The application of chiral phosphine-Schiff base type ligands in silver(I)-catalyzed asymmetric vinylogous Mannich reaction of aldimines with trimethylsiloxyfuran

Article abstract of DOI:10.1016/j.tet.2009.05.080

Catalytic asymmetric vinylogous Mannich (AVM) reactions of readily available aldimines with trimethylsiloxyfuran in the presence of catalytic amount of AgOAc and chiral phosphine-Schiff base type ligands are described, affording the corresponding products in up to 91% yield, anti/syn >99:1 and 81% ee.

Full text of DOI:10.1016/j.tet.2009.05.080

Tetrahedron 65 (2009) 6001–6007
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Tetrahedron
journal homepage: www.elsevier.com/locate/tet
The application of chiral phosphine-Schiff base type ligands in silver(I)-catalyzed
asymmetric vinylogous Mannich reaction of aldimines with trimethylsiloxyfuran
,b,
Zhi-Liang Yuan a, Jia-Jun Jiang a, Min Shi a
*
a Laboratory for Advanced Materials and Institute of Fine Chemicals, School of Chemistry and Molecular Engineering, East China University of Science and Technology,
130 Mei Long Lu, Shanghai 200237, China
b State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences, 354 Fenglin Lu, Shanghai 200032 China
a r t i c l e i n f o
a b s t r a c t
Article history:
Catalytic asymmetric vinylogous Mannich (AVM) reactions of readily available aldimines with trime-
thylsiloxyfuran in the presence of catalytic amount of AgOAc and chiral phosphine-Schiff base type li-
gands are described, affording the corresponding products in up to 91% yield, anti/syn >99:1 and 81% ee.
Ó 2009 Elsevier Ltd. All rights reserved.
Received 22 April 2009
Received in revised form 27 May 2009
Accepted 27 May 2009
Available online 3 June 2009
1. Introduction
reported an AVM reaction which relied on the use of N-(2-thienyl)-
sulfonylimines as substrates.5 A bifunctional thiourea catalyst
The reaction of silyloxyfuran with imines, nitrones or iminium
ions has already been reported by several research groups.1 Such
Mannich-type reaction is one of the most important methods for
promoted AVM reaction was developed by Chen et al. in 2007.6 Very
recently, a chiral Brønsted acid-catalyzed approach to this AVM
reaction was achieved by Akiyama et al.7 and Schneider’s group,8
respectively. Aside from these pioneering investigations, the ex-
ploration of new catalytic systems in AVM reaction is still a main
challenge at the present stage.
Previous research has disclosed that aldimine substrates having
2-methyloxyphenyl group is essential to give the AVM product in
high yield and good enantioselectivity in this catalytic system
through a bidentate chelation with the chiral metal complex
(Scheme 1).4 Herein, we wish to report a novel and efficient sil-
ver(I)-catalyzed AVM procedure, which relies on the use of chiral
phosphine-Schiff base type ligands developed in our group. Fur-
thermore, this paper will reveal that the AVM reaction of aldimines
1, which do not possess 2-methyloxyphenyl group, with siloxyfuran
2 can proceed smoothly to give the corresponding products 3 in
good yields and moderate to good enantioselectivities in the
presence of phosphine-Schiff base type ligand and AgOAc under
mild reaction conditions (Scheme 1).
the synthesis of b-amino carbonyls and their derivatives, which can
be found in a large number of biologically active natural products.2
Recently, several elegant catalytic systems have been applied in
asymmetric vinylogous Mannich (AVM) reactions. For example,
Martin and Lopez reported the first catalytic asymmetric addition
of trialkylsilyloxyfurans to aldimines in 1999.3 Later, Hoveyda and
Snapper have developed a silver(I)-based catalyst, leading to the
product of AVM reaction in excellent diastereo- and enantiose-
lectivity.4 In particular, the use of 2-methyloxyphenyl group as
aldimine substituent was essential for achieving good enantiose-
lectivities in AVM reaction (Scheme 1). Moreover, Carretero et al.
R
H
N
MeO
N
O
MeO
HN
R
PPh2
OMe
5 mol%
5 mol% AgOAc
N
R
+
2. Results and discussion
OTMS
O
O
O
We initially utilized a moderate Lewis acid AgOAc (10 mol %)9
combined with chiral phosphine-Schiff base type ligands L1–L11
(11 mol %) prepared from the reaction of salicylaldehyde as well as
their analogs with (R)-(ꢀ)-2-(diphenylphosphino)-1,10-binaphthyl-
20-amine10 (Fig. 1) as the catalysts and the AVM reaction of readily
available aldimine 1a (0.2 mmol) with siloxyfuran 2 (0.36 mmol) as
a model reaction in tetrahydrofuran (THF) containing 0.36 mol of
iPrOH (1.8 equiv) to develop the optimal reaction conditions and
the results of these experiments are summarized in Table 1. It was
R = aryl
up to 94% yield
>98% de
up to 98% ee
Scheme 1. Previous research in AVM reaction and our approach.
* Corresponding author.
E-mail address: mshi@mail.sioc.ac.cn (M. Shi).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.05.080

6002
Z.-L. Yuan et al. / Tetrahedron 65 (2009) 6001–6007
R2
R5
R1
R4
R2
examined, chiral phosphine-Schiff base ligand L6 possessing two
electron-withdrawing groups at 2- and 3-positions of benzene ring
gave the best result, affording 3a in 80% yield and 70% ee (dr¼99:1)
(Table 1, entry 6).
R1
R3
N
N
HO
PPh2
With the best chiral phosphine-Schiff base ligand being identi-
fied, we next carried out silver(I)-L6 catalyzed AVM reaction of 1a
with 2 in different solvents with a variety of silver(I) salts. The re-
sults are outlined in Table 2. When the reaction was carried out in
CH2Cl2 and toluene, 3a was obtained in 87% and 85% yield as well as
66% and 67% ee, respectively (Table 2, entries 2 and 3). Solvents
such as Et2O, CH3CN, and 1,4-dioxane are not suitable to this re-
action, providing 3a in lower yields and ee’s even raising the re-
action temperature to ꢀ20 ꢁC (Table 2, entries 1, 4, and 5).
Therefore, the best conditions are to carry out the reaction in THF at
ꢀ78 ꢁC to room temperature for 24 h. The decrease in yields, dia-
stereoselectivities (from 60:40 to 75:25), and enantioselectivities
was also observed when other silver(I) salts such as AgOTf, AgOTFA,
and AgClO4 were applied instead of AgOAc in this reaction (Table 2,
entries 6–8).
PPh2
L3: R1 = H, R2 = H, R3 = H, R4 = H, R5 = H
L4: R1 = Cl, R2 = H, R3 = Cl, R4 = H, R5 = H
L5: R1 = Cl, R2 = H, R3 = H, R4 = H, R5 = Cl
L6: R1 = Cl, R2 = Cl, R3 = H, R4 = H, R5 = H
L7: R1 = F, R2 = H, R3 = H, R4 = H, R5 = H
L8: R1 = Br, R2 = H, R3 = H, R4 = H, R5 = H
L9: R1 = CF3, R2 = H, R3 = H, R4 = H, R5 = H
L10: R1 = OMe, R2 = H, R3 = OMe, R4 = H,
L1: R1 = OMe, R2 = H
L2: R1 = H, R2 = Me
R
5 = H
L11: R1 = OBn, R2 = tBu, R3 = H, R4 = tBu,
5 = H
R
Figure 1. Chiral phosphine-Schiff base type ligands L1–L12.
