Fe(III) catalyzed enantioselective hydrophosphonylation of aldehydes promoted by chiral camphor Schiff bases

Article abstract of DOI:10.1016/j.tetasy.2015.07.004

Abstract Five novel chiral camphor Schiff bases were designed. Schiff base L₃ showed high efficiency in Fe(III)-catalyzed asymmetric hydrophosphonylations of aldehydes, giving the corresponding products in high yields (up to 91%) along with mod

Full text of DOI:10.1016/j.tetasy.2015.07.004

Tetrahedron: Asymmetry xxx (2015) xxx–xxx
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Tetrahedron: Asymmetry
journal homepage: www.elsevier.com/locate/tetasy
Fe(III) catalyzed enantioselective hydrophosphonylation
of aldehydes promoted by chiral camphor Schiff bases
⇑
⇑
Feng Xu , Yanpeng Liu, Jingxuan Tu, Chao Lei, Gaoqiang Li
Key Laboratory of Macromolecular Science of Shaanxi Province, School of Chemistry & Chemical Engineering, Shaanxi Normal University, Xi’an, Shaanxi 710062, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
Five novel chiral camphor Schiff bases were designed. Schiff base L3 showed high efficiency in
Fe(III)-catalyzed asymmetric hydrophosphonylations of aldehydes, giving the corresponding products
in high yields (up to 91%) along with moderate to good enantioselectivities (up to 82%).
Ó 2015 Elsevier Ltd. All rights reserved.
Received 15 May 2015
Accepted 7 July 2015
Available online xxxx
1. Introduction
base and its complex. Clearly, the development of new efficient
and practical catalytic systems for asymmetric hydrophosphonyla-
In recent years, the importance of
a
-hydroxyphosphonates has
tion reaction is still a highly challenging topic.
From natural chiral sources, -(+)-camphor often plays an
been well-recognized due to their biological activities. These com-
pounds have been widely applied in medicine and biochemistry, as
antibacterial agents, enzymes renin, thrombin, and anti-HIV
agents.1 Since the biological activity of these compounds is strongly
D
important role in the asymmetric organic synthesis, in terms of
its low-cost, easy-purification, and rigid structure.12 Chiral
camphor and its metal complexes have been shown to be highly
efficient in many asymmetric reactions. We have paid much atten-
tion to modifying the chiral camphor frame. On the other hand,
iron has unique properties, compared with rare metals and some
sensitive metal salts, which are frequently used in asymmetric
hydrophosphonylation reactions, such as being inexpensive,
non-toxic, more abundant, and environmentally friendly. The
development of iron catalysts is a primary long term goal in syn-
thetic organic chemistry. Iron based catalysts are under-utilized
in organic synthesis, especially in the field of asymmetric synthe-
sis.13 Therefore, the development of an iron complex with new
chiral camphor derivatives for the synthesis of optically active
related to the absolute configuration of the
unit, it is notsurprising thatgreat efforts have focused onthe synthe-
sis of chiral
-hydroxyphosphonates derivatives.2 The catalytic
asymmetric hydrophosphonylation of aldehydes is one of the most
powerful strategies for the synthesis of -hydroxyphosphonates.
a-hydroxyphosphonates
a
a
Therefore, the development of new catalytic systems for the
asymmetric hydrophosphonylation of aldehyde3 has become a core
work of this procedure.
Wynberg et al. first reported the preparation of enantiomeri-
cally enriched
a-hydroxyphosphonates using amino alcohol as a
catalyst.4 Since this pioneering work, various catalytic systems,
including organic molecules and chiral metal complexes, have
been developed. The first transition metal catalyzed asymmetric
hydrophosphonylation was discovered by Shibuya et al.5
Shibasaki et al. reported the first highly enantioselective
hydrophosphonylation of aldehydes using hetero-bimetallic com-
plexes as catalysts.6 Subsequently, a breakthrough was achieved
with the C1-symmetric [Al-(salalen)] complex by Katsuki et al.7
Excellent results were also observed by Yamamoto et al.,8 Feng
et al.9 and other groups.10 Recently, the squaramine used to pro-
mote enantioselective hydrophosphonylation reactions was
reported by Herrera et al..11
a-hydroxyphosphonates is a reasonable target.
Chen et al. reported on the camphor-based tridentate Schiff base
SBAIB ligands,14 which were used in the asymmetric hydrophos-
phonylation of aldehydes to afford
a-hydroxyphosphonates with
high yields and good enantioselectivities.14c Inspired by this
result and pursuit our interest in the development of cost
effective and accessible catalysts based on the chiral camphor for
the asymmetric catalytic synthesis, we herein report the synthesis
of an unusual chiral camphor iron complex and its application as
a catalyst in asymmetric hydrophosphonylation of aldehydes for
the synthesis of optically active a-hydroxyphosphonates.
However, only limited types of chiral ligands have been suc-
cessfully utilized in this reaction, which is in contrast to the many
excellent chiral ligands and complexes, especially for chiral Schiff
2. Results and discussion
At first, (1S,2R,4R)-1-amino-7,7-dimethylbicyclo[2.2.1]hept-
⇑
an-2-ol was prepared according to the procedure reported by
Corresponding authors.
E-mail addresses: fengxu@snnu.edu.cn (F. Xu), gqli@snnu.edu.cn (G. Li).
http://dx.doi.org/10.1016/j.tetasy.2015.07.004
0957-4166/Ó 2015 Elsevier Ltd. All rights reserved.
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2
F. Xu et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
1: R1 = R2 = R3 = H;
L2: R1 = OCH3, R2 = R3 = H
L
OH
OH
R3
N
R1
R2
OHC
Na2SO4
reflux
3: R1 = CH3, R2 = R3 = H
L
OH
OH
R1
H2N
L4: R1 = R3 = t-Bu, R2 = H
R3
5: R1 = R3 = H, R2 = OH
L
R2
Scheme 1. Synthesis of chiral camphor Schiff bases.
Yan et al.15 As shown in Scheme 1, the new Schiff bases L1–L5 were
prepared from (1S,2R,4R)-1-amino-7,7-dimethylbi-cyclo[2.2.1]
heptan-2-ol by condensation with an appropriate commercially
available aldehyde in MeOH/CH2Cl2 (1:3, v/v) in the presence of
anhydrous Na2SO4 at reflux.
