Highly efficient and selective olefination of acyl phosphonates with ethyl diazoacetate catalyzed by a cobalt(II) porphyrin complex

Article abstract of DOI:10.1016/j.tet.2008.05.108

The cobalt(II) porphyrin complex (CoTPP) was found to be an efficient catalyst for the Wittig type olefination of acyl phosphonates with ethyl diazoacetate (EDA) in the presence of triphenylphosphine (Ph₃P). By using this one pot methodology under mild conditions, densely functionalized vinyl phosphonates were obtained in high yields and high E/Z selectivities in relatively short reaction times. A?rather broad substrate spectrum and steric influence on the reaction rate were observed.

Full text of DOI:10.1016/j.tet.2008.05.108

Tetrahedron 64 (2008) 7555–7560
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Highly efficient and selective olefination of acyl phosphonates with ethyl
diazoacetate catalyzed by a cobalt(II) porphyrin complex
*
Erkan Ertu¨rk, Ayhan S. Demir
Department of Chemistry, Middle East Technical University, 06531 Ankara, Turkey
a r t i c l e i n f o
a b s t r a c t
Article history:
The cobalt(II) porphyrin complex (CoTPP) was found to be an efficient catalyst for the Wittig type ole-
fination of acyl phosphonates with ethyl diazoacetate (EDA) in the presence of triphenylphosphine
(Ph3P). By using this one pot methodology under mild conditions, densely functionalized vinyl phos-
phonates were obtained in high yields and high E/Z selectivities in relatively short reaction times.
A rather broad substrate spectrum and steric influence on the reaction rate were observed.
Ó 2008 Elsevier Ltd. All rights reserved.
Received 10 March 2008
Received in revised form 5 May 2008
Accepted 22 May 2008
Available online 28 May 2008
1. Introduction
Vinyl phosphonates constitute a very important class of organic
compounds.1 They have been used as monomers,2 polymer addi-
tives,3 flame retardants,4 precursors for drug synthesis,5 etc. Vinyl
phosphonates have also been subjected to a variety of further
transformations.6 Therefore, several methods for the preparation of
vinyl phosphonates have been reported in the literature where the
metalation of alkynes, hydrophosphynilation of alkynes, Arbusov
reactions of vinyl chlorides, Horner–Wadsworth–Emmons (HWE)
type olefination of simple alkyl phosphonates via metalation, and
radical trapping reactions were all employed.7 Wittig type olefi-
nation is one of the most frequently used methods for the con-
struction of carbon–carbon double bonds in organic synthesis.8,9
Phosphoranes that are the nucleophilic part of the Wittig reactions
were easily prepared by the Arbusov reaction or via the de-
composition of diazo compounds in the presence of a transition
metal complex.10,11 Very recently, iron and cobalt porphyrin com-
plexes were successfully utilized for the olefination of aldehydes
and for ketones with diazo compounds in the presence of triar-
ylphosphines, wherein metal porphyrins generate stable metal
carbene complexes.12 In conjunction with our ongoing program on
acyl phosphonate chemistry,13 we report here our successful results
on the cobalt(II) tetraphenylporphyrin (CoTPP) catalyzed olefina-
tion of acyl phosphonates with ethyl diazoacetate (EDA) in the
presence of triphenylphosphine (Ph3P) (Fig. 1). Although several
examples on the olefination of acyl phosphonates via a classical
stepwise Wittig reaction were shown by Zbiral and Harris in the
literature,7d,14 it has systematically not been investigated so far.
N
N
N
N
Co
CoTPP
Figure 1. Structure of the cobalt(II) porphyrin (CoTPP) complex.
2. Results and discussion
Although both air-stable CoTPP and the iron(III) tetraphe-
nylporphyrin chloride (FeTPPCl) were able to catalyze the olefina-
tion of aldehydes as well as ketones by decomposing the diazo
compounds in the presence of Ph3P,12e,f cost-effective CoTPP was
the catalyst of choice for our investigation for the acyl phosphonate
olefination (Eq. 1). Absolute toluene was used as the solvent be-
cause of its relative high boiling point and high solubility of CoTPP
in toluene. After the simple optimization of the catalyst loading and
the yield using benzoyl phosphonate (1a) as the test substrate,
4 mol % of CoTPP was found to be optimum. After stirring at 80 ꢀC
for 4 h (TLC) under the standard conditions (CoTPP [4 mol %], EDA
[1.20 equiv], Ph3P [1.20 equiv]), the corresponding olefin product
2a was obtained in 92% yield and high E/Z selectivity (97:3) (Table 1,
entry 1). Several substituted aroyl phosphonates (1b–g) were then
subjected to the olefination in order to determine the substrate
scope of this methodology (Table 1, entries 2–7). The vinyl phos-
phonates 2b–f were isolated in high yields (72–94%) and E/Z
* Corresponding author. Tel.: þ90 312 210 3242; fax: þ90 312 210 3200.
E-mail address: asdemir@metu.edu.tr (A.S. Demir).
0040-4020/$ – see front matter Ó 2008 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2008.05.108

7556
E. Ertu¨rk, A.S. Demir / Tetrahedron 64 (2008) 7555–7560
selectivities within 4 h at 80 ꢀC, in which the only exception was the
olefin product 2g bearing a 2-methyl substituted phenyl group.