Table 1
Table 2
Optimization of chiral ligands for the AVM reaction of aldimine 1a and siloxyfuran 2
Effect of solvents and silver salts on the AVM reaction of aldimine 1a and
siloxyfuran 2
Ph
HN
Ph
AgOAc (10 mol %),
Ligand (11 mol %)
Ph
N
HN
Silver salts (10 mol %),
S
Ph
+
+
Ph
R
N
L6 (11 mol %)
S
1.8 equiv iPrOH, THF,
OTMS
O
Ph
Ph
R
O
OTMS 1.8 equiv iPrOH, THF,
_78 °C for 6 h, then warm
to rt naturally for overnight
_78 °C for 6 h, then warm
to rt naturally for overnight
O
Ph
3a
O
3a
1a
2
O
1a
2
O
Entrya
Ligand
Yieldb (%)
dr (anti/syn)c
eed (%)
Absolute
Entrya Solvent
Silver
salt
Yieldb (%) dr (anti/syn)c eed (%) Absolute
Configuratione
3a
3a
3a
Configuratione
3a
3a
3a
1
2
3
4
5
6
7
8
L1
L2
L3
L4
L5
L6
L7
L8
L9
L10
L11
53
50
73
70
69
80
81
78
77
75
73
99:1
99:1
99:1
99:1
99:1
99:1
99:1
99:1
99:1
99:1
99:1
35
33
23
65
17
70
63
70
70
60
8
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
1
2
3
4
5f
6
7
8
Et2O
Toluene AgOAc
CH2CI2
CH3CN
Dioxane AgOAc
THF
THF
THF
AgOAc
50
87
85
21
36
38
99:1
99:1
99:1
90:10
99:1
75:25
60:40
65:35
62
66
67
66
43
38
30
37
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
AgOAc
AgOAc
AgOTf
AgOTFA 30
AgCIO4 37
9
10
11
a
Reaction conditions: 1a (0.2 mmol), 2 (0.36 mmol), iPrOH (0.36 mmol), silver
salt (10 mol %), L6 (11 mol %), solvent (1.0 mL), and the reaction was carried out at
ꢀ78 ꢁC to rt for 24 h.
a
i
Reaction conditions: 1a (0.2 mmol), 2 (0.36 mmol), PrOH (0.36 mmol), AgOAc
(10 mol %), ligand (11 mol %), THF (1.0 mL), and the reaction was carried out at
ꢀ78 ꢁC to rt for 24 h.
b
Isolated yield after column chromatography.
c
Determined by analysis of 300 MHz 1H NMR spectra.
d
b
Determined by chiral HPLC analysis; see Supplementary data for the details.
Isolated yield after column chromatography.
e
c
Determined by analysis of 300 MHz 1H NMR spectra.
Determined by the X-ray diffraction.
The reaction was carried out at ꢀ20 ꢁC to rt for 24 h.
f
d
Determined by chiral HPLC analysis; see Supplementary data for the details.
Determined by the X-ray diffraction.
e
Previous studies have revealed that additives, even small
amounts of simple achiral compounds, often played an important
role in the enhancement of the reactivity and enantioselectivity.8,12
The optimization studies on the effects of different additives were
performed and the results of these experiments are summarized in
Table 3. When the reaction was carried out without any additive,
the desired product 3a was obtained in 49% yield and 51% ee after
stirring for 48 h from ꢀ78 ꢁC to room temperature (Table 3, entry
1).13 Adding EtOH, tBuOH, and 1,2-cyclohexanediol into the reaction
system afforded 3a in higher yields and enantioselectivities under
identical conditions (Table 3, entries 2–4). We also examined
(ꢀ)-menthol, 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), which is
known to accelerate the reaction rate and enantioselectivity in
some cases,14 CF3CH2OH, diphenylmethanol, and triphenylmetha-
nol in this AVM reaction and found that similar results were ach-
ieved (Table 3, entries 5–9). Gratifyingly, when phenylmethanol
(BnOH) was used as an additive, the desired product 3a was
attained in 85% yield and 79% ee (Table 3, entry 10). Therefore,
various phenylmethanol derivatives combined with AgOAc and li-
gand L6 were screened for the reaction. However, it was found that
found that the corresponding AVM product 3a was obtained in 53%
yield and 35% ee as anti-configuration as the major diastereomer
(dr¼99:1) in the presence of L1 (Table 1, entry 1). Using L2 as a li-
gand11 combined with AgOAc afforded 3a in 50% yield and 33% ee
(dr¼99:1) (Table 1, entry 2). After investigating the phosphine-
Schiff base type ligand L3, which do not have a phenolic hydroxy
group, we found that 3a was produced in 73% yield and 23% ee
(dr¼99:1), indicating that this type of phosphine-Schiff base li-
gands has higher catalytic ability (Table 1, entry 3). Then, it was
found that chiral phosphine-Schiff base ligands L4–L11 having
electron-withdrawing group or electron-donating group at 2-po-
sition of benzene ring gave the better results (Fig.1) (Table 1, entries
4–10). As for the phosphine-Schiff base ligand L5 having a 2,6-di-
substituted benzene ring, product 3a was produced in 69% yield
and only 17% ee (dr¼99:1) (Table 1, entry 5). As for the sterically
bulky chiral phosphine-Schiff base ligand L11 bearing electron-
donating 3,5-di-tert-butyl groups on the benzene ring, the product
3a was obtained in 73% yield and only 8% ee (dr¼99:1) under
identical conditions (Table 1, entry 11). Among the ligands

Z.-L. Yuan et al. / Tetrahedron 65 (2009) 6001–6007
6003
(4-nitrophenyl)methanol, (4-methoxyphenyl)methanol, and pyr-
idin-2-ylmethanol are less effective in both of the yield and ee than
those of phenylmethanol under identical conditions (Table 3, en-
tries 11–13). Silica gel could also accelerate the reaction rate, but
did not improve the enantioselectivity of 3a (Table 3, entry 14).
NaBArF [sodium tetrakis(3,5-bistrifluoromethylphenylborate)],
which has been successfully used in several asymmetric catalysis,15
was examined in this reaction as an additive, producing 3a in 81%
yield and 77% ee (Table 3, entry 15).
was determined as (R,S)-configuration by X-ray diffraction of 3e
containing a bromine atom on the benzene ring.16 The ORTEP
drawing of 3e is shown in Figure 2 and the CIF data of 3e are pre-
sented in Supplementary data.17
Table 4
Scope and limitations of AVM reaction of aldimine 1 and siloxyfuran 2
Ar1
Ar1
AgOAc (10 mol %),
HN
N
L6 (11 mol %)
S
Ar2
+
R
OTMS BnOH (1.8 equiv), THF,
Ar2
O
Table 3
O
_78 °C for 6 h, then warm
Optimization of reaction conditions of aldimine 1a and siloxyfuran 2
1
2
3
O
to rt naturally for overnight
Ph
HN
AgOAc (10 mol %),
Ph
Entrya Aldimine 1 (Ar1/Ar2)
Yieldb dr
(%)
eed (%) Absolute
N
L6 (11 mol %)
S
+
Ph
(anti/syn)c Configuratione
R
OTMS
O
additives (1.8 equiv), THF,
_78 °C for 6 h, then warm
to rt naturally for overnight
Ph
O
3a
3
3
3
1a
2
O
1
2
3
4
5
6
7
8
1b (4-NO2C6H4/C6H5)
1c (4-MeOC6H4/C6H5)
1d (3-CF3C6H4/C6H5)
1e (4-BrC6H4/4-BrC6H4)
1f (4-BrC6H4/2-CF3C6H4)
3b, 51 99:1
3c, 56 99:1
3d, 90 99:1
3e, 78 99:1
3f, 85 99:1
38
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
62
65
65e
55
80
81
59
73
75
Entrya Additive
Time Yieldb dr
eed (%) Absolute
Configuratione
(h)
(%)
(anti/syn)c
3a
3a
3a
1g (4-BrC6H4/2,4-(MeO)2C6H3) 3g, 81 75:25
1
2
3
4
5
6
7
8
d
48
24
24
24
24
24
24
24
24
24
24
49
77
79
73
67
66
75
81
50
85
35
95:5
95:5
99:1
99:1
99:1
99:1
99:1
99:1
95:5
99:1
95:5
51
59
65
71
69
66
75
65
65
79
63
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
R,S
1h (C6H5/2,4-CI2C6H3)
1i (C6H5/4-NO2C6H4)
1h (C6H5/2,4-CI2C6H3)
1h (C6H5/2,4-CI2C6H3)
3h, 80 99:1
3i, 91 99:1
3h, 83 99:1
3h, 85 99:1
EtOH
tBuOH
9f
10g
1,2-Cyclohexanediol
(ꢀ)-Menthol
a
Reaction conditions: 1 (0.2 mmol), 2 (0.36 mmol), BnOH (0.36 mmol), AgOAc
HFIP
(10 mol %), L6 (11 mol %), THF (1.0 mL), and the reaction was carried out at ꢀ78 ꢁC to
CF3CH2OH
rt for 24 h.