With the chiral camphor Schiff bases in hand, the asymmetric
induced properties were initially examined in the hydrophosphony-
lation of benzaldehyde with diethyl phosphate in the presence of
sodium carbonate at room temperature in THF according to the lit-
erature.16 The catalytic metal salt was fixed to FeCl3 and kept in a 1:1
ratio to Schiff based as Sekar’s results. The experimental results are
listed in Table 1. Iron trichloride cooperated with chiral camphor
Schiff bases L3 to give diethyl hydroxy(phenyl)methyl phosphonate
with the highest yield (85%) and ee (76%) among the Schiff bases
L1–L5. This implied that the Schiff bases L3 cooperated with iron
trichloride and was most powerful for the model reaction. The
optimization of reaction conditions then focused on Fe promoted
by chiral camphor Schiff bases L3 as the catalyst for model reaction.
Table 2
Effects of solvent on the asymmetric hydrophosphonylation reaction under the chiral
Schiff base L3 and FeCl3
a
O
OH
L
FeCl3,
3
*
H
O
OEt
OEt
OEt
OEt
Na2CO3
H
P
P
O
solvent, rt, 24h
1a
2a
3aa
Entry
Solvent
Yieldb (%)
eec (%)
1
2
3
4
5
6
7
8
9
THF
DCM
DCE
Toluene
Dioxane
CHCl3
EtOH
CH3CN
DMF
85
83
35
75
58
80
60
65
54
76
59
51
64
66
62
28
61
50
a
Reaction conditions: benzaldehyde 1a (53 mg, 0.5 mmol), diethyl phosphate 2a
(76 mg, 0.55 mmol), FeCl3 (8 mg, 10 mol %), L3 (14 mg, 10 mol %), Na2CO3 (53 mg,
Table 1
a
0.5 mmol), solvent (5 mL), under N2.
Screen asymmetric induced properties of the chiral Schiff bases L1–L5
b
Isolated yields.
Determined by HPLC analysis (Chiracel OD-H).
c
O
OH
L
FeCl3,
*
H
O
OEt
OEt
OEt
OEt
Na2CO3
H
P
P
O
THF, rt, 24h
1a
2a
3aa
Table 3
Effects of base on the asymmetric hydrophosphonylation reaction catalyzed by the
chiral Schiff base L3 and FeCl3
a
Entrya
L (mol %)
Yieldb (%)
eec (%)
1
2
3
4
5
L1 (10)
L2 (10)
L3 (10)
L4 (10)
L5 (10)
77
80
85
82
75
20
17
76
70
11
O
OH
*
L
FeCl3,
Base
3
OEt
OEt
H
O
OEt
OEt
H
P
P
O
THF, rt
3aa
1a
2a
a
Reaction conditions: benzaldehyde 1a (53 mg, 0.5 mmol), diethyl phosphate 2a
(76 mg, 0.55 mmol), FeCl3 (8 mg, 10 mol %),
0.5 mmol), THF (5 mL), under N2.
L (10 mol %), Na2CO3 (53 mg,
Entry
Base
Time (h)
Yieldb (%)
eec (%)
b
1
2
3
4
5
6
7
8
Na2CO3
NaHCO3
K2CO3
Na2SO3
K3PO4
DABCO
TEA
DBU
24
24
24
24
24
24
24
24
24
24
24
30
15
85
87
77
56
40
82
75
70
73
80
85
71
86
76
80
12
63
33
73
74
11
72
76
75
70
59
Isolated yields.
Determined by HPLC analysis (Chiralcel OD-H).
c
The reaction solvent is an important factor with regards to
chemical reactions. Several solvents were chosen to test the sol-
vent factor for the asymmetric hydrophosphonylation reaction cat-
alyzed by chiral Schiff base L3 and FeCl3 (Table 2, entries 1–9).
Among the different solvents, THF was established as the best
choice for this reaction system (Table 2, entry 1, 85% yield, 76% ee).
Next, the effects of various bases were examined using chiral
Schiff base L3 and FeCl3 as the catalyst. Inorganic bases and organic
bases were tested in THF. The results are summarized in Table 3. It
can be seen that NaHCO3 (one equivalent) provided the product with
anexcellent yield(87%) and enantioselectivity (80%), which was bet-
ter than other bases for the model reaction. Moreover, the amount of
NaHCO3 was changed from 0.5–1.5 equiv in the hydrophosphonyla-
tion reaction (Table 3, entries 2, 10, and 11). The results indicated
that an excess of NaHCO3 did not improve the chemical yield or
the enantiomeric excess. The temperature effect was also explored
9
DIPEA
10d
11e
12f
13g
NaHCO3
NaHCO3
NaHCO3
NaHCO3
a
Reaction conditions: benzaldehyde 1a (53 mg, 0.5 mmol), diethyl phosphate 2a
(76 mg, 0.55 mmol), FeCl3 (8 mg, 10 mol %), L3 (14 mg, 10 mol %), Base (0.5 mmol),
THF (5 mL), under N2.
b
Isolated yields.
Determined by HPLC analysis (Chiracel OD-H).
0.5 equiv NaHCO3 was used.
1.5 equiv NaHCO3 was used.
Reaction temperature was 0 °C.
Reaction temperature was 55 °C.
c
d
e
f
g
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F. Xu et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
3
Table 4
After the optimal reaction conditions were established, the
asymmetric hydrophosphonylation reaction was performed
between diethyl phosphate and aldehydes under the optimized
reaction conditions. The results are summarized in Table 5. The aro-
matic aldehydes underwent the asymmetric hydrophosphonylation
reaction smoothly with good chemical yields and enantiomeric
excess values with electron-withdrawing and electron-donating
groups. 1-Naphthaldehyde also successfully afforded the desired
product in good yield and with acceptable enantioselectivity.
