Chiral catalysts for the asymmetric cycloaddition of carbon dioxide with epoxides

Article abstract of DOI:10.1016/j.tetasy.2008.08.001

Several chiral BINADCo(III)X (BINAD = Bis(1,1′-2-hydroxy-2′-alkoxy-3-naphthylidene)-1,2-cyclohexanediamine, X = OAc, CF₃CO₂, CCl₃CO₂, OTs, p-NO₂PhCO₂) complexes were synthesized and used to

Full text of DOI:10.1016/j.tetasy.2008.08.001

Tetrahedron: Asymmetry 19 (2008) 1947–1953
Contents lists available at ScienceDirect
Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Chiral catalysts for the asymmetric cycloaddition of carbon dioxide
with epoxides
*
Lili Jin, Yongzhong Huang, Huanwang Jing , Tao Chang, Peng Yan
State Key Laboratory of Applied Organic Chemistry, Lanzhou University, Lanzhou 730000, PR China
a r t i c l e i n f o
a b s t r a c t
0
0
Article history:
Several chiral BINADCo(III)X (BINAD = Bis(1,1 -2-hydroxy-2 -alkoxy-3-naphthylidene)-1,2-cyclohexane-
diamine, X = OAc, CF CO , CCl CO , OTs, p-NO PhCO ) complexes were synthesized and used to catalyze
Received 27 June 2008
Accepted 1 August 2008
Available online 29 August 2008
3
2
3
2
2
2
the asymmetric cycloaddition of carbon dioxide with epoxides under mild condition to afford chiral cyclic
carbonates. The best catalyst of (S,S,S,S)-BINADCo(III)(OAc) 9b and phenyltrimethylammonium tribro-
mide (PTAT) can provide propylene carbonate with the highest ee being 95% at ꢀ20 °C.
Ó 2008 Elsevier Ltd. All rights reserved.
1
. Introduction
Transformation of carbon dioxide into useful organic com-
2. Results and discussion
Some multi-chiral free ligands of BINAD (Fig. 1, compounds 1
and 3) have already been reported for asymmetric catalytic reac-
pounds has attracted much interest during the last two decades
due to the economic and environmental benefits arising from the
utilization of renewable sources and the growing concern on the
greenhouse effect.
cycloaddition of CO
for CO fixation.
2
organic synthetic intermediates, monomers, aprotic polar solvents,
pharmaceutical/fine chemical intermediates, and in the biomedical
2
9–32
tions.
These multi-chiral free ligands can be good chiral li-
. As
gands for the asymmetric cycloaddition of epoxides and CO
2
1
–4
The preparation of cyclic carbonates via
with epoxides is one of the methodologies
The cyclic carbonates are widely used as
a result, we decided to synthesize these novel multi-chiral ligands
1-11 (Fig. 1). The ligands were easy to convert to the multi-chiral
complexes of BINADCo(II) 1a–11a (Fig. 2) which were oxidized to
BINADCo(III)OAc 1b–11b using glacial acetic acid. The (R,R,R,R)-
BINADCo(III)OAc complexes 1b–5b were first obtained by tuning
2
5
–11
1
2–21
0
applications.
The enantiomerically pure cyclic carbonates
of the 2 -substituted group of BINOL in catalyst 1b supplying vari-
have rarely been reported except for the insertion of carbon diox-
ide into enantiomerically pure chiral epoxides or the coupling reac-
tion of carbon dioxide with racemic epoxides catalyzed by chiral
ous steric effect. These catalysts might combine the two kinds of
chirality of salen-backbone and of BINOL-frame and affect their
enantioselectivity in the asymmetric cycloaddition reaction. The
investigation results using these new catalysts with phenyltri-
methylammonium tribromide as co-catalyst are summarized in
Table 1. It was found that catalyst 1b with the smallest 2 -hydroxy
group had lower enantioselectivity (entry 1) than other analogues
and has lower Krel values for the kinetic resolution reaction of PO
and CO . For the catalysts 2b–5b, the more bulky substituted group
2
2
2–26
salenCo(III) catalysts.
The kinetic resolution of racemic epox-
ides with water is known as an efficient method for obtaining
2
7,28
0
enantiopure epoxide,
ides with CO using a chiral salenCo(III) complex as catalyst and
a co-catalyst of quaternary onium salt cannot lead to the enantio-
the kinetic resolution of racemic epox-
2
pure epoxide and cyclic carbonate.2
ogies for the asymmetric cycloaddition of CO
2–26
Therefore, new methodol-
with epoxides are
2
gave better ee values and higher Krel values (entries 4–7). Catalyst
0
still well desired in terms of their atom economic characteristic.
Herein, we report our recent efforts for the synthesis of optically
active cyclic carbonates with the enantiomeric excess ranging from
moderate to excellent catalyzed by the novel multi-chiral catalysts
of BINADCo(III)X.
4b with a 2 -benzyloxy group had more activity than the other ana-
logues yielding (S)-propylene carbonate within 77 TOF. Modified
catalysts 1b-Cs and 1b-Mg have more steric effect thus giving
higher relative rate constants Krel values (entries 2 and 3) than
their precursors 1b. On the other hand, when the chirality of
0
1
,1 -2-binaphthol and 1,2-cyclohexanediamine were mixed to pre-
pare the catalysts of (S,R,R,S)-BINADCo(III)OAc 6b and (R,S,S,R)-
BINADCo(III)OAc 7b, their activity and enantioselectivity decreased
(
entries 8 and 9 vs entries 1 and 7). As predicted, when the config-
0
uration of both 1,1 -2-binaphthol and 1,2-cyclohexanediamine
was switched from (R) to (S) in order to prepare the catalysts of
(S,S,S,S)-BINADCo(III)OAc 8b, 9b, the chirality of the product was
*
Corresponding author. Tel.: +86 931 392 7959; fax: +86 931 891 2582.
E-mail address: hwjing@lzu.edu.cn (H. Jing).
0
957-4166/$ - see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2008.08.001

1
948
L. Jin et al. / Tetrahedron: Asymmetry 19 (2008) 1947–1953
(R)
(R)
(R)
(R)
N
N
N
N
OH
HO
OH
OH
HO
HO
(
R)
(R)
(R)
(R)
R
R
N
N
(R,R,R,R)
(
R)
(R)
1
2
3
4
5
R=OH
R=OBu
R=OCH3
R=OCH Ph
R=Ph
6
7
8
9
(S,R,R,S) R=OH
(R,S,S,R) R=Ph
(S,S,S,S) R=OH
(S,S,S,S) R=OBu
1
1
0-(R,R,R,R,R,R)
1-(S,R,R,S,R,R)
2
Figure 1. BINAD compounds.
