Gold(III)-catalyzed intramolecular furanylation and cyclopropanation of acyclic conjugated enynones

Article abstract of DOI:10.1055/s-0032-1317926

We have developed an efficient cascade gold-catalyzed furanylation- cyclopropanation of acyclic (E)-deca-2,9-dien-4-yn-1-ones and an (E)-undeca-2,10-dien-4-yn-1-one to give 1-(2-furyl)bicyclo[3.1.0]hexanes and a 1-(2-furyl)bicyclo[4.1.0]heptane, respectiv

Full text of DOI:10.1055/s-0032-1317926

174▌
PAPER
pGapoerld(III)-Catalyzed Intramolecular Furanylation and Cyclopropanation of
Acyclic Conjugated Enynones
Gold(III)-Catalyzed Intramolecular Furanylation and Cyclopropanation
Chang Ho Oh,* Lanhua Piao, Ji Hee Kim
Department of Chemistry and Research Institute for Natural Science, Hanyang University, Sungdong-Gu, Seoul 133 791, South Korea
Fax +82(2)22990762; E-mail: changho@hanyang.ac.kr
Received: 19.09.2012; Accepted after revision: 23.11.2012
diates that undergo cycloaddition reactions with
Abstract: We have developed an efficient cascade gold-catalyzed
additional alkynes or alkenes.5
furanylation–cyclopropanation of acyclic (E)-deca-2,9-dien-4-yn-
1-ones and an (E)-undeca-2,10-dien-4-yn-1-one to give 1-(2-fu-
ryl)bicyclo[3.1.0]hexanes and a 1-(2-furyl)bicyclo[4.1.0]heptane,
respectively. This requires a configurational change from the E-iso-
mer to the Z-isomer prior to furan formation. The intermediate was
proposed to be a gold–carbene, which would undergo cyclopropa-
nation to furnish the product.
Many diynals, enynals, and enynones have been trans-
formed to novel bifunctional metal-containing carbonyl
ylides, dipolar species, with alkynophilic metal cations
and successively reacted with an unsaturated bond to pro-
vide polycycles via cycloaddition.6 Recently we exten-
sively studied various platinum-catalyzed Husigen-type
[3+2]-cycloadditions of enynal substrates.7 In general, the
platinum–pyrylium intermediate, formed in situ in a 6-
endo-dig manner, reacts with a double bond to form the
platinum–carbene complex which, depending on the reac-
tion conditions, undergoes deprotonation, hydration, or
insertion to give various [m,7,n] tricyclic compounds. In
contrast to platinum catalysts, gold catalysts have exhibit-
ed a somewhat different behavior toward enynals. Gold
compounds react with substrate I to form the furanyl in-
termediate A in a 5-exo-dig manner in which the resulting
gold–carbene would undergo cyclopropanation with the
pendant double bond to give the product II.8 It is worth
noting that we have found a similar transformation but
with a different mechanistic pathway from enediynal III
to the furan IV under palladium-catalyzed cycloreduction
conditions. The hydropalladation would occur at the ter-
minal triple bond of III to form vinylpalladium which un-
derwent carbopalladation with the internal alkyne unit to
form the intermediate B,9 and then subsequent carbonyl
oxygen attack to the carbon attached to the palladium
could result in the formation of the product IV and palla-
dium species for next catalytic cycles (Scheme 1).10
Key words: cyclization, gold catalyst, furanylation, cyclopropana-
tion, enynone
Among many new synthetic transformations, transition-
metal-catalyzed reactions are very attractive since these
reactions can directly construct complicated molecules
from readily accessible starting materials under mild con-
ditions.1 Platinum- or gold-catalyzed electrophilic activa-
tion of alkynes has attracted much attention as an efficient
method to facilitate atom-economical construction of
complex molecules.2 The use of gold compounds as ho-
mogeneous catalysts for the conversion of many organic
substrates is a fast growing area in organic chemistry.3
Gold catalysis is emerging as an extraordinary tool to cre-
ate molecular complexity due to the unique ability of
gold(I) and gold(III) complexes to activate C–C π-sys-
tems.4 Electrophilic activation of the alkyne occurs by al-
kynophilic gold compounds and hence substrates
containing both an acetylene moiety and an oxygen or ni-
trogen atom can be transformed into zwitterionic interme-
A
AuBr3 (5 mol%)
CHO
O
O
toluene
E
E
r.t., 0 °C
Au3+
E
Au3+
II
I
E
E
E
O
CHO
Pd(PPh3)4 (3 mol%)
HCOOH (1.5 equiv)
Pd
O
O
H
O
E
dioxane, 80 °C
E = CO2Et
E
Pd
E
IV
E
E
III
B
E
Scheme 1 Furan formation from enynals under gold and palladium catalysis
SYNTHESIS 2013, 45, 0174–0182
Advanced online publication: 13.12.2012
0
0
3
9
-
7
8
8
1
1
4
3
7
-
2
1
0
X
DOI: 10.1055/s-0032-1317926; Art ID: SS-2012-F0735-OP
© Georg Thieme Verlag Stuttgart · New York

PAPER
Gold(III)-Catalyzed Intramolecular Furanylation and Cyclopropanation
175
The furan nucleus is of immense interest because it is Thus, we synthesized acyclic enynal (Z)-1a, with Z con-
widely found in numerous natural products and biologi- figuration, and screened its reaction with several transi-
cally active compounds and can be utilized to access other tion-metal catalysts (Table 1). First, gold(III) bromide
useful compounds.11 Furan syntheses in a 5-exo-dig man- was chosen based on our previous work.8 Thus, the cata-
ner from alkynones or alkenones have been reported using lytic activity of gold(III) bromide, platinum(II) chloride,
a variety of catalysts containing mercury,12 palladium,13 silver(I) triflate were examined in the furanylative cyclo-
gold,14 and indium.15 In an extension to work on gold-cat- propanations of (Z)-1a in toluene, which gave the corre-
alyzed furanylation–cyclopropanation,16 we wish to re- sponding product 2a in 65%, 61%, and 40% yields,
port our recent results using acyclic enynals and enynones respectively (entries 1–3). Since platinum(II) chloride
with gold catalysis. Compared to the previous substrates was found to catalyze the present reaction well, we further
anchored by rigid aromatics or cycloalkenes, the present examined other platinum(II) chloride based catalytic sys-
work using acyclic substrates is of interest to us because tems. Thus PtCl2(PPh3)2 in refluxing toluene was found to
of their relatively flexible configurations. For metal- catalyze the reaction of (Z)-1a to give 2a together with 3a
catalyzed reactions of acyclic ynones with an alkene, the (entry 4). Cationic platinum, generated in situ from plati-
Echavarren group reported cyclization of acyclic enynes num(II) chloride/silver(I) hexafluoroantimonate, reacted
bearing a carbonyl group at the alkenyl side chain to give with (Z)-1a in toluene to afford solely the cyclized prod-
oxatricyclic derivatives by using gold(I) catalyst.17 The uct 3a in 26% yield (entry 5); in dichloromethane, this cat-
Iwasawa group also reported in 2008 that acyclic γ,δ- ionic platinum afforded 3a as the major product (entry 6).7
ynones using a catalytic amount of platinum(II) chloride Platinum(II) chloride/silver(I) tetrafluoroborate in dichlo-
in the presence of electron-rich alkenes gave oxabicyclic romethane, however, afforded 3a in only 21% yield (entry
derivatives through the novel bifunctional platinum- 7). Assuming that solvent polarity is important in the pres-
containing carbonyl ylides and developed its asymmetric ent reaction, we examined gold(III) bromide as a catalyst
version in 2010.18
in different solvents. The reaction of (Z)-1a using
gold(III) bromide catalysis with dichloromethane or hex-
ane as the solvent in resulted in the formation of 2a in 45%
and 86% yields, respectively (entries 8 and 9).
