C(sp3)-C(sp3) bond breaking in methylenecyclopropanes involving a Aui/AuIII catalytic cycle

Article abstract of DOI:10.1002/ejoc.201000765

Gold(I) can catalyze the diacetoxylation of methylenecyclopropanes to produce the corresponding diacetoxylated products in moderate to good yields in acetic acid in the presence of iodosobenzene diacetate via C-C bond breaking under mild condition.

Full text of DOI:10.1002/ejoc.201000765

FULL PAPER
DOI: 10.1002/ejoc.201000765
C(sp3)–C(sp3) Bond Breaking in Methylenecyclopropanes Involving a AuI/AuIII
Catalytic Cycle
Di-Han Zhang,[a] Lun-Zhi Dai,[a] and Min Shi*[a]
Keywords: Gold / C–C bond activation / Methylenecyclopropanes
Gold(I) can catalyze the diacetoxylation of methylenecyclo- of iodosobenzene diacetate via C–C bond breaking under
propanes to produce the corresponding diacetoxylated prod-
ucts in moderate to good yields in acetic acid in the presence
mild condition.
Introduction
Results and Discussion
Initial studies using (diphenylmethylene)cyclopropane
(1a) as the substrate were aimed at determining the reaction
outcomes and subsequently optimizing the reaction condi-
tions (0.2 mmol). The results of these experiments are sum-
marized in Table 1. We found that the diacetoxylated prod-
uct 2a was obtained in 62% yield using (Ph3P)AuCl as the
catalyst (5 mol-%) in the presence of PhI(OAc)2 (1.2 equiv.)
in acetic acid (HOAc) at 80 °C (Table 1, entry 1). Using
NaAuCl4·2H2O or AuCl3 as the catalyst afforded 2a in 50%
and 65% yield, respectively under identical conditions
(Table 1, entries 2 and 3). In the presence of (Me3P)AuCl
or (IPr)AuCl, 2a could be also obtained in 67% and 64%
yield, respectively (Table 1, entries 4 and 5). Adding silver
salts did not improve the reaction outcomes (Table 1, en-
tries 6–9). Further examination of solvent and temperature
effects revealed that using (Me3P)AuCl (5 mol-%) as the
catalyst produced 2a in 76% yield in HOAc at 60 °C in the
presence of PhI(OAc)2 (1.2 equiv.) (Table 1, entry 18),
which serves as the optimal conditions for the diacetoxyl-
ation of 1a and other organic solvents such as CH2Cl2,
CH3CN, tetrahydrofuran (THF), toluene, methanol and
1,2-dichloroethane (DCE) or Ac2O did not facilitate the
formation of 2a (Table 1, entries 10–16 and 17–20). More-
over, adding PhI(OAc)2 (2.2 equiv.) into the reaction system
afforded 2a in 77% yield at 60 °C in HOAc in the presence
of (Me3P)AuCl (5 mol-%), indicating that the yield could
not receive an evident improvement even using large excess
amount of PhI(OAc)2 (Table 1, entry 21). The control ex-
periments have also indicated that no reaction occurs in the
absence of gold catalyst or iodosobenzene diacetate.
Gold salts and complexes have emerged in the past few
years as powerful catalysts for electrophilic activation of
carbon-carbon multiple bonds toward a variety of nucleo-
philes.[1] Generally, this type of reaction relies on the inter-
action of the gold catalysts with the π-bonds of alkenes,
alkynes, and allenes. Recently, an unprecedented gold-cata-
lyzed oxidative cross-coupling of propargylic acetates and
arylboronic acid has been developed from AuI and AuIII
catalytic cycles in the presence of oxidants such as Se-
lectfluor, leading to a one-step synthesis of α-arylenones.[2]
This interesting finding opens up a new perspective field for
the gold-catalyzed organic reactions.
The introduction of strained small-ring systems as mo-
lecular building blocks has drawn increasing attention be-
cause the relief of ring strain can provide a potent thermo-
dynamic driving force. Due to their inherent ring strains,
interesting preparative aspects and the applications specific
to these ring compounds have been developed. Since the
first example of gold-catalyzed transformation of cyclopro-
pane was reported by Thomas in 1976,[3] the gold-catalyzed
reactions using strained small rings have increased rapidly.
Such systems include cyclopropane, cyclopropene, oxirane
and aziridine and others. Previously, we reported the diace-
toxylation of methylenecyclopropanes (MCPs)[4] via a PdII/
PdIV catalytic cycle under mild conditions.[4l] In this paper,
we wish to report a novel C–C bond breaking reaction of
MCPs of type 1, a kind of highly strained small rings, cata-
lyzed by gold in the presence of oxidant such as iodosoben-
zene diacetate [PhI(OAc)2], leading to diacetoxylation of
methylenecyclopropanes under mild conditions.
