Pd-catalyzed asymmetric allylic etherizations with oximes by chiral alkene-phosphine ligands

Article abstract of DOI:10.1021/jo200925q

Palladium-catalyzed asymmetric allylic etherizations with a variety of oximes as nucleophiles utilizing a chiral alkene-phosphine hybrid ligand have been successfully achieved for the first time to afford the optical active oxime ethers in high yields with good to excellent enantioselectivities.

Full text of DOI:10.1021/jo200925q

NOTE
pubs.acs.org/joc
Pd-Catalyzed Asymmetric Allylic Etherizations with Oximes by Chiral
Alkene-Phosphine Ligands
Ziping Cao, Zhaoqun Liu, Yilin Liu, and Haifeng Du*
Beijing National Laboratory of Molecular Sciences, CAS Key Laboratory of Molecular Recognition and Function, Institute of Chemistry,
Chinese Academy of Sciences, Beijing 100190, China
S Supporting Information
b
ABSTRACT: Palladium-catalyzed asymmetric allylic etheriza-
tions with a variety of oximes as nucleophiles utilizing a chiral
alkene-phosphine hybrid ligand have been successfully achieved
for the first time to afford the optical active oxime ethers in high
yields with good to excellent enantioselectivities.
d-catalyzed asymmetric allylic substitutions provide a prac-
tical and efficient approach to construct the CꢀC, CꢀN, and
high activities and selectivities in palladium-catalyzed asymmetric
allylic substitutions.42,43 On the basis of our previous study, we
envision that chiral terminal-alkene-phosphine hybrid ligands
will be suitable for Pd-catalyzed asymmetric allylic etherizations
with oximes. Herein, we report our efforts on this subject.
Because Pd(PPh3)4 was an efficient catalyst for the allylic
etherization of 1,3-diphenyl-2-propenyl acetate (1a) with oxime
2a (Scheme 1),9 initially, various well-established chiral phos-
phine ligands44ꢀ48 were subjected to this reaction to examine the
activity and selectivity (Scheme 2). It was disappointing to find
that ligands 4ꢀ7 led to only 6ꢀ29% yields with 13ꢀ76% ee’s,
which indicated that the challenge still remained in this asym-
metric transformation. We were pleased to find that alkene/
phosphine hybrid ligand 8a43 was highly effective for this reaction
to give the desired oxime ether 3a in 95% yield with 83% ee, while
a control experiment with 8b43 as a ligand afforded only a small
amount of product 3a with 8% ee (Scheme 2). The terminal
alkene moieties in ligand 8a proved to be essential for the
observed high activity and selectivity.
P
CꢀO bonds enantioselectively from readily available starting
materials.1ꢀ3 Oximes can be easily obtained by a simple con-
densation of aldehydes or ketones with hydroxylamine and have
been widely utilized in synthetic chemistry.4ꢀ8 In 2004, Take-
moto and co-workers described the first Ir-catalyzed allylic
substitutions with oximes.9 Therein, they also reported one
example of allylic substitution catalyzed by Pd(PPh3)4 (Scheme 1).9
Soon after that, Takemoto and co-workers realized the Ir-
catalyzed asymmetric transformation.10ꢀ13 However, to the best
of our knowledge, few applications of oximes as nucleophiles in
Pd-catalyzed asymmetric allylic substitutions that would provide
access to useful optically active oxime ethers14ꢀ20 have been
reported. The key point to achieve this enantioselective trans-
formation is to determine suitable chiral ligands.
Scheme 1. Pd-Catalyzed Allylic Etherization with Oxime 2a
To further improve the enantioselectivities, various reaction
conditions were then optimized. As shown in Table 1, both base
and solvent had some impact on the reactivity and enantioselec-
tivity. We found that the allylic etherization of 1,3-diphenyl-2-
propenyl acetate (1a) with oxime 2a under the catalysis of 8a/Pd
(3.0 mol %) using N,N-diisopropylethylamine (DIPEA) as a base
and CH3CN as a solvent went smoothly to give the best
enantioselectivity (Table 1, entry 11).
Under optimized conditions, chiral alkene/phosphine ligands
were subsequently evaluated to search for more effective ligands.
Compared with ligand 8a, ligand 8c43 gave a similar yield but a
lower ee, and ligand 8e43 gave a little higher ee (Figure 1). Ligand
8f43 containing an internal double bond led to only 10% yield
Chiral olefins as one type of lately emerging ligands have
attracted intensive attention.21ꢀ24 Both chiral diene25ꢀ31 and
hybrid olefin ligands incorporated with heteroatoms such as
phosphorus32ꢀ35 or nitrogen36,37 have been well developed and
successfully applied in asymmetric catalysis. Recently, our group
developed a variety of acyclic chiral diene ligands for Rh-
catalyzed asymmetric additions.38ꢀ41 Particularly, a strategy
was adopted in our group for the exploring of novel alkene-
phosphine hybrid ligand by the combination of the terminal
alkene and the phosphorus atom. These resulting ligands showed
Received: May 6, 2011
Published: June 13, 2011
r
2011 American Chemical Society
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|

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NOTE
Scheme 2. Pd-Catalyzed Asymmetric Allylic Etherization
with Oxime 2a
Figure 1. Evaluation of chiral alkene-phosphine ligands for Pd-cata-
lyzed asymmetric etherization with oxime 2a.
