Reaction of diethyl thiocyanatomethylphosphonate with aldehydes as a route to diethyl Z-1-alkenylphosphonates

Article abstract of DOI:10.1002/hc.20371

Diastereoselective synthesis of diethyl Z-1-alkenylphosphonates from easily available diethyl thiocyanatomethylphosphonate and aromatic aldehydes has been developed. Olefination of the aldehydes occurs under mild conditions and affords the title compounds with moderate yields. A plausible mechanism of the above-mentioned reaction is also discussed.

Full text of DOI:10.1002/hc.20371

Heteroatom Chemistry
Volume 18, Number 7, 2007
R
eaction of Diethyl
Thiocyanatomethylphosphonate
with Aldehydes as a Route to Diethyl
Z-1-Alkenylphosphonates
Roman Blꢀ aszczyk and Tadeusz Gajda
Institute of Organic Chemistry, Department of Chemistry, Technical University of Lodz,
Zeromskiego St. 116, 90-924 Lodz, Poland
Received 18 September 2006; revised 3 December 2006
cyanatoacetic acid esters with aromatic aldehy-
ABSTRACT: Diastereoselective synthesis of diethyl
des as a route to 2-imino-1,3-oxathiolanes, we fo-
cused our attention on the reactions of diethyl
thiocyanatomethylphosphonate 1 with aldehydes
Z-1-alkenylphosphonates from easily available diethyl
thiocyanatomethylphosphonate and aromatic aldehy-
des has been developed. Olefination of the aldehydes
occurs under mild conditions and affords the title
compounds with moderate yields. A plausible mech-
anism of the above-mentioned reaction is also dis-
cussed. ꢀC 2007 Wiley Periodicals, Inc. Heteroatom Chem
2
, which could lead to new derivatives of 2-
imino-[1,3]-oxathiolan-4-yl)phosphonates 3 and/or
-hydroxy-1-mercaptophosphonates 4 (Scheme 1).
2
However, the above-mentioned reactions afforded
α,β-unsaturated phosphonates instead of the desired
products 3 and 4. This observation prompted us
to direct our investigations toward the synthesis of
alkenylphosphonates.
1
8:732–739, 2007; Published online in Wiley InterScience
(
www.interscience.wiley.com). DOI 10.1002/hc.20371
Alkenylphosphonates are important intermedi-
ates in organic chemistry [5], especially for the
synthesis of carbo- and heterocyclic compounds
INTRODUCTION
Organic thiocyanates are valuable tools for the
synthesis of a wide variety of organosulfur com-
pounds [1]. Increasing interest in the chem-
istry of bifunctional organic compounds contain-
ing both phosphorus and sulfur moieties resulted
in the efficient synthesis of racemic [2] as well
as optically active 1-(thiocyanato)alkylphosphonates
[5a,6] as well as various functionalized phospho-
nates [5a,7].
Although
a
number
of
methodologies
have been developed for the synthesis of E-1-
alkenylphosphonates [8], there is still a place for
the new protocols directed to the preparation of Z-
alkenylphosphonates [5a]. So far, these compounds
are available by Horner–Wadsworth–Emmons
[3], their application in the preparation of the
α-sulfanylphosphonates [3], potential metalloen-
zyme inhibitors.
Being inspired by the work of Hayashi
et al. [4] who found the condensation of thio-
(HWE) olefination of aldehydes with tetrakis(2,2,2-
trifluoroethyl)methylenebisphosphonate [9], palla-
dium-catalyzed coupling of dialkyl phosphites with
Z-1-bromo-1-alkenes [10], and copper-promoted
substitution of vinyl bromides with dialkyl
and diphenyl phosphites in the presence of
base [11]. Other convenient methodologies are
Correspondence to: Tadeusz Gajda; e-mail: tmgajda@p.lodz.pl.
ꢀ
c 2007 Wiley Periodicals, Inc.
732

Reaction of Diethyl Thiocyanatomethylphosphonate with Aldehydes 733
TABLE 1 Diethyl 1-Alkenylphosphonates (5/6a–g) Prepared
Entry Products 5/6
R
5/6 Z/Ea Yield b (%)
1
2
3
4
5
6
7
8
9
a
a
a
b
c
d
e
f
Ph
Ph
Ph
98/2
60 (55)
75 (60)
–
c
65/35
d
–
2-MeOC H
2-MeC H
91/9
97/3
5/95
91/9
72/28
84/16
40 (21)
51 (32)
6
4
SCHEME 1 Expected route to 2-imino-[1,3]-oxathiolan-4-
yl)phosphonates 3 and 2-hydroxy-1-mercaptophosphonates
6
4
e
4-O NC H
33 (22)
45 (26)
50 (31)
65 (41)
2
6
4
4
.