Although aliphatic aldehyde smoothly generated the phosphate,
the enantioselectivity decreased sharply. The absolute configura-
Influence of catalyst loading on the asymmetric hydrophosphonylation reaction
catalyzed by chiral Schiff base L3 and FeCl3 and the performance of different
disubstituted phosphitesa
O
OH
*
L
FeCl3,
NaHCO33
H
O
OR
OR
OR
OR
H
P
P
THF, rt, 24h
O
2a-d
1a
3
2a
2c
2b
: R= Et; : R= Me;
2d
: R= Bu;
: R= Ph.
tions of all
a-hydroxyphosphonates with a known absolute
Entry
R
L3 (mol %)
FeCl3 (mol %)
Yieldb (%)
eec (%)
configuration in the literature, produced by our procedure, had an
(S)-configuration. However, Chen’s result14c gave (R)-absolute
configuration products based on the iron complex of SBAIB ligand,
which is a camphor based Schiff base derived from the 3-amino
group of (1R,2S,3R)-3-amino-1,7,7-trimethylbicyclo[2.2.1]hep-
tan-2-ol. This means a combination of our catalytic system and
Chen’s system will produce either an (S) or (R) absolute
configuration a-hydroxyphosphonates as desired.
A key intermediate for the explanation of the absolute configu-
rations of the obtained phosphonates is given in Scheme 2 on the
1
2
3
4
5
6
7
Et
Et
Et
Et
Me
Bu
Ph
5
10
20
30
10
10
10
5
10
20
30
10
10
10
86
87
87
85
68
73
nr
78
80
76
74
79
75
—
a
Reaction conditions: benzaldehyde 1a (53 mg, 0.5 mmol), diethyl phosphate 2
(0.55 mmol), NaHCO3 (42 mg, 0.5 mmol), THF (5 mL), under N2.
b
Isolated yields.
Determined by HPLC analysis (Chiracel OD-H).
c
(Table 3, entries 12 and 13). It was found that room temperature was
the best while increasing or decreasing the reaction temperature
resulted in a lower enantioselectivity. Subsequently, the effect of
the catalyst loading was examined and the results are shown in
Table 4. It was seen that 10 mol % was the optimal catalyst loading
(Table 4, entry 2). With the optimized reaction conditions in hand,
other disubstituted phosphites, such as dimethyl phosphite, dibutyl
phosphite, and diphenyl phosphite, were next evaluated (Table 4,
entries 5 and 6). All of the dialkyl phosphites smoothly gave the
desired products in good yield and enantioselectivity. Diethyl
phosphite showed the best performance (87% yield, 80% ee).
However, the diphenyl phosphite failed to generate any product in
this transformation and the reason was unclear.
O
N
O
EtO
O
P
Fe
EtO
O
Cl
O
Fe
O
N
H
Si-attack
π-π stacking
Scheme 2. A possible intermediate for the generation of phosphonate.
Table 5
a
Enantioselective hydrophosphonylation of various aldehydes catalyzed by chiral Schiff base L3 and FeCl3
FeCl3 (10 mol%)
OH
*
O
H
O
OEt
L
3 (10 mol%)
OEt
OEt
P
R
P
OEt NaHCO3 (1.0 equiv.)
THF, rt
R
H
O
3
1
2a
Entry
Aldehyde
Product
Time (h)
Yieldb (%)
eec (%)
Configurationd
1
2
3
4
5
6
7
8
PhCHO
3aa
3ab
3ac
3ad
3ae
3af
3ag
3ah
3ai
3aj
3ak
3al
3am
3an
3ao
3ap
3aq
24
24
24
24
23
23
21
24
10
11
13
20
20
15
15
20
24
87
86
85
82
84
83
85
81
90
91
89
83
80
85
83
80
73
80
80
79
76
79
78
72
78
74
72
71
75
81
82
79
63
41
(S)
(S)
—
4-MeOC6H4CHO
3-MeOC6H4CHO
2-MeOC6H4CHO
4-MeC6H4CHO
—
(S)
(S)
—
(S)
(S)
(S)
—
(S)
(S)
(S)
—
(S)
—
3-MeC6H4CHO
4-Me2NC6H4CHO
2,3,4-Trimethoxybenzaldehyde
4-FC6H4CHO
4-BrC6H4CHO
3-ClC6H4CHO
Thiophene-2-carboxaldehyde
5-Methylthiophene-2-carboxaldehyde
Cinnamaldehyde
9
10
11
12
13
14
15
16
17
a
-Methyl-trans-cinnamaldehyde
1-Naphthaldehyde
Phenylpropyl aldehyde
a
Reaction conditions: aldehyde 1 (0.5 mmol), diethyl phosphate 2 (76 mg, 0.55 mmol), FeCl3 (8 mg, 10 mol %), L3 (14 mg, 10 mol %), NaHCO3 (42 mg, 0.5 mmol), THF
(5 mL), under N2.
b
Isolated yields.
c
Determined by HPLC analysis (Chiralcel OD-H or Chiralpak AD columns).
Configuration was assigned on the basis of a thorough literature survey.
d
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4
F. Xu et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
basis of Chen’s proposed mechanism.14c The addition of the
phosphite group to the benzaldehyde occured on the si-face of
the benzaldehyde, since there was steric hindrance from the
bridge dimethyl group of the camphor moiety if the addition
occured on the re-face of the benzaldehyde. Thus phosphonates
with an (S)-absolute configuration were favored.
J = 7.8, 3.5 Hz, 1H), 2.38 (s, 1H), 2.28 (s, 3H), 2.09–1.87 (m, 5H),
1.33–1.23 (m, 5H), 0.85 (s, 3H); 13C NMR (101 MHz, CDCl3): d
164.9, 160.7, 133.5, 129.3, 126.5, 118.1, 117.8, 78.7, 77.4, 48.2,
43.6, 39.9, 28.0, 27.1, 20.0, 15.6; HRMS (ESI) [M+H]+ calcd for
C17H23NO2: 274.1802; found: 274.1807.
4.1.4. (1S,2R,4R)-1-((E)-3,5-Di-tert-butyl-2-hydroxybenzylidene-
amino)-7,7-dimethylbicyclo[2.2.1]heptan-2-ol L4
3. Conclusion
Yellow solid; yield 85%; mp 149–151 °C; [
a]
D
22 = À51.4 (c 1.0,
CHCl3); 1H NMR (400 MHz, CDCl3): d 13.97 (s, 1H), 8.46 (s, 1H),
7.40 (s, 1H), 7.14 (s, 1H), 3.86 (s, 1H), 2.15–1.88 (m, 6H), 1.45 (s,
9H), 1.32 (s, 9H), 1.30–1.25 (m, 5H), 0.86 (s, 3H); 13C NMR
(101 MHz, CDCl3): d 166.0, 158.6, 140.0, 137.1, 127.1, 126.2,
118.1, 78.8, 74.8, 48.1, 43.7, 39.8, 35.1, 34.2, 31.5, 29.5, 27.9,
27.1, 20.2, 19.9; HRMS (ESI) [M+H]+ calcd for C24H37NO2:
272.2897; found: 372.2906.