Scheme 3. Synthesis of Chiral Amine from the Oxime Ether
Table 1. Optimization of Reaction Conditionsa
entry
base
solvent
yield (%)b
ee (%)c
1
K2CO3
Na2CO3
Li2CO3
Cs2CO3
KOAc
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
CH2Cl2
THF
95
86
83
85
86
84
83
84
85
86
86
87
90
2
3
50
4
99
5
96
gave only low yield and ee (Table 2, entry 21). Oximes derived
from aliphatic aldehydes or ketones were ineffective for the
current system, and the reason still awaits further investigation.
The absolute configuration of product 3l was determined as S by
the X-ray structure of derivatives (Supporting Information), and
the configurations of other products were tentatively assigned by
analogy.
The resulting oxime ethers provide access to optically active
amines. For example, compound 3a can be easily converted to
compound 9 in a reasonable yield with excellent diastereoselec-
tivity after hydrogenation with H2 and addition with n-butyl-
lithium (Scheme 3). The NꢀO bond was then cleaved efficiently
by treating with Zn/HOAc according to the reported metho-
ds10,15ꢀ20 to afford both optically active alcohol 10 and amine 11.
In conclusion, terminal-alkene-phosphine hybrid ligands
proved to be highly effective for palladium-catalyzed asymmetric
allylic etherizations of 1,3-diaryl-2-propenyl acetates with oximes
to give optically active oxime ethers in high yields and ee’s.
Importantly, the current study also provides an attractive ap-
proach for the synthesis of optically active amines.
6
Et3N
87
7
DIPEA
DIPEA
DIPEA
DIPEA
DIPEA
>99
98
8
9
toluene
dioxane
CH3CN
99
10
11
82
91
a All reactions were carried out with 1a (0.24 mmol), 2a (0.20 mmol),
Pd/8a = 1/1 (3 mol % Pd), base (0.40 mmol), and solvent (1.0 mL) at
room temperature for 2 h. b Yield based on oxime 2a. c The ee was
determined by chiral HPLC (Chiralpak IC column).
with 66% ee for the reverse absolute configuration, which was
probably the result of the steric hindrance on the double bond.
With the optimized condition and the best ligand in hand, the
substrate scope for Pd-catalyzed asymmetric allylic etherization
with oximes was examined, and all the results are summarized in
Table 2. It was found that oximes derived from aromatic
aldehydes or ketones were effective substrates to give the desired
products in 54ꢀ99% yields with 89ꢀ96% ee’s (Table 2, entries
1ꢀ15, 18ꢀ20), and enantiomerically pure oxime ethers were
obtained after a single recrystallization in hexanes (Table 2,
entries 1 and 14). It is worth noting that R-carbonyloximes
2pꢀ2r were also suitable substrates for this reaction to give the
corresponding products in good yields and ee’s (Table 2, entries
16ꢀ18). However, using cyclohex-2-enyl actetate as a substrate
’ EXPERIMENTAL SECTION
General Procedure for 8e/Pd-Catalyzed Asymmetric Al-
lylic Etherization with Oxime. To a dried Schlenk flask charged
with [PdCl(C3H5)]2 (0.0022 g, 0.006 mmol, 3.0 mol % Pd) and ligand
8e (0.0062 g, 0.012 mmol, 3 mol %) was added distilled CH3CN
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NOTE
Table 2. Pd/8e-Catalyzed Asymmetric Allylic Etherization with Oximesa
a All reactions were carried out with 1 (0.48 mmol), oxime 2 (0.40 mmol), [PdCl(C3H5)]2 (0.006 mmol), 8e (0.012 mmol), DIPEA (0.80 mmol), and
CH3CN (2.0 mL) at 0 °C for 2 h unless otherwise noted. b Ligand 8a was used. c The absolute configuration was tentatively assigned by analogy with (S)-
3l. d Yield based on oxime. e The ee values were determined by chiral HPLC. f The ee in parentheses was determined after a single recrystallization in
hexanes (75% yield for entry 1, 74% yield for entry 14). g The reaction was conducted with 5 mol % catalyst at room temperature for 8 h.
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NOTE
(0.6 mL) under argon, and the resulting mixture was stirred at room
temperature for 20 min before being cooled to 0 °C. Then a solution of
1,3-diphenyl-2-propenyl acetate 1a (0.1210 g, 0.48 mmol) and oxime 2
(0.4 mmol) in CH3CN (1.40 mL) and DIPEA (0.1032 g, 0.8 mmol) was
added. After 2 h of stirring at 0 °C, the reaction mixture was concentrated
under reduced pressure, and the crude residue was purified by flash
chromatography on silica gel to afford the desired product 3.
Benzaldehyde O-[(1S,2E)-1,3-Diphenyl-2-propen-1-yl]o-
xime (Table 2, entry 1). White solid, mp 70ꢀ71 °C, [R]20D +39.4
(c 0.66, CH2Cl2) (93% ee); IR (film) 1494, 1447 cmꢀ1; 1H NMR (400
MHz, CDCl3) δ 8.22 (s, 1H), 7.60ꢀ7.54 (m, 2H), 7.47 (d, J = 7.2 Hz,
2H), 7.44ꢀ7.28 (m, 10H), 7.27ꢀ7.21 (m, 1H), 6.68 (d, J = 16.0 Hz,
1H), 6.52 (dd, J = 16.0, 6.8 Hz, 1H), 5.89 (d, J = 6.8 Hz, 1H); 13C NMR
(100 MHz, CDCl3) δ 149.4, 140.6, 136.8, 132.7, 132.5, 130.0, 129.2,
128.8, 128.7, 128.6, 128.1, 128.0, 127.6, 127.3, 126.9, 86.1. Anal. Calcd
for C22H19NO: C, 84.31; H, 6.11; N, 4.47. Found: C, 84.34; H, 6.04;
N, 4.46.
