Asymmetric desymmetrization of the diallyl acetals of alkynals by the enantioselective Pauson-Khand-type reaction catalysts

Article abstract of DOI:10.1002/adsc.200800514

Asymmetric desymmetrization of the di-allyl acetals of alkynal (1) by an enantioselective Pauson-Khand-type reaction catalyst was studied. The corresponding 5-oxabicyclo[3.3.0]octenones (2) were obtained as a mixture of diastereomers (2a and 2b), which were hydrolyzed to afford a single enantiomer (3), in high yields (up to 88%) as well as excellent enantioselectivities (up to 97%).

Full text of DOI:10.1002/adsc.200800514

COMMUNICATIONS
DOI: 10.1002/adsc.200800514
Asymmetric Desymmetrization of the Diallyl Acetals of Alkynals
by the Enantioselective Pauson–Khand-Type Reaction Catalysts
Dong Eun Kim,a Bo Hyung Lee,a Mudigonda Rajagopalasarma,a
Jean-Pierre GenÞt,b Virginie Ratovelomanana-Vidal,b,* and Nakcheol Jeonga,*
a
Department of Chemistry, Korea University, Seoul, 136-701, Korea
Fax : (+82)-2-3290-3121; phone: (+82)-2-3290-3136; e-mail: njeong@korea.ac.kr
Laboratoire de Synthꢀse Sꢁlective Organique et Produits Naturels, Ecole Nationale Supꢁrieure de Chimie de Paris, 11 rue
b
Pierre et Marie Curie, 75231 Paris Cedex 05, France
E-mail: virginie-vidal@enscp.fr
Received: August 14, 2008; Published online: November 17, 2008
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/adsc.200800514.
Abstract: Asymmetric desymmetrization of the di-
allyl acetals of alkynal (1) by an enantioselective
Pauson–Khand-type reaction catalyst was studied.
The corresponding 5-oxabicyclo[3.3.0]octenones (2)
were obtained as a mixture of diastereomers (2a
and 2b), which were hydrolyzed to afford a single
enantiomer (3), in high yields (up to 88%) as well
as excellent enantioselectivities (up to 97%).
Compound (1) had been previously subjected to
PKR utilizing a stoichiometric amount of Co2(CO)8
and gave a diastereomeric and racemic mixture of 2-a
and 2-b.[4a] The resulting products (2) were useful for
the preparation of iridoids and carbocyclic nucleotide
mimics.[4b,c] Having established an achiral Co2(CO)8
catalyst for the formation of racemic 2, we next fo-
cused on the stereoselective version of the reaction by
using APKR catalysts. The resultant products can
serve as key intermediates in the synthesis of relevant
natual products such as brefeldin A (6). We first
checked the compatibility of the acetal substrates (1)
with the currently available APKR catalysts. Several
conditions previously reported based on either Rh(I)
or Ir(I) to date together with the newly optimized
conditions at ambient temperature by us[5] were
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
Keywords: asymmetrric desymmetrization; atrop-
ACHTUNGTRENNUNG
The asymmetric desymmetrization of meso com- tested to examine the characteristics of the reaction
pounds or prochiral compounds by chiral catalysts is and find an optimized condition. The results are sum-
among the most efficient strategies to generate opti- marized in Table 1.
cally pure compounds.[1] We reported previously an
efficient catalytic asymmetric Pauson–Khand reaction
based on chiral cationic Rh(I)-BINAP complexes
(named APKR hereafter).[2] In an effort for determin-
ing the scope of this reaction and exploring its appli-
cation to the synthesis of natural or unnatural biologi-
cally interesting compounds, we reported the efficient
asymmetric desymmetrization of the prochiral dien-
ynes such as propargyl 1-vinylallyl N-tosylamides and
ethers.[3] We describe herein the synthesis of a wide
range of highly functionalized cyclopentenones (3) in
optically pure or enriched form based on the same
concept. As seen in the previous study with dien-
ynes,[3] asymmetric desymmetrization of acetals (1) by
the chiral PKR catalyst also generates two stereogenic
centers at the same time, raising issues of diastereose-
lectivity as well as enantioselectivity (Scheme 1).
