An efficient synthesis of enol phosphates via organic base-promoted addition of phosphites to 4-oxo-enoates

Article abstract of DOI:10.1016/j.tet.2012.05.021

A TMG catalyzed, practical and efficient hydrophosphorylation of 4-oxo-enoates by diethyl or diphenyl phosphite has been described. This protocol allows a convenient access to a variety of enol phosphates under mild conditions in good yield with excellent stereoselectivity.

Full text of DOI:10.1016/j.tet.2012.05.021

Tetrahedron 68 (2012) 6032e6037
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An efficient synthesis of enol phosphates via organic base-promoted addition
of phosphites to 4-oxo-enoates
*
*
Xiao-Yu Zhu, Jia-Rong Chen, Liang-Qiu Lu , Wen-Jing Xiao
Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University, 152 Luoyu Road, Wuhan, Hubei 430079, China
a r t i c l e i n f o
a b s t r a c t
Article history:
A TMG catalyzed, practical and efficient hydrophosphorylation of 4-oxo-enoates by diethyl or diphenyl
phosphite has been described. This protocol allows a convenient access to a variety of enol phosphates
under mild conditions in good yield with excellent stereoselectivity.
Received 15 January 2012
Received in revised form 27 April 2012
Accepted 4 May 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Available online 12 May 2012
Keywords:
Hydrophosphorylation
4-Oxo-enonate
Enol phosphate
High stereoselectivity
1. Introduction
thermodynamic). Therefore, the development of new efficient and
highly selective strategies for the preparation of enol phosphates is
Enol phosphates are an important class of organophosphates
that exhibit a variety of biological properties.1 For example, phos-
phenol pyruvate (PEP) 1 is well known high-energy species, which
plays an important role in transformation of ADP to ATP (Fig. 1).2
The natural cyclophostin 2 shows potent inhibition of acetyl cho-
linesterase (AChE) from the housefly (CSMA strain) and the brown
plant hopper. The cyclipostin 3 bearing a long chain lipophilic al-
cohol is potent inhibitor of hormone sensitive lipase (HSL).3
Moreover, diversely functionalized enol phosphates are of great
synthetic importance due to their versatile synthetic applications.4
The generally synthetic methods for enol phosphates are based on
still highly desirable.
Recently, Lee and co-workers have developed an elegant gold (I)
complex catalyzed addition of diphenyl phosphite to alkynes,
which afforded a variety of kinetic enol phosphates or the ther-
modynamically favored enol phosphates in high yield and selec-
tivity by using different ligands.6 Inspired by this pioneering
achievements, we envisioned that proper tuning of the steric hin-
drance of the reactants and reaction parameters would probably
provide another avenue for the synthesis of enol phosphates. As
part of our ongoing program on the development of asymmetric
conjugate addition reaction,7 we recently reported a highly enan-
tioselective Michael addition of nitroalkanes to 4-oxo-enoate 4a.7a
Based on these success and highly reactive nature of 4-oxo-enoates,
we continued to investigate the addition reaction of phosphites to
4-oxo-enoate 4a, which would provide a new approach to bioactive
phosphate derivatives (Scheme 1).8 However, in sharp contrast to
the previous examples of conjugate addition of dialkyl phosphites
Perkow reaction of a-haloketones or a-haloaldehydes with trialkyl
phosphites or the reaction of enolate anions with dialkyl phos-
phorochloridates.5 However, the wide application of these methods
are usually impeded by certain issues, such as formation of side
product and the selectivity of the corresponding product (kinetic vs
to b
-aroylacrylic acid (Scheme 1, eq. 1),9 the reactions of diethyl or
diphenyl phosphite and 4-oxo-enoates gave rise to the enol phos-
phates 6 in good yield and stereoselectivity by use of organic base
(Scheme 1, eq. 2).
2. Result and discussion
Fig. 1. Examples of biologically active enol phosphate derivatives.
Initially, the addition of diethyl phosphite (5a) to (E)-4-oxo-4-
phenylbut-2-enoate (4a) was selected as the test reaction using
30 mol % of DBU (1,8-diazabicycloundec-7-ene) as the catalyst in
* Corresponding authors. E-mail address: wxiao@mail.ccnu.edu.cn (W.-J. Xiao).
0040-4020/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2012.05.021

X.-Y. Zhu et al. / Tetrahedron 68 (2012) 6032e6037
6033
Table 2
Scope of the 4-oxo-enoates and dialkyl phosphitesa
Entry
R1
R2
4
R3
6
Yieldb (%)
1
2
3
4
5
6
7
8
Ph
Ph
Ph
Ph
p-CH3Ph
p-FPh
Et
Me
iPr
Bn
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Me
Et
Et
(4a)
(4b)
(4c)
(4d)
(4e)
(4f)
(4g)
(4h)
(4i)
(4j)
(4k)
(4l)
(4m)
(4a)
(4a)
(4n)
(4o)
(4p)
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Ph
Ph
Ph
Ph
Ph
6a
66 (24)
57
52
51
53
62
58
60
38 (45)
63
53
71
55
58
83
82
54
82
6b
6c
6d
6e
6f
6g
6h
6i
6j
6k
6l
6m
6n
6n
6o
6p
6q
Scheme 1. Strategy for the synthesis of enol phosphates.
toluene at room temperature. Interestingly, the reaction proceeded
efficiently and provided the unexpected 6a as the main product in
56% yield accompanied with a small amount of Michael-type ad-
duct (28% yield) and some other unknown side products (Table 1,
entry 1). The structure of 6a was fully characterized by 1H, 13C, and
31P NMR analysis. Encouraged by these results, we continued to
examine other bases for this reaction and found that the bases have
great impact on this reaction. For example, the use of commercially
available and cheap TMG (1,1,3,3-tetramethylguanidine) resulted in
a slight increase of yield while other bases, such as DABCO (1,4-
diazabicyclo[2.2.2]octane), pyridine, Et3N, KOH, and K2CO3 led to
low yield or even no desired product (entries 3e8). A brief survey of
common solvents showed that CHCl3 proved to be the best of
choice (entry 12, 64% yield). Moreover, increasing the amount of
catalyst to 50 mol % could accelerate the reaction and afford the
desired product in 66% yield (entry 18).