(R)
(R)
(R)
(R)
N
N
N
N
Co
X
Co
X
O
O
O
O
O
O
(
R)
(R)
(R)
(R)
R
R
X
Co
N
N
(
R,R,R,R)
(
R)
(R)
X = none, 1a ~ 11a
X = OAc, 1b ~ 11b
1
1
1
2
3
4
b
R=OH
b-Cs R=OCs
b-Mg R=O1/2Mg 6b (S,R,R,S) R=OH
5
b (R,R,R,R) R=Ph
1
0b-(R,R,R,R,R,R)
b
b
b
R=OBu
7b (R,S,S,R) R=Ph
1
1b-(S,R,R,S,R,R)
8
9
b
b
(S,S,S,S) R=OH
(S,S,S,S) R=OBu
R=OCH3
R=OCH Ph
2
Figure 2. BINADCo(III) complexes.
Table 1
BINADCo (III) complexes in asymmetric cycloaddition of CO
2
and POa
O
O
(
R)-catalyst
(S)-catalyst
O
O
O
O
O
O
O
+
CO2
co-catalyst
co-catalyst
(R)
(S)
(R)
(S)
PCb (ee%/yield)
t (h)
TOFc (hꢀ1
)
K
d
Entry
Catalyst
Conv (%)
rel
1
2
3
4
5
1b
39
24
27
25
36
46
33
41
30
43
34
33 (S)/38.5
45 (S)/23.5
55 (S)/27
24
12
24
20
20
12
17
48
98
42
24
32
40
22
23
36
77
38
17
6
2
3
4
4
5
4
4
2
2
5
3
1b-Cs
1b-Mg
2b
3b
4b
5b
6b
7b
10b
11b
60 (S)/24.8
55 (S)/35.6
44 (S)/45.8
49 (S)/32.6
24 (S)/40.7
30 (R)/29.5
54 (S)/42.8
45 (S)/33.7
e
6
7
8
9
1
1
0
1
36
29
a
Reaction condition: catalyst (0.05 mmol), PTAT (0.1 mmol), PO (100 mmol, 7 mL), temperature: 25 °C, CO
ee value was determined by Varian CP-3800 GC on a Supelco-DEX series (225) chiral column.
TOF: Turnover frequence, moles of product/per mole catalyst per hour.
2
: 0.5 MPa.
b
c
d
e
K
rel = ln[1 ꢀ c(1 + ee)]/ln[1 ꢀ c(1 ꢀ ee)], where c is the conversion and ee is the enantiomeric excess of the resulting propylene carbonate.
The 36.8% ee of remaining PO was determined by converting to related PC using unchiral catalyst.

L. Jin et al. / Tetrahedron: Asymmetry 19 (2008) 1947–1953
1949
also switched from (S)-PC to (R)-PC (Table 2, entries 5 and 6). These
Table 4
The anoin effect of catalyst on asymmetric cycloaddition of CO
2
and POa
results reveal that the chirality of PC is affiliated with chirality of
salen-backbone and of BINOL-frame: the same chiralities of
binaphthol and diamine are consistent to enhance the enantio-
selectivity, whereas the contrary chiralities of them are inconsis-
tent to decrease the ee value of PC.
Entry
BINADCo(III)X
Conv (%)
PC (ee%/yield)
t (h)
Krel
ꢀ
1
2
3
4
5
2b ðX ¼ CH
3
CO
Þ
20
30
20
26
27
87 (S)/20.2
65 (S)/29.6
53 (S)/20.1
43 (S)/25.9
83 (S)/26.8
72
70
90
18
6
4
3
15
2
ꢀ
2c ðX ¼ CF CO
3
Þ
2
ꢀ
2d ðX ¼ CCl
3
ꢀ
CO
Þ
2
2e (X = TsO )
2f ðX ¼ p-NO
55
Furthermore, the effect of temperature was also investigated
ꢀ
2
PhCO2
Þ
150
(Table 2). When the reaction temperature decreased from room
a
temperature to 0 °C, the Krel value was augmented from 4 to 18
along with the ee value of (S)-PC improved obviously to 87% (Table
Reaction condition: catalyst (0.05 mmol), PTAT (0.1 mmol), PO (100 mmol,
: 0.5 MPa, 0 °C.
7
mL), CO
2
2, entry 1) using (R,R,R,R)-BINADCo(III)OAc 2b as catalyst and PTAT
as co-catalyst; otherwise, the Krel value was augmented to 21 along
with the ee value of (R)-PC which increased to 90% (Table 2, entry 7
at 0 °C) using (S,S,S,S)-BINADCo(III)OAc (9b) as catalyst and PTAT as
co-catalyst. When the reaction temperature was cooled down to
Table 5
Asymmetric cycloaddition of CO
2
with various epoxidesa
O
ꢀ
20 °C, the enantiomeric excess and the relative rate constant Krel
(S)-catalyst
values of (R)-PC approached to 95% and 41, respectively (Table 2,
entry 8). These results demonstrated that catalysts 2b and 9b have
excellent catalytic abilities and enantioselectivities with regard to
the synthesis of chiral PC.
O
O
O
O
+
CO2
co-catalyst
R
R
R
Entry
R=
CH
ClCH
Conv (%)
CC (ee%/yield)
t (h)
K
rel
1b
2
33
15
10
5
89 (R)/33.2
68 (S)/14.8
10 (R)/9.7
6 (R)/4.6
120
72
26
6
Table 2
3
The effect of temperature on asymmetric cycloaddition of CO
2
and POa
2
c
3
PhOCH
Ph
2
48
1
Entry
Catalyst
T (°C)
Conv (%)
PC (ee%/yield)
t (h)
K
rel
c
4
48
1
5
Et
5
86 (R)/4.8
120
14
1
2
3
4
5
6
7
8
2b
6b
3b
4b
8b
9b
9b
9b
0
0
0
20
20
20
11
28
13
10
5
87 (S)/20
41 (S)/20.1
71 (S)/20
64 (S)/11.1
50 (R)/27.7
81 (R)/12.9
90 (R)/10
95 (R)/4.9
72
48
96
120
17
20
18
3
7
5
4
11
21
41
a
Reaction condition: catalyst 9b (0.05 mmol), PTAT (0.1 mmol), epoxide
: 0.5 MPa, 0 °C.
The 42.4% ee of remaining PO was determined.
(
100 mmol, 7 mL), CO
2
0
b
10
10
0
ꢀ20
c
The ee value was determined by HPLC (Daicel Chiralcel OD, n-hexane/2-pro-
panol (9:1 v/v), 1.0 mL/min, 254 nm).