(m, 2H), 7.22 (dd, J = 7.6, 7.2 Hz, 1H), 6.69 (d, J = 16.0 Hz, 1H),
6.52 (dd, J = 16.0, 6.8 Hz, 1H), 5.90 (d, J = 6.8 Hz, 1H); 13C NMR (100
MHz, CDCl3) δ 146.4, 140.4, 136.7, 134.0, 132.8, 130.9, 130.2, 129.9,
129.0, 128.7, 128.2, 128.1, 127.6, 127.5, 127.0, 126.9, 86.5. Anal. Calcd
for C22H18ClNO: C, 75.97; H, 5.22; N, 4.03. Found: C, 76.02; H, 5.30;
N, 3.91.
2-Naphthaldehyde O-[(1S,2E)-1,3-Diphenyl-2-propen-
1-yl]oxime (Table 2, entry 7). White solid, mp 74ꢀ75 °C,
[R]20 +35.5 (c 0.4, CH2Cl2) (94% ee); IR (film) 1510, 1494,
D
1
1449 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.85 (s, 1H), 8.55ꢀ8.51
(m, 1H), 7.86 (d, J = 7.6 Hz, 2H), 7.73 (d, J = 7.2 Hz, 1H), 7.54 (d, J = 8.0
Hz, 2H), 7.52ꢀ7.49 (m, 2H), 7.49ꢀ7.39 (m, 5H), 7.38ꢀ7.30 (m, 3H),
7.28ꢀ7.22 (m, 1H), 6.77 (d, J = 16.0 Hz, 1H), 6.59 (dd, J = 16.0, 6.8 Hz,
1H), 5.99 (d, J = 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 149.3,
140.6, 136.8, 134.0, 132.9, 130.8, 130.6, 129.2, 128.8, 128.7, 128.3,
128.1, 128.0, 127.9, 127.7, 127.2, 126.9, 126.3, 125.4, 125.0, 86.3. Anal.
Calcd for C26H21NO: C, 85.92; H, 5.82; N, 3.85. Found: C, 86.16; H,
5.93; N, 3.88.
4-Methylbenzaldehyde O-[(1S,2E)-1,3-Diphenyl-2-pro-
pen-1-yl]oxime (Table 2, entry 2). White solid, mp 81ꢀ82 °C,
Acetophenone O-[(1S,2E)-1,3-Diphenyl-2-propen-1-yl]oxi-
me (Table 2, entry 8). White solid, mp 103ꢀ104 °C, [R]20D +36.6 (c
0.68, CH2Cl2) (93% ee); IR (film) 1494, 1448, 1368 cmꢀ1; 1H NMR
(400 MHz, CDCl3) δ 7.72ꢀ7.66 (m, 2H), 7.54 (d, J = 7.6 Hz, 2H),
7.51ꢀ7.42 (m, 4H), 7.42ꢀ7.33 (m, 6H), 7.32ꢀ7.26 (m, 1H), 6.74 (d,
J = 16.0 Hz, 1H), 6.59 (d, J = 16.0, 6.8 Hz, 1H), 6.00 (d, J = 6.8 Hz, 1H),
2.41 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 155.2, 141.1, 136.9, 136.8,
132.2, 129.8, 129.2, 128.7, 128.6, 128.5, 127.9, 127.8, 127.4, 126.9, 126.3,
86.0, 13.3. Anal. Calcd for C23H21NO: C, 84.37; H, 6.46; N, 4.28.
Found: C, 84.43; H, 6.58; N, 4.24.
[R]20 +50.7 (c 0.42, CH2Cl2) (94% ee); IR (film) 1604, 1494,
D
1
1450 cmꢀ1; H NMR (400 MHz, CDCl3) δ 8.24 (s, 1H), 7.54ꢀ7.48
(m, 4H), 7.48ꢀ7.39 (m, 4H), 7.38ꢀ7.31 (m, 3H), 7.30ꢀ7.23 (m, 1H),
7.18 (d, J = 8.0 Hz, 2H), 6.72 (d, J = 16.0 Hz, 1H), 6.56 (dd, J = 16.0, 6.4
Hz, 1H), 5.92 (d, J = 6.4 Hz, 1H), 2.38 (s, 3H); 13C NMR (100 MHz,
CDCl3) δ 149.5, 140.7, 140.2, 136.9, 132.6, 129.7, 129.5, 129.3, 128.7,
128.6, 128.0, 127.9, 127.6, 127.3, 126.9, 86.0, 21.6. Anal. Calcd for
C23H21NO: C, 84.37; H, 6.46; N, 4.28. Found: C, 84.32; H, 6.45;
N, 4.25.
