Axially chiral N-heterocyclic carbene gold(I) complex catalyzed asymmetric Friedel-Crafts/cyclization reaction of nitrogen-tethered 1,6-enynes with indole derivatives

Article abstract of DOI:10.1016/j.tetasy.2011.12.004

A class of axially chiral NHC-Au(I) complexes has been applied to the asymmetric Friedel-Crafts/cyclization reaction of 1,6-enynes 14 with indole derivatives 15, affording the corresponding Friedel-Crafts and intramolecular cyclization products 16 in good yields with moderate ee values under mild conditions.

Full text of DOI:10.1016/j.tetasy.2011.12.004

Tetrahedron: Asymmetry 22 (2011) 2029–2038
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Axially chiral N-heterocyclic carbene gold(I) complex catalyzed asymmetric
Friedel–Crafts/cyclization reaction of nitrogen-tethered 1,6-enynes with
indole derivatives
Jinming Yang a, Rui Zhang a, Wenfeng Wang a, Zhen Zhang a, Min Shi a,b,
⇑
a Key Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry & Molecular Engineering, East China University of Science and Technology,
130 Mei-Long Road, Shanghai 200237, China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Road, Shanghai 200032, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A class of axially chiral NHC–Au(I) complexes has been applied to the asymmetric Friedel–Crafts/cycliza-
tion reaction of nitrogen-tethered 1,6-enynes 14 with indole derivatives 15, affording the corresponding
Friedel–Crafts and intramolecular cyclization products 16 in good yields and with moderate ee values
under mild conditions.
Received 8 November 2011
Accepted 6 December 2011
Available online 12 January 2012
Ó 2011 Elsevier Ltd. All rights reserved.
1. Introduction
N-Heterocyclic carbenes (NHCs) represent a growing class of
ligands in transition-metal catalysis,8 which have several typical
Over the past decade, homogeneous gold catalysis has seen ra-
pid growth for C–C, C–O or C–N bond forming reactions mainly due
to the soft carbophilic Lewis acid properties of gold complexes to-
ward C–C multiple bonds.1 In comparison to other transition metal
catalysts, gold complexes can efficiently catalyze reactions under
very mild conditions that are tolerant of air or moisture to give
excellent chemoselectivity and wide functional group compatibil-
ity. Although the first example of a gold-catalyzed enantioselective
reaction was reported by Hayashi and Ito in 1986 for the aldol con-
densation between isocyanates and aldehydes,2 gold-catalyzed
asymmetric transformations still remains a challenging topic
although there have been a few investigations at the present stage3
despite the rapid development of several synthetic applications.4
To the best of our knowledge, most studies on this topic have been
focused on the gold activation of allenes toward nucleophilic
attack, such as the asymmetric hydrofunctionalization of alle-
nes,4b–f [2+2] cycloaddition and cycloisomerization of enallenes.5
Only a few reports have addressed the asymmetric activation of
substrates containing an alkyne functional group.4a,6 The difficulty
of enantioselective gold(I)-catalyzed transformations is probably
due to the linear coordination geometry of the Au(I) center with
the reaction site far away from the chiral environment, thus special
strategies or chiral ligands are needed to deliver spatial arrange-
ments to the opposite site of the metal cation.3,7
features such as stability to air and moisture, low toxicity, strong
r
-donor and poor
p
-acceptor properties.9 So far, in almost all of
the successful systems for asymmetric gold catalysis, chiral phos-
phines were employed as ligands,2–6 while the number of chiral
NHC–Au(I) complexes reported as catalysts remains rare6f,g,10
although NHCs have emerged as an effective alternative for a num-
ber of homogeneous gold catalysts.8k,11 During our ongoing survey
of the literature, there is only one relevant paper reported by
Tomioka et al. using C2-symmetric NHC–Au(I) complexes in the
cycloisomerization of 1,6-enynes, providing the corresponding
cyclopentane products in high yields but along with moderate
enantioselectivities (up to 59% ee).6g Based upon our previous suc-
cessful examples of NHC–metal complex-catalyzed asymmetric
transformations,12 we reported that the sterically less hindered
gold(I) complex (aR)-6 shown in Scheme 1 with a pyrrolidin-1-yl
group, was the best catalyst in the gold(I)-catalyzed asymmetric
acetoxycyclization of 1,6-enyne, giving products in >99% yield
and with (ꢀ)59% ee at 0 °C. The sterically less hindered gold(I)
catalyst (aS)-2a (Scheme 1) as well was the best catalyst in the
asymmetric oxidative rearrangement of 1,6-enynes, affording the
corresponding aldehydes in excellent yields (up to >99%) and with
low to modest enantioselectivities (3.1–70% ee) using PhCl as the
solvent at 10 °C.13 The steric environment around the gold center
can significantly affect the product’s enantioselectivity while the
substrates used can also impact to a large extent, the reaction out-
come; we thus attempted asymmetric catalysis with these chiral
NHC–Au complexes. Herein we report that these axially chiral gold
complexes are also reasonably effective in the asymmetric Friedel–
Crafts/cyclization reaction of nitrogen-tethered 1,6-enynes 14 with
⇑
Corresponding author. Fax: +86 21 64166128.
E-mail address: Mshi@mail.sioc.ac.cn (M. Shi).
0957-4166/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetasy.2011.12.004

2030
J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
Our previous work
N
N
N
N
N
Au
Au
I
I
NHAc
(aR)-6
2a
(aS)-
NHC-Au(I) cat. (aR)-6 (5 mol%)
Ts
N
AgSbF6 (5 mol%)
H
Ts
N
Ph
AcOH (20 equiv, dry), DCE
0 °C, 24 h
H
Ph
OAc
>99% yield, -59% ee
CHO
2a
NHC-Au(I) cat. (aS)- (5 mol%)
AgSbF6 (5 mol%)
X
X
R
Ph2SO (1.5 equiv), PhCl
4AMS, 10 °C
R
H
X = O, NR'
R = Ar
86-99% yields
3. 1-70% ee
This work
R1
N
4
NHC-Au(I)cat. (5 mol%)
R2
3
R4
5
AgSbF6 (5 mol%)
R1
N
R4
2
+
H
6
DCE, 25 °C, 24 h
N 1
R3
H
7
R2
N
14
15
R3
16, up to 66% ee
Scheme 1. Axially chiral NHC–Au complex catalyzed asymmetric reactions.
indole derivatives 15, giving the corresponding Friedel–Crafts and
intramolecular cyclization products 16 in good yields and with
moderate ee values under mild conditions (Scheme 1).14
reaction (Table 1, entries 8–13). This may be due to the counter
anion of SbF6 making the gold cationic species more stable in this
reaction. In terms of the yield, we found that using DCE as the sol-
vent, 16a was formed in a 73% yield and 37% ee value with a 99:1 dr
value (Table 1, entry 1). Since the solvents employed could signifi-
cantly affect the reaction rates, all of the reactions shown in Table 1
were quenched until when they were complete, based on the TLC
monitoring.
We next examined various axially chiral gold complexes in the
asymmetric Friedel–Crafts/cyclization reaction of 1,6-enyne 14a
with indole derivative 15a in DCE at 25 °C and the results are
shown in Table 2. These gold complexes are all fairly effective cat-
alysts in this reaction to afford 16a in moderate to good yields
along with 4–46% ee values (Table 2, entries 1–14). Axially chiral
gold complex (aS)-7 produced 16a in an 89% yield along with
46% ee and 12:1 dr, this was the best result in this reaction (Table 2,
entry 10).
