Stereoselectivity in trimethylenemethane (TMM) diyl mediated cycloaddition reaction to angularly fused triquinanes

Article abstract of DOI:10.1002/asia.201000672

A thorough study on the diastereoselectivity in the TMM diyl mediated [2+3] cycloaddition reaction of monosubstituted linear substrates to form angularly fused triquinanes was carried out. Substitution at position 3 provided complete diastereoselectivity,

Full text of DOI:10.1002/asia.201000672

FULL PAPERS
DOI: 10.1002/asia.201000672
Stereoselectivity in Trimethylenemethane (TMM) Diyl Mediated
Cycloaddition Reaction to Angularly Fused Triquinanes
Yeokwon Yoon, Taek Kang, and Hee-Yoon Lee*[a]
Dedicated to Professor Eiichi Nakamura on the occasion of his 60th birthday
Abstract: A thorough study on the diastereoselectivity in the TMM diyl mediated
[2+3] cycloaddition reaction of monosubstituted linear substrates to form angular-
ly fused triquinanes was carried out. Substitution at position 3 provided complete
diastereoselectivity, while positions 1 and 4 induced marginal stereoselectivity. Po-
sition 2 did not show any influence on the diastereoselectivity. Position 4 turned
out to be incompatible with the cycloaddition reaction as the carbene intermediate
Keywords: carbenes
tion · stereoselectivity · trimethyl-
enemethane · triquinane
·
cycloaddi-
À
underwent O Si bond insertion to form a dihydrofuran ring.
Introduction
Trimethylenemethane (TMM) had been a theoretically in-
teresting species before its first observation by Dowd in
1966.[1] Since then, TMM has attracted the interest of physi-
cal organic and synthetic chemists owing to its unique elec-
tronic state and seemingly high reactivity.[2] The first syn-
thetically useful TMM was discovered by Kçbrich[3] as the
TMM diyl diradical, and thorough study of this TMM diyl
by Berson has revealed various properties of TMM diyl in-
cluding [2+3] cycloaddition reaction with multiple bonds.[4]
Little and Ott later further developed this TMM diyl [2+3]
cycloaddition reaction and applied it to the total synthesis of
linearly fused triquinane natural products (Figure 1a).[5] The
TMM diyl was also utilized in the diradical cyclization reac-
tions to form medium-size rings.[6] In this case, two radicals
of TMM diyl reacted separately to form diradical intermedi-
ates that undergo immediate recombinative bond formation.
Figure 1. Various ways of TMM-mediated [2+3] cycloaddition reactions.
Though TMM diyl is highly reactive and reacts with any
type of multiple bonds to form five-membered rings, it has
shown limited synthetic applicability owing to restrictions in
the preparation of precursor compounds. As supplements to
the TMM diyl diradical, several synthetic methodologies
have been developed. Methylene cyclopropane was used in
the Pd- or Ni-mediated cycloaddition reaction though the
reaction did not generate TMM intermediates or TMM
metal complexes.[7] Methylenecyclopropane could be re-
placed with acetate of silylated methallyl alcohol in a Pd-
mediated cycloaddition reaction.[8] A more stable form of
TMM as a zwitterion was also developed by Yamago and
Nakamura and was applied to [2+3] cycloaddition reaction
(Figure 1).[9]
[a] Dr. Y. Yoon, T. Kang, Prof. Dr. H.-Y. Lee
Department of Chemistry
KAIST
373-1 Gusung Dong, Yuseong, Daejeon, 305-701 (Korea)
Fax : (+82)42-350-2810
E-mail: leehy@kaist.ac.kr
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/asia.201000672.
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Chem. Asian J. 2011, 6, 646 – 651

Recently, we reported an alkylidene carbene initiated cy-
cloaddition reaction of TMM diyl.[10a] This new strategy not
only offers a unique synthetic strategy as the alkylidene car-
bene reacts with olefin to turn the double bond into a TMM
diradical while cleaving the double bond completely, but
also adds versatility to the existing synthetic methodology
by Little and Ott, as the new methodology extends the
TMM diyl mediated cycloaddition reaction to the synthesis
of angularly fused triquinanes (Figure 2).[11] The alkylidene
Scheme 1. Asymmetric induction in the TMM diyl [2+3] cycloaddition
reaction.