Diphenylmethanol
Triphenylmethanol
Phenylmethanol
(4-Nitrophenyl)-
methanol
b
Isolated yield after column chromatography.
9
10
11
c
Determined by analysis of 300 MHz 1H NMR spectra.
d
Determined by chiral HPLC analysis; see Supplementary data for the details.
The absolute configuration was determined by X-ray crystallographic analysis.
Ligand L8 was used under optimized conditions instead of L6.
Ligand L9 was used under optimized conditions instead of L6.
e
f
12
(4-Methoxyphenyl)-
methanol
24
61
99:1
70
R,S
g
13
Pyridin-2-yl-methanol 48
25
85
81
90:10
99:1
99:1
53
71
77
R,S
R,S
R,S
14f
15g
Silica gel
NaBArF
8
24
a
Reaction conditions: 1a (0.2 mmol),
2 (0.36 mmol), additives (0.36 mmol),
AgOAc (10 mol %), L6 (11 mol %), THF (1.0 mL), and the reaction was carried out at
ꢀ78 ꢁC to rt for 24 h.
b
Isolated yield after column chromatography.
c
Determined by analysis of 300 MHz 1H NMR spectra.
d
Determined by chiral HPLC analysis; see Supplementary data for the details.
Determined by the X-ray diffraction.
The reaction was carried out with 50 mg of silica gel.
The reaction was carried out with 11 mol % of NaBArF.
e
f
g
Under these optimum conditions, that is, use of 10 mol % of
AgOAc, 11 mol % of chiral ligand L6, and 1.8 equiv of phenyl-
methanol (BnOH) as the additive, we next examined the generality
of this reaction with various aldimines 1, which do not possess 2-
methyloxyphenyl group, with siloxyfuran 2 and the results are
summarized in Table 4. Aldimines 1b having a 4-nitro substituent
on the phenyl ring of Ar1 gave the corresponding AVM product 3b
in 51% yield and 38% ee (Table 4, entry 1). In most cases, the cor-
responding AVM adducts 3c–i were formed in good yields and good
diastereoselectivities as well as moderate to good enantioselectiv-
ities (Table 4, entries 2–8). When ligands L8 and L9 were used in
this reaction under the optimized conditions, the achieved enan-
tiomeric excesses of adduct 3h were lower than that of L6 (Table 4,
entries 7, 9, and 10). Only using aldimine 1g having 2,4-dimethoxy
group on the benzene ring of Ar2 afforded 3g in 75:25 diaster-
eoselectivity, presumably due to the electronic effect (Table 4, entry 6).
The highest ee was achieved using aldimine 1h having 2,4-dichloro
groups on the benzene ring of Ar2 to give the adduct 3h in 81% ee
and 80% yield (dr¼99:1) (Table 4, entry 8). Their structures were
determined by 1H and 13C NMR spectroscopy and HRMS or mi-
croanalyses, and the enantiomeric excesses were analyzed by chiral
HPLC (see Supplementary data). The absolute configuration of 3
Figure 2. ORTEP drawing of 3e.
Then we applied our newly developed catalytic system into the
previously reported AVM reaction, which used the substrate bear-
ing an o-anisidine N-aryl group.4 The adduct 3j was obtained in 58%
yield and 63% ee, less effective than the catalytic system developed
by Hoveyda et al. (Scheme 2).

6004
Z.-L. Yuan et al. / Tetrahedron 65 (2009) 6001–6007
out, which were filtered to give the corresponding phosphine-salen
type ligands and phosphine-Schiff base type ligands L1–L11 as yellow
MeO
MeO
solids.
HN
AgOAc (10 mol %),
L6 (11 mol %)
S
N
+
3.2.1. (R,E)-2-((20-(Diphenylphosphino)-1,10-binaphthyl-2-
ylimino)methyl)-5-methoxyphenol (L1)
R
OTMS
O
BnOH (1.8 equiv), THF,
_78 °C for 6 h, then warm
to rt naturally for overnight
O
Ph
A yellow solid; this is a known compound.11 1H NMR (CDCl3, TMS,
1j
2
O
3j
300 MHz):
d
3.74 (s, 3H, CH3), 6.21 (s, 1H, ArH), 6.34 (d, J¼8.4 Hz, 1H,
58% yield
>98% de
63% ee
ArH), 6.89–7.28 (m,12H, ArH), 7.38–7.51 (m, 4H, ArH), 7.91–7.95 (m, 4H,
ArH), 8.05 (d, J¼8.7 Hz, 1H, ArH), 8.21 (s, 1H, CH), 12.30 (s, 1H, OH). 31P
20
NMR (CDCl3, 121 MHz, 85% H3PO4):
d
ꢀ17.39. [
a
]
D
þ136 (c 0.35, CHCl3).
Scheme 2. AVM reaction of the substrate that bears an o-anisidine N-aryl group.
3.2.2. (R,E)-2-((20-(Diphenylphosphino)-1,10-binaphthyl-2-
ylimino)methyl)-4-methylphenol (L2)
Since N-diphenylphosphinoyl group could be easily removed
under acidic conditions,19 we next applied our catalytic system into
the AVM reaction of the N-diphenylphosphinoylimine 1k with
siloxyfuran 2 under the optimized reaction conditions. It was found
that this AVM reaction could also give the corresponding adduct 3k
in 55% yield with moderate enantio- and diastereoselectivity (43%
ee and 75:25 dr, Scheme 3).
A yellow solid; this is a known compound.11 1H NMR (CDCl3,
TMS, 300 MHz):
d
2.23 (s, 3H, CH3), 6.68 (d, J¼8.4 Hz, 1H, ArH),
6.82–7.52 (m, 20H, ArH), 7.94–7.96 (m, 3H, ArH), 8.06 (d, J¼9 Hz,1H,
Ar), 8.24 (s,1H, CH),11.55 (s,1H, OH). 31P NMR (CDCl3,121 MHz, 85%
20
H3PO4):
d
ꢀ17.40. [
a
]
D
þ178 (c 0.25, CHCl3).
P(O)Ph2
HN
R
P(O)Ph2
AgOAc (10 mol %),
N
L6 (11 mol %)
S
OTMS
BnOH (1.8 equiv), THF,
_78 °C for 6 h, then warm
to rt naturally for overnight
O
+
O
Cl
Cl
2
O
1k
3k
55% yield
75/25 dr
43% ee
Scheme 3. AVM reaction of the N-diphenylphosphinoylimine 1k and siloxyfuran 2.