1-Naphthyl
2-Furyl
(E)-PhCH CH
g
aDiastereomers ratios measured by 1H and 31P NMR of the crude
reaction mixture.
based on catalytic reduction of the 1-alkynyl-
7h,12] and 1,2-dienylphosphonates [13] and
addition of “zirconocene” [14] or lithium
organocuprates and Grignard reagents [12a] to
[
b
Yields of pure, isolated diastereomers 5/6. Yields in parentheses
refer to single Z-5a-c,e-g separated after flash chromatography.
c
d
e
◦
2
2
Equivalents of t-BuOK, at −70 C for 2 h was applied.
◦
Equivalents of LDA, at −70 C for 10 min was applied.
1
-alkynylphosphonates. Also nucleophilic addi-
tions of organometallic reagents to diethyl 1-
trimethylsilyl)vinylphosphonate [15] and Peterson
Yield of pure E-6d.
(
olefination of acetaldehyde with dialkyl (trimethyl-
silyl)methylphosphonates [16] seem to be useful for
the preparation of Z-alkenylphosphonates. Other
attractive methods involve stereospecific palladium
acetate-catalyzed reaction of Z-alkenylboronates
with triethyl phosphite [17], acid cleavage of
Table 1. Diastereoselectivity of the olefination was
1
31
determined by means of H and P NMR spectra of
crude reaction mixtures. The detailed stereochemi-
cal analysis will be discussed further.
The results summarized in Table 1 show that
the application of 2.2 equivalents of sodium hy-
E-α-triphenylstannylvinylphosphonates
[17,18],
palladium- and nickel catalyzed coupling reac-
tions of Z-α-bromoalkenylphosphonates with
arylboronic acids [8b], and finally the reaction of
O,O-diethyl S-(2-oxoalkyl)dithiophosphates and Se-
◦
dride, at the temperature of −4 C, afforded diethyl
styrylphosphonates 5a and 6a in good yields (60%)
and high Z-stereoselectivity (E/Z = 2/98, Table 1, en-
try 1). It is noteworthy that the reaction was com-
pleted very quickly (about 10 min). In turn, the use of
(2-oxoalkyl)selenophosphates with sodium diethyl
phosphite [19].
◦
potassium tert-butoxide, at −70 C for 2 h, resulted in
better yields in comparison to sodium hydride, how-
ever at the expense of stereoselectivity (E/Z = 35/65,
Table 1, entry 2). Lithium diisopropylamide (LDA)
afforded a mixture of unidentified organophospho-
rus compounds (Table 1, entry 3).
RESULTS AND DISCUSSION
Herein, we present the results of our investigation on
the olefination of carbonyl compounds by means of
diethyl thiocyanatomethylphosphonate 1, affording
the corresponding diethyl Z-1-alkenylphosphonates
In addition, we found that, regardless of the
conditions applied, the crude reaction mixture con-
tained a considerable amount of E-(2-thiocyanato-
vinyl)-benzene 7a and diethyl phosphate 8. These
byproducts could be, however, easily separated
from alkenylphosphonates 5/6a by standard aque-
ous workup and flash chromatography.
5
in moderate yields and in high stereoselectivity.
The starting diethyl thiocyanatomethylphos-
phonate [2a]
1 was prepared in 87% yield
via nucleophilic displacement of diethyl (4-
nitrobenzenesulfonyloxymethyl)-phosphonate [20]
with potassium thiocyanate in the presence of cat-
alytic amounts of 18-crown-6. The presented syn-
thesis is a modification of the procedure described
previously for the preparation of diisopropyl 1-
The presence of side products in the crude reac-
1
tion mixture was confirmed by H NMR spectrum,
showing two doublets at 6.5 and 6.9 ppm with trans
3
vicinal-coupling constant ( JHH = 15.00 Hz) diagnos-
(thiocyanato)alkylphosphonates [3].
tic for 7a, as well as by the signal of phosphate 8 at
31
1
Our initial studies concentrated on the optimiza-
1.0 ppm in the P NMR. The H NMR data are in
agreement with those obtained for E-(2-thiocyanato-
vinyl)-benzene 7a prepared independently [21].