Figure 2. Alkylidene carbene mediated TMM diyl cycloaddition reac-
tions.
carbene mediated TMM diyl cycloaddition reaction becomes
versatile as several different ways to generate alkylidene
carbene can be applied to produce TMM diyls[10] and thus
allows a stereoselectivity study during [2+3] cycloaddition
reaction in the formation of triquinane compounds. While
transition-metal-mediated enantioselective [2+3] cycloaddi-
tion through a TMM-like intermediate has been successfully
explored,[12] diastereoselectivity in the formation of triqui-
nanes through [2+3] cycloaddition reaction has not been
systematically studied.[13] For angularly fused triquinanes, no
such study had been possible before the alkylidene carbene
route was developed. Understanding of stereoselectivity in
the cycloaddition reaction to angularly fused triquinanes
would provide valuable information for designing and plan-
ning the total synthesis of natural products possessing the
triquinane structure.[14]
Scheme 2. Reagents and conditions: a) TBSCl, NaH/THF, 86%; b) MsCl,
Et3N/CH2Cl2; c) TMS-propargyl Grignard, CuCN/Et2O, 68% for two
steps; d) 1N HCl/THF, 99%; e) MsCl, Et3N/CH2Cl2; f) diethyl malonate,
NaH/THF, 86% for two steps; g) NaCl, H2O/DMSO, reflux, 66%;
h) LiAlH4/Et2O, 0 8C, 99%; i) (COCl)2-DMSO; Et3N/CH2Cl2, À608C–RT,
96%; j) vinyl Grignard/THF, 08C, 76%; k) TBSOTf, 2,6-lutidine/CH2Cl2,
92%; l) K2CO3/MeOH, 97%.
late, followed by copper-catalyzed propargylation, produced
7 after deprotection of the silyl group. The alcohol was acti-
vated as mesylate, and malonate ester synthesis protocol
produced 8. The ester of 8 was converted into the corre-
sponding aldehyde and then vinyl Grignard addition to the
aldehyde produced 9. Protection of the alcohol of 9 fol-
lowed by the liberation of terminal alkyne produced 1a.
Substrate 1b was prepared from pentynol (Scheme 3).
From pentynol, 11 was prepared by following a literature
preparation.[16] The ester group of 11 was reduced using
DIBAL-H to form the diol product and both hydroxy
groups of the product were protected as silyl ethers to pro-
duce 12. Selective deprotection of the primary alcohol of
12[17] and subsequent oxidation followed by allyl Grignard
addition produced 13. The free hydroxy group was protected
temporarily as an acetate, and deprotection of the silyl
group followed by oxidation produced ketone 14. Olefina-
tion of the ketone of 14 under neutral reaction conditions[18]
and protecting group exchange yielded 1b.
Results and Discussion
There are five positions in the dieneyne precursor A that
can induce stereoselectivity during the tandem cycloaddition
reaction to form angularly fused triquinanes. A silylated hy-
droxy group was introduced into each of these five positions
to examine the stereoselectivity during the [2+3] cycloaddi-
tion reaction (Scheme 1).
Preparation of the Substrates for Tandem Cycloaddition
Reaction
The synthesis of 1a started from 6 (Scheme 2). Selective mo-
noprotection of a hydroxy group with a tert-butyldimethylsil-
yl group[15] and activation of the remaining alcohol as mesy-
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H.-Y. Lee et al.
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Scheme 6. Reagents and conditions: a) nBuLi, 5-bromopent-1-ene/THF
95%; b) nBuLi, BrCH2CH2OTBS/THF, 68%; c) TBAF/THF, 90%;
d) TFAA-DMSO; Et3N/CH2Cl2, À608C–RT, 67%; e) HCCMgBr/Et2O,
Scheme 3. Reagents and conditions: a) LiAlH4/Et2O, 85%; b) TBSOTf,
2,6-lutidine/CH2Cl2, 96%; c) HF-pyr/THF, 85%; d) (COCl)2-DMSO;
Et3N/CH2Cl2, À608C–RT, 96%; e) allyl Grignard/Et2O, 0 8C, 74% for
two steps; f) Ac2O, Et3N, DMAP/CH2Cl2, 95%; g) 1N HCl/THF, 71%;
h) PCC/CH2Cl2, 92%; i) CH2I2, Zn, TiCl4/THF, 42%; j) K2CO3/MEOH,
92% k) TBSOTf, 2,6-lutidine/CH2Cl2, 86%.