Thus, the sterically hindered aroyl phosphonate 1g had to be heated
at 100 ꢀC for 24 h in order to give the vinyl phosphonate 2g in good
yield (72%) and under full-stereoselectivity (E/Z¼100/0, entry 7). The
alkoyl phosphonates 1h and 1i were the somewhat less reactive
substrates for the olefination. However, they could be converted to
the corresponding olefin products 2h and 2i in 89% and 72% yields
and after 6 h and 12 h, respectively (entries 8 and 9). Only
E-isomers of 2h and 2i were obtained. This result of a longer re-
action time for the olefination of the alkoyl phosphonate compared
to the aroyl phosphonate indicates that alkoyl phosphonates are
less reactive toward phosphoranes than aroyl phosphonates. Thus,
we attempted to olefinate the sterically hindered and less reactive
pivaloyl phosphonate (1j) under the standard reaction conditions
(entry 10). However, no conversion of 1j was detected. In spite of all
our attempts to convert 1j by modifying the reaction conditions
(e.g., refluxing the reaction mixture for 48 h in the presence of
Table 1
Olefination of acyl phosphonates (1) with EDA catalyzed by CoTPPa
Entry
Substrate
Product
Time (h)
Yieldb (%)
E/Zc
O
O
H
EtO
P(OMe)2
1
4
92
97/3
P(OMe)2
O
O
1a
2a
O
O
H
EtO
P(OMe)2
O
2
3
4
5
4
4
4
4
80
81
83
94
95/5
97/3
97/3
97/3
P(OMe)2
O
MeO
MeO
1b
2b
O
O
H
EtO
P(OMe)2
O
P(OMe)2
O
F
F
1c
2c
O
O
H
EtO
P(OMe)2
O
P(OMe)2
O
Cl
Cl
1d
2d
O
O
H
EtO
O
P(OMe)2
O
P(OMe)2
O
Me
Me
1e
2e
H
O
EtO
P(OMe)2
O
P(OMe)2
O
6
4
90
97/3
Me
Me
1f
2f
O
O
EtO
P(OMe)2
O
7
24d
72
100/0
P(OMe)2
O
Me
1g
Me
2g

E. Ertu¨rk, A.S. Demir / Tetrahedron 64 (2008) 7555–7560
7557
Table 1 (continued )
Entry
Substrate
Product
Time (h)
Yieldb (%)
E/Zc
O
O
EtO
P(OMe)2
8
9
6
89
100/0
100/0
P(OMe)2
O
O
1h
2h
O
O
O
EtO
P(OMe)2
O
1i
12
72
P(OMe)2
O
2i
P(OMe)2
10
d
48
d
d
O
1j
a
Reactions were carried out at 80 ꢀC in toluene under argon, using 1.00 equiv of acyl phosphonate, 1.20 equiv of EDA, 1.20 equiv of Ph3P, and 4.0 mol % of CoTPP.
b
c
Isolated yield.
Determined by 1H NMR.
Reaction was run at 100 ꢀC.
d
1.00 equiv of benzoic acid as the Brønsted acid catalyst),12e,f no
by phosphorane (5) formation and olefination as depicted in
conversion of 1j could be achieved. Then, the olefination of pivaloyl
phosphonate (1j) was attempted by employing trimethyl phosphite
((MeO)3P) and lithium bromide for the generation of less hindered
ylide compared to what is formed from Ph3P, as reported by
Aggarwal et al.12b (Scheme 1). Thus, we were able to minimize
sterical influences on the reaction. However, all experiments using
toluene or dioxane as the solvents at 80 ꢀC or at reflux temperature
for 48 h failed. While no conversion of 1j was observed, the sole
product isolated was the phosphonate 3, which demonstrated that
CoTPP is also able to transfer carbene to trimethyl phosphite
forming the desired ylide for further transformations (Scheme 1).
Scheme 2.
EtO2C
R
H
EtO2C
Ph3P
O
Ph3P
CoIITPP
EtO2C
N2
N2
P(OMe)2
O
O
H
Ph3P CHCO2Et
5
R
P(OMe)2
O
CoIIITPP
4
Scheme 2. Possible olefination mechanism catalyzed by CoTPP is in agreement with
what is proposed in the literature.12f
O
H
CoTPP
(cat.)
O
EtO
CO2Et
N2
EDA
ð1Þ
+
R
P(OMe)2
O
Ph3P
R
P(OMe)2
O
3. Conclusions
1
2
In conclusion, we have presented a very practical route to-
ward the synthesis of alkoxycarbonylmethylidene phosphonates
by reacting the acyl phosphonates with EDA in the presence of
Ph3P and a catalytic amount of commercially available CoTPP.
Easily accessible aroyl and alkoyl phosphonates could be olefi-
nated in very high yields, in excellent E/Z ratios, and in short
reaction times by using this one pot protocol under neutral and
mild conditions, which made this methodology very practical for
synthesis. Moreover, this methodology could also excellently
extend the application area of the metalloporphyrin catalyzed
olefination reactions for the synthesis of potentially useful un-
saturated trisubstituted systems bearing carboxylic- and phos-
phonic-ester functionalities. Further investigations on the use of
these trisubstituted vinyl phosphonates are in progress at our
laboratory.
