Silver-catalyzed carbon dioxide incorporation and rearrangement on propargylic derivatives

Article abstract of DOI:10.1246/bcsj.20110078

A silver/DBU catalyst system was developed for the effective synthesis of cyclic carbonate and oxazolidinone from the reaction of CO₂ with propargylic alcohols and propargylic amines, respectively, in high yields under mild conditions. It was f

Full text of DOI:10.1246/bcsj.20110078

698
Bull. Chem. Soc. Jpn. Vol. 84, No. 7, 698–717 (2011)
© 2011 The Chemical Society of Japan
BCSJ Award Article
Silver-Catalyzed Carbon Dioxide Incorporation and
Rearrangement on Propargylic Derivatives
Satoshi Kikuchi, Shunsuke Yoshida, Yuudai Sugawara, Wataru Yamada, Hau-Man Cheng,#,³
Kosuke Fukui, Kohei Sekine, Izumi Iwakura,## Taketo Ikeno, and Tohru Yamada*
Department of Chemistry, Keio University, Hiyoshi, Kohoku-ku, Yokohama 223-8522
Received March 8, 2011; E-mail: yamada@chem.keio.ac.jp
A silver/DBU catalyst system was developed for the effective synthesis of cyclic carbonate and oxazolidinone from
the reaction of CO2 with propargylic alcohols and propargylic amines, respectively, in high yields under mild conditions.
It was found that the [3,3]-sigmatropic Meyer-Schuster-type rearrangement of the propargylic alcohol was mediated by
CO2 in DMF to afford the corresponding ¡,¢-unsaturated carbonyl compounds in high yields. The silver salt combined
with the chiral Schiff base ligand could be applied to enantioselective chemical CO2 incorporation into various
bispropargylic alcohols to produce the corresponding cyclic carbonate in high yields with high enantioselectivity. The
absolute configuration was determined by VCD spectroscopy as well as by X-ray analysis. These products were found to
be active for the aminolysis reaction to afford the corresponding carbamate derivatives in high yields without any loss of
optical purity.
An enormous amount of energy has been generated by
It was recently found that a catalytic amount of a silver salt
as a ³-Lewis acid to activate an alkyne combined with the use
of DBU is an efficient catalyst system for the reaction of CO2
with propargylic derivatives. We now report that a silver
salt/DBU combination catalyzes the reaction of CO2 with
propargylic alcohols10a and propargylic amines10b to produce
the corresponding cyclic carbonates and oxazolidinones in
good to excellent yields, respectively. We also describe that a
Meyer-Schuster-type rearrangement is mediated by CO2 in the
presence of a catalytic amount of silver methanesulfonate and a
base to afford the corresponding enones in high yields.11 We
also describe the asymmetric incorporation of CO2 into
bispropargylic alcohol catalyzed by a chiral silver salt derived
from silver acetate and Schiff base ligand to give the
corresponding chiral cyclic carbonate in good to excellent
yields with high enantioselectivity.12 The reaction mechanism
postulated by a computational approach, the determination of
the absolute configuration of the optically active cyclic
carbonate using VCD spectroscopy and X-ray analysis, and
the application of an optically active cyclic carbonate for
aminolysis, is also reported.
the oxidation of hydrocarbons in order to make our life
comfortable and convenient while generating an enormous
amount of CO2 worldwide.1 Because the most oxidized form of
the carbon derivatives is much less reactive, its application to
organic synthesis has been considered to be one of the
most challenging research topics. As well as the chemical
fixation of CO2, much effort has been made to utilize CO2 as an
attractive C1 feedstock for organic synthesis due to its
ubiquitous, abundant, and nontoxic properties, however due
to its lower reactivity, harsh reaction conditions are required to
activate and incorporate CO2 into organic compounds.2 It is
necessary to develop a mild reaction system including catalysts
to efficiently capture CO2 into a wide variety of substrates,
especially fine-chemicals. Various synthetic reactions of CO2
have been reported. Typically enol derivatives,3 Grignard
reagents,4 and alkyllithium compounds5 readily react with
CO2 to afford the corresponding carboxylic acids, though a
stoichiometric amount of a strong nucleophile is employed.
Transition-metals, such as nickel,6 rhodium,7 palladium,8
copper,2e,9 and gold,2e can catalyze the reaction of CO2 to
produce the corresponding carboxylic acid and lactone deriv-
atives. However, it is required to prepare in advance reactants
containing a boron, halogen moiety, etc., and the scope and
applicability are limited.
Results and Discussion
Reaction of CO2 with Propargylic Alcohols. Numerous
reports13 have been published for the synthesis of cyclic
carbonates from CO2 with a propargylic alcohol. Although
many catalysts including metal salts and phosphines have been
developed to demonstrate this reaction, harsh reaction con-
ditions are required to achieve high yields, and terminal
³ Present address: Chemical Synthesis Laboratory at Biopolis,
Institute of Chemical and Engineering Science, ASTAR,
Singapore
Published on the web June 25, 2011; doi:10.1246/bcsj.20110078

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
699
O
BH+
Table 1. Screening of Various Metals for the Catalytic CO2
Incorporation Reaction
O
O
R3
OH
O
O
O
10 mol% Metal Salt
DBU (1.0 equiv)
CO2
O
O
R1
OH
R3
R3
R2
R2
M+
O
Base
R2
R1
R1
+
CO2
M
CH2Cl2, rt
Ph
Ph
O
1b
2b
BH+
O
Entrya)
Metal salt
Yield/%b)
+
M
+
Base
O
R1
1
2
3
4
5
6
7
8
9
[Rh(acac)3]
Hg(OTf)2
PtCl2
PdCl2
Pd(OAc)2
CuCl
AuCl
AgClO4
AgOTs
no reaction
no reaction
no reaction
no reaction
trace
trace
no reaction
quant.
R3
R2
Scheme 1. Proposed mechanism of CO2 incorporation into
propargylic alcohols.
alkynes are the only applicable substrates for these carbonate
formations. Supercritical conditions have also been employed
for the CO2 incorporation into propargylic alcohols including
internal alkynes in the presence of the phosphine catalyst.14
However, the applicable substrates are still limited to aryl-
substituted propargylic alcohols without any bulky group on
the propargylic position.
quant.
a) Reaction conditions: The reaction was carried out in 1.0 mL
of dichloromethane using 10 mol % metal salt as catalyst,
0.25 mmol DBU and 0.25 mmol of the substrate 1b under
2.0 MPa CO2. b) Isolated yield.
Screening of Metal Salts for a Catalyst: The reaction
mechanism of the CO2 incorporation into propargylic alcohols
was assumed to be as follows. The alcohol, activated by
the amine base, would react with the CO2 to generate a
carbonate intermediate. An intramolecular ring-closing reac-
tion would then proceed on the alkyne, which would be
activated by the metal complex to afford the corresponding
cyclic carbonate with the release of the metal complex catalyst
(Scheme 1).
Table 2. Examination of Counter Anion in Silver Salt Catalysts
10 mol% AgX
DBU (1.0 equiv)
O
OH
O
CO2
+
O
Ph
CH2Cl2, r.t.
Ph
1g
2g
Entrya)
AgX
Yield/%b)
The activation of the alkyne by the metal complex catalyst
was proposed to be crucial to promote the present reaction. The
nucleophilic addition to the acetylenes activated by metal salts
is a promising strategy that can be used to obtain various
alkenes. For example, it was reported that an intramolecular
nucleophilic ring-closing reaction of the carbonate onto the
propargylic derivatives activated by a gold(I) catalyst afforded
the corresponding cyclic carbonates.15 We screened various
transition-metal salts to activate the C-C triple bond with the
use of the phenyl-substituted alkyne 1b as a model substrate at
room temperature under a CO2 pressure of 2.0 MPa (Table 1).
Unfortunately, almost none of the metals, such as rhodium,
mercury, platinum, and palladium, that were expected to
activate the alkynes, could catalyze the reaction (Entries 1-5).
The copper(I) salt produced a trace amount of the cyclic
carbonate and gold was inactive for the present reaction
(Entries 6 and 7). It was found that by using silver salts as a
catalyst in the presence of a stoichiometric amount of DBU,
the cyclic carbonate 2b was quantitatively obtained (Entries 8
and 9).
Next, examination of the counter anion of the silver salt was
performed for the reaction of the propargylic alcohol possess-
ing an alkyl-substituted internal alkyne 1g which had lower
reactivity than the phenyl-substituted alkyne 1b (Table 2). In
the presence of 10 mol % silver perchlorate, the reaction
smoothly proceeded to afford the cyclic carbonate 2g with an
83% yield (Entry 7). Other silver salts could catalyze the
incorporation reaction (Entries 1-6), but silver cyanide pro-
duced a 38% yield and the starting propargyl alcohol was
1
2
3
4
5
6
7
8
AgCN
38
66
67
67
68
77
83
84
84
95
AgOTf
Ag2CO3
AgBF4
AgF
AgSbF6
AgClO4
AgOMs
AgOAc
AgOAc
9
10c)
a) Reaction conditions: The reaction was carried out in 1.0 mL
of dichloromethane using a 10 mol % metal salt as catalyst,
0.25 mmol DBU and 0.25 mmol of the substrate 1g under
1.0 MPa CO2. b) Isolated yield. c) The reaction was carried out
in toluene.
recovered (Entry 1). The most efficient silver salt was found to
be silver methanesulfonate or silver acetate. They successfully
catalyzed the conversion of 1g into the corresponding cyclic
carbonate 2g in high yields (Entries 8 and 9). When the reaction
was carried out in toluene at a 1.0 MPa CO2 pressure, the
chemical yield improved to 95% (Entry 10).
Application to Various Propargylic Alcohols:
The
combined catalyst system of silver acetate with a stoichiometric
amount of DBU was successfully applied to various pro-
pargylic alcohols (Table 3). In the presence of 10 mol % silver
acetate and 1.0 equivalent of DBU at room temperature, the
terminal alkyne 1a bearing bulky substituent reacted with CO2