08C, 66%; f) TBSOTf, 2,6-lutidine/CH2Cl2, 95%; g) PhIACHTNUGRTNEUNG(TFA)2/CH3CN-
H2O, 70%; h) CH2I2, Zn, TiCl4/THF, 33%.
twice with 5-bromopent-1-ene and silyl-protected bromo-
ethanol to afford 19 after deprotection of the silyl protecting
group. The alcohol of 19 was oxidized to the corresponding
aldehyde, and acetylide anion addition to the aldehyde pro-
duced 20 after protection of the resulting alcohol. The thio-
acetal of 20 was liberated to the ketone,[20] and olefination
of the ketone furnished 1e.
Scheme 4. Reagents and conditions: a) TPAP, NMO/CH2Cl2; b) 3-butenyl
Grignard/Et2O, 84% for two steps; c) TBAF/THF, 91%; d) TBSOTf, 2,6-
lutidine/CH2Cl2, 98%.
Stereoselectivity in the Tandem Cycloaddition Reaction of
Linear Substrates with OTBS Substituents in the Formation
of Angularly Fused Triquinanes
Substrate 1c was prepared from 7 (Scheme 4). Oxidation
of the alcohol to the corresponding aldehyde followed by
the addition of 3-butenyl Grignard reagent produced 15.
Silyl protection after desilylation of the alkyne produced 1c.
Substrate 1d also was preprared from hydroxymethallyl
alcohol 6 (Scheme 5). Selective protection of one of the two
The prepared substrates 1a–e were converted into alkynyl
iodonium salts, and alkylidene carbenes were generated
from the alkynyl iodonium salts by the addition of phenyl-
sulfinate anion to the b-position of the alkynes. The alkyli-
dene carbenes underwent tandem cycloaddtion reaction to
form angularly fused triquinanes (Scheme 7) and the results
are summarized in the Table 1.
Scheme 5. Reagents and conditions: a) DHP, PPTS/CH2Cl2, 50%;
b) MsCl, Et3N/CH2Cl2; c) 3-butenyl Grignard, CuCN/Et2O, 87% for two
steps; d) TsOH/MeOH, 95%; e) TPAP, NMO/CH2Cl2; f) TMS-propargyl
Grignard/Et2O, 69% for two steps; g) TBAF/THF, 90%; h) TBSOTf, 2,6-
lutidine/CH2Cl2, 93%.
alcohols as the THP ether and butenylation after activation
of the remaining alcohol as mesylate afforded 16. The alco-
hol that was obtained from deprotection of the THP group
of 16 was oxidized to the aldehyde, and propargyl Grignard
addition to the aldehyde produced 17. Silyl protection of the
alcohol after the desilylation of alkyne produced 1d.
The synthesis of 1e started from 1,3-dithiane anion alkyla-
Scheme 7. Preparation of iodonium salts and tandem cycloaddition reac-
tion.
tion reactions (Scheme 6).[19] 1,3-Dithiane was alkylated
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Stereoselectivity in Trimethylenemethane Diyl Mediated Cycloaddition
Table 1. Products from tandem cycloaddition reaction of alkylidene car-
benes.
Precursor
Products and yield[a]
1a
22% (2:1)
26%
1b
1c
Scheme 8. Cyclopropanation versus insertion reaction.
26% (1:1)
28%
33%
stead of undergoing cyclopropanation reaction. The inser-
À
tion reaction into the O Si bond appears to be as facile as
À
the insertion reaction into the C H bond. This result indi-
cates that position 4 cannot accommodate substituents
where carbene insertion could occur.
21%
74%
36%
The stereochemistry of the products was confirmed by
NOE experiments (Scheme 9). Since 2a and 2a’ were not
1d
1e
15%
13%
[a] Yield of isolated product. The product ratios in the parenthesis were
1
determined by H NMR integration of the crude product mixtures.