Table 1 Furanylative Cyclopropanations of Enynal (Z)-1a
O
With this encouraging result in hand, a new acyclic eny-
none 1b was examined. Since the Z-configuration was re-
quired in order to form the furan ring, we expected that 1b
could be isomerized into (Z)-1b under our conditions.
Fortunately, when we treated 1b with a gold(III) bromide
solution in hexane for four hours, the corresponding prod-
uct 2b was isolated in 75% yield as the major product
along with two byproducts. When we ran this reaction in
dichloromethane, the H-shift product, 3b, was obtained
along with 2b in 27% and 54% yields, respectively. Yet,
such a dramatic solvent dependency is still unknown. A
possible pathway for this reaction is proposed in Scheme
2.
O
O
COOEt
COOEt
+
COOEt
COOEt
COOEt
COOEt
(Z)-1a
2a
3a
Catalysta
Solvent
Temp Time Yield
(°C) (h)
(%)
1
2
3
4b
5
6
7
8
9
AuBr3
toluene
toluene
toluene
toluene
toluene
CH2Cl2
CH2Cl2
CH2Cl2
hexane
r.t.
60
1
6
2
1
2
1
1
2
1
65 (2a)
61 (2a)
40 (2a)
PtCl2
AgOTf
80
Initially, the E-configuration of 1b should be isomerized
to the Z-configuration. We proposed that the gold cation
would coordinate with the carbonyl oxygen to form C
which could make isomerization into (Z)-1b possible. The
intermediate (Z)-1b would be activated by alkynophilic
gold cation to D followed by cyclization to yield ylide F
through E.19 The carbenoid F would react with the pen-
dant double bond to form the cyclopropane 2b as the ma-
jor route. When this reaction was carried out in relatively
polar dichloromethane, the carbenoid F could undergo H-
transfer to afford the product 3b. We also wish to report
the scope of the furanylative cyclopropanations of eny-
nones catalyzed by gold(III) bromide in hexane. We pre-
pared various acyclic enynones 1c–m by known
methods.20 Then, we tested the substrates under our opti-
mized conditions [AuBr3 (5 mol%), dry hexane, 25–60
°C] and the results are summarized Table 2.
PtCl2(PPh3)2
PtCl2/AgSbF6
PtCl2/AgSbF6
PtCl2/AgBF4
AuBr3
120
r.t.
r.t.
r.t.
r.t.
r.t.
19 (2a), 31 (3a)
26 (3a)
57 (3a)
21 (3a)
45 (2a)
AuBr3
86 (2a)
a Catalyst (5 mol%) was used.
b Substrate (Z)-1a (40%) was recovered.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 174–182

176
C. H. Oh et al.
PAPER
Ph
O
O
Ph
Ph
Ph
AuBr3 = Au(+)
hexane, 75%
cyclopropanation
Au(+)
O
O
H-shift
E
E
E
E
E
E
E
E
(+)Au
1b
2b
F
3b
Au(+)
Au(+)
Ph
Ph
Ph
O
Ph
O
O
Au(+)
O+
(+)Au
E
E
E
E
(+)Au
E
Au
E
E
E
E
C
(Z)-1b
D
E = CO2Et
Scheme 2 Proposed mechanism furanylative cyclopropanation
Table 2 Gold-Catalyzed Furanylative Cyclopropanation of Enynones
Entry
Substrate
Temp, time
Products
Yield (%)
O
Ph
O
Ph
1
60 °C, 12 h
89
OBn
OBn
OBn
BnO
2c
1c
O
Ph
Ph
O
2
25 °C, 15 h
72
COOEt
COOEt
COOEt
COOEt
2d
1d
MeO
MeO
O
O
3
60 °C, 10 h
64
COOEt
COOEt
COOEt
COOEt
1e
2e
Synthesis 2013, 45, 174–182
© Georg Thieme Verlag Stuttgart · New York

PAPER
Gold(III)-Catalyzed Intramolecular Furanylation and Cyclopropanation
177
Table 2 Gold-Catalyzed Furanylative Cyclopropanation of Enynones (continued)
Entry
Substrate
Temp, time
60, °C12 h
Products
Yield (%)
O
O
O
O
4
52
COOMe
COOMe
COOMe
COOMe
2f
1f
O
Ph
Ph
O
OBn
5
6
7
60 °C, 1 h
60 °C, 2 h
60 °C, 10 h
87
90
73
BnO
2g
1g
MeO
MeO
O
O
OBn
BnO
2h
1h
O
Ph
Ph
O
O
O
COOMe
COOMe
COOMe
COOMe
2i
1i
O
8
60 °C, 6 h
86
COOMe
COOMe
COOMe
COOMe
2j
1j
O
9
60 °C, 20 h
61
COOMe
COOMe
COOMe
COOMe
1k
2k
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 174–182

178
C. H. Oh et al.
PAPER
Table 2 Gold-Catalyzed Furanylative Cyclopropanation of Enynones (continued)
Entry
Substrate
Temp, time
60 °C, 15 h
Products
Yield (%)
O
O
OBn
10
65
BnO
1l
2l
O
2-naph
O
OBn
11
60 °C, 2 h
72
BnO
2m
1m
a General conditions: 0.1 to 1.0 mmol scale, AuBr3 (5 mol%), hexane (1–2 mL).
