Regioselective anodic fluorination of α-(arylthio)benzylphosphonate esters, α-(arylthio)methylphosphonate esters and their analogues

Article abstract of DOI:10.1055/s-2007-977439

Regioselective anodic α-fluorination of α-(arylthio) benzylphosphonate esters and [(arylthio)methyl]- and [(heteroarylthio)methyl] phosphonate esters was successfully carried out at a glassy carbon anode or platinum anode in dimethoxyethane and nitrometha

Full text of DOI:10.1055/s-2007-977439

1148
CLUSTER
Regioselective Anodic Fluorination of a-(Arylthio)benzylphosphonate Esters,
a-(Arylthio)methylphosphonate Esters and Their Analogues
Regioselective
An
s
odic Fluor
a
ination of
a
m
-(Arylthio)benzylp
i
E
H
sters idaka, Bakenova Zagipa, Hirokatsu Nagura, Toshio Fuchigami*
Department of Electronic Chemistry, Tokyo Institute of Technology, Nagatsuta, Midori-ku, Yokohama 226-8502, Japan
Fax +81(45)9245406; E-mail: fuchi@echem.titech.ac.jp
Received 5 January 2007
approach to give fluorinated phosphonates.5,6 Previously,
we have successfully carried out the anodic fluorination of
benzylphosphonate derivatives as shown in Scheme 1.5
However, the anodic fluorination of an unsubstituted ben-
Abstract: Regioselective anodic a-fluorination of a-(arylthio)ben-
zylphosphonate esters and [(arylthio)methyl]- and [(heteroaryl-
thio)methyl]phosphonate esters was successfully carried out at a
glassy carbon anode or platinum anode in dimethoxyethane and
nitromethane to provide the corresponding a-fluorophosphonate zylphosphonate ester required an extremely large excess
esters in excellent to moderate yields.
of electricity (28 F/mol) due to its high oxidation potential
(Epox: 2.39 V vs SSCE).
Key words: electrochemical fluorination, a-fluorophosphonate es-
ter, Emmons–Wittig reagent, anodic substitution, electrosynthesis
It is well known that phenylthio groups are easily oxidized
and also readily eliminated reductively. For example, re-
ductive elimination of the phenylsulfonyl group from
Naturally occurring phosphonate moieties play critical
roles in a wide-variety of biochemical processes. Recent-
ly, many studies have indicated that the presence of the
fluorine atoms at the a-position of phosphorous in phos-
phonate increases both the structural and electronic simi-
larities to the parent phosphate groups.1 Therefore, much
effort has recently been directed towards constructing
nonhydrolyzable phosphate mimics; a-fluoro- and a,a-di-
fluoromethylene groups have been widely recognized as
isoelectronic and isosteric replacements for oxygen in
phosphate groups. From a synthetic viewpoint, various
new fluorinating reagents such as diethylaminosulfur tri-
fluoride (DAST) and Selectfluor have been developed.2,3
However, these conventional fluorinating reagents have
serious drawbacks as they are expensive, toxic, corrosive
and sometimes explosive. We have shown that selective
electrochemical fluorination is a highly efficient tool in
the synthesis of various fluorinated organic compounds
and this method has the advantage of mild conditions and
the avoidance of hazardous and explosive reagents.4 It is
for these reasons that we thought to try an electrochemical
[fluoro(phenylsulfonyl)methyl]phosphonate is easily
achieved using Na–Hg.7
Reductive cyclization of diethyl [1-fluoro-1-(2-pyr-
imidylsulfonyl)-5-hexenyl]phosphonate has also been
reported as shown in Scheme 2.8 Furthermore,
[fluoro(phenylsulfonyl)methyl]phosphonate is well
known as an Emmons–Wittig reagent used in the prepara-
tion of various fluoroolefins as shown in Scheme 3.9
R2
R1
F
R2
R1
F
R2
R1
[PhSO2CFP(O)(OEt)2]–
O
H
SO2Ph
Scheme 3
We have successfully carried out the anodic a-fluorina-
tion of various sulfides.10 For example, we have achieved
the anodic a-fluorination of a-(phenylthio)phosphonate
ester as shown in Scheme 4.11 However, constant poten-
tial electrolysis (CPE) was necessary in this case.