Synthesis of angularly fused triquinanes from linear sub-
strates 1a–e was initiated by the introduction of an iodo-
phenyl group to the end of the terminal alkynes via SnBu3
substitution. When the phenylsulfinate anion was added to
the alkynyl iodonium salts, the alkylidene carbenes were
generated, and subsequent cyclopropanation followed by
TMM formation set the stage for a possible stereoselective
[2+3] cycloaddition reaction. Though the triquinane forma-
tion through alkylidene cabene formation was accompanied
by rearrangement of the alkylidene carbene to phenyl sul-
fone, this side reaction would not affect the stereoselectivity
during the cycloaddition reaction. The cycloaddition reac-
tion of 1a produced a mixture of two diastereomeric prod-
ucts in 2:1 ratio. When the substitution was moved to posi-
tion 2, no stereoselecitivity was observed, as the cycloaddi-
tion reaction of 1b produced an equal amount of two diaste-
reomeric products. To our delight, when the substituent was
moved to position 3, only a single isomeric triquinane prod-
uct was obtained. In the case of the substrate 1e, the cyclo-
addition reaction produced a mixture of two diastereomeric
products in 2:1 ratio. Contrary to other substrates, 1d pro-
duced a completely different type of product through car-
Scheme 9. Confirmation of stereochemistry of the products by NOE ex-
periments.
separable, the corresponding diastereomeric alcohols 5a and
5a’ were prepared through deprotection of the silyl groups
and then separated. The NOE experiment on 5a showed
that the carbinol proton has interactions with protons H5,
H7a, and H8a, which confirmed the relative stereochemistry
of 5a. In the case of 2c, interaction of the carbinol proton
with H4b clearly confirmed the relative stereochemistry. In-
teraction of the carbinol proton of 2e with H4a also con-
firmed the relative stereochemistry of 2e. This result
showed that only position 3 can induce a good diastereose-
lectivity during the [2+3] cycloaddition reaction while posi-
tions 1 and 5 have little influence in the diastereoselectivity.
Position 2 did not appear to influence the stereochemical
outcome of the cycloaddition reaction.
The diastereoselectivity of the cycloaddition reaction can
be explained through the transition-state model
(Scheme 10). The transition-state model clearly distinguishes
the pseudo-equatorially positioned OTBS group from the
bene insertion reaction (Scheme 8). Alkylidene carbene was
[21]
À
inserted into the O Si bond to form a dihydrofuran in-
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H.-Y. Lee et al.
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The filtrate was concentrated in vacuo to yield the tin compound, which
was used for the next step. To a stirred solution of tin compound in
CH2Cl2 (100 mLmmolÀ1) was added a solution of phenyl
ACTHNUTRGNE(NUG cyano)iodonium
triflate (1.2 equiv) at À408C under argon. The reaction mixture was
stirred for 15 min and formed a clear solution at À408C. Then, the reac-
tion mixture was added to a solution of benzenesulfinic acid sodium salt
(2 equiv) and [18]crown-6 (2 equiv) in CH2Cl2 (200 mLmmolÀ1) at room
temperature. The resulting reaction mixture was stirred and was
quenched with saturated NH4Cl solution and extracted with CH2Cl2. The
organic layers were combined and dried over MgSO4. The filtrate was
concentrated in vacuo, and the residue was purified by flash column
chromatography on silica gel to give the products.
Compound 3a: 1H NMR (400 MHz, CDCl3): d=7.97 (2H, d, J=7.2 Hz),
7.66–7.62 (1H, m), 7.56–7.53 (2H, m), 5.79–5.70 (1H, m), 5.12 (1H, dt,
J=17.2 Hz, J=1.5 Hz), 5.02 (1H, dd, J=11.6 Hz, J=1.2 Hz), 4.73 (1H,
s), 4.66 (1H, s), 4.07 (1H, q, J=6.0 Hz), 2.47 (2H, t, J=7.4 Hz), 2.23
(2H, t, J=7.5 Hz), 2.02–1.89 (2H, m), 1.58–1.50 (2H, m), 0.87 (9H, s),
0.01 (3H, s), 0.00 ppm (3H, s); 13C NMR (100 MHz, CDCl3): d=146.3,
142.0, 141.3, 133.9, 129.2, 127.2, 114.0, 110.6, 97.0, 78.5, 73.3, 36.0, 33.3,
31.0, 25.8, 28.2, 17.7, À4.3, À4.8 ppm.
