A first homogeneous gold(III)-catalysed epoxidation of aromatic alkenes

Article abstract of DOI:10.3184/030823407X275937

The first example of a homogeneous gold(III)-catalysed epoxidation of aromatic alkenes at room temperature using sodium chlorite as the stoichiometric oxidant in a homogeneous trisolvent system of 2-methoxyethanol/acetonitrile/ water (volume ratio: 1/3/1)

Full text of DOI:10.3184/030823407X275937

722 RESEARCH PAPER
DECEMBER, 722–724
JOURNAL OF CHEMICAL RESEARCH 2007
A first homogeneous gold(III)-catalysed epoxidation of aromatic alkenes
Xiao-Qiang Li, Chen Li, Fan-Bo Song and Chi Zhang*
The State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, P. R. China
The first example of a homogeneous gold(III)-catalysed epoxidation of aromatic alkenes at room temperature using
sodium chlorite as the stoichiometric oxidant in a homogeneous trisolvent system of 2-methoxyethanol/acetonitrile/
water (volume ratio: 1/3/1) is reported. A radical-trapping experiment suggested that the reaction might proceed via
a radical pathway.
Key words: alkenes, epoxidations, homogeneous catalysis, gold, sodium chlorite
Homogeneous cationic gold-catalysed organic transformations
have been a focus of attention in recent years due to their
novelty and high efficiency.1 In most cases, cationic gold
acts as a soft Lewis acid to activate alkynes and allenes
towards either carbon-carbon bond or carbon-heteroatom
bond formation. Owing to the lower electron density in
a carbon–carbon double bond,1b reports concerning the
activation of alkenes have been limited and only appeared
quite recently with the nucleophilic addition of phenols,2,3
active methylene compounds,4 and alcohols5 to unactivated
alkenes. Homogeneous gold-catalysed oxidation reactions
have attracted interest as well,1a including oxidation of
sulfides to sulfoxides,6 alcohols to carbonyl compounds,7
methane to methanol,8 alkanes to alkyl hydroperoxides9 and
the Baeyer–Villiger oxidation of ketones.10 Moreover, the
homogeneous gold-catalysed oxidation of alkenes such as
the nitrene transfer reaction11 and the oxidative cleavage of a
C–C double bond12 have also been studied. To the best of our
knowledge, the homogeneous epoxidation of alkenes using a
simple gold salt as a catalyst,13 has not been reported. Hence,
we report the first example of a homogeneous gold(III)-
catalysed epoxidation of aromatic alkenes with sodium chlorite
(NaClO2) as the stoichiometric oxidant in a trisolvent system
of CH3OCH2CH2OH/CH3CN/H2O at room temperature.
Initially, the epoxidation reaction of trans-stilbene was
tested using gold trichloride as a catalyst and sodium
chlorite14 as an oxidant in CH3CN/H2O (4/1, v/v). This
reaction provided trans-stilbene oxide in 42% yield at room
temperature (Table 1, entry 1).15 However, the background
reaction (without AuCl3) also gave the trans-stilbene oxide in
35% yield. In order to increase the catalytic activity of AuCl3,
various types of ligands including N,N-bidentate ligands such
as neocuprione; N,O-mixed tetracoordinating ligands such
as N,N'-bis(salicylidene)-1,2-phenylenediamine and the O,
O-bidentate ligand, acetylacetone (acac) were tried. Of these,
only acac was successful (Table 1, entry 2 vs entry 1).16 With
this in mind, six oxygen-containing organic solvents were
screened as a third solvent along with CH3CN/H2O without
the use of any ligands (entries 3-8). It was observed that the
use of CH3OCH2CH2OH/CH3CN/H2O (volume ratio: 1/3/1)