With the optimized conditions in hand, we then investigated
the scope and limitations of this reaction with a variety of 4-oxo-
enoates and phosphites (Table 2). Firstly, we found that this strat-
egy is general with respect to the ester moiety of 4-oxo-enoates
(entries 1e4). Changing the ethyl group to methyl, isopropyl, and
benzyl groups gave the corresponding products in comparable
yields (51e57%). As shown in entries 5e13, the electronic and steric
properties of the aromatic ring of 4-oxo-enoates have little impact
on the yields. For example, in the case of 4-oxo-enoates bearing
p-ClPh
p-BrPh
p-OCH3Ph
m-OCH3Ph
m-ClPh
m-BrPh
o-OCH3Ph
Ph
9
10
11
12
13
14c
15d
16d
17d
18d
Ph
p-BrPh
p-NO2Ph
m-NO2Ph
19d
(4q)
Ph
6r
85
a
Reaction conditions: 4 (0.2 mmol), 5a (0.4 mmol), TMG (0.1 mmol), 1 mL CHCl3,
room temperature, 10w24 h (entries 1e13) or 4 (0.2 mmol), 5b (0.4 mmol), TMG
(0.1 mmol), 2 mL toluene, ꢀ20 ꢁC, 0.5w5 h (entries 14e19).
b
Isolated yield based on 4. Values in parentheses are the yields of the Michael-
type adduct.
c
Performed in 2 mL toluene at room temperature.
Performed in 2 mL toluene at ꢀ20 ꢁC.
d
CH3, F, Cl, and Br at the para-position of aryl ring, the desired enol
phosphates were obtained in good yields (entries 5e8) with the
exception of para-MeO substituted 4i (entry 9, 38% yield). More-
over, it was found that the 4-oxo-enoates with electron-
withdrawing and donating groups, such as Cl, Br, and MeO at
meta- and ortho- position of phenyl ring also proceeded smoothly
to give the products in a range of 53e71% yield (entries 10e13). It
was found that toluene is superior to chloroform in the case of
diphenyl phosphate and the enol phosphate was obtained in a yield
of 58% (entry 14). After brief further screening of the conditions, we
found that the reactions of 4a, 4n, 4o, 4p with diphenyl phosphate
can give the corresponding enol phosphate derivatives in satisfying
yields in toluene at ꢀ20 ꢁC (entries 15e18). It is worth noting that
Table 1
Optimization studiesa
Entry
Solvent
Catalyst
Time (h)
Yieldb (%)
1
2
3
4
5
6
7
8
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
Toluene
DMF
Xylene
CH2Cl2
Cl(CH2)2Cl
CHCl3
Et2O
THF
DMF
CH3CN
C2H5OH
CHCl3
DBUc
TMGd
DABCOe
Pyridine
Et3N
2
2
56
58
96
96
96
96
96
2
2
3
2
20
2
N.R.f
N.R.f
Trace
20
4-oxo-enoate 4q with a methyl group at b-carbon can also partic-
ipate in the reaction to give the desired product in 85% yield after
5 h (entry 19).
Finally, the structure of the enol phosphate 6o was un-
ambiguously confirmed by X-ray analysis (Fig. 2). Moreover, it was
found that the enol phosphate 6o has cis-configuration.10
KOH
K2CO3
K2CO3
TMG
TMG
TMG
TMG
TMG
TMG
TMG
23
52
34
32
25
64
51
48
43
15
46
66
9
10
11
12
13
14
15
16
17
18g
2
2
2
2
TMG
TMG
TMG
12
a
Reaction conditions: 4a (0.2 mmol), 5a (0.4 mmol), catalyst (0.06 mmol), 1 mL
solvent, room temperature.
b
Isolated yield based on 4a.
c
DBU¼1,8-diazabicycloundec-7-ene.
d
TMG¼1,1,3,3-tetramethylguanidine.
e
DABCO¼1,4-diazabicyclo[2.2.2]octane.
f
No reaction.
g
50 mol % TMG was used.
Fig. 2. X-ray crystal structure of enol phosphate 6o.

6034
X.-Y. Zhu et al. / Tetrahedron 68 (2012) 6032e6037
Though further detailed mechanistic studies are needed, we
4.2. 4-Oxo-enoates were prepared according to the literature
procedures7a
proposed two possible pathways for this reaction based on the
previous related work on phosphate chemistry (Scheme 2).11 Tak-
ing the model reaction as example, in path a, the nucleophilic ad-
4.2.1. (E)-Ethyl 4-(3-chlorophenyl)-4-oxobut-2-enoate (4k). Yellow
solid, yield: 92%. 1H NMR (400 MHz, CDCl3)
dition of (EtO)2P(OH) 5a to the
b
-carbon of 4a in the presence of
d
7.97 (t, J¼1.8 Hz, 1H),
base gave the enolate anion I. Then, the enolate anion I underwent
the protonation to give the formal Michael adduct 7a or cylization/
rearrangement sequence to afford the corresponding product 6a.