In conclusion, five novel chiral camphor-based Schiff bases
derived from the 1-amino group of (1S,2R,4R)-1-amino-7,7-
dimethyl-bicyclo[2.2.1]hep-tan-2-ol have been designed and
applied to form the corresponding Fe(III) complexes as catalysts
in the asymmetric hydrophosphonylation of aldehydes. Schiff base
L3 showed the best chirality induction ability. The electron-rich
and electron-deficient aromatic aldehydes were well tolerated in
the reaction system with good chemical yields and enantiomeric
4.1.5. 4-((E)-((1S,2R,4R)-2-Hydroxy-7,7-dimethylbicyclo[2.2.1]-
excess values. The absolute configurations of all
a-hydroxyphos-
heptan-1-ylimino)methyl)benzene-1,3-diol L5
phonates with a known absolute configuration in the literature
were (S), which is contrary to Chen’s results in which an (R)-config-
uration was observed using the camphor based Schiff base derived
from 3-amino group of (1R,2S,3R)-3-amino-1,7,7-trimetylbicyclo-
[2.2.1]heptan-2-ol. The application of these camphor-based Schiff
bases in other asymmetric reactions is currently under
investigation.
Yellow solid; yield 73%; mp 215–216 °C; [
a
]
22 = À175.1 (c 1.0,
D
CHCl3); 1H NMR (400 MHz, DMSO): d 14.63 (s, 1H), 9.87 (s, 1H),
8.26 (d, J = 5.9 Hz, 1H), 7.13 (d, J = 8.6 Hz, 1H), 6.11–5.98 (m, 2H),
5.25–5.23 (m, 1H), 3.78–3.75 (m, 1H), 1.94–1.76 (m, 5H), 1.31–
1.19 (m, 2H), 1.12 (s, 3H), 0.81 (s, 3H); 13C NMR (101 MHz,
DMSO): d 171.6, 163.0, 162.2, 134.2, 111.1, 105.9, 103.6, 75.6,
71.4, 47.3, 42.4, 40.4, 28.4, 26.6, 19.7; HRMS (ESI) [M+H]+ calcd
for C16H21NO3: 276.1594; found: 276.1599.
4. Experimental section
4.2. General procedure for synthesis of optically active
4.1. General procedure for synthesis of Schiff base ligands
a-hydroxyphosphonates
(1S,2R,4R)-1-Amino-7,7-dimethylbicyclo[2.2.1]heptan-2-ol
(5 mmol, 776 mg) was reacted with 2-hydroxy-1-aromaticaldehy-
des (5 mmol) in MeOH/CH2Cl2 (1:3, v/v) (8 mL) in the presence of
anhydrous Na2SO4 under a nitrogen atmosphere at room tempera-
ture. The reaction mixture was then stirred for 12 h. Subsequently,
filtration and concentration of the filtrate gave a residue, which was
purified by silica gel column chromatography (eluents: petroleum
ether/ethyl acetate = 6:1–1:2) to give the target product.
Dialkyl phosphite (0.55 mmol, 76 mg) and aldehyde (0.5 mmol)
were added to a THF (5 mL) solution of FeCl3 (10 mol %, 8 mg),
ligand L3 (10 mol %, 14 mg) and NaHCO3 (1.0 equiv, 42 mg) under
a nitrogen atmosphere. The reaction mixture was stirred for 10–
23 h at room temperature, then the solvents were evaporated to
give a residue. The final product was obtained by purification of
the residue using silica gel column chromatography (eluents: pet-
roleum ether/ethyl acetate = 2:1–1:7), which was characterized by
NMR for confirming the chemical structure and the chiral HPLC for
evaluating the enantiomeric excess using Chiralcel OD-H or
Chiralpak AD columns.
4.1.1. (1S,2R,4R)-1-(2-Hydroxybenzylideneamino)-7,7-
dimethyl-bicyclo[2.2.1]heptan-2-ol L1
Yellow solid; yield 75%; mp 99–101 °C; [
a]
D
22 = À110.8 (c 1.0,
CHCl3); 1H NMR (400 MHz, CDCl3): d 14.12 (s, 1H), 8.41 (s, 1H),
7.36–7.32 (m, 1H), 7.29–7.27 (m, 1H), 6.97 (d, J = 8.3 Hz, 1H),
6.88 (t, J = 7.4 Hz, 1H), 3.92–3.89 (m, 1H), 2.33 (s, 1H), 2.12–2.06
(m, 1H), 2.03–1.87 (m, 4H), 1.36–1.27 (m, 5H), 0.87 (s, 3H); 13C
NMR (101 MHz, CDCl3): d 164.6, 162.9, 132.7, 131.7, 118.8,
117.9, 78.6, 74.6, 48.3, 43.6, 39.9, 27.8, 27.1, 19.9; HRMS (ESI)
[M+H]+ calcd for C16H21NO2: 260.1645; found: 260.1643.
