Samarium iodides catalyzed meso-epoxides ring opening by aromatic amines

Article abstract of DOI:10.1016/j.tetlet.2004.08.048

Samarium diiodide catalyzes the ring opening of meso-epoxides by several aromatic amines affording β-aminoalcohols at room temperature. The use of bis-binaphthoxy iodo samarium allows an enantioselective desymmetrization of cyclohexene oxide by o-anisidin

Full text of DOI:10.1016/j.tetlet.2004.08.048

Tetrahedron
Letters
Tetrahedron Letters 45 (2004) 7749–7751
Samarium iodides catalyzed meso-epoxides ring opening
by aromatic amines
*
´
Fabien Carree, Richard Gil and Jacqueline Collin
´ ˆ ´
Laboratoire de Catalyse Moleculaire UMR 8075, ICMMO, Batiment 420 Universite Paris-Sud 91405 Orsay, France
Received 16 June 2004; revised 9 August 2004; accepted 10 August 2004
Abstract—Samarium diiodide catalyzes the ringopeningof meso-epoxides by several aromatic amines affording b-aminoalcohols at
room temperature. The use of bis-binaphthoxy iodo samarium allows an enantioselective desymmetrization of cyclohexene oxide by
o-anisidine.
Ó 2004 Elsevier Ltd. All rights reserved.
1. Introduction
and trivalent samarium iodides catalyze the ringopening
of epoxides by amines and by silylated nucleophiles.11a,b
The b-aminoalcohols are important organic compounds
with numerous applications in medicinal and organic
chemistry and as chiral auxiliaries for asymmetric syn-
thesis.1,2 They are typically obtained by ringopening
of epoxides by amines but the use of elevated tempera-
tures and excess of amines are often required to perform
these reactions.3 Since milder conditions are highly
desirable to prepare sensitive molecules, various alterna-
tive methods have been studied, such as a variety of cat-
alysts,4–7 or reaction media such as fluorous solvents8
and ionic liquids.9 Amongst the different types of Lewis
acids that have been described, metal halides,5 triflates,6
or lithium bistriflimide7 are revealed as efficient catalysts
for the ringopeningof epoxides with aromatic amines.
We have previously studied the reaction of aliphatic
amines with epoxides in the presence of catalytic
amounts of samarium diiodide to produce b-aminoal-
cohols. We have now extended this study to the ring
openingof cyclic epoxides by aromatic amines. Results
are gathered in the Table 1. In a typical experiment,
addition of the aromatic amine to 10% SmI2(THF)2 sus-
pended in methylene chloride was followed by addition
of the epoxide. Reactions of aniline and cyclohexene
oxide were first examined and afforded the b-amino-
alcohol as the trans isomer in good yield without the
formation of side products after one night at room tem-
perature (entry 1). Decreasingthe catalytic ratio to
5% did not bringany modification in the yield in reac-
tion product (70%). We then tested the reaction of var-
ious aromatic amines substituted by electron donating
or withdrawinggroups (entries 2–4) to obtain the corre-
sponding b-aminoalcohols in satisfactory yields. The
reaction of other cyclic epoxides, cyclohexadiene mon-
oxide 1b and cyclopentene epoxide 1c with aniline and
substituted anilines afforded similarly the corresponding
trans b-aminoalcohols except for p-nitroaniline. Yet, the
reaction of aniline with cycloheptene oxide afforded only
small amounts (<10%) of the corresponding b-aminoal-
cohol after 24h.
The applications of lanthanide derivatives in catalysis
have grown rapidly due to their high Lewis acid proper-
ties and their non-toxicity.10 Lanthanide chlorides5g,h
and triflates6a,b can thus be used for the ringopening
reactions of epoxides. We have shown the interest of
samarium diiodide as a Lewis acid type catalyst for var-
ious reactions, such as Mukaiyama aldol and Michael
reaction, [4 + 2] cycloaddition and sequences of succes-
sive reactions includingMukaiyama Michael-aldol and
Michael-iminoaldol tandem reactions.11 In the course
of these investigations we found that samarium diiodide
OH
10% SmI2(THF)2
CH2Cl2, rt
+
O
NH2
Keywords: Samarium diiodide; Lanthanides; Epoxides ringopening;
b-Aminoalcohol; Enantioselective catalysis.
Correspondingauthor. Tel.: +33 1 69154740; fax: +33 1 69154680;
e-mail: jacollin@icmo.u-psud.fr
N
H
*
1a
2
3a-1
0040-4039/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2004.08.048