Scheme 1. Asymmetric desymmetrization of bisallyl prop-
argyl acetals
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Table 1. Optimization of desymmetrization of 1-3 by various
asymmetric Pauson-Khand reaction catalysts.
pounds 2-3a (36% yield, 68% ee) and 2-3b (5% yield,
46% ee) with moderate yields and enantioselectivi-
ties[5] On the other hand, a relatively insensitive neu-
tral Ir(I) catalyst, generated from [IrACHTUNRGTNEUNG(COD)2Cl]2 (15
mol%) and (R)-BINAP (30 mol%) in toluene, which
was our choice in the previous desymmetrization of
dieneynes,[3,6a] was reluctant to react with substrate 1-
3 even at high temperature (1108C) and for a pro-
longed reaction time (24 h) (entry 3 in Table 1). Final-
ly, by combining [Rh(CO)2Cl]2 (5 mol%) and (R)-
BINAP (12 mol%) and cinnamaldehyde developed
by Shibata and co-workers, which served not only as
solvent but also as a source of carbon monoxide by
rhodium(I)-catalyzed decarbonylation, the reaction
proceeded at 1208C to afford compounds 2-3a (41%
yield, 86% ee) and 2-3b (25% yield, 70% ee).[6d]
The following characteristics of the reaction are
worth mentioning: (1) Carefully dry conditions were
required to obtain a good combined yield of 66%. (2)
The reaction provided the PKR product 2-3 as a mix-
ture of diastereomers, 2-3a and 2-3b, in 25% and
41%, respectively.[7] The ratio of diastereomers was
variable depending on the exact conditions, but opti-
Entry
Conditions[a]
2-3a
Yield/ee [%]
2-3b
Yield/ee [%]
1
2
3
4
a
b
c
NR (decomposition of 1-3)
36/68 5/46
Only 20% of 1-3 was consumed.
41/86 25/70
d
[a]
a [Rh(CO)2Cl]2 (3 mol%), (R)-BINAP (9 mol%), AgOTf
(12 mol%) in THF at 908C under CO (1 atm). b
[Rh(CO)2Cl]2 (3 mol%), (R)-BINAP (9 mol%), AgOTf
(12 mol%) in THF at 18-208C under Ar:CO (10:1, 1
atm).
mol%) in toluene at 1108C under CO (1 atm). d. [Rh-
(COD)Cl]2 (5 mol%), (R)-BINAP (12 mol%) in cinna-
maldehyde (20 eq) at 1208C under Ar (1 atm).
c [IrACHTUNGTRENNUNG(COD)2Cl]2 (15 mol%), (R)-BINAP (30
ACHTUNGTRENNUNG
Compound 1-3, a reference substrate, was too sensi- mization for the exclusive formation of one diastereo-
tive to the original cationic Rh(I) catalyst protocol mer seemed improbable. The enantiomeric excesses
pioneered by our laboratory.[2c] Consequently, the ap- of diasteromers were determined as 70% for minor
plication of the original thermal reaction gave rise to product 2-3a and 86% for major product 2-3b. The as-
substantial amounts of decomposed compounds signment of relative stereochemistry was later unam-
(entry 1 in Table 1). At ambient temperature (entry 2 biguously confirmed by the elucidation of the single
in Table 1), the cationic Rh(I) catalyst prepared by crystal structure of 2-5a obtained from entry 10 in
mixing [Rh(CO)2Cl]2 (3 mol%), (R)-BINAP (9 Table 3 (Figure 1). (3) The absolute configuration at
mol%) and AgOTf (12 mol%) did provide com- C*(1) of both diastereomers 2-3a and 2-3b was deter-
Table 2. Ligand effects on the desymmetrization of 1-3.
Entry
Ligand
2-3a
2-3b
Yield/ee [%] config. C*(1)
Yield/ee [%] config. C*(1)
1
2
3
4
5
6
7
(R)-L1 p-OMe-BINAP
(R)-L2 p-Me-BINAP
(R)-L3 BINAP
(R)-L4 p-CF3-BINAP
(S)-L5 Synphos
(S)-L6 Difluorphos
(R)-L7 Segphos
21/67 (R)
36/65 (R)
25/70 (R)
36/32 (R)
30/67 (S)
28/63 (S)
27/74 (R)
49/81 (R)
46/87 (R)
41/83 (R)
37/44 (R)
55/90 (S)
22/70 (S)
48/83 (R)
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Asymmetric Desymmetrization of the Diallyl Acetals of Alkynals
COMMUNICATIONS
The experimental protocol was established as fol-
lows: a mixture of substrate 1 and the neutral Rh(I)-
(R)-p-Me-BINAP (L2) or (S)-Synphos (L5) catalyst
(prepared in situ by mixing 3 mol% [RhClACTHNUGTRENUNG(COD)]2
and 9 mol% of the corresponding ligand) in cinnamal-
dehyde was refluxed under argon until the starting
material disappeared completely, usually within 2 h.
