Chiral phosphinothiourea-catalyzed asymmetric Morita-Baylis-Hillman reactions of acrylates with aromatic aldehydes

Article abstract of DOI:10.1016/j.tet.2009.07.066

A series of chiral bifunctional phosphinothioureas were synthesized and applied to the enantioselective Morita-Baylis-Hillman reaction of aromatic aldehydes with acrylates. In the presence of 8 mol % of organocatalyst 2e, the Baylis-Hillman adducts were o

Full text of DOI:10.1016/j.tet.2009.07.066

Tetrahedron 65 (2009) 8185–8190
Contents lists available at ScienceDirect
Tetrahedron
journal homepage: www.elsevier.com/locate/tet
Chiral phosphinothiourea-catalyzed asymmetric Morita–Baylis–Hillman
reactions of acrylates with aromatic aldehydes
*
Kui Yuan, Hong-Liang Song, Yinjun Hu, Xin-Yan Wu
Key Laboratory for Advanced Materials and Institute of Fine Chemicals, East China University of Science and Technology, Shanghai 200237, China
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 6 May 2009
Received in revised form 23 July 2009
Accepted 24 July 2009
Available online 29 July 2009
A series of chiral bifunctional phosphinothioureas were synthesized and applied to the enantioselective
Morita–Baylis–Hillman reaction of aromatic aldehydes with acrylates. In the presence of 8 mol % of
organocatalyst 2e, the Baylis–Hillman adducts were obtained in good enantioselectivities and up to 96%
yield under mild reaction conditions.
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Chiral phosphinothiourea
Acrylate
Asymmetric organocatalysis
Enantioselective Morita–Baylis–Hillman
reaction
1. Introduction
has yet been reported by using chiral catalysts. The slow reaction
rate (usually several days) and low enantioselectivities are the
Recently, the Morita–Baylis–Hillman (MBH) reaction, one of the
most useful and popular carbon–carbon bond forming reactions,
has attracted much attention due to the atom-economic construc-
tion of the multifunctional products.1 In the last decade, much re-
search effort was concentrated on its efficiency and selectivity, and
the asymmetric MBH reaction of enone with aldehydes and aza-
MBH reactions have obtained good results.2,3 However, the identi-
fication of an asymmetric MBH reaction of aldehydes with acrylates
is still a challenge for organic chemists, and few efficient chiral
catalysts have been developed for this process. Among them,
Hatakeyama reported the excellent enantioselective MBH reaction
of the highly reactive 1,1,1,3,3,3-hexafluoroisopropyl (HFIP) acrylate
with aldehydes (up to 99% ee).4 Shi developed a quinidine-derived
chiral amine as organocatalyst for the MBH reactions of aldehydes
biggest problems. To the best of our knowledge, the highest enan-
tioselectivity of this kind of MBH reaction catalyzed by organic
molecules was 64% ee using chiral N-methylprolinol at ꢀ10 ꢁC.7c
In our previous work, the enantioselective MBH reaction of MVK
(methylvinylketone)withp-nitrobenzaldehydecatalyzedby2awent
to completion in 5 min (Fig. 1).9 Considering the strong reactivity of
MVK, we desired to know if better results could be obtained by
lowering the reactivity of the Michael donor. To the best of our
knowledge, there is no report related to the phosphine-catalyzed
enantioselective MBH reaction of acrylates with aldehydes. Herein,
we report the first example of a good enantioselective asymmetric
MBH reaction of acrylates with aldehydes using chiral bifunctional
phosphinothiourea as the catalyst.
with (a
)-naphthyl acrylate to achieve 92% ee but only 17% yield.5
CHO
O
OH
O
Chen and co-workers reported on the use of La(OTf)3 and camphor-
derived dimerized ligands to accelerate the MBH reaction of alde-
hydes with acrylates obtained up to 95% ee and up to 97% yield.6
While commerciallyavailable unactivated acrylates (such as methyl,
ethyl or n-butyl acrylate) used as Michael donor, fewer successful
asymmetric MBH reactions were delevoped.6,7 Except for some re-
ports of enzyme-catalyzed kinetic resolution of racemic MBH
products with poor yields,1b,2a,8 no other good enantioselectivity
2a
10 mol%
CH2Cl2, 13 °C, 5 min
NO2
34% yield, 80% ee
NO2
Figure 1. The MBH reaction of MVK with p-nitrobenzaldehyde catalyzed by 2a.
2. Results and discussion
Initially we chose the reaction of n-butyl acrylate with p-nitro-
benzaldehyde as a model reaction, and evaluated the organocatalysts
* Corresponding author. Tel.: þ86 21 64252011; fax: þ86 21 64252758.
E-mail address: xinyanwu@ecust.edu.cn (X.-Y. Wu).
0040-4020/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2009.07.066

8186
K. Yuan et al. / Tetrahedron 65 (2009) 8185–8190
Table 2
2a–g, which can be easily synthesized by condensation of (R,R)-
2-amino-1-(diphenylphosphino)-cyclohexane (1) with 1.1 equiv of
the corresponding isothiocyanate under mild conditions (Fig. 2).9 The
results are summarized in Table 1.
The effect of the solventsa
CHO
O
OH
O
10 mol% 2e
n-BuO
n-BuO
Solvent, 30 °C
2a: R = c-C6H11
S
NO2
2b
: R = C6H5
NO2
R
2c: R = 3,5-(CF3)2C6H3
NH2
NH
N
H
RNCS
2d
: R = n-C4H9
Entry
Solvent
Time (h)
Yieldb (%)
eec (%)
2e: R = n-C12H25
PPh2
PPh2
2f: R = n-C18 37
H
1
2
3
CH2Cl2
CHCl3
PhMe
THF
THF
THF
5
5
5
4
4
4
3
5
5
5
5
4
80
56
54
99
99
97
94
Trace
33
22
18
78
60
63
69
71
71
71
70
n.d.g
41
60
55
49
2g
1
2
: R = C6H5CH2
Figure 2. Synthesis of the phosphinothiourea catalysts.