With these optimal conditions in hand, we next exam-
ined a variety of MCPs 1 in this reaction and the results of
these experiments are shown in Table 2. As can be seen
from Table 2, as for various diarylmethylenecyclopropanes
in which both R1 and R2 are aromatic groups, the corre-
sponding diacetoxylated products 2b–2k could be obtained
in 40–83% yields within 16 h under the standard condi-
[a] State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences,
354 Fenglin Road, Shanghai 200032, China
Fax: +86-21-64166128
E-mail: Mshi@mail.sioc.ac.cn
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201000765.
View this journal online at
wileyonlinelibrary.com
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Eur. J. Org. Chem. 2010, 5454–5459

Gold-Catalytic Bond Breaking in Methylenecyclopropanes
Table 1. Optimization of the reaction conditions.
Table 2. (Me3P)AuCl-catalyzed diacetoxylation of various MCPs 1
under the optimized conditions.
Entry[a] Catalyst
Solvent
T [°C]
Yield [%][b], 2a
Entry[a]
1, R1/R2
Yield [%][b], 2
1
(Ph3P)AuCl
HOAc
HOAc
HOAc
HOAc
HOAc
80
80
80
80
80
80
80
80
62
50
65
67
64
64
26
56
complex
complex
complex
complex
complex
complex
trace
complex
68
76
72
71
77
1
2
3
4
5
6
7
8
1b, 4-CH3C6H4/4-CH3C6H4
1c, 4-FC6H4/4-FC6H4
1d, 4-ClC6H4/4-ClC6H4
1e, 4-BrC6H4/4-BrC6H4
1f, 3-CF3C6H4/4-CH3C6H4
1g, 2,4-F2C6H3/4-CH3C6H4
1h, 4-ClC6H4/4-CH3C6H4
1i, 4-BrC6H4/4-CH3C6H4
1j, 2,5-(CH3)2C6H3/C6H5
1k, 4-CH3C6H4/C6H5
1l, 4-CH3OC6H4/H
2b, 65
2c, 85
2d, 80
2e, 74
2f, 76
2g, 51
2h, 78
2i, 57
2j, 40
2k, 46
2l, 54
2m, 77
2n, 92
2o, 99
2p, complex
2
3
NaAuCl4·2H2O
AuCl3
4
5
(Me3P)AuCl
(IPr)AuCl
6[c]
7[c]
8[c]
9[c]
10
11
12
13
14
15
16
17
18
19
20
21[d]
(Me3P)AuCl/AgOAc HOAc
(Me3P)AuCl/AgOTf
(Me3P)AuCl/AgBF4
HOAc
HOAc
(Me3P)AuCl/AgSbF6 HOAc
80
reflux
9
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
(Me3P)AuCl
CH2Cl2
CH3CN 80
THF
toluene
MeOH
DCE
10
11
12
13
14
15
reflux
80
reflux
80
80
70
60
50
40
1m, 2-CH3OC6H4/H
1n, 2,4-(CH3O)2C6H3/H
1o, 3,4,5-(CH3O)3C6H2/H
1p,
Ac2O
HOAc
HOAc
HOAc
HOAc
HOAc
16
1q, C6H5/CH3
2q, complex
[a] All reactions were carried out using 1 (0.2 mmol), PhI(OAc)2
(1.2 equiv.) in the presence of (Me3P)AuCl (5 mol-%) in HOAc
(1.0 mL) at 60 °C for 16 h. [b] Isolated yield.
60
[a] All reactions were carried out using 1 (0.2 mmol), PhI(OAc)2
(1.2 equiv.) in the presence of catalyst (5 mol-%) in various solvents
(1.0 mL) otherwise specified. [b] Isolated yield. [c] 10 mol-% of Ag
salt was added. [d] PhI(OAc)2 (2.2 equiv.) was added.
tions. The electronic properties of the substituents on their
benzene rings significantly influenced the reaction out-
comes (Table 2, entries 1–10). For MCPs having electron-
withdrawing groups on the benzene rings, the products 2
could be obtained in good to high yields (Table 2, entries 2,
3 and 7). Furthermore, as for unsymmetrical MCPs 1l–1o,
Scheme 1. Intramolecular rearrangement of MCPs 1r and 1s under
the standard conditions.
in which R1 is an aromatic group and R2 is a hydrogen AuCl showed a sharp signal at δ = 33.1 ppm in CDCl3 (see
atom, the reactions also proceeded smoothly to give the Figure S1 in the Supporting Information). Further exami-
corresponding diacetoxylated products 2l–2o in 54–99% nation of the 31P NMR spectrum revealed that upon heat-
yields under the standard conditions (Table 2, entries 11– ing (Ph3P)AuCl in HOAc at 80 °C for 10 h did not alter the
14). Only in the cases of aliphatic MCP 1p and unsymmetri- catalyst since the signal of (Ph3P)AuCl was observed at δ =
cal MCP 1q in which R1 is an aromatic group and R2 is a 32.8 ppm in CDCl3 (see Figure S2 in the Supporting Infor-
methyl group, complex product mixtures were formed un- mation). Interestingly, if measuring the 31P NMR spectrum
der the standard conditions (Table 2, entries 15 and 16). of (Ph3P)AuCl under the standard reaction conditions [in
The product structures of 2a–2o were determined by NMR HOAc with PhI(OAc)2 and MCP 1 at 60 °C for 2 h and
spectroscopic data, MS, and HRMS (see Supporting Infor- 10 h], the 31P NMR spectrum showed a new signal at δ =
mation).