However, we can’t exclude the pathway b at the current stage,
which involves the 1,2-addition of phosphite anion to the carbonyl
group of 4a and the subsequent phospha-Brook rearrangement to
give the intermediate enol phosphate anion IV. The following
protonation of enol phosphate anion IV should result in a cis/trans
mixture of enol phosphate 6. To get some insights into the possible
mechanism, we carried out the reaction with 7a under the optimal
conditions in the presence of TMG and didn’t observe any forma-
tion of 6a. Moreover, the 1H NMR analysis of the reaction mixture
showed that only cis-configured products were observed. There-
fore, path a (intramolecular cylization/rearrangement sequence) is
more favorable than path b.
7.84e7.89 (m, 2H), 7.59 (dd, J¼8.0, 1.0 Hz, 1H), 7.47 (t, J¼7.9 Hz, 1H),
6.90(d, J¼15.5 Hz,1H), 4.31 (q, J¼7.1Hz,2H),1.36(t, J¼7.1Hz,3H)ppm;
13C NMR (100 MHz, CDCl3)
d 188.1, 165.2, 138.0, 135.8, 135.3, 133.7,
133.2, 130.1, 128.7, 126.8, 61.5, 14.1 ppm. MS (EI) m/z 240 (MþH)þ.
4.2.2. (E)-Ethyl 2-methyl-4-oxo-4-phenylbut-2-enoate
(4q). Colorless oil, 48% yield. 1H NMR (400 MHz, CDCl3)
d
7.96e7.98 (m, 2H), 7.72e7.73 (m, 1H), 7.60 (t, J¼7.4 Hz, 1H), 7.50 (t,
J¼7.6 Hz, 2H), 4.31 (dd, J¼14.3, 7.1 Hz, 2H), 2.19 (s, 3H), 1.37 (t,
J¼7.1 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3)
d 192.5, 167.3, 140.7,
137.4, 133.5, 131.7, 128.6, 61.5, 14.7, 14.1 ppm. MS (EI) m/z 218 (Mþ).
4.3. General procedure for the synthesis of compounds
6ae6m
To a solution of 4-oxo-enoate 4 (0.2 mmol) and diethyl phos-
phite 5a (0.4 mmol) in chloroform (1 mL) was added TMG
(0.1 mmol) at room temperature. After completed (monitored by
TLC analysis), the mixture was purified by column chromatography
on silica gel (PE/EA¼20/1w5/1 as eluent) to afford the corre-
sponding product 6.
4.3.1. (Z)-Ethyl 4-((diethoxyphosphoryl)oxy)-4-phenylbut-3-enoate
(6a). Colorless oil, 66% yield. 1H NMR (400 MHz, CDCl3)
d 7.55
(dd, J¼7.9, 1.6 Hz, 2H), 7.31e7.37 (m, 3H), 5.85e5.89 (m, 1H),
4.01e4.21 (m, 6H), 3.47 (dd, J¼7.0, 2.8 Hz, 2H), 1.21e1.30 (m, 9H)
ppm; 13C NMR (100 MHz, CDCl3)
d
171.2, 147.5 (d, J¼9.2 Hz), 134.9,
128.6, 128.2, 125.6, 109.3 (d, J¼6.5 Hz), 64.4 (d, J¼5.9 Hz), 60.7, 31.8,
Scheme 2. Two possible pathways for the addition of phosphate 5a to 4-oxo-enoate
4a.
15.9 (d, J¼6.9 Hz), 14.1 ppm; 31P NMR (161 MHz, CDCl3)
d
ꢀ6.27 ppm. FTIR (KBr, cmꢀ1): 3489, 3064, 2985, 2936, 2910, 1736,
1667, 1447, 1393, 1371, 1342, 1264, 1165, 1099, 1023, 983, 965, 887,
804, 768, 697, 625, 505. HRMS (ESI): Calcd for C16H23O6P [MþNa]þ:
365.1130; found: 365.1137.
3. Conclusion
In summary, we have developed an efficient addition reaction of
diethyl or diphenyl phosphite to 4-oxo-enoates by the use of simple
and cheap TMG as the catalyst. The reaction provided a practical
access to a wide range of enol phosphates. Considering the readily
availability of the phosphorylation reagent and the operational
simplicity of the procedure, the current methodology should find
wide application in organic synthesis and medicinal chemistry.
Further mechanistic study and synthetic transformations of the
enol phosphates are still ongoing in our laboratory.
4.3.2. Ethyl 2-((diethoxyphosphoryl)oxy)-4-oxo-4-phenylbutanoate
(7a). Colorless oil, 24% yield. 1H NMR (400 MHz, CDCl3)
d 7.99 (d,
J¼7.4 Hz, 2H), 7.59 (t, J¼7.3 Hz, 1H), 7.47 (t, J¼7.6 Hz, 2H), 4.16e4.25
(m, 6H), 3.80e3.88 (m, 1H), 3.63e3.73 (m, 1H), 3.41e3.49 (m, 1H),
1.26e1.39 (m, 9H) ppm; 13C NMR (100 MHz, CDCl3)
d 196.4 (d,
J¼15.3 Hz), 168.4, 136.0, 133.5, 128.6, 128.1, 62.91 (d, J¼6.5 Hz),
128.2, 125.6, 109.3 (d, J¼6.5 Hz), 61.6, 40.9, 39.5, 36.0, 16.3,
14.0 ppm; 31P NMR (161 MHz, CDCl3) 19.61 ppm. FTIR (KBr, cmꢀ1):
d
3470, 3063, 2983, 2933, 2873, 1734, 1690, 1598, 1581, 1449, 1392,
1369, 1259, 1222, 1158, 1097, 1024, 974, 891, 859, 800, 758, 692, 562,
511. HRMS (ESI): Calcd for C16H23O6P [MþNa]þ: 365.1130; found:
365.1104.