4d
5e
6f
7
Table 1
Ether
Screening of the catalysts for the MBH reaction of n-butyl acrylate and
p-nitrobenzaldehydea
8
9
10
11
12
1,4-dioxane
EtOH
CHO
DMF
CH3CN
DMSO
O
OH
O
2a-g
10 mol%
n-BuO
n-BuO
CH2Cl2, 30 °C
a
Unless stated otherwise, the reactions were conducted with 10 mol % of orga-
NO2
nocatalyst 2e, 5 equiv of n-butyl acrylate in the solvent (0.2 M) at 30 ꢁC.
NO2
b
Isolated yields.
c
Determined by chiral HPLC.
d
Dry THF was used.
Entry
Catalyst
Time (h)
Yieldb (%)
eec (%)
e
Commercially available THF was used directly.
Dry THF with 0.2 vol % of H2O was used.
1
2
3
4
5
6
7
8
2a
2b
2c
2d
2e
2e
2f
5
12
12
5
5
24
5
57
47
59
69
80
80
78
80
61
53
43
60
60
60
60
59
f
g
Not determined.
available THF was directly used for further investigation. In ether,
the reaction was accelerated and the product was formed in 94%
yield within 3 h (entry 7). However, in the case of 1,4-dioxane, the
product was obtained in trace (entry 8). Also, in the polar solvents,
such as EtOH, DMF, and MeCN, the product was obtained in less
yield and ee (entries 9–11). In DMSO, the product was formed in
78% yield and low ee (entry 12).
Furthermore, other aspects of this reaction such as the reaction
temperature, the ratio of 3/4, the loading of the catalyst and addi-
tives were investigated (Table 3). The results indicated that the
chemical yields were strongly influenced by the reaction temper-
ature without obvious enantioselectivity change. On lowering the
reaction temperature from room temperature to ꢀ15 ꢁC, the ee
2g
5
a
Unless stated otherwise, the reactions were conducted with 10 mol % of orga-
nocatalyst, 5 equiv of n-butyl acrylate in CH2Cl2 (0.2 M) at 30 ꢁC.
b
Isolated yields.
Determined by chiral HPLC.
c
We found the thiourea moiety was critical for the MBH reaction
in terms of both yield and enantioselectivity. As illustrated in Table 1,
the aliphatic thioureas were more effective than the aromatic
thioureas, the reaction could complete in a shorter reaction time
and provide higher yield and enantioselectivity (entries 1, 4–8 vs
entries 2 and 3). The catalyst 2b, which provided high enantiose-
lectivity for the MBH reaction of MVK with aromatic aldehydes,9
showed poor reactivity toward this transformation. And the orga-
nocatalyst 2e was proved to be the best catalyst for this reaction
and furnished the desired product in 80% yield and 60% ee (entry 5).
Further lengthening the carbon chain of the thiourea moiety could
not increase the yield and ee (entry 7 vs 5). In addition, the product
was found to be stable for long periods of time in the dichloro-
methane solution (entry 6 vs 5). Comparatively, when MVK was
used as Michael donor, longer reaction time afforded lower
chemical yield due to the over reaction of the MBH product with
MVK.9 The MBH adduct was (S)-configuration, which was assigned
by comparing the optical rotation values with those reported in the
literatures.7b,8a
Next, solvent effects on this reaction using 2e as the organo-
catalyst were probed (Table 2). The results indicated that THF was
the optimal solvent in which the MBH reaction accomplished in 4 h
and afforded nearly quantitative yield and 71% ee. Whether dried or
not, using THF as solvent obtained the same results (entries 4
and 5). In general, the presence of water in H-bonding activation
catalytic system might lead to a negative effect on the enantiose-
lectivity and conversion. To test the effect of the trace amount of
water in THF, distilled H2O (0.2 vol %) was added to dry THF freshly
distilled from Na-benzophenone, the result indicated that the effect
could be ignored (entry 6 vs entries 4 and 5). Thus, commercially
Table 3
Optimization of reaction conditionsa
CHO
O
OH
O
2e
n-BuO
n-BuO
THF
NO2
NO2
4
3
Entry
Temp (ꢁC)
3/4
2e (mol %)
Time (h)
Yieldb (%)
eec (%)
1
2
3
4
5
6
7
8
30
25
25
25
25
25
0
ꢀ15
25
25
25
5
5
5
5
8
3
5
5
5
5
5
10
10
8
5
8
8
8
8
8
4
5
5
6
5
6
6
7
5
5
5
99
92
88
83
88
76
43
31
83
0
71
75
76
75
75
75
76
77
76
n.d.g
76
9d
10e
11f
8
8
72
a
Unless stated otherwise, the reactions were conducted in THF (0.2 M).
Isolated yields.
Determined by chiral HPLC.
Added 8 mol % NEt3.
Added 8 mol % PhCOOH.
Added 10 mg 4 Å MS.
b
c
d
e
f
g
Not determined.

K. Yuan et al. / Tetrahedron 65 (2009) 8185–8190
8187
Table 4
In addition, the reaction could occur with various substituted
aromatic aldehydes. As indicated in Table 5, the strong electron-
deficient benzaldehydes usually proceeded very quickly to provide
the desired products in excellent yields (85–96% yield, entries 1–6)
and good enantioselectivities. However ortho substitution as in the
cases of 2-nitrobenzaldehyde and 2,4-dichlorobenzaldehyde has
a deleterious effect on enantioselectivity, with the products being
obtained with 35% ee, 33% ee and even 7% ee (entries 3, 4, and 11),
respectively. The reaction with non-substituted benzaldehyde and
2-furaldehyde gave relatively poor yields and enantioselectivities
due to the low activities (entries 13 and 14).
