A Highly Efficient Ruthenium-Catalyzed Rearrangement of α,β-Epoxyketones to 1,2-Diketones

Article abstract of DOI:10.1021/jo0303867

TpRuPPh₃(CH₃CN)₂PF₆ catalyzed the efficient rearrangement of α,β-epoxyketones to 1,2-diketones. Unlike a previously reported iron catalyst, the reaction in this case is applicable not only to 1,2-disubstituted epoxides but also to mono- and trisubstituted epoxides and tolerates oxygen functionalities. The sterically crowded and highly basic tris(1-pyrazolyl)borate (Tp) ligand of the ruthenium catalyst might account for its high selectivity toward 1,2-diketone rather than 1,3-diketone.

Full text of DOI:10.1021/jo0303867

A High ly Efficien t Ru th en iu m -Ca ta lyzed Rea r r a n gem en t of
r,â-Ep oxyk eton es to 1,2-Dik eton es
Chia-Lung Chang, Manyam Praveen Kumar, and Rai-Shung Liu*
Department of Chemistry, National Tsing-Hua University, Hsinchu, Taiwan, ROC
rsliu@mx.nthu.edu.tw
Received December 19, 2003
TpRuPPh3(CH3CN)2PF6 catalyzed the efficient rearrangement of R,â-epoxyketones to 1,2-diketones.
Unlike a previously reported iron catalyst, the reaction in this case is applicable not only to 1,2-
disubstituted epoxides but also to mono- and trisubstituted epoxides and tolerates oxygen
functionalities. The sterically crowded and highly basic tris(1-pyrazolyl)borate (Tp) ligand of the
ruthenium catalyst might account for its high selectivity toward 1,2-diketone rather than 1,3-
diketone.
SCHEME 1
In tr od u ction
The rearrangement of epoxides by Lewis acids is an
important method for obtaining organic ketones or alde-
hydes.1,2 The rearrangement of R,â-epoxyketones by a
Lewis acid was reported by House in the early 1960s;1
the products normally consist of a mixture of 1,2- and
1,3-diketones, which result from either hydride or acyl
migration, respectively.2 In most cases, acyl migration
is the preferred pathway because it shows neighboring
group participation in opening of the epoxide ring.2 The
selective formation of 1,2- or 1,3-diketone from R,â-
epoxyketones is an interesting issue in organic syn-
thesis.1-9 Several methods have been developed for
selective synthesis of 1,3-diketones using acid or metal
catalysts such as BF3‚Et2O,2c,d,3 LiClO4,4 zeolites,5 and Pd-
(PPh3)4.6 In contrast, little is known about the selective
synthesis of 1,2-diketones due to slow hydride migration
SCHEME 2
(path A, Scheme 1). Although Mg(ClO4)2 and Ti(Oi-
2a
7
Pr)2Cl2 are selective for the synthesis of 1,2-diketone,
an excess of acid (>1.0 equimolar) is required. Silica gel
shows activity for the rearrangement of chalcone epoxides
to 1,2-diketones, but the reaction only works for deriva-
tives of chalcone epoxides.8 Suda reported that an iron-
porphyrin catalyst effected the selective synthesis of 1,2-
diketones,9 but the examples are limited to only 1,2-
disubstituted epoxyketones. In this report, we describe
a new ruthenium catalytic reaction that is applicable not
only to 1,2-disubstituted R,â-epoxyketones but also to
mono- and trisubstituted analogues. The trend in the
catalytic activity of these epoxides is opposite that
observed for common acid catalysts.2-5
(1) (a) House, H. O. J . Am. Chem. Soc. 1954, 76, 1235. (b) House,
H. O.; Ryerson, G. D. J . Am. Chem. Soc. 1961, 83, 979.
(2) (a) Klix, R. C.; Bach, R. D. J . Org. Chem. 1987, 52, 580. (b) Bach,
R. D.; Klix, R. C. J . Org. Chem. 1985, 50, 5440. (c) Bach, R. D.;
Domagala, J . M. J . Org. Chem. 1984, 49, 4181. (d) Bach, R. D.; Klix,
R. C. Tetrahedron Lett. 1985, 26, 985.
Resu lts a n d Discu ssion s
Scheme 2 shows the working hypothesis regarding the
use of TpRuPPh3(CH3CN)2-PF610 catalyst to enhance the
desired 1,2-hydrogen shift (path a). This cationic catalyst
contains two labile CH3CN, a sterically crowded tris(1-
pyrazolyl)borate, and one triphenylphosphine ligand.