4. Experimental section
4.1. General information
4.3.3. (Z)-Methyl 4-((diethoxyphosphoryl)oxy)-4-phenylbut-3-
Unless otherwise noted, materials were used as commercial
suppliers. All solvents were purified by standard method. Flash
column chromatography was performed using 200e300 mesh sil-
ica gel.
enoate (6b). Colorless oil, 57% yield. 1H NMR (400 MHz, CDCl3)
d
7.56 (dd, J¼8.0, 1.3 Hz, 2H), 7.32e7.37 (m, 3H), 5.85e5.89 (m, 1H),
4.01e4.15 (m, 4H), 3.72 (s, 3H), 3.49 (dd, J¼6.9, 2.8 Hz, 2H),
1.21e1.25 (m, 6H) ppm; 13C NMR (100 MHz, CDCl3)
171.7, 147.5 (d,
d
1H NMR, 13C NMR, and 31P NMR spectra were recorded on
Varian-Mercury 400/600 (400/600 MHz) spectrometers. Chemical
J¼9.1 Hz), 134.8, 128.7, 128.2, 125.5, 109.1 (d, J¼6.4 Hz), 64.5 (d,
J¼5.5 Hz), 51.9, 31.6, 15.9 (d, J¼6.9 Hz) ppm; 31P NMR (161 MHz,
shifts (
d
) are reported in parts per million (ppm) and coupling
CDCl3)
d
ꢀ6.74 ppm. FTIR (KBr, cmꢀ1): 3484, 3063, 2987, 2911, 1739,
constants (J) in Hertz. Data are reported as follows: chemical shift
1667, 1494, 1443, 1395, 1351, 1262, 1207, 1164, 1100, 1021, 918, 887,
816, 768, 697, 624, 519. HRMS (ESI): Calcd for C15H21O6P [MþNa]þ:
351.0973; found: 351.1023.
(
d
), multiplicity (s¼singlet, d¼doublet, t¼triplet, q¼quartet,
dd¼doublet of doublets, m¼multiplet). Mass spectra were mea-
sured on a Finnigan Trace MS spectrometer (EI) or API 2000 LC/MS/
MS (ESI-MS). Elementary analyses were taken on a Vario EL III el-
ementary analysis instrument.
4.3.4. (Z)-Isopropyl 4-((diethoxyphosphoryl)oxy)-4-phenylbut-3-
enoate (6c). Colorless oil, 52% yield. 1H NMR (400 MHz, CDCl3)

X.-Y. Zhu et al. / Tetrahedron 68 (2012) 6032e6037
6035
d
7.55 (dd, J¼8.0, 1.5 Hz, 2H), 7.28e7.33 (m, 3H), 5.85e5.89 (m, 1H),
5.02e5.08 (m, 1H), 3.99e4.11 (m, 4H), 3.44 (dd, J¼6.9, 2.9 Hz, 2H),
1.21e1.27 (m, 12H) ppm; 13C NMR (100 MHz, CDCl3)
170.7, 147.4
ppm; 13C NMR (100 MHz, CDCl3)
d
171.0, 146.5 (d, J¼9.0 Hz), 133.8,
131.4, 127.1, 122.8, 110.0 (d, J¼6.5 Hz), 64.6 (d, J¼5.7 Hz), 60.9, 31.8,
d
16.0 (d, J¼6.8 Hz), 14.2 ppm; 31P NMR (161 MHz, CDCl3)
(d, J¼9.0 Hz), 134.9, 128.6, 128.2, 125.6, 109.5 (d, J¼6.2 Hz), 68.2,
d
ꢀ6.68 ppm. FTIR (KBr, cmꢀ1): 3489, 3069, 2984, 2936, 2909, 1909,
64.4 (d, J¼5.8 Hz), 32.1, 21.8, 15.9 (d, J¼7.0 Hz) ppm; 31P NMR
1734, 1689, 1587, 1487, 1446, 1396, 1370, 1342, 1261, 1162, 1099,
1071, 1024, 887, 818, 669, 627, 508. HRMS (ESI): Calcd for
C16H22BrO6P [MþH]þ: 421.0416; found: 421.0369.
(161 MHz, CDCl3)
d
ꢀ6.68 ppm. FTIR (KBr, cmꢀ1): 3386, 2983, 2937,
1732, 1667, 1494, 1448, 1371, 1266, 1179, 1107, 1018, 971, 908, 882,
819, 768, 698, 626, 504. HRMS (ESI): Calcd for C17H25O6P [MþH]þ:
357.1467; found: 357.1449.