4-Chlorobenzaldehyde O-[(1S,2E)-1,3-Diphenyl-2-propen-
1-yl]oxime (Table 2, entry 3). White solid, mp 113ꢀ115 °C,
[R]20D +49.2 (c 0.33, CH2Cl2) (93% ee); IR (film) 1597, 1492, 1450,
1299 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.19 (s, 1H), 7.54ꢀ7.46 (m,
4H), 7.46ꢀ7.38 (m, 4H), 7.38ꢀ7.30 (m, 5H), 7.26 (dd, J = 8.0, 6.4 Hz,
1H), 6.70 (d, J = 16.0 Hz, 1H), 6.53 (dd, J = 16.0, 6.8 Hz, 1H), 5.90 (d,
J = 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 148.2, 140.5, 136.7,
135.8, 132.8, 131.0, 129.1, 129.0, 128.7, 128.6, 128.5, 128.2, 128.1, 127.5,
126.9, 86.3. Anal. Calcd for C22H18ClNO: C, 75.97; H, 5.22; N, 4.03.
Found: C, 76.13; H, 5.24; N, 4.00.
3-Chlorobenzaldehyde O-[(1S,2E)-1,3-Diphenyl-2-propen-
1-yl]oxime (Table 2, entry 4). Colorless oil, [R]20D +35.7 (c 0.98,
CH2Cl2) (92% ee); IR (film) 1596, 1563, 1494, 1480, 1450 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 8.16 (s, 1H), 7.59 (m, 1H), 7.46 (d, J = 8.0
Hz, 2H), 7.44ꢀ7.37 (m, 5H), 7.36ꢀ7.28 (m, 4H), 7.28ꢀ7.21 (m, 2H),
6.67 (d, J = 16.0 Hz, 1H), 6.50 (d, J = 16.0, 6.8 Hz, 1H), 5.88 (d, J = 6.8
Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 148.1, 140.4, 136.7, 134.9,
134.3, 132.8, 130.1, 130.0, 128.9, 128.7, 128.2, 128.1, 127.5, 127.0, 126.9,
125.6, 86.4. Anal. Calcd for C22H18ClNO: C, 75.97; H, 5.22; N, 4.03.
Found: C, 75.93; H, 5.28; N, 4.02.
2-Methylbenzaldehyde O-[(1S,2E)-1,3-Diphenyl-2-propen-
1-yl]oxime (Table 2, entry 5). Colorless oil, [R]20D +32.1 (c 0.39,
CH2Cl2) (94% ee); IR (film) 1494, 1453, 1292 cmꢀ1; 1H NMR (400
MHz, CDCl3) δ 8.56 (s, 1H), 7.73 (d, J = 7.6 Hz, 1H), 7.56 (d, J = 7.2
Hz, 2H), 7.51ꢀ7.43 (m, 4H), 7.42ꢀ7.33 (m, 3H), 7.30 (t, J = 7.2 Hz,
2H), 7.23 (dd, J = 8.0, 7.6 Hz, 2H), 6.77 (d, J = 16.0 Hz, 1H), 6.61 (dd,
J = 16.0, 6.8 Hz, 1H), 5.98 (d, J = 6.8 Hz, 1H), 2.46 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 148.5, 140.6, 137.0, 136.8, 132.7, 131.0, 130.6,
129.7, 129.2, 128.7, 128.6, 128.1, 128.0, 127.6, 127.3, 126.9, 126.2, 86.1,
20.2. Anal. Calcd for C23H21NO: C, 84.37; H, 6.46; N, 4.28. Found: C,
84.45; H, 6.56; N, 4.17.
Propiophenone O-[(1S,2E)-1,3-Diphenyl-2-propen-1-yl]o-
xime (Table 2, entry 9). White solid, mp 63ꢀ64 °C, [R]20D +28.3
(c 0.96, CH2Cl2) (94% ee); IR (film) 1494, 1449, 1339, 1300 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 7.67ꢀ7.61 (m, 2H), 7.49 (d, J = 7.2 Hz,
2H), 7.47ꢀ7.38 (m, 4H), 7.38ꢀ7.30 (m, 6H), 7.26 (dd, J = 8.0, 6.4 Hz,
1H), 6.69 (d, J = 16.0 Hz, 1H), 6.54 (dd, J = 16.0, 6.4 Hz, 1H), 5.93 (d,
J = 6.4 Hz, 1H), 2.89 (q, J = 7.6 Hz, 2H), 1.23 (t, J = 7.6 Hz, 3H); 13C
NMR (100 MHz, CDCl3) δ 160.2, 141.2, 137.0, 135.9, 132.1, 129.9,
129.2, 128.7, 128.6, 127.9, 127.8, 127.4, 126.9, 126.6, 85.9, 20.6, 11.4.
Anal. Calcd for C24H23NO: C, 84.42; H, 6.79; N, 4.10. Found: C, 84.03;
H, 6.71; N, 4.10.
Benzophenone O-[(1S,2E)-1,3-Diphenyl-2-propen-1-yl]o-
xime (Table 2, entry 10). Colorless oil, [R]20D ꢀ2.6 (c 0.27, CH2-
Cl2) (92% ee); IR (film) 1600, 1494, 1445, 1327, 1301 cmꢀ1; 1H NMR
(400 MHz, CDCl3) δ 7.61ꢀ7.51 (m, 7H), 7.51ꢀ7.35 (m, 12 H), 7.31
(dd, J = 7.6, 7.2 Hz, 1H), 6.72 (d, J = 16.0 Hz, 1H), 6.55 (dd, J = 16.0, 6.8
Hz, 1H), 6.07 (d, J = 6.8 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ
157.4, 141.0, 136.9, 136.8, 133.7, 132.1, 129.6, 129.4, 128.9, 128.7, 128.5,
128.3, 128.2, 128.1, 127.9, 127.8, 127.3, 126.8, 86.4; HRMS (FT-
ICRMS) calcd for C28H24NO (M + H+) 390.1850, found 390.1847.