The data given in Table 1 indicate that the olefi-
nation of benzaldehyde 2a by means of 1 and sodium
hydride gave the desired diethyl styrylphosphonates
tion of the conditions of the olefination reaction.
Thus, benzaldehyde 2a was chosen as a model car-
bonyl compound, and selected bases (NaH, t-BuOK,
lithium diisopropylamide(LDA)) were used for met-
alation of 1 (Scheme 2). The results are presented in
Heteroatom Chemistry DOI 10.1002/hc

734 Blaszczyk and Gajda
exception, for which irrespectively of the conditions
applied, high E-diastereoselectivity was observed
(
Z/E = 5/95, Table 1, entry 6). The reaction is limited
to α,β-unsaturated (cinnamaldehyde) and aromatic
aldehydes. Unfortunately, the method gave no satis-
factory results for aliphatic aldehydes and ketones
for which mixtures of unidentified organophospho-
rus compounds were formed.
The assignment of the stereochemistry of the
double bond of diethyl 1-alkenylphosphonates 5 and
6
was based on the values of vicinal proton–proton
3
3
( JHH), carbon–phosphorus ( JCP), and proton–
3
31
phosphorus ( JHP) coupling constants. The P NMR
chemical shifts and selected diagnostic couplings
constants of the diethyl 1-alkenylphosphonates 5,
and 6 are summarized in Table 2.
SCHEME 2
prepared.
Diethyl 1-alkenylphosphosphonates 5/6a–g
3
3
Thus, the values of JCP (8–10 Hz) and JHH
13–14 Hz) for diethyl Z-1 alkenylphosphonates 5
(
are smaller than the ones for E-6, (J = 23–25 Hz
5
/6a in good yields and simultaneously with high
and J = 16–17 Hz, respectively). The reverse rela-
3
diastereoselectivity.
tion is observed when it comes to J . For Z-5
HP
3
All other olefination reactions were executed
in compliance with this optimized protocol. Thus,
according to Scheme 2, a range of representa-
tive aldehydes underwent olefination with 1 in the
vicinal-coupling, constants JHP are around 47–51
Hz, whereas the E-6 are characterized by the value
in the range of 22–23 Hz. These results are in agree-
ment with the literature data [14a,22]. In addition
31
presence of 2.2 equivalents of sodium hydride at
in all P NMR spectra, the signals of the Z-isomers
5 appear at higher field than the ones of the E-5
[7h,12a,22d].
◦
−
4 C to give, after chromatography, pure diethyl
1
-alkenylphosphonates 5a–g and 6a–g in moderate
yields (Scheme 2). The results are summarized in
Table 1.
Plausible mechanistic pathways of the olefi-
nation are shown in Scheme 3. The competitive
Horner–Wadsworth–Emmons reaction, resulted in
the formation of E-(2-thiocyanato-vinyl)-arenes 7, is
responsible for decreased yields of alkenylphospho-
nates 5 and 6. The stereochemistry of olefination is
determined by combination of the stereoselectivity
The above-mentioned transformations occurred
with high Z-diastereoselectivity (Z/E = 98:2 to
72:28), and single Z-diastereomers 5a–c, e–g could
be easily isolated from the reaction mixtures by flash
chromatography. 4-Nitrobenzaldehyde 2d was the
TABLE 2 31P NMR Chemical Shifts (δ) and Selected Vicinal-Coupling Constants (J) of Diethyl 1-alkenylphosphonates 5 and 6
31P NMR δ
1
H NMR JHH
3
1
H NMR JHP
3
13
C NMR JCP
3
Entry
Compounds 5/6
R
1
2
3
4
5
6
7
8
9
Z-5a
E-6a
Z-5b
E-6b
Z-5c
E-6c
Z-5d
E-6d
Z-5e
E-6e
Z-5f
Ph
16.31
19.82
16.90
20.71
16.17
19.54
14.35
17.46
14.35
17.45
16.22
19.99
17.77
20.78
14.24
17.46
14.11
17.73
13.84
17.46
14.36
17.53
13.71
17.28
14.76
17.51
12.84
16.72
51.07
22.58
51.79
23.67
51.08
8.74
–
a
2-MeOC H4
8.43
6
a
–
2-MeC H4
8.36
6
b
a
–
–
–
a
4-O NC H
6 4
47.00
22.26
50.12
22.34
49.10
22.51
50.60
2
23.52
b
1-Naphthyl
2-Furyl
–
–
b
10
11
12
13
14
10.32
25.66
E-6f
Z-5g
E-6g
b
PhCH CH
–
–
b
b
–
a
b
Too low concentration for accurate measurement.