E/Z ratios of the olefin products (2a–i) were determined
by means of 1H NMR by proportioning the integration areas of the
E- and Z-olefin protons to each other. The E-configuration for the
major products was assigned because of the vicinal cis H,P coupling
(3JH–P¼24.0 Hz).7d,14 The vicinal trans H,P coupling has a value of
44.0 Hz (3JH–P). Due to hindered rotation about the C(aryl)–C(olefin)
bond, the molecule 2g has axial chirality, which in turn causes the
two OMe groups of the phosphoryl moiety to be diastereotopic. The
CH2 protons of the ethoxy group are also diastereotopic, but they
may be too far from the chiral axis to cause different chemical shifts
in the NMR spectra. The possible reaction mechanism can be
derived from what is proposed for the metalloporphyrin catalyzed
olefination of aldehydes and ketones,12 which includes the radical
metallocarbene (4) formation from CoTPP and EDA followed
O
O
O
EDA (1.5 eq), (MeO)3P (1.2 eq), LiBr (1.0 eq)
(MeO)2P
P(OMe)2
O
OEt
3 (ca. 35% y)
CoTPP (4 mol%), Toluene or Dioxane, 80 °C, 48 h
1j
no conversion of 1j detected
Scheme 1. Search for the olefination of 1j as the sterically hindered acyl phosphonate.

7558
E. Ertu¨rk, A.S. Demir / Tetrahedron 64 (2008) 7555–7560
4. Experimental
3JC–P¼29.0 Hz, EtO(O)C). 31P NMR (161 MHz, CDCl3):
¼17.0. EA:
d
Anal. Calcd for C13H17O5P: C, 54.93; H, 6.03. Found: C, 54.89; H, 6.29.
4.1. General
Several well resolved NMR signals for the minor diastereomer (Z-
2a) could also be obtained and assigned as follows: 1H NMR
3
All reactions were carried out in oven-dried Schlenk tubes with
magnetic stirring under a positive pressure of argon. Toluene and
dioxane were freshly distilled from sodium/benzophenone prior to
use under an argon atmosphere. Ethyl diazoacetate (EDA) and tri-
phenylphosphine (Ph3P) were purchased from Aldrich and used
as-received. Cobalt(II) tetraphenylporphyrin complex (CoTPP) was
synthesized from the reaction of tetraphenylporphyrin (TPPH2)
with excessive anhydrous cobalt(II) chloride in the presence of 2,6-
lutidine (2.00 equiv) in boiling dimethylformamide (DMF) and it
was purified by recrystallization from dichloromethane (DCM)/
acetonitrile (MeCN) mixture.15 Acyl phosphonates were prepared
according to the literature procedures and purified by vacuum
distillation.16 Thin layer chromatography (TLC) was conducted on
aluminum sheets that were pre-coated with silica gel SIL G/UV254
from MN GmbH & Co., in which the spots were visualized in UV
(400 MHz, CDCl3):
d
¼1.29 (t, JH–H¼8.0 Hz, 3H, CH3CH2), 4.25 (q,
3JH–H¼8.0 Hz, 2H, CH3CH2), 6.55 (d, 3JH–P¼44.0 Hz, 1H, CHolefin). 31
P
NMR (161 MHz, CDCl3):
d
¼15.3.
4.1.2. Ethyl (E)-3-(dimethoxyphosphinyl)-3-(4-methoxyphenyl)-2-
propenoate (E-2b)
After stirring the reaction mixture at 80 ꢀC for 4 h under argon,
the olefin product 2b was obtained as a light yellow oil (250 mg,
0.80 mmol, 80%) via column chromatographic purification. Rf¼0.41
(silica gel, DCM/EtOAc 1:1). FTIR (film): nmax (cmꢁ1)¼2957 (w),
1728 (s), 1606 (s), 1511 (s), 1462 (m), 1369 (w), 1291 (s), 1251 (s),
1205 (s), 1179 (s), 1029 (s), 836 (s), 773 (m), 571 (m), 531 (m). 1H
NMR (400 MHz, CDCl3):
d
¼1.12 (t, 3JH–H¼8.0 Hz, 3H, CH3CH2), 3.74 (d,
3
3JH–P¼8.0 Hz, 6H, P(O)(OCH3)2), 3.82 (s, 3H, OCH3), 4.08 (q, JH–H
¼
3
8.0 Hz, 2H, CH3CH2), 6.86 (d, JH–P¼24.0 Hz, 1H, CHolefin), 6.89 (d,
3
light (
l
¼254 nm) and/or by staining with ninhydrin. Chromato-
3JH–H¼10.0 Hz, 2H, meta-Haryl), 7.24 (d, JH–H¼10.0 Hz, 2H, ortho-
graphic separations were performed using silica gel (MN-silica gel
H
aryl). 13C NMR (100 MHz, CDCl3):
d
¼13.8 (q, CH3CH2), {53.11, 53.17}
60, 230–400 mesh). 1H and 13C NMR spectra were recorded on
(q, JC–P¼6.0 Hz, P(O)(OCH3)2), 51.2 (q, OCH3), 60.8 (t, CH3CH2),
2
2
a Bruker DPX400 NMR spectrometer. Chemical shifts
in parts per million (ppm) relative to the residual protons in the
NMR solvent (CHCl3: 7.24) and carbon resonance of the solvent
(CDCl3: 77.0). NMR peak multiplicities were given as follows:
d
are reported
113.6 (d, meta-Caryl), {125.80, 125.87} (s, JC–P¼7.0 Hz, Caryl),
3
{129.55, 129.61} (d, JC–P¼6.0 Hz, ortho-Caryl), {132.56, 132.67} (d,
1
d
2JC–P¼11.0 Hz, CHolefin), {141.88, 143.66} (s, JC–P¼173.0 Hz, Colefin),
3
d
159.8 (s, MeO–Caryl), {164.53, 164.82} (s, JC–P¼29.0 Hz, EtO(O)C).