Ph
Ph
Ph
O
O
O
O
Ph
AuBr3
OBn
+
OBn
OBn
OBn
OBn
3+Au
Ph
OBn
O
O
Ph
3c (0%)
1c
H
G
2c (89%)
Scheme 3 Cyclopropanation to give 2c vs C–H insertion to give 3c of gold–carbene G
All substrates (Z)-1a and 1b–m were successfully trans- 2g,h,l,m were obtained as a single diastereomer with a
formed into the furanyl-substituted bicyclo[n.1.0]alkane trans relationship between the furanyl group and benzyl-
derivatives 2a–m with good to excellent yields. Substrate oxy group.21
1c was designed in order to see if there was any possibility
In summary, we have found that the gold-catalyzed reac-
of benzylic C–H insertion into the gold–carbene species G
tion of acyclic enynones 1 provide the furanyl-substituted
to form 3c, but this resulted in failure (Scheme 3).
bicyclo[n.1.0]alkanes 2 in good to excellent yields. Fur-
Substrate 1d, a homologue of 1b, gave bicyclo[4.1.0]hep- ther studies to extend the practical application are in prog-
tane derivative 2d in 72% yield. Substrates 1e, with a me- ress in our group.
thoxy group on the phenyl ring, also gave corresponding
products 2e in good yield (64%). Substrate 1f with a fura-
nyl group also worked well to give the product 2f in 52%
yield. Even substrates 1g and 1h containing a stereogenic
center resulted in exclusive formation of 2g (87%) and 2h
(90%), respectively, under these conditions. Replacing
the aryl group by an alkyl group did not affect this reaction
in terms of efficiency. Substrates 1i with a benzyl group
and substrates, 1j–l with a pentyl group on the carbonyl
group underwent these reactions smoothly to give the
products 2i–l in 73%, 86%, 61%, and 65% yields, respec-
tively. Finally, substrate 1m with a 2-naphthyl substituent
underwent the reaction to afford 2m in 72% yield. Note
that the bulkiness at the alkenyl position of 1l and 1m did
1H and 13C NMR spectra were recorded with a Varian Mercury 400
instrument and chemical shifts were measured relative to the resid-
ual solvent signal or TMS as an internal standard. All reagents were
reagent grade and used without further purification. All solvents in-
cluding hexane were used after distillation unless specified other-
wise. Technical grade EtOAc and n-hexane used for column
chromatography were distilled prior to use. Column chromatogra-
phy was carried out using silica gel (60–120 mesh) packed in glass
columns. All reactions were performed under argon atmosphere in
oven-dried glassware with magnetic stirring. General routes for the
synthesis of (Z)-1a and 1b are given in Schemes 4 and 5, respective-
ly. All other substrates 1c–m were prepared by using the corre-
sponding iodoacrylate (instead of 8) and enyne (instead of 5).
Methyl 3-Iodoacrylate (4)22
NaI (8.4 g, 56.1 mmol) was dried under vacuum for 30 min and dis-
solved in AcOH (20 mL) under an argon atmosphere. To this soln
1
not diminish its scope. Based on H and 13C NMR data,
Synthesis 2013, 45, 174–182
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PAPER
Gold(III)-Catalyzed Intramolecular Furanylation and Cyclopropanation
179
graphed (silica gel, hexane–EtOAc, 10:1, Rf = 0.3) to afford (Z)-1a
O
(250.7 mg, 72%) as a yellow oil.
E
E
+
E
E
3-Iodo-1-phenylprop-2-en-1-one (8)20a
NaI (1.56 g, 15.5 mmol) was dried under vacuum for 30 min and
dissolved in AcOH (20 mL) under an argon atmosphere. To this
soln was added the compound 7 (1.20 g, 17 mmol) at r.t. The result-
ing mixture was stirred for 12 h at 60 °C. When the reaction was
complete (TLC analysis), it was quenched with sat. NaCl soln. The
organic layer was extracted with Et2O (2 × 50 mL), and the com-
bined organic layers were washed with sat. NaCl soln, dried (anhyd
MgSO4), and concentrated by rotary evaporation. The residues were
column chromatographed (silica gel, hexane–EtOAc, 10:1,
Rf = 0.3) to afford compound 8 (1.26 g, 64%) as a yellow oil.
I
E
E
6
(Z)-1a
E
4
5
E
E = COOEt
Scheme 4 Preparation of substrate (Z)-1a
was added ethyl propiolate (5.01 g, 51.0 mmol) at r.t. The resulting
mixture was stirred for 6 h at 70 °C. When the reaction was com-
plete (TLC analysis), the mixture was cooled to r.t. and diluted with
sat. NaCl soln. The organic layer was extracted with Et2O (2 × 50
mL), and the combined organic layers were washed with sat. NaCl
soln, dried (anhyd MgSO4), filtered, and concentrated using a rotary
evaporator. The residue was column chromatographed (silica gel,
hexane–EtOAc, 10:1, Rf = 0.4) to afford compound 4 (8.3 g, 72%)
as a yellow oil.
Dimethyl 2-Allyl-2-(6-oxo-6-phenylhex-4-en-2-ynyl)malonate
(1b)
To a soln of compound 8 (1.26 g, 4.88 mmol) in DMF (15 mL) was
added PdCl2(PPh3)2 (68.5 mg, 0.098 mmol) and CuI (46.5 mg, 0.24
mmol) at 0 °C. The mixture was stirred for 5 min, and then 5 (1.40
g, 5.86 mmol) and Et3N (2.7 mL, 19.5 mmol) were added. The re-
sulting mixture was stirred for 1 h at r.t. When the reaction was
complete (TLC analysis), it was quenched with sat. NH4Cl soln.
The organic layer was extracted with Et2O (2 × 50 mL), washed
with sat. NaCl soln, dried (anhyd MgSO4), and concentrated by ro-
tary evaporation. The residues were column chromatographed (sili-
ca gel, hexane–EtOAc, 10:1, Rf = 0.2) to afford compound 1b (1.27
g, 71%) as a yellow oil.
Diethyl 2-Allyl-2-(prop-2-ynyl)malonate (5)23
Diethyl allylmalonate (3.0 g, 15 mmol) was dissolved in anhyd
DMF (25 mL). The mixture was cooled to 0 °C and NaH (0.72 g,
18.0 mmol) was slowly added. After 10min of stirring at 0 °C,
propargyl bromide (2.15 g, 18.0 mmol) was added. The mixture was
stirred for 30 min at 0 °C, and then it was allowed to warm up to r.t.
and stirred for an additional 30 min. When the reaction was com-
plete (TLC analysis), it was quenched with sat. NH4Cl soln at 0 °C.
The organic layer was extracted with Et2O (2 × 50 mL) and the com-
bined organic layers were washed with sat. NaCl soln, dried (anhyd
MgSO4), filtered, and concentrated using a rotary evaporator. The
residues were column chromatographed (silica gel, hexane–EtOAc,
10:1, Rf = 0.4) to afford compound 5 (3.3 g, 92%) as a colorless oil.
Diethyl 1-(5-Phenylfuran-2-yl)bicyclo[3.1.0]hexane-3,3-dicar-
boxylate (2b); Typical Procedure
Enynone 1b (37.0 mg, 0.1 mmol), AuBr3 (2 mg, 0.005 mmol), and
dry hexane (1.0 ml) were placed in a new 5-mL test tube at 0 °C.
The mixture was purged with a stream of dry argon gas and stirred
at r.t. for 4 h (TLC monitoring). Upon completion, a drop of Et3N
was added to quench the reaction and the solvent was removed un-
der vacuum. The residue was purified by flash column chromatog-
raphy (silica gel, hexane–EtOAc, 20:1) to give the product 2b (27.8
mg, 75%) as a colorless oil.