33.7 ppm and 33.8 ppm in CDCl3, suggesting that (Ph3P)-
On the other hand, in the case of MCPs 1r and 1s, in AuCl has been changed during the reaction (see Figure S3
which both R1 and R2 are aromatic rings with electron- and Figure S4 in the Supporting Information).[6]
donating groups, the reaction produced the corresponding
The MALDI-MS spectrum obtained from the crude re-
intramolecular rearrangement products 3a in 91% yield and action mixture of (Ph3P)AuCl (5 mol-%) with 1a
3b as two isomeric mixtures in 51% yield, respectively, (0.1 mmol) and PhI(OAc)2 (1.2 equiv.) in HOAc under the
rather than the diacetoxylated products under the standard standard conditions after a short period showed a cluster
conditions, presumably due to the easier 1,2-migration of at m/z 518.0, which might be attributed to the gold species
electron-rich aromatic rings (Scheme 1).[5]
[(C6H5)3PAu(OAc)]+ (see Supporting Information). More-
To verify the active catalytic species, several 31P NMR over, using [(4-FC6H4)3]PAuCl instead of (Ph3P)AuCl under
measurements were conducted to detect the real active cata- the same reaction conditions, a similar cluster at m/z 572.0
lytic species. The 31P NMR spectrum of a sample of (Ph3P)- was observed, which was attributed to the corresponding
Eur. J. Org. Chem. 2010, 5454–5459
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5455

D.-H. Zhang, L.-Z. Dai, M. Shi
FULL PAPER
gold species [(4-FC6H4)3PAu(OAc)]+ (see Supporting Infor-
mation). This result further suggests that a (R3P)AuOAc
species exists in this catalytic reaction system.
Another stoichiometric experiment using a LAuOAc spe-
cies, which was generated from Ph3PAuCl and AgOAc, as
the catalyst was carried out to further verify the active spe-
cies (Scheme 2). It was found that in the absence of
PhI(OAc)2 or HOAc, no reaction occurred in DCE and
adding 1.2 equiv. of PhI(OAc)2 and 0.3 mL of HOAc into
the reaction system afforded 2a in 47% yield at 60 °C if
using 1a as substrate (Scheme 2). These results suggest that
the acetoxylated AuI species might be the real active species
in this reaction and PhI(OAc)2 as well as HOAc are essen-
tial in this interesting transformation.
Scheme 3. Control experiments of MCP 1a with iodosobenzene di-
carboxylates under the standard conditions.
A plausible mechanism for the formation of these diacet-
oxylated derivatives 2 is tentatively outlined in Scheme 4 on
the basis of above spectroscopic data and the control ex-
periments. AuI complex first coordinates to methylenecyclo-
propane 1 to give intermediate A.[2] There might be an equi-
librium between the intermediate A and intermediate B in
HOAc at 60 °C,[1s] in which intermediate B is attacked by
AcO– from LAuOAc to afford intermediate C. The interme-
diate C generates intermediate D via allylic rearrangement,
which undergoes oxidative addition with PhI(OAc)2 to pro-
vide AuIII intermediate E.[8] The reductive elimination of
intermediate E produces diacetoxylated product 2 and gen-
erates AuI species F [LAuOAc]. The AuI complex F then
coordinates to methylenecyclopropane 1 to give intermedi-
ate B again, which produces intermediate C via ring-open-
ing process with AcO– and completes the catalytic cycle.
Scheme 2. (Ph3P)AuOAc-catalyzed diacetoxylation of MCP 1a.
On the other hand, to determine the coordination
pattern of AuI with MCP 1, 13C NMR spectroscopic mea-
surements were conducted to verify whether AuI complex
coordinates to the double bond or the cyclopropane. The
13C NMR spectrum of 1a showed olefinic carbon signals at
δ = 129.943 and 124.345 ppm as well as cyclopropyl carbon
signal at δ = 3.540 ppm in CDCl3, respectively (see Figure
S5 in the Supporting Information). Interestingly, if measur-
ing the 13C NMR spectrum of the mixture of 1a (0.1 mmol)
with (Ph3P)AuCl (0.1 mmol) and AgOAc (0.1 mmol) in
CDCl3 at room temperature after 20 h, the 13C NMR spec-
trum showed olefinic carbon signals at δ = 129.812 and
124.302 ppm as well as cyclopropyl carbon signal at δ =
3.463 ppm, respectively, indicating a relatively obvious up-
field shift with ∆δ = 0.131 ppm at the olefinic carbon. These
results may indicate that AuI such as (Ph3P)AuOAc can be
potentially coordinated by olefinic moiety in MCPs, al-
though the observed chemical shift differences are small.