This structural feature is more suitable for the formation
of five-membered chelated diketone A rather than the
six-membered chelated species B. The bulky size of
(3) (a) Kunisch, F.; Hobert, K.; Welzel, P. Tetrahedron Lett. 1985,
26, 6039. (b) Okuda, K.; Katsura, T.; Tanino, H.; Kakoi, H.; Inoue, S.
Chem. Lett. 1994, 157.
(4) Sankararaman, S.; Nesakumar, J . E. J . Chem. Soc., Perkin
Trans. 1 1999, 3173.
(5) Elings, J . A.; Lempers, H. E. B.; Sheldon, R. A. Eur. J . Org.
Chem. 2000, 10, 1905.
(6) Suzuki, M.; Watanabe, A.; Noyori, R. J . Am. Chem. Soc. 1980,
102, 2095.
(7) Sosnovskii, G. M.; Astapovich, I. V. Zh. Org. Khim. 1993, 29,
85.
(8) Rao, T. B.; Rao, J . M. Synth. Commun. 1993, 23, 1527.
(9) Suda, K.; Baba, K.; Nakajima, S.-I.; Takanami, T. Chem.
Commun. 2002, 2570.
(10) Chan, W.-C.; Lau, C.-P.; Chen, Y.-Z.; Fang, Y.-Q.; Ng, S.-M.;
J ia, G. Organometallics 1997, 16, 34.
10.1021/jo0303867 CCC: $27.50 © 2004 American Chemical Society
Published on Web 03/13/2004
J . Org. Chem. 2004, 69, 2793-2796
2793

Chang et al.
TABLE 1. Ca ta lytic Tr a n sfor m a tion over Va r iou s Solven ts a n d Ca ta lysts
entry
catalyst
solvent
conditions
yieldsb (recovery)c
1
2
3
4
5
6
7
8
9
TpRuPPh3(CH3CN)2PF6
TpRuPPh3(CH3CN)2PF6
TpRuPPh3(CH3CN)2PF6
TpRuPPh3(CH3CN)2PF6
TpRuPPh3(CH3CN)2PF6
TpRuPPh3(CH3CN)2PF6
TpRu(PPh3)2Cl
toluene
CH3CN
DME
DCE
benzene
DMF
toluene
toluene
toluene
100 °C (5 h)
85 °C (12 h)
85 °C (12 h)
80 °C (12 h)
80 °C (12 h)
110 °C (6 h)
100 °C (5 h)
100 °C (5 h)
100 °C (5 h)
99%
94%
87% (10%)
71% (23%)
81% (17%)
89% (9%)
90%
CpRu(PPh3)2Cl
CpRu(PPh3)(CH3CN)2PF6
(94%)
(5%)
a
b
Performed with 10 mol % catalyst, [substrate] ) 0.80 M. Products were isolated from silica column. c Values in parentheses represent
recovery yields of compound 1.