In summary, we have developed a new catalytic AVM reaction
system applicable to aldimines, which do not possess 2-methyloxy-
phenyl group and siloxyfuran using a chiral phosphine-Schiff base
ligand/AgOAc/BnOH combination.18 The catalytic system reported
here afforded AVM product 3 in up to 91% yield and 81% ee. The
addition of phenylmethanol (BnOH) is important to achieve better
yield and diastereoselectivity as well as enantioselectivity. Current
efforts are in progress to extend this chiral phosphine-Schiff base
ligand/AgOAc/BnOH combination to other catalytic enantioselective
reactions in our laboratory.
3.2.3. (R,E)-N-Benzylidene-20-(diphenylphosphino)-1,10-
binaphthyl-2-amine (L3)
A yellow solid; this is a known compound.11 1H NMR (CDCl3,
TMS, 300 MHz):
d
6.67 (d, J¼8.1 Hz, 1H, ArH), 6.93–7.56 (m, 21H,
ArH), 7.74 (d, J¼7.8 Hz, 1H, ArH), 7.80 (d, J¼8.7 Hz, 1H, ArH), 7.87–
7.90 (m, 3H, ArH), 8.16 (s, 1H, CH). 31P NMR (CDCl3, 121 MHz, 85%
20
H3PO4):
d
ꢀ17.70. [
a]
þ191 (c 0.25, CHCl3).
D
3.2.4. (R,E)-N-(2,4-Dichlorobenzylidene)-20-(diphenylphosphino)-
1,10-binaphthyl-2-amine (L4)
A yellow solid; this is a known compound.11 1H NMR (CDCl3,
TMS, 300 MHz): d 6.90–7.53 (m, 20H, ArH), 7.72–7.91 (m, 4H, ArH),
3. Experimental section
3.1. General remarks
8.02 (d, J¼8.7 Hz, 1H, ArH), 8.52 (s, 1H, CH). 31P NMR (CDCl3,
20
121 MHz, 85% H3PO4):
d
ꢀ12.89. [
a]
þ335 (c 0.25, CHCl3).
D
1H and 13C NMR spectra were recorded on a Bruker AM-300
spectrometer for solution in CDCl3 with tetramethylsilane (TMS) as
an internal standard; J-values are in hertz. Mass spectra were
recorded by EI methods, and HRMS was measured on a Finnigan
MAþ mass spectrometer. THF and toluene were distilled from so-
dium (Na) under argon (Ar) atmosphere. CH3CN and 1,2-dichloro-
methane were distilled from CaH2 under argon (Ar) atmosphere.
Commercially obtained reagents were used without further puri-
fication. All reactions were monitored by TLC with Huanghai GF254
silica gel coated plates. Flash column chromatography was carried
out using 300–400 mesh silica gel at increased pressure.
3.2.5. (R,E)-N-(2,6-Dichlorobenzylidene)-20-(diphenylphosphino)-
1,10-binaphthyl-2-amine (L5)
A yellow solid; this is a known compound.11 1H NMR (CDCl3,
TMS, 300 MHz):
d 6.92–7.06 (m, 2H, ArH), 7.09–7.21 (m, 10H, ArH),
7.22–7.48 (m, 9H, ArH), 7.75–7.92 (m, 3H, ArH), 8.03 (d, J¼9.0 Hz,
1H, ArH), 8.22 (s, 1H, CH). 31P NMR (CDCl3, 121 MHz, 85% H3PO4):
20
d
ꢀ12.66. [
a
]
þ291 (c 0.2, CHCl3).
D
3.2.6. (R,E)-N-(2,3-Dichlorobenzylidene)-20-(diphenylphosphino)-
1,10-binaphthyl-2-amine (L6)
A yellow solid; this is a known compound.11 1H NMR (CDCl3,
TMS, 300 MHz):
d 6.92–7.51 (m, 19H, ArH), 7.69–7.93 (m, 5H, ArH),
8.04 (d, J¼8.7 Hz, 1H, ArH), 8.50 (s, 1H, CH). 31P NMR (CDCl3,
3.2. General procedure of the preparation of chiral
phosphine-Schiff base type ligands L1–L11
20
121 MHz, 85% H3PO4):
d
ꢀ12.63. [
a]
þ392 (c 0.2, CHCl3).
D
3.2.7. (R,E)-20-(Diphenylphosphino)-N-(2-fluorobenzylidene)-
To a solution of (R)-(ꢀ)-2-(diphenylphosphino)-1,10-binaphthyl-
20-amine10,11 (227 mg, 0.5 mmol) in absolute ethanol (4.0 mL) was
added salicylaldehydes (0.5 mmol) or benzaldehydes (0.5 mmol) at
room temperature and the reaction mixture was stirred under reflux
overnight. After cooling to room temperature, precipitates settled
1,10-binaphthyl-2-amine (L7)
A yellow solid, mp 75–78 ꢁC. IR (CH2Cl2):
n
3052, 3007, 1612,
1581, 1502, 1485, 1458, 1433, 1300, 1279, 1265, 1238, 1216, 1149,
1096, 1026, 964 cmꢀ1 1H NMR (CDCl3, TMS, 300 MHz):
6.89–
.
d

Z.-L. Yuan et al. / Tetrahedron 65 (2009) 6001–6007
6005
7.48 (m, 22H, ArH), 7.82–7.92 (m, 3H, ArH), 8.02 (d, 1H, J¼8.4 Hz,
at room temperature. A solution of aldimine 1 (0.20 mmol) in THF
(0.5 mL) was added followed by phenylmethanol (0.36 mmol).
Siloxyfuran 2 (0.36 mmol) was added when the mixture was cooled
to ꢀ78 ꢁC, and the reaction mixture was stirred at ꢀ78 ꢁC for 6 h
then the reaction solution was warmed to room temperature natu-
rally and stirred overnight. The reaction was quenched by the ad-
dition of a saturated aqueous solution of NaHCO3 (2 mL). After
stirring for 15 min at room temperature, the mixture was extracted
by Et2O, washed with brine, and the organic layer was dried over
anhydrous Na2SO4. Then the solvent was removed under reduced
pressure and the residue was purified by flash column chromatog-
raphy (SiO2) to give the corresponding product 3.
ArH), 8.48 (s, 1H, CH). 31P NMR (CDCl3, 121 MHz, 85% H3PO4):
d
ꢀ12.65. 19F NMR (CDCl3, 282 MHz, CFCl3):
ꢀ121.94. MS (EI) m/e
d
559 [Mþ] (20.9), 438 (39.5), 437 (100), 359 (2.9), 326 (3.8), 281
(11.5), 183 (3.1), 179 (3.2), 109 (2.0). HRMS (EI) calcd for C39H27FNP
20
(MþHþ): 559.1865, found: 559.1863. [
a
]
þ156.8 (c 0.75, CH2Cl2).
D
3.2.8. (R,E)-N-(2-Bromobenzylidene)-20-(diphenylphosphino)-
1,10-binaphthyl-2-amine (L8)
A yellow solid, mp 76–78 ꢁC. IR (CH2Cl2):
n
3052, 1610, 1585,
1561, 1502, 1479, 1433, 1265, 1195, 1024, 965 cmꢀ1. 1H NMR (CDCl3,
TMS, 300 MHz): d 6.93–7.44 (m, 22H, ArH), 7.84–7.94 (m, 3H, ArH),
8.04 (d, 1H, J¼8.4 Hz, ArH), 8.53 (s, 1H, CH). 31P NMR (CDCl3,
121 MHz, 85% H3PO4):
d
ꢀ12.64. MS (EI) m/e 619 [Mþ] (6.3), 621
3.3.1. (S)-5-((R)-Phenyl(phenylamino)methyl)furan-2(5H)-one (3a)
(6.9), 540 (5.8), 438 (35.6), 437 (100), 357 (3.7), 281 (9.3), 183 (3.1),
A pale yellow solid; this is a known compound.18 1H NMR
77 (3.1). HRMS (EI) calcd for C39H27BrNP (MþHþ): 619.1064, found:
(300 MHz, CDCl3, TMS):
d
4.38 (1H, d, J¼6.4 Hz, NH), 4.84 (1H, dd,
20
619.1067. [
a
]
þ232.7 (c 0.85, CH2Cl2).