4.3.10. (Z)-Ethyl 4-((diethoxyphosphoryl)oxy)-4-(4-methoxyphenyl)
but-3-enoate (6i). Colorless oil, 38% yield. 1H NMR (400 MHz,
4.3.5. (Z)-Benzyl 4-((diethoxyphosphoryl)oxy)-4-phenylbut-3-enoate
CDCl3)
1H), 4.02e4.20 (m, 6H), 3.82 (s, 3H), 3.44 (dd, J¼6.9, 2.8 Hz, 2H),
1.23e1.30 (m, 9H) ppm; 13C NMR (100 MHz, CDCl3)
171.4, 159.9,
d
7.50 (d, J¼8.8 Hz, 2H), 6.87 (d, J¼8.8 Hz, 2H), 5.72e5.76 (m,
(6d). Colorless oil, 51% yield. 1H NMR (400 MHz, CDCl3)
d 7.55 (dd,
J¼7.9, 1.6 Hz, 2H), 7.26e7.38 (m, 8H), 5.86e5.90 (m, 1H), 5.17 (s, 2H),
d
3.98e4.08 (m, 4H), 3.53 (dd, J¼6.9, 2.8 Hz, 2H), 1.18e1.22 (m, 6H)
147.3 (d, J¼9.1 Hz), 127.5, 127.0, 113.5, 107.4 (d, J¼6.5 Hz), 64.5 (d,
ppm; 13C NMR (100 MHz, CDCl3)
d
171.1, 147.7 (d, J¼8.9 Hz), 135.71,
J¼5.8 Hz), 60.7, 55.2, 31.8, 16.0 (d, J¼7.0 Hz), 14.2 ppm; 31P NMR
134.9, 128.7, 128.5, 128.2, 125.6, 109.0 (d, J¼6.3 Hz), 66.6, 64.5 (d,
(161 MHz, CDCl3)
d
ꢀ6.76 ppm. FTIR (KBr, cmꢀ1): 3474, 2984, 2934,
J¼5.9 Hz), 31.8, 15.9 (d, J¼6.9 Hz) ppm; 31P NMR (161 MHz, CDCl3)
2843, 1736, 1667, 1609, 1513, 1463, 1446, 1392, 1371, 1258, 1174,
1099, 1027, 889, 801, 761, 626, 504. HRMS (ESI): Calcd for C17H25O7P
[MþNa]þ: 395.1236; found: 395.1221.
d
ꢀ6.58 ppm. FTIR (KBr, cmꢀ1): 3477, 3064, 3034, 2985, 2937, 2910,
1960, 1886, 1736, 1687, 1601, 1496, 1449, 1389, 1345, 1261, 1159,
1100, 1023, 907, 817, 767, 698, 625, 506. HRMS (ESI): Calcd for
C21H25O6P [MþNa]þ: 427.1286; found: 427.1263.
4.3.11. Ethyl 2-(diethoxyphosphoryl)-4-(4-methoxyphenyl)-4-
oxobutanoate (7i). Colorless oil, 45% yield. 1H NMR (400 MHz,
4.3.6. (Z)-Ethyl 4-((diethoxyphosphoryl)oxy)-4-(p-tolyl)but-3-
CDCl3)
6H), 3.87 (s, 3H), 3.62e3.80 (m, 2H), 3.37e3.43 (m, 1H), 1.28e1.39
(m, 9H) ppm; 13C NMR (100 MHz, CDCl3)
d
7.97 (d, J¼8.5 Hz, 2H), 6.94 (d, J¼8.4 Hz, 2H), 4.17e4.25 (m,
enoate (6e). Colorless oil, 53% yield. 1H NMR (400 MHz, CDCl3)
d
7.44 (d, J¼8.1 Hz, 2H), 7.15 (d, J¼8.0 Hz, 2H), 5.80e5.84 (m, 1H),
3.99e4.20 (m, 6H), 3.45 (dd, J¼6.9, 2.7 Hz, 2H), 2.35 (s, 3H),
1.23e1.30 (m, 9H) ppm; 13C NMR (100 MHz, CDCl3)
171.3, 147.6 (d,
d
194.8 (d, J¼15.5 Hz),
168.5 (d, J¼5.0 Hz), 163.7, 130.4, 129.0, 113.7, 62.9 (d, J¼5.1 Hz), 61.6,
d
55.4, 40.9, 39.5, 35.5, 16.3, 14.0 ppm; 31P NMR (161 MHz, CDCl3)
J¼9.1 Hz), 138.6, 132.1, 128.9, 125.5, 108.3 (d, J¼4.6 Hz), 64.4 (d,
d
19.84 ppm. FTIR (KBr, cmꢀ1): 3470, 2968, 2843, 2770, 2577, 2410,
J¼5.8 Hz), 60.7, 31.8, 21.2, 16.0 (d, J¼6.9 Hz), 14.2 ppm; 31P NMR
2049, 1736, 1677, 1601, 1512, 1463, 1366, 1260, 1157, 1097, 1023, 894,
834, 802, 765, 712, 636, 608, 563, 505, 434. MS (EI) m/z 375
(MþH)þ.
(161 MHz, CDCl3)
d
ꢀ6.75 ppm. FTIR (KBr, cmꢀ1): 3490, 2984, 2933,
2873, 1737, 1667, 1613, 1513, 1447, 1394, 1371, 1342, 1265, 1166, 1099,
1030, 965, 889, 819, 761, 695, 632, 520. HRMS (ESI): Calcd for
C17H25O6P [MþH]þ: 357.1467; found: 357.1445.