–2e–, – H+
F
F
– 2e–, – H+
PhS
P(O)(OEt)2
Ph
P(O)(OEt)2
Et3N·3HF–MeCN
PhS
P(O)(OEt)2
Ph
P(O)(OEt)2
Et4NF·3HF–DME
CPE
28 F/mol
78%
57%
Scheme 4
Scheme 1
O
P
O
O
O
P
I
O
P
Bu3SnH, AIBN
benzene
N
S
OEt
OEt
OEt
OEt
OEt
OEt
R
F
N
F
F
R = (CH2)3CH=CH2
Scheme 2
SYNLETT 2007, No. 7, pp 1148–1152
2
4.
0
4.
2
0
0
7
Advanced online publication: 13.04.2007
DOI: 10.1055/s-2007-977439; Art ID: Y00207ST
© Georg Thieme Verlag Stuttgart · New York

CLUSTER
Regioselective Anodic Fluorination of a-(Arylthio)benzylphosphonate Esters
1149
Table 1 Anodic Fluorination of Diethyl a-(Phenylthio)benzylphosphonate
SPh
P(O)(OEt)2
F
SPh
P(O)(OEt)2
F
F
– e–
+
P(O)(OEt)2
Et4NF·3HF
CCE
1
2a
2b
Entry
Solvent
Electrode
Charge passed (F/mol) Ratio (2a:2b)
Total yield (%)a
1
2
3
4
5
MeCN
DME
Pt
4
3
3
4
3
2:1
3:1
35
Pt
46
MeNO2
DME
Pt
1:1
8
GC
GC
50:1
50:1
94 (82)b
96 (81)b
MeNO2
a Determined by 19F NMR spectroscopy.
b Isolated yield of 2a.
With these facts in mind, we studied the anodic fluorina-
tion of various derivatives of a-(arylthio)phosphonate es-
ter under various conditions. At first, we investigated the
anodic fluorination of diethyl a-(phenylthio)benzylphos-
phonate (1) in various solvents containing Et4NF·3HF as
a supporting electrolyte and a fluorine source using an
undivided cell.12 Constant current electrolysis (CCE) was
carried out at platinum and glassy carbon (GC) anodes.
The results are summarized in Table 1.
Regardless of the electrolytic solvents, the electrolysis at
a platinum anode afforded the desired monofluorinated
product 2a13 in low yields and the difluorinated byproduct
2b was always formed. In sharp contrast, the use of a
glassy carbon anode in dimethoxyethane (DME) provided
a-monofluorinated product 2a in high yield and the
formation of byproduct 2b was suppressed considerably.
It is quite interesting that although a platinum anode in
nitromethane was not suitable for the fluorination, the use
of a GC anode in the same solvent gave an excellent yield
of 2a. Since the oxidation potential of 1 (Epox: 1.65 V vs
SSCE) is much lower when compared to a benzylphos-
Figure 1 Current–potential curves of 1 (8 mM) in Et4NF·3HF–
DME (1M)
electrolysis was carried out at a GC anode in Et4NF·3HF–
MeNO2. As shown in Table 2, the anodic fluorination of
3 and 4 proceeded smoothly to provide the corresponding
a-fluorinated products 614 and 715 in excellent yields. 1-
Naphthyl derivative 5 also underwent anodic fluorination
and monofluorinated product 816 was formed in moderate
yield.
ox
phonate devoid of a phenylthio group (Ep : 2.39 V vs
SSCE), the current efficiency for the anodic fluorination
of 1 was much higher than that of benzylphosphonate.
In order to clarify the reason why a GC anode was so
effective for the anodic fluorination, current–potential
curves of 1 were measured at the GC and platinum anodes
in DME. As shown in Figure 1, the current due to the
oxidation of substrate 1 at a GC anode was much larger
than that at a platinum anode although background cur-
rents at both anodes were almost the same. This result
clearly indicates that a GC anode is much more effective
for the oxidation of 1 compared with a platinum anode.