After extensive experimentations, we learned that
(R)-p-Me-BINAP (L2) and (S)-Synphos (L5) have a
different behavior depending on the considered sub-
strates 1. For example, (S)-Synphos (L5) was the
better ligand for the relatively slow reacting sub-
strates (1-1 to 1-5), bearing aryl substituents on the
alkyne. The phosphorus on (S)-Synphos (L5) had
comparable electron density with that of BINAP (L3)
(respectively, 31P NMR: À14.3 ppm and À14.4 ppm).
As a result, the decarbonylation was affected effi-
Figure 1. ORTEP drawing of 2-5a.
mined after acidic hydrolysis. In each case, the same ciently as well. The overall reaction efficiency is also
absolute configuration was obtained for compound 3 dependent on the electron density of the alkynes. As
demonstrating a good stereocontrol at the C*(1) posi- the electron density increased, the overall chemical
tion. The absolute configuration at C*(1) was R as yield of the PKR slightly decreased while the enantio-
shown in Scheme 1, when (R)-BINAP was employed selectivity increased. This might be attributed to the
as a chiral ligand.[8] (4) Comparable results were ob- parallel kinetic resolution mentioned previously.
tained in a one-pot operation consisting of both
APKR reaction and acidic hydrolysis.
The poor diastereoselectivity in this Rh(I)-cata-
lyzed reaction could be a potential drawback of this
As we have already noted that the efficiency and strategy,[4] However, when we carefully studied the
stereoselectivity of the reaction was sensitive not only enantioselectivity, this concern was minimized as the
to the electronic and steric characteristics of the li- major diastereomer was obtained with excellent enan-
gands, but also to the electron density of the alkyne tioselectivities (> 90% except one example, 1-5) and
substrate,[9] further optimizations were attempted with in decent yields (range of 44 to 59%). In addition,
various ligands (L1 to L7).
since each diastereomer had the same stereogenic
The ligand effects were first examined with substrate center at C*(1), a single product (3) substantially en-
1-3 as summarized in Table 2, revealing that (R)-p-Me- riched by one enantiomer was obtained upon trace
BINAP (L2) and (S)-Synphos (L5) are the best ligands acidic hydrolysis in wet THF, either from the separat-
with regard to yields and enantioselectivities.
ed diastereomer 2a and 2b or from the mixture of dia-
This result is contrary to those observed in the stereomers 2a and 2b. The combined yields of the two
study under the thermal conditions using a cationic steps were in the range 61–75% with enantiomeric ex-
Rh(I) catalyst at atmospheric CO pressure, in which cesses of the combined mixture generally greater than
the electron-deficient phosphorus ligands such as (R)- 80% (erꢀ9:1).
p-CF3-BINAP (L4) and (S)-Difluorphos (L6) provid-
Compound 1-1 having an electron-donating 4’-me-
thoxyphenyl substituent (entry 2 in Table 3) provided
ed better chemical yields and enantioselectivities.[9]
Although precedents indicated that the PKR reac- a mixture of 2-1a and 2-1b, respectively, in 32% and
tion can be accelerated by catalysts bearing the more 44% yield, with enantiomeric excesses of 68% and
electron-rich phosphine ligands and/or having a nar- 90% by using (S)-Synphos (L5). On the other hand,
rower dihedral angle in a transition intermediate,[9a] the substrate 1-4 having an electron-withdrawing sub-
the PKR was tainted by the formation of side prod- stituents such as 4-ClC6H4 (entry 10 in Table 3) af-
ucts resulting from simultaneously facilitated b-hy- forded an improved diastereoselectivity (2:1) with
dride elimination of the metallacyclopentene inter- (S)-Synphos (L5) but with slightly lower enantiomeric
mediate. However, in this case, the formation of the excess together with higher combined chemical yield
presumed catalyst, [(CO)RhClL*], resulted from the (62% ee and 27% yield for 2-4a, 90% ee and 59%
decarbonylation of cinnamaldehyde, may be signifi- yield for 2-4b, respectively).
cantly expedited by the ligand bearing the more elec-
tron-rich phosphorus.