Trimethyl Nona-1,8-dien-3-yne-1,6,6-tricarboxylate (6)
To a DMF (15 mL) soln of compound 4 (2.01 g, 8.4 mmol) was add-
ed PdCl2(PPh3)2 (118.4 mg, 0.17 mmol, 2 mol%) and CuI (80.3 mg,
0.42 mmol) at 0 °C. The mixture was stirred for 5 min, and then ad-
ditional 5 (2.41 g, 10.1 mmol) and Et3N (4.7 mL, 33.8 mmol) in
DMF (5 mL) were added. The resulting mixture was stirred for 4 h
at 60 °C. When the reaction was complete (TLC analysis), it was
quenched with sat. NH4Cl soln. The organic layer was extracted
with Et2O (2 × 50 mL), and the combined organic layers were
washed with sat. NaCl soln, dried (anhyd MgSO4), filtered, and con-
centrated. The residues were column chromatographed (silica gel,
hexane–EtOAc, 10:1, Rf = 0.2) to afford compound 6 (1.98 g, 70%)
as a yellow oil.
1H NMR (400 MHz, CDCl3): δ = 7.59 (d, J = 7.6 Hz, 2 H), 7.36–
7.33 (m, 2 H), 7.22–7.19 (m, 1 H), 6.55 (d, J = 2.8 Hz, 1 H), 6.11
(d, J = 3.6 Hz, 1 H), 4.25–4.16 (m, 4 H), 2.98–2.85 (m, 2 H), 2.69–
2.59 (m, 2 H), 1.85–1.80 (m, 1 H), 1.30–1.20 (m, 7 H), 0.75–0.72
(m, 1 H).
13C NMR (100 MHz, CDCl3): δ = 172.57, 171.49, 156.51, 151.71,
130.94, 128.56, 126.79, 123.29, 106.01, 105.88, 61.88, 61.74,
59.54, 37.95, 35.90, 27.26, 26.73, 16.95, 14.02.
HRMS: m/z [M]+ calcd for C22H24O5: 368.1624; found: 368.1624.
Diethyl 1-(Furan-2-yl)bicyclo[3.1.0]hexane-3,3-dicarboxylate
(2a)
Diethyl 2-Allyl-2-(6-oxohex-4-en-2-ynyl)malonate [(Z)-1a]
A 1.0 M DIBAL-H in THF soln (1.4 mL, 1.4 mmol) was added
dropwise to a soln of 6 (401.1 mg, 1.2 mmol) in CH2Cl2 (10 mL) at
–78 °C, on completion of the addition, the mixture was stirred for
30 min. When the reaction was complete (TLC analysis), it was
quenched with 1.0 M HCl soln. The organic layer was extracted
with Et2O (2 × 50 mL), and the combined organic layers were
washed with sat. NaCl soln, dried (anhyd MgSO4), and concentrat-
ed by rotary evaporation. The residues were column chromato-
Colorless oil; yield: 25.9 mg (86%).
1H NMR (400 MHz, CDCl3): δ = 7.23 (s, 1 H), 6.28 (t, J = 2.2 Hz,
1 H), 6.02 (d, J = 3.2 Hz, 1 H), 4.21 (q, J = 7.2 Hz, 2 H), 4.17 (q,
J = 7.2 Hz, 2 H), 2.83 (ABq, Δδ = 20.4 Hz, J = 17.6 Hz, 2 H), 2.63
(d, J = 14.0 Hz, 1 H), 2.58 (dd, J = 14.0, 4.8 Hz, 1 H), 1.73 (m, 1 H),
1.27 (t, J = 7.2 Hz, 3 H), 1.23 (J = 7.2 Hz, 3 H), 1.13 (dd, J = 6.4,
6.4 Hz, 1 H), 0.67 (dd, J = 6.4, 6.4 Hz, 1 H).
O
O
O
Ph
CO2Et
+
CO2Et
CO2Et
CO2Et
I
8
7
5
1b
Scheme 5 Preparation of substrate 1b
© Georg Thieme Verlag Stuttgart · New York
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180
C. H. Oh et al.
PAPER
13C NMR (100 MHz, CDCl3): δ = 172.71, 171.63, 156.92, 140.53,
110.46, 103.92, 61.98, 61.84, 59.69, 38.21, 36.03, 27.18, 26.36,
16.69, 14.14.
1H NMR (400 MHz, CDCl3): δ = 7.58 (d, J = 7.2 Hz, 2 H), 7.34 (t,
J = 7.6 Hz, 3 H), 7.29–7.23 (m, 5 H), 6.56 (d, J = 3.2 Hz, 1 H), 6.10
(d, J = 3.2 Hz, 1 H), 4.67 (t, J = 8.4 Hz, 1 H), 4.55 (s, 2 H), 2.06 (dt,
J = 12.8, 8.0 Hz, 1 H), 1.93, (ddd, J = 12.0, 8.0, 4.0 Hz, 1 H), 1.82
(dd, J = 12.4, 8.4 Hz, 1 H), 1.65 (m, 1 H), 1.40 (m, 1 H), 1.31 (dd,
J = 5.0, 4.8 Hz, 1 H), 1.23 (dd, J = 8.0, 5.0 Hz 1 H).
13C NMR (100 MHz, CDCl3): δ = 157.05, 151.92, 138.88, 131.28,
128.68, 128.42, 127.93, 127.59, 126.86, 123.49, 106.58, 106.14,
81.93, 71.89, 30.50, 27.48, 27.40, 24.75, 12.05.
HRMS: m/z [M]+ calcd for C16H20O5: 292.1311; found: 292.1320.
3,3-[Bis(benzyloxy)methyl]-1-(5-phenylfuran-2-yl)bicyc-
lo[3.1.0]hexane (2c)
Yellow oil; yield: 40.2 mg (89%).
1H NMR (400 MHz, CDCl3): δ = 7.71 (d, J = 6.8 Hz, 2 H), 7.60–
7.39 (m, 12 H), 7.34 (t, J = 7.6 Hz, 1 H), 6.67 (d, J = 3.0 Hz, 1 H),
6.16 (d, J = 3.0 Hz, 1 H), 4.69 (s, 2 H), 4.65 (s, 2 H), 3.61 (s, 2 H),
3.52 (s, 2 H), 2.46 (d, J = 13.6 Hz, 1 H), 2.19 (dd, J = 14.0, 6.4 Hz,
1 H), 2.06 (d, J = 13.6 Hz, 1 H), 1.91 (m, 1 H), 1.76 (d, J = 13.6 Hz,
1 H), 1.60 (dd, J = 8.4, 4.0 Hz, 1 H), 0.97 (dd, J = 5.0, 4.6 Hz, 1 H).
HRMS: m/z [M]+ calcd for C23H22O2: 330.1620; found: 330.1620
trans-2-(Benzyloxy)-1-[5-(3-methoxyphenyl)furan-2-yl]bicyc-
lo[3.1.0]hexane (2h)
Colorless oil; yield: 37.0 mg (90%).
