Bismuth triflate catalyzed Claisen rearrangement of allyl naphthyl ethers

Article abstract of DOI:10.1016/j.tetlet.2006.03.193

Bismuth triflate was found to be an efficient catalyst for the Claisen rearrangement of allyl naphthyl ethers. The reaction proceeds smoothly with a catalytic amount of bismuth triflate (20 mol %) to afford the corresponding ortho-allyl naphthol in moderate to good yields in most cases.

Full text of DOI:10.1016/j.tetlet.2006.03.193

Tetrahedron Letters 47 (2006) 4051–4055
Bismuth triflate catalyzed Claisen rearrangement
of allyl naphthyl ethers
Thierry Ollevier* and Topwe M. Mwene-Mbeja
De´partement de Chimie, Universite´ Laval, Que´bec, Canada G1K 7P4
Received 9 February 2006; revised 28 March 2006; accepted 30 March 2006
Available online 2 May 2006
Abstract—Bismuth triflate was found to be an efficient catalyst for the Claisen rearrangement of allyl naphthyl ethers. The reaction
proceeds smoothly with a catalytic amount of bismuth triflate (20 mol %) to afford the corresponding ortho-allyl naphthol in
moderate to good yields in most cases.
Ó 2006 Elsevier Ltd. All rights reserved.
ortho-Allyl naphthols are versatile intermediates in
the synthesis of biologically active compounds as
1,4-naphthoquinones1a and anthracyclinones.1b,c The
[3,3] sigmatropic shift (Claisen rearrangement) of allyl
aryl ethers can provide convenient access to ortho-allyl
naphthols.2 Although the Claisen rearrangement pro-
vides an efficient synthetic route for the preparation of
ortho-allyl naphthols, it usually requires high tempera-
tures to proceed.1 These forcing conditions lead to
severe side reactions. Recently, synthetic methodologies
involving rare earth triflates as catalysts for the Claisen
rearrangement have been described.3 High catalytic
activity, low toxicity, moisture, and air tolerance of
lanthanide triflates make them attractive catalysts. How-
ever, the high cost of these catalysts restricts their use.
Clearly, there is a need for the development of new
cheap Lewis acids that can promote the above reaction
in a catalytic way.
ularly attractive because it is commercially available or
can easily be prepared from commercially available
starting materials.14
Herein, we report an attractive method using bis-
muth(III) triflate hydrate (Bi(OTf)3ÆxH2O, 2.5 < x <
4)4b as a catalyst for the Claisen rearrangement of allyl
naphthyl ethers.15 Double rearrangement of di(allyloxy)
naphthalenes is also reported. ortho-Allyl naphthols are
obtained efficiently in the presence of 20 mol %
Bi(OTf)3. Among the various catalyst loadings tested,
20 mol % was found to give the rearrangement to occur
with the best yield.
Initially, the Claisen rearrangement was screened on
differently substituted allyl 1-naphthyl ethers (Table 1).
The naphthol derivatives 1a–i were first allylated
according to the usual procedure (allyl bromide,
Cs2CO3, DMF). The rearrangement occurs with
20 mol % Bi(OTf)3ÆxH2O in a polar coordinating solvent
such as acetonitrile (Scheme 1). The corresponding
ortho-allyl naphthols 3a–g were isolated in moderate to
good yields. Allyl 1-naphthyl ether 2a afforded ortho-
allyl naphthol 3a with a moderate yield (3a, 64%;
deprotected 1-naphthol 1a was also isolated, 4%)
(Table 1, entry 1). With various substituents on the
naphthol ring, the reaction occurred smoothly to give
the corresponding ortho-allyl naphthols 3a–e (Table 1,
entries 1–5). 1,5-Di(allyloxy)naphthalene 2f could
undergo a selective mono Claisen rearrangement to give
compound 3f with moderate yield (Table 1, entry 6).
When a crotyl 1-naphthyl ether was used, a mixture of
[3,3] and [1,3] products 3g and 3g0 was obtained, with
Bismuth compounds have attracted recent attention
due to low toxicity, low cost, and good stability.4
Bismuth(III) salts have been reported as catalysts for
epoxide opening,5 imine allylation,6 Mannich-type reac-
tions,7 Mukaiyama-aldol reactions,8 formation and
deprotection of acetals,9 Friedel–Crafts reactions,10
Fries rearrangement,11 Diels–Alder reactions,12 and
intramolecular Sakurai cyclizations.13 Bi(OTf)3 is partic-
Keywords: Bismuth; Bismuth(III) triflate; Claisen; Rearrangement;
Naphthol; Green chemistry.