The MBH reaction of different acrylates with p-nitrobenzaldehyde by 2ea
CHO
O
OH
O
8 mol% 2e
R'O
R'O
THF, 25 °C
NO2
NO2
Entry
R0
Time (h)
Yieldb (%)
eec (%)
1
2
3
4
5
6
Me
Et
n-Bu
t-Bu
Bn
7
7
5
8
7
8
85
92
88
53
63
32
76
77
76
74
76
9
3. Conclusion
(a)-Nap
In summary, we have developed the first phosphinothiourea-
catalyzed asymmetric MBH reaction between acrylates and alde-
hydes. It is particularly noteworthy that this new catalytic system is
effective for various commercially available acrylates. With 8 mol %
of phosphinothiourea 2e, the Morita–Baylis–Hillman reaction could
proceed in 5–24 h under mild conditions and afford the desired
products in up to 77% ee and moderate-to-excellent yields (up to
96%).
a
Unless stated otherwise, the reactions were conducted with 8 mol % of orga-
nocatalyst 2e, 5 equiv of acrylate in THF (0.2 M) at 25 ꢁC.
b
Isolated yields.
c
Determined by chiral HPLC, and the absolute configuration was determined by
comparison of optical rotation with that of literature report.4,6,7b,8a,10
value increased just 1% (entry 8 vs 3). The suitable reaction tem-
perature was 25 ꢁC (entries 2 and 3). Using Et3N, PhCOOH or 4 Å MS
as the additive, the catalytic activity of 2e was also examined. As
illustrated in Table 3, Et3N or 4 Å MS as the additive provided lower
yield (83% and 72%) and similar enantioselectivity (76% ee) (entries
9 and 11 vs 3). However, using PhCOOH as additive failed to obtain
the product (entry 10). The perfect ratio of 3/4 was 5/1. And this
reaction could be performed with as low as 5 mol % of catalyst
loading (entry 4), where a comparable result (75% ee, 83% yield)
was achieved.
Under the optimized conditions (8 mol % of 2e as catalyst,
5 equiv of acrylate, THF as solvent, 25 ꢁC), the MBH reactions of
various acrylates with p-nitrobenzaldehyde (4) were surveyed to
determine the scope of substrates. The results in Table 4 showed
that better yield and enantioselectivity were obtained using ethyl
acrylate as a Michael donor (92% yield, 77% ee). Surprisingly,
4. Experimental
4.1. General methods
Melting points are taken without correction. Optical rotations
were measured on a WZZ-2A digital polarimeter at the wavelength
of the sodium D-line (598 nm) at 20 ꢁC. 1H, 13C, and 31P NMR spectra
were recorded on Bruker 500 or 400 spectrometer. 1H NMR spectra
were referenced to tetramethylsilane (d, 0.00 ppm) using CDCl3 or
(CD3)2CO as solvent. 13C NMR spectra were referenced to solvent
carbons (77.0 ppm for CDCl3, 206.5 ppm for (CD3)2CO). 31P NMR
spectra were referenced to an external H3PO4 signal (0.0 ppm). IR
spectra were recorded on Nicolet Magna-I 550 spectrometer. High
resolution mass spectra (HRMS) were recorded on Micromass GCT
spectrometer with Electron Ionization (EI) resource. HPLC analysis
was performed on Waters 510 with 2487 detector using Daicel
Chiralcel OD-H, Chiralcel OJ, Chiralpak AS-H or Chiralpak AD-H
column.
(a)-naphthyl acrylate just gave the product in 32% yield and 9% ee
in the same reaction conditions and dioxanone was observed as
a byproduct.4
Table 5
The MBH reactions between various aromatic aldehydes with ethyl acrylate or
THF was directly used without further purification. And other
solvents were purified and dried according to standard methods
prior to use. 4-Trifluoromethylbenzaldehyde, 4-chlorobenzaldehyde
and benzaldehyde, 2-furaldehyde were freshly distilled while other
aldehydes were recrystallized from ethanol.
n-butyl acrylate catalyzed by 2ea
O
O
OH
Ar
8 mol% 2e
R'O
ArCHO
R'O
THF, 25 °C
4.2. General procedure for the synthesis of chiral
phosphinothiourea catalysts
Entry
Ar
R0
Time (h)
Yield (%)b
ee (%)c
1
2
3
4
5
6
7
8
4-NO2C6H4
Et
n-Bu
Et
n-Bu
Et
n-Bu
Et
n-Bu
Et
n-Bu
Et
Et
7
5
92
88
90
85
96
94
63
54
37
36
66
36
24
42
77
76
35
33
77
75
71
69
65
63
7
4-NO2C6H4
2-NO2C6H4
2-NO2C6H4
3-NO2C6H4
3-NO2C6H4
4-CF3C6H4
4-CF3C6H4
4-ClC6H4
4-ClC6H4
2,4-Cl2C6H3
4-BrC6H4
C6H5
12
12
10
10
12
12
20
20
20
18
24
20
To a solution of (R,R)-1-amino-2-(diphenylphosphino)cyclo-
hexane (1)9,11 (283 mg, 1.0 mmol) in 3.0 mL CH2Cl2 was added
isothiocyanate (1.1 mmol) at room temperature, and the resulting
mixture was stirred at this temperature until the reaction com-
pleted (monitoring by TLC). The solvent was removed under re-
duced pressure and the residue was purified by column
chromatography (petroleum ether/ethyl acetate¼4/1 or 3/1) to
afford the chiral phosphinothiourea compounds (the phosphino-
thiourea catalysts 2a–c were described in our previous work).9
9
10
11
12
13d
14
65
54
27
Et
Et
2-Furyl
a
4.2.1. Phosphinothiourea 2a. White solid, 65% yield, mp: 98–
Unless stated otherwise, the reactions were conducted with 8 mol % of orga-
100 ꢁC; [
a
]
ꢀ46.0 (c 1.0, CH2Cl2); IR (KBr, cmꢀ1):
n 3415, 3064,
nocatalyst 2e, 5 equiv of acrylate in THF (0.2 M) at 25 ꢁC.