as the solvent system gave the best result, with conversion
of trans-stilbene being 91% and the isolated yield of trans-
stilbene oxide being 81% (entry 4). Noticeably, there was no
background epoxidation reaction in this trisolvent system. This
was distinct from the CH3CN/H2O bisolvent system where
background reaction occurred to a great extent. The catalytic
activity of gold trichloride in the epoxidation of trans-stilbene
in this trisolvent system was evident. 1,2-Dimethoxyethane,
ethanol and i-propanol were inferior solvent components to
2-methoxyethanol (entries 3, 6 and 7). Though the same yield
of trans-stilbene oxide was obtained in a trisolvent of t-BuOH/
CH3CN/H2O as that in CH3OCH2CH2OH/CH3CN/H2O
(entry 4 vs. 8), only 14% epoxide yield was produced for the
Table 1 Optimisation of reaction componentsa
Entry
Ligand or the
third solvent
Yield/%b
Conversion
/%
1
2
3
4
5
6
7
8
None
42
66
59
81
–
34
51
81
47
acacc
84
DMEd
66
CH3OCH2CH2OHe
HOCH2CH2OHe
EtOHe
91
no reaction
43
61
86
i-PrOHe
t-BuOHe
aUnless otherwise indicated, the reaction was conducted
with 1 mmol of trans-stilbene, 5 mol% of AuCl3, 3 mmol of
NaClO2 in the bisolvent of CH3CN (12 ml) and H2O (3 ml) at
room temperature for 24 hours. bIsolated yields. 20 mol% of
c
acac was added into the reaction system illustrated in note a.
d3 ml of DME was added into the reaction system illustrated in
note a, correspondingly, volume of CH3CN was reduced to 9 ml
from 12 ml and volume of H2O kept unchanged. No ligand was
e
used. All other parameters were identical to those of entry 3
except that 3 ml of alcohol was employed instead of DME.
Table 2 Screened gold catalystsa
Entry
Gold catalyst
Yield/%
1b
(PPh3)AuCl
(PPh3)AuCl/AgOTf
< 5
< 5
2b,c
O
N
3d
4d
80
81
Au
Cl Cl
AuCl3
O
AuCl3
aReaction conditions: 0.5 mmol of trans-stilbene, 0.025 mmol
of gold catalyst, and 1.5 mmol of NaClO2 in a trisolvent of
CH3OCH2CH2OH (1.5 ml), CH3CN (4.5 ml), and H2O (1.5 ml).
b95% of trans-stilbene was recovered. cMolar ratio of (PPh3)AuCl
to AgOTf was 1:1. dThe conversion of trans-stilbene was 91%.
epoxidationoftrans-4-chlorostilbeneint-BuOH/CH3CN/H2O.
Consequently, the trisolvent of CH3OCH2CH2OH/CH3CN/
H2O was the choice of solvent for further optimisation.
Other gold(I) and gold(III) complexes were screened with
results summarised in Table 2. Chloro(triphenylphosphine)
gold(I)17 has no catalytic activity since more than 95% of the
starting material was recovered, and its catalytic activity did not
improve on the addition of AgOTf (Table 2, entries 1 and 2).
Dichloro(pyridine-2-carboxylato)gold(III)18 showed equal
catalytic activity to AuCl3 when trans-stilbene was used as the
substrate (entries 3 and 4). However, in the case of trans-4-
chlorostilbene, AuCl3 was more reactive since yields of the
corresponding epoxide using AuCl3 and dichloro(pyridine-
2-carboxylato)gold(III) were 87% and 76%, respectively.
Therefore, the optimal reaction system was composed of
5 mol% AuCl3, 3 equivalents of sodium chlorite, and a
trisolventCH3OCH2CH2OH/CH3CN/H2O(1/3/1,volumeratio)
* Correspondent. E-mail: zhangchi@nanai.edu.cn
PAPER: 07/4851

JOURNAL OF CHEMICAL RESEARCH 2007 723
a
Ph
Ph
AuCl3 (5 mol %), NaClO2 (3eq)
MeOCH2CH2OH (1.5 mL)
Table 3 Epoxidation of olefins catalysed by AuCl3
Entry
Olefin
Yield
/%b
Conversion
/%
Ph
0.5 mmol
O
Ph
CH3CN (4.5 mL), H2O (1.5 mL)
24 h, rt
81 %
1
2
trans-Stilbene
81
35c
92
87
76
56
50
55
50
62
56f
58g
37
91
39
97
91
85
58
70
92
90
84
71
100
100
cis-Stilbene
Scheme 1 Optimal epoxidation system of trans-stilbene.
