Bismuth triflate catalyzed [1,3] rearrangement of aryl 3-methylbut-2-enyl ethers

Article abstract of DOI:10.1055/s-2006-950326

An efficient bismuth triflate catalyzed [1,3] rearrangement of aryl 3-methylbut-2-enyl ethers has been developed. The reaction proceeds rapidly and affords the corresponding para- and ortho-prenylated phenols and naphthols in moderate to good yields (up t

Full text of DOI:10.1055/s-2006-950326

PAPER
3963
Bismuth Triflate Catalyzed [1,3] Rearrangement of Aryl 3-Methylbut-2-enyl
Ethers
B
i(OTf) -Cataly
h
ze
d
[1,3]
R
e
i
arrange
e
ment of
A
r
r
yl 3-Me
r
thylbut-2
y
-enyl Ethers Ollevier,* Topwe M. Mwene-Mbeja
2
Département de Chimie, Université Laval, Québec, PQ, G1K 7P4, Canada
Fax +1(418)6567916; E-mail: thierry.ollevier@chm.ulaval.ca
Received 18 July 2006
muth compounds have attracted recent attention due to
Abstract: An efficient bismuth triflate catalyzed [1,3] rearrange-
ment of aryl 3-methylbut-2-enyl ethers has been developed. The re-
action proceeds rapidly and affords the corresponding para- and
ortho-prenylated phenols and naphthols in moderate to good yields
their low toxicity, low cost, and good stability.5 Bismuth
salts have been reported as catalysts for opening of ep-
oxides,6 Mukaiyama aldol and Mannich-type reactions,7
(up to 86%). ortho-Prenylphenols are immediately cyclized under formation of acetals,8 Sakurai reactions,9 Friedel–Crafts
reactions and Fries rearrangements.10 Bi(OTf)3 is particu-
the reaction conditions to the corresponding chroman derivatives.
larly attractive because it is commercially available or can
be easily prepared from readily available starting materi-
als.11
Key words: bismuth, bismuth triflate, [1,3] rearrangement, Lewis
acid, allyl phenyl ethers
We recently reported the bismuth(III)-catalyzed [3,3] re-
arrangement (Claisen rearrangement) of allyl 1-naphthyl
ethers.12 When a crotyl 1-naphthyl ether was used, a mix-
ture of [3,3] and [1,3] products was obtained, with the ex-
pected Claisen rearrangement being the major pathway.
The general effectiveness of Bi(OTf)3 as a Lewis acid
brought us to study the desired [1,3] shift. We found that
[1,3] rearrangement of substituted 3-methylbut-2-enyl
naphthyl ethers was efficiently catalyzed by
Bi(OTf)3·4H2O in mild conditions. Both ortho- and para-
prenylated naphthols and phenols are readily obtained in
the presence of 5 mol% of Bi(OTf)3. Among various cat-
alyst loadings tested, 5 mol% of Bi(OTf)3 was found to
give the rearranged products with the best yield. Under
our conditions, the corresponding Claisen [3,3] rearrange-
ment was never observed.
The [3,3] sigmatropic shift (Claisen rearrangement) of al-
lyl aryl ethers provides a convenient access to ortho-allyl
phenols and naphthols,1 which are versatile intermediates
in the synthesis of biologically active compounds such as
1,4-naphthoquinones and anthracyclinones.2 The difficul-
ty in preparing 2,2-disubstituted ethers such as 1¢ renders
the Claisen rearrangement inconvenient for the prepara-
tion of terminally substituted ortho-allylphenols 2. A mild
and convenient method for the [1,3] rearrangement of
ether 1 is therefore desirable as an alternative to the Clais-
en rearrangement (Equation 1).
Although the [1,3] rearrangement provides an efficient
synthetic route for the preparation of ortho- or para-pre-
nylated phenols along with chroman derivatives 3, it usu-
ally requires high temperatures to proceed.3 These forcing
conditions lead to severe side reactions. Recently, syn-
thetic methods involving Al(III) derivatives, lanthanide
triflates, and clays as catalysts for the [1,3] sigmatropic re-
arrangement of allyl aryl ethers have been reported.4 Bis-
Initially, we screened the [1,3] rearrangement on differ-
ently 2- and 4-substituted allyl 1-naphthyl ethers
(Table 1). The substituted 1-naphthyl prenyl ethers 5a–d
were first prepared according to the usual procedure (pre-
OH
O
O
OH
O
2
∆
3
∆
OH
+
[1,3]
[3,3]
1'
2
1
4
Equation 1
SYNTHESIS 2006, No. 23, pp 3963–3966
x
x.
x
x
.
2
0
0
6
Advanced online publication: 20.10.2006
DOI: 10.1055/s-2006-950326; Art ID: M04706SS
© Georg Thieme Verlag Stuttgart · New York