Having determined the optimal reaction conditions, the general-
ity of this gold(I) complex-catalyzed asymmetric Friedel–
Crafts/cyclization reaction was next examined using a variety of
1,6-enynes 14 and indole derivatives 15 and the results are
summarized in Table 3. When the R1 sulfonyl group was 4-bro-
mobenzenesulfonyl (Bs), 4-nitrobenzenesulfonyl (Ns) or 2,4,6-tri-
isopropylbenzenesulfonyl, the reaction proceeded smoothly to
afford the corresponding products 16b–16d in good yields but along
with 2–44% ee values, suggesting that the electronic properties and
steric effects of the sulfonyl group play a significant role in this
reaction (Table 3, entries 1–3). Moreover, when R2 was either an
electron-rich or -poor aromatic group, the reaction proceeded
2. Results and discussion
Axially chiral NHC–Au(I) complexes 1–1113 and the intermedi-
ates 12 and 13 (Fig. 1) derived from optically active binaphthyl-
2,20-diamine (BINAM) (see Scheme 2 in the Section 4), which were
employed in the asymmetric Friedel–Crafts/cyclization reaction of
1,6-enynes 14 with indole derivatives 15. The new NHC–Au(I)
complex (aR)-4 was characterized by NMR, MALDI-MS, and IR
spectroscopic data and its structure has been further confirmed
by the X-ray diffraction study of single crystals grown from a solu-
tion of mixed petroleum ether/CH3CO2Et/CH2Cl2 (1:1:1). Its ORTEP
drawing is shown in Figure 2.15
Initial examination of the asymmetric Friedel–Crafts/cyclization
reaction of 1,6-enyne 14a with indole derivative 15a was carried
out in various solvents using gold complex (aR)-6 as the catalyst
in the presence of silver salts and the results are summarized in
Table 1. As can be seen from Table 1, the desired product 16a was
obtained in good yields in 1,2-dichloroethane (DCE), chloroben-
zene, toluene, and dichloromethane using gold complex (aR)-6 as
the catalyst in the presence of AgSbF6 (Table 1, entries 1–4). In ace-
tonitrile, tetrahydrofuran (THF), and ether, the desired product 16a
was formed in lower yields, indicating that the reaction could not
proceed efficiently in electron-donating solvents (Table 1, entries
5–7). The examination of other silver salts and other counter ions,
such as NaBARF, revealed that AgSbF6 was the best cocatalyst in this

J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
2031
Ph
I
N
N
N
N
N
N
N
N
Au
Au
I
I
Au
Ph
I
Au
I
Au
H
N
N
NHAc
NHAc
N
O
3
(aR)-1
(aS)-
(aS)-2a
(aS)-2b
Ph
N
N
N
N
N
N
N
N
N
Au
I
Au Cl
Au Cl
Au
I
Au
I
H
N
H
N
N
N
N
N
O
Ph
O
Boc
Boc
(aR)-6
5
(aS,R)-
4
(aR)-
5
(aS,S)-
N
N
N
N
N
N
N
N
N
N
Au
Ph
I
Au
I
Au
I
Au
Ph
I
H
N
N
Ph
6
(aS)-
(aS)-7
9
(aS)-
(aS)-8
N
N
N
N
N
Au
I
HO
Au
I
N
10
(aS)-
(aS)-11
Figure 1. Axially chiral gold complexes employed in the asymmetric Friedel–Crafts/cyclization reaction of 1,6-enynes 14 with indole derivatives 15.
Bn
Bn
Cl
N
N
N
N
N
(Me2S)AuCl (2 equiv)
NaOAc (4 equiv)
N
N
N
N
N
N
BnCl
Au Cl
Au Cl
1,4-dioxane
100 °C, 48 h
CH3CN, 85 °C
48 h, 37%
Cl
N
Bn
Bn
12
(aR)-
13
4
(aR)-
(aR)-
Scheme 2.
efficiently to give the corresponding adducts 16e–16i in good yields
along with 42–62% ee values and high dr values, indicating that the
electronic properties of the R2 group did not have a significant
impact on the reaction outcome (Table 3, entries 4–8). Furthermore,
the R3 group on the indole derivative could also be an H atom, Bn
group or Boc-protecting group, giving the corresponding products

2032
J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
recorded using a Bruker AM-300 or AM-400 spectrometer in CDCl3
with tetramethylsilane (TMS) as an internal standard. 1H NMR and
13C NMR chemical shifts were referenced to 0.00 ppm (TMS) and
77.0 ppm (CDCl3), respectively; coupling constants J are given in
Hz. Optical rotations were determined at 589 nm (sodium D line)
using a Perkin-Elmer-341 MC digital polarimeter; [
given in units of 10 degꢀ1 cm2 gꢀ1. Infrared spectra were recorded
on a Perkin-Elmer PE-983 spectrometer with absorption in cmꢀ1
a]D-values are
.
Chiral HPLC was performed by using a SHIMADZU SPD-10A vp ser-
ies with chiral columns (Chiralpak AD-H, OD-H and IC-H columns,
4.6 ꢁ 250 mm, Daicel Chemical Ind., Ltd). Mass spectra were re-
corded by EI, ESI, and MALDI and HRMS was measured on a HP-
5989 instrument. Flash column chromatography was performed
using 300–400 mesh silica gel. For thin-layer chromatography
(TLC), silica gel plates (Huanghai GF254) were used. The single
crystals for X-ray diffraction were obtained by recrystallization
from CH2Cl2/petroleum ether (1:1).
4.2. Preparation of axially chiral NHC–Au(I) complexes 1, 2a, 2b,
3 and 5–11
Complexes 1, 2a, 2b, 3 and 5–11 are the known compounds and
were synthesized according to the literature.17
4.2.1. Complex (aR)-1
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
4.24 (s, 6H), 6.54 (t, J = 8.0 Hz, 2H), 6.60 (d, J = 8.4 Hz, 2H), 7.14 (t,
J = 7.6 Hz, 2H), 7.46 (d, J = 8.4 Hz, 2H), 7.55–7.70 (m, 8H), 7.95 (d,
J = 9.2 Hz, 2H), 7.99 (d, J = 8.4 Hz, 2H).
Figure 2. ORTEP drawing of NHC–Au(I) complex 4.
16j–16n in good yields along with 54–66% ee values and high dr val-
ues under the standard conditions (Table 3, entries 9–13). Only
when R2 was a hydrogen atom or an aliphatic group such as sub-
strates 14j (R2 = H), 14k (2 ꢁ R2 = Me), or 14l (2 ꢁ R2 = Me), did the
reaction provide complex product mixtures under the standard con-
ditions (Table 3, entries 14–16). Their spectroscopic data have been
summarized in Section 4 and the major product of 16 was unambig-
uously assigned as having the anti-configuration on the basis of X-
ray diffraction data of 16l. Its ORTEP drawing is shown in Figure 3.16
We used 16l of 66% ee for recrystallization from CH2Cl2/petroleum
ether (1:1). The single crystal obtained is a racemic product. There-
fore, while the relative configuration can be determined, the abso-
lute configuration cannot be determined at the present stage.
4.2.2. Complex (aS)-2a
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
2.07 (s, 3H), 3.94 (s, 3H), 6.82 (t, J = 8.0 Hz, 1H), 6.89 (d, J = 8.4 Hz,
1H), 7.12–7.22 (m, 5H), 7.25–7.29 (m, 1H), 7.39–7.46 (m, 2H),
7.64–7.69 (m, 3H), 7.80 (d, J = 8.4 Hz, 1H), 8.00 (d, J = 8.8 Hz, 1H),
8.11 (d, J = 8.4 Hz, 1H), 8.25 (d, J = 9.2 Hz, 1H).
4.2.3. Complex (aS)-2b
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
1.99 (s, 3H), 5.37 (d, J = 15.6 Hz, 1H), 5.84 (d, J = 15.6 Hz, 1H), 6.82–
6.84 (m, 2H), 6.89 (t, J = 7.2 Hz, 1H), 6.95–7.09 (m, 5H), 7.19 (t,
J = 7.2 Hz, 1H), 7.28–7.29 (m, 4H), 7.48–7.49 (m, 2H), 7.66 (d,
J = 8.4 Hz, 1H), 7.68–7.72 (m, 1H), 7.74 (d, J = 8.8 Hz, 1H), 7.85 (d,
J = 8.8 Hz, 1H), 8.10 (d, J = 8.8 Hz, 1H), 8.13 (d, J = 8.4 Hz, 1H),
8.29 (d, J = 8.4 Hz, 1H).
3. Conclusion
In conclusion, axially chiral gold(I) complex 7 prepared from
optically active BINAM was found to be a fairly effective catalyst
for the asymmetric Friedel–Crafts/cyclization reaction of 1,6-eny-
nes 14 with indole derivatives 15 in DCE under mild conditions
to give the corresponding products 16 in good yields along with
moderate to good enantioselectivities. Efforts are currently under-
way to elucidate the mechanistic details of this asymmetric reac-
tion and to find further applications for these axially chiral gold
complexes.
4.2.4. Complex (aS)-3
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
3.77 (s, 3H), 6.79 (d, J = 8.4 Hz, 1H), 7.02 (t, J = 7.2 Hz, 1H), 7.14 (d,
J = 8.0 Hz, 1H), 7.20–7.30 (m, 5H), 7.36 (t, J = 7.2 Hz, 1H), 7.43–7.47
(m, 2H), 7.56–7.66 (m, 3H), 7.72 (d, J = 9.2 Hz, 2H), 7.76–7.81 (m,
3H), 8.21 (d, J = 8.4 Hz, 1H), 8.28 (d, J = 8.8 Hz, 1H), 8.40 (d,
J = 9.2 Hz, 1H).