J¼4.4, 6.4 Hz, CH), 5.41 (1H, ddd, J¼1.2, 2.0, 4.4 Hz, CH), 6.04 (1H, dd,
J¼2.0, 6.0 Hz, CH), 6.54 (2H, d, J¼7.6 Hz, ArH), 6.70 (1H, t, J¼8.0 Hz,
ArH), 7.10 (2H, dd, J¼7.6, 8.0 Hz, ArH), 7.24–7.31 (5H, m, ArH), 7.34
(1H, dd, J¼1.2, 6.0 Hz, CH). Enantiomeric excess was determined by
D
3.2.9. (R,E)-20-(Diphenylphosphino)-N-(2-(trifluoromethyl)-
benzylidene)-1,10-binaphthyl-2-amine (L9)
A yellow solid, mp 85–88 ꢁC. IR (CH2Cl2):
n
3053, 1617, 1586,
HPLC with a Chiralcel OD-H column (hexane/iPrOH¼80:20, 1.0 mL/
20
1575, 1502, 1480, 1433, 1313, 1277, 1169, 1124, 1059, 1034, 967 cmꢀ1
.
min, 254 nm, tmajor¼19.52 min, tminor¼27.20 min; [
a
]
ꢀ108.2 (c
D
1H NMR (CDCl3, TMS, 300 MHz):
d
6.88–7.57 (m, 22H, ArH), 7.85–
0.65, CH2Cl2), 79% ee).
7.94 (m, 3H, ArH), 8.06 (d, 1H, J¼8.4 Hz, ArH), 8.56 (s, 1H, CH). 31P
NMR (CDCl3, 121 MHz, 85% H3PO4):
d
ꢀ12.70. 19F NMR (CDCl3,
3.3.2. (S)-5-((R)-(4-Nitrophenylamino)(phenyl)methyl)furan-
282 MHz, CFCl3):
d
ꢀ57.51. MS (EI) m/e 609 [Mþ] (11.7), 438 (38.3),
2(5H)-one 3b
437 (100), 357 (4.1), 281 (10.0), 250 (3.8), 218 (5.2), 179 (4.2), 77
A yellow solid, mp 152–155 ꢁC. IR (CH2Cl2):
n 3361, 3301, 3071,
(3.8). HRMS (EI) calcd for C40H27F3NP (MþHþ): 609.1833, found:
3019, 2970, 2925, 2346, 1742, 1599, 1528, 1502, 1477, 1365, 1322,
20
609.1830. [
a]
þ160.9 (c 0.50, CH2Cl2).
1303, 1229, 1217, 1197, 1159, 1111, 1025, 899 cmꢀ1. 1H NMR (300 MHz,
D
CDCl3, TMS):
d
4.99 (dd, 1H, J¼7.2, 3.6 Hz, CH), 5.21 (d, 1H, J¼4.2 Hz,
3.2.10. (R,E)-N-(2,4-Dimethoxybenzylidene)-20-(diphenyl-
NH), 5.51 (dd, J¼3.6, 1.8 Hz, CH), 6.10 (dd, J¼5.7, 2.1 Hz, CH), 6.53 (d,
phosphino)-1,10-binaphthyl-2-amine (L10)
2H, J¼9.3 Hz, ArH), 7.29–7.41 (m, 6H, ArHþCH), 8.02 (d, 2H, J¼9.0 Hz,
A yellow solid, mp 79–82 ꢁC. IR (CH2Cl2):
n
3459, 3381, 3052,
ArH). 13C NMR (75 MHz, CDCl3, TMS):
d 58.9, 84.3, 113.9, 119.2, 123.4,
3001, 2964, 2938, 2837, 1677, 1601, 1586, 1504, 1463, 1434, 1421,
124.0, 128.8, 129.2, 144.3, 145.3, 147.7, 152.9, 171.7. MS (EI) m/e 310
[Mþ] (6.9), 228 (15.6), 227 (100), 181 (36.9), 180 (9.1), 173 (12.7), 117
(15.5), 103 (10.5), 76 (11.0). HRMS (EI) calcd for C17H14N2O4 (MþHþ):
310.0954, found: 310.0956. Enantiomeric excess was determined by
1306, 1290, 1273, 1209, 1159, 1117, 1031, 966 cmꢀ1. 1H NMR (CDCl3,
TMS, 300 MHz): d 3.65 (s, 3H, CH3), 3.78 (s, 3H, CH3), 6.28–6.29 (m,
2H, ArH), 6.94–7.48 (m, 19H, ArH), 7.82–7.90 (m, 3H, ArH), 8.00 (d,
1H, J¼8.4 Hz, ArH), 8.55 (s, 1H, CH). 31P NMR (CDCl3, 121 MHz, 85%
HPLC with a Chiralcel OD-H column (hexane/iPrOH¼80:20, 0.7 mL/
20
H3PO4):
d
ꢀ12.56. MS (EI) m/e 601 [Mþ] (17.5), 570 (6.4), 438 (37.3),
min, 230 nm, tminor¼17.33 min, tmajor¼20.33 min; [
a
]
ꢀ29.5 (c
D
437 (100), 416 (5.0), 357 (5.0), 301 (11.6), 281 (9.9), 183 (4.4). HRMS
0.50, CH2Cl2), 38% ee).
20
(EI) calcd For C41H32NO2P (MþHþ): 601.2171, found: 601.2177. [
þ172.5 (c 0.65, CH2Cl2).
a]
D
3.3.3. (S)-5-((R)-(4-Methoxyphenylamino)(phenyl)methyl)-
furan-2(5H)-one 3c
3.2.11. (R,E)-N-(2-(Benzyloxy)-3,5-di-tert-butylbenzylidene)-20-
A white solid; this is a known compound.3 1H NMR (300 MHz,
(diphenylphosphino)-1,10-binaphthyl-2-amine (L11)
CDCl3, TMS): d 3.68 (3H, s, CH3), 4.12 (1H, br, NH), 4.77 (1H, d,
A yellow solid (mixtures of E- and Z-isomers), mp 88–91 ꢁC. IR
J¼3.0 Hz, CH), 5.41 (1H, d, J¼1.8 Hz, CH), 6.04 (1H, dd, J¼1.2, 5.7 Hz,
CH), 6.51 (2H, d, J¼9.0 Hz, ArH), 6.69 (2H, d, J¼9.0 Hz, ArH), 7.25–
7.30 (5H, m, ArH), 7.35 (1H, d, J¼5.7 Hz, CH). Enantiomeric excess
was determined by HPLC with a Chiralcel IC-H column (hexane/
(CH2Cl2):
1478, 1435, 1362, 1264, 1202, 1163, 1116, 1014, 964 cmꢀ1. 1H NMR
(CDCl3, TMS, 300 MHz): 1.03 (s, 9H, CH3), 1.39 (s, 9H, CH3), 4.52
n 3474, 3378, 3052, 2961, 2868, 1686, 1619, 1585, 1498,
d
(d, 1H, J¼12.3 Hz, CH2), 4.68 (d, 1H, J¼12.3 Hz, CH2), 6.75–7.41 (m,
iPrOH¼90:10, 0.7 mL/min, 214 nm, tmajor¼126.58 min, tminor¼
20
20H, ArH), 7.82–7.90 (m, 4H, ArH), 8.43 (s, 1H, CH). 31P NMR
151.22 min; [
a]
ꢀ55.6 (c 0.65, CH2Cl2), 62% ee).