*
Corresponding author. Tel.: +1 418 656 5034; fax: +1 418 656
7916; e-mail: thierry.ollevier@chm.ulaval.ca
0040-4039/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2006.03.193

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T. Ollevier, T. M. Mwene-Mbeja / Tetrahedron Letters 47 (2006) 4051–4055
Table 1. Bi(OTf)3 catalyzed ortho-Claisen rearrangement of allyl 1-naphthyl ethers
Entry
1
R1
H
R2
H
R3
H
R4
H
Ta (h)
Compound 3
Yield 3b (%)
OH
24
64
3a
OH
2
3
H
H
4-OMe
H
H
H
H
1
85
57
OMe
3b
OH
4-Cl
40
Cl
3c
OH
4
5
5-OMe
7-OMe
H
H
H
H
H
H
24
40
61
62
OMe
3d
OH
MeO
3e
OH
6
5-OCH2CH@CH2
H
H
H
1.5
40
O
3f
OH
3g
65c
OH
7
H
H
H
Me
6
3g'
(3g/3g': 91/9)
OH
d
8
9
H
H
H
Me
Me
Me
Me
24
18
—
3h
O
4-Cl
80e
Cl
3i'
a Conditions: 20 mol % Bi(OTf)3ÆxH2O, MeCN, 82 °C, [allyl 1-naphthyl ether] = 0.1 M except 0.5 M for entry 6.
b Isolated yield.
1
c Compounds 3g/3g0 ratio was determined by GC and H NMR. Starting material 2g was a 61/39 mixture of stereoisomers. Compound 3g0 was
isolated as a 55/45 mixture of stereoisomers.
d Starting material 2h was recovered.
e Reaction performed with 5 mol % Bi(OTf)3ÆxH2O, PhMe, 0 °C, 4 h, 22 °C, 19 h.

T. Ollevier, T. M. Mwene-Mbeja / Tetrahedron Letters 47 (2006) 4051–4055
4053
R3
R4
Br
R4
OH
R
3
R4
O
OH
R3
Bi(OTf)3•xH2O (20 mol %)
Cs2CO3, DMF
60-100%
R2
R2
R2
R1
R1
R1
1a-i
2a-i
3a-i
Scheme 1.
O
OH
OH
R
R
Br
R
Bi(OTf)3•xH2O (20 mol %)
MeCN, reflux
CsCO3, DMF
74-95%
1j-k
2j-k
3j-k
Scheme 2.
the expected Claisen rearrangement being the main
pathway ([3,3]/[1,3] = 91:9) (Table 1, entry 7). No rear-
rangement was observed with the prenyl ether of 1-
naphthol (2h), and the starting material was recovered
(20 mol % Bi(OTf)3ÆxH2O, MeCN, reflux, 24 h) (Table
1, entry 8). However, the transfer of the allyl group in
a [1,3] fashion was effective with 4-chloro naphthyl pre-
nyl ether and was immediately followed by cyclization
affording 3i0 in a good yield when slightly different con-
ditions were applied (5 mol % Bi(OTf)3ÆxH2O, PhMe,
0 °C, 4 h, 22 °C, 19 h) (Table 1, entry 9). No [3,3] rear-
ranged product was observed in that case. Such a
sequential reaction involving a Claisen rearrangement
followed by cyclization was already reported in a clay
catalyzed rearrangement16 and a Sc(OTf)3 catalyzed
rearrangement in ionic liquids.17
the para-Claisen rearrangement products were obtained
through a sequential ortho-Claisen rearrangement fol-
lowed by a second [3,3] rearrangement.