s¼singlet, d¼doublet, t¼triplet, q¼quartet, m¼multiplet, br¼
broad. 13C atoms were assigned by means of DEPT-135 experiments.
The IR measurements were performed on a Varian 1000 FTIR
spectrometer. High resolution CI mass spectra were recorded on
a Finnigan MAT. Elemental analyses (EA) were performed using
a LECO, CHNS-932 instrument.
31P NMR (161 MHz, CDCl3):
d¼17.0. EA: Anal. Calcd for C13H17O5P:
C, 53.50; H, 6.09. Found: C, 53.73; H, 6.21. Several well resolved
NMR signals for the minor diastereomer (Z-2b) could also be
obtained and assigned as follows: 1H NMR (400 MHz, CDCl3):
3
3
d
¼1.38 (t, JH–H¼8.0 Hz, 3H, CH3CH2), 4.33 (q, JH–H¼8.0 Hz, 2H,
CH3CH2), 6.61 (d, JH–P¼44.0 Hz, 1H, CHolefin). 31P NMR (161 MHz,
3
CDCl3):
d
¼15.3.
4.1.1. Ethyl (E)-3-(dimethoxyphosphinyl)-3-phenyl-2-propenoate
(E-2a) (representative procedure)
4.1.3. Ethyl (E)-3-(dimethoxyphosphinyl)-3-(4-fluorophenyl)-2-
propenoate (E-2c)
CoTPP (40.0 mmol, 4 mol %) and Ph3P (1.2 mmol, 1.20 equiv)
were placed in an oven-dried Schlenk tube and then the tube was
capped with a glass stopper. The tube was evacuated for 15 min and
back-filled with argon. The glass stopper was replaced with a rub-
ber septum under positive pressure of argon. After addition of ab-
solute toluene (2 mL) as the solvent, dimethyl benzoyl phosphonate
(1.0 mmol, 1.00 equiv) was added in one portion succeeded by the
addition of EDA (1.2 mmol, 1.20 equiv) in one portion at room
temperature. After stirring the homogenous mixture at room
temperature for several minutes, the mixture was stirred at 80 ꢀC
(oil-bath temperature) under argon. The reaction progress was
monitored by TLC. Upon completion of the reaction (80 ꢀC, 4 h, as
indicated in Table 1), the mixture was cooled to room temperature
and evaporated. By the addition of diethyl ether (ca. 10–15 mL),
triphenylphosphine oxide was precipitated and it was removed
from the reaction mixture by decanting the solution phase. After
removing all volatile components of the solution by rotary evapo-
ration, the olefin product 2a was obtained as a light yellow oil
(260 mg, 0.92 mmol, 92% yield) after column chromatography on
silica gel. Rf¼0.47 (silica gel, DCM/EtOAc 1:1). FTIR (film): nmax
(cmꢁ1)¼3068 (w), 2984 (m), 2957 (m), 2853 (w), 1729 (s), 1446 (m),
After stirring the reaction mixture at 80 ꢀC for 4 h under argon,
the olefin product 2c was obtained as a light yellow oil (245 mg,
0.81 mmol, 81%) via column chromatographic purification. Rf¼0.44
(silica gel, DCM/EtOAc 1:1). FTIR (film): nmax (cmꢁ1)¼2985 (w),
2958 (m), 1728 (s), 1600 (m), 1508 (s), 1464 (m), 1369 (w), 1256 (s),
1222 (s), 1205 (s), 1027 (s), 837 (s), 774 (m), 569 (m), 509 (m). 1H
NMR (400 MHz, CDCl3):
d
¼1.10 (t, 3JH–H¼8.0 Hz, 3H, CH3CH2), 3.75
3
3
(d, JH–P¼12.0 Hz, 6H, P(O)(OCH3)2), 4.07 (q, JH–H¼8.0 Hz, 2H,
3
CH3CH2), 6.88 (d, JH–P¼24.0 Hz, 1H, CHolefin), 7.06 (t, J¼8.0 Hz, 2H,
meta-Haryl), 7.24–7.28 (m, 2H, ortho-Haryl). 13C NMR (100 MHz,
2
CDCl3):
d
¼13.8 (q, CH3CH2), {53.19, 53.25} (q, JC–P¼6.0 Hz,
P(O)(OCH3)2), 60.9 (t, CH3CH2), {115.07, 115.08, 115.28, 115.29} (d,
4JC–P¼4.0 Hz, JC–F¼21.0 Hz, meta-Caryl), {129.63, 129.67, 129.70,