4.2.1. (S)-Diethyl hydroxy(phenyl)methylphosphonate 3aa9
White solid; mp 76.1–77.0 °C; 87% yield, 80% ee, HPLC (Chiralcel
OD-H,
n-hexane/i-PrOH,
95:5,
0.5 mL/min,
254 nm):
tR(minor) = 27.644 min, tR(major) = 33.914 min;
[
a]
D
22 = À28.3 (c
1.0, CHCl3) {lit.9
[
a]
D
20 = À39.7 (c 0.39, CHCl3)}; 1H NMR (400 MHz,
CDCl3): d 7.50–7.48 (m, 2H), 7.38–7.28 (m, 3H), 5.02 (dd, J = 10.9,
5.4 Hz, 1H), 4.09–3.98 (m, 4H), 1.28–1.20 (m, 6H).
4.1.2. (1S,2R,4R)-1-(2-Hydroxy-3-methoxybenzylideneamino)-
4.2.2. (S)-Diethyl hydroxy(4-methoxyphenyl)methylphosphonate
3ab9
7,7-dimethylbicyclo[2.2.1]heptan-2-ol L2
Yellow solid; yield 78%; mp 60–61 °C; [
a]
22= À157.2 (c 1.0,
D
White solid; mp 117.3–118.6 °C; 86% yield, 80% ee, HPLC
(Chiralcel OD-H, n-hexane/i-PrOH, 95:5, 0.5 mL/min, 254 nm):
CHCl3); 1H NMR (400 MHz, CDCl3): d 14.83 (s, 1H), 8.25–8.13 (m,
1H), 6.84–6.59 (m, 3H), 3.96–3.88 (m, 4H), 3.28 (s, 1H),
2.08–1.89 (m, 5H), 1.32–1.25 (m, 5H), 0.83 (s, 3H); 13C NMR
(101 MHz, CDCl3): d 164.1, 149.5, 123.3, 117.7, 116.3, 113.5, 78.2,
73.8, 55.9, 48.3, 43.4, 39.9, 27.6, 27.0, 19.8; HRMS (ESI) [M+H]+
calcd for C17H23NO3: 290.1751; found: 290.1755.
tR(minor) = 39.487 min, tR(major) = 58.233 min;
[
a
]
22 = À30.5 (c
D
1.5, CHCl3) {lit.9
[
a]
D
20 = À38.6 (c 0.76, CHCl3)}; 1H NMR (400 MHz,
CDCl3): d 7.43–7.40 (m, 2H), 6.89 (d, J = 8.6 Hz, 2H), 4.95 (dd,
J = 10.0, 5.3 Hz, 1H), 4.09–3.91 (m, 4H), 3.81 (s, 3H), 1.29–1.20
(m, 6H).
4.1.3. (1S,2R,4R)-1-(2-Hydroxy-3-methylbenzylideneamino)-
4.2.3. Diethyl hydroxy(3-methoxyphenyl)methylphosphonate
3ac9
7,7-dimethylbicyclo[2.2.1]heptan-2-ol L3
Yellow solid; yield 81%; mp 147–149 °C; [
a
]
22 = À56.1 (c 1.0,
D
Colorless oil; 85% yield, 79% ee, HPLC (Chiralcel OD-H, n-hex-
ane/i-PrOH, 95:5, 0.5 mL/min, 254 nm): tR(minor) = 38.992 min,
CHCl3); 1H NMR (400 MHz, CDCl3): d 14.20 (s, 1H), 8.39 (s, 1H),
7.16 (dd, J = 27.7, 7.3 Hz, 2H), 6.77 (t, J = 7.5 Hz, 1H), 3.86 (dd,
tR(major) = 59.256 min;
[
a]
D
22 = À12.5 (c 1.5, CHCl3) {lit.9
Please cite this article in press as: Xu, F.; et al. Tetrahedron: Asymmetry (2015), http://dx.doi.org/10.1016/j.tetasy.2015.07.004

F. Xu et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
5
[
a
]
20 = À13.6 (c 0.50, CHCl3)}; 1H NMR (400 MHz, CDCl3): d 7.20 (t,
tR(minor) = 28.636 min, tR(major) = 24.880 min;
[
a
]
22 = À25.2 (c
D
D
J = 7.9 Hz, 1H), 7.01–6.97 (m, 2H), 6.78 (d, J = 8.2 Hz, 1H), 4.93 (dd,
J = 10.9, 4.8 Hz, 1H), 4.03–3.89 (m, 4H), 3.74 (s, 3H), 1.23–1.14 (m,
6H).
2.0, CHCl3) {lit.16
[a]
20 = À17.4 (c 1.4, CHCl3)}; 1H NMR (400 MHz,
D
CDCl3): d 7.49 (d, J = 8.3 Hz, 2H), 7.38–7.35(m, 2H), 4.98 (dd,
J = 10.8, 3.5 Hz, 1H), 4.27 (s, 1H), 4.11–4.01 (m, 4H), 1.29–1.23
(m, 6H).
4.2.4. Diethyl hydroxy(2-methoxyphenyl)methylphosphonate
3ad9
4.2.11. Diethyl(3-chlorophenyl)(hydroxy)methylphosphonate
3ak9
Colorless oil; 82% yield, 76% ee, HPLC (Chiralcel OD-H, n-hex-
ane/i-PrOH, 95:5, 0.5 mL/min, 254 nm): tR(minor) = 35.387 min,
White solid; mp 54.5–55.3 °C; 89% yield, 71% ee, HPLC
(Chiralpak AD, n-hexane/i-PrOH, 95:5, 0.5 mL/min, 254 nm):
tR(major) = 43.051 min;
[
a
]
22 = À34.1 (c 1.5, CHCl3) {lit.9
D
[
a]
D
20 = À43.4 (c 0.78, CHCl3)}; 1H NMR (400 MHz, CDCl3): d 7.48–
tR(minor) = 33.972 min, tR(major) = 31.105 min;
[
a
]
22 = À21.3 (c
D
7.45 (m, 1H), 7.24–7.19 (m, 1H), 6.92 (t, J = 7.5 Hz, 1H), 6.82 (d,
J = 8.3 Hz, 1H), 5.35 (dd, J = 12.1, 7.2 Hz, 1H), 4.10–3.86 (m, 4H),
3.79 (s, 3H), 1.23 (t, J = 7.1 Hz, 3H), 1.10 (t, J = 7.1 Hz, 3H).
1.5, CHCl3) {lit.9
[
a]
D
20 = À25.3 (c 0.46, CHCl3)}; 1H NMR (400 MHz,
CDCl3): d 7.54 (s, 1H), 7.38–7.28 (m, 3H), 5.03 (d, J = 11.2 Hz, 1H),
4.66 (s, 1H), 4.16–4.03 (m, 4H), 1.32–1.24 (m, 6H).