Moreover, as shown in Scheme 3, we found that if using
iodosobenzene dipivalate to replace PhI(OAc)2 in this reac-
tion using 1a as substrate, 2a could still be produced in 85%
yield under the standard conditions, suggesting that the
carboxylate moiety of iodosobenzene dicarboxylate is ex-
changeable with the employed carboxylic acid solvent and
acetic acid is involved in the initial stage of this reaction.[7]
Utilizing PhI(OAc)2 in propionic acid (CH3CH2COOH)
provided dipropionyloxylated product 4a in 87% yield
(Scheme 3). We also confirmed that 2a could not be trans-
Scheme 4. A plausible reaction mechanism.
In summary, we have reported in this paper an interesting
formed into 4a in propionic acid under the standard condi- gold-catalyzed diacetoxylation of methylenecyclopropanes
tions.
in moderate to good yields in the presence of iodosobenz-
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Gold-Catalytic Bond Breaking in Methylenecyclopropanes
1
cm–1. H NMR (CDCl3, 400 MHz, TMS): δ = 2.08 (s, 3 H, CH3),
ene diacetate via C–C bond breaking under mild condi-
tions. The reaction is considered to proceed via a AuI/AuIII
catalytic cycle. Clarification of the reaction mechanism and
further application of this chemistry are in progress.
2.09 (s, 3 H, CH3), 2.34 (s, 3 H, CH3), 4.60 (s, 2 H, CH2), 4.71 (s,
2 H, CH2), 7.02 (d, J = 8.0 Hz, 2 H, Ar), 7.14 (d, J = 8.0 Hz, 2 H,
Ar), 7.32 (d, J = 7.6 Hz, 1 H, Ar), 7.44 (dd, J = 7.6, J = 8.0 Hz, 1
H, Ar), 7.48 (s, 1 H, Ar), 7.55 (d, J = 8.0 Hz, 1 H, Ar) ppm. 13C
NMR (CDCl3, 100 MHz, TMS): δ = 20.7, 20.8, 21.1, 62.6, 63.0,
123.9 (q, J = 270.8 Hz), 124.6 (q, J = 3.8 Hz), 125.9 (q, J = 3.8 Hz),
128.3, 128.7, 129.1, 130.6 (q, J = 32.6 Hz), 132.5, 136.6, 138.2,
141.3, 147.7, 170.6, 170.7 ppm. 19F NMR (CDCl3, 376 MHz,
CF3COOH): δ = –62.65 (s) ppm. MS (EI): m/z (%) = 406 (1.47)
[M+], 304 (10.78), 289 (31.75), 286 (100.00), 271 (18.19), 259 (5.00),
235 (5.11), 217 (12.03), 203 (7.58), 183 (10.46), 159 (3.62), 129
(5.66), 115 (3.62), 105 (5.20), 91 (3.37), 77 (1.68), 43 (39.70). HRMS
(EI) Calcd. for C22H21O4F3 (M+): 406.1392; found 406.1407.
Experimental Section
General Remarks: Melting points were determined on a digital
1
melting point apparatus. H and 13C NMR spectra were recorded
at 300 (400) and 75 (100) MHz, respectively. Mass and HRMS
spectra were recorded by EI method. The employed solvents were
dry up by the standard procedures. Commercially obtained rea-
gents were used without further purification. All reactions were
monitored by TLC with silica gel coated plates. Flash column
chromatography was carried out using 300–400 mesh silica gel at
increased pressure.
Compound 2g: Yield 38 mg, 51%. A colorless oil. IR (CH Cl ): ν
˜
2
2
= 2925, 1743, 1501, 1378, 1234, 1140, 1024, 969, 817, 513 cm–1. 1H
NMR (CDCl3, 400 MHz, TMS): δ = 2.04 (s, 3 H, CH3), 2.08 (s, 3
H, CH3), 2.33 (s, 3 H, CH3), 4.60 (s, 2 H, CH2), 4.73 (s, 2 H, CH2),
6.79–6.88 (m, 2 H, Ar), 7.04 (d, J = 8.0 Hz, 2 H, Ar), 7.12 (q, J =
8.0 Hz, 3 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ =
20.76, 20.86, 21.1, 62.2, 62.7, 104.2 (t, J = 25.8 Hz), 111.4 (dd, J =
3.1, J = 20.5 Hz), 124.2 (d, J = 19.8 Hz), 128.7, 129.0, 130.1, 131.8
(dd, J = 5.3, J = 9.1 Hz), 136.2, 138.0, 140.6, 159.4 (dd, J = 12.9,
J = 248.1 Hz), 162.6 (dd, J = 12.1, J = 248.8 Hz), 170.64, 170.66
ppm. 19F NMR (CDCl3, 376 MHz, CF3COOH): δ = –109.88 to
–109.79 (m), –109.67 to –109.60 (m) ppm. MS (EI): m/z (%) = 374
(1.51) [M+], 314 (4.19), 272 (9.62), 257 (39.69), 254 (100.00), 239
(31.32), 227 (8.60), 201 (5.14), 151 (13.22), 127 (8.45), 115 (3.53),
105 (8.39), 91 (3.53), 77 (1.86), 43 (41.82). HRMS (EI) Calcd. for
C21H20O4F2 (M+): 374.1330; found 374.1327.