When the rearrangement took place on 2,4-disubstituted
allyl naphthyl ether 4, only ortho-Claisen rearrangement
could occur to yield 2,2-diallyl-2,3-dihydronaphthalene-
1,4-dione 5, presumably after acidic hydrolysis of the
enol ether functionality (Scheme 3). Such formation of
ortho-diallyl ketones was already reported in a micro-
wave-assisted Claisen rearrangement of allyl naphthyl
ethers.18
The same conditions were applied to various readily
available diallyloxy naphthalenes as the corresponding
doubly rearranged naphthols are known to be attrac-
tive precursors for anthracyclinones (Scheme 4).1b
We hence further studied the scope and limitations of
this reaction with differently 2-substituted allyl 1-naph-
thyl ethers (Scheme 2). Two examples of Bi(OTf)3ÆxH2O
catalyzed Claisen rearrangement are presented in
Table 2. The corresponding para-allyl naphthols 3j and
3k were obtained in good to very good yields with
20 mol % of Bi(OTf)3ÆxH2O in acetonitrile. In such case,
1,4-Di(allyloxy)naphthalene 6 cleanly afforded the
corresponding doubly rearranged product (Scheme 4,
Eq. 1). 2,6-Di(allyloxy)naphthalene 8 reacted more
slowly and a mixture of di- and mono-rearranged prod-
ucts was obtained (1,5-diallylnaphthalene-2,6-diol 9,
38% and 1-allyl-6-(allyloxy)naphthalen-2-ol 10, 46%)
(Scheme 4, Eq. 2). Similarly, Claisen rearrangement
occurred with 1,5-di(allyloxy)naphthalene 2f leading to
a mixture of di- and mono-rearranged products, 11
and 3f, respectively (Scheme 4, Eq. 3). In this latter case,
the conversion was not complete and 25% of the starting
material 2f was recovered. Interestingly, a 0.1 M concen-
tration of starting material was necessary to get the
doubly rearranged product 11, along with 3f, since a
higher concentration (0.5 M) only led to the mono rear-
ranged product 3f (Scheme 1, Table 1).
Table 2. Bi(OTf)3 catalyzed para-Claisen rearrangement of 2-substi-
tuted allyl 1-naphthyl ethers
Entry
R
Ta (h)
Compound 3
Yield 3b (%)
1
2
Me
0.5
19
3j
3k
86
76
a Conditions: 20 mol % Bi(OTf)3ÆxH2O, MeCN, 82 °C.
b Isolated yield.
O
O
OH
Br
Bi(OTf)3•xH2O (20 mol %)
CsCO3, DMF
MeCN, reflux, 19 h
40%
OCH3
O
87%
OCH3
3b
4
5
Scheme 3.

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T. Ollevier, T. M. Mwene-Mbeja / Tetrahedron Letters 47 (2006) 4051–4055
O
O
OH
Bi(OTf)3•xH2O (20 mol%)
Eq.1
Eq.2
Eq.3
MeCN, reflux, 29 h
OH
75%
6
7
OH
O
O
Bi(OTf)3•xH2O (20 mol%)
MeCN, reflux, 22 h
+
HO
O
HO
38%
46%
8
9
10
OH
O
O
Bi(OTf)3•xH2O (20 mol%)
MeCN, reflux, 60 h
+
OH
OH
O
17%
19%
2f
11
3f
Scheme 4.
1569–1575; (c) Kotha, S.; Mandal, K. Tetrahedron Lett.
2004, 45, 2585–2588.
Although the precise mechanism of the bismuth(III)
catalyzed Claisen rearrangement has not been elucidated
yet, we suppose that the reaction happens by formation
of a Bi(III) naphtholate complex. Further investigations
on the mechanism of this transformation are in
progress.
2. For a recent review on the Claisen rearrangement, see:
Castro, A. M. M. Chem. Rev. 2004, 104, 2939–3002.
3. For a review on rare-earth triflates, see: (a) Kobayashi, S.;
Sugiura, M.; Kitagawa, H.; Lam, W. W.-L. Chem. Rev.
2002, 102, 2227–2302; (b) Sharma, G. V. M.; Ilangovan,
A.; Sreenivas, P.; Mahalingam, A. K. Synlett 2000, 615–
618.
4. (a) Organobismuth Chemistry; Suzuki, H., Matano, Y.,
Eds.; Elsevier: Amsterdam, 2001; (b) Gaspard-Ilough-
mane, H.; Le Roux, C. Eur. J. Org. Chem. 2004, 2517–
2532; (c) Leonard, N. M.; Wieland, L. C.; Mohan, R. S.
Tetrahedron 2002, 58, 8373–8397.
5. (a) Ogawa, C.; Azoulay, S.; Kobayashi, S. Heterocycles
2005, 66, 201–206; (b) Ollevier, T.; Lavie-Compin, G.
Tetrahedron Lett. 2004, 45, 49–52; (c) Ollevier, T.; Lavie-
Compin, G. Tetrahedron Lett. 2002, 43, 7891–7893.