2
129.74} (s, 4JC–F¼4.0 Hz, 2JC–P¼7.0 Hz, Caryl), {129.95, 130.01, 130.04,
130.09} (d, 3JC–P¼6.0 Hz, 3JC–F¼9.0 Hz, ortho-Caryl), {133.35, 133.46}
(d, 2JC–P¼11.0 Hz, CHolefin), {141.50,143.24} (s, 1JC–P¼174.0 Hz, Colefin),
5
1
{161.55, 161.58, 164.02, 164.05} (s, JC–P¼3.0 Hz, JC–F¼247.0 Hz,
F–Caryl), {164.14, 164.42} (s, JC–P¼28.0 Hz, EtO(O)C). 31P NMR
3
(161 MHz, CDCl3):
d¼16.8. EA: Anal. Calcd for C13H16FO5P: C, 51.66;
H, 5.34. Found: C, 51.72; H, 5.62. Several well resolved NMR signals
1369 (m), 1255 (s), 1205 (s),1027 (s), 832 (m), 781 (m), 700 (m), 577
for the minor diastereomer (Z-2c) could also be obtained and
3
3
(m), 542 (m). 1H NMR (400 MHz, CDCl3):
d
¼0.96 (t, JH–H¼8.0 Hz,
assigned as follows: 1H NMR (400 MHz, CDCl3):
d
¼1.37 (t, JH–H
¼
3H, CH3CH2), 3.65 (d, 3JH–P¼12.0 Hz, 6H, P(O)(OCH3)2), 3.95 (q, 3JH–H
¼
8.0 Hz, 3H, CH3CH2), 4.33 (q, JH–H¼8.0 Hz, 2H, CH3CH2), 6.61 (d,
3
3
8.0 Hz, 2H, CH3CH2), 6.81 (d, JH–P¼24.0 Hz, 1H, CHolefin), 7.19–7.22
3JH–P¼44.0 Hz, 1H, CHolefin). 31P NMR (161 MHz, CDCl3):
¼15.1.
d
(m, 2H, Haryl), 7.22–7.35 (m, 3H, Haryl). 13C NMR (100 MHz, CDCl3):
2
d
¼13.6 (q, CH3CH2), {53.06, 53.12} (q, JC–P¼6.0 Hz, P(O)(OCH3)2),
4.1.4. Ethyl (E)-3-(dimethoxyphosphinyl)-3-(4-chlorophenyl)-2-
propenoate (E-2d)
After stirring the reaction mixture at 80 ꢀC for 4 h under argon,
the olefin product 2d was obtained as a light yellow oil (265 mg,
0.83 mmol, 83%) via column chromatographic purification. Rf¼0.47
60.7 (t, CH3CH2), 127.89 (d, meta-Caryl), 127.94 (d, para-Caryl),
3
{128.26, 128.28} (d, JC–P¼2.0 Hz, ortho-Caryl), {133.12, 133.23}
2
2
(d, JC–P¼11.0 Hz, CHolefin), {133.81, 133.88} (s, JC–P¼7.0 Hz,
Caryl), {142.23, 143.96} (s, 1JC–P¼173.0 Hz, Colefin), {164.19,164. 48} (s,

E. Ertu¨rk, A.S. Demir / Tetrahedron 64 (2008) 7555–7560
7559
(silica gel, DCM/EtOAc 1:1). FTIR (film): nmax (cmꢁ1)¼2985 (w),
CDCl3):
d
¼17.2. EA: Anal. Calcd for C14H19O5P: C, 56.37; H, 6.42.
2957 (m), 1729 (s), 1489 (m), 1463 (w), 1369 (w), 1258 (s), 1207 (s),
Found: C, 56.65; H, 6.58. Several well resolved NMR signals for the
1092 (m), 1028 (s), 837 (m), 775 (m), 710 (w), 565 (m). 1H NMR
minor diastereomer (Z-2f) could also be obtained and assigned as
3
3
(400 MHz, CDCl3):
d
¼1.11 (t, JH–H¼8.0 Hz, 3H, CH3CH2), 3.75 (d,
follows: 1H NMR (400 MHz, CDCl3):
d
¼1.37 (t, JH–H¼8.0 Hz, 3H,
3JH–P¼12.0 Hz, 6H, P(O)(OCH3)2), 4.07 (q, JH–H¼8.0 Hz, 2H,
CH3CH2), 4.33 (q, 3JH–H¼8.0 Hz, 2H, CH3CH2), 6.62 (d, 3JH–P¼44.0 Hz,
3
CH3CH2), 6.89 (d, 3JH–P¼24.0 Hz,1H, CHolefin), 7.22 (dd, 4JH–P¼2.0 Hz,
1H, H2). 31P NMR (161 MHz, CDCl3):
d¼15.5.
3JH–H¼8.0 Hz, 2H, ortho-Haryl), 7.35 (d, JH–H¼8.0 Hz, 2H, meta-
3
H
aryl). 13C NMR (100 MHz, CDCl3):
d
¼13.8 (q, CH3CH2), {53.23,
4.1.7. Ethyl (E)-3-(dimethoxyphosphinyl)-3-(2-methylphenyl)-2-
propenoate (E-2g)
2
53.29} (q, JC–P¼6.0 Hz, P(O)(OCH3)2), 70.0 (t, CH3CH2), {128.34,
4
3
128.35} (d, JC–P¼1.0 Hz, meta-Caryl), {129.47, 129.52} (d, JC–P
¼
After stirring the reaction mixture at 100 ꢀC for 24 h under ar-
gon, the olefin product 2g was obtained as a light yellow oil
(215 mg, 0.72 mmol, 72%) via column chromatography purification.