General Procedure for the Reaction of MCPs Under the Standard
Reaction Conditions: Under ambient atmosphere, methylenecypro-
panes 1 (MCPs) (0.20 mmol, 1.0 equiv.), PhI(OAc)2 (0.24 mmol,
1.2 equiv.), (Me3P)AuCl (0.01 mmol, 5 mol-%), and HOAc
(1.00 mL) were added into an Schlenk tube. The reaction mixture
was stirred at 60 °C until the reaction completed. Then, the solvent
was removed under reduced pressure and the residue was purified
by a flash column chromatography (SiO2) to give the corresponding
products 2 in moderate to good yields.
1
Compound 2a: Yield 49 mg, 76%. This is a known compound. H
NMR (CDCl3, 300 MHz, TMS): δ = 2.08 (s, 6 H, CH3), 4.69 (s, 4
H, CH2), 7.14–7.16 (m, 4 H, Ar), 7.26–7.35 (m, 6 H, Ar) ppm. 13C
NMR (CDCl3, 100 MHz, TMS): δ = 20.9, 62.8, 127.2, 127.8, 128.2,
129.2, 140.3, 148.8, 170.7 ppm.
Compound 2h: Yield 57 mg, 78%. A colorless oil. IR (CH Cl ): ν
˜
2
2
= 3025, 2925, 1743, 1488, 1378, 1361, 1236, 1091, 1016, 970, 819,
513 cm–1. 1H NMR (CDCl3, 300 MHz, TMS): δ = 2.08 (s, 6 H,
CH3), 2.34 (s, 3 H, CH3), 4.66 (s, 2 H, CH2), 4.68 (s, 2 H, CH2),
7.00 (d, J = 7.8 Hz, 2 H, Ar), 7.07–7.14 (m, 4 H, Ar), 7.29 (d, J =
7.8 Hz, 2 H, Ar) ppm. 13C NMR (CDCl3, 75 MHz, TMS): δ =
20.9, 21.2, 62.8, 62.9, 127.4, 128.4, 129.0, 129.1, 130.6, 133.8, 137.0,
138.0, 138.9, 147.6, 170.7 ppm. MS (EI): m/z (%) = 372 (0.25) [M+],
252 (10.43), 217 (24.15), 203 (6.13), 189 (3.55), 149 (3.84), 129
(5.05), 115 (4.63), 105 (4.68), 84 (6.75), 71 (8.99), 57 (12.38), 43
(100.00). HRMS (EI) Calcd. for C21H21O4Cl (M+): 372.1128;
found 372.1126.
1
Compound 2b: Yield 46 mg, 65%. This is a known compound. H
NMR (CDCl3, 400 MHz, TMS): δ = 2.08 (s, 6 H, CH3), 2.33 (s, 6
H, CH3), 4.69 (s, 4 H, CH2), 7.02 (d, J = 8.4 Hz, 4 H, Ar), 7.11 (d,
J = 8.4 Hz, 4 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ
= 20.9, 21.2, 63.1, 126.4, 128.8, 129.2, 137.60, 137.65, 149.0, 170.8
ppm.
1
Compound 2c: Yield 61 mg, 85%. This is a known compound. H
NMR (CDCl3, 400 MHz, TMS): δ = 2.08 (s, 6 H, CH3), 4.66 (s, 4
H, CH2), 7.00–7.05 (m, 4 H, Ar), 7.09–7.13 (m, 4 H, Ar) ppm. 13C
NMR (CDCl3, 100 MHz, TMS): δ = 20.8, 62.7, 115.3 (d, J =
21.3 Hz), 127.9, 131.0 (d, J = 7.6 Hz), 136.12, 136.15, 146.7, 162.4
(d, J = 246.5 Hz), 170.6 ppm.
Compound 2i: Yield 47 mg, 57%. A light yellow oil. IR (CH2Cl2):
ν = 2925, 2855, 1743, 1485, 1378, 1236, 1023, 1011, 970, 820, 508
˜
1
Compound 2d: Yield 63 mg, 80%. This is a known compound. H
1
cm–1. H NMR (CDCl3, 400 MHz, TMS): δ = 2.08 (s, 6 H, CH3),
NMR (CDCl3, 400 MHz, TMS): δ = 2.08 (s, 6 H, CH3), 4.66 (s, 4
H, CH2), 7.07 (d, J = 8.8 Hz, 4 H, Ar), 7.30 (d, J = 8.8 Hz, 4 H,
Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ = 20.8, 62.6,
128.6, 130.6, 134.2, 138.3, 146.3, 170.6 ppm.