3
trans-4-Fluorostilbene
trans-4-Chlorostilbene
trans-4-Bhlorostilbene
trans-4-Bromostilbene
trans-4-Cyanostilbene
trans-4-Methylstilbene
trans-4,4’-Dimethylstilbene
Triphenylethylene
4
5d
6
(see Scheme 1). Under the optimal conditions, there was no
precipitate of metallic gold during the course of the reaction,
which supports a homogeneous gold-catalysed epoxidation
reaction.
7e
8
9
Various olefins were tested using this homogeneous gold-
catalysed epoxidation reaction. The reaction of cis-stilbene
was much slower than trans-stilbene as only 39% of cis-
stilbene was transformed to give trans-stilbene oxide as the
major epoxidation product (ratio of trans- to cis-stilbene oxide:
20/1) after 48 h (Table 3, entry 2). The nonstereospecificity
of the epoxidation reaction implied that the reaction proceeds
stepwise. As for mono para-halogen substituted trans-
stilbenes, the yields of the corresponding epoxides decreased
from excellent to poor in the order of F > Cl > Br (entries
3, 4, 6). Different solubility observed in experiments among
these three halogen-substituted trans-stilbenes might account
for the observed yield order. A trisubstituted aromatic
olefin, triphenylethylene gave triphenylethylene oxide in
62% yield (entry 10). When trans-α-methyl stilbene and
1-phenylcyclohexene were tested, however, the oxidation
products obtained were 2,2-phenyl propanal and
α-phenylcyclopentanecarboxaldehyde, which derived from the
rearrangement of two epoxides intermediates, trans-α-methyl
stilbene oxide and 1-phenylcyclohexene oxide respectively.19
A control experiment showed that trans-α-methyl stilbene
oxide readily rearranged to 2,2-phenylpropanal in quantitative
yield in the presence of 5 mol% AuCl3 in dichloromethane
at room temperature within 30 min. 1,2-Dialkyl-substituted
alkenes and terminal olefins were poor substrates under the
standard conditions. During the study of substrate scope, it was
observed that metallic gold precipitated after several minutes
if the epoxidation reaction proceeded poorly, whereas, if the
epoxidation reaction went on well, there was no precipitated
metallic gold until the completion of the reaction.
A preliminary study has been done to probe the mechanism
of the present AuCl3-catalysed epoxidation reaction. The fact
that cis-stilbene yielded trans-stilbene oxide as the major
epoxidation product implied that free radical species might be
involved in the reaction. This was the case since the addition of
20 mol% of 2,2,6,6-tetramethylpiperidin-1-yloxy (TEMPO),
a widely used radical scavenger, inhibited the epoxidation
reaction dramatically, with conversion of trans-stilbene being
only 22% after 30 h.
In summary, the first homogeneous gold(III)-catalysed
epoxidation of aromatic olefins has been developed. A novel
redox catalytic reactivity of cationic gold(III) has been
discovered. Further studies to understand the mechanism and
develop a gold-catalysed enantioselective epoxidation reaction
are underway.
10
11
12
13
trans-a-Methylstilbene
1-Phenylcyclohexene
b-Methylstyrene
aUnless otherwise noted, reactions were conducted under
the standard conditions shown in Scheme 1. bIsolated
yields. ctrans/cis-stilbene oxide
= 20:1, determined by
1H NMR. d5 mol% of dichloro(pyridine-2-carboxylato)gold(III)
was used as the catalyst instead of AuCl3. eReaction time
was 48 h. The yield of 2,2-phenyl propanal. gThe yield of
f
a-phenylcyclopentanecarboxaldehyde.
was added sodium chlorite (170 mg, 1.5 mmol, 80% purity) at room
temperature. The reaction mixture turned to yellow immediately.