4.3.12. (Z)-Ethyl 4-((diethoxyphosphoryl)oxy)-4-(3-methoxyphenyl)
but-3-enoate (6j). Colorless oil, 63% yield. 1H NMR (400 MHz,
4.3.7. (Z)-Ethyl 4-((diethoxyphosphoryl)oxy)-4-(4-fluorophenyl)but-
3-enoate (6f). Colorless oil, 62% yield. 1H NMR (600 MHz, CDCl3)
CDCl3)
d
7.24e7.30 (m, 1H), 7.15 (d, J¼7.8 Hz, 1H), 7.09 (t, J¼1.8 Hz,
1H), 6.87 (dd, J¼8.1, 2.5 Hz, 1H), 5.87e5.91 (m, 1H), 4.04e4.21 (m,
6H), 3.82 (s, 3H), 3.47 (dd, J¼6.9, 2.8 Hz, 2H), 1.23e1.30 (m, 9H)
d
7.54 (dd, J¼8.7, 5.3 Hz, 2H), 7.04 (t, J¼8.6 Hz, 2H), 5.80e5.82 (m,
1H), 4.04e4.20 (m, 6H), 3.45 (dd, J¼6.9, 2.7 Hz, 2H), 1.24e1.30 (m,
9H) ppm; 13C NMR (100 MHz, CDCl3)
171.2, 164.1, 161.6, 146.5 (d,
ppm; 13C NMR (100 MHz, CDCl3)
d
171.1, 159.3, 147.2 (d, J¼9.1 Hz),
d
136.2, 129.2, 118.0, 114.4, 110.9, 109.5 (d, J¼6.4 Hz), 64.4 (d,
J¼8.8 Hz), 131.1, 127.5 (d, J¼8.3 Hz), 115.2 (d, J¼21.8 Hz), 109.2 (d,
J¼5.8 Hz), 60.7, 55.2, 31.8, 15.9 (d, J¼7.0 Hz), 14.1 ppm 31P NMR
J¼5.8 Hz), 64.5 (d, J¼5.6 Hz), 60.9, 31.8, 16.0 (d, J¼6.9 Hz), 14.2 ppm;
(161 MHz, CDCl3)
d
ꢀ6.73 ppm. FTIR (KBr, cmꢀ1): 3489, 3070, 2984,
31P NMR (161 MHz, CDCl3)
d
ꢀ6.57 ppm. FTIR (KBr, cmꢀ1): 3489,
2839, 1943, 1908, 1868, 1735, 1668, 1602, 1583, 1489, 1432, 1394,
1371, 1263, 1209, 1164, 1098, 1024, 974, 916, 798, 700, 664, 637, 506,
485. HRMS (ESI): Calcd for C17H25O7P [MþNa]þ: 395.1236; found:
395.1166.
3071, 2985, 2935, 2911, 1736, 1688, 1669, 1603, 1510, 1478, 1446,
1394, 1371, 1343, 1263, 1233, 1162, 1099, 1027, 984, 965, 890, 810,
520. HRMS (ESI): Calcd for C16H22FO6P [MþNa]þ: 383.1036; found:
383.1032.
4.3.13. (Z)-Ethyl 4-(3-chlorophenyl)-4-((diethoxyphosphoryl)oxy)
4.3.8. (Z)-Ethyl 4-(4-chlorophenyl)-4-((diethoxyphosphoryl)oxy)but-
but-3-enoate (6k). Colorless oil, 53% yield. 1H NMR (600 MHz,
3-enoate (6g). Colorless oil, 58% yield. 1H NMR (400 MHz, CDCl3)
CDCl3)
5.89e5.92 (m, 1H), 4.06e4.20 (m, 6H), 3.46 (dd, J¼6.8, 2.6 Hz, 2H),
1.25e1.30 (m, 9H) ppm; 13C NMR (100 MHz, CDCl3)
170.9, 146.1
d 7.54 (s, 1H), 7.44e7.45 (m, 1H), 7.28e7.29 (m, 2H),
d
7.49 (d, J¼8.6 Hz, 2H), 7.32 (d, J¼8.6 Hz, 2H), 5.86e5.90 (m, 1H),
4.04e4.21 (m, 6H), 3.46 (dd, J¼6.9, 2.8 Hz, 2H), 1.24e1.30 (m, 9H)
ppm; 13C NMR (100 MHz, CDCl3)
d
d
171.1, 146.4 (d, J¼9.0 Hz), 134.5,
(d, J¼9.0 Hz), 136.7, 134.2, 129.5, 128.6, 125.6, 123.7, 110.6 (d,
133.4, 128.4, 126.9, 109.9 (d, J¼6.2 Hz), 64.6 (d, J¼5.8 Hz), 60.9, 31.8,
J¼6.2 Hz), 64.5 (d, J¼5.7 Hz), 60.8, 31.8, 15.9 (d, J¼6.8 Hz),
16.0 (d, J¼6.8 Hz), 14.2 ppm; 31P NMR (161 MHz, CDCl3)
14.1 ppm; 31P NMR (161 MHz, CDCl3)
d
ꢀ6.71 ppm. FTIR (KBr,
d
ꢀ6.58 ppm. FTIR (KBr, cmꢀ1): 1635, 1619, 1591, 1562, 1530, 1497,
cmꢀ1): 3491, 3069, 2984, 2936, 2910, 1736, 1693, 1667, 1595, 1568,
1477, 1445, 1418, 1394, 1371, 1342, 1263, 1166, 1098, 1027, 968, 903,
790, 745, 696, 633, 532, 470. HRMS (ESI): Calcd for C16H22ClO6P
[MþH]þ: 377.0921; found: 377.0868.
1472, 1447, 1410, 1391, 1320, 1300, 1245, 1146, 1097, 1048, 1030, 997,
908, 843, 797, 742, 729, 714, 684, 648, 625, 572, 523, 489. FTIR (KBr,
cmꢀ1): 3486, 3069, 2984, 2936, 2910, 1736, 1689, 1593, 1491, 1446,
1399, 1370, 1342, 1263, 1165, 1094, 1026, 887, 819, 681, 629, 524.
HRMS (ESI): Calcd for C16H22ClO6P [MþNa]þ: 399.0740; found:
399.0702.