D
b
2924, 2851, 1644, 1538, 1362, 1064, 608, 559; 1H NMR (CDCl3,
Isolated yields.
c
Determined by chiral HPLC, and the absolute configuration was determined by
500 MHz):
d
7.58 (t, 2H, J¼6.9 Hz), 7.51–7.47 (m, 2H), 7.39–7.33 (m,
comparison of optical rotation with that of literature report.7c,8a
d
6H), 5.26–5.73 (br, 2H), 4.32–3.72 (br, 1H), 2.46–2.43 (m, 1H),
2.36–2.33 (m, 1H), 1.86–1.64 (m, 8H), 1.58–1.56 (m, 1H), 1.43–1.40
8 mol % NEt3 was added. Under the typical reaction conditions, no product was
detected.

8188
K. Yuan et al. / Tetrahedron 65 (2009) 8185–8190
(m, 1H), 1.28–0.99(m, 8H); 13C NMR (CDCl3, 125 MHz):
d
178.52,
2H, J¼6.8 Hz), 7.54–7.35 (m, 8H), 5.38 (br, 2H), 4.09 (br,1H), 2.95 (br,
1H), 2.49–2.37 (m, 2H), 1.78–1.69 (m, 3H), 1.48–1.38 (m, 3H), 1.36–
1.28 (m, 34H), 0.90 (t, J¼6.8 Hz, 3H); 13C NMR (CDCl3, 100 MHz):
136.78 (d, J¼13.8 Hz), 134.75 (d, J¼15.1 Hz), 133.80 (d, J¼20.6 Hz),
132.60 (d, J¼19.1 Hz), 128.59, 128.28 (d, J¼6.8 Hz), 128.23, 127.92
(d, J¼7.5 Hz), 51.63, 40.00 (d, J¼13.3 Hz), 32.61, 32.35, 32.18, 27.04,
24.91, 24.15, 23.73; 31P NMR (CDCl3, 202 MHz, 85% H3PO4):
d
180.06, 137.12 (d, J¼13.2 Hz), 134.95 (d, J¼14.2 Hz), 134.43 (d,
J¼20.4 Hz), 132.90 (d, J¼18.5 Hz), 129.09, 128.71 (d, J¼6.2 Hz),
128.52, 128.35 (d, J¼7.5 Hz), 55.88, 43.62, 40.57 (d, J¼14.2 Hz),
33.80, 31.94, 29.73, 29.68, 29.64, 29.55, 29.38, 29.35, 28.85, 27.64,
26.95, 25.53, 24.45, 22.70, 14.16; 31P NMR (CDCl3, 202 MHz, 85%
d
ꢀ9.39; HRMS (EI) calcd for C25H33N2PS ([M]þ) 424.2102, found:
424.2102.
4.2.2. Phosphinothiourea 2b. White solid, 92% yield, mp: 148–
H3PO4):
found: 594.4139.
d
ꢀ6.25; HRMS (EI) calcd for C37H59N2PS ([M]þ) 594.4137,
149 ꢁC; [
a
]
D ꢀ78.5 (c 1.0, CH2Cl2); IR (KBr, cmꢀ1):
n
3374, 3051, 2928,
2852, 1596, 1531, 1496, 1449, 1318, 1258, 1046, 743, 696; 1H NMR
(CDCl3, 500 MHz):
d
7.56–7.50 (m, 5H), 7.33–7.23 (m, 9H), 7.13 (d,
4.2.7. Phosphinothiourea 2g. White solid, 91% yield, mp: 63–65 ꢁC;
J¼6.4 Hz, 2H), 6.11 (s, 1H), 4.36 (s, 1H), 2.36–2.29 (m, 2H), 1.73–1.70
[a
]
D ꢀ18.8 (c 0.85, CH2Cl2); IR (KBr, cmꢀ1):
n 3419, 3062, 2927, 2853,
(m, 2H), 1.58 (s, 1H), 1.38–1.35 (m, 1H), 1.18–1.22 (m, 2H), 1.08–1.06
2361, 1541, 1496, 1480, 1433, 1373, 1262, 1050, 742, 697, 509; 1H
(m, 1H); 13C NMR (CDCl3, 125 MHz):
d
179.57, 137.29 (d, J¼13.0 Hz),
NMR (CDCl3, 400 MHz): d 7.57–7.47 (m, 4H), 7.37–7.29 (m, 9H),
136.73, 135.61, 135.35 (d, J¼20.6 Hz), 133.26 (d, J¼18.0 Hz), 130.67,
129.70, 129.15 (d, J¼5.9 Hz), 128.93 (d, J¼5.1 Hz), 128.86, 127.34,
125.41, 57.09 (d, J¼15.8 Hz), 41.27 (d, J¼16.1 Hz), 34.04, 28.27, 26.18,
7.23–7.22 (m, 2H), 5.19–5.78 (br, 1H), 3.78–4.39 (br, 3H), 2.46–2.37
(m, 1H), 2.31–2.28 (m, 1H), 1.75–1.61 (m, 4H), 1.47–1.39 (m, 1H),
1.30–1.23 (m, 3H); 13C NMR (CDCl3, 100 MHz):
d 180.38, 136.98 (d,
25.14; 31P NMR (CDCl3, 202 MHz, 85% H3PO4):
d
ꢀ7.73; HRMS (EI)
J¼12.4 Hz), 135.02 (d, J¼14.9 Hz), 134.36 (d, J¼20.4 Hz), 132.50 (d,
J¼18.7 Hz), 129.13, 128.77, 128.72, 128.67, 128.39 (d, J¼7.6 Hz),
127.75, 127.66, 55.51, 47.75, 40.40 (d, J¼14.1 Hz), 33.10, 27.28, 25.16,
calcd for C25H27N2PS ([M]þ) 418.1633, found: 418.1634.