Overlapped with other signals.
Heteroatom Chemistry DOI 10.1002/hc

Reaction of Diethyl Thiocyanatomethylphosphonate with Aldehydes 735
SCHEME 3 Plausible mechanistic pathways of the olefination of aldehydes with 1.
of the initial carbon–carbon bond-forming step and
reversible formation of the intermediates 9, 10 and
corresponding alkenylphosphonates 5 and 6. Such
extrusion of sulfur is known to proceed stereospecifi-
cally with retention of configuration [20,22e,25], giv-
ing Z-5 as a major isomer.
17, 18.
According to Scheme 3, in the first, reversible
step [23] primary oxyanion intermediates 9 and 10,
formed from aldehyde and metalated 1, are con-
verted into appropriate cyanate derivatives 13 and
The reversed outcome of the olefination of p-
nitrobenzaldehyde 2d is still open for discussion.
However, it could be rationalized by fast isomeriza-
tion of the primarily formed Z-alkenylphosphonate
5d into the thermodynamically stable E-6d under
the reaction conditions. Slow isomerization of the
other Z-5 was also observed upon prolonged stand-
ing at room temperature.
14 via oxathiolanimine derivatives 11 and 12. The in-
termediate formation of oxathiolanimines has been
previously postulated in the ring opening of epoxides
with thiocyanates [24] and in the reactions of thio-
cyanate acetic acid esters with aldehydes [4]. Such
ring closure and subsequent intramolecular migra-
tion of the cyano group from sulfur to oxygen re-
quires synperiplanar orientation of the oxygen anion
and thiocyanate group. Hence, (RS/SR)-9, in com-
parison to (RR/SS)-10, reacts faster via the less hin-
dered transition state to give 13 as a major product.
Above-mentioned steps seem to be also reversible.
On the other hand, in the competitive HWE
reaction, oxyanion intermediates 9 and 10 could
decompose via transient four-centered interme-
diates 17 and 18 to yield (2-thiocyanato-vinyl)-
arenes 7 (Scheme 3). The formation of E-7 is
definitely preferred. Faster formation (from 10)
and syn-cycloelimination of less sterically hindered
oxaphosphetane 18 is responsible for such stereo-
chemical outcome [23].
Subsequent S 2-type cyclization of 13 and 14 leads
N
to thiiranes 15 and 16 with inversion of configura-
tion at the carbon adjacent to the phosphoryl moiety.
The episulfides are well-known precursors of
olefins [24]. Spontaneous desulfurization of the
above-mentioned episulfides, triggered by sodium
hydride, causes the conversion of 15 and 16 into the
31
1
P and H NMR spectroscopy, together with
some additional experiments, were applied to ac-
count for the formation of the postulated inter-
mediates. At first, olefination of benzaldehyde 2a
with 1 was performed using 1 equivalent of sodium
Heteroatom Chemistry DOI 10.1002/hc

736 Blaszczyk and Gajda
cyanatomethylphosphonate 1 can be the useful start-
ing material for the stereoselective synthesis of di-
ethyl Z-1-alkenylphosphonates 5, derived from aro-
matic aldehydes.
SCHEME 4 Synthesis of cis-episulfide 15a.
EXPERIMENTAL
31
hydride, instead of standard 2.2 equivalents. The
P
NMR spectrum of the crude reaction mixture ex-
hibited three signals, the major one at 20.39 ppm
assigned to cis-episulfide 15a, and two minors at
NMR spectra were recorded on a Bruker Avance
DPX 250 instrument at 250.13 MHz for H NMR,
1
1
3
31
62.90 MHz for C NMR, and 101.3 MHz for
NMR in CDCl solution, using tetramethylsilane as
internal and 85% H PO as external standard. Pos-
itive chemical shifts are downfield from external
P
16.32 and 16.71 ppm were ascribed to Z-5a and
3
the other compound, whose structure has not been
established.