After 24 h, the reaction was quenched by the addition of saturated
aqueous Na2S2O3 solution (15 ml), and the mixture was extracted
with EtOAc (30 ml × 3). The combined organic layers were washed
with water (10 ml) and brine (10 ml) once, dried over anhydrous
Na2SO4, filtered, and concentrated under reduced pressure.
The residue was purified by flash column chromatography
(2% EtOAc in petroleum ether) on silica gel to give trans-stilbene
oxide14 (159 mg, 81%) as a white solid: m.p. 66–67°C (lit.14 63–65°C.
1H NMR (400 MHz, CDCl3) δ 7.42–7.37 (m, 10H), 3.88 (s, 2H); 13
C
NMR (100 MHz, CDCl3) δ 137.07, 128.53, 128.29, 125.47, 62.80.
IR (KBr) 1452, 1278, 860, 837, 745, 690 cm-1; EI-MS (M+): 196.
Oxidation of 1-phenylcyclohexene
1-Phenylcyclohexene was treated with the above procedure,
except that flash column chromatography was conducted with
1% EtOAc in petroleum ether on silica gel, giving 50 mg
α-phenylcyclopentanecarboxaldehyde20 in 58% yield as a colourless
1
oil. H NMR (400 MHz, CDCl3) δ 9.30 (s, 1H), 7.28–7.16 (m, 5H),
2.47–2.41 (m, 2H), 1.83–1.54 (m, 6H); 13C NMR (100 MHz, CDCl3)
δ 200.59, 140.20, 128.67, 127.58, 127.08, 63.61, 32.24, 24.13.
IR(KBr) 3036, 2805, 2715, 2212, 1720 1587, 1488, 754, 659 cm-1.
ESI-MS (M+): 174.
trans-4-Fluorostilbene oxide (Table 3, entry 3)
M.p. 75–76°C (lit.21 76–77°C). 1H NMR (400 MHz, CDCl3)
d 7.38–7.04 (m, 9H), 3.85 (d, J = 2.4 Hz, 1H), 3.83 (d, J = 2.4 Hz,
1H); 13C NMR (100 MHz, CDCl3) d 163.72 (d, J = 244.9 Hz), 136.82,
132.81, 128.55, 128.37, 127.14 (d, J = 8.2 Hz), 125.44, 115.55 (d,
J = 21.5 Hz), 62.76, 62.18. IR(KBr) 3062, 3033, 2987, 1602, 1509,
1459, 1430, 1234, 1093, 829, 775, 738, 694, 563, 520 cm-1. ESI-MS
(M+): 214.
trans-4-Chlorostilbene oxide (Table 3, entry 4)
M.p. 99–100°C (lit.21 100.4–101.5°C). H NMR (400 MHz, CDCl3)
1
d 7.35–7.26 (m, 9H), 3.85 (d, J = 2.4 Hz, 1H), 3.82 (d, J = 2.4 Hz,
1H); 13C NMR (100 MHz, CDCl3) d 136.67, 135.69, 134.01, 128.70,
128.55, 128.41, 126.79, 125.44, 62.82, 62.09. IR(KBr) 3046, 2979,
2917, 1650, 1589, 1488, 1457, 1274, 1087, 1010, 817, 748, 696, 516
cm-1. ESI-MS (M+): 230.
Experimental
trans-4-Bromostilbene oxide (Table 3, entry 6)
Sodium chlorite (80% purity) was purchased and used without
further purification. CH3CN, H2O and CH3OCH2CH2OH were
distilled before use. The known epoxide products were identified by
M.p. 83–85°C (lit.22 83–85°C). 1H NMR (400 MHz, CDCl3) d 7.52–
7.21 (m, 9H), 3.84 (d, J = 2.4 Hz, 1H), 3.82 (d, J = 2.4 Hz, 1H); 13
C
1
comparison of their H- and 13C NMR spectra with those reported
NMR (100 MHz, CDCl3) d 136.63, 136.11, 131.63, 128.55, 128.42,
127.09, 125.43, 122.12, 62.79, 62.13. IR(KBr) 3045, 2985, 1671,
1587, 1484, 1457, 1423, 1105, 1068, 1006, 815, 748, 698, 617, 514
cm-1. ESI-MS (M+): 274.