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Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
Table 3. Various Cyclic Carbonates Obtained from Propargylic Alcohols by the Silver-Catalyzed CO2 Incorporation
10 mol% AgOAc
O
OH
O
DBU
R3
CO2
(1.0 MPa)
+
O
R3
R1
R2
toluene, rt
5 h
R1
R2
1
2
Entrya)
1
Carbonate
Yield/%b)
Entrya)
13
Carbonate
Yield/%b)
O
O
O
O
O
2a
2b
85
2h
quant.
O
Ph
Ph
Et
O
O
2
3c),d)
4d),e)
quant.
86
98
O
O
O
O
14
15
2i
96
95
O
Ph
O
O
Ph
Ph
Ph
Ph
O
O
O
5
6
2c
2d
2e
quant.
95
2j
Et
O
O
O
O
O
O
O
O
Ph
16
17
2k
21
96
76
Ph
Ph
Ph
O
O
O
O
7f)
8
80
quant.
MeO
O
O
O
O
9f)
10
84
96
THPO
O
Ph
2f
18
19
2m
2n
97
91
O
O
Ph
O
Si
11f)
12
81
95
O
O
O
2g
O
O
Ph
a) Reaction conditions: The reaction was carried out in 1.0 mL of toluene using 10 mol % silver acetate,
0.25 mmol DBU and 0.25 mmol substrate under a 1.0 MPa CO2 pressure. b) Isolated yield. c) Carried out
using 10 mol % of DBU. d) Reaction time: 24 h. e) Carried out using 1.0 mol % silver acetate under a
1.0 MPa CO2 pressure. f) Carried out under atmospheric CO2 pressure.
to afford the corresponding cyclic carbonate 2a in 85% yield
(Entry 1). The internal alkyne 1b was quantitatively converted
into the cyclic product 2b under 1.0 MPa CO2 (Entry 2).
A catalytic amount of the base effectively promoted the
reaction to afford the product in high yield (Entry 3). The lower
catalyst loading of 1.0 mol % silver acetate effectively cata-
lyzed the reaction of the alcohol 1b at 1.0 MPa CO2 to form
the carbonate 2b in high yield, though a longer time
was required to complete the reaction (Entry 4). The more
bulky propargylic alcohols 1c and 1d were smoothly converted
into the corresponding cyclic carbonates 2c and 2d in high
yields, respectively (Entries 5 and 6). The reaction of
the propargylic alcohols having a5-membered ring 1e or
6-membered ring 1f smoothly proceeded in excellent yields
(Entries 8 and 10). Even under atmospheric CO2 pressure, the
propargylic alcohols 1e-1g could be converted with excellent
selectivities (Entries 7, 9, and 11). The alkyl-substituted
propargylic alcohols have never been reported for the incor-
poration reaction of CO2, whereas in the present catalyst
system, they were capable of reacting with CO2 to afford the
cyclic carbonates 2g-2k in high yields (Entries 12-16). It is
noted that the propargylic alcohols with ether and acetal
functions were smoothly converted into the corresponding
products 2l and 2m in high yields without any loss of reactivity
(Entries 17 and 18). The silyl-protected propargylic alcohol
was subjected to the present reaction to afford the cyclic
carbonate with the silyl-protected form 2n in high yield
(Entry 19). The geometry of the carbon-carbon double bond in
the product 2k was determined by X-ray analysis and it was
revealed that the Z-isomer was obtained as the sole product
(Figure 1). Product 2b was also found to have the Z-form by
comparing the chemical shift of the olefinic proton with the

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
701
O
Table 4. Examination of Various Reaction Conditions
O
O
AgOAc
DBU
NH2
O
O
NH
Ph
CO2
+
toluene, rt
Ph
(Z)
3a
4a
CO2 pressure AgOAc
DBU
Time
/h
Yield
O
O
Entrya)
/MPa
/mol % /mol %
/%b)
O
(Z)
Ph
1
2
3
4
5
6c)
1.0
0.1
1.0
1.0
1.0
0.3
10
10
10
10
3
100
100
5
0
0
2
6
23
46
47
47
95
95
94
87
93
91
2k
Figure 1. The structure of the CO2-incorporated cyclic
carbonate 2k.10a
2
0
a) Reaction conditions: The reaction was carried out in 1.0 mL
of toluene with 0.25 mmol of substrate at room temperature.
b) Isolated yield. c) The reaction was carried out in 1.5 mL of
toluene with 0.50 mmol of substrate.
2c : 2.2%
2d : 1.0%
2e :14.3%
2f : 7.1%
2i : 2.5%
2j : 9.0%
2l : 6.0%
2m : 5.0%
O
O
H
R1
O
As a model compound of an N-unsubstituted propargylic
amine with an internal alkyne, 1-(phenylethynyl)cyclohexan-
amine (3a) was first subjected to the standard conditions in
the presence of 10 mol % silver acetate and a stoichiometric
amount of DBU in toluene at 1.0 MPa CO2 pressure and room
temperature, and the corresponding oxazolidinone 4a was
obtained in 95% yield in 2 h (Table 4, Entry 1). The reaction
preceeded so smoothly that milder reaction conditions were
examined involving the CO2 pressure and the amounts of
the silver catalyst and DBU in the reaction of 3a at room
temperature (Table 4). Under atmospheric CO2 pressure, the
corresponding product was obtained in an excellent yield
(Entry 2). A catalytic amount of the base effectively promotes
the reaction to afford the product in excellent yield (Entry 3).
It was found that in the absence of DBU, the product was
obtained in 87% yield (Entry 4). The mechanism for the present
reaction was assumed to be that the carbamate intermediate
derived from the propargylic amine with CO2 successively
reacted with the alkyne activated by the silver catalyst to afford
the oxazolidinone via an intramolecular ring-closing reaction.
Although the DBU base would assist with the carbamate forma-
tion, in equilibrium between the corresponding ammonium
carbamate and free propargylic amine in a CO2 atmosphere,17j
the amine could work as a base to assist with the carbamate
formation without DBU. The reaction was also catalyzed by
3 mol % silver acetate to produce an excellent yield (Entry 5).
In the reaction with 2 mol % silver acetate under 0.3 MPa CO2
pressure, the propargylic amine 3a was completely consumed to
afford the product in excellent yield (Entry 6).
R2
H
2g
2n
: 9.0%
: 1.0%
2h : 3.0%
NOE
Figure 2. NOE experiment of the cyclic carbonates 2.
reported value.13f All other cyclic carbonates were obtained as
the sole isomer based on NMR spectroscopic analysis, and
they were suggested to be the Z-isomer by NOE experiments.
A correlation between the olefinic proton and the methyl
or methylene protons bound to the C-4 carbon on the
5-alkylidene-4,4-disubstituted-1,3-dioxolan-2-one ring of the
products 2c, 2d, 2e, 2f, 2g, 2h, 2i, 2j, 2l, 2m, and 2n was
detected. The intensities (%) of the signals are shown
(Figure 2). These observations suggested that a nucleophilic
ring-closing step proceeded with activation of the alkyne by the
silver catalyst at the anti-position against the carbonate
nucleophile.
Application to Propargylic Amines: The present catalytic
system could be applied to various propargylic amines to afford
the corresponding oxazolidinones. Oxazolidinones have been
employed as reliable auxiliaries for various selective synthetic
organic reactions. Oxazolidinones have been conventionally
prepared from the corresponding 2-aminoalcohols with phos-
gene,16 however its high toxicity and environmental burden
have been seriously considered. The oxazolidinone preparation
from CO2 is one of the most attractive synthetic methods not
using phosgene. Much effort has been made to develop the
chemical fixation of CO2 into propargylic amines to provide
oxazolidinone derivatives.13n,17 In spite of various reports on
the incorporation of CO2 into propargylic amines, practical
procedures for the reaction of the propargylic amines with
internal alkynes or N-unsubstituted amines have never been
achieved. Also, it should be pointed out that the applicable
substrates are still limited and/or almost all the reported
methods required severe reaction conditions, such as high
temperature and/or high pressure the same as the reaction of
propargylic alcohols.
Various solvents were screened expecting effective solvation
of the carbamate intermediate to accelerate the reaction
(Table 5). In MeOH and CHCl3 solvents, the product was
obtained in low yields (Entries 1 and 2). In THF, the reaction
proceeded as smoothly as in toluene though a longer reaction
time was required (Entry 3). When DMF was employed as the
solvent, the reaction was dramatically accelerated to afford the
product in 98% yield after 4 h (Entry 4). Various aprotic polar
solvents then were examined under milder reaction conditions
(Entries 5-8). Under atmospheric CO2 pressure, propargylic

