Bi(OTf)3-catalyzed allylation of epoxides: A facile synthesis of homoallylic alcohols

Article abstract of DOI:10.1016/S0040-4039(03)01559-4

Epoxides react smoothly with tetraallyltin in the presence of 2 mol% of Bi(OTf)₃ under mild reaction conditions to afford the corresponding homoallylic alcohols in excellent yields with high regioselectivity while aryl aziridines produce exclusively allyl amines in good yields under similar conditions.

Full text of DOI:10.1016/S0040-4039(03)01559-4

TETRAHEDRON
LETTERS
Pergamon
Tetrahedron Letters 44 (2003) 6501–6504
Bi(OTf) -catalyzed allylation of epoxides: a facile synthesis of
3
homoallylic alcohols
J. S. Yadav,* B. V. S. Reddy and G. Satheesh
Division of Organic Chemistry, Indian Institute of Chemical Technology, Hyderabad 500 007, India
Received 7 March 2003; revised 10 June 2003; accepted 20 June 2003
Abstract—Epoxides react smoothly with tetraallyltin in the presence of 2 mol% of Bi(OTf) under mild reaction conditions to
3
afford the corresponding homoallylic alcohols in excellent yields with high regioselectivity while aryl aziridines produce exclusively
allyl amines in good yields under similar conditions.
©
2003 Elsevier Ltd. All rights reserved.
The stereoselective addition of allylmetal reagents to
aldehydes, imines and epoxides is one of the most
important carbonꢀcarbon bond forming reactions in
and can be easily prepared, even on multi-gram scale,
in the laboratory from commercially available bis-
muth(III) oxide and triflic acid. Owing to its unique
7
1
organic synthesis. In particular, Lewis acid catalyzed
catalytic properties, bismuth(III) triflate has been exten-
8
carbon–carbon bond forming reactions are of great
significance in organic synthesis because of their high2
reactivity, selectivity and mild reaction conditions.
Epoxides and aziridines are versatile building blocks for
sively used for a plethora of organic transformations
9
including rearrangement of oxiranes. However, there
have been no reports on the allylation of epoxides with
allyltin reagents employing Bi(OTf) as catalyst.
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3
the synthesis of many bioactive natural products. They
are well-known carbon electrophiles capable of reacting
with various nucleophiles and their ability to undergo
regioselective ring opening reactions contributes largely
Herein, we wish to report the use of Bi(OTf) as a
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remarkable Lewis acid for the allylation of aryl epox-
ides with tetraallyltin to produce the corresponding
homoallylic alcohols under mild conditions (Scheme 1).
4
to their synthetic value. Despite a number of methods
that have been reported for the cleavage of epoxides
and aziridines with various nucleophiles, only a few
5
Accordingly, treatment of styrene oxide with tetraallyl
methods are reported for the allylation of epoxides and
aziridines with allylmetal reagents. Moreover, many of
these methods produce a mixture of products and thus
the desired products are obtained in low to moderate
yields. Therefore, the development of simple and novel
reagents, which are more efficient and provide conve-
nient procedures with improved yields, is needed.
tin in the presence of 2 mol% Bi(OTf) afforded the
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6
corresponding 1-phenyl-4-penten-2-ol in 87% yield
(entry a). In a similar fashion, various aryl substituted
epoxides reacted smoothly with tetraallyl tin to give the
correspnding homoallylic alcohols in excellent yields.
Cycloalkyl oxiranes such as 1,2-dihydronaphthalene
oxide and indene oxide also gave the corresponding
homoallylic alcohols (entries e, f). Even the sterically
hindered stilbene oxides and 2-naphthyl oxirane
afforded the respective homoallylic alcohols in high
Recently, bismuth(III) triflate has attracted the interest
of synthetic organic chemists because it is inexpensive
Scheme 1.
Keywords: bismuth triflate; allylation; oxiranes; homoallylic alcohols.
*
Corresponding author. Fax: 91-40-27170512; e-mail: yadav@iict.ap.nic.in
0
040-4039/$ - see front matter © 2003 Elsevier Ltd. All rights reserved.
doi:10.1016/S0040-4039(03)01559-4