Thus, the highly efficient anodic fluorination of 1 at a GC
anode was reasonably explained.
It is well known that a sulfone group can be the activating
moiety for carbon–carbon bond formation and other trans-
formations. Pyridylsulfonyl and pyrimidylsulfonyl groups
are much more effective in their reductive elimination
compared with a phenylsulfonyl group as exemplified in
Scheme 2.7,8 Therefore, anodic fluorination of phospho-
nates with heteroarylthio groups such as pyridylthio and
pyrimidinylthio groups were investigated. We carried out
the anodic fluorination of a-(phenylthio)-a-(2-pyridyl)-,
and a-(phenylthio)-a-(4-pyridyl)benzylphosphonates (9
and 10) at a GC anode in DME as shown in Table 3. In
both cases 9 and 10, the anodic fluorination proceeded
well to provide the a-fluorinated products 1117 and 1218
in high yields. Since 10 has a higher oxidation potential
Next, we extended this anodic fluorination to a-(phenyl-
thio)benzylphosphonate derivatives 3, 4 and diethyl
[(phenylthio)(1-naphthyl)methyl]phosphonate (5). The
Synlett 2007, No. 7, 1148–1152 © Thieme Stuttgart · New York

1150
A. Hidaka et al.
CLUSTER
Table 2 Anodic Fluorination of Diethyl a-(Arylthio)benzyl-
phosphonate Derivatives 3–5
Table 4 Anodic Fluorination of Diethyl [(arylthio)methyl]phos-
phonate 13–16
F
Y
Y
F
– ne–
– 2e–, – H+
ArS
P(O)(OEt)2
13–16
ArS
P(O)(OEt)2
17–20
PhS
P(O)(OEt)2
PhS
P(O)(OEt)2
6–8
Et4NF·3HF–MeNO2
Et4NF·3HF–DME
CCE, Pt anode
CCE, GC anode
3–5
Entry Substrate
Y
Charge passed Yield
(F/mol)
Entry Substrate Ar
Charge passed Yield
(F/mol)
(%)a
(%)a
1
2
3
3
4
5
3
6 91 (83)b
1
2
3
4
13
14
15
16
3
17 84 (78)b
MeO
I
7 98 (82)b
8 68 (61)b
3.5
24
18 91 (82)b
19 97 (91)b
20 80 (72)b
3
4
N
N
a Determined by 19F NMR.
b Isolated yield.
10
N
N
a Determined by 19F NMR.
b Isolated yield.
Table 3 Anodic Fluorination of a-(Pyridylthio)benzylphosphonate
9 and 10
Ph
– 2e–, – H+
Ph
ArS
F
– 2e–, – H+
Et3N·3HF–MeCN
F
P(O)(OEt)2
2a, 11, 12
ArS
P(O)(OEt)2
1, 9, 10
Et4NF·3HF–DME
CCE, GC anode
N
S
P(O)(OEt)2
N
S
P(O)(OEt)2
20%
Entry Substrate Ar
Charge passed Yield
(F/mol)
(%)a
Scheme 5
1
2
1
9
4
2a 94 (82)b
marked increase in yield and current efficiency can be ex-
plained in terms of anodic stability of the supporting fluo-
ride salt used and the enhanced nucleophilicity of fluoride
ions by DME.20,21 In these cases, a platinum anode was
also effective for the anodic fluorination. Although an ex-
tremely large excess amount of electricity was required to
complete the electrolysis of diethyl [(4-pyridylthio)meth-
yl]phosphonate (15) owing to its high oxidation potential
(Epox: 2.23 V vs SCE), a-fluorinated product 1922 was
formed in almost quantitative yield. Since diethyl [(2-pyr-
imydylthio)methyl]phosphonate (16) also has a high
oxidation potential (Epox: 2.15 V vs SCE), a large excess
amount of electricity was needed to provide a-fluorinated
product 2023 in high yield.
6
11 89 (81)b
12 88 (82)b
N
3
10
25
N
a Determined by 19F NMR.
b Isolated yield.