13C NMR (100 MHz, CDCl3): δ = 158.60, 151.53, 138.92, 131.27,
128.63, 128.37, 127.50, 127.48, 126.70, 123.31, 106.01, 105.26,
74.63, 74.58, 73.32, 73.30, 38.89, 36.31, 29.61, 29.47, 25.20.
1H NMR (400 MHz, CDCl3): δ = 7.29–7.17 (m, 7 H), 7.13 (d,
J = 2.0 Hz, 1 H), 6.78 (dd, J = 8.0, 1.6 Hz, 1 H), 6.56 (d, J = 3.2 Hz,
1 H), 6.10 (d, J = 3.2 Hz, 1 H), 4.66 (t, J = 8.0 Hz, 1 H), 4.54 (s, 2
H), 3.82 (s, 3 H), 2.05 (dt, J = 13.2, 7.6 Hz, 1 H), 1.93, (ddd,
J = 12.0, 8.0, 4.0 Hz, 1 H), 1.82 (dd, J = 12.4, 8.4 Hz, 1 H), 1.65 (m,
1 H), 1.40 (m, 1 H), 1.31 (dd, J = 5.0, 4.8 Hz, 1 H), 1.22 (dd, J = 8.0,
4.6 Hz 1 H).
13C NMR (100 MHz, CDCl3): δ = 159.95, 157.06, 151.67, 138.81,
132.52, 129.73, 128.39, 127.88, 127.56, 116.15, 112.40, 109.04,
106.57, 106.49, 81.88, 71.85, 55.37, 30.46, 27.45, 27.34, 24.70,
12.03.
HRMS: m/z [M]+ calcd for C32H32O3: 464.2351; found: 464.2360.
Diethyl 1-(5-Phenylfuran-2-yl)bicyclo[4.1.0]heptane-3,3-dicar-
boxylate (2d)
Colorless oil; yield: 36.8 mg (72%).
1H NMR (400 MHz, CDCl3): δ = 7.58 (d, J = 7.6 Hz, 2 H), 7.34 (t,
J = 8.0 Hz, 2 H), 7.19 (t, J = 7.6 Hz, 1 H), 6.56 (d, J = 3.2 Hz, 1 H),
6.23 (d, J = 3.2 Hz, 1 H), 4.19 (q, J = 7.2 Hz, 2 H), 4.18 (q, J = 7.2
Hz, 2 H), 3.12 (d, J = 14.8 Hz, 1 H), 2.14 (d, J = 14.0 Hz, 1 H), 2.02
(d, J = 14.4 Hz, 1 H), 1.92 (m, 2 H), 1.66 (m, 1 H), 1.59 (m, 1 H),
1.37 (dd, J = 9.6, 4.0 Hz, 1 H), 1.26 (t, J = 7.2 Hz, 3 H), 1.20 (t,
J = 7.2 Hz, 3 H), 0.68 (dd, J = 5.6, 5.2 Hz, 1 H).
13C NMR (100 MHz, CDCl3): δ = 172.44, 171.03, 159.64, 151.25,
131.32, 128.64, 126.69, 123.32, 106.20, 105.73, 61.57, 61.39,
52.81, 33.34, 25.00, 20.34, 19.46, 17.14, 14.18.
HRMS: m/z [M]+ calcd for C24H24O3: 360.1725; found: 360.1726.
Dimethyl 1-(5-Benzylfuran-2-yl)bicyclo[3.1.0]hexane-3,3-di-
carboxylate (2i)
Colorless oil; yield: 23.9 mg (73%).
1H NMR (400 MHz, CDCl3): δ = 7.31–7.22 (m, 5 H), 5.91 (d,
J = 2.8 Hz, 1 H), 5.83 (d, J = 2.8 Hz, 1 H), 3.89 (s, 2 H), 3.74 (s, 3
H), 3.71 (s, 3 H), 2.81 (ABq, Δδ = 26.4 Hz, J = 18.4 Hz, 2 H),
2.63(d, J = 13.6 Hz, 1 H), 2.59 (dd, J = 13.6, 4.4 Hz, 1 H), 1.69 (m,
1 H), 1.08 (dd, J = 7.2, 7.2 Hz, 1 H), 0.59 (dd, J = 5.2, 4.8 Hz, 1 H).
13C NMR (100 MHz, CDCl3): δ = 173.15, 172.08, 155.60, 152.64,
138.41, 128.79, 128.53, 126.47, 107.06, 104.66, 59.57, 53.14,
53.01, 38.39, 36.17, 34.63, 27.17, 26.23, 16.63.
HRMS: m/z [M]+ calcd for C23H26O5: 382.1780; found: 382.1793.
Diethyl 1-[5-(3-Methoxyphenyl)furan-2-yl]bicyclo[3.1.0]hex-
ane-3,3-dicarboxylate (2e)
Colorless oil; yield: 20.0 mg (64%).
1H NMR (400 MHz, CDCl3): δ = 7.26 (t, J = 8.4 Hz, 1 H), 7.18 (d,
J = 8.0 Hz, 1 H), 7.12 (s, 1 H), 6.77 (d, J = 8.0 Hz, 1 H), 6.54 (d,
J = 2.8 Hz, 1 H), 6.11 (d, J = 3.6 Hz, 1 H), 4.23 (q, J = 7.2 Hz, 2 H),
4.19 (q, J = 7.2 Hz, 2 H), 3.85 (s, 3 H), 2.87 (ABq, Δδ = 18.6 Hz,
J = 13.2 Hz, 2 H) , 2.67 (d, J = 13.2 Hz, 1 H), 2.61 (dd, J = 4.4, 4.8
Hz, 1 H), 1.83 (m, 1 H), 1.28 (t, J = 7.2 Hz, 3 H), 1.25 (t, J = 7.2 Hz,
3 H), 1.20 (m, 1 H), 0.74 (dd, J = 5.2, 5.2 Hz, 1 H).
13C NMR (100 MHz, CDCl3): δ = 172.66 171.58, 159.95, 156.76,
151.67, 132.41, 129.75, 116.15, 112.42, 109.12, 106.38, 106.13,
61.98, 61.84, 59.79, 55.40, 38.14, 36.05, 27.41, 26.87, 17.23, 14.13.
HRMS: m/z [M]+ calcd for C21H22O5 354.1467; found: 354.1458.
Dimethyl 1-(5-Pentylfuran-2-yl)bicyclo[3.1.0]hexane-3,3-dicar-
boxylate (2j)
Colorless oil; yield: 36.4 mg (86%).