1-(4-Methylphenyl)ethanone O-[(1S,2E)-1,3-Diphenyl-2-
propen-1-yl]oxime (Table 2, entry 11). White solid, mp 105ꢀ
107 °C, [R]20D +46.6 (c 0.67, CH2Cl2) (94% ee); IR (film) 1514, 1494,
1449, 1367, 1316 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 7.51 (d, J = 8.0
Hz, 2H), 7.46 (d, J = 8.0 Hz, 2H), 7.43ꢀ7.35 (m, 4H), 7.34ꢀ7.27 (m,
3H), 7.23 (dd, J = 7.2, 6.8 Hz, 1H), 7.14 (d, J = 8.0 Hz, 2H), 6.65 (d, J =
16.0 Hz, 1H), 6.51 (dd, J = 16.0, 6.4 Hz, 1H), 5.90 (d, J = 6.4 Hz, 1H),
2.34 (s, 3H), 2.33 (s, 3H); 13C NMR (100 MHz, CDCl3) δ 155.2, 141.2,
139.2, 137.0, 134.1, 132.1, 129.9, 129.2, 128.7, 128.6, 127.9, 127.8, 127.4,
126.9, 126.2, 85.8, 21.4, 13.3. Anal. Calcd for C24H23NO: C, 84.42; H,
6.79; N, 4.10. Found: C, 84.09; H, 6.92; N, 4.20.
2-Chlorobenzaldehyde O-[(1S,2E)-1,3-Diphenyl-2-propen-
1-yl]oxime (Table 2, entry 6). Colorless oil, [R]20D +22.2 (c 0.56,
CH2Cl2) (92% ee); IR (film) 1600, 1494, 1471, 1449 cmꢀ1; 1H NMR
(400 MHz, CDCl3) δ 8.65 (s, 1H), 7.85 (d, J = 7.6 Hz, 1H), 7.48 (d, J =
7.6 Hz, 2H), 7.45ꢀ7.38 (m, 4H), 7.38ꢀ7.29 (m, 4H), 7.29ꢀ7.24
1-(4-Chlorophenyl)ethanone O-[(1S,2E)-1,3-Diphenyl-2-
propen-1-yl]oxime (Table 2, entry 12). White solid, mp 129ꢀ
130 °C, [R]20D +46.1 (c 0.59, CH2Cl2) (94% ee); IR (film) 1492, 1449,
1
1398, 1367, 1313 cmꢀ1; H NMR (400 MHz, CDCl3) δ 7.58 (d, J =
8.4 Hz, 2H), 7.49 (d, J = 7.2 Hz, 2H), 7.46ꢀ7.38 (m, 4H), 7.38ꢀ7.30
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NOTE
(m, 5H), 7.26 (dd, J = 7.6, 6.8 Hz, 1H), 6.69 (d, J = 16.0 Hz, 1H), 6.54 (d,
J = 16.0, 6.4 Hz, 1H), 5.93 (d, J = 6.4 Hz, 1H), 2.34 (s, 3H); 13C NMR
(100 MHz, CDCl3) δ 154.1, 141.0, 136.9, 135.3, 135.2, 132.3, 129.6,
128.7, 128.6, 128.5, 128.0, 127.9, 127.6, 127.4, 126.9, 86.2, 13.1. Anal.
Calcd for C23H20ClNO: C, 76.34; H, 5.57; N, 3.87. Found: C, 76.38; H,
5.61; N, 3.74.
1-(1-Naphthalenyl)ethanone O-[(1S,2E)-1,3-Diphenyl-2-
propen-1-yl]oxime (Table 2, entry 13). Colorless oil, [R]20D +23.0
(c 0.50, CH2Cl2) (93% ee); IR (film) 1494, 1449, 1364, 1301 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 7.92 (d, J = 8.4 Hz, 1H), 7.82 (d, J = 8.0 Hz,
2H), 7.52 (d, J = 7.2 Hz, 2H), 7.48ꢀ7.39 (m, 7H), 7.39ꢀ7.30 (m, 3H),
7.30ꢀ7.23 (m, 2H), 6.72 (d, J = 16.0 Hz, 1H), 6.58 (dd, J = 16.0, 6.4 Hz,
1H), 5.96(d,J= 6.4 Hz, 1H), 2.47 (s, 3H); 13C NMR (100 MHz, CDCl3) δ
157.1, 141.2, 136.9, 135.5, 134.0, 132.6, 131.0, 129.7, 129.2, 128.8, 128.7,
128.4, 128.0, 127.5, 126.9, 126.6, 126.2, 126.1, 125.9, 125.2, 85.9, 17.8;
HRMS (FT-ICRMS) calcd for C27H24NO (M + H+) 378.1852, found
378.1857.