Meanwhile, for the substrates (1-6 to 1-8, entries 11
to 16 in Table 3) having alkyl group substituents at
By carefully balancing electronic and steric factors, the alkynes, (R)-p-Me-BINAP (L2) turned out to be
(R)-p-Me-BINAP (L2) and (S)-Synphos (L5) turned the best ligand. The reactions employing (S)-Synphos
out to be the best ligands for this reaction (entries 2 (L5) afforded a substantially reduced chemical yield
and 5 in Table 2).
of the PKR product (entries 12, 14 and 16 in Table 3),
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Table 3. Asymmetric desymmetrization of the bisallenyl propargyl acetals 1 by an enantioselective PKR with (R)-p-Me-
BINAP (L2) and (S)-Synphos (L5).
Entry Substrate Ligand Time 2-a
2-b
3[a]
3[b]
Overall[c]
Overall[d]
[h]
Yield/ee[f]
Yield/ee[f]
Yield/ee[f]
Yield/ee[f]
Yield/ee[f]
Yield/ee[f]
[%] (config. [%] (config. [%] (config. [%] (config. [%] (config. [%] (config.
C1)
C1)
C1)
C1)
C1)
C1)
1
2
4’-
(R)-L2 1.5
30/75 (R)
32/68 (S)
46/80 (R)
44/90 (S)
82/74 (R)
78/70 (S)
84/80 (R)
82/90 (S)
63/78 (R)
61/83 (S)
64/76 (R)
68/85 (S)
CH3OC6H4 (S)-L5
(1-1)
1
3
4
4’-
CH3C6H4
(R)-L2 3
(S)-L5 1.5
32/65 (R)
30/64 (S)
44/87 (R)
48/92 (S)
82/65 (R)
84/64 (S)
82/85(R)
80/90 (S)
62/77 (R)
63/80 (S)
64/79 (R)
66/85 (S)
(1-2)
5
6
7
8
C6H5 (1-3) (R)-L2 3
(S)-L5 2.5
4’-ClC6H4 (R)-L2 3
36/65 (R)
30/67 (S)
40/64 (R)
27/62 (S)
36/58 (R)
40/63 (S)
65[e]
46/87 (R)
55/90 (S)
47/86(R)
59/90 (S)
50/77(R)
53/84 (S)
83/68 (R)
77/68 (S)
78/65 (R)
80/62 (S)
80/58 (R)
78/63 (S)
20–80[g]/97 (R)
20–90[g]/93 (S)
84/94 (R)
88/90 (S)
82/93 (R)
86/95 (S)
–
72/88 (R)
80/90 (S)
84/86 (R)
82/89 (S)
86/76 (R)
84/83 (S)
66/75 (R)
67/82 (S)
70/77 (R)
70/81 (S)
72/69 (R)
75/72 (S)
60/97 (R)
30/94 (S)
65/94 (R)
48/90 (S)
70/76 (R)
74/86(S)
74/81 (R)
76/83 (S)
80/69 (R)
(1-4)
(S)-L5 2.5
9
4’-CF3C6H4 (R)-L2 3
(1-5)
H (1-6)
10
11
12
13
14
15
16
17
18
(S)-L5 2.5
(R)-L2 1
80/77 (S)
[g]
[g]
(S)-L5
(R)-L2 1
(S)-L5
allyl (1–8) (R)-L2 1.5
(S)-L5
1
35[e]
Me (1-7)
77[e]
66/94 (R)
50/92 (S)
1
54[e]
78[e]
64/ꢀ95[f] (R) 70/ꢀ95[f] (R)
1
74[e]
64/95[f] (S)
–
–
64/95[f] (S)
TMS (1–9) (R)-L2 NR
(S)-L5 NR
–
–
–
–
–
[a]
[b]
[c]
[d]
[e]
[f]
Data for 3 obtained from 2-a.
Data for 3 obtained from 2-b.
Overall yield and enantioselectivity by weighted summation of the previous two data.
Data were obtained after one-pot operation of two reaction steps.
An inseparable mixture was obtained.
The ee were determined by NMR using a chiral shifting agent, EuACTHNUTRGNEUNG(hfc)3.