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Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
O
Table 5. Examination of Various Solvents
O
O
(Z)
O
NH
NH2
Ph
O
2 mol% AgOAc
NH
Ph
CO2
+
solvent, 25 °C
4a
N
Ph
O
3a
4a
Entrya) Solvents CO2 pressure/MPa Time/h Yield/%b)
(Z)
1
2
3
4
5
6
7
8
MeOH
CHCl3
THF
DMF
DMF
MeCN
DMA
DMSO
0.3
0.3
0.3
0.3
0.1
0.1
0.1
0.1
47
47
47
4
10
10
10
10
19
32
94
98
97
91
92
98
Figure 3. The structure of the CO2-incorporated oxazoli-
dinone 4a.10b
4a : 7.0% 4l : 3.0%
4e : 4.0% 4m : 3.0%
a) Reaction conditions: The reaction was carried out in 1.5 mL
of solvent with 0.50 mmol of substrate at 25 °C. b) Isolated
yield.
O
O
4f : 5.0% 4n : 7.0%
4g : 2.0% 4o : 4.0%
4h : 4.0% 4p : 6.0%
4i : 5.0% 4q : 5.0%
4j : 4.0% 4r : 6.0%
4k : 3.0%
O
H
O
H
NR2
R3
NR2
R3
R1
R1
or
amine 3a smoothly reacted with CO2 in aprotic polar solvents,
especially in DMSO, and the corresponding oxazolidinone 4a
was obtained in 98% yield after 10 h (Entry 8).
H
H
NOE
NOE
The optimized catalytic system was successfully applied to
the reaction of various propargylic amines (Table 6). Prop-
argylic amines with terminal alkyne and primary, secondary,
and tertiary N-substituted amines were converted into the
corresponding oxazolidinones 4b-4e in excellent yields (Entries
1-4). For the less reactive substrates, a 0.4 MPa CO2 pressure
was required to achieve an excellent yield (Entries 3, 4, and 11).
Also, the reaction of N-unsubstituted propargylic amines with
the terminal alkyne 3f proceeded in high yield (Entry 5). The
N-substituted internal alkynes, alkyl-substituted alkyne 3g and
3h and aryl-substituted alkyne 3i-3l, reacted with CO2 to afford
the corresponding oxazolidinone in high yield (Entries 6-11). It
should be pointed out that in the present catalytic system, the
N-unsubstituted propargylic amines with an internal alkyne,
which have never been reported as being involved in a CO2
incorporation reaction, were smoothly converted into the
corresponding cyclic products under mild conditions. The
alkyl-substituted (3m, Entry 12), aryl-substituted (3n-3t,
Entries 13-20), and heteroaryl-substituted (3u and 3v, Entries
21 and 22) alkynes were converted into the corresponding
oxazolidinones in high yield. As for the exo-olefin structure, all
products were obtained as a sole isomer based on an NMR
spectroscopic analysis, and they were suggested to be the
Z-isomer by NOE experiments. The geometry of the C-C
double bond in product 4a was confirmed to be the Z-isomer by
X-ray analysis (Figure 3). In the NOE experiments, a correla-
tion between the olefinic proton and the methyl or methylene
protons bound to the C-3 or C-4 carbon on the oxazolidinone
ring of the products 4a and 4e-4r was detected, respectively.
The intensities (%) of the signals are indicated in Figure 4.
Rearrangement Reaction Mediated by Carbon Dioxide.
During the course of examining the reaction conditions for
the CO2 incorporation reaction into propargylic alcohols, the
corresponding ¡,¢-unsaturated carbonyl compounds via the
Meyer-Schuster-type reaction was detected as a by-product in
Figure 4. NOE experiment of the oxazolidinone 4.
some polar solvents. In a toluene solution, the silver-catalyzed
reaction of propargyl alcohol with CO2 selectively afforded the
corresponding cyclic carbonate, while in dichloromethane and
chlorobenzene, the corresponding ¡,¢-unsaturated carbonyl
compounds via the Meyer-Schuster-type reaction were ob-
tained along with the cyclic carbonate.
The Meyer-Schuster rearrangement18 reaction reported in
192219 is the rearrangement of propargylic alcohol into
the corresponding ¡,¢-unsaturated carbonyl compounds. This
reaction consists of two key steps: (1) effective enhancement of
the leaving ability of the hydroxy group to generate the
carbocation intermediate, and (2) nucleophilic addition of the
hydroxide equivalent to the activated alkyne to afford the
resulting enone. For a tertiary propargylic alcohol, a protic acid
was used as a simple reagent to drive this reaction though the
Rupe rearrangement via the enyne intermediate to afford the
undesired ¡,¢-unsaturated carbonyl compounds as by-prod-
ucts. In order to suppress the side reactions in this textbook
reaction,20 oxo-metallic reagents21,22 have been examined
to concomitantly remove the hydroxy group with the [3,3]-
sigmatropic rearrangement involving the nucleophilic addition
to an alkyne, but a high reaction temperature is required to
almost complete these reactions.23 The high affinity of the late
transition-metals, such as gold,24 to the acetylenic ³-bond
was used to activate the propargylic alcohols under the mild
conditions. The ruthenium complex catalyst25 was employed
for the activation of the alkyne via the vinylidene-ruthenium
intermediate derived from the terminal alkynes.
Screening of Metal Salt Catalysts: Several metal salts
were screened as a catalyst. Rhodium, palladium, iridium, and
copper(I) were not active for the reaction, whereas platinum,
mercury, and gold could catalyze the reaction to afford the

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
703
Table 6. Various Propargylic Amines
O
O
NHR4
2 mol% AgOAc
DMSO, 25 °C
NR4
CO2
(0.1 MPa)
+
R3
R2
R1
R1
R3
R2
3
4
Entrya)
Oxazolidinone
Time/h Yield/%b)
Entrya)
11c),d)
Oxazolidinone
Time/h Yield/%b)
O
O
O
NPMB
O
1
4b
7.0
7.0
95
4l
24
98
Ph
NBn
O
O
O
O
O
NPMB
2
4c
97
99
12
4m
4n
7.0
77
97
NH
Ph
n-C5H11
O
O
3c),d)
4d
32
13
14
5.0
3.0
O
NPMB
NH
Ph
Ph
O
O
O
O
4c),d)
4e
4f
72
83
95
99
4o
4p
4a
99
NPMB
NH
i-Pr
O
O
O
O
O
NH
5
6
4.0
15
16
4.0
quant.
98
NH
Ph
Ph
R
O
O
NH
R = Ph
O
4g
3.0
1.5
10
NBn
R =
17
18
4q
4r
2.5
3.0
94
99
O
MeO
7
O
4h
95
NBn
n-C5H11
R =
R =
F
O
O
O
O
NiPr
8
9
4i
2.0
1.5
99
99
19
20
4s
4t
7.0
2.5
94
Ph
Ph
O
NiPr
R =
4j
quant.
F3C
Ph
S
N
O
21
22
4u
4v
3.0
7.0
97
89
R =
R =
O
10
4k
3.0
97
NPMB
Ph
a) Reaction conditions: The reaction was carried out in 1.5 mL of DMSO with 2 mol % silver acetate and 0.50 mmol of substrate under
0.1 MPa CO2 pressure at 25 °C. b) Isolated yield. c) PMB: p-Methoxybenzyl. d) 0.4 MPa of CO2 pressure.

704
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
Table 7. Examination of Various Silver Salts
OH
10 mol%AgX
O
CO2 (1.0 MPa)
DBU in formamide
Ph
Ph
1g
6a
Entrya)
AgX
Time/h
Yield/%b)
Entrya)
AgX
Time/h
Yield/%b)
1
2
3
4
5
6
AgCl
AgI
AgF
AgSbF6
AgOTs
AgOAc
10
8
12
12
12
12
trace
trace
68
73
74
7
8
9
10
11
12
AgOTf
Ag2O
AgOCOCF3
AgNO3
AgBF4
20
12
11
12
11
8
76
78
79
80
85
89
76
AgOMs
a) Reaction conditions: The reaction was carried out in 0.5 mL of formamide with 10 mol % silver salt,
0.25 mmol of substrate and 0.2 equiv of DBU at 60 °C under 1.0 MPa CO2 pressure. b) Isolated yield.
corresponding ¡,¢-unsaturated carbonyl compounds. A silver
salt was found to be the best catalyst for this reaction among
them. Various silver salts were next examined for the reaction
of propargylic alcohol 1g in formamide under CO2 pressure
(1.0 MPa). Among the silver halides examined, only silver
fluoride affected the reaction to afford the corresponding enone
6a in 68% yield (Table 7, Entries 1-3). Almost all the cationic
silver salts which were investigated catalyzed the synthesis of
the ¡,¢-unsaturated carbonyl compounds in good yields
(Entries 4-11). It was found that silver methanesulfonate was
the best catalyst for the Meyer-Schuster-type rearrangement
mediated by CO2 to produce the corresponding ¡,¢-unsaturat-
ed carbonyl compound in high yield (Entry 12).
Table 8. Examination of Various Solvents
OH
10 mol% AgOMs
CO2 (0.1 MPa)
DBU, solvent, rt
Ph
1g
O
O
O
O
Ph
+
Ph
2g
6a
Enone
Carbonate
Yield/%b)
Carbonate 2g Enone 6a
Entrya)
Solvent
Time/h
Examination of Reaction Solvents: The optimization of
several solvents for the Meyer-Schuster-type rearrangement
mediated by CO2 was performed (Table 8). In a toluene
solution, the silver-catalyzed reaction of propargylic alcohol
with CO2 selectively afforded the corresponding cyclic carbon-
ate (Entry 3), while in dichloromethane and chlorobenzene, the
corresponding ¡,¢-unsaturated carbonyl compounds via the
Meyer-Schuster-type reaction was obtained along with the
cyclic carbonate (Entries 1 and 2). The polar solvents, such as
DMF and DMA, improved the selectivity toward the enone
(Entries 4-7). Finally, it was found that formamide was the best
solvent to selectively obtain the corresponding enone (Entry 8).
Various Propargylic Alcohols: The optimized system was
successfully applied to various propargylic alcohols (Table 9).
In the presence of 10 mol % silver methanesulfonate and
0.2 equivalent DBU under 1.0 MPa CO2 at 60 °C, the alkyl-
substituted tertiary propargylic alcohols 1g and 5b were
smoothly converted into the corresponding ¡,¢-unsaturated
ketones 6a and 6b in high yield (Entries 1 and 2). The
propargylic alcohol 5c possessing bulky substituents was also
converted into the corresponding enone 6c in high yield
(Entry 3) when a 3.0 equivalents DBU was employed at 60 °C.
For the propargylic alcohols 1j, 1k, and 5f with a five-to-seven-
membered ring, the reactions smoothly proceeded under mild
conditions using a 1.0 equivalent diisopropylethylamine to
afford the rearranged products 6d-6f with the cycloalkylidene
groups in 93%, 90%, and 94% yields, respectively, without any
isomerization of the C-C double bond. The propargylic
alcohols 1i and 5h with a phenyl group at the propargylic
1
2
3
CH2Cl2
PhCl
toluene
2-propanol
DMF
DMF
DMA
formamide
24
24
24
48
72
12
12
12
45
79
74
trace
trace
7
39
11
trace
51
39
73
4c)
5
6d)
7d)
8d)
16
6
63
86
a) Reaction conditions: The reaction was carried out in 0.5 mL
of solvent using 10 mol % silver methanesulfonate, 0.25 mmol
of substrate and 0.25 mmol of DBU at room temperature under
atmospheric CO2 pressure. b) Isolated yield. c) Carried out at
50 °C. d) Carried out under 1.0 MPa CO2 pressure.
position were capable of reacting with CO2 to afford the
corresponding enones 6g in 98% yield (Entry 7) and 6h in 80%
yield in DMF (Entry 8). The present catalytic system could be
applied to various tertiary as well as secondary propargylic
alcohols to afford the products 6j and 6k in high yield at room
temperature (Entries 10 and 11), although it has been reported
that the secondary propargylic alcohols were difficult to convert
into the corresponding ¡,¢-unsaturated ketones under mild
conditions. However, the propargylic alcohol 5l was less
reactive and the corresponding monosubstituted enone 6l was
obtained in 29% yield (Entry 12). The ethoxy-substituted
propargylic alcohols 5m and 5n were good substrates that
afforded the corresponding ethyl esters of the ¡,¢-unsaturated
carboxylic acids 6m and 6n in high yields (Entries 13 and 14).