54
100
a
Reaction condition: catalyst (0.05 mmol), PTAT (0.1 mmol), PO (100 mmol,
: 0.5 MPa.
different substituted groups can be transferred to the correspond-
ing optically active cyclic carbonates (CC) with considerable to
good ee value. It is worth noting that when the conversion was
augmented from 10% (Table 2, entry 7) to 33% (Table 5, entry 1),
the ee and Krel values sustained the same level.
7
mL), CO
2
Meanwhile, the co-catalysts of quaternary ammonium haloge-
nide were screened in order to enhance the activity and enantio-
selectivity of catalyst for asymmetric cycloaddition of CO with
2
propylene oxide (PO). The results are listed in Table 3. It can be
seen that the PTAT and TBAB were the good co-catalysts (entries
3
. Conclusion
1
and 4), while the TBAC showed less activity (entry 5) and TBAF
In conclusion, we have demonstrated that a series of multi-
showed no activity (entry 6) under the reaction conditions.
chiral BINADCo(III)X complexes in the presence of PTAT or TBAB
are highly efficient catalysts for the coupling of epoxides and car-
bon dioxide affording chiral cyclic carbonates in moderate yield
with high enantioselectivities under very mild condition. Compar-
Table 3
and POa
2
The effect of co-catalyst on asymmetric cycloaddition of CO
Entry Catalyst Co-catalyst T (°C) Conv. (%) PC (ee%/yield) t (h)
K
rel
ing with the results using chiral Schiff base catalyst contained only
1
2
3
4
5
6
9b
2b
2b
2b
2b
2b
Bu
PTAT
Bu
Bu
Bu
Bu
4
NBr
0
0
10
0
10
10
17
20
25
14
3
84 (R)/16.8
87 (S)/19.7
63 (S)/24.6
78 (S)/13.9
80 (S)/3
24 14
72 18
22–24
one chiral center,
our investigation results with regard to the
ee value of cyclic carbonates achieved much progress. The chirali-
ties of BINOL-frame and backbone of Schiff base might have some
synergic effects: the same absolute configuration of it has a posi-
tive effect giving a higher ee value of propylene carbonate; on
the other hand, the opposite absolute configuration of it had a neg-
ative effect giving a lower ee value of propylene carbonate that
4
NBr
4
NBr
4
NCl
4
NF
20
36
5
9
196
9
—
—
5 days
—
a
Reaction condition: catalyst (0.05 mmol), co-catalyst (0.1 mmol), PO (100
mmol, 7 mL), CO : 0.5 MPa.
2
3
3,34
phenomena are consistent with literature reports.
The substi-
tuted groups on the frame of these catalysts play very important
roles. Therefore, decorating of these new catalysts will be a further
improvement.
To screen for the best catalyst system, the various acids were
used in the oxidation of BINADCo(II) leading to catalyst
ꢀ
ꢀ
ꢀ
ꢀ
BINADCoðIIIÞXðX ¼ CH
3
CO 2b, CF
3
CO 2c, CCl
3
CO 2d, TsO 2e,
2
2
2
ꢀ
and p ꢀ NO
2
PhCO 2f). The catalytic properties of these catalysts
2
were then investigated at 0 °C. The results (Table 4) show that cat-
alyst 2b with OAc as the counterion has better enantioselectivity
4. Experimental
(
entry 1, 87% ee) than the other analogues, and that catalyst 2c
Epoxides were purchased from Aldrich and Alfa Aesar company
and distilled from CaH , (S)-1,1 -bi-2-naphthol and (R)-1,1 -bi-2-
2
ꢀ
0
0
with CF
3
CO as counterion has better activity than others (entry 2).
2
With the optimized conditions, we examined this asymmetric
cycloaddition reaction of other epoxides with carbon dioxide using
naphthol were purchased from Lianyungang Chiral Chemicals Co.
Ltd (China) and used without further purification. (1R,2R)-(ꢀ)-
0
0
9
b as catalyst (Table 5). We found that, using 0.05% catalyst, 0.1%
N,N -Bis((R)-2,2 -dihydroxy-3-naphthylidene)-1,2-cyclohexanedia-
0
0
PTAT as catalyst, various mono-substituted terminal epoxides with
mine 1, (1R,2R)-(ꢀ)-N,N -bis((S)-2,2 -dihydroxy-3-naphthyli-dene)-

1
950
L. Jin et al. / Tetrahedron: Asymmetry 19 (2008) 1947–1953
0
0
1
3
,2-cyclohexanediamine 6, (1S,2S)-(ꢀ)-N,N -bis((S)-2,2 -dihydroxy-
(20 mL) were added. The mixture was stirred and heated to reflux
for 3.5 h. Then, the bromide was added in one portion from a pres-
sure-funnel and the reaction mixture was continued for 3 h under
reflux conditions. After evaporating the acetone using a rotary
evaporator, the residue was treated with a flash chromatograph
using the petroleum ether and ethyl acetate as eluent (10:1, v/v).
The colorless liquid was obtained with the yield from 30% to 66%
(For OR = Ph, this procedure was alternated to treat BINOL firstly
with the triflic anhydride and then following a standard Grignard
-naphthylidene)-1,2-cyclohexanediamine 8, and (1R,2R)-(ꢀ)-
0
0
0
N,N -bis((R)-1,1 -2-hydroxy-2 -methoxy-3-naphthyli-dene)-1,2-
cyclohexanediamine 3 were prepared according to the literature
3
5–38
1
13
methods.
Varian 300 and Varian 400 spectrometers, with TMS as internal ref-
erence (d = 7.26 ppm for CDCl , d = 77 ppm for CDCl ). Chemical
shifts (d) are given in parts per million (ppm) and coupling constants
J) are given in Hertz (Hz). HRESIMS were carried out on a Bruker
H NMR and C NMR spectra were recorded on
H
3
C
3
(
APEX II mass spectrometer with glycerol as the matrix. Elemental
analyses were carried out on Carioel elemental analyzer. The enan-
tiomeric excesses of the resulting cyclic carbonate without fluores-
cence were determined by chiral GC analysis (Supelco-DEX series
reaction using Ni(DPPE)Cl
2
as catalyst).
4.1.1.2. General procedure for synthesis of 2-methoxymethyl-
0
0
2 -alkoxy-1,1 -binaphthyl.
To a 250 mL three-necked flask
(
225) chiral column; injection temperature = 250 °C; detection tem-
equipped with a pressure-funnel, a rubber-stopper and a magnetic
stir bar, 2 -alkoxy-BINOL (10 mmol), THF/DMF (60 mL, 2:1v/v) and
0
perature = 250 °C; 180 °C isothermal.) using a Varian CP-3800 gas
chromatograph or Shimadzu GC-9AM equipped with a flame-ioni-
NaH (0.46 g, 60%) were added. When the mixture was cooled down
0
0
zation detector (FID), and N
2
as a carry gas. The enantiomeric ex-
to 0 °C,
a
solution of 2-hydroxy-2 -alkoxy-1,1 -binaphthyl
cesses of the resulting cyclic carbonate with fluorescence were
determined by chiral HPLC analysis (Daicel Chiralcel OD chiral
column, n-hexane/2-propanol (9:1 v/v), 1.0 mL/min, 254 nm) using
a Water 600 controller with 2996 pholodiode Array detector.