1H NMR (400 MHz, CDCl3): δ = 5.89 (d, J = 3.0 Hz, 1 H), 5.84 (d,
J = 3.0 Hz, 1 H), 3.75 (s, 3 H), 3.71 (s, 3 H), 2.81 (ABq, Δδ = 25.2
Hz, J = 14.0 Hz, 2 H), 2.64 (d, J = 13.2 Hz, 2 H), 2.59 (dd, J = 13.2,
4.4 Hz, 1 H), 2.53 (t, J = 8.0 Hz, 1 H), 1.69 (m, 1 H), 1.59 (quintet,
J = 7.2 Hz, 2 H), 1.32 (m, 4 H), 1.08 (dd, J = 7.0, 6.8 Hz, 1 H), 0.89
(t, J = 6.8 Hz, 3 H), 0.59 (dd, J = 5.2, 5.2 Hz, 1 H).
HRMS: m/z [M]+ calcd for C23H26O6: 398.1729; found: 398.1722.
13C NMR (100 MHz, CDCl3): δ = 173.22, 172.12, 154.75, 154.64,
105.18, 104.39, 59.43, 53.19, 53.06, 38.36, 36.14, 31.52, 28.10,
27.82, 27.13, 26.04, 22.53, 16.34, 14.15.
Dimethyl 1-(2,3-Bifuran-5-yl)bicyclo[3.1.0]hexane-3,3-dicar-
boxylate (2f)
Colorless oil; yield: 18.7 mg (52%).
1H NMR (400 MHz, CDCl3): δ = 7.65 (s, 1 H), 7.40 (s, 1 H), 6.55
(s, 1 H), 6.26 (d, J = 3.2 Hz, 1 H), 6.05 (d, J = 2.8 Hz, 1 H), 3.76 (s,
3 H), 3.73 (s, 3 H), 2.86 (ABq, Δδ = 24.4 Hz, J = 13.6 Hz, 2 H), 2.67
(d, J = 13.6 Hz, 1 H), 2.62 (dd, J = 13.6, 4.4 Hz, 1 H), 1.77 (m, 1 H),
1.16 (dd, J = 6.8, 6.4 Hz, 1 H), 0.66 (dd, J = 5.6, 5.2 Hz, 1 H).
HRMS: m/z [M]+ calcd for C19H26O5: 334.1780; found: 334.1768.
Dimethyl 5-Methyl-1-(5-pentylfuran-2-yl)bicyclo[3.1.0]hexane-
3,3-dicarboxylate (2k)
Colorless oil; yield: 28.5 mg (61%).
13C NMR (100 MHz, CDCl3): δ = 173.15, 172.07, 155.75, 145.94,
143.42, 137.81, 118.02, 107.82, 106.00, 59.64, 53.20, 53.08, 38.44,
36.19, 36.10, 29.84, 27.22, 26.55, 16.93.
1H NMR (400 MHz, CDCl3): δ = 5.92 (d, J = 2.8 Hz, 1 H), 5.86 (d,
J = 2.8 Hz, 1 H), 3.75 (s, 3 H), 3.72 (s, 3 H), 2.84 (ABq, Δδ = 32.0
Hz, J = 14.0 Hz, 2 H), 2.72 (d, J = 13.8 Hz, 1 H), 2.55 (t, J = 8.0 Hz,
2 H), 2.42 (d, J = 13.8 Hz, 1 H), 1.61 (quintet, J = 6.8 Hz, 2 H),
1.31(m, 4 H), 1.07 (s, 3 H), 0.89 (t, J = 6.8 Hz, 3 H), 0.88 (d, J = 6.0
Hz, 1 H), 0.67 (d, J = 6.0 Hz, 1 H).
HRMS: m/z [M]+ calcd for C18H18O6: 330.1103; found: 333.1096.
trans-2-(Benzyloxy)-1-(5-phenylfuran-2-yl)bicyclo[3.1.0]hex-
ane (2g)
Colorless oil; yield: 28.8 mg (87%).
Synthesis 2013, 45, 174–182
© Georg Thieme Verlag Stuttgart · New York

PAPER
Gold(III)-Catalyzed Intramolecular Furanylation and Cyclopropanation
181
13C NMR (100 MHz, CDCl3): δ = 173.23, 172.29, 155.29, 153.21,
106.39, 105.14, 58.01, 53.17, 53.01, 42.27, 39.54, 31.46, 31.28,
31.05, 28.17, 27.79, 22.52, 20.22, 18.03, 14.15.
1H NMR (400 MHz, CDCl3): δ = 7.71 (d, J = 7.2 Hz, 2 H), 7.42 (s,
2 H), 7.39 (t, J = 7.6 Hz, 2 H), 7.30 (d, J = 7.2 Hz, 1 H), 6.68 (d, J =
3.6 Hz, 1 H), 6.66 (d, J = 3.6 Hz, 1 H), 5.75 (sext, J = 6.8 Hz, 1 H),
5.12 (d, J = 21.2 Hz, 1 H), 5.09 (d, J = 14.4 Hz, 1 H), 4.31–4.22 (m,
4 H), 3.10 (d, J = 7.6 Hz, 2 H), 1.28 (t, J = 7.2 Hz, 6 H).
HRMS: m/z [M]+ calcd for C20H28O5 348.1937; found: 348.1952.
13C NMR (100 MHz, CDCl3): δ = 119.26, 154.99, 150.71, 132.45,
130.24, 128.85, 128.10, 124.65, 124.21, 119.20, 113.23, 110.16,
106.97, 62.27, 60.30, 39.28, 14.22.
trans-2-(Benzyloxy)-4,4-dimethyl-1-(5-pentylfuran-2-yl)bicyc-
lo[3.1.0]hexane (2l)
Colorless oil; yield: 27.0 mg (65%).
1H NMR (400 MHz, CDCl3): δ = 7.32–7.23 (m, 5 H), 5.89 (d,
J = 3.0 Hz, 1 H), 5.85 (d, J = 3.0 Hz, 1 H), 4.59 (dd, J = 8.4, 8.4 Hz,
1 H), 4.48 (ABq, Δδ = 17.6 Hz, J = 12.0 Hz, 2 H), 2.55 (t, J = 7.2
Hz, 2 H), 1.76 (dd, J = 13.2, 7.2 Hz, 1 H), 1.61 (m, 2 H), 1.33 (m, 5
H), 1.19 (m, 2 H), 1.09 (s, 3 H), 1.04 (dd, J = 8.0, 6.0 Hz, 1 H), 1.00
(s, 3 H), 0.88 (t, J = 6.6 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 155.34, 154.71, 139.03, 128.34,
127.80, 127.47, 105.21, 104.66, 81.29, 71.72, 41.71, 38.53, 37.33,
31.55, 30.44, 29.97, 28.19, 27.93, 26.33, 22.56, 14.18, 11.14.
HRMS: m/z [M]+ calcd for C22H24O5: 368.1624; found: 368.1625.
Acknowledgment
Financial support was provided by a grant from the National
Research Foundation of Korea (NRF 3|201100000000663) for
financial support.
HRMS: m/z [M]+ calcd for C24H32O2: 352.2402; found: 352.2403.
