F. Mohsenzadeh et al. / C. R. Chimie xxx (2016) 1e8
3
BiCl3/SiO2 (1.25 mol%) under 15 min irradiation led to
quantitative conversion and excellent regioselectivity
(Table 1, entry 3).
Further work showed that SiO2 has poor catalytic ac-
tivity, whereas the yield of the desired product sharply
increased in the presence of BiCl3 to highlight its important
role in catalyzing the reaction (Table 1, entries 6e8).
Nevertheless, the efficiency of BiCl3/SiO2 over BiCl3 itself in
the reaction is clear (Table 1, entries 3, 6).
The classical reaction was also studied in the presence of
BiCl3/SiO2 at 25 and 50 ꢀC for 1 h (Table 1, entries 9, 10). The
same results were obtained under microwave irradiation
and classical heating at 50 ꢀC (Table 1, entries 3, 10) to
highlight the role of the catalyst.
The higher catalytic activity of BiCl3/SiO2 is due to good
dispersion of BiCl3 over high surface area of silica and may
be attributed to eOeBiOCl catalytic sites.
heating, when aniline derivatives are used as substrates
(Table 3, entries 2, 5e9).
In contrast to styrene oxide, epoxides such as epichlo-
rohydrin and isopropyl glycidyl ether showed lower activ-
ity (Table 3, entries 2, 7, 8).
The reaction was also carried out with aliphatic amines,
e.g., n-hexylamine, benzylamine, cyclohexylamine and
morpholine (Table 3, entries 14e17). Except cyclohexyl-
amine (91%), the other aliphatic amines exhibited moder-
ate selectivity (70%) under microwave heating. When the
same reaction was conducted under thermal heating, both
products A and B were obtained in a ratio of 1:1 (Table 3,
entry 17).
The turnover frequencies (TOF) of all reactions were
calculated to measure the catalyst activity. It was found that
TOF values are in the range of 256e320 hꢁ1 and 58e80 hꢁ1
under microwave and classical conditions, respectively
(Table 3).
In general, the reaction of epoxide with aromatic and
aliphatic amines is regioselective. A tentative reaction route
for the BiCl3/SiO2 catalyzed ring-opening of styrene oxide
with aniline and cyclohexylamine is depicted in Scheme 1.
It is well known that the nature and type of the amine
molecule influence the selective ring-opening of the sty-
rene oxide [11]. Cyclohexylamine as a stronger nucleophile,
attacks on the carbon atom of the epoxide ring with a more
positive charge and less steric hindrance, whereas in the
case of aniline, steric factors predominate over electronic
factors [21,22].
3.2. Recycling of the catalyst
The feasibility of repeated use of BiCl3/SiO2 was also
examined (Table 2). The catalyst was readily isolated from
the reaction mixture. After completion of the reaction,
ethanol (2 mL) was added to the reaction mixture. The
catalyst is insoluble in ethanol and was simply filtered from
the resulting mixture. The recycled catalyst was washed
with ethanol twice more, filtered off and dried at 100 ꢀC
under reduced pressure for 2 h and then reused in the
subsequent run without adding any fresh catalyst. The
reused catalyst is stable under the reaction conditions, and
remains active even in fifth run with no decrease in activity
while high regioselectivity is maintained.
On the other hand, the Lewis acidic sites on the surface
of the BiCl3/SiO2 catalyst are responsible for the activation
of epoxide to enhance the reaction rate.
3.4. Crystal structure of 2-(2,5-dichlorophenylamino)-2-
phenylethanol
3.3. Evaluation of the reaction scope
The excellent preliminary results of the model reaction
led us to expand the generality of this catalyst (BiCl3/SiO2)
to a series of amines and epoxides under solvent-free mi-
crowave and thermal conditions. The results are summa-
rized in Table 3.
It was found that aniline derivatives bearing either
electron-donating (such as methoxy, methyl, and dimethyl)
or electron-withdrawing (such as bromo, chloro, and
dichloro) substituents reacted smoothly to give the corre-
Single crystals of compound 13 (Table 3, entry 13)
suitable for SCXRD measurement were grown by slow
evaporation of an ethanol solution. The unit cell di-
mensions were determined from 2000 reflections. The
structure was solved by the direct method and refined by
full matrix least-squares calculations based on F2 to final
R1 ¼ 0.0793 and wR2 (all data) ¼ 0.2262, using SHELXL-
2014 and WinGX-2013.3 programs [23e29]. The
compound crystallizes in the triclinic system and P1 space
group. Two independent molecules with a molecular for-
mula of C14H14Cl2NO were found in the asymmetric unit
giving a total Z ¼ 4 for the unit cell; a ¼ 8.8614(18),
sponding
b-amino alcohols (Table 3, entries 1e13) in
quantitative yields with high to excellent regioselectivities
(from 90:10 to 100:0). Moreover, the selectivity of products
is almost comparable under microwave and classical
b ¼ 10.969(2), c ¼ 15.914(3),
a
¼ 70.44(3),
b
¼ 78.16(3),
g
¼ 88.87(3), cell volume V ¼ 1424.6(6) Å3, crystal di-
mensions: 0.64 ꢂ 0.34 ꢂ 0.15 mm, measurement range:
Table 2
5.4 < 2q < 50, 4819 independent reflections and max/min
Recyclability of BiCl3/SiO2 (0.25 g) for aminolysis of styrene oxide
(6 mmol) with 4-methoxyaniline (5 mmol).
residual electron density [e Å3]: 0.403/ꢁ0.426. All non-
hydrogen atoms were refined with anisotropic displace-
ment parameters. Hydrogen atoms were placed in ideal
positions and refined as riding atoms with relative isotropic
displacement parameters. A view of the structure is
depicted in Fig. 1. As revealed by X-ray crystallography [30],
the solid state structure of compound 13 exhibits an un-
precedented fourfold R4,4(8) intermolecular hydrogen-
bonding motif [O1eH1O1/O2_$2 d(H/A ¼ 2.724(5)Å
Run
Conversion (%)
Product selectivity
A
B
1st
100
100
100
100
100
95
95
95
92
92
5
5
5
8
8
2nd
3rd
4th
5th
Please cite this article in press as: F. Mohsenzadeh, et al., Greener aminolysis of epoxides on BiCl3/SiO2, Comptes Rendus Chimie
Mohsenzadeh, Farshid