7.2 Hz, 1H), 7.56 (dd, J = 7.6, 1.6 Hz, 2H), 7.47 (dd, J = 8.0, 7.6 Hz,
2H), 7.39ꢀ7.32 (m, 3H), 7.31ꢀ7.24 (m, 7H), 7.24ꢀ7.16 (m, 3H), 6.48
(d, J = 16.0 Hz, 1H), 6.28 (dd, J = 16.0, 6.8 Hz, 1H), 5.86 (d, J = 6.8 Hz,
1H); 13C NMR (100 MHz, CDCl3) δ 194.3, 156.6, 140.2, 136.6, 135.0,
134.4, 132.4, 131.5, 130.5, 129.6, 129.1, 128.9, 128.7, 128.5, 128.0, 127.9,
127.3, 126.8, 126.7, 87.0; HRMS (FT-ICRMS) calcd for C29H24NO2 (M +
H+) 418.1802, found 418.1795.
Benzaldehyde O-[(1S,2E)-1,3-Di(4-methylphenyl)-2-pro-
pen-1-yl]oxime (Table 2, entry 19). White solid, mp 121ꢀ
123 °C, [R]20 +27.8 (c 0.54, CH2Cl2) (89% ee); IR (film) 1513,
D
1447, 1300, 1210 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 8.22 (s, 1H),
7.62ꢀ7.55 (m, 2H), 7.41ꢀ7.30 (m, 7H), 7.22 (d, J = 7.6 Hz, 2H), 7.13
(d, J = 8.0 Hz, 2H), 6.66 (d, J = 16.0 Hz, 1H), 6.48 (dd, J = 16.0, 6.8 Hz,
1H), 5.87 (d, J = 6.8 Hz, 1H), 2.38 (s, 3H), 2.35 (s, 3H); 13C NMR (100
MHz, CDCl3) δ 149.3, 137.8, 137.7, 134.1, 132.6, 132.4, 129.9, 129.4,
129.3, 128.8, 128.3, 127.6, 127.3, 126.8, 86.1, 21.4; HRMS (FT-ICRMS)
calcd for C24H24NO (M + H+) 342.1852, found 342.1853.
1-Indanone O-[(1S,2E)-1,3-Diphenyl-2-propen-1-yl]oxime
Benzaldehyde O-[(1S,2E)-1,3-Di(3-chlorolphenyl)-2-pro-
(Table 2, entry 14). White solid, mp 106ꢀ108 °C, [R]20 +37.1
pen-1-yl]oxime (Table 2, entry 20). Colorless oil, [R]20 +27.2
D
D
(c 1.18, CH2Cl2) (91% ee); IR (film) 1595, 1569, 1475, 1428 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 8.22 (s, 1H), 7.59ꢀ7.54 (m, 2H), 7.44 (s,
1H), 7.40 (s, 1H), 7.38ꢀ7.33 (m, 3H), 7.33ꢀ7.27 (m, 3H), 7.27ꢀ7.20
(m, 3H), 6.61 (d, J = 16.0 Hz, 1H), 6.45 (dd, J = 16.0, 6.4 Hz, 1H), 5.83
(d, J = 6.4 Hz, 1H); 13C NMR (100 MHz, CDCl3) δ 149.9, 142.5, 138.4,
134.8, 134.7, 132.2, 131.6, 130.2, 130.04, 130.01, 130.0, 128.9, 128.3,
128.1, 127.6, 127.4, 126.8, 125.6, 125.1, 85.1. Anal. Calcd for
C22H17Cl2NO: C, 69.12; H, 4.48; N, 3.66. Found: C, 69.14; H, 4.36;
N, 3.81.
(c 0.58, CH2Cl2) (95% ee); IR (film) 1494, 1473, 1464, 1449, 1337,
1299 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 7.74 (d, J = 7.6 Hz, 1H),
7.54 (d, J = 7.6 Hz, 2H), 7.49ꢀ7.41 (m, 4H), 7.39ꢀ7.31 (m, 5H),
7.31ꢀ7.23 (m, 2H), 6.73 (d, J = 16.0 Hz, 1H), 6.59 (dd, J = 16.0, 6.8 Hz,
1H), 5.96 (d, J = 6.8 Hz, 1H), 3.15ꢀ3.00 (m, 4H); 13C NMR (100 MHz,
CDCl3) δ 163.4, 148.4, 141.3, 137.0, 136.5, 132.1, 130.3, 129.9, 128.7,
128.6, 127.9, 127.8, 127.3, 127.0, 126.8, 125.6, 122.0, 85.8, 28.8, 27.0.
Anal. Calcd for C24H21NO: C, 84.92; H, 6.24; N, 4.13. Found: C, 84.51;
H, 6.34; N, 4.21.
1-Tetralone O-[(1S,2E)-1,3-Diphenyl-2-propen-1-yl]oxime
(Table 2, entry 15). White solid, mp 67ꢀ68 °C, [R]20D +41.3 (c 0.46,
CH2Cl2) (96% ee); IR (film) 1494, 1451, 1438, 1329, 1300 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 8.07 (d, J = 8.0 Hz, 1H), 7.58 (d, J = 7.6 Hz,
2H), 7.54ꢀ7.44 (m, 4H), 7.43ꢀ7.34 (m, 3H), 7.31 (t, J = 7.6 Hz, 2H),
7.24 (dd, J = 7.2, 6.8 Hz, 1H), 7.19 (d, J = 7.2 Hz, 1H), 6.77 (d, J = 16.0
Hz, 1H), 6.63 (dd, J = 16.0, 6.4 Hz, 1H), 6.02 (d, J = 6.4 Hz, 1H),
3.06ꢀ2.91 (m, 2H), 2.87ꢀ2.80 (m, 2H), 1.99ꢀ1.91 (m, 2H); 13C NMR
(100 MHz, CDCl3) δ 154.5, 141.2, 139.6, 136.9, 132.1, 131.0, 129.9,
129.1, 128.7, 128.6, 128.5, 127.9, 127.8, 127.3, 126.8, 126.4, 124.6, 85.9,
29.9, 24.9, 21.6. Anal. Calcd for C25H23NO: C, 84.95; H, 6.56; N, 3.96.