[g]
Due to the inherent instability of 3-6, yields of the isolated hydrolysis products were variable batch to batch. The reliable
chemical yield and full characterization were made after direct hydrogenation of 2-6 to 4 instead of hydrolysis
(Scheme 2).
consistent with side products arising from significant dride elimination rate, more significantly. And thus,
competition of b-hydride elimination of the metalla- the formation of the side products was suppressed to
cyclopentene intermediate.
a negligible level.
Fortunately, the catalyst bearing (R)-p-Me- BINAP
Most importantly, the alkyl-substituted substrates 1-
(L2) provided well-optimized results for these sub- 7 and 1-8 provided excellent enantioselectivities with
strates with complementary effects. The catalyst had (R)-p-Me-BINAP (L2) without sacrificing the chemi-
an electron-rich phosphorus ligand for facilitating the cal yields. The only practical difficulty encountered
decarbonylation of the aldehyde, a wider dihedral with these cases was that the PKR products were ob-
angle of the ligand in the transition intermediate tained as an inseparable mixture of diastereomers.
slowed the overall reaction rate,[9b] especially b-hy- Thus, we determined the chemical yield and measured
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Asymmetric Desymmetrization of the Diallyl Acetals of Alkynals
COMMUNICATIONS
(50 mg,
0.194 mmol)
in
cinnamaldehyde
(0.5 mL,
3.872 mmol, 20 equiv.) was placed in a flask under an atmos-
phere pressure of argon. The reaction mixture was stirred at
1208C for 1.5 h. After the completion of the reaction, the
crude mixture was purified by column chromatography on
silica gel with n-hexane/ethyl acetate (8/1, v/v) as an eluent
to give the corresponding products 2-1a (yield; 16 mg,
0.056 mmol, 30%) and 2-1b (yield: 24.0 mg, 0.084 mmol,
46%), respectively.
1-(Allyloxy)-6-(4-methoxyphenyl)-3a,4-dihydro-1H-cyclo-
penta[c]furan-5(3H)-one (2-1a): IR (KBr): n=1712 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=2.35 (dd, J=18.2, 3.0 Hz,
1H), 2.90 (dd, J=18.2, 6.4 Hz, 1H), 3.44 (dd, J=8.7, 8.4 Hz,
1H), 3.50–3.56 (m, 1H), 3.83 (s, 3H), 4.23 (dd, J=12.4,
6.3 Hz, 1H), 4.39 (dd, J=12.4, 5.5 Hz, 1H), 4.46 (dd, J=8.0,
8.0 Hz, 1H), 5.28 (d, J=10.2 Hz, 1H), 5.39 (dd, J=17.1,
0.6 Hz, 1H), 5.62 (s, 1H), 6.05 (dddd, J=17.1, 10.2, 6.3,
5.2 Hz, 1H), 6.94 (d, J=8.8 Hz, 2H), 7.59 (d, J=8.8 Hz,
2H); 13C NMR (75 MHz, CDCl3): d=39.7, 42.0, 55.5, 69.0,
71.3, 97.8, 114.3, 118.4, 123.1, 130.4, 134.1, 135.3, 160.5,
170.0, 208.2; HR-MS (EI+): m/z=286.1205 [M+], calcd. for
C17H18O4: 286.1205; [a]2D3: +100.9 (c 5.3, CH2Cl2); HPLC:
The ee value was determined as 75% by HPLC analysis
using a chiral column (DAICEL CHIRALPAK AS-H, n-
hexane/2-PrOH=9/1, flow 1.0 mLminÀ1, detection at
254 nm); retention time: 12.04 min (minor) and 20.39 min
(major).
Scheme 2. Further functionalization of 2-6.
the optical purity of products 3 after hydrolysis of a
mixture of diasteromers 2. The overall chemical yields
over two steps and the enantioselectivities obtained
for 1-7, and 1-8 were excellent: 65% together with
94% ee and 64% with 95% ee, respectively.
Even 1-6 having a terminal alkyne, previously con-
sidered to be too sensitive to the acidic cationic Rh(I)
catalyst, gave a high chemical yield as well as an ex-
cellent enantioselectivity (97% ee in 60% yield over
two steps). The compound 2-6 obtained by utilizing
(R)-L2 was readily transformed into 5, which may po-
tentially be a pivotal intermediate for the synthesis of
(+)-brefeldin A (6; Scheme 2).[10]
However, TMS-substituted subtrate 1-9 remained
inert to the Rh-catalyzed PKR conditions. Although
this behavior was contrary to the cobalt-promoted re-
action, it was consistent with previously reported ob-
servation with Rh(I)-catalyzed PKRs. The extension
of this method to bis(3-butenyl) acetals of alkynal (1,
n=2) was not successful as expected with the Rh(I)
catalyst.