D
(CDCl3, 121 MHz, 85% H3PO4):
d
ꢀ12.80, ꢀ12.25. MS (EI) m/e 759
[Mþ] (10.5), 669 (54.2), 668 (100), 468 (9.2), 453 (11.7), 437 (62.6),
3.3.4. (S)-5-((R)-Phenyl(3-(trifluoromethyl)phenylamino)-
281 (7.9), 201 (9.5), 91 (47.5). HRMS (EI) calcd for C54H50NOP
methyl)furan-2(5H)-one (3d)
20
(MþHþ): 759.3630, found: 759.3636.
[
a
]
þ159.0 (c 0.25,
A yellow solid, mp 127–132 ꢁC. IR (CH2Cl2):
n
3726, 3368, 3016,
2970, 2925, 2840, 2346, 1740, 1600, 1518, 1438, 1365, 1350, 1229,
1217,1160,1105, 900 cmꢀ1.1H NMR (300 MHz, CDCl3, TMS):
4.66 (d,
D
CH2Cl2).
d
3.3. General procedure for the reaction of aldimine 1 with
siloxyfuran 2 in the presence of AgOAc and chiral phosphine-
Shiff base ligand L6
1H, J¼6.9 Hz, NH), 4.89 (dd, 1H, J¼7.5, 4.2 Hz, CH), 5.45 (t, 1H,
J¼3.6 Hz, CH), 6.07 (dd, 1H, J¼6.0, 1.5 Hz, CH), 6.67 (dd, 1H, J¼6.0,
1.8 Hz, ArH), 6.79 (s, 1H, ArH), 6.92 (d, 1H, J¼7.8 Hz, CH), 7.18 (t, 1H,
J¼7.5 Hz, ArH), 7.28–7.38 (m, 6H, ArHþCH).13C NMR (75 MHz, CDCl3,
The procedure of AVM reaction was performed according to the
method stated in Snapper and Hoveyda’s report.4 AgOAc (0.02 -
mmol) and chiral phosphine-Shiff base ligand L6 (0.022 mmol) were
added into a Schlenk tube and then THF (0.5 mL) was added into the
reaction vessel. The resulting solution was allowed to stir for 30 min
TMS):
d
59.0, 84.8,110.3 (q, J¼3.9 Hz),114.9 (q, J¼4.1 Hz),116.6,123.5,
124.0 (q, J¼256 Hz), 127.0, 128.6, 129.0, 129.5, 129.7, 131.3 (q,
J¼32.1 Hz), 135.9, 146.2, 152.6, 172.0. 19F NMR (CDCl3, 282 MHz,
CFCl3):
d
ꢀ68.49. MS (EI) m/e 333 [Mþ] (0.7), 251 (16.3), 250 (100),
173 (2.7), 172 (22.2), 145 (30.6), 127 (1.6), 125 (2.1), 77 (5.9). HRMS

6006
Z.-L. Yuan et al. / Tetrahedron 65 (2009) 6001–6007
(EI) calcd for C18H14F3NO2 (MþHþ): 333.0977, found: 333.0981.
J¼1.5 Hz, CH), 6.03 (dd, 1H, J¼6.0, 2.1 Hz, CH), 6.50 (d, 2H, J¼7.5 Hz,
ArH), 6.72 (t, 1H, J¼7.2 Hz, Ar), 7.09–7.19 (m, 3H, ArH), 7.32 (d, 1H,
J¼8.4 Hz, ArH), 7.37 (d, 1H, J¼2.1 Hz, Ar), 7.52 (dd, 1H, J¼5.7, 1.2 Hz,
Enantiomeric excess was determined by HPLC with a Chiralcel AD-H
column(hexane/iPrOH¼90:10,0.7 mL/min, 230 nm, tminor¼8.63 min,
20
tmajor¼13.28 min; [
a
]
ꢀ80.8 (c 2.10, CH2Cl2), 65% ee).
CH). 13C NMR (75 MHz, CDCl3, TMS):
d 54.8, 83.9, 113.5, 118.9, 123.5,
D
127.9, 129.3, 129.4, 129.6, 132.2, 133.9, 134.7, 145.1, 151.9, 171.8. MS
(EI) m/e 333 [Mþ] (2.0), 254 (11.1), 252 (63.2), 250 (100), 214 (10.9),
152 (5.5), 104 (24.2), 93 (3.6), 77 (38.5). HRMS (EI) calcd for
C17H13Cl2NO2 (MþHþ): 333.0323, found: 333.0318. Enantiomeric
excess was determined by HPLC with a Chiralcel OD-H column
3.3.5. (S)-5-((R)-(4-Bromophenyl)(4-bromophenylamino)-
methyl)furan-2(5H)-one (3e)
A pale yellow solid, mp 147–152 ꢁC. IR (CH2Cl2):
n
3371, 3032,
2970, 2925, 2372, 2351,1744,1594,1489,1366,1229,1217,1160,1092,
1073, 1010, 901 cmꢀ1. 1H NMR (300 MHz, CDCl3, TMS):
4.44 (1H, d,
d
(hexane/iPrOH¼80:20, 1.0 mL/min, 254 nm, tminor¼16.36 min,
20
J¼6.9 Hz, NH), 4.78 (1H, dd, J¼0.9, 6.9 Hz, CH), 5.43 (1H, ddd, J¼0.9,
1.2,1.8 Hz, CH), 6.09 (1H, dd, J¼1.8, 6.0 Hz, CH), 6.40 (2H, d, J¼9.0 Hz,
ArH), 7.15–7.21 (4H, m, ArH), 7.34 (1H, dd, J¼1.2, 6.0 Hz, CH), 7.46 (2H,
tmajor¼24.32 min; [
a]
ꢀ103.5 (c 1.05, CH2Cl2), 81% ee).
D
3.3.9. (S)-5-((R)-(4-Nitrophenyl)(phenylamino)methyl)-
furan-2(5H)-one (3i)
d, J¼8.4 Hz, ArH). 13C NMR (75 MHz, CDCl3, TMS):
d
58.8, 84.5, 110.6,
115.5,122.4,123.6,128.8,131.9,132.0,135.1,144.6,152.4,171.8. MS (EI)
m/e 421 [Mþ] (2.6), 343 (7.0), 342 (47.2), 340 (100), 338 (50.8), 184
(15.8), 115 (10.8), 89 (10.2), 76 (17.0). HRMS (EI) calcd for
C17H13Br2NO2 (MþHþ): 420.9313, found: 420.9308. Enantiomeric
excess was determined by HPLC with a Chiralcel OD-H column
A yellow oil. IR (CH2Cl2):
1759, 1602, 1519, 1437, 1347, 1319, 1278, 1254, 1160, 1104, 1045,
993 cmꢀ1. 1H NMR (300 MHz, CDCl3, TMS):
n 3378, 3107, 3053, 2923, 2847, 1929,
d
4.56 (1H, d, J¼7.2 Hz,
NH), 4.95 (1H, dd, J¼3.6, 7.2 Hz, CH), 5.48 (1H, ddd, J¼1.6, 2.0,
3.6 Hz, CH), 6.09 (1H, dd, J¼2.0, 5.6 Hz, CH), 6.52 (2H, d, J¼8.8 Hz,
ArH), 6.74 (1H, t, 7.6 Hz, ArH), 7.12 (2H, dd, J¼7.6, 8.8 Hz, ArH), 7.41
(1H, dd, J¼1.6, 5.6 Hz, CH), 7.51 (2H, d, J¼8.4 Hz, ArH), 8.17 (2H, d,
(hexane/iPrOH¼80:20, 1.0 mL/min, 254 nm, tminor¼21.62 min,
20
tmajor¼32.03 min; [
a
]
ꢀ111.2 (c 2.15, CH2Cl2), 62% ee).