(Epox: 1.90 V vs SCE) than 9 (Epox: 1.75 V vs SCE), a large
excess amount of electricity was required for the complete
electrolysis.
Furthermore, we investigated the similarly anodic fluori-
nation of various [(aylthio)methyl]phosphonates using a
platinum anode. The results are summarized in Table 4.
Previously, we had to carry out CPE of diethyl [(phenyl-
thio)methyl]phosphonate (13) in order to obtain the
monofluorinated product 17 selectively.11 However, CCE
in Et4NF·3HF–DME was found to be suitable for the
selective formation of 17 in high yield. In this case, the
anodically prepared monofluoroproduct 17 was treated
with m-chloroperbenzoic acid to provide the correspond-
ing sulfone derivative 21 in good total yield (74% from
13) as shown in Scheme 6. Thus, we were able to
efficiently prepare the Emmons–Wittig reagent using the
anodic fluorination as a key step.
In our previous study, the anodic fluorination of diethyl
[(2-pyridylthio)methyl]phosphonate (14) in Et3N·3HF–
MeCN resulted in a low yield of the a-fluorinated product
18 as shown in Scheme 5.19 In this case, an excess amount
of electricity (6 F/mol) was required to complete the
electrolysis.
The anodic fluorination in Et4NF·3HF–DME required just
3 F/mol of electricity and the yield was excellent. The
Synlett 2007, No. 7, 1148–1152 © Thieme Stuttgart · New York

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Regioselective Anodic Fluorination of a-(Arylthio)benzylphosphonate Esters
1151
F
F
– e–
13
MCPBA
PhS
P(O)(OEt)2
PhO2S
P(O)(OEt)2
Et4NF·3HF–DME
CH2Cl2
17
84%
21
total yield 74%
Scheme 6
through a short column filled with silica gel using EtOAc as
an eluent to remove fluoride salts. The eluent was
evaporated under reduced pressure, and the residue was
further purified by column chromatography on silica gel
using EtOAc to give pure fluorinated products. The products
were identified by spectroscopic data.
The fluorination of a-(arylthio)phosphonate esters seems
to proceed via a fluorosulfonium ion intermediate in a
Pummerer-type mechanism as reported previously.11
In conclusion, we have developed a practical new path-
way to the synthesis of various fluorinated a-(aryl-
thio)phosphonate ester derivatives. This electrochemical
method seems to be highly useful in the preparation of
various new types of a-fluorophosphonate esters.
(13) Diethyl a-Fluoro-a-(phenylthio)benzylphosphonate (2a):
1H NMR (CDCl3): d = 1.11 (t, J = 7.09 Hz, 3 H), 1.31 (t,
J = 7.09 Hz, 3 H), 3.69–3.79 (m, 1 H), 3.91–4.02 (m, 1 H),
4.05–4.22 (m, 2 H), 7.13–7.55 (m, 10 H); 13C NMR (CDCl3):
d = 16.3 (d, JPC = 11.7 Hz), 16.4 (d, JPC = 11.7 Hz), 64.4 (dd,
JFC = 0.02 Hz, JPC = 7.27 Hz), 64.6 (dd, JFC = 0.02 Hz,
Acknowledgment
JPC = 7.27 Hz), 106.2 (dd, JPC = 175.7 Hz, JFC = 234.3 Hz),
126.3 (t, J = 3.91 Hz), 126.4 (t, J = 3.91 Hz), 127.7 (t,
B. Zagipa is deeply indebted to UNESCO and the Japanese Ministry
of Education, Science, and Culture (Monbusho) for granting her a
research fellowship (2002–2003).
J
PC = JFC = 1.68 Hz), 128.3, 128.7 (d, J = 1.68 Hz), 129.0,
134.8 (d, J = 22.4 Hz), 135.9 (d, J = 2.24 Hz); 19F NMR
(CDCl3): d = –67.3 (d, JPF = 90.4 Hz); HRMS: m/z calcd for
C17H20FO3PS: 354.0855; found: 354.0843.