In conclusion, we have demonstrated that the asym-
metric desymmetrization of the diallyl acetals of alky-
nal (1) by enantioselective Pauson–Khand reaction
catalysts based on a neutral Rh(I) catalyst provided a
useful enantioselective synthesis of bicyclic or mono-
cyclic compounds (2 or 3) in excellent chemical yields
as well as enantioselectivities. These products will
serve as pivotal intermediates for the enantioselective
synthesis of biologically interesting compounds, such
1-(Allyloxy)-6-(4-methoxyphenyl)-3a,4-dihydro-1H-cyclo-
penta[c]furan-5(3H)-one (2-1b): IR (KBr): n=1712 cmÀ1
;
1H NMR (300 MHz, CDCl3): d=2.39 (dd, J=17.6, 3.9 Hz,
1H), 2.76 (dd, J=17.6, 6.3 Hz, 1H), 3.26–3.35 (m, 1H), 3.60
(dd, J=10.8, 7.9 Hz, 1H), 3.82 (s, 3H), 4.09 (dd, J=12.7,
6.3 Hz, 1H), 4.17 (dd, J=12.7, 5.4 Hz, 1H), 4.27 (dd, J=7.9,
7.7 Hz, 1H), 5.07 (d, J=17.1 Hz, 1H), 5.11 (d, J=9.4 Hz,
1H), 5.73 (dddd, J=17.1, 9.4, 6.3, 5.4 Hz, 1H), 6.09 (s, 1H),
6.90 (d, J=8.8 Hz, 2H), 7.53 (d, J=8.8 Hz, 2H); 13C NMR
(75 MHz, CDCl3): d=40.6, 44.2, 55.5, 69.7, 70.6, 99.0, 113.8,
118.3, 122.5, 130.8, 133.7, 137.6, 160.2, 172.7, 208.0; HR-MS
(EI+): m/z=286.1203 [M+], calcd. for C17H18O4: 286.1205;
[a]2D3: À38.1 (c 8.0, CH2Cl2); HPLC: The ee value was deter-
mined as 80% by HPLC analysis using a chiral column
(DAICEL CHIRALPAK AS-H, n-hexane/2-PrOH=9/1,
flow 1.0 mLminÀ1, detection at 254 nm); retention time:
14.41 min (minor) and 25.71 min (major).
Hydrolysis of the PKR Products
A mixture of 1-(allyloxy)-6-(4-methoxyphenyl)-3a,4-dihy-
dro-1H-cyclopenta[c]furan-5(3H)-one
(2-1-a)
(16 mg,
0.056 mmol) and p-toluenesulfonic acid (1.3 mg, 0.007 mmol,
as iridoids and brefeldine. The results will be reported 3 mol%) in THF/water (3 mL/0.5 mL) was stirred at 808C
for 6 h. The reaction mixture was quenched with a saturated
aqueous solution of sodium bicarbonate (3 mL) and extract-
ed with ethyl acetate (2 mLꢃ3). The combined organic
layer was washed with brine, and then dried over anhydrous
magnesium sulfate. After filtration of the insoluble materi-
als, the filtrate was concentrated under reduced pressure.
The residue was purified by flash chromatography of silica
gel with n-hexane/ethyl acetate (3/1, v/v) as an eluent to
give 3-1 as an oil; yield: 11.3 mg (0.046 mmol, 82% yield).
The ee was determined by HPLC analysis using a chiral
in due course.
Experimental Section
The Asymmetric Desymmetrization
A mixture of [Rh
BINAP (L2, 15.8 mg, 0.023 mmol) or (S)-Synphos (L5), 1-
[3,3-bis(allyloxy)prop-1-ynyl]-4-methoxybenzene (1-1)
ACHTUNGTRENNUNG(COD)Cl]2 (4.8 mg, 0.010 mmol), (R)-tol-
N
column specified. IR (KBr): n=3437, 1712, 1670 cmÀ1
;
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Dong Eun Kim et al.