TABLE 2. Ca ta lytic Tr a n sfor m a tion of Va r iou s
Mon osu bstitu ted Ep oxid es
structure B is less compatible with the congested space
around the ruthenium center. This catalyst has catalytic
activity toward transfer hydrogenation11 and cleavage of
a carbon-carbon triple bond.12
We examined the isomerization of monosubstituted
epoxide 1 in various solvents, and the results are shown
in Table 1. The yield of diketone 2 is quantitative with
10 mol % TpRuPPh3(CH3CN)2PF6 in hot toluene (100 °C,
5 h) and remains as high as 93% if 5 mol % catalyst is
used (toluene, 100 °C, 10 h). Other solvents are also
effective (entries 2-6) and give diketones 2 in yields of
71-94% without the formation of byproducts including
1,3-diketone, and this condition might be reflected by the
recovery yields of R,â-epoxyketone 1 in dimethoxyethane
(10%), dichloroethane (23%), benzene (17%), and di-
methylformamide (9%). We examined three other cata-
lysts (entries 7-9) to assess the effect of the tris(1-
pyrazolyl)borate and triphenyl phosphine ligands. To our
surprise, a slight decrease in the yield (90%) of 1,2-
diketone 1 was observed for TpRu(PPh3)2Cl. This result
is attributed to a rapid dissociation of PPh3 in the
presence of bulky tris(1-pyrazolyl)borate ligand.10 The
replacement of tris(1-pyrazolyl)borate ligand with a
cyclopentadienyl group, as in CpRu(PPh3)(CH3CN)2PF6,13
led to catalytic inactivity with exclusive recovery of the
starting epoxyketone 1 (>94%). This phenomenon is
unexpected because the metal is more acidic for CpRu-
(PPh3)(CH3CN)2PF6 than for TpRu(PPh3)(CH3CN)2PF6.
The rearrangement of monosubstituted R,â-epoxy-
ketones such as 1 normally gave complicated mixtures
of products with a conventional acidic catalyst like BF3‚
Et2O.9 It is unfavorable to produce carbocation character
on the CH2 terminus during the ring-opening of epoxide.
The ease and excellent yields in the rearrangement of
R,â-epoxyketone 1 with TpRuPPh3(CH3CN)2PF6 catalyst
encouraged us to perform an extensive investigation.
Table 2 shows the suitability of this catalyst with various
monosubstituted R,â-epoxy ketones. The ketone sub-
strates include phenyl and its 4-substituted fluoro, cyano,
and tert-butyl substituents (entries 1-4), with yields
exceeding 92%. It is also applicable to 2-naphthyl, cyclo-
a
Conditions: 10 mol % catalyst, [substrate] ) 0.80 M, 100 °C,
b
5 h. Products were isolated from silica column.
hexyl, and n-octyl groups (entries 5-7) without the
formation of byproducts including 1,3-diketones. A reac-
tion period of 5 h is sufficient to complete the isomeriza-
tion of these substrates (toluene, 100 °C).
In contrast to monosubstituted epoxides, rearrange-
ment of 1,2-disubstituted R,â-epoxy ketones requires a
greater duration of reaction (toluene, 100 °C, 12 h) to
complete the catalytic reaction (Table 3). This catalytic
reaction is equally effective for both trans- and cis-
epoxides 5a and 5b, respectively. The isolated yields of
the corresponding 1,2-diketones were as high as 91-94%
(Table 3, entries 1-2). Entries 3-8 show various R,â-
epoxyketones 5c-h with a change in the R1 and R3
substituents, which gave 1,2-diketones 6c-h in excellent
yields (>90%) without the formation of 1,3-diketones or
other byproducts. To our surprise, the styryl epoxide 5i
(entry 9) failed to undergo rearrangement, and was
recovered in 91% yield. Epoxide 5i is expected to be more
reactive than analogues with alkyl substituents (5c-h )
if carbocation character is developed during the opening
of epoxides.1-8 We also prepared trisubstituted epoxy-
ketones 5j and 5k (entries 10 and 11) that also efficiently
gave 1,2-diketones 6j and 6k , but the reaction time was
as long as 18 h. The relative activities of these epoxides
(11) Yeh, K.-L.; Liu, B.; Lo, C.-Y.; Liu, R.-S. J . Am. Chem. Soc. 2002,
124, 6510.
(12) Datta, S.; Chang, C.-L.; Yeh, K.-L.; Liu, R.-S. J . Am. Chem. Soc.