Scheme 10. Transition-state model of the [2+3] cycloaddition reaction.
pseudo-axially positioned one at position 3. The pseudo-ax-
ially oriented OTBS group shows a 1,3-diaxial interaction
with the methyl group of the five-membered ring. This steric
bias led to the complete stereoselectivity of the cycloaddi-
tion reaction of 1c. On the other hand, substitution at posi-
tion 2 would be far from the other part of the molecule and
thus shows no influence on the diastereoselectivity. The cur-
rent model also explains why there is only a small bias for
the two diastereomeric products in the transition state
during the cycloaddition reactions of 1a and 1e. The sub-
stituent at position 1 or 5 does not appear to provide sub-
stantial steric bias in the transition state to distinguish the
two products.
1
Compound 5a: H NMR (400 MHz, CDCl3): d=7.86–7.84 (2H, m), 7.58–
7.57 (1H, m), 7.53–7.49 (2H, m), 4.36–4.31 (1H, m), 3.05–2.99 (1H, m),
2.85–2.79 (1H, m), 2.56 (1H, dd, J=14.8 Hz, J=8.0 Hz), 2.32–2.25 (2H,
m), 2.14–2.09 (1H, m), 1.87–1.77 (3H, m), 1.68–1.61 (3H, m), 1.35–1.29
(1H, m), 1.25–1.22 ppm (1H, m)
Compound 5a’: 1H NMR (400 MHz, CDCl3): d=7.86–7.84 (2H, m),
7.61–7.49 (3H, m), 4.07–4.05 (1H, m), 3.01 (1H, dd, J=15.7 Hz, J=
7.0 Hz), 2.90–2.81 (1H, m), 2.58–2.52 (1H, m), 2.29–2.21 (1H, m), 2.17–
2.08 (2H, m), 2.02–1.94 (4H, m), 1.89–1.84 (1H, m), 1.78–1.70 ppm (3H,
m).
Compound 2b+2b’: 1H NMR (400 MHz, CDCl3): d=7.85 (4H, d, J=
7.3 Hz), 7.59–7.56 (2H, m), 7.52–7.48 (4H, m), 7.52–7.48 (4H, m), 4.34–
4.31 (1H, m), 4.07–4.03 (1H, m), 3.04–2.94 (2H, m), 2.82–2.73 (2H, m),
2.57–2.46 (3H, m), 2.28–2.18 (2H, m), 2.14 (2H, dd, J=12.1 Hz, J=
5.7 Hz), 2.02–1.92 (3H, m), 1.91–1.86 (2H, m), 1.83–1.75 (3H, m), 1.73–
1.64 (3H, m), 1.49–1.44 (2H, m), 1.37–1.33 (2H, m), 0.84 (9H, s), 0.82
(9H, s), 0.01 (3H, s), 0.01 (3H, s), 0.00 (3H, s), À0.01 ppm (3H, s).
Conclusions
In summary, substituent effects on the diastereoselectivity
during TMM diyl [2+3] cycloaddition reaction were investi-
gated. Among five positions for a substituent effect, only
position 3 provides a good diastereoselectivity. Position 4
turned out to be incompatible with the alkylidene carbene
mediated TMM diyl [2+3] cycloaddition reaction. Substitu-
ents at the other positions showed little or no stereoselectiv-
ity during the cycloaddition reaction.
This result provides a good guideline for the alkylidene-
mediated TMM diyl [2+3] cycloaddtion reaction in applica-
tion to the stereoselective total synthesis of many angularly
fused triquinane natural products as most of angularly fused
triquinanes in nature have substituents at position 3.[22] Ap-
plication of this diastereoseletive cycloaddition reaction to
the total synthesis of angularly fused triquinane natural
products will be communicated in due course.