(10 mmol) in 12 mL THF was added dropwise. After 1 h additional
stirring, 1.2 mL methoxymethyl chloride (MOMCl) was added by a
syringe. The reaction was then continued for another 4 h at room
temperature and then quenched with 100 mL water. This mixture
was extracted three times with 50 mL ethyl acetate. The combined
organic phase was washed with water and brine, and dried over
4
.1. General procedure for the preparation of new BINAD
ligands
4
MgSO . After removing the organic solvent using a rotary evapora-
tor, the residue was treated with a flash chromatography using the
petroleum ether and ethyl acetate as eluent (10:1, v/v). The color-
less liquid was obtained in 50–60% yield.
The chiral 1,2-cyclohexanediammonium mono-
0.5 mmol) and K CO (1 mmol) were dissolved in 1.2 mL 50% eth-
anol. The obtained solution was then added dropwise to a solution
of 3-formyl-2-hydroxy-2 -substituted-1,1 -binaphthyl (1 mmol) in
ethanol (5 mL) and stirred at room temperature for 24 h. The pre-
cipitate was collected by filtration, washed with cold ethanol, and
dried in vacuum oven to obtain the product with high yield (85–
L-tartrate
(
2
3
0
0
4.1.1.3. General procedure for synthesis of 3-formyl-2-
0
0
methoxymethyl-2 -alkoxy-1,1 -binaphthyl.
To a solution of
0
0
2-methoxymethyl-2 -alkoxy-1,1 -binaphthyl and TMEDA (18 mL)
in THF (400 mL), 1 M BuLi (140 mL in ethyl ether) was added with-
in 15 min at ꢀ78 °C under argon. The mixture was warmed up to
9
0%). The configurations of the ligands are shown in Figure 1.
0
°C and stirred for 30 min and then cooled down to ꢀ78 °C. A solu-
0
0
4
.1.1. Syntheses of 3-formyl-2-hydroxy-2 -substituted-1,1 -
tion of DMF (9 mL) in THF (50 mL) was added dropwise. This reac-
tion was carried out at ꢀ78 °C for 30 min and then at 0 °C for
40 min. The obtained yellow solution was quenched with 50 mL
binaphthyl
0
The synthetic route to fabricate 3-formyl-2-hydroxy-2 -alkoxy-
0
1
,1 -binaphthyl was depicted in Scheme 1.
4
saturated NH Cl solution and then with 50 mL 1 M HCl solution.
After separating the organic layer, the water layer was extracted
with ethyl ether. The combined organic layer was washed with sat-
urated NaHCO and brine, and dried over MgSO . After removing
3 4
the organic solvent using a rotary evaporator, the residue was trea-
ted with a flash chromatography using the petroleum ether and
ethyl acetate as eluent (10:1, v/v). The product was obtained in
K CO reflux
2
3
OH
OH
OH
OR
+
RBr
acetone
6
0–76% yield.
4
.1.1.4. General procedure for the synthesis of 3-formyl-2-
0
0
hydroxy-2 -alkoxy-1,1 -binaphthyl.
To a solution of 3-formyl-
MOMCl, NaH
BuLi, TMEDA
OMOM
OR
0
0
2-methoxymethyl-2 -alkoxy-1,1 -binaphthyl (10 mmol) in 10 mL
o
o
DMF, -78 C
THF, 50 mL concentrated HCl was added dropwise at 0 °C. This mix-
ture was then stirred 3 h at room temperature and then extracted
with ethyl acetate. The obtained solution was washed with water,
THF/DMF, 0 C
3 2 4
saturated NaHCO and brine, and dried with Na SO . After evaporat-
CHO
CHO
ing the solvent, the product was obtained with nearly quantitative
1
yield and characterized by H NMR and MS that was consistent with
OMOM Conc. HCl
OR
OH
OR
literature.
0 o
C
0
0
0
4
.1.2. (1R,2R)-(ꢀ)-N,N -Bis((R)-1,1 -2-hydroxy-2 -butoxy-3-
naphthylidene)-1,2-cyclohexanediamine 2
2
D
0
1
0
0
Pale yellow solid. 85% yield, ½
300 MHz, CDCl ): d 0.70 (t, J = 7.5 Hz, 6H), 1.00–1.07 (m, 4H),
.42–1.56 (m, 8H), 1.69–1.95 (m, 4H), 3.30 (d, J = 9.6 Hz, 2H),
aꢁ
¼ ꢀ88 (c 1.0, CH
2 2
Cl ); H NMR
Scheme 1. Synthetic route to 3-formyl-2-hydroxy-2 -alkoxy-1,1 -binaphthyl.
(
1
3
4
2
.1.1.1. General procedure for the synthesis of 2-hydroxy-
3.97–4.05 (m, 4H), 7.02–7.13 (m, 6H), 7.18–7.47 (m, 6H), 7.72
0
0
-alkoxy-1,1 -binaphthyl.
To a 50 mL three-necked flask
(dd, J = 6.3 Hz, J = 8.4 Hz, 4H), 7.89–7.96 (m, 6H), 8.45 (s, 2H),
1
3
equipped with a argon gas protector, a pressure-funnel and a mag-
netic stir bar, BINOL (2.86 g, 10 mmol), K CO (4 g) and acetone
13.1 (s, 2H); C NMR (75 MHz, CDCl
3
): d 13.5, 18.6, 24.0, 31.2,
2
3
32.7, 69.5, 72.8, 116.0, 117.2, 119.8, 120.3, 122.9, 123.5, 123.6,

L. Jin et al. / Tetrahedron: Asymmetry 19 (2008) 1947–1953
1951
0
0
1
1
24.8, 125.1, 126.3, 127.2, 127.9, 128.0, 128.6, 129.4, 133.0, 133.8,
35.3, 154.3, 154.6, 165.1; HRMS (ESI): calcd for [M+H]
4.1.7. Bis((1R,2R)-(ꢀ)-N,N -(R)-1,1 -bi-2-hydroxy-3-naphthyli-
+
dene)-1,2-cyclohexanediamine 10
(
C
56
H
55
N
2
O
4
) requires m/z = 819.4162, found: 819.4153; Anal.
Calcd for C56 : C, 81.90; H, 6.51; N, 3.14. Found: C, 82.12;
H, 6.65; N, 3.42.