Rf¼0.50 (silica gel, DCM/EtOAc 1:1). FTIR (film): nmax (cmꢁ1)¼2984
(w), 2957 (m), 1731 (s), 1627 (w), 1459 (w), 1255 (s), 1199 (s), 1028
(s), 832 (m), 756 (w), 726 (w), 562 (m). 1H NMR (400 MHz, CDCl3):
2
5.0 Hz, ortho-Caryl), {132.28, 132.35} (s, JC–P¼70 Hz, Caryl), {133.42,
2
133.53} (d, JC–P¼11.0 Hz, CHolefin), 134.6 (s, para-Caryl), {141.54,
143.28} (s, 1JC–P¼174.0 Hz, Colefin), {164.01, 164.29} (s, 3JC–P¼28.0 Hz,
EtO(O)C). 31P NMR (161 MHz, CDCl3):
d
¼16.5. EA: Anal. Calcd for
C
13H16ClO5P: C, 48.99; H, 5.06. Found: C, 49.22; H, 5.34. Several well
resolved NMR signals for the minor diastereomer (Z-2d) could also
d
¼0.94 (t, 3JH–H¼8.0 Hz, 3H, CH3CH2), 2.17 (s, 3H, H3C–Caryl), 3.63 (d,
be obtained and assigned as follows: 1H NMR (400 MHz, CDCl3):
3JH–P¼8.0 Hz, 3H, P(O)(OCH3)), 3.66 (d, JH–P¼8.0 Hz, 3H,
3
3
3
3
3
d
¼1.37 (t, JH–H¼8.0 Hz, 3H, CH3CH2), 4.34 (q, JH–H¼8.0 Hz, 2H,
P(O)(OCH3)), 3.92 (q, JH–H¼8.0 Hz, 2H, CH3CH2), 6.83 (d, JH–P¼
CH3CH2), 6.63 (d, JH–P¼44.0 Hz, 1H, CHolefin). 31P NMR (161 MHz,
24.0 Hz, 1H, CHolefin), 6.97 (d, J¼8.0 Hz, 1H, meta-Haryl), 7.08–7.17
3
CDCl3):
d
¼15.9.
(m, 3H, Haryl). 13C NMR (100 MHz, CDCl3):
d
¼13.6 (q, CH3CH2), 19.6
2
(q, H3C–Caryl), {53.20, 53.26} (q, JC–P¼6.0 Hz, P(O)(OCH3)), {53.35,
2
4.1.5. Ethyl (E)-3-(dimethoxyphosphinyl)-3-(4-methylphenyl)-2-
propenoate (E-2e)
53.42} (q, JC–P¼7.0 Hz, P(O)(OCH3)), 60.7 (t, CH3CH2), {125.25,
4
3
125.27} (d, JC–P¼2.0 Hz, meta-Caryl), {127.58, 127.63} (d, JC–P
¼
4
After stirring the reaction mixture at 80 ꢀC for 4 h under argon,
the olefin product 2e was obtained as a light yellow oil (280 mg,
0.94 mmol, 94%) via column chromatographic purification. Rf¼0.57
(silica gel, DCM/EtOAc 1:1). FTIR (film): nmax (cmꢁ1)¼2984 (w),
2956 (m), 1730 (s), 1510 (w), 1460 (w), 1256 (s), 1202 (s), 1027 (s),
833 (m), 773 (w), 570 (m), 510 (w). 1H NMR (400 MHz, CDCl3):
5.0 Hz, ortho-Caryl), {128.07, 128.09} (d, JC–P¼2.0 Hz, meta-Caryl),
7
{129.75, 129.77} (d, JC–P¼2.0 Hz, para-Caryl), {133.05, 133.16} (d,
2JC–P¼11.0 Hz, CHolefin), {133.27, 133.32} (s, 3JC–P¼5.0 Hz, H3C–Caryl),
2
{135.82, 135.88} (s, JC–P¼6.0 Hz, Caryl), {143.17, 144.90} (s,
1JC–P¼173.0 Hz, Colefin), {163.81, 164.10} (s, 3JC–P¼29.0 Hz, EtO(O)C).
31P NMR (161 MHz, CDCl3):
d
¼15.9. EA: Anal. Calcd for C14H19O5P:
d
¼1.10 (t, 3JH–H¼8.0 Hz, 3H, CH3CH2), 2.36 (s, 3H, H3C–Caryl), 3.74 (d,
C, 56.37; H, 6.42. Found: C, 56.65; H, 6.58.
3
3JH–P¼12.0 Hz, 6H, P(O)(OCH3)2), 4.07 (q, JH–H¼8.0 Hz, 2H,
3
CH3CH2), 6.88 (d, JH–P¼24.0 Hz, 1H, CHolefin), 7.17 (br s, 4H, Haryl).