1
Compound 3b: H NMR (400 MHz, CDCl3): d=7.98–7.96 (2H, m), 7.66–
7.63 (1H, m), 7.57–7.53 (2H, m), 5.81–5.70 (1H, m), 5.03–4.97 (2H, m),
4.78 (1H, s), 4.75 (1H, d, J=1.1 Hz), 3.78–3.72 (1H, m), 2.48 (2H, t, J=
7.2 Hz), 2.26 (2H, t, J=7.4 Hz), 2.21–2.03 (4H, m), 0.83 (9H, s), 0.01
(3H, s), À0.03 ppm (3H, s); 13C NMR (100 MHz, CDCl3): d=143.5,
142.1, 134.9, 133.9, 129.2, 127.2, 117.2, 113.7, 97.0, 78.6, 71.0, 43.1, 41.5,
33.7, 25.8, 18.0, 17.7, À4.5, À4.5 ppm.
1
Compound 2c: H NMR (400 MHz, CDCl3): d=7.86–7.84 (2H, m), 7.56–
7.54 (1H, m), 7.50–7.46 (2H, m), 3.80 (1H, dd, J=9.8 Hz, J=5.8 Hz),
3.05 (1H, dd, J=18.6 Hz, J=7.2 Hz), 2.81–2.77 (1H, m), 2.54 (1H, dd,
J=14.4 Hz, J=9.2 Hz), 2.47 (1H, dd, J=12.1 Hz, J=6.6 Hz), 2.34–2.29
(1H, m), 2.09–2.03 (2H, m), 1.96–1.92 (1H, m), 1.82–1.76 (1H, m), 1.69–
1.63 (1H, m), 1.57–1.47 (3H, m), 1.16–1.14 (1H, m), 0.74 (9H, s), À0.09
(3H, s), À0.24 ppm (3H, s); 13C NMR (100 MHz, CDCl3): d=168.2,
141.2, 132.9, 131.0, 129.0, 127.5, 79.1, 71.8, 45.5, 36.4, 36.0, 34.8, 32.7, 28.8,
25.7, 24.3, 17.8, À4.8, À5.3 ppm.
1
Compound 3c: H NMR (400 MHz, CDCl3): d=7.98–7.96 (2H, m), 7.66–
7.62 (1H, m), 7.56–7.53 (2H, m), 5.80–5.70 (1H, m), 4.99–4.91 (3H, m),
4.73 (1H, s), 4.03 (1H, t, J=6.4 Hz), 2.54 (2H, t, J=7.5 Hz), 2.35–2.28
(1H, m), 2.23–2.15 (1H, m), 2.02–1.87 (2H, m), 1.59–1.42 (2H, m), 0.84
(9H, s), 0.00 (3H, s), À0.07 ppm (3H, s); 13C NMR (100 MHz, CDCl3):
d=148.4, 142.0, 138.3, 133.9, 129.2, 127.3, 114.7, 111.5, 97.2, 78.5, 75.9,
35.7, 29.7, 27.8, 25.8, 18.1, 18.0, À4.6, À5.0 ppm.
Experimental Section
Compound 4: 1H NMR (400 MHz, CDCl3): d=7.86–7.84 (2H, m), 7.57–
7.49 (3H, m), 5.74–5.69 (1H, m), 5.06–4.91 (4H, m), 4.84 (1H, s), 2.90
(1H, dd, J=14.4 Hz, J=11 Hz), 2.57 (1H, dd, J=14.4 Hz, J=9.8 Hz),
2.02–1.87 (4H, m), 1.51–1.47 (2H, m), 0.99 (9H, s), 0.38 (3H, s),
0.35 ppm (3H, s); 13C NMR (100 MHz, CDCl3): d=173.8, 147.0, 141.5,
138.2, 132.7, 129.0, 127.2, 124.5, 114.9, 110.9, 86.9, 36.1, 33.4, 30.4, 26.9,
26.6, 17.5, À4.9, À5.0 ppm.