References and Notes
(14) Diethyl a-Fluoro-a-(phenylthio)-4-methoxybenzylphos-
phonate (6): 1H NMR (CDCl3): d = 1.14 (t, J = 6.75 Hz, 3
H), 1.32 (t, J = 6.75 Hz, 3 H), 3.80 (s, 3 H), 3.91–3.97 (m, 1
H), 4.07–4.19 (m, 1 H), 4.29–4.33 (m, 2 H), 6.83 (d, J = 8.64
(1) Romanenko, V. D.; Kukhar, V. P. Chem. Rev. 2006, 106,
3868.
(2) Berkowitz, D. B.; Bose, M.; Pfannenstied, T. J.; Doukov, T.
J. Org. Chem. 2000, 65, 4498.
(3) Wnuk, S. F.; Robins, M. J. J. Am. Chem. Soc. 1996, 118,
2519.
(4) (a) Fuchigami, T.; Tajima, T. In Fluorine-Containing
Synthons, ACS Symposium Series 911; Soloshonok, V. A.,
Ed.; American Chemical Society: Washington DC, 2005,
276. (b) Fuchigami, T. Organic Electrochemistry, 4th ed.;
Lund, H.; Hammerich, O., Eds.; Marcel Dekker: New York,
2001, Chap. 25.
Hz, 2 H), 7.36–7.58 (m, 5 H), 7.63 (d, J = 7.83 Hz, 2 H); 13
NMR (CDCl3): d = 16.1 (d, JPC = 5.56 Hz), 16.3 (d,
C
JPC = 5.56 Hz), 64.6 (dd, JFC = 1.68 Hz, JPC = 7.25 Hz), 65.2
(d, JPC = 6.70 Hz), 106.4 (dd, JPC = 162.3 Hz, JFC = 229.2
Hz), 113.4 (t, JPC = JFC = 1.68 Hz), 113.6 (t, JPC = JFC = 1.68
Hz), 127.7 (d, JPC = 3.35 Hz), 127.8 (d, JPC = 3.35 Hz),
130.4, 134.1, 134.5 (d, J = 2.80 Hz), 160.6;19F NMR
(CDCl3): d = –89.0 (d, JPF = 68.3 Hz); HRMS: m/z calcd for
C18H22FO6PS: 416.0859; found: 416.0862.
(15) Diethyl a-Fluoro-a-(phenylthio)-4-iodebenzylphos-
phonate (7): 1H NMR (CDCl3): d = 1.09 (t, J = 7.09 Hz, 3
H), 1.29 (t, J = 7.09 Hz, 3 H), 3.69–3.78 (m, 1 H), 3.93–4.01
(m, 1 H), 4.09–4.22 (m, 2 H), 7.13–7.25 (m, 5 H), 7.40 (d,
J = 7.03 Hz, 2 H), 7.54 (d, J = 7.03 Hz, 2 H); 13C NMR
(CDCl3): d = 16.2 (d, JFC = 11.7 Hz), 16.4 (d, JPC = 11.7 Hz),
64.3 (dd, JFC = 1.68 Hz, JPC = 7.27 Hz), 64.6 (dd, JFC = 1.68
Hz, JPC = 7.27 Hz), 106.0 (dd, JPC = 174.6 Hz, JFC = 233.7
Hz), 126.3 (t, JPC = JFC = 7.83 Hz), 126.4 (t, JPC = JFC = 7.83
Hz), 127.7 (t, JPC = JFC = 1.68 Hz), 128.3, 128.6 (d, J = 7.83
Hz), 129.0, 134.9 (d, J = 22.9 Hz), 135.8 (d, J = 1.68 Hz);
19F NMR (CDCl3): d = –67.3 (d, JPF = 64.5 Hz); HRMS:
m/z calcd for C17H19FIO3PS: 479.9821; found: 479.9809.