(1R,2R)-(ꢀ)-Cyclohexanediammonium mono-
L-tartrate (1 mmol)
H
54
N
2
O
4
and K CO (2 mmol) were dissolved in 2.4 mL 50% ethanol and
2
3
0
0
then added dropwise to a solution of (R)-(+)-3,3 -diformyl-2,2 -
0
dihydroxy-1,1 -binaphthyl in ethanol (5 mL). The slurry was then
0
0
0
stirred at room temperature for at least 24 h. The precipitate was
then collected by filtration, washed with cold ethanol, and dried
in vacuum oven to obtain the pale yellow solid with 80% yield,
4
.1.3. (1R,2R)-(ꢀ)-N,N -Bis((R)-1,1 -2-hydroxy-2 -ben-zyloxy-3-
naphthylidene)-1,2-cyclohexanediamine 4
2
D
0
); 1H NMR
2 2
Cl
Yellow solid. 87% yield, ½
300 MHz, CDCl ): d 1.40–1.54 (m, 4H), 1.69–1.95 (m, 4H), 3.30
d, J = 9.3 Hz, 2H), 5.04 (s, 4H), 6.93–7.06 (m, 12H), 7.20–7.31 (m,
0H), 7.45 (d, J = 8.7 Hz, 2H), 7.76 (d, J = 9.9 Hz, 4H), 7.87 (d,
J = 7.8 Hz, 2H), 7.94 (d, J = 7.8 Hz, 2H), 8.47 (s, 2H), 13.2 (s, 2H);
C NMR (100 MHz, CDCl ): d 24.0, 32.7, 71.3, 72.9, 116.1, 117.1,
3
20.1, 120.5, 123.1, 123.8, 124.9, 125.2, 125.6, 125.8, 126.2 126.4,
26.8, 126.9, 127.3, 127.3, 128.0, 128.7, 129.5 129.6, 133.2, 133.9,
aꢁ
¼ ꢀ108 (c 1.0, CH
20
D
1
½
a
ꢁ
¼ ꢀ184 (c 0.5, CH
2 2 3
Cl ); H NMR (300 MHz, CDCl ): d 1.42–
(
(
1
3
1
.56 (m, 8H), 1.69–1.95 (m, 8H), 3.29 (br, 4H), 6.98 (m, 12H),
1
3
7
.74–7.76 (m, 8H), 8.46 (s, 4H), 13.2 (s, 4H); C NMR (75 MHz,
): d 24.1, 32.7, 73.0, 116.3, 120.5, 123.2, 124.4, 127.5, 128.2,
CDCl
128.9, 133.4, 135.1, 154.4, 165.1. HRMS (ESI): calcd for [M+H]
) requires m/z = 841.3754, found: 841.3741. Anal.
Calcd for C56 : C, 79.75; H, 5.70; N, 6.25. Found: C, 79.98;
H, 5.75; N, 6.66.
3
+
1
3
56 49 4 4
(C H N O
1
1
1
48 4 4
H N O
+
35.3, 137.5, 154.1, 154.4, 165.1. HRMS (ESI): Calcd. for [M+H]
(
C
62
H
51
N
2
O
4
) requires m/z = 887.3849, found: 887.3831. Anal.
Calcd for C62 /CHCl : C, 75.18; H, 5.11; N, 2.78. Found: C,
5.42; H, 5.09; N, 2.38.
0
0
H
50
N
2
O
4
3
4.1.8. Bis((1R,2R)-(ꢀ)-N,N -(S)-1,1 -bi-2-hydroxy-3-naphthyli-
7
dene)-1,2-cyclohexanediamine) 11
2
D
0
2 2
Cl H
). 1
Pale yellow solid. 80% yield. ½
a
ꢁ
¼ ꢀ558 (c 0.5, CH
0
0
0
NMR (300 MHz, CDCl ) d 1.42–1.56 (m, 2H), 1.70–1.96 (m, 2H),
4
.1.4. (1R,2R)-(ꢀ)-N,N -Bis((R)-1,1 -2-hydroxy-2 phenyl-3-
3
3
1
1
.27 (br, 1H), 6.96 (m, 3H), 7.75 (m, 2H), 8.45 (s, 1H), 13.2 (s,
H); C NMR (75 MHz, CDCl
23.2, 124.4, 127.5, 128.2, 128.9, 133.4, 135.1, 154.4, 165.1. HRMS
ESI): calcd for [M+H] (C56
found: 841.3741. Anal. Calcd for C56
N, 6.25. Found: C, 79.78; H, 5.70; N, 6.26.
naphthylidene)-1,2-cyclohexanediamine 5
1
3
2
D
0
2 2
Cl
); 1H NMR
3
) d 24.1, 32.7, 73.0, 116.3, 120.5,
Yellow solid. 87% yield, ½
300 MHz, CDCl ): d 1.40–1.54 (m, 4H), 1.69–1.95 (m, 4H), 3.28
d, J = 9.3 Hz, 2H), 6.77 (t, J = 7.8 Hz, 2H), 7.00–7.08 (m, 12H),
aꢁ
¼ ꢀ85 (c 1.0, CH
(
(
3
+
(
H
49
N
4
O
4
) requires m/z = 841.3754,
48 4 4
H N O : C, 79.75; H, 5.70;
7
8
.15–7.34 (m, 6H), 7.57–7.66 (m, 6H), 7.92 (d, J = 7.8 Hz, 2H),
.00 (d, J = 8.7 Hz, 4H), 8.36 (s, 2H), 13.0 (s, 2H);
1
3
C NMR
(
3
75 MHz, CDCl ): d 24.0, 32.7, 73.0, 119.7, 119.8, 122.9, 124.7,
1
1
1
25.6, 126.0, 126.2, 126.9, 127.2, 127.5, 127.7, 128.0, 128.1,
28.2, 128.3, 128.5, 128.7, 131.2, 132.5, 132.8, 132.9, 133.1,
35.1, 140.2, 142.1, 154.6, 164.9. HRMS (ESI): calcd for [M+H]
4
.2. General procedure for the preparation of new BINADCo(II)
complexes
+
(
C
60
H
47
N
2
O
2
) requires m/z = 827.3638, found: 827.3640. Anal.
Calcd for C60 Cl : C, 80.34; H, 5.31; N, 3.07. Found: C,
ꢂCH
0.65; H, 5.32; N, 2.78.
New ligand BINAD 1–11 (1 mmol), Co(OAc)
mmol) and 10 mL methanol were added in a three-necked flask.
2
ꢂ4H
2
O (0.249 g,
H
46
N
2
O
2
2
2
1
8
The mixture was heated at reflux for 2.5 h under Ar. The resulting
precipitate was collected by filtration, washed with cold methanol,
and dried in vacuum oven to give BINADCo(II) complexes in 80–
85% yield. The complexes were characterized by elemental analysis
and HRMS.