6. Ollevier, T.; Ba, T. Tetrahedron Lett. 2003, 44, 9003–9005.
7. (a) Ollevier, T.; Nadeau, E. J. Org. Chem. 2004, 69, 9292–
9295; (b) Ollevier, T.; Nadeau, E. Synlett 2006, 219–222;
(c) Ollevier, T.; Nadeau, E.; Eguillon, J.-C. Org. Lett.,
submitted for publication.
In summary, we found that Bi(OTf)3ÆxH2O is an efficient
catalyst for the Claisen rearrangement of allyl naphthyl
ethers.19 An optimization of the catalyst amount showed
that the reaction works best with a catalyst loading of
20 mol %. The method offers several advantages, includ-
ing mild reaction conditions, use of a green catalyst, and
no formation of decomposition products. Because of its
various benefits, the Bi(OTf)3ÆxH2O protocol should
find utility in the synthesis of biologically active com-
pounds. Development of other Bi(OTf)3ÆxH2O catalyzed
Claisen rearrangements and related mechanistic studies
will be reported in due course.
8. (a) Ollevier, T.; Desyroy, V.; Debailleul, B.; Vaur, S. Eur.
J. Org. Chem. 2005, 4971–4973; (b) Kobayashi, S.; Ogino,
T.; Shimizu, H.; Ishikawa, S.; Hamada, T.; Manabe, K.
Org. Lett. 2005, 7, 4729–4731; (c) Le Roux, C.; Ciliberti,
L.; Laurent-Robert, H.; Laporterie, A.; Dubac, J. Synlett
1998, 1249–1251; (d) Le Roux, C.; Gaspard-Iloughmane,
H.; Dubac, J.; Jaud, J.; Vignaux, P. J. Org. Chem. 1993,
58, 1835–1839; (e) Wada, M.; Takeichi, M.; Matsumoto,
T. Bull. Chem. Soc. Jpn. 1991, 64, 990–994; (f) Ohki, H.;
Wada, M.; Akiba, K. Tetrahedron Lett. 1988, 29, 4719–
4722.
9. (a) Leonard, N. M.; Oswald, M. C.; Freiberg, D. A.;
Nattier, B. A.; Smith, R. C.; Mohan, R. S. J. Org. Chem.
2002, 67, 5202–5207; (b) Carrigan, M. D.; Sarapa, D.;
Smith, R. C.; Wieland, L. C.; Mohan, R. S. J. Org. Chem.
2002, 67, 1027–1030.
Acknowledgments
This work was financially supported by the Natural Sci-
ences and Engineering Research Council of Canada
´ ´
(NSERC, Canada), the Fonds Quebecois de la Recher-
che sur la Nature et les Technologies (FQRNT, Quebec,
Canada), the Canada Foundation for Innovation (CFI),
and Universite Laval. We thank Rhodia (Lyon, France)
for a generous gift of triflic acid and Sidech s.a. (Tilly,
Belgium) for bismuth oxide.
´
´
References and notes
1. (a) Fieser, L. F.; Campbell, W. P.; Fry, E. M. J. Am.
Chem. Soc. 1939, 61, 2206–2218; (b) Takahashi, I.;
Nomura, A.; Kitajima, H. Synth. Commun. 1990, 20,
10. (a) Le Roux, C.; Dubac, J. Synlett 2002, 181–200; (b)
`
Desmurs, J. R.; Labrouillere, M.; Le Roux, C.; Gaspard,
H.; Laporterie, A.; Dubac, J. Tetrahedron Lett. 1997, 38,

T. Ollevier, T. M. Mwene-Mbeja / Tetrahedron Letters 47 (2006) 4051–4055
4055
´
8871–8874; (c) Repichet, S.; Le Roux, C.; Dubac, J.;
magnetically stirred and heated at 82 °C for 1–40 h. The
reaction mixture was cooled to room temperature, evap-
orated, and, after addition of water, extracted with ethyl
acetate, dried over anhydrous sodium sulfate, filtered, and
concentrated under vacuum (rotary evaporator). The
residue was purified by column chromatography on silica
gel using hexanes/ethyl acetate (93/7–90/10) as eluent.
All the compounds were characterized by IR and 1H
NMR, and accord exactly with those previously
reported in the literature. The spectral data for com-
pounds 3a–b, 3d, 3g–g0, 7, 9, and 11 accord exactly those
reported in the literature.1a,b,3b,20–24
Desmurs, J. R. Eur. J. Org. Chem. 1998, 2743–2746.