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
705
O
Table 9. Transformation of Various Propargyl Alcohols into
the Enones
O
O
R3
OH
R3
Ag+
O
O
path a
a
O
b
O
R2
OH
in toluene
R1
R3
10 mol% AgOMs
R2
CO2
DBU
R2
R1
R1
R2
R2
R3
R1
Ag+
CO2 (1.0 MPa)
DBU in formamide
R1
Cyclic Carbonates
R3
path b
[3,3]-sigmatropic
rearrangement
1 and 5
6
in DMF
Entrya)
1d)
Enone
Time/h Yield/%b) (E/Z)c)
O
O
C O
O
6a
6b
6c
6d
6e
8
24
25
24
48
89
74
70
93
90
O
O
Ph
Ph
Ph
Ph
O
R3
R1
R3
R2
O
O
O
Et
R1
R2
Enones
2d)
3e)
4f)
5f)
Et
i-Pr
i-Pr
Scheme 2. Reaction mechanism of propargylic alcohol with CO2.
[3,3]-sigmatropic rearrangement into the allene-enolate. The
¡,¢-unsaturated carbonyl compounds resulted from releasing
CO2 (Scheme 2, path b). It is reasonable to assume that
the polarized structure with the elongated C-O bond in
the carbonate intermediate would be stabilized in a polar
solvent to enhance the attack on the ¢-carbon of the activated
propargylic alcohol.
The reaction of the propargylic alcohol 1a with CO2 was
monitored by time-resolved FT-IR spectroscopy in the presence
of 10 mol % AgOAc and one equivalent of DBU. Two
experiments were performed; one of the reaction systems was
that substrate, DBU, and CO2 (0.1 MPa) were placed in the
reaction vessel and then AgOAc was added. For the other,
DBU was added last. In each experiment, the specific
absorptions of the product immediately appeared at ca. 1810
O
Ph
O
O
O
O
6f)
6f
40
94
Ph
Ph
7f)
8g)
6g
6h
6i
47
96
19
48
48
72
19
54
98 (46/54)
80
Ph
Ph
Ph
9g)
84
n-Hex
¹1
O
O
O
(C=O stretching vibration) and 1700 cm (C=C stretching
10
6j
93 (75/25)
84 (76/24)
29
vibration) after the addition of AgOAc and DBU (the red line
in the Figures 5 and 6). These observations suggested that the
all reaction components (silver salt and DBU as a base) were
required to allow this reaction. It was assumed that the
cyclization step would be very fast to afford the corresponding
cyclic carbonate 2a, which would support the proposed
mechanism for the cyclic carbonate and oxazolidinone as
shown in Scheme 2.
The proposed mechanism for the ¡,¢-unsaturated carbonyl
compound was also supported by an isotopic experiment using
C18O2. The reaction was carried out under a CO2 atmosphere to
afford the ¡,¢-unsaturated ketone with MW: 188, whereas the
¡,¢-unsaturated ketone with MW: 190 was obtained from
C18O2. As shown in Figure 7, no crossed product with 16O
could be detected at all by GC-MS analysis. Under a nitrogen
atmosphere, no reaction proceeded. These observations sug-
gested that the present reaction should be promoted by CO2 and
that the rearrangement step should proceed in an intramolecular
[3,3]-sigmatropic manner, not by the intermolecular addition of
H2O or the carbonate anion.
Ph
Ph
11
6k
6l
Et
12
Ph
O
O
13f)
14f)
6m
6n
87 (46/54)
70 (79/21)
EtO
Ph
Ph
EtO
a) Reaction conditions: The reaction was carried out in 0.5 mL
of formamide with 10 mol % silver methanesulfonate,
0.25 mmol of substrate and 1.0 equiv of DBU at rt under
1.0 MPa CO2 pressure. b) Isolated yield. c) E/Z ratio is shown
in parenthesis. d) 0.2 equiv of DBU was used at 60 °C. e) 3.0
equiv of DBU was used at 60 °C. f) i-Pr2NEt was used as a
base. g) The reaction was carried out in DMF.
Proposed Mechanism: The reaction mechanism of the
reaction of CO2 with propargylic alcohol is proposed as
follows: the carbonate intermediate would be generated from
propargylic alcohol and CO2 and then intramolecular ring-
closing would proceed at the ¡-carbon of the propargylic
alcohol, which is activated by the silver salt, to afford the cyclic
carbonate (Scheme 2, path a). The ¢-carbon of the propargylic
alcohol would be alternatively attacked to promote the
The computational approach for the reaction mechanism
was performed using the Gaussian 03 program26 with the
B3LYP/6-31+G*// B3LYP/6-31+G* method and basis set
(The 3-21G* basis set was employed instead of 6-31+G* for
the Ag atom.) and Gaussian 09 program27 for the single-point
energy including the SCRF/PCM approach. As a model
substrate, 2-methyl-3-pentyn-2-ol was adopted for the repre-

706
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
1) toluene
1) toluene
2) AgOAc
O
O
O
O
OH
OH
AgOAc
DBU
2) DBU
O
O
3) CO2
3) CO2
Ph
Ph
Ph
Ph
1b
2b
1b
2b
Figure 6. Time-resolved FT-IR measurement for the reac-
tion of propargylic alcohol 1b.
Figure 5. Time-resolved FT-IR measurement for the reac-
tion of propargylic alcohol 1b.
16O
Ph
MW. 188
18O
Ph
MW. 190
Figure 7. MS spectrum of the enone obtained from CO2 and the 18O-labeled CO2.
sentative of propargylic alcohol, and 1-methyl-1,4,5,6-tetrahy-
dropyrimidine for the DBU base. As shown in Figure 8,
the anion 7a derived from the alcohol with the amine base
reacted with CO2 to produce compound 7b which was more
7e or the alkyne in compound 7c. The DBU coordination to
compound 7c afforded the structure 7f in ca. 30 kcal mol as
¹1
the coordination energy to afford compound 7f (ZPE: ¹216.3
kcal mol¹1) or the structure 7g (ZPE: ¹215.2 kcal mol¹1). The
silver ion would then coordinate on the alkyne versus the
carbonate which would be coordinated by the DBU ammonium
salt. This would be attributed to the most anionic carbonate and
the repulsion between the silver and DBU ammonium ions.
These calculations suggested that compound 7f would be
formed as an active species, although the reaction pathway was
not clear. We then analyzed the cyclization mechanism from
the active species 7f.
¹1
stable than the starting alcohol 7a in ca. 25.1 kcal mol (ZPE:
¹1
¹25.1 kcal mol
) (Relative energy was established as
¹1
0.0 kcal mol including the zero point revision. After this,
we indicated the energy including zero point revision.).
Compound 7b was coordinated by the silver ion in ca.
¹1
160 kcal mol as the coordination energy (compounds 7c-7e;
7c (ZPE: ¹182.5 kcal mol¹1), 7d (ZPE: ¹182.6 kcal mol¹1), 7e
(ZPE: ¹180.0 kcal mol¹1)). Two possible structures were
obtained for the coordination of the silver ion versus the
carbonate; it coordinates on the carbonate in compounds 7d and
The energy of the 5-membered TS 7h (ZPE: ¹190.3
kcal mol¹1) and the energy of the 6-membered TS 7i (ZPE:

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
707
O
O
O
O
CH3
CH3
CH3
CH3
H3C
H3C
7a (0.0 kcal mol−1)
7b (-25.1 kcal mol−1)
O
O
Ag
O
O
Ag
O
O
O
O
O
Ag
CH3
CH3
CH3
CH3
CH3
CH3
H3C
H3C
H3C
7c (-182.5 kcal mol−1)
7d (-182.6 kcal mol−1)
7e (-180.0 kcal mol−1)
H
N
CH3
O
N
N CH3
O
N
H
O
O
O
Ag
O
Ag
CH3
CH3
CH3
CH3
H3C
H3C
7g (-215.2 kcal mol−1)
7f (-216.3 kcal mol−1)
Figure 8. 2-Methyl-3-pentyn-2-ol as a model substrate for the cross section.
¹187.8 kcal mol¹1) were determined (Figure 9). The activation
energies were 26.0 and 28.5 kcal mol¹1, respectively. An
IRC (intrinsic reaction coordinate) analysis showed that
the Z-5-membered cyclic carbonate was obtained from
the intermediate 7j via the 5-membered TS 7h, and the
6-membered intermediate 7k was produced via the 6-mem-
bered TS 7i. The activation energy of the 6-membered
Z-5-membered cyclic carbonate was predominantly obtained
in the gas phase, since the rate-determining step was the
6-membered TS 7i.
As indicated in Table 8, the carbonate was predominantly
obtained in toluene and PhCl, while the enone was preferen-
tially produced in DMF and formamide. We next tried
the single-point calculation including the solvent effect with
the PCM model (Table 10). As a result, it was found that the
activation energy between the 5-membered TS 7h and the
6-membered TS 7i tended to become close depending on the
increase in the polarity of the solvent in the order of toluene,
CH2Cl2, DMF, and formamide. Although the activation energy
¹1
intermediate 7k was 13.0 kcal mol and the decarbonation
reaction of the intermediate 7k proceeded to afford the
corresponding enone via TS 7l and the intermediate 7m.
This observation suggested that the formation pathway of
the enone consisted of two steps, but it was thought that the