0
0
0
4
.1.5. (1S,2S-(ꢀ)-N,N -Bis((R)-1,1 -2-hydroxy-2 -phenyl-3-
naphthylidene)-1,2-cyclohexanediamine 7
2
D
0
2 2
Cl
). 1H NMR
Yellow solid. 87% yield. ½
300 MHz, CDCl ) d 1.41–1.54 (m, 4H), 1.70–1.96 (m, 4H), 3.28
d, J = 9.3 Hz, 2H), 6.78 (t, J = 7.8 Hz, 2H), 7.02–7.09 (m, 12H),
aꢁ
¼ þ197 (c 0.2, CH
(
(
3
Compound 1a: HRMS (ESI): calcd for m/z 763.2007 (C48
Co), found m/z 763.2018. Anal. Calcd for C48
75.49; H, 4.75; N, 3.67. Found: C, 75.23; H, 4.66; N, 3.55.
Compound 2a: HRMS (ESI): calcd for m/z 875.3259 (C56
Co), found m/z 875.3265. Anal. Calcd for C56
76.78; H, 5.98; N, 3.20. Found: C, 77.01; H, 5.98; N, 2.78.
Compound 3a: HRMS (ESI): calcd for m/z 791.2320
Co), found m/z 791.2332. Anal. Calcd for C50
: C, 69.87; H, 4.83; N, 3.20. Found: C, 69.54; H, 4.68; N,
36 2
H N -
O
4
36 2 4
H N O Co: C,
7
8
(
1
1
1
.16–7.35 (m, 6H), 7.56–7.66 (m, 6H), 7.93 (d, J = 7.8 Hz, 2H),
.01 (d, J = 8.7 Hz, 4H), 8.37 (s, 2H), 13.0 (s, 2H);
75 MHz, CDCl
25.6, 126.0, 126.2, 126.9, 127.2, 127.5, 127.7, 128.0, 128.1,
28.2, 128.3, 128.5, 128.7, 131.2, 132.5, 132.8, 132.9, 133.1,
35.1, 140.1, 142.1, 154.6, 164.9. HRMS (ESI): calcd for [M+H]
1
3
C NMR
52 2
H N -
) d 24.0, 32.7, 73.0, 119.7, 119.8, 122.9, 124.7,
O
4
52 2 4
H N O Co: C,
3
+
(C50H
40
N
2
O
4
40 2 4
H N O -
(
C
60
H
47
N
2
O
2
) requires m/z = 827.3638, found: 827.3640. Anal.
Calcd for C60 Cl : C, 80.34; H, 5.31; N, 3.07. Found: C,
ꢂCH
0.69; H, 5.29; N, 3.08.
CoꢂCH
2 2
Cl
H
46
N
2
O
2
2
2
3.22.
8
Compound 4a: HRMS (ESI): calcd for m/z 943.2946
Co), found m/z 943.2937. Anal. Calcd for C62
Co: C, 78.88; H, 5.13; N, 2.97. Found: C, 79.05; H, 4.94; N, 2.83.
Compound 5a: HRMS (ESI): calcd for m/z 883.2735
Co), found m/z 883.2728. Anal. Calcd for C60
OH: C, 79.99; H, 5.28; N, 3.06. Found: C, 79.63; H, 5.04; N,
(
C
62
48
H N
2
O
4
48 2 4
H N O -
0
0
0
4
.1.6. (1S,2S)-(ꢀ)-N,N -Bis((S)-1,1 -2-hydroxy-2 -butoxy-3-
naphthylidene)-1,2-cyclohexanediamine 9
2
D
0
1
Pale yellow solid. 86% yield. ½
300 MHz, CDCl ) d 0.71 (t, J = 7.5 Hz, 6H), 1.0–1.1 (m, 4H), 1.47–
.60 (m, 8H), 1.72–1.98 (m, 4H), 3.32 (d, J = 9.6 Hz, 2H), 3.98–4.2
m, 4H), 7.05–7.16 (m, 6H), 7.20–7.49 (m, 6H), 7.75 (dd,
J = 6.3 Hz, J = 8.4 Hz 4H), 7.92–7.99 (m, 6H), 8.47 (s, 2H), 13.12 (s,
aꢁ
¼ þ88 (c 1.0, CH
2
Cl
2
); HNMR
(C60H
44
N
2
O
2
44 2 2
H N O -
(
1
(
3
CoꢂCH
3
2.83.
Compound 6a: HRMS (ESI): calcd for m/z 763.7436
Co), found m/z 763.7441. Anal. Calcd for C48
Co: C, 75.49; H, 4.75; N, 3.67. Found: C, 75.11; H, 4.71; N, 3.42.
Compound 7a: HRMS (ESI): calcd for m/z 883.2735
Co), found m/z 883.2721. Anal. Calcd for C60
Co: C, 81.53; H, 5.02; N, 3.17. Found: C, 81.21; H, 4.94; N, 2.89.
Compound 8a: HRMS (ESI): calcd for m/z 763.2007
Co), found m/z 763.2019. Anal. Calcd for C48
Co: C, 75.49; H, 4.75; N, 3.67. Found: C, 75.22; H, 4.66; N, 3.35.
(C48
36
H N
2
O
4
36 2 4
H N O -
1
3
2
7
1
1
3
H); C NMR (75 MHz, CDCl ) d 13.5, 18.6, 24.0, 31.2, 32.7, 69.5,
2.8, 116.0, 117.2, 119.8, 120.3, 122.9, 123.5, 123.6, 124.8, 125.1,
26.3, 127.2, 127.9, 128.0, 128.6, 129.4, 133.0, 133.8, 135.3,
54.3, 154.6, 165.0; HRMS (ESI): calcd for [M+H] (C56
(C60H
44
N
2
O
2
44 2 2
H N O -
+
H
55
N
2
O
4
)
requires m/z = 819.4162, found: 819.4161. Anal. Calcd for
: C, 81.90; H, 6.51; N, 3.14. Found: C, 82.00; H, 6.45;
C
56
H
54
N
2
O
4
(C48
36
H N
2
O
4
36 2 4
H N O -
N, 3.34.

1
952
L. Jin et al. / Tetrahedron: Asymmetry 19 (2008) 1947–1953
Compound 9a: HRMS (ESI): calcd for m/z 875.3259
Co), found m/z 875.3271. Anal. Calcd for C56
Co: C, 76.78; H, 5.98; N, 3.20. Found: C, 77.01; H, 6.02; N, 2.81.
Compound 10a: HRMS (ESI): calcd for m/z 954.2027
Co ), found m/z 954.2034. Anal. Calcd for C56
: C, 70.44; H, 4.64; N, 5.87. Found: C, 70.65; H, 4.49; N, 5.76.