4.3.14. (Z)-Ethyl 4-(3-bromophenyl)-4-((diethoxyphosphoryl)oxy)
but-3-enoate (6l). Colorless oil, 71% yield. 1H NMR (400 MHz,
CDCl3)
1H), 5.88e5.92 (m, 1H), 4.07e4.21 (m, 6H), 3.46 (dd, J¼6.9, 2.8 Hz,
2H), 1.25e1.31 (m, 9H) ppm; 13C NMR (100 MHz, CDCl3)
170.9,
d
7.70 (s, 1H), 7.47 (dd, J¼16.8, 8.0 Hz, 2H), 7.22 (t, J¼7.9 Hz,
4.3.9. (Z)-Ethyl 4-(4-bromophenyl)-4-((diethoxyphosphoryl)oxy)but-
3-enoate (6h). Colorless oil, 60% yield. 1H NMR (400 MHz, CDCl3)
d
d
7.48 (d, J¼8.6 Hz, 2H), 7.43 (d, J¼8.7 Hz, 2H), 5.87e5.91 (m, 1H),
146.0 (d, J¼8.9 Hz), 136.9, 131.5, 129.7, 128.5, 124.1, 122.3, 110.6 (d,
4.04e4.21 (m, 6H), 3.45 (dd, J¼6.9, 2.8 Hz, 2H), 1.25e1.30 (m, 9H)
J¼5.8 Hz), 64.5 (d, J¼5.6 Hz), 60.8, 31.8, 15.9 (d, J¼6.9 Hz),

6036
X.-Y. Zhu et al. / Tetrahedron 68 (2012) 6032e6037
14.1 ppm; 31P NMR (161 MHz, CDCl3)
d
ꢀ6.74 ppm. FTIR (KBr,
1346, 1261, 1213, 1161, 1100, 1025, 963, 853, 811, 756, 691, 621, 576,
507. HRMS (ESI): Calcd for C24H22NO8P [MþH]þ: 484.1161; found:
484.1066.
cmꢀ1): 3487, 3067, 2983, 2935, 2909, 1736, 1691, 1593, 1563, 1475,
1445, 1414, 1394, 1370, 1261, 1213, 1161, 1098, 1024, 967, 898, 859,
799, 748, 694, 631, 528, 504, 465. HRMS (ESI): Calcd for
C16H22BrO6P [MþNa]þ: 443.0235; found: 443.0232.
4.4.4. (Z)-Ethyl 4-((diphenoxyphosphoryl)oxy)-4-(3-nitrophenyl)but-
3-enoate (6q). Colorless oil, 82% yield. 1H NMR (400 MHz, CDCl3)
4.3.15. (Z)-Ethyl 4-((diethoxyphosphoryl)oxy)-4-(2-methoxyphenyl)
d
8.34 (t, J¼1.8 Hz, 1H), 8.14 (dd, J¼8.1, 2.0 Hz, 1H), 7.81 (d, J¼7.9 Hz,
but-3-enoate (6m). Colorless oil, 55% yield. 1H NMR (400 MHz,
1H), 7.46 (d, J¼8.0 Hz, 1H), 7.32 (t, J¼7.9 Hz, 4H), 7.15e7.21 (m, 6H),
6.09e6.13 (m,1H), 4.15 (q, J¼7.1 Hz, 2H), 3.44 (dd, J¼6.9, 2.9 Hz, 2H),
CDCl3)
d
7.43 (dd, J¼7.6, 1.7 Hz, 1H), 7.28e7.33 (m, 1H), 6.89e6.96
(m, 2H), 5.79e5.83 (m, 1H), 4.17 (q, J¼7.1 Hz, 2H), 3.93e4.08 (m,
1.26 (d, J¼7.1 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3)
d 170.4, 150.1
4H), 3.85 (s, 3H), 3.46 (dd, J¼6.9, 2.6 Hz, 2H), 1.28 (t, J¼7.1 Hz,
(d, J¼7.1 Hz), 148.2, 145.3 (d, J¼9.0 Hz), 136.0, 131.3, 129.9, 129.4,
125.7, 123.5, 120.6 119.8 (d, J¼4.7 Hz), 112.9 (d, J¼6.5 Hz), 61.1, 31.7,
3H), 1.17e1.21 (m, 6H) ppm; 13C NMR (150 MHz, CDCl3)
d 171.3,
156.9, 144.6 (d, J¼8.9 Hz), 130.0, 124.1, 120.1, 112.4 (d, J¼7.2 Hz),
14.1 ppm; 31P NMR (161 MHz, CDCl3)
d
ꢀ18.23 ppm. FTIR (KBr,
110.8, 64.1 (d, J¼6.3 Hz), 60.6, 55.4, 31.7, 15.8 (d, J¼7.0 Hz, 7H),
cmꢀ1): 3384, 3077, 2984, 1946, 1733, 1591, 1533, 1489, 1350, 1260,
1212, 1160, 1099, 1026, 964, 853, 807, 769, 688, 619, 582, 503. HRMS
(ESI): Calcd for C24H22NO8P [MþNa]þ: 506.0981; found: 506.0962.
14.1 ppm; 31P NMR (161 MHz, CDCl3)
d
ꢀ7.18 ppm. FTIR (KBr,
cmꢀ1): 3485, 2984, 2842, 1739, 1676, 1606, 1577, 1513, 1446, 1416,
1368, 1258, 1162, 1101, 1025, 980, 892, 836, 802, 758, 639, 588,
528. HRMS (ESI): Calcd for C17H25O7P [MþNa]þ: 395.1236; found:
395.1205.
4.4.5. (Z)-Ethyl 4-((diphenoxyphosphoryl)oxy)-2-methyl-4-
phenylbut-3-enoate (6r). Colorless oil, 85% yield. 1H NMR
(400 MHz, CDCl3) d 7.50e7.53 (m, 2H), 7.28e7.33 (m, 6H), 7.14e7.20
4.4. General procedure for the synthesis of compounds 6ne6r
(m, 5H), 7.06 (d, J¼8.4 Hz, 2H), 5.78 (dd, J¼10.0, 1.7 Hz, 1H),
4.06e4.15 (m, 2H), 3.74e3.82 (m, 1H), 1.31 (d, J¼7.1 Hz, 3H), 1.21 (t,
To a solution of 4-oxo-enoate 4 (0.2 mmol) and diphenyl
phosphite 5b (0.4 mmol) in toluene (2 mL) was added TMG
(0.1 mmol) at ꢀ20 ꢁC. After completed (monitored by TLC analy-
sis), the mixture was purified by column chromatography on silica
gel (PE/EA¼20/1e10/1 as eluent) to afford the corresponding
product 6.