4.2.3. Phosphinothiourea 2c. White solid, 86% yield, mp: 212–
24.17; 31P NMR (CDCl3, 202 MHz, 85% H3PO4):
d
ꢀ6.66; HRMS (EI)
214 ꢁC; [
a
]
D ꢀ15.9 (c 0.8, CH2Cl2); IR (KBr, cmꢀ1):
n
3221, 3054, 2941,
calcd for C23H31N2PS ([M]þ) 432.1789, found: 432.1788.
2859, 1548, 1471, 1277, 1137, 1108, 888, 742, 715; 1H NMR ((CD3)2CO,
400 MHz): d 8.30 (s, 2H), 7.66 (s, 1H), 7.56 (s, 4H), 7.36–7.32 (m, 5H),
7.28 (d, J¼6.8 Hz, 1H), 4.48 (s, 1H), 3.25 (s, 2H), 2.67 (t, J¼10.0 Hz,
1H), 2.21–2.18 (m, 1H), 1.86–1.83 (m, 1H), 1.69 (s, 2H), 1.45–1.40 (m,
1H), 1.34–1.27 (m, 2H), 1.04–1.01 (m, 1H); 13C NMR ((CD3)2CO,
4.3. General procedure for the Morita–Baylis–Hillman
reaction
125 MHz):
d
180.51, 143.06, 138.43 (d, J¼14.1 Hz), 137.13 (d,
To a solution of the organocatalyst 2e (0.016 mmol) in THF
(1.0 mL) was added acrylate (1.0 mmol) at 25 ꢁC. After 10 min stir-
ring at this temperature, aromatic aldehyde (0.2 mmol) was added.
The reaction mixture was stirred at 25 ꢁC (monitoring by TLC). After
the reaction was completed, the solvent was removed under re-
duced pressure and the residue was purified by a flash column
chromatography to afford the Baylis–Hillman adduct and the ee
value was determined by HPLC analysis with chiral column.
J¼17.3 Hz), 135.75 (d, J¼21.0 Hz), 133.83 (d, J¼18.3 Hz), 132.14 (q,
J¼33.0 Hz), 130.17, 129.52 (d, J¼6.0 Hz), 129.39 (d, J¼7.5 Hz), 129.12,
125.78, 123.61, 123.26, 117.35, 55.62 (d, J¼15.5 Hz), 40.99 (d,
J¼15.6 Hz), 33.73, 28.72 (d, J¼3.6 Hz), 26.30 (d, J¼4.0 Hz), 25.63; 31P
NMR ((CD3)2CO, 202 MHz, 85% H3PO4):
d
ꢀ5.08; HRMS (EI) calcd for
C27H25N2F6PS ([M]þ)554.1380, found: 554.1381.
4.2.4. Phosphinothiourea 2d. White solid, 70% yield, mp: 76–78 ꢁC;
[
a]
D ꢀ33.0 (c 1.0, CH2Cl2); IR (KBr, cmꢀ1):
n
3262, 3072, 2931, 2856,
7.59 (t, 2H,
4.3.1. Methyl (S)-2-[hydroxy-(4-nitro-phenyl)-methyl]-acrylate.4,7b 85%
1546, 1434, 742, 698; 1H NMR (CDCl3, 500 MHz):
d
yield, 76% ee, [
a
]
D þ54.4 (c 0.34, MeOH); 1H NMR (CDCl3, 500 MHz):
J¼6.9 Hz), 7.50–7.48 (m, 2H), 7.38–7.33 (m, 6H), 5.56–5.44 (br, 2H),
4.42–3.85 (br, 1H), 3.12–2.83 (br, 1H), 2.43–2.33 (m, 2H), 1.73–1.68
(m, 4H), 1.43–1.35 (m, 3H), 1.34–1.18 (m, 5H), 0.89 (t, 3H, J¼7.3 Hz);
d
8.22 (d, J¼8.7 Hz, 2H), 7.58 (d, J¼8.7 Hz, 2H), 6.40 (s, 1H), 5.87 (s, 1H),
5.64 (d, J¼6.2 Hz, 1H), 3.75 (s, 3H), 3.27 (d, J¼6.2 Hz,1H); HPLC analysis
(OD-H column,
l¼254 nm, eluent: hexane/2-propanol¼95/5, flow
13C NMR (CDCl3, 100 MHz):
d
180.08, 137.21 (d, J¼13.8 Hz), 135.12
rate: 1.0 mL/min): tR¼38.22 min (major), 33.70 min (minor).
(d, J¼15.6 Hz), 134.34 (d, J¼20.6 Hz), 132.50 (d, J¼18.8 Hz), 129.09,
128.73 (d, J¼6.6 Hz),128.63, 128.38 (d, J¼7.5 Hz), 55.98, 43.19, 40.52
(d, J¼12.8 Hz), 33.56, 30.87, 27.67, 25.42, 24.35, 20.04, 13.79; 31P
4.3.2. Ethyl (S)-2-[hydroxy-(4-nitro-phenyl)-methyl]-acrylate.8a 92%
yield, 77% ee, [
a
]
D þ60.3 (c 0.39, MeOH); 1H NMR (CDCl3, 500 MHz):
NMR (CDCl3, 202 MHz, 85% H3PO4):
d
ꢀ6.62; HRMS (EI) calcd for
d
8.21 (d, J¼8.7 Hz, 2H), 7.58 (d, J¼8.7 Hz, 2H), 6.40 (s, 1H), 5.85 (s,
C23H31N2PS ([M]þ) 398.1946, found: 398.1945.