4.2.5. (S)-Diethyl hydroxy(p-tolyl)methylphosphonate 3ae9
White solid; mp 96.3–97.0 °C; 84% yield, 79% ee, HPLC
(Chiralcel OD-H, n-hexane/i-PrOH, 95:5, 0.5 mL/min, 254 nm):
4.2.12. (S)-Diethyl hydroxy(thiophen-2-yl)methylphosphonate
3al9
Colorless oil; 83% yield, 75% ee, HPLC (Chiralcel OD-H, n-hex-
ane/i-PrOH, 90:10, 0.5 mL/min, 254 nm): tR(minor) = 18.878 min,
tR(minor) = 23.815 min, tR(major) = 27.382 min;
[
a]
22 = À31.3 (c
D
1.0, CHCl3) {lit.9
[
a]
20 = À40.0 (c 0.81, CHCl3)}; 1H NMR (400 MHz,
tR(major) = 31.172 min;
[
a
]
22 = À10.2 (c 1.0, CHCl3) {lit.9
D
D
CDCl3): d 7.38–7.36 (m, 2H), 7.18 (d, J = 7.9 Hz, 2H), 4.98 (dd,
J = 10.4, 5.0 Hz, 1H), 4.10–3.92 (m, 4H), 3.18 (s, 1H), 2.35 (s, 3H),
1.30–1.21 (m, 6H).
[a
]
D
20 = À11.3 (c 0.57, CHCl3)}; 1H NMR (400 MHz, CDCl3): d 7.23–
7.20 (m, 1H), 7.12–7.10 (m, 1H), 6.93–6.91(m, 1H), 5.17 (d,
J = 11.0 Hz, 1H), 4.85 (s, 1H), 4.11–3.95 (m, 4H), 1.24–1.16 (m, 6H).
4.2.6. (S)-Diethyl hydroxy(m-tolyl)methylphosphonate 3af16
Colorless oil; 83% yield, 78% ee, HPLC (Chiralcel OD-H, n-hex-
ane/i-PrOH, 95:5, 0.5 mL/min, 254 nm): tR(minor) = 24.183 min,
4.2.13. (S)-Diethyl hydroxy(5-methylthiophen-2-yl)methylpho-
sphonate 3am5c
White solid; mp 71.0–72.3 °C; 80% yield, 81% ee, HPLC (Chiralcel
tR(major) = 39.432 min;
[
a
]
22 = À17.6 (c 1.0, CHCl3) [lit.16
OD-H,
n-hexane/i-PrOH,
90:10,
0.5 mL/min,
254 nm):
D
[
a]
D
20 = À16.1 (c 1.0, CHCl3)]; 1H NMR (400 MHz, CDCl3): d 7.23–
tR(minor) = 16.341 min, tR(major) = 32.851 min;
[
a]
22 = À5.1 (c
D
7.14 (m, 3H), 7.04 (d, J = 6.7 Hz, 1H), 4.90 (dd, J = 10.9, 5.1 Hz,
1.5, CHCl3) {lit.5c
[a
]
D
20 = À3.8 (c 1.0, CHCl3)}; 1H NMR (400 MHz,
1H), 4.21 (s, 1H), 4.03–3.87 (m, 4H), 2.28 (s, 3H), 1.12–1.21(m, 6H).
CDCl3): d 6.97 (s, 1H), 6.64 (s, 1H), 5.12 (dd, J = 10.9, 5.8 Hz, 1H),
4.63 (s, 1H), 4.19–4.06 (m, 4H), 2.47 (s, 3H), 1.34–1.26 (m, 6H);
13C NMR (101 MHz, CDCl3): d 140.5, 136.9, 126.4, 124.9, 67.8,
66.2, 63.6, 63.3, 16.4, 15.3; HRMS (ESI) [M+Na]+ calcd for
4.2.7. Diethyl(4-(dimethylamino)phenyl)(hydroxy)methylphos-
phonate 3ag17
Light yellow solid; mp 93.8–94.3 °C; 85% yield, 72% ee, HPLC
(Chiralcel OD-H, n-hexane/i-PrOH, 90:10, 0.5 mL/min, 254 nm):
C10H17O4PS: 287.0477; found: 287.0475.
tR(minor) = 26.234 min, tR(major) = 35.252 min;
[a]
22 = À26.1 (c
4.2.14. (S)-Diethyl 1-hydroxy-3-phenylallylphosphonate 3an18
White solid; mp 87.2–88.7 °C; 85% yield, 82% ee, HPLC (Chiralpak
D
1.0, CHCl3); 1H NMR (400 MHz, CDCl3): d 7.36–7.33 (m, 2H), 6.71
(d, J = 8.7 Hz, 2H), 4.88 (dd, J = 9.6, 5.0 Hz, 1H), 4.11–3.88 (m, 4H),
3.15 (s, 1H), 2.95 (s, 6H), 1.29 (t, J = 7.1 Hz, 3H), 1.22 (t, J = 7.1 Hz, 3H).
AD,
tR(minor) = 22.621 min, tR(major) = 25.118 min;
1.0, CHCl3) {lit.18
n-hexane/i-PrOH,
90:10,
0.5 mL/min,
254 nm):
[
a]
22 = À12.1 (c
D
[a
]
D
18 = +7.7 (c 0.92, CHCl3) for 49% ee (R)}; 1H
4.2.8. (S)-Diethyl hydroxy(2,3,4-trimethoxyphenyl)methylphos-
phonate 3ah16
White solid; mp 82.3–83.8 °C; 81% yield, 78% ee, HPLC
(Chiralcel OD-H, n-hexane/i-PrOH, 90:10, 0.5 mL/min, 254 nm):
NMR (400 MHz, CDCl3): d 7.40 (d, J = 7.5 Hz, 2H), 7.32 (t, J = 7.4 Hz,
2H), 7.27–7.23 (m, 1H), 6.81–6.76 (m, 1H), 6.36–6.29 (m, 1H),
4.70–4.65 (m, 1H), 4.23–4.16(m, 4H), 3.73 (s, 1H), 1.36–1.31(m, 6H).
tR(minor) = 26.148 min, tR(major) = 30.828 min;
[
a
]
22 = À13.7 (c
4.2.15. Diethyl 1-hydroxy-2-methyl-3-phenylallylphosphonate
3ao19
D
1.0, CHCl3) {lit.16
[a
]
D
20 = À9.4 (c 2.4, CHCl3)}; 1H NMR (400 MHz,
CDCl3): d 7.28–7.25 (m, 1H), 6.70 (d, J = 8.7 Hz, 1H), 5.28 (dd,
J = 11.6, 7.1 Hz, 1H), 4.21–4.13 (m, 2H), 4.10–4.02 (m, 1H),
4.01–3.92 (m, 4H), 3.87 (s, 3H), 3.85 (s, 3H), 1.33 (t, J = 7.1 Hz,
3H), 1.20 (t, J = 7.1 Hz, 3H).