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J. S. Yada6 et al. / Tetrahedron Letters 44 (2003) 6501–6504
Scheme 2.
Scheme 3.
Table 1. Bi(OTf) -catalyzed allylation of epoxides and aziridines
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J. S. Yada6 et al. / Tetrahedron Letters 44 (2003) 6501–6504
6503
yields (entries g, h, i). In all cases, the reactions pro-
ceeded rapidly at room temperature with high selectiv-
ity. No regioisomers were detected in the H NMR
References
1
spectrum of crude products. This clearly indicates that
the oxiranes do not undergo cleavage with tetraallyltin
under these reaction conditions. Initially, the epoxides
1
. (a) Yamamoto, Y.; Asao, N. Chem. Rev. 1993, 93, 2207–
2293; (b) Marshall, J. A. CHEMTRACTS 1992, 5, 75–
106; (c) Ramachandran, P. V. Aldrichimica Acta 2002, 35,
23–35.
undergo rearrangement in the presence of Bi(OTf) to
3
generate the corresponding aldehydes. These in situ
formed aldehydes react rapidly with tetraallyl tin to
afford the corresponding homoallylic alcohols (Scheme
2. Kobayashi, S. Eur. J. Org. Chem. 1999, 15–27.
3
4
5
. (a) Shimizu, M.; Yoshida, A.; Fujisawa, T. Synlett 1992,
204–206; (b) Bonini, C.; Righi, G. Synthesis 1994, 225–
238; (c) McCoull, W.; Davis, F. A. Synthesis 2000, 1347–
1365.
2).
. (a) Smith, J. G. Synthesis 1984, 629–656; (b) Kump, J. E.
G. In Comprehensive Organic Synthesis; Trost, B. M.;
Fleming, I., Eds.; Pergamon Press: Oxford, 1991; Vol. 7,
p. 469.
. (a) Rao, A. S.; Paknikar, S. K.; Kirtane, J. G. Tetra-
hedron 1983, 39, 2323–2367; (b) Tanner, D. Angew.
Chem., Int. Ed. Engl. 1994, 33, 599–619; (c) Yadav, J. S.;
Anjaneyulu, S.; Ahmed, M. M.; Reddy, B. V. S. Tetra-
hedron Lett. 2001, 42, 2557–2559.
However, in the absence of catalyst, the reactions did
not proceed even under reflux conditions after a long
reaction time (8–12 h). Interestingly, a 2-phenyl-
aziridine also underwent cleavage rapidly with tetraallyl
tin in the presence of 2 mol% Bi(OTf) to give the
3
corresponding 2-phenyl-N-(p-toluenesulfonyl)-pent-4-
en-1-amine in 82% yield (entry j). The allyl transfer
occurred exclusively at the benzylic carbon to produce
the g-amino olefin (Scheme 3).
6. (a) Taber, T. H.; Lee, M. C. J. Org. Chem. 1997, 62,
342–9344; (b) Overman, L. E.; Renhowe, P. A. J. Org.
9
Chem. 1994, 59, 4138–4142; (c) Imai, J.; Nishida, S. J.
Org. Chem. 1990, 55, 4849–4852; (d) Kozikowski, A. P.;
Ishida, H.; Isobe, K. J. Org. Chem. 1979, 44, 2788–2790;
Similarly, p-methyl- and p-chlorophenylaziridines were
opened with tetraallyl tin to generate the corresponding
g-amino olefin derivatives (entries k, l). The product
obtained from p-chlorophenylaziridine is a key interme-
diate for the synthesis of the antispastic agent,
Baclofen. Arylaziridines underwent cleavage in a
regioselective manner with preferential attack at the
benzylic position. In the case of aryl aziridines, the
reactions proceeded efficiently at room temperature
with high regioselectivity. Among the various metal
(
e) Scheider, M.-R.; Mann, A.; Taddei, M. Tetrahedron
Lett. 1996, 37, 8493–8496.
7
8
9
. Repichet, S.; Zwick, A.; Vendier, L.; Le Roux, C.;
Dubac, J. Tetrahedron Lett. 2002, 43, 993–995.
. Leonard, M. N.; Wieland, L. C.; Mohan, R. S. Tetra-
hedron 2002, 58, 8373–8397.
. Bhatia, K. A.; Eash, K. J.; Leonard, N. M.; Oswald, M.
C.; Mohan, R. S. Tetrahedron Lett. 2001, 42, 8129–8132.
1
0
triflates such as Bi(OTf) , Yb(OTf) , In(OTf) and
3
3
3
10. Phung, A. N.; Braun, J.; Goffic, F. L. Synth. Commun.
1995, 25, 1783–1788.
Ce(OTf) tested for this transformation, bismuth(III)
3
triflate was found to be the most effective catalyst in
terms of conversion and reaction rates. However, 5
mol% of scandium triflate also gave similar results
under the present reaction conditions. As solvent,
dichloromethane appeared to give the best results.
Other allylating agents such as allyltributylstannane
and allyltrimethylsilane also reacted smoothly with
11. General procedure: A mixture of the epoxide (2 mmol),
bismuth triflate (0.05 mmol) and tetraallyltin (1 mmol) in
dichloromethane (10 mL) was stirred at room tempera-
ture for the specified time (see Table 1). After completion
of the reaction as indicated by TLC, the reaction mixture
was quenched with water (15 mL) and extracted with
dichloromethane (2×10 mL). Evaporation of the solvent
followed by purification on silica gel (Merck, 100–200
mesh, ethyl acetate–hexane, 0.5–9.5) afforded the pure
homoallylic alcohol. The spectroscopic data of all the
products were identical with data reported in litera-
epoxides in the presence of 2 mol% Bi(OTf) , but the
3
reactions took longer and the products were obtained
in only moderate yields. The scope and generality of
this process is illustrated with respect to various epox-
ides, aziridines and tetraallyl tin and the results are
10,12
1
ture.
Spectral data for selected products: 3a:
H
NMR (CDCl ) l: 1.50–1.60 (br s, 1H, OH), 2.10–2.38
3
11
presented in Table 1.
(
1
m, 2H), 2.60–2.80 (m, 2H), 3.79–3.85 (m, 1H), 5.05 (dd,
H, J=1.9, 10.2 Hz), 5.15 (dd, 1H, J=1.9, 17.3 Hz),
In summary, this paper describes a mild and efficient
protocol for the allylation of aryl substituted epoxides
and aziridines with tetraallyl tin using bismuth(III)
triflate as a novel catalyst. This method is a useful and
attractive strategy for the preparation of homoallylic
alcohols from epoxides in a single operation.
5.75–5.90 (tdd, 1H, J=6.5, 10.2, 17.3 Hz), 7.15–7.38 (m,
5H). IR (KBr): w 3415, 2925, 2855, 1641, 1494, 1453,
1076, 1033, 915, 746 cm . EIMS: m/z: 162 M , 121, 103,
−
1
+
9
1
2
2. HRMS calcd. for C H O: 162.1045. Found:
11 14
1
62.1019. 3f: H NMR (CDCl ) l: 1.95 (br s, 1H, OH),
3
.50 (d, 2H, J=6.4 Hz), 2.90 (d, 2H, J=17.5 Hz), 3.05
(
d, 2H, 17.5 Hz), 5.15 (dd, 1H, J=1.8, 10.3 Hz), 5.20 (dd,
1
1
2
1
H, J=1.8, 17.3 Hz), 5.90–6.05 (tdd, 1H, J=6.4, 10.3,
7.3 Hz), 7.15–7.30 (m, 4H). IR (KBr): w 3410, 3072,
Acknowledgements
−1
925, 1579, 1480, 1273, 1024, 915, 735 cm . EIMS: m/z:
+
74 M , 155, 139, 131, 112, 103, 89, 76, 69, 52, 42.
B.V.S. thanks CSIR, New Delhi for the award of a
fellowship.
HRMS calcd. for C H O: 174.1044. Found: 174.1068.
3h: H NMR (CDCl ) l: 1.80 (br s, 1H, OH), 2.15–2.40
12 14
1
3