708
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
Energy /
kcal mol-1
O
O
-180
-190
-200
-210
-220
-230
O
O
O
O
7i
H3C
H3C
Ag
O
O
Ag
O
7h
7l
O
H3C
Ag
O
O
O
7j
H3C
Ag
H3C
O
Ag
7k
O
CH3
C
N
O
O
O
7f
Ag
O
N
H3C
O
H
O
7m
Ag
H3C
The counter ammonium was omitted for simplify
in the structures 7i, 7h, 7j, 7k, 7l, and 7m.
Figure 9. The energy diagram for cyclic carbonate and enone preparations.
Table 10. The Acitivation Energya) and Selectivity in Several Solvents
Calculated
Experimental
Yield/%
Entry
Solvent
¹1
Activation energy with ZPE/kcal mol
¦E
5-Membered TS (7h)
6-Membered TS (7i)
Carbonate 2g
Enone 6a
1
2
3
4
toluene
CH2Cl2
DMF
20.547
16.993
16.186
16.221
22.396
18.306
16.717
16.680
1.85
1.31
0.53
0.46
74
45
7
trace
39
73
formamide
6
86
a) PCM-B3LYP/6-31+G*// PCM-B3LYP/6-31+G*.
O
O
cat.
AgX
OH
O
O
O
cat. Chiral ligand : L*
O
*
R1
R2
R2
Ag+ / L*
R2
CO2
R1
R1
R1
R1
R1
Scheme 3. Enantioselective chemical incorporation of CO2 into bispropargylic alcohols.
between the two pathways did not reverse in the calculation of
the model substrate, this observation shows that the polarity of
the solvent was crucial for the ratio between the cyclic
carbonate and the enone, and this tendency was consistent with
the fact that the carbonate was preferentially obtained in the
nonpolar solvent, while the enone was predominantly formed
in the polar solvent.
Enantioselective Version of CO2 Incorporation into
Bispropargylic Alcohols. Based on the reaction mechanism
in the silver-catalyzed CO2 incorporation reaction into the
propargylic alcohols, supported by the computational approach,
the silver catalysts effectively activated the C-C triple bond as
a ³-Lewis acid on the side opposite the carbonate anion, and
then the intramolecular cyclization proceeded to selectively
afford the corresponding cyclic product with the (Z)-exo-
alkene, the corresponding optically active cyclic carbonates
would be obtained by using an optically active silver catalyst,
which is in rapid equilibrium between the two alkynes in the
bispropargylic alcohols, and a nucleophilic attack selectively
proceeds on one of the C-C triple bonds with asymmetric
desymmetrization (Scheme 3).
Screening of Optically Active Ligands: Various optically
active ligands were first examined, such as ferrocene deriva-
tives, BINAP, BOX, and Py-BOX (Table 11). In the presence
of 10 mol % silver acetate with the ligand, model compound 8a
was treated with 15 mol % of DBU in CH2Cl2 under 1.0 MPa
CO2 pressure at room temperature. Although all the reactions
proceeded to afford the corresponding cyclic carbonates, the
corresponding products were obtained without any enantio-
selectivity (Entries 1-4 and 6). It was assumed that the DBU

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
709
Table 11. Examination of Various Chiral Ligands with DBU
in 96% yield with 40% ee and in 92% yield with 70% ee,
respectively (Entries 4 and 5). In the presence of 5 mol % silver
acetate with a 6 mol % chiral ligand at 5 °C, the enantiomeric
excess was slightly improved (Entry 6), while the product was
obtained in low yield with 82% ee at ¹10 °C (Entry 7). It was
found that in the presence of excess amounts of silver acetate
with respect to the chiral ligand, the enantiomeric excess was
slightly improved (Entry 8) and the product was obtained with
83% ee at 5 °C (Entry 9).
10 mol% AgOAc
12 mol% L*
15 mol% DBU
O
OH
O
O
*
Ph
CO2 (1.0 MPa)
Ph
Ph
CH2Cl2, r.t.
Ph
8a
9a
Time/h Yield/%b) Ee/%c)
Entrya)
L*
Under these reaction conditions, various chiral Schiff
base ligands were then screened (Table 13). By using the
ligand possessing a phenyl (Entry 1) or sterically bulky
substituent (Entries 2 and 3), the reaction proceeded, but
a low enantiomeric excess was observed. The selectivity was
also moderate when an unsymmetrical chiral ligand derived
from L-valine amide (Entry 4) or a ligand possessing a five-
membered ring backbone (Entries 5 and 6). The effect of
side chains were examined using the silver complexes
possessing a cyclohexyl backbone (Entries 7-14). Only a trace
amount of product was obtained with the pyrrole or 4-pyridyl
side chain (Entries 7 and 9). The ligands possessing a quinoline
(Entry 10) or substituted-pyridine group (Entries 11-14) on the
side chain afforded the corresponding cyclic carbonate with a
good enantiomeric excess, while the ligands with thiazole on
the side chains gave moderate results (Entry 8). It was
eventually found that the chiral ketimine ligand 10b was the
best ligand for both the reactivity and the selectivity. By using
the ligand 10b, the bispropargylic alcohol 8a was completely
consumed to afford the corresponding product in excellent
yield with a high enantiomeric excess (Entry 15).
NMe2
1
2.5
61
0
Fe
PPh2
2
6
25
4
PPh2
O
O
3
4
2.5
1
82
70
2
3
N
N
t-Bu
t-Bu
O
O
N
N
N
i-Pr
i-Pr
5d)
6
2
94
93
26
5
N
N
For the reaction with over 2 equivalents of AgOAc versus
the chiral ligand 10b, almost the same enantiomeric excess was
observed (Table 14, Entries 3-8 and 10-12). This observation
0.3
N
N
1
7d)
2
96
40
was confirmed by the H NMR spectroscopic titration of the
N
N
silver acetate and chiral ketimine ligand 10b; the chemical
shifts of Ha, Hb, and Hc of ligand 10b gradually shifted to low
field when the ratio of AgOAc to ligand 10b increased, while
using over 2 equivalents of AgOAc versus the chiral ligand
10b, these chemical shifts became constant. That is, it
suggested that the silver acetate and chiral ketimine ligand
10b would form the corresponding 2:1 complex (Figure 10).
After examination of the loading ratio of the ligand/silver, a
combination of 3 mol % silver acetate and 1 mol % of 10b was
found to be the best conditions to realize high selectivity
(Table 14, Entry 5). When the reaction was carried out at 0 °C,
the CO2-incorporated carbonate was obtained up to 92% ee
(Table 14, Entry 13).
10a
a) Reaction conditions: The reaction was carried out in 1.5 mL
of CH2Cl2 with 0.25 mmol of substrate under 1.0 MPa CO2
pressure. b) Isolated yield. c) Enantiomeric excess was
determined by HPLC analysis using Daicel Chiralcel OD-H.
d) Reaction was carried out without DBU.
could strongly coordinate the silver catalyst to block the
coordination by the chiral ligand, while (¹)-sparteine was
employed as a chiral ligand without DBU to afford the
corresponding cyclic product with a 26% ee (Entry 5). Without
DBU, several chiral ligands were then screened and the product
was obtained with 40% ee using the chiral Schiff base ligand
10a28 derived from 1,2-diaminocyclohexane and 2-pyridine-
carbaldehyde (Entry 7).
Various reaction conditions involving the solvent, catalyst
loading, and temperature were examined in the presence of the
ligand 10a (Table 12). In the DMF and THF solvents, the
product was obtained in moderate yield and ee (Entries 1 and
2). In toluene, the selectivity was improved to afford the
product with a 71% ee, however, the reactivity was low
(Entry 3). When CH2Cl2 and CHCl3 were employed as the
solvents, the reaction proceeded to afford the cyclic carbonate
Determination of Absolute Configuration: Although we
tried to determine the absolute configuration of the carbonate
9a by X-ray analysis, an appropriate single crystal for X-ray
analysis could not be obtained. The absolute configuration was
then determined by VCD measurements combined with the
corresponding spectra predicted by the DFT calculations.29
VCD (vibrational circular dichroism) has received much
attention in recent years to nonempirically determine absolute
configuration. The VCD spectra were obtained using a JASCO
¹1
FVS-6000 spectrometer at the resolution of 4 cm using a
CDCl3 solution in a 50 ¯m BaF2 cell. The concentrations were
0.115 M and the baselines for the spectra were the VCD spectra