1H), 5.63 (d, J¼6.3 Hz, 1H), 4.20 (q, J¼7.1 Hz, 2H), 3.35 (d, J¼6.3 Hz,
1H), 1.27 (t, J¼7.1 Hz, 3H); HPLC analysis (OD-H column, ¼254 nm,
l
4.2.5. Phosphinothiourea 2e. Colorless oil, 73% yield, [
a
]
ꢀ27.5 (c
eluent: hexane/2-propanol¼95/5, flow rate: 1.0 mL/min):
tR¼29.63 min (major), 26.51 min (minor).
D
1.0, CH2Cl2); IR (KBr, cmꢀ1):
n
3313, 2926, 2852, 1551, 1493, 1228,
699, 505; 1H NMR (CDCl3, 500 MHz):
d
7.57 (t, 2H, J¼6.9 Hz), 7.51–
7.47 (m, 2H), 7.37–7.32 (m, 6H), 5.86–5.35 (br, 2H), 4.31–3.85 (br,
1H), 3.15–2.72 (br, 1H), 2.43–2.32 (m, 2H), 1.72–1.65 (m, 3H), 1.39–
1.37 (m, 3H), 1.30–1.14 (m, 22H), 0.90–0.87 (m, 3H); 13C NMR
4.3.3. n-Butyl (S)-2-[hydroxy-(4-nitro-phenyl)-methyl]-acrylate. 7b,12
88% yield, 76% ee, [
a
]
þ54.8 (c 0.46, MeOH); 1H NMR (CDCl3,
D
400 MHz):
d
8.21 (d, J¼8.4 Hz, 2H), 7.58 (d, J¼8.4 Hz, 2H), 6.40 (s,
(CDCl3, 100 MHz):
d
180.05, 137.12 (d, J¼13.3 Hz), 135.48 (d,
1H), 5.85 (s, 1H), 5.63 (d, J¼6.4 Hz, 1H), 4.15 (t, J¼6.8 Hz, 2H), 3.32
(d, J¼6.4 Hz, 1H), 1.66–1.58 (m, 2H), 1.39–1.30 (m, 2H), 0.92 (t,
J¼14.6 Hz), 134.41 (d, J¼20.4 Hz), 132.42 (d, J¼18.5 Hz), 129.08,
128.69 (d, J¼6.4 Hz),128.53, 128.35 (d, J¼7.5 Hz), 55.18, 43.42, 40.59
(d, J¼15.3 Hz), 33.64, 31.91, 29.72, 29.64, 29.60, 29.53, 29.34, 28.86,
27.70, 26.93, 25.49, 24.44, 22.69, 14.14; 31P NMR (CDCl3, 202 MHz,
85% H3PO4):
510.3198, found: 510.3200.
J¼7.6 Hz, 3H); HPLC analysis (AS-H column,
l¼254 nm, eluent:
hexane/2-propanol¼96/4, flow rate: 1.0 mL/min): tR¼22.18 min
(major), 24.26 min (minor).
d
ꢀ6.43; HRMS (EI) calcd for C31H47N2PS ([M]þ)
4.3.4. tert-Butyl (S)-2-[hydroxy-(4-nitro-phenyl)-methyl]-acrylate.10
53% yield, 74% ee, [
a
]
þ38.9 (c 0.18, MeOH); 1H NMR (CDCl3,
D
4.2.6. Phosphinothiourea 2f. Colorless oil, 78% yield, [
a
]
ꢀ25.5 (c
500 MHz):
d
8.21 (d, J¼8.7 Hz, 2H), 7.57 (d, J¼8.5 Hz, 2H), 6.31 (s,
D
1.0, CH2Cl2); IR (KBr, cmꢀ1):
n
3309, 2924, 2852, 1552, 1494, 1469,
1H), 5.75 (s,1H), 5.57 (d, J¼6.6 Hz,1H), 3.45 (d, J¼6.6 Hz,1H),1.43 (s,
9H); HPLC analysis (AD-H column,
¼254 nm, eluent: hexane/2-
1432, 1258,1228, 747, 699, 505; 1H NMR (CDCl3, 400 MHz):
d
7.62 (t,
l

K. Yuan et al. / Tetrahedron 65 (2009) 8185–8190
8189
propanol¼90/10, flow rate: 1.0 mL/min): tR¼9.45 min (major),
(d, J¼6.0 Hz, 1H), 4.14 (t, J¼6.6 Hz, 2H), 3.32 (d, J¼6.0 Hz, 1H), 1.62–
1.58 (m, 2H), 1.36–1.29 (m, 2H), 0.90 (t, J¼7.4 Hz, 3H); HPLC analysis
11.49 min (minor).