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J. S. Yada6 et al. / Tetrahedron Letters 44 (2003) 6501–6504
m, 2H), 4.0 (d, 1H, J=6.7 Hz), 4.39–4.50 (m, 1H), 12. (a) Abenhaim, D. P.; Henry-Basch, E.; Freon, P.
(
5
1
7
1
.10 (dd, 1H, J=1.7, 10.2 Hz), 5.20 (dd, 1H, J=1.7,
7.3 Hz), 5.90–6.10 (tdd, 1H, J=6.5, 10.2, 17.3 Hz),
.20–7.50 (m, 10H). IR (KBr) w: 3415, 2930,
Bull. Soc. Chim. Fr. 1970, 179–182; (b) Likhar,
P. R.; Kumar, M. P.; Bandyopadhyay, A. K.
Tetrahedron Lett. 2002, 43, 3333–3335; (c) Yadav,
J. S.; Reddy, B. V. S.; Pandey, S. K.; Srihari,
P.; Prathap, I. Tetrahedron Lett. 2001, 42, 9089–
9092.
−
1
664, 1595, 1497, 1301, 1221, 1071, 757 cm EIMS:
+
m/z: 238 M , 196, 168, 152, 140, 112, 89, 65, 42.
HRMS calcd. for C H O: 238.1357. Found: 238.1329.
17
18