3964
T. Ollevier, T. M. Mwene-Mbeja
PAPER
O
OH
O
OH
Bi(OTf)3⋅4H2O (5 mol%)
PhMe, 0–22 °C
+
+
R1
R1
R1
R1
5a–d
6a–d
7a–d
8a–d
Scheme 1
nyl bromide, Cs2CO3, DMF, 22 °C). The rearrangement yields to give chroman derivatives 3 (Table 2, entries c–
occurs with 5 mol% Bi(OTf)3·4H2O in an apolar solvent f). The rearrangement occurred in the presence of either
such as toluene (Scheme 1). The ortho- and para-substi- an ester or a ketone functionality (Table 2, entries f and g).
tuted naphthol derivatives 6 and 8, along with the corre-
sponding chroman derivatives 7 were isolated in moderate
to good yields. 1-Naphthyl prenyl ether 5a afforded ortho-
O
O
OH
prenylnaphthol (6a) in a moderate yield (72%) (Table 1,
entry a). Whatever the substitution of the naphthol ring,
the reaction occurred smoothly to give the corresponding
ortho- or para-prenylnaphthols 6 or 8 (Table 1, entries a–
c). With ortho-substituted 1-naphthyl prenyl ethers, the
[1,3] rearrangement afforded the corresponding para-pre-
nylnaphthols 8b (Table 1, entry b). 1-(3-Methylbut-2-
enyloxy)-4-methoxynaphthalene (5c) was smoothly rear-
ranged into the ortho isomer 6c (Table 1, entry c). The
transfer of the allyl group in a [1,3] fashion was also effec-
tive with the 4-chloronaphthyl prenyl ether and was im-
mediately followed by a cyclization reaction affording 7d
in a good yield (Table 1, entry d). Such a sequential reac-
tion involving a [1,3] rearrangement and a cationic cy-
clization reaction has already been reported in a clay-
catalyzed rearrangement.4d,e
Bi(OTf)3⋅4H2O (5 mol%)
+
PhMe, 0–22 °C
R1,R2,R3
1a–g
R1,R2,R3
R1,R2,R3
3a–g
4a–g
Scheme 2
It is likely that the reaction conditions promote formation
of a discrete, delocalized prenyl carbocation and bismuth
aryloxide, which recombine to give the desired product.
Detailed investigations on the mechanism of this transfor-
mation are in progress.
In summary, we have found that Bi(OTf)3·4H2O is an ef-
ficient catalyst for the [1,3] rearrangement of aryl prenyl
ethers. The method offers several advantages including
mild reaction conditions, use of an environmentally be-
nign catalyst, and no formation of by-products.
From thereon, we further studied the scope and limitations
of this reaction with differently substituted 3-methylbut-
2-enyl phenyl ethers 1 (Scheme 2). The corresponding
para-prenylphenols 4 were obtained in moderate to good
yield with 5 mol% of Bi(OTf)3·4H2O in toluene (Table 2,
entries a, b, and g). With para-substituted substrates, the
[1,3] rearrangement immediately followed by a subse- 1H NMR spectra were recorded on a 400 MHz (100 MHz for 13C
NMR) magnetic resonance spectrometer in CDCl3. Column chro-
quent cationic cyclization occurred in moderate to good
matography was performed on silica gel (230–400 mesh) and ana-
lytical TLC was carried out using 250 mm commercial silica gel
Table 1 Bi(OTf)3-Catalyzed [1,3] Rearrangement of 3-Methylbut-
2-enyl 1-Naphthyl Ethers 5
plates. All glassware was stored in the oven and flame-dried prior
to use under an inert atmosphere of argon. Toluene was distilled
from sodium. Aryl 3-methylbut-2-enyl ethers 1 and 5 were synthe-
sized according to known literature procedures.13
Entry R1
Time
(h)a
Yield 6
Yield 7
Yield 8
(%)b
(%)b
(%)b
Bismuth Triflate-Catalyzed [1,3] Rearrangement of Aryl 3-
Methylbut-2-enyl Ethers 1 and 5; General Procedure
a
b
c
H
4.5
72 (6a)
–
–
To a solution of aryl 3-methylbut-2-enyl ether 1 or 5 (1 mmol) in
toluene (10 mL) at 0 °C was added Bi(OTf)3·4H2O (0.05 mmol).
The mixture was magnetically stirred at 0 °C for 2 h, allowed to
reach r.t., and then stirred at this temperature for 2.5–21 h. After ad-
dition of H2O, the mixture was extracted with EtOAc, washed with
H2O, dried (Na2SO4), filtered, and concentrated under vacuum (ro-
tatory evaporator). The residue was purified by column chromatog-
raphy on silica gel using hexanes–EtOAc (93:7–90:10) as eluent.
Products 3e,14a 3f,14b 3g,14c 4a,4e 4b,14d 4e,4d 4g,14e 6a,14f 7d,12 and
8b14g accord exactly with those previously reported in the literature.
2-COMe 10
–
–
52 (8b)
4-OMe
4-Cl
19
23
86 (6c)
–
–
–
d
–
80 (7d)
a Conditions: 5 mol% Bi(OTf)3·4H2O, PhMe, 0 °C, 2 h, then 22 °C,
2.5–21 h.
b Isolated yield.
Synthesis 2006, No. 23, 3963–3966 © Thieme Stuttgart · New York