4.2.5. Complex (aS,S)-5
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
1.20 (s, 9H), 1.62–2.10 (m, 6H), 2.86 (s, 1H), 3.77 (s, 3H), 4.31 (br,
1H), 7.10–7.13 (m, 1H), 7.21–7.32 (m, 3H), 7.38 (t, J = 7.6 Hz, 1H),
7.45 (d, J = 8.0 Hz, 1H), 7.50–7.54 (m, 1H), 7.59 (t, J = 7.2 Hz, 2H),
7.63 (d, J = 9.2 Hz, 1H), 7.73 (t, J = 7.6 Hz, 1H), 7.89 (d, J = 8.8 Hz,
1H), 8.08 (s, 1H), 8.20 (d, J = 8.0 Hz, 1H), 8.31 (d, J = 9.2 Hz, 1H),
8.53 (s, 1H).
4. Experimental
4.1. General
Unless otherwise stated, all reactions and manipulations were
performed using standard Schlenk techniques. All solvents were
purified by distillation using standard methods. Commercially
available reagents were used without further purification. Melting
points were determined on a digital melting point apparatus and
temperatures are uncorrected. 1H and 13C NMR spectra were
4.2.6. Complex (aS)-6
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
1.80–1.83 (m, 2H), 1.95–2.01 (m, 2H), 2.61 (t, J = 8.0 Hz, 2H),

J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
2033
Table 1
Asymmetric Friedel–Crafts/cyclization reaction of 1,6-enyne 14a with indole derivative 15a in various solvents in the presence of (aR)-6 and silver salts
6
NHC-Au(I) cat. (aR)- (5 mol%)
Ph
Ts
N
AgX (5 mol%)
+
Ts
N
N
solvent, 25 °C
H
H
Ph
N
15a
14a
16a
Entrya
AgX
Solvent
Time (d)
Yieldb(%)
drc
eed(%)
1
2
3
4
5
6
7
8
9
10
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgSbF6
AgOTf
DCE
PhCl
Toluene
CH2Cl2
CH3CN
THF
Et2O
DCE
DCE
DCE
1
2
2
1.5
7
2.5
5
1
2.5
7
73
83
69
77
40
35
46
59
44
NR
>99:1
12:1
>99:1
53:1
>99:1
>99:1
26:1
(ꢀ)37
(ꢀ)14
(ꢀ)24
(ꢀ)22
(ꢀ)13
(ꢀ)18
(ꢀ)20
(ꢀ)5
>99:1
>99:1
AgClO4
4-NO2PhCO2Ag
(ꢀ)37
e
e
—
—
CO2Ag
e
e
11
DCE
6
NR
—
—
O2N
NO2
O
Ag
e
e
12
13
C
P
O
DCE
DCE
5
5
NR
—
—
O
Ag
e
e
NaBARF
Trace
—
—
a
b
c
Reaction conditions: 5 mol % of catalyst; 5 mol % of AgX; 0.1 mmol of 14a; 3.0 equiv of 15a; 1.0 mL of dry solvent.
Isolated yields.
Determined by 1H NMR spectroscopy.
Determined by chiral HPLC using a Chiralpak AD-H column.
Not determined.
d
e
2.99–3.05 (m, 2H), 4.06 (s, 3H), 6.19 (d, J = 8.4 Hz, 1H), 6.36 (t,
J = 8.0 Hz, 1H), 6.71 (d, J = 8.8 Hz, 1H), 7.00 (t, J = 7.6 Hz, 1H),
7.12–7.17 (m, 3H), 7.19–7.23 (m, 1H), 7.27 (d, J = 9.2 Hz, 1H),
7.47–7.53 (m, 2H), 7.63–7.67 (m, 1H), 7.83 (d, J = 8.8 Hz, 1H),
7.92 (d, J = 8.4 Hz, 1H), 8.06 (d, J = 8.0 Hz, 1H), 8.12 (d, J = 8.8 Hz,
1H).
(t, J = 7.2 Hz, 4H), 7.00 (t, J = 7.2 Hz, 2H), 7.15–7.20 (m, 2H), 7.25–
7.34 (m, 5H), 7.42 (d, J = 9.2 Hz, 1H), 7.51 (t, J = 7.2 Hz, 1H), 7.65–
7.67 (m, 1H), 7.74 (d, J = 8.8 Hz, 1H), 8.00 (d, J = 8.0 Hz, 1H), 8.14
(d, J = 8.8 Hz, 1H).
4.2.10. Complex (aS)-10
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
3.76 (s, 3H), 6.68 (ddd, J = 2.8, 6.0, 8.4 Hz, 1H), 6.78 (d, J = 8.0 Hz,
1H), 6.90 (dt, J = 1.2, 8.0 Hz, 1H), 6.97 (d, J = 8.0 Hz, 1H), 7.16–
7.17 (m, 2H), 7.25–7.40 (m, 5H), 7.43–7.47 (m, 1H), 7.55 (dt,
J = 1.2, 8.0 Hz, 1H), 7.59–7.65 (m, 2H), 7.72 (d, J = 7.6 Hz, 1H),
7.80 (d, J = 8.4 Hz, 1H), 7.86 (d, J = 8.0 Hz, 1H), 8.10 (d, J = 8.0 Hz,
1H), 8.21 (d, J = 8.4 Hz, 1H), 8.48 (s, 1H), 11.82 (s, 1H).
4.2.7. Complex (aS)-7
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
2.46 (s, 6H), 4.07 (s, 3H), 6.33 (d, J = 8.0 Hz, 1H), 6.41 (t, J = 7.2 Hz,
1H), 6.89 (d, J = 8.8 Hz, 1H), 7.00 (t, J = 7.6 Hz, 1H), 7.16–7.27 (m,
4H), 7.42–7.45 (m, 2H), 7.58–7.65 (m, 3H), 7.85 (d, J = 8.4 Hz,
1H), 8.07 (d, J = 7.6 Hz, 1H), 8.16 (d, J = 8.4 Hz, 1H).
4.2.8. Complex (aS)-8
4.2.11. Complex (aS)-11
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
3.95 (s, 3H), 4.38 (dd, J = 6.0, 16.0 Hz, 1H), 4.56 (t, J = 5.6 Hz, 1H),
4.62 (dd, J = 5.6, 16.0 Hz, 1H), 6.76 (d, J = 8.8 Hz, 1H), 6.85 (t,
J = 7.6 Hz, 1H), 6.99 (d, J = 8.4 Hz, 1H), 7.02–7.05 (m, 4H), 7.08–
7.17 (m, 5H), 7.23 (d, J = 8.4 Hz, 1H), 7.42–7.45 (m, 3H), 7.49 (d,
J = 8.0 Hz, 1H), 7.67 (ddd, J = 2.8, 5.6, 8.0 Hz, 1H), 7.71 (d,
J = 8.4 Hz, 1H), 8.10 (d, J = 8.4 Hz, 1H), 8.20 (d, J = 8.4 Hz, 1H).
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
3.80 (s, 3H), 6.86 (ddd, J = 1.6, 6.0, 7.6 Hz, 1H), 7.15–7.26 (m, 4H),
7.29–7.34 (m, 3H), 7.36–7.41 (m, 2H), 7.46–7.55 (m, 4H), 7.58 (d,
J = 8.4 Hz, 1H), 7.62 (d, J = 8.8 Hz, 1H), 7.68 (d, J = 8.0 Hz, 1H),
7.74 (d, J = 8.8 Hz, 1H), 7.82 (d, J = 8.8 Hz, 1H), 8.01 (d, J = 8.0 Hz,
1H), 8.14 (d, J = 8.4 Hz, 1H), 8.39 (s, 1H).