(OD-H column,
l
¼220 nm, eluent: hexane/2-propanol¼99/1, flow
4.3.5. Benzyl (S)-2-[hydroxy-(4-nitro-phenyl)-methyl]-acrylate.6 63%
rate: 1.0 mL/min): tR¼23.71 min (major), 21.23 min (minor).
yield, 76% ee, [
a
]
D þ40.4 (c 0.26, MeOH); 1H NMR (CDCl3, 400 MHz):
d
8.19 (d, J¼8.6 Hz, 2H), 7.56 (d, J¼8.6 Hz, 2H), 7.37–7.35 (m, 3H),
4.3.13. Ethyl (S)-2-[hydroxy-(4-chloro-phenyl)-methyl]-acrylate.7c 37%
1
7.30–7.28 (m, 2H), 6.47 (s,1H), 5.92 (s,1H), 5.66 (d, J¼6.0 Hz,1H), 5.18
(s, 2H), 3.24 (d, J¼6.0 Hz, 1H); HPLC analysis (AS-H column,
yield, 65% ee; H NMR (CDCl3, 500 MHz):
d
7.32 (s, 4H), 6.34 (s, 1H),
5.80 (s, 1H), 5.53 (d, J¼5.7 Hz, 1H), 4.18 (q, J¼7.1 Hz, 2H), 3.21 (d,
l
¼254 nm, eluent: hexane/2-propanol¼90/10, flow rate: 1.0 mL/
J¼5.7 Hz, 1H), 1.26 (t, J¼7.1 Hz, 3H); HPLC analysis (OD-H column,
min): tR¼18.09 min (major), 20.62 min (minor).
l
¼220 nm, eluent: hexane/2-propanol¼97/3, flow rate: 1.0 mL/min):
tR¼15.41 min (major), 13.90 min (minor).
4.3.6. -Naphthyl (S)-2-[hydroxy-(4-nitro-phenyl)-methyl]-acryl-
a
ate. 6 32% yield, 9% ee; 1H NMR (CDCl3, 500 MHz):
8.18 (d,
d
4.3.14. n-Butyl (S)-2-[hydroxy-(4-chloro-phenyl)-methyl]-acrylate.15
J¼8.7 Hz, 2H), 7.80 (d, J¼8.2 Hz, 1H), 7.69 (d, J¼8.2 Hz, 1H,), 7.61 (d,
J¼8.6 Hz, 2H), 7.50 (d, J¼8.3 Hz, 1H), 7.39 (m, 3H), 7.11 (d, J¼7.5 Hz,
1H), 6.78 (s, 1H), 6.14 (s, 1H), 5.76 (s, 1H), 2.29 (br, 1H); HPLC
36% yield, 63% ee; 1H NMR (CDCl3, 500 MHz):
d 7.32 (s, 4H), 6.34 (s,
1H), 5.80 (s, 1H), 5.53 (d, J¼5.7 Hz, 1H), 4.13 (t, J¼6.6 Hz, 2H), 3.92
(d, J¼5.7 Hz, 1H), 1.63–1.58 (m, 2H), 1.35–1.29 (m, 2H), 0.91 (t,
analysis (AS-H column,
l
¼254 nm, eluent: hexane/2-propanol¼90/
J¼7.4 Hz, 3H); HPLC analysis (AS-H column,
l
¼220 nm, eluent:
10, flow rate: 1.0 mL/min): tR¼20.97 min (major), 18.69 min
hexane/2-propanol¼97/3, flow rate: 0.8 mL/min): tR¼14.07 min
(minor).
(major), 15.21 min (minor).
4.3.7. Ethyl 2-[hydroxy-(2-nitro-phenyl)-methyl]-acrylate.7c 90% yield,
4.3.15. Ethyl (S)-2-[hydroxy-(2,4-dichloro-phenyl)-methyl]-acryl-
35% ee, [
a]
D þ100.0 (c 0.60, MeOH); 1H NMR (CDCl3, 500 MHz):
d
7.96
ate.13 66% yield, 7% ee; 1H NMR (CDCl3, 500 MHz):
d 7.52 (d,
(d, J¼8.1 Hz,1H), 7.75 (d, J¼7.8 Hz, 1H), 7.67–7.64 (m, 1H), 7.49–7.46 (m,
J¼8.4 Hz, 1H), 7.39 (d, J¼1.6 Hz, 1H), 7.30 (dd, J¼1.6 and 8.4 Hz, 1H),
6.34 (s,1H), 5.92 (d, J¼4.5 Hz,1H), 5.57 (s,1H), 4.23 (q, J¼7.1 Hz, 2H),
3.32 (d, J¼4.5 Hz, 1H), 1.29 (t, J¼7.1 Hz, 3H); HPLC analysis (OD-H
1H), 6.38 (s, 1H), 6.19 (s, 1H), 5.74 (s, 1H), 4.18 (q, J¼7.1 Hz, 2H), 3.43 (s,
1H), 1.22 (t, J¼7.1 Hz, 3H); HPLC analysis (OD-H column, ¼254 nm,
l
eluent: hexane/2-propanol¼90/10, flow rate: 1.0 mL/min): tR¼10.39
column,
l
¼220 nm, eluent: hexane/2-propanol¼95/5, flow rate:
min (major), 14.61 min (minor).
1.0 mL/min): tR¼9.71 min (major), 7.77 min (minor).
4.3.8. n-Butyl (S)-2-[hydroxy-(2-nitro-phenyl)-methyl]-acrylate.13 85%
4.3.16. Ethyl (S)-2-[hydroxy-(4-bromo-phenyl)-methyl]-acrylate.7c 36%
yield, 33% ee, [
a]
D þ71.6 (c 0.44, MeOH); 1H NMR (CDCl3, 500 MHz):
yield, 65% ee, [
a
]
þ17.6 (c 0.17, CHCl3); 1H NMR (CDCl3, 500 MHz):
D
d
7.96 (d, J¼8.1 Hz, 1H), 7.74 (d, J¼7.7 Hz, 1H), 7.66–7.63 (m, 1H), 7.49–
d
7.47 (d, J¼8.4 Hz, 2H), 7.26 (d, J¼8.4 Hz, 2H), 6.34 (s, 1H), 5.80 (s, 1H),
7.46 (m, 1H), 6.39 (s, 1H), 6.17 (s, 1H), 5.76 (s, 1H), 4.16–4.07 (m, 2H),
5.51 (d, J¼5.8 Hz, 1H), 4.18 (q, J¼7.1 Hz, 2H), 3.21 (d, J¼5.8 Hz, 1H),
3.43 (s, 1H), 1.59–1.53 (m, 2H), 1.33–1.24 (m, 2H), 0.89 (t, J¼7.4 Hz, 3H);
1.26 (t, J¼7.1 Hz, 3H); HPLC analysis (OD-H column, ¼220 nm, eluent:
l
HPLC analysis (OD-H column,
l
¼254 nm, eluent: hexane/2-
hexane/2-propanol¼95/5, flow rate: 0.8 mL/min): tR¼13.96 min
propanol¼90/10, flow rate: 1.0 mL/min): tR¼8.58min (major),
(major), 12.870 min (minor).