(16) Diethyl [Fluoro(2-naphthyl)(phenylthio)methyl]phos-
phonate (8): 1H NMR (CDCl3): d = 1.07 (t, J = 7.02 Hz, 3
H), 1.28 (t, J = 7.02 Hz, 3 H), 3.65–3.78 (m, 1 H), 3.91–4.04
(m, 1 H), 4.12–4.25 (m, 2 H), 7.07–7.16 (m, 3 H), 7.41–7.47
(m, 4 H), 7.47–7.79 (m, 4 H), 7.94 (m, 1 H); 13C NMR
(CDCl3): d = 16.3 (d, JPC = 5.56 Hz), 16.4 (d, JPC = 5.56 Hz),
64.5 (d, JPC = 7.26 Hz), 65.2 (d, JPC = 7.26 Hz), 106.2 (dd,
(5) Zagipa, B.; Hidaka, A.; Cao, Y.; Fuchigami, T. J. Fluorine
Chem. 2006, 127, 552.
(6) Cao, Y.; Hidaka, A.; Tajima, T.; Fuchigami, T. J. Org.
Chem. 2005, 70, 9614.
(7) Wnuk, S. F.; Bergolla, L. A.; Garcia, P. I. J. Org. Chem.
2002, 67, 3065.
(8) (a) Trost, B. M.; Salzmann, T. N.; Hiroi, K. J. Am. Chem.
Soc. 1976, 98, 4887. (b) Trost, B. M. Acc. Chem. Res. 1978,
11, 453.
(9) (a) McCarthy, J. R.; Huber, E. W.; Matthews, L. D.
Tetrahedron 1996, 52, 45. (b) Shen, Y.; Wang, G. Org. Lett.
2002, 2083. (c) Berkowitz, D. B.; Bose, M.; Nathan, G. Org.
Lett. 2001, 2009.
(10) (a) Fuchigami, T.; Shimojo, M.; Konno, A.; Nakagawa, K. J.
Org. Chem. 1990, 55, 6074. (b) Dawood, K. M.; Higashiya,
S.; Hou, Y.; Fuchigami, T. J. Org. Chem. 1999, 64, 7935.
(c) Cao, Y.; Fuchigami, T. J. Electroanal. Chem. 2006, 587,
25.
(11) Fuchigami, T.; Shimojo, M.; Konno, A.; Nakagawa, K.
J. Org. Chem. 1994, 59, 5937.
J
J
PC = 176.8 Hz, JFC = 234.3 Hz), 124.0 (dd, JPC = 2.80 Hz,
FC = 5.59 Hz), 125.8 (dd, JPC = 5.59 Hz, JFC = 9.50 Hz),
(12) Typical procedure for anodic fluorination: Anodic
oxidation of 1 (0.5 mmol) was carried out in an undivided
cell equipped with a GC plate anode (2 × 2 cm2) and platinum
plate cathode (2 × 2 cm2) in Et4NF·3HF–DME (1 M, 5 mL)
at r.t. Constant current (2.5 mA/cm2) was passed until the
starting material 1 was almost consumed (monitored by
TLC). After electrolysis, the electrolytic solution was passed
126.1, 126.5, 127.4, (d, JFC = 6.10 Hz), 128.4, 128.5, 128.8,
132.4 (t, JFC = 11.1 Hz), 132.8, 135.8; 19F NMR (CDCl3):
d = –65.9 (d, JPF = 92.5 Hz); HRMS: m/z calcd for
C21H22FO3PS: 404.1011; found: 404.1007.
Synlett 2007, No. 7, 1148–1152 © Thieme Stuttgart · New York

1152
A. Hidaka et al.
CLUSTER
(17) Diethyl a-Fluoro-a-(2-pyridylthio)benzylphosphonate
(11): 1H NMR (CDCl3): d = 1.14 (t, J = 7.02 Hz, 3 H), 1.26
(t, J = 7.02 Hz, 3 H), 3.89 (q, J = 7.29 Hz, 1 H), 4.14 (q,
J = 6.48 Hz, 1 H), 4.34 (q, J = 6.9 Hz, 2 H), 6.90–7.56 (m,
8 H), 8.34 (d, J = 4.86 Hz, 1 H); 13C NMR (CDCl3): d =
16.33 (d, JPC = 10.62 Hz), 16.39 (d, JPC = 10.65 Hz), 64.7
(dd, JPC = 7.29 Hz, JFC = 31.02 Hz), 65.1 (dd, JPC = 6.78 Hz,
128.9 (t, J = 1.68 Hz), 134.1 (d, J = 22.36 Hz), 149.17 (s);
19F NMR (CDCl3): d = –66.67 (d, JPF = 86.9 Hz); HRMS:
m/z calcd for C16H19FNO3PS: 355.0807; found: 355.0789.