Supporting Information for this article is available online at
http://www.thieme-connect.com/ejournals/toc/synthesis.SnoIufproi
m
tgioSrantnugIifoop
r
itmnatr
trans-2-(Benzyloxy)-4,4-dimethyl-1-5-[5-(2-naphthyl)furan-2-
yl]bicyclo[3.1.0]hexane (2m)
Colorless oil; yield: 60.8 mg (72%).
References
1H NMR (400 MHz, CDCl3): δ = 8.01 (s, 1 H), 7.81 (m, 3 H), 7.70
(d, J = 8.4 Hz, 1 H), 7.44 (m, 2 H), 7.27 (m, 5 H), 6.68 (d, J = 3.2
Hz, 1 H), 6.14 (d, J = 3.2 Hz, 1 H), 4.74 (t, J = 8.0 Hz, 1 H), 4.55 (s,
2 H), 1.85 (dd, J = 12.8, 7.8 Hz, 1 H), 1.50 (dd, J = 8.4, 4.8 Hz, 1
H), 1.33 (dd, J = 4.8, 4.8 Hz, 1 H), 1.25 (m, 2 H), 1.15 (s, 3 H),
1.06(s, 3 H).
13C NMR (100 MHz, CDCl3): δ = 157.48, 151.94, 138.78, 133.69,
132.48, 128.40, 128.33, 128.11, 127.83, 127.81, 127.55, 126.47,
125.67, 122.26, 121.34, 106.82, 106.57, 80.82, 71.77, 41.64, 39.22,
37.51, 30.70, 30.00, 26.31, 11.74.
(1) Patil, N. T.; Yamamoto, Y. Chem. Rev. 2008, 108, 3395.
(2) (a) Charruault, L.; Michelet, V.; Taras, R.; Gladiali, S.;
Genêt, J.-P. Chem. Commun. 2004, 850. (b) Toullec, P. Y.;
Chao, C.-M.; Chen, Q.; Gladiali, S.; Genêt, J.-P.; Michelet,
V. Adv. Synth. Catal. 2008, 350, 2401. (c) Brissy, D.;
Skander, M.; Retailleau, P.; Frison, G.; Marinetti, A.
Organometallics 2009, 28, 140. (d) Brissy, D.; Skander, M.;
Jullien, H.; Retailleau, P.; Marinetti, A. Org. Lett. 2009, 11,
2137. (e) Munõz, M. P.; Adrio, J.; Carretero, J. C.;
Echavarren, A. M. Organometallics 2005, 24, 1293.
(f) Chao, C.-M.; Vitale, M. R.; Toullec, P. Y.; Genêt, J.-P.;
Michelet, V. Chem. Eur. J. 2009, 15, 1319. (g) Chao, C.-M.;
Beltrami, D.; Toullec, P. Y.; Michelet, V. Chem. Commun.
2009, 6988.
(3) (a) Dyker, G. Angew. Chem. Int. Ed. 2000, 39, 4237; Angew.
Chem., 2000, 112, 4407 . (b) Hashmi, A. S. K. Gold Bull.
(Berlin, Ger.) 2003, 36, 3. (c) Hashmi, A. S. K. Gold Bull.
(Berlin, Ger.) 2004, 37, 51. (d) Krause, N.; Hoffmann-
Röder, A. Org. Biomol. Chem. 2005, 3, 387. (e) Hashmi, A.
S. K. Angew. Chem. Int. Ed. 2005, 44, 6990; Angew. Chem.,
2005, 117, 7150 . (f) Hashmi, A. S. K.; Hutchings, G.
Angew. Chem. Int. Ed. 2006, 45, 7896; Angew. Chem. 2006,
118, 8064 . (g) Hashmi, A. S. K. Chem. Rev. 2007, 107,
3180. (h) Früstner, A.; Davies, P. W. Angew. Chem. Int. Ed.
2007, 46, 3410; Angew. Chem. 2007, 119, 3478 . (i) Shen, C.
H. Tetrahedron 2008, 64, 3885. (j) Skouta, R.; Li, C.-J.
Tetrahedron 2008, 64, 4917. (k) Muzart, J. Tetrahedron
2008, 64, 5815. (l) Li, Z.; Brouwer, C.; He, C. Chem. Rev.
2008, 108, 3239. (m) Arcadi, A. Chem. Rev. 2008, 108,
3266.
HRMS (Cl): m/z calcd for C29H29O2: 409.2168; found: 409.2190.
Diethyl 3-Oxobicyclo[5.3.0]deca-4,6-diene-9,9-dicarboxylate
(3a)
Enynone 1a (30.1 mg, 0.1 mmol), PtCl2 (1.4 mg, 0.005 mmol),
AgSbF6 (1.8 mg, 0.005 mmol) and anhyd CH2Cl2 (1.0 mL) were
placed in a new 5 mL test tube at 0 °C. The reaction mixture was
purged with a stream of dry argon gas and stirred at r.t. for 1 h by
monitoring the reaction periodically by TLC. Upon completion, a
drop of Et3N was added to quench the reaction and the solvent was
removed under vacuum. The residue was purified by flash column
chromatography (silica gel, hexane–EtOAc, 20:1) to give the prod-
uct 3a (17.2 mg, 57%) as a colorless oil.
1H NMR (400 MHz, CDCl3): δ = 7.09 (m, 1 H), 6.25 (m, 1 H), 6.17
(m, 1 H), 4.20 (m, 4 H), 3.19 (dd, J = 17.6, 2.8 Hz, 1 H), 2.63 (m, 2
H), 2.45 (d, J = 17.2 Hz, 1 H), 2.35 (dt, J = 17.6, 6.4 Hz, 1 H), 2.04
(m, 1 H), 1.91( t, J = 13.0 Hz, 1 H), 1.26 (t, J = 7.2 Hz, 3 H), 1.23
(t, J = 7.2 Hz, 3 H).
13C NMR (100 MHz, CDCl3): δ = 194.31, 170.55, 170.52, 135.07,
132.04, 131.71, 125.33, 62.11, 62.02, 53.78, 44.07, 34.76, 30.86,
30.19, 14.11.
(4) (a) Gorin, D. J.; Toste, F. D. Nature (London, U. K.) 2007,
446, 395. (b) Witham, C. A.; Mauleon, P.; Shapiro, N. D.;
Sherry, B. D.; Toste, F. D. J. Am. Chem. Soc. 2007, 129,
5838.
HRMS: m/z [M]+ calcd for C16H20O5: 292.1311; found: 292.1316.
(E)-Diethyl 2-Allyl-2-[2-(5-phenylfuran-2-yl)vinyl]malonate
(3b)
(5) (a) Garayalde, D.; Nevado, C. ACS Catalysis 2012, 2, 1462.
(b) Butenschön, H. Angew. Chem. Int. Ed. 2008, 47, 5287.
(6) (a) Iwasawa, N.; Shido, M.; Kusama, H. J. Am. Chem. Soc.