2003, 125, 9294.
2794 J . Org. Chem., Vol. 69, No. 8, 2004

Rearrangement of a,b-Epoxyketones to 1,2-Diketones
TABLE 3. Rea r r a n gem en t of Di- a n d Tr isu bstitu ted
Ep oxyk eton es
SCHEME 4
product
(yields)
entries epoxides
R1
R2
cis-H
cis-nC6H13 trans-H
R3
1
2
3
4
5
5a
5b
5c
5d
5e
5f
Ph
Ph
Ph
trans-nC4H9 6a (94%)
6b (91%)
6c (93%)
6d (94%)
6e (92%)
6f (95%)
H
Me
2-naphthyl H
Me
cyclohexyl
nC8H17
iPr
H
Me
6
cis-H
cis-H
cis-H
H
trans-nCu
7
8
9
5g
5h
5i
trans-nC6H13 6g (90%)
SCHEME 5
tBu
trans-nBu
Ph
6h (90%)
nC6H13
Ph
nrc
10
11
5j
5k
Me
Me
6j (95%)
6k (90%)
nC14H29
Me
Me
a
Conditions: 10 mol % catalyst, [substrate] ) 0.80 M, 100 °C,
b
12 h for entries 1-8, 18 h for entries 9-11. Products were
isolated from silica column. c Recovery yield of 5i was 91% in this
case.
SCHEME 3 a
cation nor radical character is being developed in this
reaction mechanism. We propose that the ruthenium
complex coordinates with the carbonyl group of R,â-
epoxyketone to generate species C. The approach of the
ruthenium center to the acidic CR-proton develops car-
boanion character to induce ring opening of the epoxides,
giving five-membered chelated enolate anion D. Repro-
tonation of the enolate functionality with the Ru-H bond
of species D is expected to regenerate active ruthenium
species and 1,2-diketone product. To examine this hy-
pothesis, we prepared the substrate 9, which was found
to be inactive in hot toluene using TpRuPPh3(CH3-
CN)2PF6 catalyst (100 °C, 12 h) with a 90% recovery. The
catalytic inactivity of compound 9 is attributed to the lack
of a CR-proton. Scheme 5 shows a crucial experiment to
confirm the enolate intermediate D. We selected epoxide
5j as a molecule for study because the resulting product
6j has a less acidic isopropyl proton to retard proton
exchange with external D2O. In the presence of D2O,
treatment of epoxide 5j with 10 mol % ruthenium catalyst
in hot CH3CN (90 °C, 6 h) gave product 6j containing
98% deuterium content, which is thought to derive from
protonation of enolate species D with D2O. The proton
exchange of product 6j with external D2O proved to be
too slow to account for such a large deuterium content
on the basis of a blank experiment.
a
Conditions: 10 mol % catalyst, [substrate] ) 0.80 M, 100 °C,
8 h. bProducts were isolated from silica column.
decrease in the order monosubstituted > 1,1-disubsti-
tuted > trisubstituted epoxides.
We also examined the ability of this catalytic activity
to tolerate different functional groups. As shown in
Scheme 3, we prepared various monosubstituted R,â-
epoxyketones 7a -e bearing an aldehyde, alcohol, diox-
alane, mono-, and 1,2-disubstituted alkenes. The 1,2-
diketones 8a -e were isolated in yields of 81-91%, which
indicates that this catalytic reaction is applicable to
various oxygen functionalities. The alkene product 8e
retains a cis geometry without isomerization of the olefin
functionality.