11. (a) Ollevier, T.; Desyroy, V.; Asim, M.; Brochu, M.-C.
Synlett 2004, 2794–2796; (b) Sreedhar, B.; Swapna, V.;
Sridhar, C. Synth. Commun. 2004, 34, 1433–1440.
12. (a) Garrigues, B.; Oussaid, A. J. Organomet. Chem. 1999,
585, 253–255; (b) Laurent-Robert, H.; Garrigues, B.;
Dubac, J. Synlett 2000, 1160–1162.
´
13. (a) Leroy, B.; Marko, I. E. Org. Lett. 2002, 4, 47–50; (b)
´
Leroy, B.; Marko, I. E. Tetrahedron Lett. 2001, 42, 8685–
8688.
´
14. (a) Repichet, S.; Zwick, A.; Vendier, L.; Le Roux, C.;
Dubac, J. Tetrahedron Lett. 2002, 43, 993–995; (b)
2-Allyl-4-chloro-naphthalen-1-ol (3c). Reagents: 1-allyloxy-
4-chloronaphthalene (400 mg, 1.82 mmol) and Bi(OTf)3Æ
xH2O (260 mg, 0.36 mmol). The reaction was stirred for
40 h and quenched according to the typical procedure. The
crude product was purified by column chromatography on
silica gel to afford 260 mg (57%) of 3c as a reddish
solid; mp 48–50 °C; Rf 0.31 (hexane/ethyl acetate = 93:7);
IR (KBr): m = 3511 (br), 3081, 2920, 2865, 1622, 1596,
1571, 1505, 1458, 1426, 1264, 1229, 909, 763; 1H NMR
(CDCl3): d = 8.18 (2H, m), 7.45 (2H, m), 7.32 (1H, s), 6.04
(1H, m), 5.55 (1H, s), 5.20–5.40 (2H, m), 3.55 (2H, d,
J = 2.3 Hz); 13C NMR (CDCl3): d = 145.1, 131.7, 126.8,
124.4, 123.1, 122.3, 122.2, 120.5, 119.4, 113.9, 110.0, 31.8;
HRMS: calcd for C13H11ClO (M+) 218.0498, found
218.0503.
`
Labrouillere, M.; Le Roux, C.; Gaspard, H.; Laporterie,
A.; Dubac, J.; Desmurs, J. R. Tetrahedron Lett. 1999, 40,
285–286; (c) Peyronneau, M.; Arrondo, C.; Vendier, L.;
Roques, N.; Le Roux, C. J. Mol. Cat. A 2004, 211, 89–91;
(d) Bi(OTf)3ÆxH2O has been prepared from Bi2O3 accord-
ing to Ref. 14a.
15. A Bi(OTf)3 screening for the catalytic Claisen rearrange-
ment of substituted allyl phenyl ethers was independently
studied by Sreedhar.11b However, the rearrangement of
1-(allyloxy)-4-methylbenzene using 5 mol % anhydrous
Bi(OTf)3 performed in Sreedhar’s conditions never affor-
ded reproducible yields in our hands (less than 20%
conversion with extended reaction times).
16. Dauben, W. G.; Cogen, J. M.; Behar, V. Tetrahedron Lett.
1990, 31, 3241–3244.
´
20. Wipf, P.; Rodrıguez, S. Adv. Synth. Catal. 2002, 344, 434–
17. Zulfiqar, F.; Kitazume, T. Green Chem. 2000, 2, 296–297.
18. Kotha, S.; Mandal, K.; Chandra Deb, A.; Banerjee, S.
Tetrahedron Lett. 2004, 45, 9603–9605.
440.
21. Bundy, G. L.; Lin, C.-H. PCT Int. Appl. WO 87/01698,
1987.
19. Typical procedure for the Bi(OTf)3ÆxH2O catalyzed Claisen
rearrangement of naphthyl allyl ethers 2a–k, 4, 6, and 8.
Under an inert atmosphere of argon, to a solution of allyl
naphthyl ether 2 (1 mmol) in acetonitrile (10 mL) was
added Bi(OTf)3ÆxH2O (0.20 mmol). The mixture was
22. Krohn, K.; Bernhard, S. Synthesis 1996, 699–701.
23. Sharma, G. V. M.; Ilangovam, A.; Sreenivas, P.; Maha-
lingam, A. K. Synlett 2000, 615–618.
24. Tada, Y.; Satake, A.; Shimizu, I.; Yamamoto, A. Chem.
Lett. 1996, 1021–1022.