PAPER
Bi(OTf)2-Catalyzed [1,3] Rearrangement of Aryl 3-Methylbut-2-enyl Ethers
3965
Table 2 Bi(OTf)3-Catalyzed [1,3] Rearrangement of Various Substituted 3-Methylbut-2-enyl 1-Phenyl Ethers 1
Entry
1
Time (h)a
12
Major product
Yield 3 (%)b
Yield 4 (%)b
64 (4a)
OH
a
–
O
b
c
17
18
–
65 (4b)
OH
O
O
80 (3c)
–
O
d
14
78 (3d)
–
O
O
e
12
16
14
76 (3e)
80 (3f)
11 (3g)
3 (4e)
O
O
OCH3
O
OCH3
O
f
–
CO2Et
CO2Et
O
g
68 (4g)
O
OH
O
a Conditions: 5 mol% Bi(OTf)3·4H2O, PhMe, 0 °C, 2 h, then 22 °C, 10–16 h.
b Isolated yield.
4-Methoxy-2-(3-methylbut-2-enyl)naphthalen-1-ol (6c)
Yield: 86%.
(m, 2H), 3.90 (s, 3 H), 3.50 (d, J = 7.2 Hz, 2 H), 1.78 (s, 3 H), 1.76
(s, 3 H).
IR (film): 3381, 3069, 2974, 2934, 2854, 1661, 1596, 1450, 1378
cm–1.
13C NMR (100 MHz, CDCl3): d = 147.9, 147.0, 133.1, 130.1, 129.0,
126.7, 124.9, 124.3, 123.0, 122.1, 110.3, 62.3, 28.4, 26.0, 18.2.
1H NMR (400 MHz, CDCl3): d = 8.13 (d, J = 8.3 Hz, 1 H), 8.05 (d,
J = 8.4 Hz, 1 H), 7.53 (m, 1 H), 7.45 (m, 1 H), 6.64 (s, 1 H), 5.30
Anal. Calcd for C16H18O2: C, 79.31; H, 7.49; O, 13.21. Found: C,
78.93; H, 7.69; O, 12.87.
Synthesis 2006, No. 23, 3963–3966 © Thieme Stuttgart · New York