1
in literature. The H NMR spectra were recorded at 400 MHz (13C
NMR at 100 MHz), using CDCl3 as the solvent.
Epoxidation of trans-stilbene; typical procedure
To a stirred mixture of trans-stilbene (90 mg, 0.5 mmol) and
gold(III) chloride (7.6 mg, 0.025 mmol) in a homogeneous solvent
of CH3CN (4.5 ml), CH3OCH2CH2OH (1.5 ml) and water (1.5 ml)
trans-4-Cyanostilbene oxide (Table 3, entry 7)
M.p. 76–77°C (lit.21 colourless oil, in view of our other evidence we
believe the literature description to be in error). 1H NMR (400 MHz,
PAPER: 07/4851

724 JOURNAL OF CHEMICAL RESEARCH 2007
(k) N. Marion and S.P. Nolan, Angew. Chem., Int. Ed., 2007, 46, 2750;
(l) A.S.K. Hashimi, Chem. Rev., 2007, 107, 3180.
CDCl3)d7.70–7.26(m,9H),3.92(d,J=1.6Hz,1H),3.83(d,J=1.6Hz,
1H); 13C NMR (100 MHz, CDCl3) d 142.40, 136.11, 132.33, 128.62,
126.08, 125.46, 125.35, 118.53, 111.95, 63.16, 61.74. IR(KBr) 3041,
3010, 2225, 1602, 1494, 1459, 1423, 1280, 1170, 1091, 825, 759,
725, 694, 611, 551 cm-1. ESI-MS (M+): 221.
2
3
C.-G. Yang and C. He, J. Am. Chem. Soc., 2005, 127, 6966.
(a) J. Zhang, C.-G. Yang and C. He, J. Am. Chem. Soc., 2006, 128, 1798;
(b) C. Brouwer and C. He, Angew. Chem. Int. Ed., 2006, 45, 1744.
(a) X.-Q. Yao and C.-J. Li, J. Am. Chem. Soc., 2004, 126, 6884; (b)
R.V. Nyuyen, X.-Q. Yao, D.S. Bohle and C.-J. Li, Org. Lett., 2005, 7,
673; (c) R.V. Nyuyen, X.-Q. Yao and C.-J. Li, Org. Lett., 2006, 8, 2397;
(d) C.-Y Zhou and C.-M. Che, J. Am. Chem. Soc., 2007, 129, 5828.
X. Zhang and A. Corma, Chem. Commun., 2007, 3080.
(a) F. Gasparrini, M. Giovannoli, D. Misiti, G. Natile and G. Palmieri,
Tetrahedron, 1983, 39, 3181; (b) F. Gasparrini, M. Giovannoli, D. Misiti,
G. Natile and G. Palmieri, Tetrahedron, 1984, 40, 165; (c) F. Gasparrini,
M. Giovannoli and D. Misiti, J. Org. Chem., 1990, 55, 1323; (d) E. Boring,
Y.V. Geletti and C.L. Hill, J. Am. Chem. Soc., 2001, 123, 1625.
B. Guan, D. Xing, G. Cai, X. Wan, N. Yu, Z. Fang, L. Yang and Z. Shi,
J. Am. Chem. Soc., 2005, 127, 18004.
4
trans-4-methylstilbene oxide (Table 3, entry 8) 21
M.p. 59–61°C (lit.21 59–60°C).1H NMR (400 MHz, CDCl3)
d 7.38–7.18 (m, 9H), 3.85 (d, J = 2.4 Hz, 1H), 3.83 (d, J = 2.4 Hz,
1H), 2.37 (s, 3H); 13C NMR (100 MHz, CDCl3) d 138.11, 137.19,
134.06, 129.21, 128.50, 128.20, 125.43, 62.83, 62.71, 21.19. IR(KBr)
3049, 2984, 1494, 1457, 1427, 1218, 1108, 1049, 817, 732, 696, 607,
509 cm-1. EI-MS (M+): 210.