3
4
3
1
The configuration of episulfides could be as-
signed on the basis of diagnostic vicinal proton–
proton coupling constants of the episulfide ring
85% H
3
PO for P NMR spectra. Chemical shifts
4
(δ) are indicated in ppm and coupling constants
(J) in Hz. Elemental analyses were performed on
a Perkin–Elmer PE 2400 analyzer. IR spectra were
measured on a Specord M80 (Zeiss) instrument and
3
trans
HH
3
cis
HH
1
(
J
<
J
) [26]. Thus, H NMR spectrum
of the above-mentioned reaction mixture shows,
among other signals, two double doublets of the
−
1
are reported in cm . Flash chromatography was
performed with glass column packed with Baker sil-
ica gel (30–60 µm). Melting points were determined
in open capillaries and are uncorrected. All reagents
were purchased from Fluka and were used without
further purification.
3
thiirane ring protons at 3.15 ppm ( JHH = 7.25 Hz.
2
3
3
J
J
PH = 9.7 Hz) and 4.30 ppm ( JHH = 7.25 Hz.
PH = 11.5 Hz), respectively. The value of 7.25 Hz
is in agreement with the literature data for cis-
episulfides [26], thus immediately confirming the
configuration of 15a.
E-(2-Thiocyanato-vinyl)-benzene 7a was pre-
pared as described in the literature [21]. Diethyl (4-
nitrobenzenesulfonyloxymethyl)-phosphonate was
obtained from diethyl hydroxymethylphosphonate
and 4-nitrobenzenesulfonyl chloride in the same
way as described previously [20]. Diethyl (3-phenyl-
oxiranyl)-phosphonates 19 (cis/trans = 91/9) were
obtained in 50% yield by dioxirane epoxidation of
diethyl styrylphosphonates 5a/6a (Z/E = 91/9), ac-
cording to the literature method [7h,12].
Attempted isolation of 15a from the reaction
mixture failed. During chromatography, extrusion
of sulfur from 15a took place and only Z-5a was
isolated.
Conversion of oxiranes into the correspond-
ing thiiranes by an oxygen-sulfur exchange reac-
tion is known as a convenient route to episul-
fides [27]. Moreover, Inokawa and Yamamoto [28]
described the efficient synthesis of dimethyl 1,2-
epithio-1-methylethanephosphonate from the ap-
propriate epoxide. However, synthesis of 15a by an
independent way has finished with limited success.
We found, as shown in Scheme 4, that treatment of
diethyl (3-phenyl-oxiranyl)-phosphonates [7h,12a]
Diethyl Thiocyanatomethylphosphonate (1) [2a]
The title compound was obtained by modification
of the method described previously [3]. The solu-
tion of diethyl (4-nitrobenzenesulfonyloxymethyl)-
phosphonate (8.20 g, 23 mmol), KSCN (8.98 g, 92
mmol), and 18-crown-6 (0.62 g, 2.3 mmol, 10 mol%)
1
9 (cis/trans = 91/9) with thiourea in methanol at
room temperature for 6 h produced a mixture of
starting 19 (64%, δ
P
= 17.27), cis-episulfide 15a (6%,
= 20.7), diethyl Z-styrylphosphonate 5a (21%,
= 16.3), and diethyl E-styrylphosphonate 6a (9%,
δ
δ
δ
P
P
P
in CH CN (230 mL) was refluxed for 3 h. Then,
3
the solvent was evaporated under reduced pres-
sure and the solid residue was extracted with di-
ethyl ether (3 × 80 mL). Ether was evaporated un-
der reduced pressure, and the yellow oily residue
was distilled under reduced pressure (bulb to bulb,
31
= 19.8), as determined by P NMR. Unfortu-
nately, as a result of desulfurization, the concentra-
tion of 15a in the reaction mixture was very low.
The thiiranes, substituted by aromatic residues and
electron-withdrawing groups, are known to form
olefins even at room temperature [4]. Nevertheless,
this experiment confirmed the intermediate forma-
tion of cis-episulfides during the olefination of alde-
hydes with 1.
◦
150 C, 0.05 mmHg) to give analytically pure 1 (2.22
g, 87% yield), as a colorless oil. IR (film): ν = 2160
−
1
1
cm (s), 2984 (m), 1260 (s), 1024 (m). H NMR
3
(250 MHz, CDCl
2CH CH
4.24 (qt, JH,H = 7.08 Hz, 4H, 2CH
NMR (63 MHz, CDCl
3
): δ = 1.40 (t, JH,H = 7.06 Hz, 6H,
2
3
2
O), 3.15 (d, JH,P = 12.53 Hz, 2H, CH
2
13
P),
C
3
In conclusion, the results presented in this pa-
per demonstrate that easily available diethyl thio-
3
CH
2
O) ppm.