2.33 (s, 3 H, CH3), 4.66 (s, 2 H, CH2), 4.68 (s, 2 H, CH2), 7.00 (t,
J = 8.8 Hz, 4 H, Ar), 7.12 (d, J = 8.0 Hz, 2 H, Ar), 7.44 (d, J =
8.0 Hz, 2 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ =
20.8, 21.1, 62.7, 62.9, 122.0, 127.5, 129.0, 129.1, 130.9, 131.3, 136.9,
137.9, 139.4, 147.6, 170.6, 170.7 ppm. MS (EI): m/z (%) = 418
(1.73) [M+ + 2], 416 (1.79) [M+], 316 (4.85), 315 (5.69), 298 (35.74),
296 (35.26), 283 (8.84), 235 (19.27), 217 (100.00), 206 (45.86), 203
(27.71), 191 (14.52), 189 (14.96), 178 (7.72), 165 (5.86), 129 (4.69),
115 (6.08), 105 (5.67), 91 (3.82), 43 (46.07). HRMS (EI) Calcd. for
C21H21O4Br (M+): 416.0623; found 416.0630.
Compound 2e: Yield 72 mg, 74%. A colorless oil. IR (CH Cl ): ν
˜
2
2
= 2926, 1743, 1487, 1378, 1235, 1071, 1024, 1011, 971, 824, 727
cm–1. H NMR (CDCl3, 400 MHz, TMS): δ = 2.08 (s, 6 H, CH3),
1
4.65 (s, 4 H, CH2), 7.01 (d, J = 8.8 Hz, 4 H, Ar), 7.46 (d, J =
8.8 Hz, 4 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ =
20.8, 62.5, 122.4, 128.6, 130.8, 131.5, 138.7, 146.2, 170.5 ppm. MS
(EI): m/z (%) = 482 (0.60) [M+ + 2], 480 (0.29) [M+], 364 (6.56),
362 (13.50), 301 (12.44), 299 (12.80), 283 (31.94), 281 (31.27), 272
(10.80), 270 (11.60), 203 (17.73), 202 (12.28), 189 (10.56), 101
(3.51), 43 (100.00). HRMS (EI) Calcd. for C20H18O4Br2 (M+):
479.9572; found 479.9576.
1
Compound 2j: Yield 28 mg, 40%. This is a known compound. H
NMR (CDCl3, 400 MHz, TMS): δ = 2.03 (s, 3 H, CH3), 2.07 (s, 3
H, CH3), 2.08 (s, 3 H, CH3), 2.30 (s, 3 H, CH3), 4.50 (d, J =
12.0 Hz, 1 H, CH2), 4.56 (d, J = 12.0 Hz, 1 H, CH2), 4.77 (d, J =
12.4 Hz, 1 H, CH2), 4.81 (d, J = 12.4 Hz, 1 H, CH2), 6.95 (s, 1 H,
Ar), 6.98–7.05 (m, 2 H, Ar), 7.16–7.19 (m, 2 H, Ar), 7.24–7.31 (m,
3 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ = 19.2, 20.8,
Compound 2f: Yield 63 mg, 76%. A light yellow oil. IR (CH2Cl2):
ν = 3025, 2927, 1744, 1379, 1336, 1300, 1239, 1128, 1023, 806, 706
˜
Eur. J. Org. Chem. 2010, 5454–5459
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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5457

D.-H. Zhang, L.-Z. Dai, M. Shi
FULL PAPER
20.9, 62.3, 63.0, 127.7, 128.1, 128.6, 129.0, 129.6, 130.3, 132.4,
135.0, 139.1, 139.6, 147.8, 170.76, 170.82 ppm.
2 H, CH2), 3.74 (s, 3 H, CH3), 3.78 (s, 3 H, CH3), 6.75–6.79 (m, 4
H, Ar), 7.14 (dd, J = 2.0, J = 6.8 Hz, 2 H, Ar), 7.79 (dd, J = 2.4,
J = 6.8 Hz, 2 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ
= 15.5, 34.0, 55.15, 55.26, 113.2, 114.4, 128.8, 129.5, 131.8, 133.4,
158.1, 162.5, 198.6 ppm. MS (EI): m/z (%) = 283 (21.07) [M+ + 1],
282 (100.00) [M+], 267 (9.12), 147 (19.94), 135 (84.52), 115 (8.15),
92 (10.32), 84 (8.00), 77 (16.61). HRMS (EI) Calcd. for C18H18O3
(M+): 282.1256; found 282.1258.
1
Compound 2k: Yield 31 mg, 46%. This is a known compound. H
NMR (CDCl3, 300 MHz, TMS): δ = 2.077 (s, 3 H, CH3), 2.083 (s,
3 H, CH3), 2.33 (s, 3 H, CH3), 4.69 (s, 2 H, CH2), 4.71 (s, 2 H,
CH2), 7.03 (d, J = 8.1 Hz, 2 H, Ar), 7.11–7.16 (m, 4 H, Ar), 7.26–
7.32 (m, 3 H, Ar) ppm. 13C NMR (CDCl3, 75 MHz, TMS): δ =
20.9, 21.1, 62.96, 62.99, 126.8, 127.7, 128.1, 128.8, 129.1, 129.2,
137.4, 137.6, 140.5, 148.9, 170.8 ppm.
