Microwave-assisted aminolysis of epoxides under solvent-free conditions catalyzed by montmorillonite clay

Article abstract of DOI:10.1039/a804379e

The reaction of primary and secondary amines with epoxides in the presence of montmorillonite K10 clay, under solvent-free conditions and microwave irradiation affords high yields of β-amino alcohols.

Full text of DOI:10.1039/a804379e

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128 J. CHEM. RESEARCH (S), 1999
J. Chem. Research (S),
1999, 128±129$
Microwave-assisted Aminolysis of Epoxides Under
Solvent-free Conditions Catalyzed by Montmorillonite
Clay$
Mohammad M. Mojtahedi,a Mohammad R. Saidi*a and
Mohammad Bolourtchianb
aDepartment of Chemistry, Sharif University of Technology, P.O. Box 11356-9516, Teheran, I. R. of Iran
bChemistry & Chemical Engineering Research Center of Iran, P.O. Box 14335-186, Teheran, I. R. of Iran
The reaction of primary and secondary amines with epoxides in the presence of montmorillonite K10 clay, under solvent-
free condtions and microwave irradiation affords high yields of ꢀ-amino alcohols.
Table 1 Distribution of the ring opening products of epoxides
b-Amino alcohols are important organic compounds in
biological and pharmaceutical processes. One of the best
by primary and secodary amines
routes to synthesize these compounds involves the regio-
selective ring opening of oxiranes at elevated temperatures1,2
or in the presence of metal salts such as lithium per-
chlorate,3 samarioum iodide,4 cobalt(II) chloride,5,6 lithium
methanetri¯uorosulfonate,7 titanium tetraisopropoxide,8 and
polymer-supported reagents.9 In many of these cases, the
ring opening of epoxides is carried out in a solvent, and
normally requires many hours at re¯ux temperature under
environmentally unfriendly conditions.
Montmorillonite K10 clay has long been known to show
strong solid acidity, and has been used as a catalyst in
organic reactions. Microwave-assisted treatment of liquid
and solid samples has been a very helpful method for
organic and inorganic synthesis and its application in rapid
synthetic organic chemistry has received much attention in
recent years.10±12
In this paper we report a new, simple, and fast procedure
for ring opening of epoxides with a cheap and convenient
heterogeneous catalyst. These reactions are performed in a
domestic conventional microwave oven, under solvent-free
conditions, although more sophisticated microwave reactors
are now commercially available.
When epoxide 1 were treated with 1.0 equivalent of a
primary or secondary amine 2 in the presence of 0.2 g
montmorillonite K10 clay under microwave irradiation,
without any solvent, complete reaction took place, leading
to b-amino alcohols 3a±m (Scheme 1).
The reaction takes place in the solid phase, in an open
vessel, and the products can be extracted from the support
by solvent. The starting epoxides, products and yields are
shown in Table 1.
Scheme 1
Distribution of the products in Table 1 shows that the
regioselectivity of ring opening of the epoxide is low in
some cases. Ring opening of epoxides in entries 8, 9 and 12,
13 occur with very high regioselectivity. Only one product
was obtained in these cases. The low yield of 3j and 3k may
be due to evaporation of starting epoxide during microwave
heating, since no epoxide was found in the product after
microwave irradiation. Increasing the amount of epoxide in
*To receive any correspondence (e-mail: Saidi@ch.sharif.ac.ir).
$This is a Short Paper as de®ned in the Instructions for Authors,
aThe yield after 3 h at 70 8C (oil bath) was only 25%. bThe only
Section 5.0 [see J. Chem. Research (S), 1999, Issue 1]; there is there-
product.
fore no corresponding material in J. Chem. Research (M).