3966
T. Ollevier, T. M. Mwene-Mbeja
PAPER
2,2,6,8-Tetramethylchroman (3c)
Yield: 80%.
IR (film): 3004, 2975, 2925, 2852, 1481, 1449, 1382, 1368 cm–1.
1H NMR (400 MHz, CDCl3): d = 6.80 (s, 1 H), 6.74 (s, 1 H), 2.72
(t, J = 6.8 Hz, 2 H), 2.24 (s, 3 H), 2.15 (s, 3 H), 1.78 (t, J = 6.8 Hz,
2 H), 1.33 (s, 6 H).
13C NMR (100 MHz, CDCl3): d = 150.2, 129.4, 128.1, 126.3, 120.2,
73.9, 33.4, 33.2, 27.3, 22.9, 20.8, 20.7, 6.3.
(4) Aluminum(III) derivatives: (a) Wipf, P.; Rodriguez, S. Adv.
Synth. Catal. 2002, 344, 434. (b) Maruoka, K.; Sato, J.;
Banno, H.; Yamamoto, H. Tetrahedron Lett. 1990, 31, 377.
Lanthanides salts: (c) Sharma, G. V. M.; Ilangovan, A.;
Sreenivas, P.; Mahalingam, A. K. Synlett 2000, 615.
Clays: (d) Dauben, W. G.; Cogen, J. M.; Behar, V.
Tetrahedron Lett. 1990, 31, 3241. (e) Dintzner, M. R.;
Morse, K. M.; McClelland, K. M.; Coligado, D. M.
Tetrahedron Lett. 2004, 45, 79.
(5) (a) Organobismuth Chemistry; Suzuki, H.; Matano, Y., Eds.;
Elsevier: Amsterdam, 2001. (b) Gaspard-Iloughmane, H.;
Le Roux, C. Eur. J. Org. Chem. 2004, 2517. (c) Leonard,
N. M.; Wieland, L. C.; Mohan, R. S. Tetrahedron 2002, 58,
8373.
(6) (a) Ogawa, C.; Azoulay, S.; Kobayashi, S. Heterocycles
2005, 66, 201. (b) Ollevier, T.; Lavie-Compin, G.
Tetrahedron Lett. 2004, 45, 49. (c) Ollevier, T.; Lavie-
Compin, G. Tetrahedron Lett. 2002, 43, 7891.
(7) (a) Ollevier, T.; Nadeau, E. Synlett 2006, 219. (b) Ollevier,
T.; Desyroy, V.; Debailleul, B.; Vaur, S. Eur. J. Org. Chem.
2005, 4971. (c) Kobayashi, S.; Ogino, T.; Shimizu, H.;
Ishikawa, S.; Hamada, T.; Manabe, K. Org. Lett. 2005, 7,
4729. (d) Ollevier, T.; Nadeau, E. J. Org. Chem. 2004, 69,
9292. (e) Le Roux, C.; Ciliberti, L.; Laurent-Robert, H.;
Laporterie, A.; Dubac, J. Synlett 1998, 1249. (f) Ollevier,
T.; Nadeau, E.; Eguillon, J.-C. Adv. Synth. Catal. 2006, 348,
2080. (g) Ollevier, T.; Desyroy, V.; Nadeau, E. ARKIVOC,
2007, accepted
(8) Leonard, N. M.; Oswald, M. C.; Freiberg, D. A.; Nattier, B.
A.; Smith, R. C.; Mohan, R. S. J. Org. Chem. 2002, 67, 5202.
(9) Ollevier, T.; Ba, T. Tetrahedron Lett. 2003, 44, 9003.
(10) (a) Le Roux, C.; Dubac, J. Synlett 2002, 181. (b) Ollevier,
T.; Desyroy, V.; Asim, M.; Brochu, M.-C. Synlett 2004,
2794.
Anal. Calcd for C13H18O: C, 82.06; H, 9.53; O, 8.41. Found: C,
81.70; H, 9.72; O, 8.04.
6-tert-2,2-Dimethylchroman (3d)
Yield: 78%.
IR (film): 2963, 2869, 1498, 1481, 1462 cm–1.
1H NMR (400 MHz, CDCl3): d = 7.10 (d, J = 8.6 Hz, 1 H), 7.03 (s,
1 H), 6.69 (d, J = 8.6 Hz, 1 H), 2.77 (t, J = 6.8 Hz, 2 H), 1.78 (t,
J = 6.8 Hz, 2 H), 1.20–1.30 (m, 15 H).
13C NMR (100 MHz, CDCl3): d = 151.9, 142.4, 126.4, 124.6, 120.2,
116.8, 74.2, 34.2, 33.2, 31.9, 27.5, 23.2.
Anal. Calcd for C15H22O: C, 82.52; H, 10.16; O, 7.33. Found: C,
82.25; H, 10.50; O, 6.98.
Acknowledgment
This work was financially supported by the Natural Sciences and
Engineering Research Council of Canada (NSERC), the Fonds
Québécois de la Recherche sur la Nature et les Technologies
(FQRNT, Québec, Canada), the Canada Foundation for Innovation,
and Université Laval. We thank Rhodia (Lyon, France) and Sidech
s.a. (Tilly, Belgium) for generous gift of chemicals.
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Dubac, J. Tetrahedron Lett. 2002, 43, 993. (b) Labrouillère,
M.; Le Roux, C.; Gaspard, H.; Laporterie, A.; Dubac, J.;
Desmurs, J. R. Tetrahedron Lett. 1999, 40, 285.
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Synthesis 2006, No. 23, 3963–3966 © Thieme Stuttgart · New York