Found: C, 84.94; H, 6.56; N, 4.04.
Benzaldehyde O-Cyclohex-2-enyl Oxime (Table 2, entry
21). Colorless oil, [R]20D ꢀ72.2 (c 0.38, CH2Cl2) (33% ee); IR (film)
1447, 1309 cmꢀ1 1H NMR (400 MHz, CDCl3) δ 8.11 (s, 1H),
;
7.61ꢀ7.58 (m, 2H), 7.40ꢀ7.35 (m, 3H), 6.02ꢀ5.96 (m, 1H),
5.92ꢀ5.88 (m, 1H), 4.74 (brs, 1H), 2.15ꢀ2.07 (m, 1H), 2.06ꢀ1.96
(m, 1H), 1.96ꢀ1.90 (m, 2H), 1.84ꢀ1.74 (m, 1H), 1.68ꢀ1.52 (m, 1H);
13C NMR (100 MHz, CDCl3) δ 148.6, 132.9, 132.6, 129.8, 128.8, 127.2,
126.6, 76.7, 28.5, 25.5, 18.9; HRMS (FT-ICRMS) calcd for C13H16NO
(M + H+) 202.1226, found 202.1229.
Procedure for the Synthesis of Chiral Amine from Oxime
Ether. To a solution of the oxime ether 3a (0.0939 g, 0.3 mmol, >99%
ee) in MeOH/EtOAc (3.0 mL, v/v = 1/1) was added PtO2 H2O
3
Ethyl-2-[(10S,20E)-10,30-diphenyl-20-propen-10-yloxyimino-
]propanoate (Table 2, entry 16). White solid, mp 47ꢀ49 °C,
(0.0037 g, 5 mol %) under H2 atmosphere, and the resulting mixture was
stirred at room temperature for 4 h. Then the mixture was filtered,
washed with ethyl ether (10 mL), dried over MgSO4, filtered, and con-
centrated. The residue was dissolved in toluene (1.5 mL) and cooled
[R]20 ꢀ2.4 (c 0.51, CH2Cl2) (88% ee); IR (film) 1717, 1495, 1450,
D
1367, 1319 cmꢀ1; 1H NMR (400 MHz, CDCl3) δ 7.45ꢀ7.37 (m, 6H),
7.37ꢀ7.30 (m, 3H), 7.26 (dd, J = 7.6, 6.8 Hz, 1H), 6.64 (d, J = 16.0 Hz,
1H), 6.49 (dd, J = 16.0, 6.8 Hz, 1H), 6.04 (d, J = 6.8 Hz, 1H), 4.31 (q, J =
7.2 Hz, 2H), 2.19 (s, 3H), 1.34 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz,
CDCl3) δ 164.0, 149.9, 140.0, 136.5, 132.9, 128.7, 128.6, 128.5, 128.2,
128.1, 127.3, 126.9, 87.3, 61.9, 14.3, 12.1. Anal. Calcd for C20H21NO3:
C, 74.28; H, 6.55; N, 4.33. Found: C, 74.17; H, 6.58; N, 4.21.
to ꢀ78 °C. BF3 Et2O (0.1278 g, 0.9 mmol, 3 equiv) was then added
3
dropwise, and the mixture was stirred for 10 min before nBuLi (0.36 mL,
0.9 mmol, 3 equiv, 2.5 M in hexanes) was added dropwise. The resulting
mixture was continued to stir for 2 h at this temperature before water
(1.0 mL) was added to quench the reaction. The mixture was then
extracted with ethyl ether (5 mL ꢁ 3), and the organic phase was dried
over MgSO4, filtered, and concentrated. The crude residue was purified
by flash chromatography on silica gel (petroleum ether/ethyl ether =
20:1, v/v) to afford the desired product 9 as a colorless oil (0.0728 g,
65% for 2 steps, >20/1 dr).
2-[(10S,20E)-10,30-Diphenyl-20-propen-10-yloxyimino]buta-
n-2-one (Table 2, entry 17). Colorless oil, [R]20 ꢀ6.4 (c 0.72,
D
CH2Cl2) (83% ee); IR (film) 1694, 1604, 1495, 1450, 1359, 1304 cmꢀ1
;
1H NMR (400 MHz, CDCl3) δ 7.49ꢀ7.40 (m, 6H), 7.39ꢀ7.32 (m,
3H), 7.28 (dd, J = 7.6, 7.2 Hz, 1H), 6.69 (d, J = 16.0 Hz, 1H), 6.53 (d, J =
16.0, 6.8 Hz, 1H), 5.95 (d, J = 6.8 Hz, 1H), 2.36 (s, 3H), 2.05 (s, 3H);
13C NMR (100 MHz, CDCl3) δ 196.9, 156.1, 140.0, 136.5, 133.1, 128.8,
128.7, 128.5, 128.3, 128.2, 127.4, 126.9, 87.5, 25.2, 9.2. Anal. Calcd for
C19H19NO2: C, 77.79; H, 6.53; N, 4.77. Found: C, 78.02; H, 6.50;
N, 4.74.