3
3
): δ = 15.9 (d, JC,P = 5.83 Hz,
Heteroatom Chemistry DOI 10.1002/hc

Reaction of Diethyl Thiocyanatomethylphosphonate with Aldehydes 737
1
3
2
CH
3
2
CH
J
2
O), 25.3 (d, JC,P = 150, 5 Hz, CH
2
P), 63.1
O), 72.8 (SCN) ppm.
qt,
J
H,H = 7.13 Hz, 4H, 2CH
3
CH O), 5.80 (dd,
2
3
3
(
d,
C,P = 5.8 Hz, 2CH
3
CH
2
J
J
H,H = 14.11,
J
H,P = 17.16 Hz, 1H, CHP), 6.86 (d,
3
1
3
3
P NMR (101 MHz, CDCl
209.20): calcd. C 34.45, H 5.78, N 6.70; found C
4.35, H 5.76, N 6.72.
3
): δ = 18.63. C
6
H
12NO
3
PS
H,H = 8.30 Hz, 1H, Har), 6.97 (t, JH,H = 7.54 Hz, 1H,
3
(
3
H
ar), 7.33 (bt,
J
H,H = 7.99 Hz, 1H, Har), 7.53 (dd,
3
3
J
H,H = 14.09,
J
H,P = 51.79 Hz, 1H, CHCHP), 7.84
3
13
(bd,
J
H,H = 7.64 Hz, 1H, Har) ppm. C NMR (63
3
MHz, CDCl
5.2 (CH
3
): δ = 15.8 (d, JC,P = 6.6 Hz, 2CH
3
CH
CH
2
O),
O),
General Procedure for the Preparation of Diethyl
-Alkenylphosphonates 5/6a–g Using NaH As a
Base.
2
5
1
3
O), 61.3 (d,
JC,P = 5.9 Hz, 2CH
3
2
1
1
09.7 (Car), 115.9 (d, JC,P = 185.9 Hz, CHP), 119.9
3
(
C
ar), 124.3 (d, JC,P= 8.4 Hz, CCHCHP), 130.5 (Car
)
◦
To a cooled to −4 C suspension of sodium hydride
31
1
43.9 (CHCHP), 157.0 (Car) ppm. P NMR (101
(
0.158 g, 6.6 mmol) in anhydrous THF (20 mL), the
MHz, CDCl
C 57.77, H 7.09; found C 57.65, H 7.08.
3
): δ = 16.90. C13
H
19
O P (270.26): calcd.
4
solution of aldehyde 2a–g (3.15 mmol) and 1 (0.627
g, 3 mmol) in THF (5 mL) was added dropwise for
2
0 min. Then the reaction mixture was stirred for
Diethyl Z-(2-o-Tolyl-vinyl)-phosphonate (5c)
7h,29]. Z-5c was isolated by flash chromatog-
raphy (ethyl acetate/hexane, 2:1) as a yellow oil.
◦
1
0 min from −4 to 0 C and for 10 min at room
[
temperature. The resultant mixture was quenched
with 5% aqueous solution of KHSO
evaporated under reduced pressure; the residue was
dissolved in CH Cl (80 mL) and washed with 5%
KHSO
CH Cl
4
. Solvent was
Yield: 32%. IR (film): ν = 2984 (m), 1608 (m), 1244
−1
1
(
s), 1028 (s), 780 (m) cm . H NMR (250 MHz,
2
2
3
4
CDCl
3
): δ = 1.12 (dt, JH,H = 7.08, JH,P = 0.46 Hz, 6H,
CH O), 2.29 (s, 3H, CH ), 3.78–4.01 (m, 4H,
CH
4
(10 mL). Water layer was re-extracted with
(20 mL). The combined organic layers were
2
2
1
1
CH
3
2
3
2
2
3
2
CH
3
2
O), 5.90 (dd, JH,H = 13.84, JH,P = 17.80 Hz,
washed successively with brine (2 × 5 mL) and H
2
O
3 3
H, CHP), 7.42 (dd, JH,H = 13.83, JH,P = 51.08 Hz,
(5 mL), dried over anhydrous MgSO , and evapo-
4
H, CHCHP), 7.13–7.28 (m, 3H, Har), 7.59–7.65
rated under reduced pressure to give the mixture of
diethyl 1-alkenylphosphonates 5/6. Analytically pure
phosphonates 5/6 or single Z-isomers 5 (E-isomer in
case of 6d) were isolated after flash chromatography
on silica gel. The results are summarized in Tables 1
and 2.