710
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
Table 12. Examination of Various Reaction Conditions
cat. AgOAc
cat. L* : 10a
O
L*
OH
O
N
N
O
*
+
CO2
(1.0 MPa)
Ph
solvent
Ph
Ph
N
N
10a
Ph
8a
9a
Entrya)
Solvent
AgOAc/mol %
L*/mol %
Temp/°C
Time/h
Yield/%b)
Ee/%c)
1
2
3
4
5
6
7
8
9
DMF
THF
10
10
10
10
10
5
5
5
5
12
12
12
12
12
6
6
1
1
rt
rt
rt
rt
rt
18
21
21
2
63
40
27
96
92
92
11
90
91
6
56
71
40
70
75
82
75
83
toluene
CH2Cl2
CHCl3
CHCl3
CHCl3
CHCl3
CHCl3
5
5
48
168
20
96
¹10
20
5
a) Reaction conditions: The reaction was carried out in 1.5 mL of solvent with 0.25 mmol of substrate
under 1.0 MPa CO2 pressure. b) Isolated yield. c) Enantiomeric excess was determined by HPLC analysis
using Daicel Chiralcel OD-H.
of CDCl3. Products 9a obtained with (R,R)- and (S,S)-10b were
recrystallized over n-hexane to prepare >99% ee cyclic
carbonates for the VCD measurement. The absolute config-
uration of 9a was determined by comparison of the exper-
imental and calculated VCD spectra. The IR and VCD spectra
of 9a were theoretically calculated based on the density
functional theory at the B3LYP/6-31G(d,p) level (blue line in
Figures 11 and 12). The scaling factor of 0.97 was employed.30
A conformational analysis provided only one stable conformer
for 9a. All of the calculations were conducted using the
Gaussian 0331 program code. The observed VCD spectrum of
9a obtained with (S,S)-10b (green line in Figure 12) was
identical to the calculated spectrum of (R)-9a (blue line in
Figure 12). Therefore, it was concluded that (R)-9a was
obtained from the reaction catalyzed by the silver complex
with a chiral ligand (S,S)-10b.
The absolute configuration of the carbonate 9a was also
confirmed by an X-ray analysis of the 9a-cobalt carbonyl
complex (Figure 13). The product 9a obtained with (R,R)-10b
was recrystallized over n-hexane to prepare the >99% ee cyclic
carbonate. The obtained enantiomerically pure 9a was treated
with [Co2(CO)8] in heptane to afford the corresponding 9a-
cobalt carbonyl complex (Scheme 4).32 The result of the X-ray
analysis revealed that the (S)-9a was obtained as the Z-isomer
in the reaction catalyzed by the complex with (R,R)-10b.
Various Bispropargylic Alcohols: The optimized catalytic
system was successfully applied to various bispropargylic
alcohols (Table 15). In the presence of 3 mol % silver acetate
and 1 mol % ligand 10b under a 1.0 MPa CO2 pressure at 0 °C,
the phenyl-substituted bispropargylic alcohols 8a and 8b were
converted into the corresponding cyclic carbonates 9a and 9b
in the excellent yields with 92% ee and 93% ee, respectively
(Entries 1 and 2). The reaction of the fluoromethyl-substituted
propargylic alcohol 8c also proceeded in high yield with a high
ee (Entry 3). Though the bispropargylic alcohol with a homo-
benzyl substituent 8d was less reactive than the other phenyl-
substituted alcohols, the cyclic product 9d was obtained
without affecting the enantioselectivity (Entry 4). The isopro-
pyl-substituted alkyne 8e reacted with CO2 to afford the
corresponding carbonate 9e in high yield with a high ee
(Entry 5). Due to the steric bulkiness, the alkyne 8f was less
reactive and the corresponding product 9f was obtained in 58%
yield with an 82% ee (Entry 6). Bispropargylic alcohols with a
substituted phenyl 8g-8j were also good substrates that
afforded the corresponding cyclic carbonates 9g-9j in excellent
yields with good to high enantiomeric excesses regardless of
the electron-donating and -withdrawing substituents (Entries
7-10). The enantiomer-enriched conjugated cyclic carbonate
9k was also obtained in high yield with an 80% ee (Entry 11).
The alkyl-substituted alkyne with a protective group in the
molecule 8l was converted into the corresponding cyclic
product 9l in excellent yield with a moderate enantioselectivity
(Entry 12). As for the exo olefin structure, all products were
obtained as the sole isomer based on NMR spectroscopic
analysis, and they were suggested to be the Z-isomer based on
the NOE experiments.
The Application for Aminolysis Reaction: The obtained
optically active cyclic carbonate was found to afford the
corresponding carbamates via the aminolysis reaction without
any loss of enantioselectivity. Although a protocol to produce
the carbamate was recently reported involving the reaction of
an amine, internal propargylic alcohol and CO2,33 a high
reaction temperature was required within the limitation of the
secondary amines. Milder reaction conditions should be
developed for the stereoselective aminolysis of a wide variety
of amines.
The reactions of the obtained optically active cyclic carbon-
ate 9a with various amines were carried out in THF at 5 °C
(Table 16). Secondary amines, such as diethylamine, pyrrol-
idine, and morpholine, produced the corresponding carbamate
11a-11c in high to excellent yields while maintaining the
enantioselectivity, however the reaction of diethylamine re-
quired 24 h to consume the optically active cyclic carbonate 9a
(Entries 1-3). The reaction of aliphatic primary amines, such as
tert-butylamine, iso-propylamine, and propylamine, also pro-
ceeded to afford the corresponding products 11d-11f in

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
711
Table 13. Examination of Various Chiral Schiff Base Ligands
O
O
5 mol% AgOAc
1 mol% L*
OH
O
Ph
+
CO2
(1.0 MPa)
*
CHCl3, 5 °C
Ph
Ph
Ph
8a
Time/h Yield/%b) Ee/%c)
9a
Entrya)
L*
Entrya)
L*
Time/h Yield/%b) Ee/%c)
Ph
N
Ph
N
1
96
64
89
87
4
N
N
R'
R'
N
N
R¤ =
7
2-pyrrolyl
40
trace
2
27d)
N
N
8
9
2-thiazolyl
4-pyridyl
2-quinolyl
2-pyridyl
136
48
67
trace
76
53
N
N
t-Bu
N
t-Bu
N
3
4
42
94
96
90
3
10
11
12
92
80
82
72
N
N
i-Pr
82
91
37d)
N
N
2-(3,5-di-Me-pyridyl)
92
92
N
N
Bn
N
13
14
2-(6-Me-pyridyl)
42
42
84
91
83
76
5
6
86
96
93
70
30
58
N
N
2-(4-Me2N-pyridyl)
N
N
N
N
N
N
15
22
97
89
N
N
N
N
10b
a) Reaction conditions: The reaction was carried out in 1.5 mL of CHCl3 with 0.25 mmol of substrate under 1.0 MPa CO2 pressure.
b) Isolated yield. c) Enantiomeric excess was determined by HPLC analysis using Daicel Chiralcel OD-H. d) Major isomers were
different form other entries.
excellent yields without any loss of enantioselectivity although
their reactivities were lower than the secondary amines (Entries
4-6). An allylamine was also found to be an appropriate amine
for the reaction to produce the corresponding carbamate 11g in
96% yield with the same enantioselectivity (Entry 7).
various tertiary and secondary propargyl alcohols were effi-
ciently promoted by CO2 to afford the corresponding ¡,¢-
unsaturated carbonyl compounds in high yield. The former
reaction selectively proceeded in toluene, whereas the latter in
polar solvents, such as DMF. It was found that the enantiose-
lective chemical CO2 incorporation into various bispropargylic
alcohols was achieved by the combined use of a catalytic
amount of silver acetate and chiral Schiff base ligand. These
products were active for the aminolysis reaction to afford the
corresponding carbamate derivatives in high yields without any
loss of enantioselectivity.
Conclusion
It is noted that the silver catalyst system could be used for
various CO2 incorporation reactions; in the presence of DBU,
the cyclization of CO2 with propargylic alcohols and prop-
argylic amines stereoselectively proceeded to afford the
corresponding cyclic carbonate derivatives and oxazolidinone
derivatives, respectively, as a Z-isomer in high chemical yields
under mild reaction conditions. By using the present catalyst
system, the [3,3]-sigmatropic Meyer-Schuster-type reaction of
Experimental
General. The 1H and 13C NMR spectra were recorded with
a JOEL model AL-400 or ¡-400 spectrometer using CDCl3 as

712
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
Shift Change of Ha
Table 14. The Effect of AgOAc/L*10b Ratio
2.7
2.65
2.6
O
AgOAc
OH
O
L* : 10b
O
*
Ph
+
CO2
(1.0 MPa)
CHCl3, 5 °C
Ph
Ph
Ph
8a
9a
δ
2.55
2.5
AgOAc
/mol % /mol %
L*
AgOAc Time Yield
Ee
/%c)
Entrya)
Ha
Ha
Hb
Hb
/L*
/h
/%b)
N
N
2.45
2.4
1
2
3
4
5
6
7
8
9
10
11
12
13d)
1
1.5
2
2.5
3
4
5
7
2
4
1
1
1
1
1
1
1
1
4
2
2
2
1
1/1
1.5/1
2/1
2.5/1
3/1
4/1
5/1
7/1
1/2
2/1
22
20
22
24
22
22
22
22
12
11
12
11
48
94
98
92
92
97
92
97
87
90
98
90
96
98
81
84
88
88
90
89
89
88
84
88
89
89
92
N
N
Hc
Hc
10b
2.35
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
The ratio of AgOAc to 10b
Shift Change of Hb
4.6
4.5
4.4
4.3
4.2
4.1
4
5
6
3
2.5/1
3/1
3/1
δ
a) Reaction conditions: The reaction was carried out in 1.5 mL
of CHCl3 with 0.25 mmol of substrate under 1.0 MPa CO2
pressure at 5 °C. b) Isolated yield. c) Enantiomeric excess was
determined by HPLC analysis using Daicel Chiralcel OD-H.
d) Carried out at 0 °C.
Ha
Ha
Hb
Hb
N
N
N
N
Hc
Hc
3.9
3.8
10b
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
the solvent. The IR spectra were measured with a Thermo
Electron Corporation model NICOLET 6700 FT-IR spectrom-
eter. The melting points were measured with a Stanford
Research Systems MPA100. The gas chromatograph mass
spectra were obtained using a Shimadzu model GCMS-QP5000
spectrometer equipped with a DB-1 (Agilent Technologies,
Inc.) GC column. The ESI high-resolution mass spectra were
obtained using a Waters LCT Premier XE mass spectrometer.
Column chromatography was conducted on silica gel (Kanto
60 N). The dehydrated THF was purchased from Kanto
Chemical Co., Inc., and used without further purification.
Diethylamine, pyrrolidine, morpholine, tert-butylamine, iso-
propylamine, propylamine, and allylamine were distilled before
use. The HPLC analyses were performed using a Shimadzu
LC-6A and/or LC-10A chromatograph equipped with a chiral
column (Daicel Chiralcel OD-H, Daicel Chiralcel OZ-H, or
Chiralpak IA); the peak areas were obtained with a Shimadzu
SPD-M10AVP diode array detector/Shimadzu Class-VP or
JASCO MD-2010 plus multiwavelength detector/ChromNAV.
The optical rotations were recorded with JASCO P-2200 digital
polarimaters. The VCD spectra were measured with a JASCO
The ratio of AgOAc to 10b
Shift Change of Hc
8.75
8.7
δ
8.65
8.6
Ha
Ha
Hb
Hb
N
N
N
N
8.55
8.5
Hc
Hc
10b
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
The ratio of AgOAc to 10b
Figure 10. Changes in chemical shift with AgOAc/10b
ratio.
Copies of the data can be obtained free of charge via
http://www.ccdc.cam.ac.uk/conts/retrieving.html (or from the
Cambridge Crystallographic Data Centre, 12, Union Road,
Cambridge, CB2 1EZ, UK; Fax: +44 1223 336033; e-mail:
deposit@ccdc.cam.ac.uk).
General Procedure for the Synthesis of Cyclic Carbon-
ate. To a solution of propargylic alcohol 1 (0.25 mmol) in
toluene (1.0 mL) was added AgOAc (4.1 mg, 0.025 mmol)
and DBU (38.0 mg, 0.25 mmol). The reaction mixture was
stirred under 1.0 MPa CO2 pressure at room temperature. After
the reaction was complete, the product was purified by silica
gel column chromatography to afford the corresponding
carbonate 2.
¹1
FVS-6000 spectrometer at a resolution of 4 cm using a
CDCl3 solution in a 50 ¯m BaF2 cell with an MCT detector.
The React IR· 4000 system (Mettler-Toledo International,
Inc.) equipped with a SiComp ATR probe was used for the
time-resolved FT-IR measurements. The analysis software for
the React IR· 4000 system was iC IR· (Ver. 4.0). The data of
compounds 2,10a 4,10b 6,11 and 912 had been already reported in
previous papers, respectively. Crystallographic data have been
deposited with Cambridge Crystallographic Data Centre:
Deposition numbers CCDC-635752, -734834, and -773512
for compound 2k, 4a, and 9a-cobalt complex, respectively.

