scan-
ning electron micrograph (SEM) pictures were taken using
Jeol JSM-5300 microscope (acceleration voltage10 kV).
The sample powder was deposited on a carbon tape before
mounting on a sample holder. To reduce the charge
developed on the sample, gold sputtering was done for
3 min. The SEM of the CuFe2O4 sample is shown in
Fig. 2a. As indicated in this figure, small agglomerated
nanoparticles of disordered surface morphology are
observed. The transmission electron micrographs (TEM)
were obtained with a Philips CM-10 microscope. The
CuFe2O4 sample for TEM was prepared by dispersing the
powdered sample in ethanol by sonication and then drop
drying on a copper grid (400 mesh) coated with carbon
film. As the TEM figure shows the average size of particles
resulted from this method is approximately 5–15 nm. The
particle sizes obtained from TEM are in good agreement
with XRD measurement (Fig. 2b).
1-Phenoxy-3-phenylamino-propan-2-ol (3a): IR (KBr):
3,383, 3,254, 3,050, 2,936, 2,861, 1,682, 1,532, 1,525,
1
1,475, 1,436, 1,336, 1,322, 1,286 cm-1; H NMR (CDCl3,
500 MHz): d 3.22–3.26 (m, 1H), 3.38–3.42 (m, 1H),
3.60–3.65 (m, 2H), 3.98–4.05 (m, 2H), 4.25 (br s, 1H),
6.64–6.68 (m, 2H), 6.70–6.75 (m, 2H), 6.88–6.91 (m, 2H),
7.05–7.25 (m, 2H); 13C NMR (CDCl3, 125 MHz):46.8,
69.7, 70.2, 113.8, 115.8, 117.8, 118.1, 121.3, 129.4, 148.8,
156.6.
2-Phenyl-2-phenylamino-ethanol (3 h): IR (KBr):
3,321, 3,244, 3,047, 3,031, 2,964, 2,834, 1,615, 1,533,
1
1,488, 1,351, 1,212; H NMR (CDCl3, 500 MHz): d 3.78
(dd, 1H, J = 5.0, 10.5 Hz), 3.90 (dd, 1H, J = 4.0,
10.5 Hz), 4.55 (dd, 1H, J = 6.5, 10.8 Hz), 6.40 (d, 2H,
J = 7.5 Hz), 6.80 (t, 1H, J = 7.8 Hz), 6.95 (d, 2H,
J = 8.0 Hz), 7.30–7.45 (m, 5H). 13C NMR (CDCl3,
125 MHz): d 57.8, 68.5, 112.1, 117.8, 126.4, 127.43,
128.5, 129.7, 136.1, 146.8.
1-Benzylamino-3-phenoxy-propan-2-ol (3 l): IR (KBr):
3,272, 3,012, 2,939, 2,848, 1,618, 1,570, 1,468, 1,360,
1
1,258, 1,203; H NMR (CDCl3, 500 MHz): d 2.75–2.85
(m, 1H), 2.95 (br s, 1H), 3.80 (d, 2H, J = 2.0 Hz), 3.95 (d,
2H, J = 5.0 Hz), 4.05–4.15 (m, 1H), 6.85–6.95 (m, 3H),
7.30–7.40 (m, 7H); 13C NMR (CDCl3, 500 MHz): 53.8,
55.3, 68.2, 70.5, 114.7, 121.1, 128.1, 128.3, 128.5, 129.2,
140.1, 158.8.
General procedure for the synthesis of b-amino
alcohols
To a mixture of epoxide and amine (1 mmol) in (2 mL)
CH2Cl2 was added CuFe2O4 nanoparticles (10 mol%) and
the resulting mixture was stirred at room temperature for
1-Allyloxy-3-morpholin-4-yl-propan-2-ol (3p): IR
(KBr): 3,378, 3,259, 2,926, 1,613, 1,523, 1,458, 1,248,
1,237; 1H NMR (CDCl3, 500 MHz): d 2.1–2.3 (m, 6H), 3.2
Fig. 2 a SEM image of
CuFe2O4 nanoparticles b TEM
image of CuFe2O4 nanoparticles
123

J IRAN CHEM SOC
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