4.3. Preparation of axially chiral NHC–Au(I) complex (aR)-4
4.2.9. Complex (aS)-9
This is a known compound.17 1H NMR (400 MHz, CDCl3, TMS) d
3.75 (s, 3H), 4.32 (s, 4H), 6.58 (d, J = 7.2 Hz, 4H), 6.67 (t, J = 8.4 Hz,
1H), 6.73 (d, J = 8.0 Hz, 1H), 6.82 (d, J = 9.2 Hz, 1H), 6.89
Compound 1212f (195 mg, 0.40 mmol) and benzyl chloride
(0.93 mL, 8.0 mmol) were refluxed in 1,4-dioxane (6.0 mL) until
12 was completely consumed as seen by TLC monitoring. When a

2034
J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
Table 2
Axially chiral gold complex catalyzed asymmetric Friedel–Crafts/cyclization reaction of 1,6-enyne 14a with indole derivative 15a in DCE
NHC-Au(I) catalyst (5 mol%)
AgSbF6 (5 mol%)
Ts
N
Ph
+
Ts
N
N
DCE, 25 °C
H
H
N
Ph
14a
15a
16a
Entrya
Catalyst
Time (d)
Yieldb(%)
drc
eed (%)
1
2
3
4
5
6
7
8
(aR)-1
(aS)-2a
(aS)-2b
(aS)-3
(aR)-4
(aS,S)-5
(aS,R)-5
(aS)-6
(aR)-6
(aS)-7
(aS)-8
(aS)-9
(aS)-10
(aS)-11
1.0
1.0
1.0
1.5
2.0
1.5
1.0
1.0
2.0
1.0
2.5
1.0
1.0
1.0
84
87
88
53
70
44
63
89
73
89
42
67
85
82
68:1
(+)33
(+)44
(+)20
(ꢀ)4
6:1
>99:1
25:1
35:1
42:1
(+)38
(ꢀ)11
(+)17
(+)34
(ꢀ)37
(+)46
(+)12
(+)20
(ꢀ)4
42:1
>99:1
>99:1
12:1
36:1
>99:1
30:1
9
10
11
12
13
14
50:1
(ꢀ)10
a
b
c
Reaction conditions: 5 mol % of catalyst; 5 mol % of AgSbF6; 0.1 mmol of 14a; 3.0 equiv of 15a; 1.0 mL of DCE.
Isolated yields.
Determined by 1H NMR spectroscopy.
d
Determined by chiral HPLC using a Chiralpak AD-H column.
white solid precipitated in the reaction system, the resulting sus-
pension was cooled to room temperature and filtered to obtain
the solid, which was then washed with n-hexane three times to
give benzimidazolium salt 13 in almost quantitative yield without
any further purification.
Under an argon atmosphere, to a flame-dried Schlenk tube
equipped with a septum and stirrer bar were added NHC precursor
13 (74 mg, 0.10 mmol), NaOAc (33 mg, 0.40 mmol), and [(Me2-
S)AuCl] (59 mg, 0.20 mmol) followed by the addition of dry CH3CN
(5.0 mL) as the solvent. After refluxing at 85 °C for about 48 h, the
reaction mixture was cooled to room temperature and filtered
through Celite. The volatiles were then removed under reduced
pressure and the residue was purified by a silica gel flash column
chromatography (eluent: petroleum ether/EtOAc, 3/1) to give
complex 4 as a white solid in a 37% yield (Scheme 2).
4.4. Preparation of 1,6-enynes and indole derivatives
4.4.1. Preparation of 1,6-enyne 14i
To a mixture of propargylamine (412 lL, 6.0 mmol) and Et3N
(0.92 mL, 6.6 mmol) in CH2Cl2 (4.0 mL) was added dropwise the
solution of TsCl (1258 mg, 6.6 mmol) in CH2Cl2 (12.0 mL) at 0 °C.
The reaction system was then warmed to room temperature and
stirred for 5 h followed by quenching with 20 mL of water. After
extraction with CH2Cl2 for three times, the combined organic
phases were washed with saturated brine and then dried over
anhydrous Na2SO4. The crude product was concentrated under re-
duced pressure and then purified by silica gel flash column chro-
matography (eluent: petroleum ether/EtOAc, 5/1; containing
minor Et3N) to give 4-methyl-N-(prop-2-ynyl)benzenesulfonamide
as a white solid in an 84% yield. It is a known compound.18 1H NMR
(400 MHz, CDCl3, TMS) d 2.11 (t, J = 2.4 Hz, 1H), 2.43 (s, 3H), 3.83
(dd, J = 6.0, 2.4 Hz, 2H), 4.73 (t, J = 6.0 Hz, 1H), 7.32 (d, J = 8.0 Hz,
2H), 7.78 (d, J = 8.8 Hz, 2H).
Under an argon atmosphere, to a solution of 4-methyl-N-(prop-
2-ynyl)benzenesulfonamide (418 mg, 2.0 mmol), 3-(4-methoxy-
phenyl)-prop-2-en-1-ol (362 mg, 2.2 mmol), and Ph3P (630 mg,
2.4 mmol) in THF (10 mL) was added dropwise DEAD (0.47 mL,
2.4 mmol) at 0 °C. The reaction was warmed to room temperature
and stirred for 24 h. The volatiles were then removed under
reduced pressure and the residue was purified by silica gel flash col-
umn chromatography (eluent: petroleum ether/EtOAc, 10/1) to give
14i as a yellow solid in a 90% yield. Mp 85–87 °C. 1H NMR (300 MHz,
CDCl3, TMS) d 2.05 (t, J = 2.4 Hz, 1H), 2.42 (s, 3H), 3.79 (s, 3H), 3.96
(d, J = 6.6 Hz, 2H), 4.11 (d, J = 1.8 Hz, 2H), 5.92 (dt, J = 15.3, 7.5 Hz,
1H), 6.51 (d, J = 15.3 Hz, 1H), 6.84 (d, J = 8.4 Hz, 2H), 7.28 (t,
J = 9.0 Hz, 4H), 7.76 (d, J = 8.4 Hz, 2H). 13C NMR (75 MHz, CDCl3) d
21.5, 35.7, 48.6, 55.2, 73.7, 76.5, 113.9, 120.4, 127.7, 128.8, 129.4,
4.3.1. Compound (aR)-12
This is a known compound.12f 1H NMR (300 MHz, CDCl3, TMS) d
6.11 (d, J = 7.8 Hz, 2H), 6.50 (t, J = 7.5 Hz, 2H), 6.93–6.99 (m, 2H),
6.99 (s, 2H), 7.43 (d, J = 8.4 Hz, 2H), 7.48–7.56 (m, 6H), 7.63–7.69
(m, 2H), 8.07 (d, J = 8.4 Hz, 4H).
4.3.2. Complex (aR)-4
A colorless solid. Mp 325–327 °C (dec.). 1H NMR (400 MHz,
CDCl3, TMS) d 5.82 (d, J = 15.6 Hz, 2H), 6.22 (d, J = 15.2 Hz, 2H),
6.48 (t, J = 8.0 Hz, 2H), 6.63 (d, J = 8.0 Hz, 2H), 7.00 (t, J = 8.0 Hz,
2H), 7.27–7.36 (m, 8H), 7.47 (d, J = 7.2 Hz, 4H), 7.56–7.60 (m, 2H),
7.65–7.71 (m, 6H), 7.98 (dd, J = 8.0, 5.6 Hz, 4H). IR (KBr)
m 2359,
2342, 1749, 1734, 1698, 1684, 1559, 1534, 1522, 1508, 1489, 1474,
1276, 1261, 764, 749, 689, 684, 669, 651 cmꢀ1. ½a D20
¼ þ60 (c 0.45,
ꢂ
CHCl3). LRMS (MALDI) m/e 1095.5 [M+-Cl]; HRMS (MALDI) calcd
for [C48H34N4197Au-Cl2Au] requires 863.2444, found 863.2429
[M+-Cl2Au].
134.4, 135.9, 143.5, 159.4. IR (KBr)
m 3033, 2957, 2925, 2838,
1607, 1577, 1512, 1495, 1464, 1456, 1442, 1421, 1347, 1305,

J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
2035
Table 3
The scope and limitations of the axially chiral gold complex catalyzed asymmetric Friedel–Crafts/cyclization reaction of 1,6-enynes 14 with indole derivatives 15 in DCE
R1
N
4
R2
NHC-Au(I) cat. (aS)-7 (5 mol%)
3
5
R4
AgSbF6 (5 mol%)
R4
2
R1
N
+
H
6
DCE, 25 °C, 24 h
N1
H
7
R2
R3
N
16
14
15
R3
Entrya
R1
R2
R3, R4
Yieldb(%)
drc
eed(%)
1
2
Bs
Ns
Ph, 14b
Ph, 14c
1-Me, H, 15a
1-Me, H, 15a
16b, 40
16c, 80
66:1
57:1
(+)6
(+)44
iPr
iPr
O
S
3
iPr
Ph, 14d
1-Me, H, 15a
16d, 67
>99:1
(+)2
O
4
5
6
7
8
9
10
11
12
13
14
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
Ts
1-Naph, 14e
Mes, 14f
4-CIC6H4,14g
4-MeC6H4,14h
4-MeOC6H4, 14i
Ph, 14a
Ph, 14a
Ph, 14a
Ph, 14a
Ph, 14a
H, 14j
1-Me, H, 15a
1-Me, H, 15a
1-Me, H, 15a
1-Me, H, 15a
1-Me, H, 15a
H, 2-Me, 15b
1-Bn, 2-Me, 15c
H, 5-Br, 15d
1-Bn, H, 15e
1-Boc, H, 15f
1-Me, H, 15a
16e, 87
16f, 90
16g, 83
16h, 87
16i, 86
16j, 88
16k, 73
16l, 86
16m, 81
16n, 72
Complex
>99:1
>99:1
>99:1
>99:1
>99:1
9:1
(+)62
(+)62
(+)62
(+)60
(+)42
(+)65
(+)56
(+)66
(+)63
(+)54
10:1
13:1
>99:1
>99:1
e
e
—
—
Ts
N
14k
14l
e
e
15
16
14k
14l
1-Me, H, 15a
1-Me, H, 15a
Complex
Complex
—
—
Ts
N
e
e
—
—
a
b
c
Reaction conditions: 5 mol % of (aS)-7; 5 mol % of AgSbF6. 0.1 mmol of 14; 3.0 equiv of 15; 1.0 mL of dry DCE at 25 °C for 24 h.