Colorless oil; 83% yield, 79% ee, HPLC (Chiralpak AD, n-hexane/i-
PrOH, 95:5, 0.5 mL/min, 254 nm): tR(minor) = 35.924 min,
tR(major) = 37.682 min;
[
a
]
22 = À8.2 (c 1.5, CHCl3) {lit.19
D
[a
]
D
20= À17.4 (c 1.4, CHCl3)}; 1H NMR (400 MHz, CDCl3): d 7.28–
7.13 (m, 5H), 6.61 (d, J = 4.8 Hz, 1H), 4.47 (d, J = 12.2 Hz, 1H),
4.2.9. (S)-Diethyl(4-fluorophenyl)(hydroxy)methylphosphonate
3ai16
4.14–4.08 (m, 4H), 1.95–1.93 (m, 3H), 1.28–1.23 (m, 6H).
White solid; mp 56.3–57.1 °C; 90% yield, 74% ee, HPLC
(Chiralcel OD-H, n-hexane/i-PrOH, 97:3, 0.5 mL/min, 254 nm):
4.2.16. (S)-Diethyl hydroxy(naphthalen-1-yl)methylphosphon-
ate 3ao20
tR(minor) = 34.289 min, tR(major) = 31.176 min;
[
a]
22 = À23.6 (c
White solid; mp 111.2–112.6 °C; 80% yield, 63% ee, HPLC
(Chiralpak AD, n-hexane/i-PrOH, 90:10, 0.5 mL/min, 254 nm):
D
1.5, CHCl3) {lit.16
[a
]
D
20 = À15.5 (c 2.6, CHCl3)}; 1H NMR (400 MHz,
CDCl3): d 7.49–7.45 (m, 2H), 7.05 (t, J = 8.6 Hz, 2H), 5.00 (dd,
J = 10.3, 5.3 Hz, 1H), 4.27–4.23 (m, 1H), 4.12–3.96 (m, 4H),
1.29–1.21 (m, 6H).
tR(minor) = 33.960 min, tR(major) = 32.051 min;
[
a
]
22 = À78.2 (c
D
1.5, CHCl3) {lit.20
[
a]
20 = À100.5 (c 0.6, CHCl3)}; 1H NMR (400 MHz,
D
CDCl3): d 8.12–8.10 (m, 1H), 7.92–7.83 (m, 3H), 7.56–7.48 (m, 3H),
5.90–5.86 (m, 1H), 4.11–3.95 (m, 4H), 1.25–1.05 (m, 6H).
4.2.10. (S)-Diethyl(4-bromophenyl)(hydroxy)methylphospho-
nate 3aj16
White solid; mp 69.2–70.5 °C; 91% yield, 72% ee, HPLC
(Chiralcel OD-H, n-hexane/i-PrOH, 95:5, 0.5 mL/min, 254 nm):
4.2.17. Diethyl 1-hydroxy-3-phenylpropylphosphonate 3ap20
Colorless oil; 73% yield, 41% ee, HPLC (Chiralcel OD-H, n-hex-
ane/i-PrOH, 95:5, 0.5 mL/min, 254 nm): tR(minor) = 17.488 min,
Please cite this article in press as: Xu, F.; et al. Tetrahedron: Asymmetry (2015), http://dx.doi.org/10.1016/j.tetasy.2015.07.004

6
F. Xu et al. / Tetrahedron: Asymmetry xxx (2015) xxx–xxx
3. (a) Gröger, H.; Hammer, B. Chem. Eur. J. 2000, 6, 943–948; (b) Merino, P.;
Marqués-Lopéz, E.; Herrera, R. P. Adv. Synth. Catal. 2008, 350, 1195–1208; (c)
Kolodiazhnyi, O. I. Tetrahedron Asymmetry 2005, 16, 3295–3340; (d) Albrecht,
Ł.; Albrecht, A.; Krawczyk, H.; Jørgensen, K. A. Chem. Eur. J. 2010, 16, 28–48.
4. (a) Wynberg, H.; Smaardijk, A. A. Tetrahedron Lett. 1983, 24, 5899–5900; (b)
Smaardijk, A. A.; Noorda, S.; Bolhuis, F.; Wynberg, H. Tetrahedron Lett. 1985, 26,
493–496.
5. (a) Yokomatsu, T.; Yamagishi, T.; Shibuya, S. Tetrahedron Asymmetry 1993, 4,
1779–1782; (b) Yokomatsu, T.; Yamagishi, T.; Shibuya, S. Tetrahedron
Asymmetry 1993, 4, 1783–1784; (c) Yokomatsu, T.; Yamagishi, T.; Shibuya, S.
J. Chem. Soc., Perkin Trans. 1 1997, 1527–1533.
tR(major) = 19.743 min;
[a]
22 = +10.7 (c 1.0, CHCl3) {lit.20
D
[a]
20 = +14.5 (c 0.3, CHCl3)}; 1H NMR (400 MHz, CDCl3): d 7.32–
D
7.19 (m, 5H), 4.22–4.12 (m, 4H), 3.86 (s, 1H), 3.01–2.94 (m, 1H),
2.79–2.71 (m, 1H), 2.09–1.99 (m, 3H), 1.40–1.30 (m, 6H).
4.2.18. (S)-Dimethyl hydroxy(phenyl)methylphosphonate 3ba6c
White solid; mp 99.3–100.2 °C; 68% yield, 79% ee, HPLC
(Chiralcel OD-H, n-hexane/i-PrOH, 95:5, 0.5 mL/min, 254 nm):
tR(minor) = 47.617 min, tR(major) = 50.259 min;
[
a]
22 = À38.5°
D
6. (a) Sasai, H.; Bougauchi, M.; Arai, T.; Shibasaki, M. Tetrahedron Lett. 1997, 38,
2717–2720; (b) Qian, C.; Huang, T.; Zhu, C.; Sun, J. J. Chem. Soc., Perkin Trans. 1
1998, 2097–2103; (c) Arai, T.; Bougauchi, M.; Sasai, H.; Shibasaki, M. J. Org.