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1H NMR (300 MHz, CDCl3): d=2.54 (dd, J=19.3, 1.9 Hz,
1H), 2.81 (dd, J=19.3, 7.2 Hz, 1H), 3.40–3.44 (m, 1H),
3.81–3.89 (m, 2H), 3.86 (s, 3H), 6.99 (d, J=8.6 Hz, 2H),
7.40 (d, J=8.6 Hz, 2H), 10.13 (s, 1H); 13C NMR (75 MHz,
CDCl3): d=39.6, 39.7, 55.7, 64.2, 114.5, 120.7, 132.1, 152.6,
157.7, 161.7, 193.4, 208.0; HR-MS (EI+): m/z=246.0870
[M+], calcd. for C14H14O4: 246.0892; [a]2D3: +60.5 (c 3.8,
CH2Cl2); HPLC: The ee value was determined as 74% by
HPLC analysis using a chiral column (DAICEL CHIRAL-
PAK AS-H, n-hexane/2-PrOH=2/1, flow 1.5 mLminÀ1, de-
tection at 254 nm); retention time: 7.84 min (minor) and
11.41 min (major).
[2] a) N. Jeong, in: Comprehensive Organometallic Chemis-
try III, Vol 11, (Eds.: R. Crabtree, M. P. Mingos),
Elsevier, Oxford, 2006, pp 335–366; b) N. Jeong, in:
Modern Rhodium-Catalyzed Organic Reactions, (Ed.:
P. A. Evans), Wiley-VCH, Weinheim, 2005, pp 215–
240; c) N. Jeong, in: Transition Metals In Organic Syn-
thesis: Building Blocks and Fine Chemicals, Vol. 1,
(Eds.: M. Beller, C. Bolm), Wiley-VCH:, Weinheim,
1998, pp 560–577; d) N. Jeong, B. K. Sung, Y. K. Choi,
J. Am. Chem. Soc. 2000, 122, 6771–6772; e) N. Jeong,
B. K. Sung, J. S. Kim, S. B. Park, S. D. Seo, J. Y. Shin,
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[3] N. Jeong, D. H. Kim, J. H. Choi, Chem. Commun. 2004,
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Acknowledgements
[4] a) N. Jeong, B. Y. Lee, S. H. Lee, Y. K. Chung, S-G.
Lee, Tetrahedron Lett. 1993, 34, 4023–4026; b) J. Velc-
icky, J. Lex, H-G. Schmalz, Org. Lett. 2002, 4, 565–568;
c) J. Velcicky, A. Lanver, J. Lex, A. Prokop, T. Wieder,
H-G. Schmalz, Chem. Eur. J. 2004, 10, 5087–5110;
d) A. Lanver, H-G. Schmalz, Eur. J. Org. Chem. 2005,
1444–1458.
This work was supported by a Korea Science and Engineer-
ing Foundation (KOSEF) grant (No. R01-2007-000-10534-0)
and by the Korea Research Foundation Grant (KRF-2007-
313-C00414) funded by the Korean Government (MOST and
MOEHRD), respectively.
[5] D. E. Kim, I. S. Kim, V. Ratovelomanana-Vidal, J-P.
GenÞt, N. Jeong, J. Org. Chem. 2008, 73, 7985–7989.
[6] a) T. Shibata, K. Takagi, J. Am. Chem. Soc. 2000, 122,
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Kakiuchi, Tetrahedron Lett. 2004, 45, 9163–9166; d) T.
Shibata, N. Toshida, K. Takagi, J. Org. Chem. 2002, 67,
7446–7450.
[7] CCDC 696219 contains the supplementary crystallo-
graphic data for this paper. These data can be obtained
free of charge from The Cambridge Crystallographic
Data Centre via www.ccdc.cam.ac.uk/data_request/cif.
[8] The absolute configuration at C*(1) of 2-3b obtained
with (R)-L2 was determined as R by comparison of the
retention time of 2-3b in HPLC analysis with the data
previously reported in ref.[4c]
[9] a) D. E. Kim, C. Choi, I. S. Kim, S. Jeulin, V. Ratovelo-
manana-Vidal, J.-P. GenÞt, N. Jeong, Synthesis 2006, 23,
4053–4059; b) D. E. Kim, C. Choi, I. S. Kim, S. Jeulin,
V. Ratovelomanana-Vidal, J.-P. GenÞt, N. Jeong, Adv.
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