´
F. Carree et al. / Tetrahedron Letters 45 (2004) 7749–7751
7750
Table 1. Ringopeningof meso-epoxides catalyzed by samarium diiodide
Entry
Epoxide
Amine
Product
OH
Yielda,b
N
H
Ar
1
2
3
4
1a
1a
1a
1a
Aniline
3a-1
3a-2
3a-3
3a-4
75
75
57
76
o-Anisidine
p-Anisidine
p-Bromoaniline
OH
N
H
Ar
5
6
7
8
9
1b
1b
1b
1b
1b
Aniline
3b-1
3b-2
3b-3
3b-4
3b-5
80
72
75
93
0
o-Anisidine
p-Anisidine
p-Bromoaniline
p-Nitroaniline
OH
Ar
N
H
10
11
11
12
1c
1c
1c
1c
Aniline
3c-1
3c-2
3c-3
3c-4
50
61
63
78
o-Anisidine
p-Anisidine
p-Bromoaniline
a % in isolated product. Typical procedure: a solution of o-anisidine (276mg, 2.2mmol) in 5mL CH2Cl2 is transferred under argon on a suspension of
SmI2(THF)2 (110mg, 0.2mmol).11e Cyclohexene oxide (200lL, 2mmol) is then added with a syringe. The reaction medium is stirred for 18h at
room temperature and quenched by a hydrochloric acid solution (1M) followed by a neutralization. After extraction and drying, the residue is
purified by flash chromatography on silica (cyclohexane/AcOEt: 80/20).
b All products have been precedently reported and have been characterized by NMR, IR, and MS spectroscopies.
Catalytic enantioselective ringopeningof meso-epoxides
has been a focus of interest as an efficient method to cre-
ate two contiguous asymmetric centers. Efficient cata-
lysts have been reported for reactions with various
nucleophiles such as PhSH, PhOH, TMSN3, TMSCN.12
However, there are only a few reports concerningthe
enantioselective catalysis of the ringopeningof epoxides
by amines.13 Titanium-binol catalysts afforded aminoal-
cohols with high asymmetric induction by reacting epox-
nide chlorides,5g while better inductions were observed
with ytterbium triflate in the presence of binol.13b Shiba-
saki and co-workers developed a praseodymium com-
plex, Pr(R)AbinolAPPh3P@O, which afforded the
enantioselective ringopeningof meso-epoxides with p-
anisidine and applied this method to the formal synthe-
sis of 4-demethoxydaunomycin.13c These results
prompted us to report our first results concerningthe
enantioselective aminolysis of meso-epoxides.
13a
ides containingketal groups with aliphatic amines.
Two systems involvinglanthanides and binaphthol cat-
alyze the openingof cyclohexene oxide by aniline. Low
enantiomeric excesses were first reported usinglantha-
We have precedently described the preparation of new
lanthanide iodobinaphthoxides and their application
for enantioselective Diels–Alder and iminoaldol reac-
OH
10% cat
O
+
O
.(THF)
cat
Sm
I
NH2
2
N
H
O
CH2Cl2, 100% conv
OMe
3a-2
MeO
1a
4
rt
18 h
18 h
52% ee
65% ee
72% yield
65% yield
0 ˚C
OH
10% cat
CH2Cl2, 100% conv
+
O
NH2
OMe
N
H
3b-2
MeO
1b
4
rt
18 h
68% ee
60% yield

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F. Carree et al. / Tetrahedron Letters 45 (2004) 7749–7751
7751
tions.14 We have now found that bis-binaphthoxy iodo
samarium (prepared from samarium triiodide and bis
potassium (R)-binaphthoxide) catalyzes the reaction of
cyclohexene oxide and cyclohexadiene monoxide with
o-anisidine, affordingthe corresponding b-aminoalco-
hols 3a-2 and 3b-2 in good yields and with, respectively,
52% and 68% enantiomeric excess at room temperature.
Asymmetric induction is increased by loweringtempera-
ture. The enantioselective desymmetrization of various
epoxides with aromatic amines catalyzed by lanthanide
iodobinaphthoxides is currently under study.
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Rama Rao, K. Synthesis 2001, 831–832; (i) Zhao, P. Q.;
Xu, L. W.; Xia, C. G. Synlett 2004, 846–850; (j) Swamy,
N. R.; Goud, T. V.; Reddy, S. M.; Krishnaiah, P.;
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6. (a) Chini, M.; Crotti, P.; Favero, L.; Macchia, F.;
Pineschi, M. Tetrahedron Lett. 1994, 35, 433–436; (b)
Meguro, M.; Asao, N.; Yamamoto, Y. J. Chem. Soc.,
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Samarium diiodide allows to perform ringopeningof
epoxides by aromatic amines with good yields in mild
conditions and these reactions can be extended to the
enantioselective synthesis of b-aminoalcohols with chi-
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7. Cossy, J.; Bellosta, V.; Hamoir, C.; Desmurs, J. R.
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´
´
Acknowledgements
We thank CNRS for financial support and MNESER
for Ph.D. grant for F.C.
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