Isolated yields.
Determined by 1H NMR spectroscopy.
Determined by chiral HPLC.
Not determined.
d
e
1282, 1252, 1175, 1161, 1119, 1095, 1059, 1032, 926, 898, 854, 814,
763, 738, 715, 703, 659, 580, 564, 543 cmꢀ1. LRMS (EI) m/e 355, 200
(65.69%), 199 (20.29%), 198 (100%), 184 (22.53%), HRMS (EI) calcd
for [C20H21NO3S] requires 355.1242, found 355.1246 [M+].
4.5.1. 1-Methyl-3-((4-methylene-1-tosylpyrrolidin-3-yl)
(phenyl)methyl)-1H-indole 16a
This is a known compound.1a 1H NMR (400 MHz, CDCl3, TMS) d
2.43 (s, 3H), 3.31 (dd, J = 8.8, 3.6 Hz, 1H), 3.40–3.47 (m, 2H), 3.74 (s,
3H), 3.83 (d, J = 14.0 Hz, 1H), 3.88 (d, J = 16.0 Hz, 1H), 3.95 (d,
J = 10.4 Hz, 1H), 4.23 (d, J = 1.2 Hz, 1H), 4.73 (d, J = 1.2 Hz, 1H),
6.87 (s, 1H), 7.01 (t, J = 7.2 Hz, 1H), 7.08–7.11 (m, 1H), 7.16–7.25
(m, 8H), 7.33 (d, J = 8.0 Hz, 1H), 7.60 (d, J = 8.0 Hz, 2H),
4.4.2. 1,6-Enynes 14a–14h, 14j–14m and indole derivatives 15a,
15d, and 15f are known compounds and have been synthesized
according to the literature procedures17,19–22
½
a 2D0
ꢂ
¼ ꢀ43 (c 2.0, CHCl3) [(+)46% ee].
4.5. General procedure for NHC–Au(I) complex-catalyzed
asymmetric Friedel–Crafts/cyclization reaction of 1,6-enynes
with indole derivatives and analytical data for the products
4.5.2. 3-{[1-(4-Bromo-benzenesulfonyl)-4-methylene-pyrroli-
din-3-yl]-phenyl-methyl}-1-methyl-1H-indole 16b
A colorless solid. 40% yield. Mp 197–199 °C. 1H NMR (300 MHz,
CDCl3, TMS) d 3.30 (dd, J = 9.3, 3.9 Hz, 1H), 3.45 (dd, J = 18.9, 9.6 Hz,
1H), 3.40–3.50 (m, 1H), 3.73 (s, 3H), 3.85 (s, 2H), 3.94 (d, J = 9.9 Hz,
1H), 4.28 (s, 1H), 4.76 (s, 1H), 6.85 (s, 1H), 7.02–7.13 (m, 2H), 7.18–
7.27 (m, 6H), 7.34 (d, J = 8.1 Hz, 1H), 7.56 (t, J = 9.0 Hz, 4H). 13C
NMR (75 MHz, CDCl3) d 32.8, 45.7, 47.8, 52.2, 53.1, 109.2, 110.4,
116.1, 119.0, 119.4, 121.8, 125.8, 126.3, 127.1, 127.8, 128.1,
A mixture of NHC–Au(I) complex (5 mol %), 1,6-enyne 14a
(0.10 mmol), 1-methyl-1H-indole 15a (0.30 mmol), and AgSbF6
(2.0 mg, 0.0050 mmol) in dry 1,2-dichloroethane (DCE) (1.0 mL)
was stirred at 25 °C until 14a was completely consumed by TLC
monitoring. Then the reaction mixture was quenched by filtering
through Celite and the volatiles were removed under reduced
pressure. The residue was purified by silica gel flash column chroma-
tography (eluent: petroleum ether/EtOAc, 8/1) to give the corre-
sponding product 16a as a white solid.
128.2, 129.1, 132.3, 134.7, 137.0, 143.1, 144.6. IR (KBr)
2928, 2883, 2360, 1574, 1541, 1472, 1457, 1388, 1373, 1348,
1120, 1092, 1032, 1008, 901, 823, 738, 703, 613, 577 cmꢀ1
m 3056,
.

2036
J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
4.5.5. 1-Methyl-3-{[4-methylene-1-(toluene-4-sulfonyl)-
pyrrolidin-3-yl]-naphthalen-1-yl-methyl}-1H-indole 16e
A colorless solid. 87% yield. Mp 186–188 °C. 1H NMR (300 MHz,
CDCl3, TMS) d 2.44 (s, 3H), 3.42 (dd, J = 9.6, 6.9 Hz, 1H), 3.51–3.64
(m, 2H), 3.69 (s, 3H), 3.84 (t, J = 14.7 Hz, 2H), 4.21 (s, 1H), 4.54 (s,
1H), 4.92 (d, J = 9.3 Hz, 1H), 6.85 (s, 1H), 6.95 (dd, J = 7.5, 6.9 Hz,
1H), 7.15 (t, J = 6.6 Hz, 1H), 7.21–7.28 (m, 4H), 7.31–7.45 (m, 4H),
7.63 (dd, J = 7.8, 4.2 Hz, 3H), 7.77–7.80 (m, 1H), 7.90–7.93 (m,
1H). 13C NMR (75 MHz, CDCl3) d 21.5, 22.6, 32.7, 48.2, 52.4, 53.3,
109.2, 109.8, 116.3, 118.8, 119.4, 121.7, 122.9, 124.7, 125.2,
125.8, 126.5, 126.8, 127.3, 127.8, 128.9, 129.7, 132.0, 132.6,
133.7, 137.0, 139.3, 143.6, 145.1. IR (KBr)
m 3048, 2923, 2853,
2359, 2343, 1596, 1541, 1508, 1472, 1458, 1344, 1160, 10995,
793, 777, 738, 663, 587, 548 cmꢀ1. ½a D20
¼ ꢀ95 (c 0.50, CHCl3)
ꢂ
[(+)62% ee]. Chiralcel AD-H, hexane/iPrOH = 70/30, 0.7 mL/min,
230 nm, tmajor = 9.03 min, tminor = 10.31 min. LRMS (ESI) m/e 507.1
[M++H]; HRMS (ESI) calcd for [C32H30N2O2S+Na] requires
529.1920, found 529.1936 [M++Na].
4.5.6. 1-Methyl-3-[[4-methylene-1-(toluene-4-sulfonyl)-pyrr-
olidin-3-yl]-(2,4,6-trimethyl-phenyl)-methyl]-1H-indole 16f
A colorless solid. 90% yield. Mp 225–227 °C. 1H NMR (300 MHz,
CDCl3, TMS) d 1.97 (s, 3H), 2.20 (d, J = 23.4 Hz, 6H), 2.40 (s, 3H),
3.57–3.73 (m, 4H), 3.78 (s, 3H), 3.95 (d, J = 13.5 Hz, 1H), 4.09 (s,
1H), 4.45 (d, J = 10.5 Hz, 1H), 4.70 (s, 1H), 6.57 (s, 1H), 6.77 (s,
2H), 6.88 (d, J = 5.4 Hz, 2H), 7.11–7.16 (m, 1H), 7.23 (t, J = 7.5 Hz,
3H), 7.65 (d, J = 8.4 Hz, 2H). 13C NMR (75 MHz, CDCl3) d 20.6,
21.5, 29.6, 32.8, 41.2, 44.1, 52.4, 54.2, 108.9, 110.6, 115.7, 118.7,
119.9, 121.5, 126.0, 127.76, 127.78, 129.7, 132.4, 135.3, 135.6,
Figure 3. ORTEP drawing of 16l.
½
a 2D0
ꢂ
¼ ꢀ4:0 (c 0.20, CHCl3), ½a D20
¼ ꢀ2:0 (c 1.0, CHCl3) [(+)6% ee].