Scheme 4 shows a plausible mechanism that is distinct
from those observed for acid catalysts.1-8 The active
ruthenium species are likely to be neutral TpRuPPh3(CH3-
CN)PF6 in toluene because TpRu(PPh3)2Cl is equally
active. Acid-promoted ring opening of the epoxides seems
unlikely for the present system. The catalytic inactivity
of styryl oxide 5i indicates that neither benzyl carbo-
Con clu sion
We have developed a catalytic reaction for the efficient
rearrangement of R,â-epoxyketones to 1,2-diketones. The
substrates include monosubstituted, 1,2-disubstituted,
and trisubstituted R,â-epoxy ketones. The trend in the
catalytic activity of these epoxides is opposite that seen
with common acid catalysts. This catalytic reaction
tolerates suitable oxygen functionalities. 1,2-Diketones
are recognized as versatile intermediates in organic
synthesis, and their synthesis has received considerable
J . Org. Chem, Vol. 69, No. 8, 2004 2795

Chang et al.
1H), 2.96-2.93 (m, 1H). 13C NMR (100 MHz, CDCl3): δ 192.8,
attention.14,15 The present method appears to be useful
in view of its simplicity (no additives), high yields, and
wider range of suitable R,â-epoxyketones. Detailed stud-
ies are underway to elucidate the reaction mechanism.16
164.0, 130.5, 128.3, 113.9, 55.3, 50.6, 47.2. HRMS: calcd for
C
10H10O3, 178.0630; found, 178.0632.
(3) P r oced u r e for Ca ta lytic Rea ction s. To a toluene
solution (0.70 mL) were added epoxide 1 (100 mg, 0.56 mmol)
and TpRuPPh3(CH3CN)2PF6 (43 mg, 0.056 mmol), and the
reaction mixture was heated at 100 °C for 5 h. The solution
was filtered over a short silica bed and then washed with
diethyl ether (4 mL). Concentration of the filtrate under
reduced pressure gave 1,2-diketone 2 as a yellow oil (99 mg,
0.55 mmol, 99%).
Exp er im en ta l Section
Unless otherwise noted, all reactions were carried out under
a nitrogen atmosphere in oven-dried glassware using a stan-
dard syringe, cannula, and septa apparatus. Benzene, diethyl
ether, tetrahydrofuran, and hexane were dried with sodium
benzophenone and distilled before use. Dichloromethane was
dried over CaH2 and distilled before use. Vinylmagnesium
bromide, p-methoxyphenyl aldehyde, m-chloroperbenzoic acid,
and tetra-n-propylammonium perruthenate (TPAP) were ob-
tained commercially and used without purification. TpRu-
(PPh3)(CH3CN)2PF6 was prepared by heating TpRu(PPh3)2Cl
with LiPF6 in CH3CN according to a literature method.10
Spectral data of compounds 3a -h , 4a -h , 5a -k , 6a -k , and
7a -e in repetitive experiments are provided in Supporting
Information.
(4) 1-(4-Meth oxy-p h en yl)-p r op a n e-1,2-d ion e (2). Rf )
0.59 (ether/heaxane ) 1/3); IR (neat, cm-1): 3031 (w), 1732
1
(s), 1720 (s), 1622 (w). H NMR (400 MHz, CDCl3): δ 7.94 (d,
J ) 8.4 Hz, 2H), 6.94 (d, J ) 8.4 Hz, 2H), 3.87 (s, 3H), 2.48 (s,
3H); 13C NMR (100 MHz, CDCl3): δ 201.1, 189.9, 164.7, 132.7,
124.6, 114.1, 55.5, 26.4. HMRS: calcd for C10H10O3, 178.0630;
found, 178.0631.