5
6
7
8
9
trans-4,4'-Dimethylstilbene oxide (Table 3, entry 9)
M.p. 80–82°C (lit.14 75–77°C). 1H NMR (400 MHz, CDCl3) d 7.26–
7.18 (m, 9H), 3.82 (s, 2H), 2.36 (s, 6H); 13C NMR (100 MHz, CDCl3)
d 138.01, 134.19, 129.18, 125.39, 62.74, 21.18. IR(KBr) 3032, 2896,
1608, 1523, 1278, 1010, 882, 839, 801 cm-1. EI-MS (M+): 224.
C.J. Jones, D. Taube, R.A. Periana, R.J. Nielsen, J. Oxgaard and
W.A. Goddard III, Angew. Chem. Int. Ed., 2004, 43, 4626.
G.B. Shul’pin, A.E. Shilov and G. Süss-Fink, Tetrahedron Lett., 2001, 42,
7253.
10 A. von. Baeyer and V. Villiger, Ber. Dtsch. Chem. Ges., 1899, 32, 3622.
11 Z. Li, X. Ding and C. He, J. Org. Chem., 2006, 71, 5876.
12 D. Xing, B. Guan, G. Cai, Z. Fang, L. Yang and Z. Shi, Org. Lett., 2006,
8, 693.
13 For selected heterogeneous epoxidation reactions of propene, see:
(a) T. Hayshi, K. Tanaka and M. Haruta, J. Catal. 1998, 178, 566; (b)
B. Chowdhury, J.J. Bravo-Suarez, M. Dare, S. Tsubota and
M. Haruta, Angew. Chem., Int. Ed., 2006, 45, 412; (c) T.A. Nijhuis and
B.M. Weckhuysen, Catal. Today, 2006, 117, 84; For heterogeneous
epoxidation reactions of styrene, see: (d) N.S. Patil, B.S. Uphade,
P. Jana, S.K. Bharagava and V.R. Choudhary, J. Catal., 2004, 223,
236; For heterogeneous epoxidation reactions of trans-stilbene, see: (e)
P. Ligner, F. Morfin, S. Mangematin, L. Massin, J.-L. Rousset and
V. Caps, Chem. Commun. 2007, 186.
Triphenylethylene oxide (Table 3, entry 10)
M.p. 75–76°C (lit.14 75–77°C). 1H NMR (400 MHz, CDCl3) d 7.29–
6.93 (m, 15H), 4.23 (s, 1H); 13C NMR (100 MHz, CDCl3) d 140.92,
135.73, 135.40, 129.13, 128.66, 128.56, 128.30, 127.79, 127.73,
127.65, 127.59, 127.50, 126.70, 126.28, 68.62, 67.98. IR (KBr) 3027,
1605, 1460, 1394, 1280, 756, 690 cm-1. EI-MS (m/z) (M+): 272.
2,2-diphenyl propanal (Table 3, entry 11)19a
1
Colourless oil. H NMR (400 MHz, CDCl3) d 9.91 (s, 1H), 7.35–
7.25 (m, 10H), 1.78 (s, 3H); 13C NMR (100 MHz, CDCl3) d 199.48,
141.74, 128.68, 128.11, 127.17, 59.78, 22.53. IR(KBr) 3046, 2980,
1720, 1605, 1491, 1450 860, 832, 741, 693 cm-1. ESI-MS (M+): 210.
14 X. -L. Geng, Z. Wang, X.-Q. Li and C. Zhang, J. Org. Chem., 2005, 70,
9610.
15 Other oxidants such as H2O2, Oxone, NaOCl, and PhIO did not give
epoxidation product, only trace amount of C-C double bond cleavage
products were detected.
trans-b-methylstyrene oxide (Table 3, entry 13)14
1
Colourless oil. H NMR (400 MHz, CDCl3) d 7.36–7.25 (m, 5H),
3.57 (d, J = 1.6 Hz, 1H), 3.03 (dq, J = 4.8, 1.6 Hz, 1H), 1.45 (d,
J = 4.8 Hz, 3H); 13C NMR (100 MHz, CDCl3) d 137.67, 128.35,
127.94, 125.47, 59.43, 58.94, 17.84. IR(KBr) 3033, 2924, 1691,
1447, 1246, 1067, 687 cm-1. EI-MS: m/z 134 (M+).