ꢂ
Chiralcel AD-H, hexane/iPrOH = 70/30, 0.7 mL/min, 230 nm,
tmajor = 9.15 min, tminor = 12.23 min. LRMS (ESI) m/e 521.0 [M++H];
HRMS (ESI) calcd for [C27H26N2O2SBr] requires 521.0893, found
521.0893 [M++H].
137.0, 143.6, 144.1. IR (KBr)
m 2922, 2855, 1613, 1597, 1471,
1424, 1346, 1306, 1180, 1096, 1045, 1013, 815, 738, 664, 591,
4.5.3. 1-Methyl-3-{[4-methylene-1-(4-nitro-benzenesulfonyl)-
pyrrolidin-3-yl]-phenyl-methyl}-1H-indole 16c
549 cmꢀ1. ½a 2D0
¼ ꢀ94 (c 0.80, CHCl3) [(+)62% ee]. Chiralcel AD-H,
ꢂ
hexane/iPrOH = 70/30, 0.7 mL/min, 230 nm, tmajor = 6.36 min,
tminor = 6.86 min. LRMS (ESI) m/e 499.1 [M++H]; HRMS (ESI) calcd
for [C31H34N2O2S+Na] requires 521.2233, found 521.2223 [M++Na].
A yellow solid. 80% yield. Mp 192–194 °C. 1H NMR (400 MHz,
CDCl3, TMS) d 3.33–3.38 (m, 1H), 3.47–3.52 (m, 2H), 3.74 (s, 3H),
3.91–3.94 (m, 3H), 4.33 (d, J = 1.6 Hz, 1H), 4.80 (d, J = 1.2 Hz, 1H),
6.86 (s, 1H), 6.97–7.01 (m, 1H), 7.09–7.12 (m, 1H), 7.16–7.21 (m,
5H), 7.23–7.27 (m, 2H), 7.82–7.85 (m, 2H), 8.21–8.24 (m, 2H). 13C
NMR (100 MHz, CDCl3) d 32.8, 45.8, 47.9, 52.2, 53.0, 109.3, 110.8,
116.0, 119.1, 119.2, 122.0, 124.3, 125.8, 126.4, 127.1, 128.1,
4.5.7. 3-{(4-Chlorophenyl)-[4-methylene-1-(toluene-4-
sulfonyl)-pyrrolidin-3-yl]-methyl}-1-methyl-1H-indole 16g
A colorless solid. 83% yield. Mp 202–204 °C. 1H NMR (400 MHz,
CDCl3, TMS) d 2.23 (s, 3H), 3.34–3.40 (m, 3H), 3.75 (s, 3H), 3.80–
3.93 (m, 3H), 4.23 (s, 1H), 4.76 (s, 1H), 6.86 (s, 1H), 7.00–7.04 (m,
1H), 7.09 (d, J = 8.4 Hz, 2H), 7.13–7.28 (m, 7H), 7.59 (d, J = 8.0 Hz,
2H). 13C NMR (100 MHz, CDCl3) d 32.8, 45.1, 47.8, 52.1, 53.0,
109.3, 110.5, 115.8, 119.0, 119.3, 121.9, 125.8, 127.0, 127.7,
128.3, 129.5, 129.7, 131.8, 132.6, 137.1, 141.9, 143.6, 144.8. IR
128.2, 128.3, 128.6, 137.0, 142.9, 144.3, 150.1. IR (KBr)
m 3058,
2923, 2854, 2360, 2343, 1527, 1505, 1458, 1349, 1166, 1098,
736, 615 cmꢀ1. ½a D20
¼ ꢀ27 (c 0.45, CHCl3) [(+)44% ee]. Chiralcel
ꢂ
AD-H, hexane/iPrOH = 70/30, 0.7 mL/min, 230 nm, tmajor = 12.12 -
min, tminor = 21.89 min. LRMS (ESI) m/e 488.1 [M++H]; HRMS (ESI)
calcd for [C27H25N3O4S+Na] requires 510.1458, found 510.1463
[M++Na].
(KBr)
1473, 1457, 1340, 1161, 1092, 1013, 739, 663, 591, 549 cmꢀ1
¼ ꢀ46 (c 0.35, CHCl3) [(+)62% ee]. Chiralcel AD-H, hex-
m 2922, 1733, 1698, 1684, 1653, 1647, 1558, 1541, 1489,
.
a 2D0
4.5.4. 1-Methyl-3-{[4-methylene-1-(2,4,6-triisopropyl-benzene-
sulfonyl)-pyrrolidin-3-yl]-phenyl-methyl}-1H-indole 16d
½ ꢂ
ane/iPrOH = 70/30,
0.7 mL/min,
230 nm,
tmajor = 10.79 min,
A colorless solid. 67% yield. Mp 194–195 °C. 1H NMR (400 MHz,
CDCl3, TMS) d 1.16 (d, J = 6.4 Hz, 6H), 1.19 (d, J = 6.8 Hz, 6H), 1.23
(d, J = 6.8 Hz, 6H), 2.82–2.93 (m, 1H), 3.41 (dd, J = 10.4, 5.2 Hz,
1H), 3.51 (dd, J = 10.0, 7.2 Hz, 1H), 3.59–3.65 (m, 1H), 3.72 (s,
3H), 3.86 (dt, J = 13.2, 1.6 Hz, 1H), 3.94 (dq, J = 13.6, 2.0 Hz, 1H),
4.09–4.19 (m, 2H), 4.24 (d, J = 10.8 Hz, 1H), 4.28 (dd, J = 4.0,
2.0 Hz, 1H), 4.78 (dd, J = 3.6, 1.6 Hz, 1H), 6.94 (s, 1H), 6.98–7.02
(m, 1H), 7.08–7.24 (m, 7H), 7.28–7.31 (m, 2H), 7.49–7.51 (dt,
J = 8.0, 0.8 Hz, 1H). 13C NMR (75 MHz, CDCl3) d 23.5, 24.6, 24.9,
32.7, 34.1, 45.8, 47.8, 51.4, 109.1, 110.0, 116.7, 118.9, 119.4,
121.7, 123.8, 125.7, 126.2, 127.2, 128.2, 128.3, 130.8, 137.0,
tminor = 13.21 min. LRMS (ESI) m/e 491.1 [M++H]; HRMS (ESI) calcd
for [C28H27N2O2SCl+Na] requires 513.1374, found 513.1366
[M++Na].
4.5.8. 1-Methyl-3-{[4-methylene-1-(toluene-4-sulfonyl)-
pyrrolidin-3-yl]-p-tolyl-methyl}-1H-indole 16h
A colorless solid. 87% yield. Mp 178–180 °C. 1H NMR (400 MHz,
CDCl3, TMS) d 2.23 (s, 3H), 2.43 (s, 3H), 3.27 (dd, J = 9.2, 4.0 Hz, 1H),
3.39–3.46 (m, 2H), 3.73 (s, 3H), 3.85 (s, 2H), 3.92 (d, J = 10.4 Hz,
1H), 4.28 (d, J = 1.2 Hz, 1H), 4.74 (d, J = 0.8 Hz, 1H), 6.85 (s, 1H),
7.00 (dd, J = 12.0, 7.2 Hz, 3H), 7.07 (d, J = 8.0 Hz, 2H), 7.17 (t,
J = 6.8 Hz, 1H), 7.24 (d, J = 8.0 Hz, 3H), 7.34 (d, J = 8.0 Hz, 1H),
7.59 (d, J = 8.0 Hz, 2H). 13C NMR (100 MHz, CDCl3) d 20.9, 21.5,
32.7, 45.2, 47.7, 52.4, 53.1, 109.2, 110.0, 116.6, 118.8, 119.5,
121.6, 125.7, 127.2, 127.7, 127.9, 128.8, 129.7, 132.6, 135.6,
143.6, 145.6, 151.3, 153.0. IR (KBr)
m 2958, 2928, 2868, 1600,
1483, 1465, 1424, 1363, 1316, 1263, 1151, 1134, 1061, 1043,
1031, 899, 883, 765, 703, 675, 670, 588, 562 cmꢀ1. ½a D20
¼ þ2:0 (c
ꢂ
1.0, CHCl3) [(+)2% ee]. Chiralcel AD-H, hexane/iPrOH = 70/30,
0.7 mL/min, 230 nm, tmajor = 6.25 min, tminor = 8.45 min. LRMS
(ESI) m/e 569.2 [M++H]; HRMS (ESI) calcd for [C36H44N2O2S+Na] re-
quires 591.3016, found 591.3021 [M++Na].