(5) Oxir a n yl-p h en yl-m eth a n on e (3a ). This epoxide was
prepared similarly from vinylmagnesium bromide and benz-
aldehyde, followed by sequential epoxidation with m-chloro-
perbenzoic acid and oxidation with TPAP according to the
synthetic procedure for compound 1. Rf ) 0.52 (ether/hexane
(1) Sta n d a r d P r oced u r e for th e Syn th esis of R,â-
Ep oxyk eton e. Syn th esis of 1-(4-Meth oxy-p h en yl)-p r op -
2-en -1-ol. To a THF (10 mL) solution of p-methoxyphenyl
aldehyde (2.00 g, 14.7 mmol) was added vinylmagnesium
bromide (17.6 mL, 1 M, 17.6 mmol) at 0 °C, and the mixture
was stirred for 2 h before addition of H2O. The solution was
evaporated under reduced pressure, and the organic layer was
extracted with diethyl ether. The extract was dried in vacuo
and chromatographed through a silica column to give allylic
alcohol as a colorless oil (1.98 g, 12.0 mmol, 82%). IR (neat,
1
) 1/3). IR (neat, cm-1): 3033 (w), 1717 (s), 1619 (w). H NMR
(400 MHz, CDCl3): δ 8.03 (d, J ) 7.2 Hz, 2 H), 7.58 (t, J ) 7.2
Hz, 1 H), 7.48 (t, J ) 7.2 Hz, 2 H), 4.22 (dd, J ) 4.4, 2.4 Hz,
1 H), 3.10 (dd, J ) 6.4, 4.4 Hz, 1 H), 2.95 (dd, J ) 6.4, 4.4 Hz,
1 H). 13C NMR (125 MHz, CDCl3): δ 194.5, 135.3, 133.8, 128.7,
128.2, 50.9, 47.4. HMRS: calcd for C9H8O2, 148.0524; found,
148.0526.
(6) 1-P h en yl-p r op a n e-1,2-d ion e (4a ). This diketone was
obtained similarly from heating epoxide 3a with ruthenium
catalyst in hot toluene (100 °C, 5 h) according to the procedure
for compound 2. Rf ) 0.57 (ether/hexane ) 1/3). IR (neat,
cm-1): 3035 (w), 1716 (s), 1617 (w). 1H NMR (400 MHz,
CDCl3): δ 7.99 (d, J ) 7.6 Hz, 2 H), 7.62 (t, J ) 7.6 Hz, 1 H),
7.48 (t, J ) 7.6 Hz, 2 H), 2.51 (s, 3 H). 13C NMR (125 MHz
CDCl3): δ 200.5, 191.3, 134.5, 131.7, 130.2, 128.8, 26.3.
HMRS: calcd for C10H10O2, 148.0524; found, 148.0525.
(7) 3-(E)-Bu tyl-oxir a n yl-p h en yl-m eth a n on e (5a ). This
epoxide was prepared similarly from 1-hexenylmagnesium
bromide and benzaldehyde, followed by sequential epoxidation
with m-chloroperbenzoic acid and oxidation with TPAP ac-
cording to the synthetic procedure for compound 1. Rf ) 0.51
(ether/hexane ) 1/3). IR (neat, cm-1): 3034 (w), 1720 (s), 1622
1
cm-1): 3423 (vs, br), 1645 (m), 1614 (w). H NMR (400 MHz,
CDCl3): δ 7.28 (d. J ) 8.8 Hz, 2H), 6.87 (d, J ) 8.8 Hz, 2H),
6.07-5.99 (m, 1H), 5.33 (dd, J ) 17.6, 1.5 Hz, 1H), 5.16 (dd, J
) 12.8, 1.5 Hz), 5.14 (s, 1H), 3.78 (s, 3H), 1.94 (s, 1H). 13C NMR
(100 MHz, CDCl3): δ 159.0, 140.3, 134.8, 127.6, 114.6, 113.8,
74.7, 55.2. HRMS (70 eV): calcd for C10H12O2, 164.0837; found,
164.0836.