16 See Supplementary Data for details.
17 For the preparation of chloro(triphenylphosphine)gold(I), see: K. Burgess,
B.F.G. Johnson, J. Lewis and P.R. Raithby J. Chem. Soc., Dalton Trans.,
1983, 1661.
18 For the preparation of dichloro(pyridine-2-carboxylato)gold(III),
see: (a) A. Dar, K. Moss, S. M. Cottrill, R.V. Parish, C.A. McAuliffe,
R.G. Pritchard, B. Beagley and J. Sandbank, J. Chem. Soc., Dalton Trans.,
1992, 1907; For applications of dichloro(pyridine-2-carboxylato)gold(III),
see: (b) S. Wang and L. Zhang, J. Am. Chem. Soc., 2006, 128, 8414;
(c) S. Wang and L. Zhang, J. Am. Chem. Soc., 2006, 128, 14274;
(d) A.S.K. Hashimi, J.P. Weyrauch, M. Rudolph and E. Kurpejovic,
Angew. Chem., Int. Ed., 2004, 43, 6545.
This work was financially supported by The National Natural
Science Foundation of China (No. 20572046 and No.
20421202), the 111 Project (B06005), and the Ministry of
Education of China.
Received 26 September 2007; accepted 19 December 2007
19 For selected examples of simple metal salts induced rearrangement of
epoxides, see: (a) InCl3: B.C. Ranu and U. Jana, J. Org. Chem., 1998,
63, 8212; (b) Er(OTf)3: A. Procopio, R. Dalpozzo, A.N. Nino, M. Nardi,
G. Sindona and A. Tagarelli, Synlett, 2004, 14, 2633; (c) Bi(OTf)3:
K.A. Bhatia, K.J. Eash, N.M. Leoard, M.C. Oswald and R.S. Mohan,
Tetrahedron Lett., 2001, 42, 8129; (d) IrCl3: I. Karame, L.M. Tommasino
and M. Lemaire, Tetrahedron Lett., 2003, 44, 7687.
20 (a) K. Maruoka, N. Murase, R. Bureau, T. Ooi and H. Yamamoto,
Tetrahedron, 1994, 50, 3663; (b) T. Imama, M. Ogawa, T. Kataoka,
O. Muraoka and G. Tanabe, Tetrahedron, 1998, 54, 8941.
21 S. Oudeyer, E. Léonel, J.P. Paugam and J. -Y. Nédélec, Synthesis, 2004,
3, 389.
Paper 07/4951
doi: 10.3184/030823407X275937
References
1
For reviews on gold-catalysed transformations see: (a) A.S.K. Hashmi,
Gold Bull., 2004, 37, 51; (b) A.S.K. Hashimi, Gold Bull., 2003, 36,
3;(c)A. Hoffmann-RoderandN. Krause, Org. Biomol. Chem., 2005, 3, 387;
(d) G. Dyker, Angew. Chem., Int. Ed. 2000, 39, 4237; (e) A.S.K. Hashimi,
Angew. Chem., Int. Ed., 2005, 44, 6990; (f) S. Ma, S. Yu and Z. Gu,
Angew. Chem., Int. Ed., 2006, 45, 200; (g) E. Jimenez-Nunez, and
A.M. Echavarren, Chem. Commun., 2007, 333; (h) A.S.K. Hashmi and
G.J. Hutchings, Angew. Chem., Int. Ed., 2006, 45, 7896; (i) L. Zhang,
J. Sun and S.A. Kozmin, Adv. Synth. Catal., 2006, 348, 2271;
(j) R.A. Widenhoefer and X. Han, Eur. J. Org. Chem., 2006, 4555;
22 Y. Okazaki, F. Ando and J. Koketsu, Bull. Chem. Soc. Jpn., 2003, 76,
2155.
PAPER: 07/4851