D
J¼8.4 Hz, ArH). 13C NMR (75 MHz, CDCl3, TMS):
d 58.9, 84.3, 113.7,
3.3.6. (S)-5-((R)-(4-Bromophenylamino)(2-(trifluoro-
methyl)phenyl)methyl)furan-2(5H)-one (3f)
119.0, 123.5, 123.9, 128.4, 129.3, 144.3, 145.1, 147.7, 152.5, 171.6. MS
(EI) m/e 310 [Mþ] (7.0), 228 (15.5), 227 (100), 181 (42.3), 180 (17.5),
168 (7.7), 115 (7.3), 93 (12.7), 77 (24.3). HRMS (ESI) calcd for
C17H14N2O4 (MþHþ): 310.0954, found: 310.0952. Enantiomeric
excess was determined by HPLC with a Chiralcel AD-H column
A pale yellow oil. IR (CH2Cl2):
1764, 1697, 1594, 1491, 1453, 1401, 1310, 1276, 1251, 1164, 1118, 1074,
1036, 901 cmꢀ1 1H NMR (300 MHz, CDCl3, TMS):
4.45 (d, 1H,
n 3376, 3098, 2954, 2925, 2854,
.
d
J¼6.6 Hz, NH), 5.32 (dd, 1H, J¼7.8, 2.1 Hz, CH), 5.49 (d, 1H, J¼2.1 Hz,
CH), 6.09 (d, 1H, J¼3.9 Hz, CH), 6.48 (d, 2H, J¼8.1 Hz, ArH), 7.20 (d,
2H, J¼8.1 Hz, ArH), 7.38–7.45 (m, 2H, ArH), 7.51–7.62 (m, 2H, ArH),
(hexane/iPrOH¼80:20, 1.0 mL/min, 230 nm, tminor¼18.38 min,
20
tmajor¼24.23 min; [
a]
ꢀ92.7 (c 2.00, CH2Cl2), 59% ee).
D
7.71 (d, 1H, J¼6.9 Hz, CH). 13C NMR (75 MHz, CDCl3, TMS):
d
54.6,
3.3.10. (S)-5-((R)-(2-Methoxyphenylamino)phenylmethyl)-
furan-2(5H)-one (3j)
84.0, 110.9, 115.7, 123.7, 124.3 (q, J¼270 Hz), 126.6 (q, J¼5.3 Hz),
127.9, 128.2 (q, J¼30 Hz), 128.7, 132.7, 135.4, 144.3, 152.3, 171.7. 19F
A pale yellow solid, mp 143–146 ꢁC. IR (CH2Cl2):
n
3416, 3063,
2938, 2835,1762, 1600, 1512,1455,1430,1340,1245, 1222,1157, 1132,
1105, 1026, 896 cmꢀ1. 1H NMR (300 MHz, CDCl3, TMS):
3.87 (s, 3H,
NMR (CDCl3, 282 MHz, CFCl3):
d
ꢀ62.80. MS (EI) m/e 411 [Mþ] (4.7),
331 (15.3), 330 (89.3), 328 (100), 310 (56.8), 308 (58.8), 229 (39.6),
134 (16.9), 76 (24.9). HRMS (EI) calcd for C18H13BrF3NO2 (MþHþ):
411.0082, found: 411.0084. Enantiomeric excess was determined by
d
CH3), 4.85 (d,1H, J¼3.6 Hz, NH), 4.93 (d,1H, J¼5.1 Hz, CH), 5.45 (t,1H,
J¼2.1 Hz, CH), 6.11 (dd, 1H, J¼5.1, 1.5 Hz, CH), 6.37 (dd, 1H, J¼5.1,
1.5 Hz, CH), 6.63–6.78 (m, 3H, ArH), 7.26–7.34 (m, 5H, ArH), 7.39 (dd,
HPLC with a Chiralcel OD-H column (hexane/iPrOH¼90:10, 0.7 mL/
20
min, 230 nm, tminor¼21.33 min, tmajor¼30.93 min; [
a]
ꢀ65.5 (c
1H, J¼5.1, 1.5 Hz, CH). 13C NMR (75 MHz, CDCl3, TMS):
d 55.5, 59.2,
D
0.70, CH2Cl2), 55% ee).
85.4, 109.5, 111.3, 117.7, 120.9, 123.2, 127.1, 128.2, 128.8, 135.9, 137.1,
147.0, 153.0, 172.3. MS (EI) m/e 295 [Mþ] (2.6), 213 (17.0), 212 (100),
196 (17.5),134 (1.1),120 (33.6),115 (7.3), 91 (17.5), 77 (9.7). HRMS (ESI)
calcd for C17H14N2O4 (MþHþ): 295.1208, found: 295.1207. Enantio-
meric excess was determined by HPLC with a Chiralcel OD-H column
3.3.7. (S)-5-((R)-(4-Bromophenylamino)(2,4-dimethoxy-
phenyl)methyl)furan-2(5H)-one (3g)
A pale yellow oil. IR (CH2Cl2):
1744, 1605, 1591, 1502, 1455, 1365, 1293, 1263, 1229, 1216, 1207, 1158,
1090, 1034, 898 cmꢀ1. 1H NMR (300 MHz, CDCl3, TMS):
3.75 (s, 3H,
n 3727, 3375, 3025, 2970, 2840, 2346,
(hexane/iPrOH¼80:20, 1.0 mL/min, 254 nm, tmajor¼26.62 min,
20
d
tminor¼47.77 min; [
a
]
ꢀ85.8 (c 0.75, CH2Cl2), 63% ee).
D
CH3), 3.85 (s, 3H, CH3), 4.56 (d, 1H, J¼8.4 Hz, NH), 4.89 (t, 0.6H,
J¼1.5 Hz, CH, NH), 5.16 (dd, 1H, J¼8.1, 4.2 Hz, CH), 5.48 (t, 1H, J¼1.8 Hz,
CH), 5.99 (dd, 1H, J¼5.4, 1.8 Hz, CH), 6.16 (dd, 0.3H, J¼7.8, 1.8 Hz, CH),
6.37–6.44 (m, 4H, ArH), 7.07 (d, 1H, J¼8.4 Hz, ArH), 7.13 (d, 2H,
J¼8.7 Hz, ArH), 7.40 (dd, 1H, J¼5.7, 1.2 Hz, CH), 7.55 (dd, 0.3H, J¼5.7,
3.3.11. (R)-5-((S)-{4-Chlorophenyl-(diphenylphosphinoylamino)}-
methyl)-(5H)-furan-2-one (3k)
A white solid; this is a known compound.20 1H NMR (300 MHz,
CDCl3, TMS):
d
4.31 (dd,1H, J¼9.6, 6.6 Hz, NH), 4.54 (ddd,1H, J¼3.6, 3.6,
1.2 Hz, CH). 13C NMR (75 MHz, CDCl3, TMS):
d
52.7, 55.2, 55.4, 84.4,
10.8 Hz, CH), 5.56 (s, 1H, CH), 5.90 (d, 1H, J¼5.7 Hz, CH), 7.05 (d, 2H,
J¼8.4 Hz, ArH), 7.21 (d, 2H, J¼8.4 Hz, ArH), 7.36–7.54 (m, 7H, ArH and
CH), 7.69 (dd, 2H, J¼12.0, 7.8 Hz, ArH), 7.82 (dd, 2H, J¼12.0, 7.8 Hz, ArH).