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J. CHEM. RESEARCH (S), 1999 129
entries 10 and 11 did not change the yield in these reactions.
However irradiation for 30 s with a 2 min interval gave a
35% yield of b-amino alcohol 3k.
References
1 X. L. Fu and S. H. Wa, Synth. Commun., 1997, 27, 1677.
2 A. J. Shuker, M. G. Siegel, D. P. Matthews and L. O. Weigel,
Tetrahedron Lett., 1997, 38, 6149.
3 M. Chini, P. Crotti and F. Macchia, Tetrahedron Lett., 1990, 31,
4661.
4 P. Van de Weghe and J. Collin, Tetrahedron Lett., 1995, 36,
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5 J. Iqbal and A. Pandey, Tetrahedron Lett., 1990, 31, 575.
6 A. De, S. Ghosh and J. Igbal, Tetrahedron Lett., 1997, 38, 8379.
7 J. Auge and F. Leroy, Tetrahedron Lett., 1996, 37, 7715.
8 A. Vidal-Ferran, A. Moyano, M. A. Pericas and A. Riera,
J. Org. Chem., 1997, 62, 4970.
9 M. Hori and K. D. Janda, J. Org. Chem., 1998, 63, 889.
10 Y. Izumi, K. Urabe and M. Onaka, Zeolite, Clay and Heterpoly
Acid in Organic Reaction, VCH, New York, 1992, pp. 21±47.
11 S. Caddick, Tetrahedron, 1995, 51, 10403.
Experimental
Montmorillonite K10 clay was activated in the microwave
oven for 5 min just before use. The products were puri®ed by
column chromatography, using aluminium oxide, eluting with light
petroleum, if needed. All compounds were identi®ed by NMR and
IR spectroscopy.13
General Procedure for the Preparation of ꢀ-Amino Alcohols.Ð
mixture of epoxide (1 mmol), amine (1 mmol) and mont-
A
morillonite K10 clay (0.2 g) was placed in a Te¯on container with a
screw cap. Then the mixture was irradiated with high power
(900 W) in a conventional microwave oven for 1 min. After the
mixture was cooled to room temperature, it was washed with
dichloromethane (2Â 10 ml). The solvent was evaporated and the
product(s) were identi®ed.
12 C. R. Strauss and R. W. Trainor, Aust. J. Chem., 1995, 48,
1665.
13 Selected Spectroscopic Data.ÐCompounds 3a±3g, 3j and 3k
have been synthesized previously.3,4 The 1H NMR and 13C
NMR spectra were recorded on a Bruker AC80 instrument
using CDCl3 as solvent. Chemical shifts are in ppm relative to
TMS. 3h: ꢁH 1.28±1.51 (m, 4H), 1.98±2.52 (m, 6H), 3.01±3.18
(m, 2H), 3.42±3.63 (m, 1H), 3.63±3.90 (m, 3H), 4.70±5.12
(m, 2H), 5.34±5.88 (m, 1H). ꢁC 23.46 (CH2), 54.34 (CH2), 59.18
(CH2), 67.94 (CH2), 72.24 (CH2), 72.94 (CH), 116.82 (CH2),
134.76 (CH). 3i: ꢁH 2.12±2.75 (m, 6H), 3.31 (t, J ˆ 5.8 Hz,
4H), 3.41±4.06 (m, 6H), 4.85±5.38 (m, 2H), 5.52±6.11 (m, 1H).
ꢁC 53.88 (CH2), 61.53 (CH2), 66.29 (CH2), 66.75 (CH2), 77.23
(CH2), 77.33 (CH), 116.88 (CH2), 134.69 (CH). 3l: ꢁH 1.01 (d,
J ˆ 6.0 Hz, 6H), 1.61±1.88 (m, 4H), 2.27±2.76 (m, 6H), 3.34±
3.98 (m, 3H), 4.51 (s, 1H). ꢁC 21.92 (CH3), 23.99 (CH2), 54.20
(CH2), 59.10 (CH2), 68.10 (CH2), 70.91 (CH), 71.92 (CH).
3m: ꢁH 1.20 (d, J ˆ 6.1 Hz, 6H), 2.40±2.86 (m, 6H), 3.30±3.58
(m, 5H), 3.58±4.10 (m, 4H). ꢁC 21.73 (CH3), 53.67 (CH2), 61.37
(CH2), 66.22 (CH2), 66.60 (CH2), 70.42 (CH), 71.75 (CH).
In conclusion, ring opening of epoxides with primary
and secondary amines can be achieved within 1 min under
environmentally friendly solvent-free conditions under
microwave irradiation in the presence of montmorillonite
K10 clay as solid support. These organic reactions are
safe and take place more rapidly and with higher yields
compared to conventional heating.
Financial support of this work from the Iranian Scienti®c
Research Council is greatly acknowledged.
Received, 9th June 1998; Accepted, 12th November 1998
Paper E/8/04379E