(1S,10S)-N-(10,30-Diphenylpropan-10-oxy)-1-phenylpentan-
1-amine (9). [R]20 ꢀ51.0 (c 0.49, CH2Cl2); IR (film) 1494,
D
1
1454 cmꢀ1; H NMR (400 MHz, CDCl3) δ 7.40ꢀ7.10 (m, 15H),
5.38 (brs, 1H), 4.60 (dd, J = 7.6, 6.0 Hz, 1H), 3.98 (dd, J = 8.8, 5.6 Hz,
1H), 2.80ꢀ2.66 (m, 1H), 2.66ꢀ2.53 (m, 1H), 2.30ꢀ2.10 (m, 1H),
2.00ꢀ1.80 (m, 2H), 1.75ꢀ1.55 (m, 1H), 1.40ꢀ1.05 (m, 4H), 0.88 (t,
J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 142.7, 142.2, 141.9,
128.6, 128.5, 128.4, 128.3, 128.0, 127.6, 127.5, 127.0, 125.9, 84.8, 65.9,
37.9, 33.7, 32.4, 28.5, 22.9, 14.2; HRMS (FT-ICRMS) calcd for
C26H32NO (M + H+) 374.2478, found 374.2470.
2-[(10S,20E)-10,30-Diphenyl-20-propen-10-yloxyimino]-1,2-
diphenylethanone (Table 2, entry 18). Colorless oil, [R]20D ꢀ12.1
(c 0.37, CH2Cl2) (91% ee); IR (film) 1681, 1597, 1494, 1449 cmꢀ1; 1H
NMR (400 MHz, CDCl3) δ 7.94 (d, J = 7.2 Hz, 2H), 7.62 (dd, J = 7.6,
6405
dx.doi.org/10.1021/jo200925q |J. Org. Chem. 2011, 76, 6401–6406

The Journal of Organic Chemistry
NOTE
To a solution of 9 (0.0597 g, 0.16 mmol) in HOAc/H2O (1.0 mL,
v/v = 1/1) was added zinc dust (0.4160 g, 6.4 mmol), and the resulting
mixture was stirred at 50 °C for 5 h. Then the mixture was filtered and
washed with H2O (2 mL) and EtOAc (5 mL), the organic phase was
separated, and the aqueous layer was extracted with EtOAc (5 mL ꢁ 2).
The combined organic solution was dried over MgSO4, filtered and
concentrated. The crude residue was purified by flash chromatography
on silica gel (petroleum ether/ethyl ether = 10:1 to 5:1, v/v) to afford
the desired alcohol product 10 as a white solid (0.0237 mg, 70%
yield, >99% ee). The aqueous layer was neutralized with saturated
NaHCO3 aqueous solution and extracted with CH2Cl2 (5 mL ꢁ 3). The
organic phase was dried over MgSO4, filtered, and concentrated to give
amine 11 as a colorless oil (0.0180 g, 69% yield, 96% ee).
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(1S)-1,3-Diphenylpropan-1-ol (10). [R]20 ꢀ27.1 (c 0.52,
D
CHCl3) (>99% ee) [[R]20 +13.4 (c 0.22, CHCl3) 47% ee for
D
R-isomer49]; 1H NMR (400 MHz, CDCl3) δ 7.40ꢀ7.33 (m, 4H),
7.33ꢀ7.24 (m, 3H), 7.24ꢀ7.15 (m, 3H), 4.70 (dd, J = 6.8, 5.6 Hz, 1H),
2.82ꢀ2.63 (m, 2H), 2.22ꢀ2.11 (m, 1H), 2.11ꢀ1.98 (m, 1H), 1.92 (brs,
1H); 13C NMR (100 MHz, CDCl3) δ 144.8, 142.0, 128.7, 128.6, 128.5,
127.8, 126.1, 126.0, 74.1, 40.7, 32.3.
(S)-1-Phenylpentan-1-amine (11). [R]20 ꢀ23.6 (c 0.64,
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CH2Cl2) (96% ee) [[R]27 ꢀ17.4 (c 1.9, CH2Cl2) 94% ee for
D
1
S-isomer50]; H NMR (400 MHz, CDCl3) δ 7.38ꢀ7.20 (m, 5H),
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0.87 (t, J = 7.2 Hz, 3H); 13C NMR (100 MHz, CDCl3) δ 147.1, 128.6,
127.0, 126.5, 56.5, 39.6, 29.0, 22.9, 14.2.
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’ ASSOCIATED CONTENT
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S
Supporting Information. Data for the determination of
b
enantiomeric excess and X-ray data for 3l in CIF format, along
with NMR spectra. This material is available free of charge via the
Internet at http://pubs.acs.org.
’ AUTHOR INFORMATION
Corresponding Author
*E-mail: haifengdu@iccas.ac.cn.
(34) Defieber, C.; Ariger, M. A.; Moriel, P.; Carreira, E. M. Angew.
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’ ACKNOWLEDGMENT
The authors are thankful for financial support from the
National Science Foundation of China (20802079, 21072194),
the National Basic Research Program of China (2010CB833
300), and the Scientific Research Foundation for the Returned
Overseas Chinese Scholars.
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