(2) Syn th esis of (4-Meth oxy-p h en yl)-oxir a n yl-m eth a -
n on e (1). To a CH2Cl2 solution (20 mL) of the preceding alcohol
(1.20 g, 7.31 mmol) was added m-chloroperbenzoic acid (2.52
g, 14.6 mmol), and the mixture was stirred at 26 °C for 12 h
before addition of water (10 mL). The organic layer was
extracted with diethyl ether, washed with NaHCO3 solution,
and dried over MgSO4. The extract was concentrated and
eluted through a silica (hexane/NEt3 ) 100/1) column to give
an epoxide as a colorless oil (1.20 g, 6.66 mmol). To a CH2Cl2
solution (20 mL) was added the epoxide (1.20 g, 6.66 mmol),
N-methyl morpholine oxide (1.35 g, 10.0 mmol), TPAP (117
mg, 0.33 mmol), and powdered 4 Å molecular sieves (0.50 g),
and the mixture was stirred at 25 °C for 1 h. The mixture was
filtered, dried in vacuo, and chromatographed through a short
alumina column to afford R,â-epoxyketone 1 (1.05 g, 5.92
mmol, 81%) as a colorless oil. Rf ) 0.41 (ether/hexane ) 1/3).
IR (neat, cm-1): 3032 (w), 1722 (s), 1622 (w). 1H NMR (400
MHz, CDCl3): δ 8.03 (d, J ) 8.4 Hz, 2H), 6.95 (d, J ) 8.4 Hz,
2H), 4.18 (t, J ) 2.6 Hz, 1H), 3.87 (s, 3H), 3.06 (t, J ) 2.6 Hz,
1
(w). H NMR (400 MHz, CDCl3): δ 7.99 (d, J ) 7.3 Hz, 2H),
7.60 (t, J ) 7.3 Hz, 1H), 7.48 (t, J ) 7.3 Hz, 2H), 4.00 (d, J )
2.0 Hz, 1H), 3.14-3.10 (m, 1H), 1.77-1.66 (m, 2H), 1.52-1.46
(m, 2H), 1.44-1.36 (m, 2H), 0.91 (t, J ) 6.8 Hz, 3H). 13C NMR
(100 MHz, CDCl3): δ 194.5, 135.4, 133.6, 128.6, 128.1, 59.9,
57.2, 31.5, 27.2, 22.2, 13.7. HMRS: calcd for
204.1150; found, 204.1153.
C13H16O2,
1-P h en yl-h ep ta n e-1,2-d ion e (6a ). This diketone was ob-
tained similarly from heating epoxide 5a with ruthenium
catalyst in hot toluene (100 °C, 10 h) according to the procedure
for compound 2. Rf ) 0.75 (ether/hexane ) 1/3). IR (neat,
cm-1): 3037 (w), 1735 (s), 1712 (s), 1618 (w). 1H NMR (400
MHz, CDCl3): δ 7.97 (d, J ) 7.8 Hz, 2H), 7.64 (t, J ) 7.8 Hz,
1H), 7.50 (t, J ) 7.8 Hz, 2H), 2.87 (t, J ) 7.4 Hz, 2H), 1.72-
1.70 (m, 2H), 1.38-1.32 (m, 4H), 0.90 (t, J ) 7.4 Hz, 3H). 13C
NMR (100 MHz, CDCl3): δ 203.4, 192.5, 134.4, 131.9, 130.0,
128.7, 38.6, 31.2, 22.4, 22.3, 13.8. HMRS: calcd for C13H16O2,
204.1150; found, 204.1151.
(13) CpRu(CH3CN)2PPh3PF6 was prepared in situ from equimolar
of CpRu(CH3CN)3PF6 and PPh3.
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(16) Mechanism of this rearrangement is also distinct from that of
the iron-porphyrin catalyst,9 which is applicable to styrylepoxy ketones
5i, affording excellent yields of 1,2-diketone products.
(17) Although this catalytic reaction works well for R,â-epoxy
ketones, it is not applicable to R,â-epoxy aldehydes.
Ackn owledgm en t. We thank National Science Coun-
cil, Taiwan, for financial support of this work.
Su p p or tin g In for m a tion Ava ila ble: Spectral data of R,â-
epoxyketones 3b-g, 5b-k , and 7a -e and 1,2-diketones 4b-
h , 6b-k , and 8a -e in repetitive experiments. This material
is available free of charge via the Internet at http://pubs.acs.org.
J O0303867
2796 J . Org. Chem., Vol. 69, No. 8, 2004