137.0, 140.3, 143.5, 145.2. IR (KBr)
2343, 2331, 1541, 1509, 1482, 1473, 1458, 1373, 1344, 1161,
1132, 1118, 1095, 1044, 814, 739, 663, 591, 549 cmꢀ1
m 3048, 2922, 2856, 2360,
.

J. Yang et al. / Tetrahedron: Asymmetry 22 (2011) 2029–2038
2037
½
a 2D0
ꢂ
¼ ꢀ26 (c 0.50, CHCl3) [(+)60% ee]. Chiralcel AD-H, hex-
7.00 (d, J = 2.0 Hz, 1H), 7.10–7.13 (m, 3H), 7.16–7.23 (m, 4H),
7.27 (dd, J = 8.4, 7.6 Hz, 2H), 7.42 (d, J = 1.6 Hz, 1H), 7.59 (d,
J = 8.4 Hz, 2H), 8.26 (s, 1H). 13C NMR (100 MHz, CDCl3) d 21.6,
45.5, 47.7, 52.2, 53.1, 110.3, 112.68, 112.73, 117.5, 121.7, 122.4,
125.1, 126.5, 127.6, 128.1, 128.3, 128.5, 129.8, 132.5, 134.9,
ane/iPrOH = 70/30,
0.7 mL/min,
230 nm,
tmajor = 8.73 min,
tminor = 11.30 min. LRMS (ESI) m/e 471.1 [M++H]; HRMS (ESI) calcd
for [C29H30N2O2S+Na] requires 493.1920, found 493.1923 [M++Na].
4.5.9. 3-{(4-Methoxy-phenyl)-[4-methylene-1-(toluene-4-
sulfonyl)-pyrrolidin-3-yl]-methyl}-1-methyl-1H-indole 16i
A yellow solid. 86% yield. Mp 190–192 °C. 1H NMR (300 MHz,
142.6, 143.8, 144.7. IR (KBr) m 3085, 3065, 2924, 1653, 1647,
1636, 1457, 1339, 1170, 1097, 814, 737, 702, 548 cmꢀ1
.
½
a 2D0
ꢂ
¼ ꢀ6:0 (c 0.25, CHCl3).), ½a D20
¼ ꢀ4:0 (c 1.0, CHCl3) [(+)66%
ꢂ
CDCl3, TMS)
d
2.42 (s, 3H), 3.29 (dd, J = 13.5, 8.4 Hz, 1H),
ee]. Chiralcel AD-H, hexane/iPrOH = 70/30, 0.7 mL/min, 230 nm,
tmajor = 8.56 min, tminor = 9.54 min. LRMS (ESI) m/e 521.0 [M++H];
HRMS (ESI) calcd for [C27H25N2O2SBr+Na] requires 543.0712, found
543.0725 [M++Na].
3.38–3.42 (m, 2H), 3.71 (s, 3H), 3.73 (s, 3H), 3.85 (s, 2H), 3.90 (d,
J = 9.0 Hz, 1H), 4.26 (s, 1H), 4.75 (s, 1H), 6.72 (d, J = 8.7 Hz, 2H),
6.84 (s, 1H), 7.00 (t, J = 7.8 Hz, 1H), 7.08 (d, J = 8.4 Hz, 2H), 7.17
(t, J = 7.5 Hz, 1H), 7.24 (d, J = 5.7 Hz, 3H), 7.32 (d, J = 8.1 Hz, 1H),
7.59 (d, J = 7.8 Hz, 2H). 13C NMR (75 MHz, CDCl3) d 21.5, 32.7,
44.8, 47.9, 52.3, 53.1, 55.1, 109.2, 110.1, 113.4, 116.6, 118.7,
119.5, 121.7, 125.6, 127.1, 127.7, 129.0, 129.6, 132.6, 135.5,
4.5.13. 1-Benzyl-3-{[4-methylene-1-(toluene-4-sulfonyl)-
pyrrolidin-3-yl]-phenyl-methyl}-1H-indole 16m
A colorless solid. 81% yield. Mp 78–80 °C. 1H NMR (400 MHz,
CDCl3, TMS) d 2.40 (s, 3H), 3.31–3.36 (m, 1H), 3.38–3.42 (m, 1H),
3.41 (dd, J = 6.0, 3.6 Hz, 1H), 3.82–3.90 (m, 2H), 3.95 (d, J = 9.6 Hz,
1H), 4.22 (d, J = 1.2 Hz, 1H), 4.73 (d, J = 1.6 Hz, 1H), 5.28 (d,
J = 1.6 Hz, 2H), 6.93 (s, 1H), 6.99–7.21 (m, 11H), 7.27–7.35 (m,
4H), 7.59 (dt, J = 8.4, 2.0 Hz, 2H). 13C NMR (100 MHz, CDCl3) d
21.5, 45.6, 47.8, 49.9, 52.3, 53.0, 109.7, 110.1, 117.1, 119.2, 119.7,
122.0, 125.3, 126.2, 126.5, 127.5, 127.6, 127.7, 128.1, 128.2,
137.0, 143.5, 145.1, 157.8. IR (KBr)
m 3057, 3027, 2926, 2854,
2360, 2343, 1610, 1542, 1509, 1473, 1466, 1459, 1344, 1247,
1161, 1095, 742, 664, 591, 549 cmꢀ1. ½a D20
¼ ꢀ21 (c 0.45, CHCl3)
ꢂ
[(+)42% ee]. Chiralcel AD-H, hexane/iPrOH = 70/30, 0.7 mL/min,
230 nm, tmajor = 11.40 min, tminor = 15.38 min. LRMS (ESI) m/e
487.1 [M++H]; HRMS (ESI) calcd for [C29H30N2O3S+Na] requires
509.1869, found 509.1856 [M++Na].
128.8, 129.7, 132.7, 136.8, 137.5, 143.1, 143.5, 145.0. IR (KBr)
m
4.5.10. 2-Methyl-3-{[4-methylene-1-(toluene-4-sulfonyl)-
pyrrolidin-3-yl]-phenyl-methyl}-1H-indole 16j
3059, 2923, 2854, 2360, 1598, 1495, 1480, 1466, 1453, 1345,
1160, 1094, 766, 741, 663, 589, 549 cmꢀ1. ½a D20
¼ ꢀ41 (c 0.30,
ꢂ
A colorless solid. 88% yield. Mp 112–114 °C. 1H NMR (400 MHz,
CDCl3, TMS) d 2.34 (s, 3H), 2.42 (s, 3H), 3.11 (dd, J = 6.8, 1.2 Hz, 2H),
3.78 (dt, J = 14.0, 2.0 Hz, 2H), 4.02 (dd, J = 14.4, 1.2 Hz, 1H), 4.08 (d,
J = 11.6 Hz, 1H), 4.39 (d, J = 1.6 Hz, 1H), 4.79 (d, J = 1.6 Hz, 1H),
7.01–7.11 (m, 3H), 7.18–7.34 (m, 7H), 7.57 (dd, J = 8.4, 6.4 Hz,
3H), 7.84 (s, 1H). 13C NMR (100 MHz, CDCl3) d 12.2, 21.5, 45.5,
46.0, 52.4, 53.0, 109.9, 110.6, 113.0, 119.0, 119.3, 120.8, 126.0,
126.9, 127.7, 128.1, 128.3, 129.6, 132.0, 132.7, 135.5, 143.1,
CHCl3) [(+)63% ee]. Chiralcel AD-H, hexane/iPrOH = 70/30, 0.7 mL/
min, 230 nm, tmajor = 10.04 min, tminor = 13.18 min. LRMS (ESI) m/e
533.1 [M++H]; HRMS (ESI) calcd for [C34H32N2O2S+Na] requires
555.2077, found 555.2064 [M++Na].
4.5.14. 3-{[4-Methylene-1-(toluene-4-sulfonyl)-pyrrolidin-3-
yl]-phenyl-methyl}-indole-1-carboxylic acid tert-butyl ester
(16n)
143.5, 145.9. IR (KBr)
1558, 1541, 1472, 1458. 1436, 1430, 1339, 1304, 1184, 1160,
1094, 1065, 1045, 1032, 899, 813, 737, 664, 588, 549. cmꢀ1
¼ ꢀ45 (c 0.20, CHCl3) [(+)65% ee]. Chiralcel OD-H, hex-
m 3055, 2922, 2854, 1716, 1697, 1684,
A colorless solid. 72% yield. Mp 90–92 °C. 1H NMR (300 MHz,
CDCl3, TMS) d 1.71 (s, 9H), 2.43 (s, 3H), 3.34–3.39 (m, 1H), 3.43
(d, J = 5.1 Hz, 2H), 3.76–3.87 (m, 2H), 3.96 (d, J = 13.8 Hz, 1H),
4.13 (s, 1H), 4.72 (s, 1H), 7.09–7.29 (m, 10H), 7.48 (s, 1H), 7.63
(d, J = 8.1 Hz, 2H), 8.05 (d, J = 6.6 Hz, 1H). 13C NMR (100 MHz,
CDCl3) d 21.6, 28.2, 29.7, 45.3, 47.7, 52.0, 53.1, 84.0, 110.7, 115.2,
119.7, 121.9, 122.3, 124.6, 126.7, 127.7, 128.26, 128.33, 129.8,
.