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
713
O
O
AgOAc
OH
O
O
(R,R)-10b
[Co2(CO)8]
O
*
O
*
Ph
Ph
CO2
CHCl3
n-heptane
Ph
Ph
Ph
Ph
9a
8a
Co2(CO)6
Scheme 4. Synthesis of 9a-cobalt complex.
a: 9a obtained with (R,R)-10b (Experiment (CDCl3 solution))
b: 9a obtained with (S,S)-10b (Experiment (CDCl3 solution))
c: (R)-9a (Calculation (B3LYP/6-31G(d,p))
O
*
O
3000
2500
2000
1500
1000
500
O
Ph
Ph
9a
O
O
O
CH3
*
OC
OC Co
Co
CO
CO
OC
OC
9a-Cobalt complex
O
O
O
CH3
(S)
0
2000
1800
1600
1400
1200
1000
Wavenumber / cm-1
9a
Figure 11. Calculated and experimental IR spectra.
Figure 13. The absolute configuration of 9a-cobalt
complex.
a: 9a obtained with (R,R)-10b (Experiment (CDCl3 solution))
b: 9a obtained with (S,S)-10b (Experiment (CDCl3 solution))
c: (R)-9a (Calculation (B3LYP/6-31G(d,p))
General Procedure for the Meyer-Schuster-Type Rear-
rangement Mediated by CO2. To a solution of propargyl
alcohol 1 (or 5) (0.25 mmol) in formamide (0.5 mL) was added
silver methanesulfonate (5.1 mg, 0.025 mmol) and DBU
(7.5 mg, 0.050 mmol). The reaction mixture was stirred at
60 °C under 1.0 MPa CO2 pressure. After the reaction was
complete, purification by silica gel column chromatography
gave the corresponding enone 6.
O
O
8E-08
6E-08
4E-08
2E-08
0
O
Ph
Ph
9a
The Procedure for the Isotopic Experiment Using C18O2.
To a solution of propargyl alcohol 1g (41.7 mg, 0.25 mmol) in
DMF (0.5 mL) was added silver methanesulfonate (5.1 mg,
0.025 mmol) and DBU (37.5 mg, 0.25 mmol). The reaction
mixture was stirred at room temperature under atmospheric
C18O2 pressure for 3 days. After the reaction mixture was
analyzed by GC-MS, purification by silica gel column
chromatography (EtOAc/hexane, 1:50) gave the corresponding
enone-18O 6a in 38% yield.
1950
1750
1550
1350
1150
950
-2E-08
-4E-08
-6E-08
-8E-08
Wavenumber / cm-1
General Procedure for the Reaction of Bispropargylic
Alcohol with CO2. A mixture of AgOAc (1.3 mg, 7.5 ¯mol)
and 10b (0.8 mg, 2.5 ¯mol) in CHCl3 (0.5 mL) was stirred for
30 min in the dark under air. To this mixture was added
bispropargylic alcohol 8 (0.25 mmol) in CHCl3 (1.0 mL). The
reaction mixture was pressurized to 1.0 MPa in an autoclave
after the vessel was purged three times with carbon dioxide,
which was then stirred at 0 °C. After the reaction was complete,
purification by silica gel column chromatography gave the
corresponding cyclic carbonate 9.
Figure 12. Calculated and experimental VCD spectra.
General Procedure for the Synthesis of Oxazolidinone.
To a solution of propargylic amine 3 (0.50 mmol) in DMSO
(1.5 mL) was added AgOAc (1.7 mg, 0.01 mmol). The reac-
tion mixture was stirred at 25 °C under atmospheric CO2
pressure. After the reaction was complete, purification by
silica gel column chromatography gave the corresponding
oxazolidinone 4.

714
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
Table 15. Enantioselective Carbon Dioxide Incorporation into Various Bispropargylic Alcohols
O
cat. AgOAc
cat. L* : 10b
OH
O
R2
O
*
R1
+
CO2
R1
(1.0 MPa)
R2
N
N
CHCl3
R1
N
N
R1
10b
8
9
Entrya)
Products
Time/h Yield/%b) Ee/%c)
Entrya)
Products
Time/h Yield/%b) Ee/%c)
O
O
O
O
*
O
O
1d)
48
44
98
92
7d)
46
99
90
Ph
Ph
*
F
Me
9g
Ph
9a
O
O
O
O
*
O
O
*
MeO
F3C
2d)
98
93
8d)
46
97
87
Me
9h
Et
Ph
9b
OMe
O
O
O
O
*
O
O
*
3e)
40
93
91
91
90
9e)
78
96
90
79
79
Ph
Ph
Me
F
9i
Ph
Ph
9c
CF3
O
O
Br
O
O
O
*
O
*
4f)
140
10h)
168
Me
Ph
9j
9d
Br
O
O
O
O
O
*
O
5e)
44
94
58
90
82
11f)
120
46
91
97
80
47
Ph
Ph
*
Me
i-Pr
Ph
Ph
9k
9e
O
O
O
O
O
*
O
*
6g)
168
12f)
BnO
t-Bu
Me
OBn
9f
9l
a) Reaction conditions: The reaction was carried out in 1.5 mL of CHCl3 with 0.25 mmol of substrate under 1.0 MPa CO2 pressure.
b) Isolated yield. c) Enantiomeric excess was determined by HPLC analysis using chiral column (Daicel Chiralcel OD-H or Chiralpak
IB). d) Using 3 mol % of silver acetate and 1 mol % 10b at 0 °C. e) Using 3 mol % of silver acetate and 1 mol % 10b at 5 °C. f) Using
5 mol % of silver acetate and 2 mol % 10b at 5 °C. g) Using 7.5 mol % of silver acetate and 3 mol % 10b at 5 °C. h) Using 12 mol % of
silver acetate and 5 mol % 10b in 2.5 mL of CHCl3 at 5 °C.
General Procedure for Aminolysis of Optically Active
Cyclic Carbonate 9a. To a solution of the cyclic carbonate 9a
(0.125 mmol) in THF (0.5 mL) was slowly added a THF
(0.5 mL) solution of an amine at 5 °C. After the carbonate 9a
was completely consumed, the mixture was evaporated to
remove THF. Purification by silica gel column chromatography
gave the corresponding carbamate 11.
3H), 3.24-3.39 (m, 4H), 4.21 (d, 2H, J = 17.6 Hz), 7.20-7.38
(m, 8H), 7.44-7.50 (m, 2H). 13C NMR (CDCl3, 100 MHz):
¤ 13.5, 14.1, 25.2, 41.7, 42.0, 44.4, 76.9, 87.1, 87.2, 122.0,
126.7, 128.3, 128.4, 128.8, 129.8, 131.8, 134.2, 154.1, 201.9.
IR (KBr): 2973, 2936, 1701, 1474, 1430, 1381, 1277, 1169,
975, 757, 719, 696. HRMS(ESI): Calcd for C23H26NO3:
[M + H]+: 364.1913. Found: m/z 364.1912. HPLC: Daicel
chiralcel OZ-H (0.3% EtOH in hexane; flow rate = 1.0
3-Methyl-4-oxo-1,5-diphenylpent-1-yn-3-yl Diethylcarba-
31
mate (11a):
¤ 1.15 (t, 3H, J = 8.0 Hz), 1.20 (t, 3H, J = 8.0 Hz), 1.73 (s,
Colorless oil; 1H NMR (CDCl3, 400 MHz):
mL min¹1), 10.7 min (major), 15.0 min (minor). ½¡ꢀD +81.5°
(c = 0.22 in CHCl3).