Compounds 3b and 3bЈ (3.00:0.25 mixture of the two isomers): Yield
27 mg, 51%. A colorless oil. IR (CH Cl ): ν = 3004, 2955, 2836,
˜
2
2
Compound 2l: Yield 30 mg, 54%. A green oil. IR (CH Cl ): ν =
˜
2
2
1671, 1608, 1514, 1278, 1175, 1032, 992, 828, 560 cm–1. H NMR
(CDCl3, 400 MHz, TMS): δ = 1.26 (3b and 3bЈ, dd, J = 4.0, J =
6.8 Hz, 2.17 H, CH2), 1.56 (3b or 3bЈ, dd, J = 4.0, J = 6.8 Hz, 0.17
H, CH2), 1.60 (4bЈ or 4b, dd, J = 4.0, J = 6.8 Hz, 2 H, CH2), 2.26
(3b or 3bЈ, s, 0.25 H, CH3), 2.29 (3bЈ or 3b, s, 3 H, CH3), 3.73 (3b
or 3bЈ, s, 3 H, OCH3), 3.76 (3bЈ or 3b, s, 0.25 H, OCH3), 6.74–6.78
(3b and 3bЈ, m, 2.17 H, Ar), 7.05–7.15 (3b and 3bЈ, m, 4.33 H, Ar),
7.66–7.69 (3b or 3bЈ,m, 2 H, Ar), 7.79–7.83 (3bЈ or 3b, m, 0.17 H,
Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ = 15.5, 15.8, 21.5,
34.3, 55.1, 113.2, 113.9, 127.3, 127.4, 128.6, 129.0, 129.3, 129.6,
130.2, 131.9, 133.2, 134.3, 137.4, 142.5, 158.1, 200.0 ppm. MS (EI):
m/z (%) = 267 (20.99) [M+ + 1], 266 (100.00) [M+], 251 (8.94), 147
(34.96), 119 (48.42), 115 (11.03), 91 (33.30), 77 (5.75), 65 (9.92).
HRMS (EI) Calcd. for C18H18O2 (M+): 266.1307; found 266.1306.
1
2934, 2839, 1736, 1608, 1512, 1371, 1235, 1178, 1026, 834, 506
1
cm–1. H NMR (CDCl3, 400 MHz, TMS): δ = 2.10 (s, 3 H, CH3),
2.11 (s, 3 H, CH3), 3.82 (s, 3 H, OCH3), 4.74 (d, J = 0.8 Hz, 2 H,
CH2), 4.80 (s, 2 H, CH2), 6.79 (s, 1 H, CH), 6.89 (d, J = 8.8 Hz, 2
H, Ar), 7.20 (d, J = 8.8 Hz, 2 H, Ar) ppm. 13C NMR (CDCl3,
100 MHz, TMS): δ = 20.88, 20.94, 55.2, 60.8, 66.7, 113.8, 127.7,
129.2, 130.1, 134.4, 159.3, 170.7, 170.8 ppm. MS (EI): m/z (%) =
278 (2.02) [M+], 176 (4.67), 175 (6.02), 147 (14.82), 131 (3.40), 115
(8.20), 103 (5.62), 91 (5.99), 77 (5.40), 58 (10.18), 43 (100.00).
HRMS (EI) Calcd. For C15H18O5 (M+): 278.1154; found 278.1152.
Compound 2m: Yield 43 mg, 77%. A colorless oil. IR (CH Cl ): ν
˜
2
2
= 2936, 1743, 1602, 1493, 1464, 1372, 1288, 1230, 1028, 757, 513
1
cm–1. H NMR (CDCl3, 400 MHz, TMS): δ = 2.01 (s, 3 H, CH3),
2.11 (s, 3 H, CH3), 3.83 (s, 3 H, OCH3), 4.53 (d, J = 12.8 Hz, 1 H,
CH2), 4.59 (d, J = 12.8 Hz, 1 H, CH2), 5.26 (d, J = 17.2 Hz, 2 H,
CH2), 6.72 (s, 1 H, CH), 6.88 (dd, J = 8.0, J = 1.2 Hz, 1 H, Ar),
6.93–6.97 (m, 1 H, Ar), 7.26–7.30 (m, 1 H, Ar), 7.33 (dd, J = 7.6,
J = 1.6 Hz, 1 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ
= 20.7, 21.0, 55.5, 64.2, 69.5, 110.7, 114.9, 120.5, 126.3, 127.3,
129.3, 141.9, 156.6, 169.6, 170.5 ppm. MS (EI): m/z (%) = 278
(0.24) [M+], 176 (5.35), 175 (3.21), 159 (5.91), 158 (4.58), 144
(12.65), 135 (8.62), 131 (5.09), 116 (7.86), 115 (7.14), 91 (6.35), 77
(8.11), 58 (6.67), 43 (100.00). HRMS (EI) Calcd. For C15H18O5
(M+): 278.1154; found 278.1155.