Compound 11a: HRMS (ESI): calcd for m/z 954.2027
Co ), found m/z 954.2021. Anal. Calcd for C56
: C, 70.44; H, 4.64; N, 5.87. Found: C, 70.79; H, 4.45; N, 5.84.
Compound 11b: 1H NMR (300 MHz, CDCl
8H), 3.23 (br, 2H), 3.45 (m, 3H), 6.93–8.44 (m, 12H).
Compound 2e: H NMR (300 MHz, CDCl ): d 0.52–1.84 (m, 22H),
3
3.22 (br, 2H), 3.42 (br, 3H), 3.93 (br, 4H), 6.99–7.37 (m, 18H), 7.65
3
): d 1.42–1.95 (m,
(
C
56
H
52
N
2
O
4
52 2 4
H N O -
1
(
Co
C
56
H
44
N
4
O
4
2
H
44
N
4
O
4
-
(br, 4H), 7.80 (br, 2H), 7.88 (br, 2H), 8.38 (s, 2H).
1
2
Compound 2f: H NMR (300 MHz, CDCl
3
): d 0.57–2.18 (m, 22H),
3.49 (br, 2H), 5.25 (br, 4H), 7.26–7.66 (m, 28H).
(
Co
C
56
H
44
N
4
O
4
2
44 4 4
H N O -
2
4.4. General procedure for the asymmetric cycloaddition of
epoxides with carbon dioxide
4
.3. General procedure for the preparation of new
All reactions were carried out in a 100 mL stainless-steel pres-
sure reactor was charged with catalyst (0.05 mmol), epoxide
BINADCo(III)X catalysts
(
100 mmol), and co-catalyst (0.1 mmol). The reaction vessel was
The relevant acid (0.05 mmol) was added to a solution of com-
plex BINADCo(II) (0.05 mmol) in 5 mL CH Cl , and stirred at room
temperature for 4 h. After removing the solvent under reduced
pressure, a solid of catalyst, BINADCo(III)X was obtained with
purged three times with carbon dioxide, and filled carbon dioxide
to 0.5 MPa, stirred. When the pressure of reactor declined after
appropriate time, it was released to terminate the reaction. After
removing the unreacted epoxide weighed to measure its conver-
sion, chiral cyclic carbonate (R = Me, Et, CH
late the yield of cyclic carbonate, was distilled under vacuum as
a colorless liquid or it (R = Ph, PhOCH ) was recrystallized with eth-
anol. The H NMR and TOFMS of product mixture were also carried
out showing no side products of copolymer of epoxide and carbon
dioxide.
2
2
quantity yield. When the complex 1b was treated with CsCO
3
or
2
Cl), weighed to calcu-
2
9
MgEt in THF, it yielded 1b-Cs or 1b-Mg catalyst, respectively.
2
The characterization results of catalysts 1b–11b, 2c–2f using
2
HRMS are the same of 1a–11a.
1
1
Compound 1b: H NMR (300 MHz, CDCl
3
): d 1.40–1.54 (m, 4H),
1
5
.69–1.95 (m, 4H), 3.29 (d, J = 9.6 Hz, 2H), 3.58 (q, J = 7.2 Hz, 3H),
.09 (s, 2H), 6.97–7.95 (m, 22H), 8.47 (s, 2H).
1
Compound 2b: H NMR (300 MHz, CDCl
3
): d 0.59 (t, J = 7.2 Hz,
Acknowledgment
6H), 0.81–1.00 (m, 4H), 1.18–1.23 (m, 4H), 1.37–1.91 (m, 8H),
3.27 (d, J = 9.3 Hz, 2H), 3.48 (q, J = 7.2 Hz, 3H), 3.95–4.01 (m, 4H),
7.04–7.31 (m, 12H), 7.45 (d, J = 8.7 Hz, 2H), 7.72 (s, 2H), 7.74 (d,
We are grateful to the financial support of the National Natural
Science Foundation of China (NSFC 20773055, 20021001).
J = 9.0 Hz, 2H), 7.87 (d, J = 8.1 Hz, 2H), 7.96 (d, J = 8.1 Hz, 2H),
1
3
8
3
1
1
3
.45 (s, 2H); C NMR (75 MHz, CDCl ): d 13.4, 18.6, 21.2, 23.9,
References
1.2, 32.6, 69.4, 72.7, 115.9, 117.2, 119.7, 120.3, 122.9, 123.5,
23.6, 124.8, 125.1, 126.3, 127.2, 127.8, 127.9, 128.6, 129.4,
32.9, 133.8, 135.3, 154.3, 154.5, 165.1, 196.8.
1. Darensbourg, D. J.; Holtcamp, M. W. Coord. Chem. Rev. 1996, 153, 155–174.
2. Darensbourg, D. J.; Mackiewicz, R. M.; Phelps, A. L.; Billodeaux, D. R. Acc. Chem.
Res. 2004, 37, 836–844.
1
Compound 3b: H NMR (300 MHz, CDCl
3
): d 1.33–1.84 (m, 8H),
3
4
.
.
Coates, G. W.; Moore, D. R. Angew. Chem., Int. Ed. 2004, 43, 6618.
Sugimoto, H.; Inoue, S. J. Polym. Sci. Part A 2004, 42, 5561.
3
7
.25 (d, J = 9.3 Hz, 2H), 3.41 (q, J = 7.2 Hz, 3H), 3.71 (s, 6H), 6.93–
.06 (m, 6H), 7.20–7.31 (m, 4H), 7.48 (d, J = 9.9 Hz, 2H), 7.74 (d,
5. Jin, L.-L.; Jing, H.-W.; Chang, T.; Bu, X.-L.; Wang, L.; Liu, Z.-L. J. Mol. Catal. A:
Chem. 2007, 261, 262–266.
J = 11.7 Hz, 4H), 7.81 (d, J = 1.2 Hz, 2H), 7.88 (d, J = 7.8 Hz, 2H),
6
.
Kim, H. S.; Kim, J. J.; Lee, S. D.; Lah, M. S.; Moon, D.; Jang, H. G. Chem. Eur. J. 2003,
, 678–686.
Shen, Y.; Duan, W.-L.; Shi, M. Adv. Synth. Catal. 2003, 345, 337–340.
8
.00 (d, J = 7.8 Hz, 2H), 8.45 (s, 2H).
Compound 4b: H NMR (300 MHz, CDCl
9
1
3
): d 1.42–1.92 (m, 8H),
7
.
3
7
.30 (d, J = 9.3 Hz, 2H), 3.48 (q, J = 7.2 Hz, 3H), 5.09 (s, 4H), 6.93–
.06 (m, 12H), 7.20–7.31 (m, 10H), 7.45 (d, J = 8.7 Hz, 2H), 7.75
8. Jing, H.-W.; Nguyen, S. T. J. Mol. Catal. A: Chem. 2007, 261, 12–15.
Kim, Y. J.; Varma, R. S. J. Org. Chem. 2005, 70, 7882–7891.