General experimental procedure for cycloaddition reaction: To a stirred
solution of alkyne 1a–e (1 equiv) in THF (20 mLmmolÀ1) was added
nBuLi (1.2 equiv) at À788C. After the reaction mixture was stirred for
1 h, tributyltin chloride (1.1 equiv) was added. The reaction mixture was
allowed to warm to room temperature and stirred overnight. The result-
ing mixture was quenched with saturated NH4Cl solution and extracted
with EtOAc. The organic layers were combined and dried over MgSO4.
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Stereoselectivity in Trimethylenemethane Diyl Mediated Cycloaddition
1
Compound 2e: H NMR (400 MHz, CDCl3): d=7.87–7.85 (2H, m), 7.54–
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b) H. Y. Lee, W.-Y. Kim, S. Lee, Tetrahedron Lett. 2007, 48, 1407–
1410; c) H. Y. Lee, Y. Yoon, Y.-H. Lim, Y. Lee, Tetrahedron Lett.
2008, 49, 5693–5696.
7.50 (1H, m), 7.47–7.44 (2H, m), 5.15 (1H, d, J=5.6 Hz), 3.05–2.98 (1H,
m), 2.37–2.28 (1H, m), 2.16–2.04 (2H, m), 1.97–1.85 (3H, m), 1.80–1.65
(4H, m), 1.64–1.56 (1H, m), 1.45–1.37 (1H, m), 0.74 (9H, s), 0.01 (3H,
s), À0.03 ppm (3H, s); 13C NMR (100 MHz, CDCl3): d=177.7, 142.9,
132.5, 131.3, 128.8, 126.8, 80.6, 67.7, 48.9, 46.9, 41.1, 34.9, 34.8, 27.1, 25.7,
24.9, 17.7, À4.8, À5.0 ppm.
Compound 2e’: 1H NMR (400 MHz, CDCl3): d=7.87–7.84 (2H, m),
7.51–7.43 (3H, m), 5.43–5.39 (1H, m), 2.86 (1H, ddd, J=16.8 Hz, J=
7.8 Hz, J=2.1 Hz), 2.46–2.36 (1H, m), 2.29 (1H, dd, J=11.6 Hz, J=
5.6 Hz), 2.18–2.11 (1H, m), 2.01–1.91 (2H, m), 1.74–1.59 (4H, m), 1.50–
1.46 (1H, m), 1.42–1.34 (2H, m), 0.72 (9H, s), 0.01 (3H, s), À0.01 ppm
(3H, s); 13C NMR (100 MHz, CDCl3): d=173.1, 143.1, 132.3, 131.6, 128.6,
126.8, 79.9, 63.7, 52.2, 47.2, 39.2, 34.9, 33.2, 27.3, 25.9, 25.8, 18.0, À4.7,
À4.9 ppm.
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2672–2675.
1
Compound 3e: H NMR (400 MHz, CDCl3): d=7.98–7.96 (2H, m), 7.68–
[12] a) P. LeMarquand, W. Tam, Angew. Chem. 2008, 120, 2968–2970;
Angew. Chem. Int. Ed. 2008, 47, 2926–2928; b) B. M. Trost, S. M.
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7.64 (1H, m), 7.57–7.54 (2H, m), 5.79–5.71 (1H, m), 5.00–4.92 (2H, m),
4.79 (1H, d, J=1.2 Hz), 4.74 (1H, s), 4.52 (1H, t, J=6.8 Hz), 2.36 (2H,
d, J=6.8 Hz), 2.02–1.94 (4H, m), 1.49–1.41 (2H, m), 0.79 (9H, s), 0.00
(3H, s), À0.02 ppm (3H, s); 13C NMR (100 MHz, CDCl3): d=143.5,
141.6, 138.5, 134.1, 129.3, 127.5, 114.7, 113.7, 95.7, 81.3, 62.2, 43.7, 35.5,
33.2, 26.8, 25.5, 18.0, À4.9, À5.2 ppm.
[16] H. Fujiwara, T. Aoyama, T. Shioiri, Tetrahedron 1998, 54, 551–564.
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2162.
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Acknowledgements
This research was supported by Basic Science Research Program through
the National Research Foundation of Korea (NRF) funded by the Minis-
try of Education, Science and Technology (KRF-2008-314-C00198).
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Received: September 15, 2010
Published online: November 12, 2010
Chem. Asian J. 2011, 6, 646 – 651
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