13
(
m, 1H, Har) ppm. C NMR (63 MHz, CDCl
3
):
O), 19.0 (CH3),
CH O), 117.6 (d,
3
δ = 15.4 (d,
J
C,P = 6.6 Hz, CH
3
CH
3
2
2
6
0.7 (d,
J
C,P = 5.7 Hz, 2CH
2
1
J
C,P = 185.9 Hz, CHP), 124.8, 128.3, 128.7, 128.8
3
(C
ar) 134.6 (d, JC,P = 8.4 Hz, CCHCHP), 135.1 (Car),
31
1
46.6 (CHCHP) ppm. P NMR (101 MHz, CDCl ):
3
δ = 16.17. C13
H
19
O P (254.26): calcd. C 61.41, H 7.53;
3
Diethyl Z-Styrylphosphonate (5a) [7e,12a]. Z-
a was isolated by flash chromatography (ethyl
found C 61.30, H 7.50.
5
acetate/hexane, 5:7) as a yellow oil. Yield: 55%.
Diethyl E-[2-(4-Nitro-phenyl)-vinyl]-phosphonate
(5d) [30]. E-5d was isolated by flash chromatog-
raphy (chloroform/acetone, 3:1) as a yellow crys-
IR (film): ν = 2984 (m), 1608 (s), 1244 (s),
−
1
1
1
028 (m), 728 (s) cm . H NMR (250 MHz,
3
CDCl
3
): δ = 1.19 (t, JH,H = 7.00 Hz, 6H, 2CH
3
CH O),
CH O), 5.81
2
◦
3
talline solid, mp. 104–106 C. Lit [30] mp. 102–
4.00 (qt,
J
H,H = 7.23, Hz, 4H, 2CH
3
2
◦
3
2
103.5 C. Yield: 22%. IR (film): ν = 2984 (m), 1598
(
t,
J
J
H,H = JH,P = 14.24, Hz, 1H, CHP), 7.29 (dd,
−
1
1
3
3
(m), 1240 (s), 1022 (s), 780 (m) cm . H NMR
H,H = 14.23, JH,P = 51.07 Hz, 1H, CHCHP), 7.26–
3
1
3
(250 MHz, CDCl
2CH CH
2CH CH
3
): δ = 1.38 (t, JH,H = 7.07 Hz, 6H,
7
.70 (m, 5H, Har) ppm.
C NMR (63 MHz,
C,P = 6.3 Hz, 2CH CH O),
C,P = 6.3 Hz, 2CH CH O), 116.8 (d,
3
3
3
2
O), 4.17 (broad qt,
J
H,H = 7.00 Hz, 4H,
CDCl
3
): δ = 15.9 (d,
J
3
2
3
2
2
3
2
O), 6.44 (dd, JH,H = 17.53, JH,P = 16.28 Hz,
6
J
1.6 (d,
J
3
2
3
3
1
1H, CHP,), 7.54 (dd, JH,H = 17.54, JH,P = 22.26 Hz,
C,P = 188.7 Hz, CHP), 128.1, 129.2, 129.5 (Car),
3
3
1H, CHCHP), 7.65 (d, JH,H = 8.72 Hz, 2H, Har), 8.25
1
35.2 (d, JC,P = 8.7 Hz, CCHCHP), 148.3 (CHCHP)
3
13
3
1
(d,
J
H,H = 8.75 Hz, 2H, Har) ppm. C NMR (63
ppm.
C
P NMR (101 MHz, CDCl
3
): δ = 16.31.
3
MHz, CDCl
3
): δ = 16.2 (d, JC,P = 6.2 Hz, 2CH
3
CH O,)
2
12
H
17
O P (240.24): calcd. C 59.99, H 7.13; found
3
2
6
J
1.9 (d,
J
C,P = 5.6 Hz, 2CH3CH2O), 119.3 (d,
C 59.81, H 7.10.
1
C,P = 190.0 Hz, CHP), 123.9, 128.1 (Car), 140.6 (d,
3
Diethyl Z-[2-(2-Methoxy-phenyl)-vinyl]-phospho-
nate (5b) [7h,29]. Z-5b was isolated by flash chro-
matography (ethyl acetate/hexane, 2:1) as a yellow
oil. Yield: 21%. IR (film): ν = 2984 (m), 1600 (s),
JC,P = 23.5 Hz, CCHCHP), 145.2 (CHCHP), 148.2
31
(C ) ppm. P NMR (101 MHz, CDCl ): δ = 17.46.
ar
3
C H NO P (285.23): calcd. C 50.53, H 5.65, N 4.91;
12
16
5
found C 50.47, H 5.60, N 4.88.