9.
10. Shen, Y.-M.; Duan, W.-L.; Shi, M. J. Org. Chem. 2003, 68, 1559–1562.
(
s, 2H), 7.76 (d, J = 9.3 Hz, 2H), 7.88 (d, J = 7.2 Hz, 2H), 7.94 (d,
11. Jiang, J.-L.; Gao, F.-X.; Hua, R.-M.; Qiu, X.-Q. J. Org. Chem. 2005, 70, 381–383.
J = 9.3 Hz, 2H), 8.47 (s, 2H).
12. Huang, J.-W.; Shi, M. J. Org. Chem. 2003, 68, 6705–6709.
13. Sit, W. N.; Ng, S. M.; Kwong, K. Y.; Lau, C. P. J. Org. Chem. 2005, 70, 8583–
1
Compound 5b: H NMR (300 MHz, CDCl
3
): d 1.42–2.13 (m, 8H),
8586.
3
7
.25 (d, J = 9.3 Hz, 2H), 3.45 (q, J = 7.2 Hz, 3H), 6.74–7.30 (m, 22H),
.54 (s, 2H), 7.61 (d, J = 9.0 Hz, 2H), 7.89 (d, J = 7.5 Hz, 2H), 7.97 (d,
14. Alvaro, M.; Baleizao, C.; Das, D.; Carbonell, E.; Garcia, H. J. Catal. 2004, 228, 254–
258.
15. Shaikh, A.-A. G.; Sivaram, S. Chem. Rev. 1996, 96, 951–976.
J = 8.1 Hz, 4H), 8.33 (s, 2H).
1
16. Biggadike, K.; Angell, R. M.; Burgess, C. M.; Farrell, R. M.; Hancock, A. P.; Harker,
A. J.; Irving, A. J.; Irving, W. R.; Ioannou, C. P.; Procopiou, A.; Shaw, R. E.;
Solanke, Y. E.; Singh, O. M. P.; Snowden, M. A.; Stubbs, R.; Walton, S.; Weston,
H. E. J. Med. Chem. 2000, 43, 19–21.
Compound 6b: H NMR (300 MHz, CDCl
3
): d 1.40–1.54 (m, 4H),
1
5
.69–1.95 (m, 4H), 3.29 (d, J = 9.6 Hz, 2H), 3.58 (q, J = 7.2 Hz, 3H),
.09 (s, 2H), 6.97–7.95 (m, 22H), 8.47 (s, 2H).
Compound 7b: H NMR (300 MHz, CDCl ): d 1.42–2.13 (m, 8H),
3
1
17. Paddock, R. L.; Nguyen, S. T. J. Am. Chem. Soc. 2001, 123, 11498–11499.
1
1
8. Caló, V.; Nacci, A.; Monopoli, A.; Fanizzi, A. Org. Lett. 2002, 4, 2561–2563.
9. Yang, H.; Gu, Y.; Deng, Y.; Shi, F. Chem. Commun. 2002, 274–275.
3
7
.25 (d, J = 9.3 Hz, 2H), 3.45 (q, J = 7.2 Hz, 3H), 6.74–7.30 (m, 22H),
.54 (s, 2H), 7.61 (d, J = 9.0 Hz, 2H), 7.89 (d, J = 7.5 Hz, 2H), 7.97 (d,
20. Yano, T.; Matsui, H.; Koike, T.; Ishiguro, H.; Fujihara, H.; Yoshihara, M.;
Maeshima, T. Chem. Commun. 1997, 1129–1130.
J = 8.1 Hz, 4H), 8.33 (s, 2H).
2
2
1. Paddock, R. L.; Nguyen, S. T. Chem. Commun. 2004, 1622–1623.
2. Albrecht, B.; Marc, B. Org. Lett. 2006, 8, 4401–4404.
1
Compound 8b: H NMR (300 MHz, CDCl
3
): d 1.40–1.54 (m, 4H),
1
5
.69–1.95 (m, 4H), 3.29 (d, J = 9.6 Hz, 2H), 3.58 (q, J = 7.2 Hz, 3H),
.09 (s, 2H), 6.97–7.95 (m, 22H), 8.47 (s, 2H).
Compound 9b: H NMR (300 MHz, CDCl ): d 0.59 (t, J = 7.2 Hz,
3
23. Chen, S.; Kawthekar, R. B.; Kim, G. J. Tetrahedron Lett. 2007, 48, 297–300.
2
2
2
2
2
4. Lu, X.-B.; Liang, B.; Zhang, Y.-J.; Tian, Y.-Z.; Wang, Y.-M.; Bai, C.-X.; Wang, H.;
Zhang, R. J. Am. Chem. Soc. 2004, 126, 3732–3733.
5. Chang, T.; Jing, H.-W.; Jin, L.-L.; Qiu, W.-Y. J. Mol. Catal. A: Chem. 2007, 264, 241–
247.
6. Yamada, W.; Kitaichi, Y.; Tanaka, h.; Kojima, T.; Sato, M.; Ikeno, T.; Yamada, T.
Bull. Chem. Soc. Jpn. 2007, 80, 1391–1401.
7. Tokunaga, M.; Larrow, J. F.; Kakiuchi, F.; Jacobsen, E. N. Science 1997, 277, 936–
938.
1
6H), 0.81–1.00 (m, 4H), 1.18–1.23 (m, 4H), 1.37–1.91 (m, 8H),
3.27 (d, J = 9.3 Hz, 2H), 3.48 (q, J = 7.2 Hz, 3H), 3.95–4.01 (m, 4H),
7.04–7.31 (m, 12H), 7.45 (d, J = 8.7 Hz, 2H), 7.72 (s, 2H), 7.74 (d,
J = 9.0 Hz, 2H), 7.87 (d, J = 8.1 Hz, 2H), 7.96 (d, J = 8.1 Hz, 2H),
8. Gansauer, A.; Baechuk, A.; Keller, F.; Schmitt, M.; Grimme, S.; Gerenkmp, M.;
Muck-Lichtenfeld, C.; Daasbjerg, K.; Svith, H. . J. Am. Chem. Soc. 2007, 129,
8
8
.45 (s, 2H).
Compound 10b: 1H NMR (300 MHz, CDCl
3
): d 1.42–1.95 (m,
1359–1371.
H), 3.25 (br, 2H), 3.48 (m, 3H), 6.98–8.46 (m, 12H).
29. DiMauro, E. F.; Kozlowski, M. C. Organometallics 2002, 21, 1454–1461.

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