S. Kikuchi et al.
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011)
715
Table 16. Aminolyis Reaction of Optically Cyclic
Carbonate 9a
76.8, 86.7, 87.3, 121.9, 126.8, 128.27, 128.3, 128.9, 129.8,
131.8, 134.1, 152.8, 201.7. IR (KBr): 3368, 2984, 1701, 1517,
1506, 1460, 1260, 1205, 1088, 762, 756, 720, 706, 691.
HRMS(ESI): Calcd for C23H26NO3: [M + H]+: 364.1913.
Found: m/z 364.1930. HPLC: Daicel chiralpak IA (0.5%
EtOH in hexane; flow rate = 1.0 mL min¹1), 9.0 min (minor),
O
Ph
Ph
O
O
Amine
O
Ph
Nu
O
*
THF, 5 °C
*
O
29
Ph
10.3 (major). ½¡ꢀD +96.2° (c = 0.20 in CHCl3).
9a
11
3-Methyl-4-oxo-1,5-diphenylpent-1-yn-3-yl Isopropylcar-
1
Ee/%c)
9a 11
93 93
bamate (11e): Colorless oil; H NMR (CDCl3, 400 MHz): ¤
Entrya)
Amine
Equiv Time/h 11 Yield/%b)
1.16-1.17 (m, 6H), 1.72 (s, 3H), 3.77-3.85 (m, 1H), 4.19 (d,
1H, J = 16 Hz), 4.23 (d, 1H, J = 16 Hz), 4.78 (d, 1H, J =
7.6 Hz), 7.21-7.38 (m, 8H), 7.44-7.49 (m, 2H). 13C NMR
(CDCl3, 100 MHz): ¤ 22.9, 25.1, 86.7, 87.3, 121.8, 126.8,
128.27, 128.3, 128.9, 129.8, 131.8, 134.0, 153.7, 201.8. IR
(KBr): 3390, 3057, 2989, 2235, 1958, 1887, 1712, 1598, 1489,
1443, 1258, 1092, 1015. HRMS(ESI): Calcd for C22H24NO3:
[M + H]+: 350.1756. Found: m/z 350.1758. HPLC: Daicel
chiralpak IA (2.0% THF in hexane; flow rate = 1.0 mL min¹1),
Et2NH
NH
1
2
2.0
1.5
24
3
11a
11b
99
98
89 89
94 94
3
4
5
1.5
3.0
1.5
4
72
5
11c
11d
11e
>99
95
O
NH
94 94
93 93
NH2
NH2
30
14.0 min (minor), 19.7 min (major). ½¡ꢀD +92.3° (c = 0.22 in
>99
CHCl3).
3-Methyl-4-oxo-1,5-diphenylpent-1-yn-3-yl Propylcarba-
mate (11f): Colorless oil; 1H NMR (CDCl3, 400 MHz): ¤ 0.93
(t, 3H, J = 7.6 Hz), 1.52-1.57 (m, 2H), 1.72 (s, 3H), 3.13-3.20
(m, 2H), 4.21 (s, 2H), 4.88 (s, 1H), 7.12-7.38 (m, 8H), 7.45-
7.50 (m, 2H). 13C NMR (CDCl3, 100 MHz): ¤ 11.1, 23.1, 25.1,
42.8, 44.3, 76.9, 86.7, 87.4, 121.8, 126.8, 128.28, 128.35,
128.9, 129.8, 131.9, 134.0, 154.5, 201.9. IR (KBr): 3374, 3032,
2966, 2877, 1733, 1541, 1520, 1454, 1252, 1132, 764, 719,
689. HRMS(ESI): Calcd for C22H24NO3: [M + H]+: 350.1756.
Found: m/z 350.1758. HPLC: Daicel chiralpak IA (2% THF in
hexane; flow rate = 1.0 mL min¹1), 7.4 min (minor), 11.5 min
NH2
NH2
6
7
1.2
1.5
5.5 11f
11g
>99
89 89
94 94
3
96
a) Reaction conditions: The reaction was carried out in 1.0 mL
of THF with 0.125 mmol of substrate. b) Isolated yield.
c) Enantiomeric excess was determined by HPLC analysis
using Daicel Chiralcel OD-H for 9a, Daicel Chiralcel OZ-H
for 11a-11c, and Daicel Chiralpak IA for 11d-11g.
3-Methyl-4-oxo-1,5-diphenylpent-1-yn-3-yl Pyrrolidine-
1-carboxylate (11b):
Colorless oil; 1H NMR (CDCl3,
30
400 MHz): ¤ 1.73 (s, 3H), 1.82-1.95 (m, 4H), 3.39-3.47 (m,
4H), 4.23 (d, 1H, J = 16.8 Hz), 4.26 (d, 1H, J = 16.8 Hz),
7.21-7.37 (m, 8H), 7.50-7.53 (m, 2H). 13C NMR (CDCl3,
100 MHz): ¤ 24.9, 25.4, 25.7, 44.6, 46.1, 76.6, 87.1, 87.3,
122.0, 126.7, 128.3, 128.8, 129.8, 131.88, 131.92, 134.1,
153.1, 202.2. IR (KBr): 3033, 2982, 2872, 1701, 1498, 1417,
1277, 1229, 1073, 1063, 1037, 754, 719, 699. HRMS(ESI):
Calcd for C23H24NO3: [M + H]+: 362.1756. Found: m/z
362.1753. HPLC: Daicel chiralcel OZ-H (2% EtOH in hexane;
flow rate = 1.0 mL min¹1), 13.5 min (major), 19.9 min (minor).
(major); ½¡ꢀD +98.2° (c = 0.20 in CHCl3).
3-Methyl-4-oxo-1,5-diphenylpent-1-yn-3-yl Allylcarba-
1
mate (11g): Pale yellow oil; H NMR (CDCl3, 400 MHz): ¤
1.73 (s, 3H), 3.83 (s, 2H), 4.22 (s, 2H), 4.96 (s, 1H), 5.15 (d,
1H, J = 10.8 Hz), 5.23 (d, 1H, J = 17.2 Hz), 5.81-5.90 (m,
1H), 7.24-7.38 (m, 8H), 7.45-7.51 (m, 2H). 13C NMR (CDCl3,
100 MHz): ¤ 25.1, 43.4, 44.3, 86.5, 87.5, 116.3, 121.7, 126.8,
128.3, 128.4, 128.9, 129.8, 131.8, 133.9, 154.4, 201.8. IR
(KBr): 3364, 3064, 3029, 2930, 1716, 1646, 1602, 1543, 1508,
1455, 1244, 1091, 1063, 1030, 992, 915, 763, 718, 690.
HRMS(ESI): Calcd for C22H22NO3: [M + H]+: 348.1600.
Found: m/z 348.1601; HPLC Daicel chiralpak IA (10% THF
in hexane; flow rate = 1.0 mL min¹1), 16.4 min (minor),
28
½¡ꢀD +75.0° (c = 0.21 in CHCl3).
3-Methyl-4-oxo-1,5-diphenylpent-1-yn-3-yl Morpholine-
4-carboxylate (11c):
Colorless oil; 1H NMR (CDCl3,
29
400 MHz): ¤ 1.73 (s, 3H), 3.48 (s, 2H), 3.55 (s, 2H), 3.69 (t,
4H, J = 4.4 Hz), 4.23 (d, 2H, J = 16.4 Hz), 7.23-7.39 (m, 8H),
7.46-7.53 (m, 2H). 13C NMR (CDCl3, 100 MHz): ¤ 25.3, 44.6,
66.5, 77.1, 86.8, 87.5, 121.8, 126.9, 128.3, 128.4, 129.0, 129.8,
131.9, 133.8, 153.5, 201.8. IR (KBr): 2920, 1735, 1541, 1417,
1225, 1084, 1026, 765, 729, 696. HRMS(ESI): Calcd for
C23H24NO4: [M + H]+: 378.1705. Found: m/z 378.1710.
HPLC: Daicel chiralcel OZ-H (2.0% EtOH in hexane; flow
rate = 1.0 mL min¹1), 17.9 min (major), 25.8 min (minor).
41.4 min (major). ½¡ꢀD +79.8° (c = 0.19 in CHCl3).
Computational Methods. The Gaussian 03 program was
used for the full geometry optimizations with the B3LYP/
6-31+G*// B3LYP/6-31+G* method and basis set (The
3-21G* basis set was substituted for 6-31+G* in the case
of the Ag atom.). 5d functions were used for the d orbital.
Calculations were performed without assuming symmetry.
Frequency calculations were performed for all of the obtained
structures at the same level. It was confirmed that all the
frequencies were real for the ground states and one imaginary
frequency existed for the transition state (TS). Vectors of the
imaginary frequencies directed the reaction mode, and intrinsic
reaction coordinate calculations were further performed to
confirm that the obtained TSs were on the saddle points of the
energy surface between the reactant and the product. The
30
½¡ꢀD +54.3° (c = 0.24 in CHCl3).
3-Methyl-4-oxo-1,5-diphenylpent-1-yn-3-yl tert-Butylcar-
1
bamate (11d): Colorless oil; H NMR (CDCl3, 400 MHz): ¤
1.34 (s, 9H), 1.71 (s, 3H), 4.14 (d, 1H, J = 16.8 Hz), 4.20 (d,
1H, J = 16.8 Hz), 4.89 (s, 1H), 7.22-7.37 (m, 8H), 7.42-7.48
(m, 2H). 13C NMR (CDCl3, 100 MHz): ¤ 24.8, 28.8, 43.9, 50.8,

716
Bull. Chem. Soc. Jpn. Vol. 84, No. 7 (2011) BCSJ AWARD ARTICLE
d) A. Correa, R. Martín, Angew. Chem., Int. Ed. 2009, 48, 6201.
e) C. Bruckmeier, M. W. Lehenmeier, R. Reichardt, S. Vagin, B.
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single-point energy including the SCRF/PCM approach was
calculated using the Gaussian 09 program.
We thank Prof. Naoki Yoshioka, Keio University, and
Dr. Keiko Orisaku, Kanagawa University, for the X-ray
analysis of the 2k, 4a, and 9a-cobalt complexes. We also
thank Prof. Hiroshi Izumi, National Institute of Advanced
Industrial Science and Technology, for a great discussion
and advice regarding the VCD analysis. We thank the
Information Technology Center at the University of Electro-
Communications for the computations in the theoretical
calculations. We are very thankful to JASCO Co. for the
VCD spectra measurement. This work was supported by
a Grant-in-Aid for Science Research on Priority Areas
“Advanced Molecular Transformations of Carbon Resources”
from the Ministry of Education, Culture, Sports, Science and
Technology, Japan.
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Supporting Information
X-ray analysis of 2k, 4a, and 9a-cobalt complex. NMR and
HPLC data of the compounds 11a-11g. This material is
available free of charge on the web at http://www.csj.jp/
journals/bcsj/.
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