−
1
1
1
248 (s), 1028 (s), 756 (s) cm . H NMR (250 MHz,
3
4
CDCl
3
): δ = 1.16 (dt,
J
H,H = 7.06,
J
H,P = 0.54 Hz,
Diethyl Z-(2-Naphthalen-1-yl-vinyl)-phosphonate
(5e) [7e,12]. Z-5e was isolated by flash
6H, 2CH
3
CH
2
O), 3.84 (s, 3H, CH
3
O), 3.96 (broad
Heteroatom Chemistry DOI 10.1002/hc

738 Blaszczyk and Gajda
chromatography (ethyl acetate/toluene, 10:1) as
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608 (w), 1244 (s), 1028 (s), 784 (m) cm . H NMR
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3
(
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(
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3
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2
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992, 62, 1268–1271; (b) Firouzabadi, H.; Iranpoor,
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.61 (m, 3H, Har), 7.77–7.92 (m, 4H, Har), 7.90 (dd,
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J
H,H = 13.77,
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H,P = 50.12 Hz, 1H, CHCHP) ppm.
[
[
13
3
C NMR (63 MHz, CDCl
3
): δ = 15.9 (d, JC,P = 6.6 Hz,
2
2
1
1
CH
20.0 (d, JC,P = 186.2 Hz, CHP), 124.0, 125.2, 125.9,
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1
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1
1%. IR (film): ν = 2984 (m), 1624 (m), 1244 (s),
024 (s), 756 (w) cm . H NMR (250 MHz, CDCl ):
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H,P = 7.79 Hz, 4H, 2CH CH O),
(
b) Kuono, R.; Tsubota, T.; Okauchi, T;. Minami, T.
−
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1
3
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δ = 1.26 (t,
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3
CH
2
3
3
(dq,
J
H,H = 7.00,
J
3
2
3
2
5
J
.57 (t, JH,H
=
J
H,P = 14.76 Hz, 1H, CHP) 7.01 (dd,
3
3
H,H = 14.67,
J
H,P = 49.10 Hz, 1H, CHCHP), 6.47
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3
3
(
dd,
J
J
H,H = 3.6,
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H,H = 1.8 Hz, 1H, Har), 7.20 (d,
3
3
H,H = 3.5 Hz, 1H, Har), 7.50 (bd, JH,H = 1.7 Hz, 1H,
13
1
997, 53, 16609–16644; (c) Kim, D. Y.; Rhie, D. Y.
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Tetrahedron 1997, 53, 13603–13608; (d) Cravotto,
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C,P = 6.29 Hz, 2CH
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1
2
1
CH CH O), 111.0 (d,
12.3, 115.3 (Car) 134.1 (CHCHP), 144.1 (Car), 150.9
3
2
J
C,P = 188.63 Hz, CHP),
7
48; (e) Yokomatsu, T;. Yamagishi, T.; Suemune, K.;
3
31
(
d, JC,P = 10.32 Hz, CCHCHP) ppm. P NMR (101
MHz, CDCl P (230.20): calcd. C
): δ = 16.22. C10
2.18, H 6.57; found C 52.20, H 6.50.
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1
80; (f) Thomas, A. A.; Sharpless, K. B. J Org Chem
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4
5
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2
185–2187; (j) Kobayashi, Y;. William, A. D.; Tokoro,
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(
s), 1584 (s), 1244 (s), 1028 (s), 784 (w) cm . 1H
3
NMR (250 MHz, CDCl
3
): δ = 1.34 (t, JH,H = 7.00 Hz,
7
3
6
2
1
7
H, 2CH
3
CH
2
O), 4.11 (broad qt, JH,H = 7.16 Hz, 4H,
3
2
CH CH
3
2
O), 5.56 (dd, JH,H = 12.84, JH,P = 16.83 Hz,
9
3
H, CHP), 6.75 (d,
J
H,H = 15.58 Hz, 1H, CHPh),
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.00 (dt, JH,H = 12.13, JH,P 50.60 Hz, 1H, CHCHP),
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7
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3
): δ = 16.2 (d, JC,P = 6.4 Hz, 2CH
3
CH O),
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6
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P NMR (101 MHz, CDCl
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.21.
3
): δ = 17.77. C14
H
19
3
O P
(
7
Heteroatom Chemistry DOI 10.1002/hc

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