Chem. 1996, 61, 2926–2927.
(c 1.0, CHCl3) [lit.6c
(400 MHz, CDCl3):
[
a]
25 = À44.3° (c 1.0, CHCl3)]; 1H NMR
D
d
7.51–7.50 (m, 2H), 7.40–7.31 (m, 3H),
5.07(d, J = 11.0 Hz, 1H), 4.33 (s, 1H), 3.73–3.67 (m, 6H).
7. For
additional
remarkable
examples
of
metal
catalyzed
hydrophosphonylations, see: (a) Duxbury, J. P.; Warne, J. N. D.; Mushtaq, R.;
Ward, C.; Thornton-Pett, M.; Jiang, M.; Greatrex, R.; Kee, T. P. Organometallics
2000, 19, 4445–4457; (b) Saito, B.; Katsuki, T. Angew. Chem. Int. Ed. 2005, 44,
4600–4602; (c) Saito, B.; Egami, H.; Katsuki, T. J. Am. Chem. Soc. 2007, 129,
1978–1986; (d) Suyama, K.; Sakai, Y.; Matsumoto, K.; Saito, B.; Katsuki, T.
Angew. Chem. Int. Ed. 2010, 49, 797–799.
4.2.19. (S)-Dibutyl hydroxy(phenyl)methylphosphonate 3ba14c
Colorless oil; 73% yield, 75% ee, HPLC (Chiralcel OD-H, n-hex-
ane/i-PrOH, 97:3, 0.5 mL/min, 254 nm): tR(minor) = 23.434 min,
tR(major) = 26.176 min;
[
a]
22 = À19.5 (c 1.0, CHCl3) {lit.14c
D
8. Abell, J. P.; Yamamoto, H. J. Am. Chem. Soc. 2008, 130, 10521–10523.
9. Zhou, X.; Liu, X.; Yang, X.; Shang, D.; Xin, J.; Feng, X. Angew. Chem. Int. Ed. 2008,
47, 392–394.
[a
]
D
21 = +25.8 (c 1.08, CHCl3) for the (R)-enantiomer}; 1H NMR
(400 MHz, CDCl3): d 7.50–7.48 (m, 2H), 7.38–7.29 (m, 3H), 5.04
(d, J = 10.9 Hz, 1H), 4.03–3.93 (m, 4H), 1.97 (s, 1H), 1.64–1.51 (m,
4H), 1.40–1.25 (m, 4H), 0.93–0.86 (m, 6H).
10. (a) Yang, F.; Zhao, D.; Lan, J.; Xi, P.; Yang, L.; Xiang, S.; You, J. Angew. Chem. Int.
Ed. 2008, 47, 5646–5649; (b) Sun, L.; Guo, Q.-P.; Li, X.; Zhang, L.; Li, Y.-Y.; Da, C.-
S.; Da, C.-S. Asian J. Org. Chem. 2013, 2, 1031–1035; (c) Wang, C.; Xu, C.; Tan, X.;
Peng, H.; He, H. Org. Biomol. Chem. 2012, 10, 1680–1685; (d) Deng, T.; Cai, C.
RSC Adv. 2014, 4, 27853–27856; (e) Kumar, A.; Sharma, V.; Kaur, J.; Kumar, V.;
Mahajan, S.; Kumar, N.; Chimni, S. S. Tetrahedron 2014, 70, 7044–7049; (f) Xie,
H.; Song, A.; Zhang, X.; Chen, X.; Li, H.; Sheng, H.; Wang, W. Chem. Commun.
2013, 928–930; (g) Zhao, Y.; Li, X.; Mo, F.; Li, L.; Lin, X. RSC Adv. 2013, 3, 11895–
11901.
11. Alegre-Requena, J. V.; Marqués-López, E.; Sanz Miguel, P. J.; Herrera, R. P. Org.
Biomol. Chem. 2014, 12, 1258–1264.
12. (a) Oppolzer, W. Tetrahedron 1987, 43, 1969–2004; (b) Oppolzer, W. Pure Appl.
Chem. 1990, 62, 1241–1250.
Acknowledgments
We are grateful for the financial support from the National
Natural Science Foundation of China (21172138 and 21302117)
and Fundamental Research Funds for the Central Universities
(GK201402060 and GK261001106).
13. For review, see (a) Bolm, C.; Legros, J.; Paih, J. L.; Zani, L. Chem. Rev. 2004, 104,
6217–6254; (b) Enthaler, S.; Junge, K.; Beller, M. Angew. Chem. Int. Ed. 2008, 47,
3317–3321. and references therein; (c)Iron Catalysis; Plietker, B., Ed.; Wiley-
VCH: Weinheim, 2008.
14. (a) Boobalan, R.; Chen, C.; Lee, G.-H. Org. Biomol. Chem. 2012, 10, 1625–1638;
(b) Boobalan, R.; Lee, G.-H.; Chen, C. Adv. Synth. Catal. 2012, 354, 2511–2520;
(c) Boobalan, R.; Chen, C. Adv. Synth. Catal. 2013, 355, 3443–3450.
15. (a) Yan, T.-H.; Chu, V.-V.; Lin, T.-C.; Wu, C.-H.; Liu, L.-H. Tetrahedron Lett. 1991,
32, 4959–4962; (b) Yan, T.-H.; Tan, C.-W.; Lee, H.-C.; Lo, H.-C.; Huang, T.-Y. J.
Am. Chem. Soc. 1993, 115, 2613–2621.
16. Muthupandi, P.; Sekar, G. Org. Biomol. Chem. 2012, 10, 5347–5352.
17. Caccamese, S.; Failla, S.; Finocchiaro, P.; Principato, G. Chirality 1998, 10, 100–
105.
18. Nakanishi, K.; Kotani, S.; Sugiura, M.; Nakajima, M. Tetrahedron 2008, 64, 6415–
6419.
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Please cite this article in press as: Xu, F.; et al. Tetrahedron: Asymmetry (2015), http://dx.doi.org/10.1016/j.tetasy.2015.07.004