Compound 4a: Yield 61 mg, 87%. A white solid. Mp: 91–93 °C. IR
(CH Cl ): ν = 2968, 1738, 1462, 1173, 1004, 774, 709, 507 cm–1.
˜
2
2
1H NMR (CDCl3, 400 MHz, TMS): δ = 1.15 (t, J = 7.6 Hz, 6 H,
CH3), 2.36 (q, J = 7.6 Hz, 4 H, CH2), 4.70 (s, 4 H, CH2), 7.15 (d,
J = 6.4 Hz, 4 H, Ar), 7.26–7.32 (m, 6 H, Ar) ppm. 13C NMR
(CDCl3, 100 MHz, TMS): δ = 9.1, 27.5, 62.8, 127.5, 127.8, 128.1,
129.2, 140.4, 148.5, 174.1 ppm. MS (EI): m/z (%) = 352 (0.52) [M+],
278 (0.95), 221 (11.27), 204 (100.00), 193 (12.48), 178 (9.58), 165
(6.56), 115 (14.60), 91 (4.58), 57 (21.76). HRMS (EI) Calcd. for
C22H24O4 (M+): 352.1675; found 352.1671.
Supporting Information (see also the footnote on the first page of
this article): 1H NMR and 13C NMR spectroscopic and analytic
data of the compounds 2, 3 and 4a are included.
Compound 2n: Yield 56 mg, 92%. A yellow oil. IR (CH Cl ): ν =
˜
2
2
2942, 1740, 1609, 1504, 1464, 1370, 1233, 1028, 963, 834, 522 cm–1.
1H NMR (CDCl3, 400 MHz, TMS): δ = 2.08 (s, 3 H, CH3), 2.10
(s, 3 H, CH3), 3.81 (s, 3 H, OCH3), 3.82 (s, 3 H, OCH3), 4.76 (s, 4
H, CH2), 6.45–6.49 (m, 2 H, Ar), 6.86 (s, 1 H, CH), 7.10 (d, J =
8.0 Hz, 1 H, Ar) ppm. 13C NMR (CDCl3, 100 MHz, TMS): δ =
20.9, 21.0, 55.35, 55.40, 61.2, 66.7, 98.4, 104.0, 117.0, 129.2, 130.2,
130.6, 158.4, 161.0, 170.8, 170.9 ppm. MS (EI): m/z (%) = 308
(6.18) [M+], 239 (3.19), 205 (13.44), 189 (24.93), 188 (26.33), 177
(22.97), 155 (5.74), 141 (7.97), 127 (14.46), 113 (17.56), 99 (20.31),
85 (48.15), 71 (73.07), 57 (94.75), 43 (100.00). HRMS (EI) Calcd.
For C16H20O6 (M+): 308.1260; found 308.1255.
Acknowledgments
We thank the Shanghai Municipal Committee of Science and Tech-
nology (08dj1400100-2), National Basic Research Program of
China (973-2009CB825300), and the National Natural Science
Foundation of China for financial support (20872162, 20672127,
20821002 and 20732008).
Compound 2o: Yield 68 mg, 99%. A colorless oil. IR (CH Cl ): ν
˜
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= 2940, 1743, 1592, 1506, 1461, 1422, 1372, 1227, 1128, 1027, 926,
513 cm–1. 1H NMR (CDCl3, 300 MHz, TMS): δ = 2.04 (s, 3 H,
CH3), 2.14 (s, 3 H, CH3), 3.84 (s, 3 H, OCH3), 3.86 (s, 6 H, OCH3),
4.45 (d, J = 13.5 Hz, 1 H, CH), 4.60 (d, J = 13.5 Hz, 1 H, CH),
5.34 (s, 2 H, CH2), 6.25 (s, 1 H, CH), 6.57 (s, 2 H, Ar) ppm. 13C
NMR (CDCl3, 75 MHz, TMS): δ = 20.7, 21.1, 56.0, 60.7, 64.0,
75.3, 104.4, 115.2, 133.0, 137.9, 141.8, 153.2, 169.6, 170.5 ppm. MS
(EI): m/z (%) = 338 (0.46) [M+], 219 (2.80), 205 (7.06), 188 (1.98),
115 (2.41), 91 (3.02), 77 (3.94), 57 (4.61), 43 (100.00). HRMS (EI)
Calcd. For C17H22O7 (M+): 338.1366; found 338.1367.
Compound 3a: Yield 51 mg, 91%. A light yellow oil. IR (CH2Cl2):
ν = 3005, 2957, 2837, 1666, 1602, 1513, 1306, 1257, 1166, 1031,
˜
1
989, 838, 760 cm–1. H NMR (CDCl3, 400 MHz, TMS): δ = 1.25
(dd, J = 4.0, J = 6.8 Hz, 2 H, CH2), 1.57 (dd, J = 4.0, J = 6.8 Hz,
5458
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© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2010, 5454–5459

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Received: May 28, 2010
Published Online: August 16, 2010
Eur. J. Org. Chem. 2010, 5454–5459
© 2010 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
5459