4.1.8. Ethyl (E)-3-(dimethoxyphosphinyl)-2-pentenoate (E-2h)
After stirring the reaction mixture at 80 ꢀC for 6 h under argon,
the olefin product 2h was obtained as a light yellow oil (210 mg,
0.89 mmol, 89%) via column chromatographic purification. Rf¼0.44
(silica gel, EtOAc 100%). FTIR (film): nmax (cmꢁ1)¼2982 (m), 2957
(m), 1723 (s), 1630 (w), 1462 (m), 1371 (w), 1255 (s), 1196 (s), 1029
13C NMR (100 MHz, CDCl3):
d¼13.8 (q, CH3CH2), 21.3 (q, H3C–Caryl),
2
{53.12, 53.18} (q, JC–P¼6.0 Hz, P(O)(OCH3)2), 60.8 (t, CH3CH2),
3
{127.80, 127.85} (d, JC–P¼5.0 Hz, ortho-Caryl), 128.8 (d, meta-Caryl),
2
2
{130.68, 130.75} (s, JC–P¼7.0 Hz, Caryl), {132.87, 132.99} (d, JC–P
¼
5
12.0 Hz, CHolefin), {138.30, 138.33} (s, JC–P¼3.0 Hz, H3C–Caryl),
{142.45,144.17} (s, 1JC–P¼172.0 Hz, Colefin), {164.33,164.61} (s, 3JC–P
¼
(s), 831 (m), 782 (m). 1H NMR (400 MHz, CDCl3):
d
¼1.09 (t, 3JH–H
¼
28.0 Hz, EtO(O)C). 31P NMR (161 MHz, CDCl3):
d
¼17.4. EA: Anal.
6.0 Hz, 3H, CH3CH2Colefin), 1.24 (t, JH–H¼6.0 Hz, 3H, CH3CH2O),
3
3
Calcd for C14H19O5P: C, 56.37; H, 6.42. Found: C, 56.65; H, 6.58.
2.58–2.67 (m, 2H, CH3CH2Colefin), 3.70 (d, JH–P¼12.0 Hz, 6H,
3
3
Several well resolved NMR signals for the minor diastereomer (Z-
P(O)(OCH3)2), 4.15 (q, JH–H¼8.0 Hz, 2H, CH3CH2O), 6.53 (d, JH–P¼
2e) could also be obtained and assigned as follows: 1H NMR
24.0 Hz, 1H, CHolefin). 13C NMR (100 MHz, CDCl3):
d
¼{13.43, 13.44}
3
(400 MHz, CDCl3):
d
¼1.38 (t, JH–H¼8.0 Hz, 3H, CH3CH2), 4.34 (q,
(q, 3JC–P¼1.0 Hz, CH3CH2Colefin), 14.0 (q, CH3CH2O), {21.94, 22.01} (t,
3JH–H¼8.0 Hz, 2H, CH3CH2), 6.63 (d, 3JH–P¼44.0 Hz, 1H, CHolefin). 31
P
2JC–P¼7.0 Hz, CH3CH2Colefin), {52.57, 52.62} (q, JC–P¼5.0 Hz,
2
NMR (161 MHz, CDCl3):
d
¼15.8.
P(O)(OCH3)2), 60.5 (t, CH3CH2O), {130.81, 130.93} (d, 2JC–P¼12.0 Hz,
CHolefin), {147.35, 149.01} (s, 1JC–P¼166.0 Hz, Colefin), {164.19, 164.51}
3
4.1.6. Ethyl (E)-3-(dimethoxyphosphinyl)-3-(3-methylphenyl)-2-
propenoate (E-2f)
(s, JC–P¼32.0 Hz, EtO(O)C). 31P NMR (161 MHz, CDCl3):
d
¼20.6.
HRMS (ApCIþ): Calcd for [C9H18O5P] ([MþH]þ): 237.0892, found:
After stirring the reaction mixture at 80 ꢀC for 4 h under argon,
the olefin product 2f was obtained as a light yellow oil (268 mg,
0.90 mmol, 90%) via column chromatographic purification. Rf¼0.44
(silica gel, DCM/EtOAc 1:1). FTIR (film): nmax (cmꢁ1)¼2984 (m),
2966 (m), 1729 (s), 1603 (w), 1461 (m), 1369 (m), 1254 (s), 1188 (s),
237.0890.