J¼7.1 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3)
d 174.2, 150.4, 146.6
(d, J¼9.5 Hz), 134.4, 129.7 (d, J¼5.0 Hz), 128.9, 128.3, 125.9, 125.4 (d,
J¼12.0 Hz), 120.0 (dd, J¼16.6, 4.8 Hz), 116.8 (d, J¼6.9 Hz), 60.8, 37.3,
18.1, 14.1 ppm; 31P NMR (161 MHz, CDCl3)
d
ꢀ18.4 ppm. FTIR (KBr,
cmꢀ1): 3386, 2983, 2449, 1732, 1662, 1632, 1596, 1491, 1374, 1259,
1215, 1187, 1161, 1095, 1023, 966, 811, 756, 692, 521. HRMS (ESI):
Calcd for C25H25O6P: [MþNa]þ: 475.1286; found: 475.1287.
4.4.1. (Z)-Ethyl 4-((diphenoxyphosphoryl)oxy)-4-phenylbut-3-enoate
(6n). Colorless oil, 83% yield. 1H NMR (400 MHz, CDCl3)
Acknowledgements
d
7.50e7.53 (m, 2H), 7.28e7.30 (m, 7H), 7.10e7.17 (m, 6H),
5.93e5.97 (m, 1H), 4.11 (q, J¼7.1 Hz, 2H), 3.40 (dd, J¼7.0, 2.9 Hz,
We are grateful to the National Science Foundation of China (NO.
21072069 and 21002036), the National Basic Research Program of
China (2011CB808603), and the Program for Chang-jiang Scholars
and Innovation Research Team in University (IRT0953) for support
of this research.
2H), 1.22 (t, J¼7.1 Hz, 3H) ppm; 13C NMR (100 MHz, CDCl3)
d 170.8,
150.2 (d, J¼7.3 Hz), 147.5 (d, J¼9.5 Hz), 134.0, 129.6, 128.8, 125.5 (d,
J¼15.7 Hz), 119.9 (d, J¼4.8 Hz), 109.9 (d, J¼6.9 Hz), 60.7, 31.6,
14.0 ppm; 31P NMR (161 MHz, CDCl3)
d
ꢀ18.23 ppm. FTIR (KBr,
cmꢀ1): 3453, 3066, 2982, 2936, 2906, 2378, 1948, 1887, 1734, 1670,
1592, 1490, 1449, 1371, 1261, 1215, 1160, 1022, 960, 906, 765, 690,
619, 578, 517. HRMS (ESI): Calcd for C24H23O6P [MþNa]þ: 461.1130;
found: 461.1066.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tet.2012.05.021.
4.4.2. (Z)-Methyl 4-(4-bromophenyl)-4-((diphenoxyphosphoryl)oxy)
but-3-enoate (6o). Colorless oil, 82% yield. 1H NMR (600 MHz,
CDCl3)
d
7.41 (d, J¼8.6 Hz, 2H), 7.35 (d, J¼8.6 Hz, 2H), 7.31 (t,
References and notes
J¼7.9 Hz, 4H), 7.19 (t, J¼7.4 Hz, 2H), 7.12 (d, J¼7.8 Hz, 4H),
5.92e5.94 (m, 1H), 3.66 (s, 3H), 3.39 (dd, J¼7.0, 2.8 Hz, 2H) ppm;
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d
171.1, 150.2 (d, J¼7.2 Hz), 146.7 (d,
J¼9.3 Hz), 133.1, 131.5, 129.8, 127.2, 125.6, 123.1, 119.9 (d, J¼4.8 Hz),
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ꢀ18.44 ppm. FTIR (KBr, cmꢀ1): 3370, 3070, 2953, 2836, 1738,
1689, 1671, 1591, 1591, 1489, 1456, 1438, 1397, 1260, 1213, 1160,
1098, 1073, 1026, 951, 818, 759, 689, 621, 503. MS (EI) m/z 503
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4.4.3. (Z)-Ethyl 4-((diphenoxyphosphoryl)oxy)-4-(4-nitrophenyl)
but-3-enoate (6p). Colorless oil, 54% yield. 1H NMR (400 MHz,
CDCl3)
d
8.14 (d, J¼8.8 Hz, 2H), 7.63 (d, J¼8.8 Hz, 2H), 7.33 (t,
J¼7.8 Hz, 4H), 7.21 (m, 3H), 7.15 (d, J¼7.7 Hz, 3H), 6.16e6.20 (m,
1H), 4.16 (m, 2H), 3.45 (dd, J¼6.9, 2.9 Hz, 2H), 1.25 (t, J¼7.1 Hz, 3H)
ppm; 13C NMR (100 MHz, CDCl3)
d
170.3, 150.1 (d, J¼7.3 Hz), 147.7,
145.6 (d, J¼9.0 Hz), 140.2, 129.9, 126.2, 125.8, 123.6, 119.9 (d,
J¼4.9 Hz), 114.2 (d, J¼6.5 Hz), 61.1, 31.8, 14.1 ppm; 31P NMR
(161 MHz, CDCl3)
d
ꢀ18.18 ppm. FTIR (KBr, cmꢀ1): 3454, 3073,
2984, 2939, 2907, 2453, 1944, 1872, 1736, 1666, 1595, 1521, 1489,

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