Enantiomeric excess was determined by HPLC with a Chiralcel OD-H
98.4, 104.5, 109.7, 115.2, 115.7, 121.5, 122.6, 128.5, 131.8, 145.2, 153.3,
157.6, 160.6, 172.5. MS (EI) m/e 403 [Mþ] (0.7), 323 (18.0), 322 (99.2),
321 (20.4), 320 (100), 233 (12.1), 149 (14.8), 121 (12.9), 77 (6.1). HRMS
(EI) calcd for C19H18BrNO4 (MþHþ): 403.0419, found: 403.0424. En-
antiomeric excess was determined by HPLC with a Chiralcel OD-H
column (hexane/iPrOH¼90:10, 0.7 mL/min, 214 nm, tmajor¼24.15 min,
20
tminor¼32.21 min; [
a
]
þ13.5 (c 2.00, CHCl3), 43% ee).
D
column (hexane/iPrOH¼90:10, 0.7 mL/min, 230 nm, tminor¼44.13 min,
20
tmajor¼67.98 min; [
a
]
ꢀ100.1 (c 2.65, CH2Cl2), 80% ee).
Acknowledgements
D
3.3.8. (S)-5-((R)-(2,4-Dichlorophenyl)(phenylamino)methyl)-
furan-2(5H)-one (3h)
Financial support from the Shanghai Municipal Committee of
Science and Technology (06XD14005 and 08dj1400100-2), National
Basic Research Program of China (973)-2009CB825300, and the
National Natural Science Foundation of China (20872162,
20672127, 20732008, 20821002, and 20702013) are greatly
acknowledged.
A pale yellow oil. IR (CH2Cl2):
2320, 1753, 1602, 1561, 1504, 1470, 1453, 1384, 1316, 1229, 1217,
1158, 1103, 1043, 993 cmꢀ1. 1H NMR (300 MHz, CDCl3, TMS):
4.65
(d, 1H, J¼8.1 Hz, NH), 5.40 (dd, 1H, J¼5.4, 3.3 Hz, CH), 5.55 (t, 1H,
n 3377, 3089, 3054, 2924, 2847,
d

Z.-L. Yuan et al. / Tetrahedron 65 (2009) 6001–6007
6007
9. Reviews for the silver-catalyzed asymmetric reactions, please see: (a) Naodovic,
M.; Yamamoto, H. Chem. Rev. 2008, 108, 3132–3148; (b) Yanagisawa, A.; Arai, T.
Chem. Commun. 2008, 1165–1172.
10. (a) Sumi, K.; Ikariya, T.; Noyori, R. Can. J. Chem. 2000, 78, 697–703; (b) Botman,
P. N. M.; David, O.; Amore, A.; Dinkelaar, J.; Vlaar, M. T.; Goubitz, K.; Fraanje, J.;
Schenk, H.; Hiemstra, H.; van Maarseveen, J. H. Angew. Chem., Int. Ed. 2004, 43,
3471–3473.
11. Jiang, J. J.; Shi, M. Tetrahedron: Asymmetry 2007, 18, 1376–1382.
12. For a review on the effect of additives in asymmetric catalysis, please see: Vogl,
E. M.; Groger, H.; Shibasaki, M. Angew. Chem., Int. Ed. 1999, 38, 1570–1577.
13. Onitsuka, S.; Matsuoka, Y.; Irie, R.; Katsuki, T. Chem. Lett. 2003, 32, 974–975.
14. Zhou, J.; Ye, M. C.; Huang, Z. Z.; Tang, Y. J. Org. Chem. 2004, 69, 1309–1320.
15. References on the use of NaBArF in catalytic asymmetric reactions, please see:
(a) Liu, B.; Zhu, S. F.; Zhang, W.; Chao, C.; Zhou, Q. L. J. Am. Chem. Soc. 2007, 129,
5834–5835; (b) Chao, C.; Zhu, S. F.; Liu, B.; Wang, L. X.; Zhou, Q. L. J. Am. Chem.
Soc. 2007, 129, 12616–12617.
Supplementary data
Spectroscopic data of the compounds shown in Tables 1–4 and
the detailed descriptions of experimental procedures. This material
is available free of charge via the Internet at the Website. Supple-
mentary data associated with this article can be found in the online
version, at doi:10.1016/j.tet.2009.05.080.
References and notes
1. For a review, please see: Bur, S. K.; Martin, S. F. Tetrahedron 2001, 57, 3221–3242.
2. Reviews for catalytic asymmetric Mannich-type reactions, please see: (a)
Kobayashi, S.; Ishitani, H. Chem. Rev. 1999, 99, 1069–1094; (b) Co´ rdova, A.;
Cicchi, S.; Cordero, F. M.; Goti, A. Acc. Chem. Res. 2004, 37, 102–112; (c)
Friestad, G. K.; Mathies, A. K. Tetrahedron 2007, 63, 2541–2569.
3. Martin, S. F.; Lopez, O. D. Tetrahedron Lett. 1999, 40, 8949–8953.
4. (a) Carswell, E. L.; Snapper, M. L.; Hoveyda, A. H.; Tang, J. Angew. Chem., Int. Ed.
2006, 45, 7230–7233; (b) Mandai, H.; Mandai, K.; Snapper, M. L.; Hoveyda, A. H.
J. Am. Chem. Soc. 2008, 130, 17961–17969.
16. Kuroda, R. S.; Mason, F. J. Chem. Soc., Dalton. Trans. 1979, 727–732.
17. The crystal data of 3e have been deposited in CCDC with number 714003.
Empirical formula: C17H13Br2NO2; formula weight: 423.10; crystal color, habit:
colorless, prismatic; crystal dimensions: 0.426ꢂ0.347ꢂ0.321 mm; crystal sys-
tem: orthorhombic; lattice type: primitive; lattice parameters: a¼8.781(2) Å,
b¼13.481(4) Å, c¼13.712(4) Å,
a
¼90ꢁ,
b
¼90ꢁ,
g
¼90ꢁ, V¼1623.2(8) Å3. Space
group: P2(1)2(1)2(1); Z¼4; Dcalcd¼1.731 g/cm3; F000¼832. Diffractometer: Ri-
5. Gonza´lez, A. S.; Arraya´s, R. G.; Rivero, M. R.; Carretero, J. C. Org. Lett. 2008, 10,
4335–4337.
gaku AFC7R. Residuals: R; Rw: 0.0923, 0.2091.
18. Oudeyer, S.; Dudot, B.; Royer, J. Heterocycles 2005, 65, 823–841.
19. Selected reports on the deprotection of N-diphenylphosphinoyl group: (a) Boe-
zio, A. A.; Pytkowicz, J.; Cote, A.; Charette, A. B. J. Am. Chem. Soc. 2003,125,14260–
14261; (b) Lee, W.-Y.; Salvador, J. M.; Bodige, K. Org. Lett. 2000, 2, 931–932.
20. Yamaguchi, A.; Matsunaga, S.; Shibasaki, M. Org. Lett. 2008, 10, 2319–2322.
6. Liu, T. Y.; Cui, H. L.; Long, J.; Li, B. J.; Wu, Y.; Ding, L. S.; Chen, Y. C. J. Am. Chem.
Soc. 2007, 129, 1878–1879.
7. Akiyama, T.; Honma, Y.; Itoh, J.; Fuchibe, K. Adv. Synth. Catal. 2008, 350, 399–402.
8. (a) Giera, D. S.; Sichert, M.; Schneider, C. Org. Lett. 2008, 10, 4259–4262; (b)
Sichert, M.; Schneider, C. Angew. Chem., Int. Ed. 2008, 47, 3631–3634.