12.43 min (minor).
4.3.17. Ethyl (S)-2-[hydroxy-phenyl-methyl]-acrylate.16 24% yield,
4.3.9. Ethyl (S)-2-[hydroxy-(3-nitro-phenyl)-methyl]-acrylate.8a 96%
54% ee; 1H NMR (CDCl3, 500 MHz):
d 7.39–7.27 (m, 5H), 6.34 (s, 1H),
yield, 77% ee, [
a
]
D þ64.4 (c 0.45, MeOH); 1H NMR (CDCl3, 500 MHz):
5.81 (s, 1H), 5.57 (d, J¼5.5 Hz, 1H), 4.18 (q, J¼7.1 Hz, 2H), 3.48 (d,
d
8.27 (s, 1H), 8.16 (dd, J¼1.0 and 8.1 Hz, 1H), 7.76 (d, J¼7.7 Hz, 1H),
J¼5.5 Hz, 1H), 1.24 (t, J¼7.1 Hz, 3H); HPLC analysis (OJ column,
7.52 (t, J¼7.9 Hz, 1H), 6.42 (s, 1H), 5.89 (s, 1H), 5.63 (d, J¼6.2 Hz, 1H),
4.20 (q, J¼7.1 Hz, 2H), 3.33 (d, J¼6.2 Hz, 1H), 1.27 (t, J¼7.1 Hz, 3H);
l
¼220 nm, eluent: hexane/2-propanol¼90/10, flow rate: 0.8 mL/
min): tR¼21.93 min (major), 17.79 min (minor).
HPLC analysis (AS-H column,
l¼254 nm, eluent: hexane/2-
propanol¼95/5, flow rate: 0.8 mL/min): tR¼28.06 min (major),
4.3.18. Ethyl (S)-2-[hydroxy-(2-furfuryl)-methyl]-acrylate.12 42%
25.98 min (minor).
yield, 27% ee; 1H NMR (CDCl3, 500 MHz):
d 7.36 (s, 1H), 6.37 (s, 1H),
6.35–6.34 (m, 1H), 6.27 (d, J¼3.2 Hz, 1H), 5.92 (s, 1H), 5.59 (s, 1H),
4.3.10. n-Butyl (S)-2-[hydroxy-(3-nitro-phenyl)-methyl]-acrylate.14 94%
4.22 (q, J¼7.1 Hz, 2H), 3.41 (s, 1H), 1.28 (t, J¼7.1 Hz, 3H); HPLC
1
yield, 75% ee, [a D
]
þ48.8 (c 0.43, MeOH); H NMR (CDCl3, 500 MHz):
analysis (OD-H column,
l
¼220 nm, eluent: hexane/2-prop-
d
8.27 (s, 1H), 8.15 (dd, J¼1.0 and 8.1 Hz, 1H), 7.75 (d, J¼7.7 Hz, 1H), 7.53
anol¼90/10, flow rate: 0.8 mL/min): tR¼9.62 min (major),
(t, J¼8.0 Hz, 1H), 6.41 (s, 1H), 5.89 (s, 1H), 5.63 (d, J¼6.3 Hz, 1H), 4.14 (t,
J¼6.4 Hz, 2H), 3.34 (d, J¼6.3 Hz, 1H), 1.64–1.58 (m, 2H), 1.37–1.28
(m, 2H), 0.90 (t, J¼7.4 Hz, 3H); HPLC analysis (AD-H column,
11.31 min (minor).
Acknowledgements
l¼254 nm, eluent: hexane/2-propanol¼90/10, flow rate: 1.0 mL/min):
tR¼10.17 min (major), 11.20 min (minor).
We are grateful for the financial support from National Natural
Science Foundation of China (20772029) and the Program for New
Century Excellent Talents in University (NCET-07-0286).
4.3.11. Ethyl (S)-2-[hydroxy-(4-trifluoromethyl-phenyl)-methyl]-
acrylate.14 63% yield, 71% ee, [
a]
þ26.9 (c 0.26, CHCl3); 1H NMR
D
(CDCl3, 500 MHz):
d
7.61 (d, J¼8.2 Hz, 2H), 7.51 (d, J¼8.2 Hz, 2H),
Supplementary data
6.37 (s, 1H), 5.82 (s, 1H), 5.60 (s, 1H), 4.19 (q, J¼7.1 Hz, 2H), 3.25 (br,
1H), 1.26 (t, J¼7.1 Hz, 3H); HPLC analysis (OD-H column, ¼220 nm,
l
Supplementary data associated with this article can be found in
the online version, at doi:10.1016/j.tet.2009.07.066.
eluent: hexane/2-propanol¼95/5, flow rate: 0.8 mL/min): tR¼11.77
min (major), 10.64 min (minor).
References and notes
4.3.12. n-Butyl (S)-2-[hydroxy-(4-trifluoromethyl-phenyl)-methyl]-
acrylate.14 54% yield, 69% ee; 1H NMR (CDCl3, 400 MHz):
d
7.61 (d,
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