(19) Erian, A. W.; Konno, A.; Fuchigami, T. J. Org. Chem. 1995,
60, 7654.
(20) Hou, Y.; Fuchigami, T. J. Electrochem. Soc. 2000, 147,
4567.
J
FC = 22.87 Hz), 106.21 (dd, JPC = 170.11 Hz, JFC = 230.11
(21) Shaaban, M. R.; Ishii, H.; Fuchigami, T. J. Org. Chem. 2000,
65, 8685.
Hz), 126,3 (t, JPC = 3.91 Hz), 126.6 (t, JPC = 3.91 Hz), 127.9
(s), 128.2 (t, J = 1.69 Hz), 129.1 (t, J = 1.68 Hz), 134.5 (d,
J = 22.42 Hz), 149.19 (s);19F NMR (CDCl3): d = –66.28 (d,
(22) Diethyl [Fluoro(4-pyridylthio)methyl]phosphonate (19):
1H NMR (CDCl3): d = 1.37 (t, J = 7.09 Hz, 6 H), 4.24–4.36
(m, 4 H), 6.19 (dd, JHF = 53.6 Hz, JHP = 7.56 Hz, 1 H, CHF),
7.34 (d, J = 1.48 Hz, 1 H), 7.36 (d, J = 1.48 Hz, 1 H), 8.53
(d, J = 1.48 Hz, 1 H), 8.55 (d, J = 1.48 Hz, 1 H); 13C NMR
(CDCl3): d = 16.65 (d, JPC = 6.15 Hz), 64.5 (dd, JPC = 6.70
Hz, JFC = 11.7 Hz), 93.7 (dd, JPC = 177.2 Hz, JFC = 232.5
Hz, CHF), 122.9 (d, JFC = 1.68 Hz), 144.5 (d, JPC = 2.80 Hz),
144.7 (d, JPC = 2.80 Hz), 149.9 (s); 19F NMR (CDCl3): d =
–93.6 (dd, JPF = 83.3 Hz, JHF = 53.6 Hz); HRMS: m/z calcd
for C10H15FNO3PS: 279.0494; found: 279.0489.
(23) Mikolajczyk, M.; Balczewski, P.; Gazejszczak, S. Synthesis
1980, 127.
JPF = 92.2 Hz); HRMS: m/z calcd for C16H19FNO3PS:
355.0807; found: 355.0800.
(18) Diethyl a-Fluoro-a-(4-pyridylthio)benzylphosphonate
(12): 1H NMR (CDCl3): d = 1.13 (t, J = 7.02 Hz, 3 H), 1.29
(t, J = 7.02 Hz, 3 H), 3.86 (q, J = 7.29 Hz, 1 H), 4.01 (q,
J = 7.02 Hz, 1 H), 4.15 (q, J = 6.95 Hz, 2 H), 7.16–7.53 (m,
5 H), 7.57 (d, J = 6.92 Hz, 2 H), 8.34 (d, J = 5.21 Hz, 2 H);
13C NMR (CDCl3): d = 16.30 (d, JPC = 10.62 Hz), 16.38 (d,
J
PC = 10.62 Hz), 64.76 (dd, JPC = 7.25 Hz, JFC = 22.85 Hz),
65.1 (dd, JPC = 6.71 Hz, JFC = 22.31 Hz), 106.1 (dd,
PC = 169.52 Hz, JFC = 229.8 Hz), 126,3 (t, JPC = 3.91 Hz),
J
126.6 (t, JPC = 3.91 Hz), 127.6 (s), 128.1 (t, J = 1.68 Hz),
Synlett 2007, No. 7, 1148–1152 © Thieme Stuttgart · New York

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