4.1.9. Ethyl (E)-3-(dimethoxyphosphinyl)-4-methyl-2-
pentenoate (E-2i)
After stirring the reaction mixture at 80 ꢀC for 12 h under argon,
the olefin product 2i was obtained as a light yellow oil (180 mg,
0.72 mmol, 72%) via column chromatographic purification. Rf¼0.48
(silica gel, EtOAc 100%). FTIR (film): nmax (cmꢁ1)¼2956 (m), 1724 (s),
1027 (s), 833 (m), 775 (m), 705 (m), 625 (w), 588 (w), 547 (m), 520
3
(w). 1H NMR (400 MHz, CDCl3):
d
¼1.06 (t, JH–H¼8.0 Hz, 3H,
3
CH3CH2), 2.36 (s, 3H, H3C–Caryl), 3.74 (d, JH–P¼12.0 Hz, 6H,
3
3
P(O)(OCH3)2), 4.05 (q, JH–H¼8.0 Hz, 2H, CH3CH2), 6.87 (d, JH–P
¼
1465 (w),1369 (w),1254 (s),1204 (s),1028 (s), 829 (m), 775 (w), 579
24.0 Hz, 1H, Holefin), 7.05–7.28 (m, 4H, Haryl). 13C NMR (100 MHz,
(w). 1H NMR (400 MHz, CDCl3):
d
¼1.14 (d, JH–H¼8.0 Hz, 6H,
3
3
CDCl3):
d
¼13.7 (q, CH3CH2), 21.4 (q, H3C–Caryl), {53.15, 53.21} (q,
CH(CH3)2), 1.24 (t, JH–H¼6.0 Hz, 3H, CH3CH2), 3.53–3.65 (m, 1H,
2JC–P¼6.0 Hz, P(O)(OCH3)2), 60.8 (t, CH3CH2), {124.95, 125.01} (d,
CH(CH3)3), 3.69 (d, JH–P¼8.0 Hz, 6H, P(O)(OCH3)2), 4.15 (q, JH–H¼
3
3
3
3JC–P¼6.0 Hz, ortho-Caryl), {127.91, 127.92} (d, JC–P¼1.0 Hz, para-
8.0 Hz, 2H, CH3CH2), 6.52 (d, JH–P¼24.0 Hz, 1H, CHolefin). 13C NMR
5
Caryl), {128.37, 128.42} (d, 3JC–P¼5.0 Hz, ortho-Caryl), {129.17, 129.19}
(100 MHz, CDCl3):
d
¼14.0 (q, CH3CH2), {21.05, 21.08} (q, JC–P
¼
3
4
2
2
(d, JC–P¼2.0 Hz, meta-Caryl), {133.08, 133.19} (d, JC–P¼11.0 Hz,
3.0 Hz, CH(CH3)2), {28.83, 28.91} (d, JC–P¼8.0 Hz, CH(CH3)2),
2
2
CHolefin), {133.65, 133.72} (s, JC–P¼7.0 Hz, Caryl), {137.61, 137.62} (s,
{52.38, 52.44} (q, JC–P¼6.0 Hz, P(O)(OCH3)2), 60.7 (t, CH3CH2),
4JC–P¼1.0 Hz, H3C–Caryl), {142.30, 144.02} (s, 1JC–P¼172.0 Hz, Colefin),
{131.03, 131.14} (d, 2JC–P¼11.0 Hz, CHolefin), {150.17, 151.78} (s, 1JC–P
¼
{164.34, 164.63} (s, JC–P¼29.0 Hz, EtO(O)C). 31P NMR (161 MHz,
161.0 Hz, Colefin), {164.64, 164.95} (s, JC–P¼31.0 Hz, EtO(O)C). 31P
3
3

7560
E. Ertu¨rk, A.S. Demir / Tetrahedron 64 (2008) 7555–7560
¼20.4. HRMS (ApCIþ): calcd for
Synthesis 1997, 653–656; (g) Jiao, X.-Y.; Bentrude, W. G. J. Am. Chem. Soc. 1999,
NMR (161 MHz, CDCl3):
d
121, 6088–6089; (h) Brunner, H.; Le Cousturier, N.; Pierre, J. Synlett 2000, 201–
204; (i) Zhao, C.-Q.; Han, L.-B.; Goto, M.; Tanaka, M. Angew. Chem., Int. Ed. 2001,
40, 1929–1932; (j) Ben-Valid, S.; Quntar, A. A. A.; Srebnik, M. J. Org. Chem. 2005,
70, 3554–3559; (k) Noshi, M. N.; El-awa, A.; Torres, E.; Fuchs, P. L. J. Am. Chem.
Soc. 2007, 129, 11242–11247; (l) Han, L.-B.; Ono, Y.; Shimada, S. J. Am. Chem. Soc.
2008, 139, 2752–2753.
[C10H20O5P] ([MþH]þ): 251.1048, found: 251.1045.
Acknowledgements
8. For recent reviews on the Wittig reaction, see: (a) Maryanoff, B. E.; Reitz, A. B.
Chem. Rev. 1989, 89, 863–927; (b) Padwa, A.; Hornbuckle, S. F. Chem. Rev. 1991,
91, 263–309; (c) Cristau, H.-J. Chem. Rev. 1994, 94, 1299–1313.
9. For recent reviews on the asymmetric Wittig type reactions, see: (a) Rein, T.;
Reiser, O. Acta Chem. Scand. 1996, 50, 369–379; (b) Li, A.-H.; Dai, L.-X.; Aggarwal,
V. K. Chem. Rev. 1997, 97, 2341–2372; (c) Rein, T.; Pederson, T. M. Synthesis 2002,
579–594.
This work was supported by the Scientific and Technological
¨
Research Council of Turkey (TUBITAK), the Turkish Academy of
¨
Science (TUBA), the Turkish State Planning Organization, and the
Middle East Technical University (METU). In particular, E.E. thanks
TUBITAK for a postdoctoral fellowship.
¨
10. For recent reviews on the use of diazo compounds for the Wittig type reactions,
see: (a) Ye, T.; McKervey, M. A. Chem. Rev. 1994, 94, 1091–1160; (b) Doyle, M. P.;
Forbes, D. C. Chem. Rev. 1998, 98, 911–936.
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