½ ꢂ
a 2D0
ane/iPrOH = 70/30,
0.7 mL/min,
230 nm,
tminor = 10.76 min
tmajor = 13.14 min,. LRMS (ESI) m/e 457.1 [M++H]; HRMS (ESI) calcd
for [C28H29N2O2S] requires 457.1944, found 457.1943 [M++H].
4.5.11. 1-Benzyl-2-methyl-3-{[4-methylene-1-(toluene-4-
sulfonyl)-pyrrolidin-3-yl]-phenyl-methyl}-1H-indole 16k
A colorless solid. 73% yield. Mp 88–90 °C. 1H NMR (400 MHz,
CDCl3, TMS) d 2.27 (s, 3H), 2.38 (s, 3H), 3.05 (dd, J = 10.0, 5.6 Hz,
1H), 3.17 (dd, J = 10.0, 6.8 Hz, 1H), 3.84 (dt, J = 14.0, 2.0 Hz, 2H),
3.97 (dd, J = 14.0, 1.6 Hz, 1H), 4.11 (d, J = 11.2 Hz, 1H), 4.44 (dd,
J = 4.0, 2.0 Hz, 1H), 4.81 (dd, J = 4.0, 2.0 Hz, 1H), 5.28 (d, J = 8.4 Hz,
2H), 6.91 (d, J = 6.8 Hz, 2H), 7.02–7.35 (m, 13H), 7.55 (dt, J = 8.0,
2.0 Hz, 2H), 7.61 (dd, J = 7.2, 0.8 Hz, 1H). 13C NMR (100 MHz, CDCl3)
d 10.6, 21.5, 45.7, 45.9, 46.5, 52.5, 53.1, 109.4, 109.9, 113.3, 119.2,
119.3, 120.9, 125.8, 126.0, 126.2, 127.3, 127.7, 128.1, 128.3, 128.8,
132.7, 141.6, 143.6, 144.3. IR (KBr)
1474, 1453, 1371, 1350, 1309, 1256, 1215, 1162, 1121, 1070,
1050, 1032, 1015, 815, 767, 762, 746, 663, 590, 549 cmꢀ1
¼ ꢀ58 (c 0.50, CHCl3) [(+)54% ee]. Chiralcel IC-H, hex-
m 2956, 2926, 2855, 1732,
.
½ ꢂ
a 2D0
ane/iPrOH = 60/40,
0.7 mL/min,
230 nm,
tminor = 24.11 min
tmajor = 37.90 min. LRMS (ESI) m/e 565.0 [M++Na]; HRMS (ESI) calcd
for [C32H34N2O4S+Na] requires 565.2132, found 565.2118 [M++Na].
Acknowledgements
We thank the Shanghai Municipal Committee of Science and
Technology (08dj1400100–2), National Basic Research Program of
China (973)-2010CB833302, the Fundamental Research Funds for
the Central Universities, the National Natural Science Foundation
of China (21072206, 20472096, 20902019, 20872162, 20672127,
20821002, 20732008 and 20702059) and Professor Jie Sun for per-
forming X-ray diffraction.
129.6, 132.8, 133.7, 136.9, 137.7, 143.1, 143.4, 146.0. IR (KBr)
m
3085, 3059, 3027, 2924, 2855, 2360, 2343, 1655, 1597, 1560,
1541, 1508, 1496, 1466, 1453, 1412, 1346, 1162, 1095, 739, 699,
664, 589, 549. cmꢀ1. ½a D20
¼ ꢀ21 (c 0.15, CHCl3) [(+)56% ee]. Chiral-
ꢂ
cel AD-H, hexane/iPrOH = 70/30, 0.7 mL/min, 230 nm, tmajor = 8.05 -
min, tminor = 10.11 min. LRMS (ESI) m/e 547.2 [M++H]; HRMS (ESI)
calcd for [C35H35N2O2S] requires 547.2414, found 547.2394 [M++H].
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15. The crystal data for 4 have been deposited in CCDC with number 831588.
Empirical Formula: C49H36Au2Cl4N4; Formula Weight: 1216.55; Crystal Color,
Habit: colorless, Crystal Dimensions: 0.157 ꢁ 0.086 ꢁ 0.071 mm; Crystal
System: Monoclinic; Lattice Parameters: a = 13.578(7)Å, b = 11.721(6)Å,
c = 14.055(7)Å,
group: P2(1); Z = 2; Dcalc = 1.870 g/cm3; F000 = 1168; Final
[I >2 (I)]: R1 = 0.0408; wR2 = 0.0834.
16. The crystal data for 16l have been deposited in CCDC with number 844605.
Empirical Formula: 27H25BrN2O2S; Formula Weight: 521.46; Crystal
a
= 90°, b = 105.038(8)°,
c
= 90°, V = 2160.2(19)Å3; Space
induces
R
7. Recently an alternative approach which employs chiral counter anions has
r
4c
become very attractive in conducting asymmetric gold catalysis, see Refs.
and: Hashmi, A. S. K. Nature 2007, 449, 292–293.
C
8. (a) For selected books and reviews on NHC ligands, see: N-Heterocyclic Carbenes
in Synthesis; Nolan, S. P., Ed.; Wiley-VCH: Weinheim, Germany, 2006; (b)
Glorius, F. N-Heterocyclic Carbenes in Transition Metal Catalysis; Berlin: Springer,
2007; (c) Bourissou, D.; Guerret, O.; Gabbai, F. P.; Bertrand, G. Chem. Rev. 2000,
100, 39–91; (d) Herrmann, W. A. Angew. Chem., Int. Ed. 2002, 41, 1290–1309; (e)
Perry, M. C.; Burgess, K. Tetrahedron: Asymmetry 2003, 14, 951–961; (f) Kirmse,
W. Angew. Chem., Int. Ed. 2004, 43, 1767–1769; (g) Cesar, V.; Bellemin-
Laponnaz, S.; Gade, L. H. Chem. Soc. Rev. 2004, 33, 619–636; (h) Douthwaite, R.
E. Coord. Chem. Rev. 2007, 251, 702–717; (i) Kühl, O. Chem. Soc. Rev. 2007, 36,
592–607; (j) Kantchev, E. A. B.; O’Brien, C. J.; Organ, M. G. Angew. Chem., Int. Ed.
2007, 46, 2768–2813; (k) Diez-Gonzalez, S.; Marion, N.; Nolan, S. P. Chem. Rev.
2009, 109, 3612–3676.
Color, Habit: colorless, Crystal Dimensions: 0.25 ꢁ 0.15 ꢁ 0.10 mm; Crystal
System: Triclinic; Lattice Parameters: a = 9.3548(13)Å, b = 12.6226(17)Å,
c = 20.103(3)Å,
Space group: P-1; Z = 4; Dcalc = 1.481 g/cm3; F000 = 1072; Final
[I >2 (I)] R1 = 0.0844, wR2 = 0.2445.
a = 80.248(3)°, b = 89.184(3)°, c
= 89.857(3)°, V = 2339.2(5)Å3;
R
indices
r
17. Wang, W. F.; Yang, J.; Wang, F. J.; Shi, M. Organometallics 2011, 30, 3859–3869.
18. Brummond, K. M.; Chen, H. F.; Sill, P.; You, L. F. J. Am. Chem. Soc. 2002, 124,
15186–15187.
19. Sylvester, K. T.; Chirik, P. J. J. Am. Chem. Soc. 2009, 131, 8772–8774.
20. Mori, M.; Watanuki, S. J. Chem. Soc., Chem. Commun. 1992, 8, 1082–1084.
21. Yan, G. B.; Kuang, C. X.; Zhang, Y.; Wang, J. B. Org. Lett. 2010, 12, 1052–1055.
22. García-Rubia, A.; Urones, B.; Arrayás, R. G.; Carretero, J. C. Chem. Eur. J. 2010, 16,
9676–9685.
9. (a) Jafarpour, L.; Nolan, S. P. Adv. Organomet. Chem. 2000, 46, 181–222; (b)
Weskamp, T.; Bohm, V. P. W.; Herrmann, W. A. J. Organomet. Chem. 2000, 600,