2001, 123, 5814. (b) Kusama, H.; Funami, H.; Takaya, J.;
Iwasawa, N. Org. Lett. 2004, 6, 605. (c) Asao, N.; Sato, K.;
Yamamoto, Y. J. Org. Chem. 2005, 70, 3682. (d) Kusama,
H.; Funami, H.; Shido, M.; Hara, Y.; Takaya, J.; Iwasawa, N.
J. Am. Chem. Soc. 2005, 127, 2709. (e) Tanaka, D.; Sato, Y.;
Mori, M. Organometallics 2006, 25, 799. (f) Hildebrandt,
D.; Dyker, G. J. Org. Chem. 2006, 71, 6728. (g) Yang, C.;
Enynone 1b (37.0 mg, 0.1 mmol), AuBr3 (2 mg, 0.005 mmol), and
anhyd CH2Cl2 (1.0 mL) were placed in a new 5 mL test tube at 0 °C.
The reaction mixture was purged with a stream of dry argon gas and
stirred at r.t. for 4 h by monitoring the reaction periodically by TLC.
Upon completion, a drop of Et3N was added to quench the reaction
and the solvent was removed under vacuum. The residue was puri-
fied by flash column chromatography (silica gel, n-hexane–EtOAc,
20:1) to give the product 2b (20.0 mg, 54%) and 3b (10.0 mg, 27%)
as colorless oils. Data for 3b follow.
© Georg Thieme Verlag Stuttgart · New York
Synthesis 2013, 45, 174–182

182
C. H. Oh et al.
PAPER
(14) (a) Belting, V.; Krause, N. Org. Biomol. Chem. 2009, 7,
1221. (b) Rodríguez, A.; Moran, W. J. Tetrahedron Lett.
2011, 52, 2605.
(15) Tsuji, H.; Yamagata, K.-i.; Ueda, Y.; Nakamura, E. Synlett
2011, 1015.
(16) (a) Johansson, M. J.; Gorin, D. J.; Staben, S. T.; Toste, F. D.
J. Am. Chem. Soc. 2005, 127, 18002. (b) Moreau, X.;
Goddard, J.; Bernard, M.; Lemière, G.; López-Romero, J.
M.; Mainetti, E.; Marion, N.; Mouriès, V.; Thorimbert, S.;
Fensterbank, L.; Malacria, M. Adv. Synth. Catal. 2008, 350,
43.
(17) (a) Jiménez-Núñez, E.; Claverie, C. K.; Nieto-Oberhuber,
C.; Echavarren, A. M. Angew. Chem. Int. Ed. 2006, 45,
5451. (b) Huguet, N.; Echavarren, A. M. Synlett 2012, 23,
49.
Liu, R. Tetrahedron Lett. 2007, 48, 5887. (h) Jin, T.;
Yamamoto, Y. Org. Lett. 2008, 10, 3137. (i) Xie, Y.; Yan,
Z.; Qian, B.; Deng, W.; Wang, D.; Wu, L.; Liu, X.; Liang, Y.
Chem. Commun. 2009, 5451. (j) Patti, R. K.; Waynat, K.;
Herndon, J. Org. Lett. 2011, 13, 2848. (k) Hojo, D.; Tanaka,
K. Org. Lett. 2012, 14, 1492.
(7) (a) Oh, C. H.; Ryu, J. H.; Lee, H. I. Synlett 2007, 2337.
(b) Oh, C. H.; Lee, J. H.; Lee, S. J.; Kim, J. I.; Hong, C. S.
Angew. Chem. Int. Ed. 2008, 47, 7505; Angew. Chem. 2008,
120, 7615 . (c) Oh, C. H.; Lee, J. H.; Lee, S. M.; Yi, H. J.;
Hong, C. H. Chem. Eur. J. 2009, 15, 71. (d) Oh, C. H.; Yi, J.
H.; Lee, J. H.; Lim, D. H. Chem. Commun. 2010, 46, 3007.
(e) Oh, C. H.; Lee, S. M.; Hong, C. S. Org. Lett. 2010, 12,
1308. (f) Oh, C. H.; Tak, S. Y.; Lee, J. H.; Piao, L. H. Bull.
Korean Chem. Soc. 2011, 32, 2978.
(8) Oh, C. H.; Lee, S. J.; Lee, J. H.; Na, Y. J. Chem. Commun.
2008, 5794.
(18) (a) Kusama, H.; Ishida, K.; Funami, H.; Iwasawa, N. Angew.
Chem. Int. Ed. 2008, 47, 4903; Angew. Chem. 2008, 120:
4981 . (b) Ishida, K.; Kusama, H.; Iwasawa, N. J. Am. Chem.
Soc. 2010, 132, 8842.
(19) Kuroda, H.; Hanaki, E.; Izawa, H.; Kano, M.; Itahashi, H.
Tetrahedron 2004, 60, 1913.
(20) (a) Taniguchi, M.; Kobayashi, S.; Nakagawa, M.; Hino, T.;
Kishi, Y. Tetrahedron Lett. 1986, 27, 4763. (b) Shu, X.-Z.;
Zhao, S.-C.; Ji, K.-G.; Zheng, Z.-J.; Liu, X.-Y.; Liang, Y.-M.
Eur. J. Org. Chem. 2008, 1418.
(21) Sterochemistry between benzyloxy group and furanyl group
in 2m was unequivocally determined by observing strong
NOE in the ROESY spectrum.
(9) (a) Trost, B. M. Science (Washington, D.C.) 1991, 254,
1471. (b) Trost, B. M. Acc. Chem. Res. 1990, 23, 34.
(10) Oh, C. H.; Park, H. M.; Park, D. I. Org. Lett. 2007, 9, 1191.
(11) (a) Singh, R. P.; Foxman, B. M.; Deng, L. J. Am. Chem. Soc.
2010, 132, 9558. (b) Ouairy, C.; Michel, P.; Delpech, B.;
Crich, D.; Marazano, C. J. Org. Chem. 2010, 75, 4311.
(c) Guindon, Y.; Therien, M.; Girard, Y.; Yoakim, C. J. Org.
Chem. 1987, 52, 1680. (d) Lisphutz, B. H. Chem. Rev. 1986,
86, 795. (e) Goldsmith, D. J.; Kennedy, E.; Campbell, R. G.
J. Org. Chem. 1975, 40, 3571.
(12) Imagawa, H.; Kurisaki, T.; Nishizawa, M. Org. Lett. 2004,
6, 3679.
(13) (a) Picquet, M.; Bruneau, C.; Dixneuf, P. H. Tetrahedron
1999, 55, 3937. (b) Han, X.; Widenhoefer, R. A. J. Org.
Chem. 2004, 69, 1738. (c) Saito, A.; Enomoto, Y.;
Hanzawa, Y. Tetrahedron Lett. 2011, 52, 4996.
(22) Paterson, I.; Paquet, T. Org. Lett. 2010, 12, 2158.
(23) Wu, J. Y.; Stanzl, B. N.; Ritter, T. J. Am. Chem. Soc. 2010,
132, 13214.
Synthesis 2013, 45, 174–182
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