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B. Zagipa et al. / Journal of Fluorine Chemistry 127 (2006) 552–557
Scheme 5.
3.3. Electrolytic procedures for fluorination
CHF), 6.87–7.62 (m, 4H, C6H4); 13C NMR 16.49 (dd,
3
5JFC = 8.88 Hz, JPC = 6.01 Hz, CH3CH2O), 55.68 (s, OCH3),
4
63.35 (dd, JFC = 14.50 Hz, JPC = 7.25 Hz, CH3CH2O), 83.37
2
A typical procedure is as follows. Anodic oxidation of 1
(0.5 mmol) was carried out in an undivided cell equipped with
platinum plate electrodes (2 cm ꢀ 2 cm) in 5 ml of 1 M Et4NF-
3HF/dimethoxyethane (DME) at room temperature. Constant
current (2.5 mA/cm2) was passed until the starting material 1
was almost consumed (checked by TLC). After electrolysis, the
electrolytic solution was passed through a short column filled
with silica gel using ethyl acetate 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 ethyl acetate to give pure
fluorinated products. The products were identified by spectro-
scopic data.
1
(dd, JPC = 173.50 Hz, JFC = 177.9 Hz, CHF), 110.52 (d,
1
2
5JFC = 1.71 Hz, C6H4), 115.25 (d, JFC = 20.67 Hz, C6H4),
120.72 (s, C6H4), 123.90 (d, 3JFC = 3.32 Hz, C6H4), 128.58 (d,
3
4JFC = 6.60 Hz, C6H4), 129.86 (d, JFC = 7.79 Hz, C6H4); 19F
NMR d 125.59 (dd, 2JPF = 44.20 Hz, 2JFH = 90.69 Hz); MS: 276
(63), 245 (30), 139 (100), 121 (26), 109 (60) and 91 (75); HRMS
m/z Calcd. for C12H18FO4P 276.0927 and found: 276.0933.
1
Diethyl a,a-difluoro-3-methoxybenzylphosphonate (3b). H
3
NMR d 1.32 (t, JHH = 7.02 Hz, 6H, CH3CH2O), 3.87 (s,
OCH3), 4.15–4.29 (m, 4H, CH3CH2O), 6.96–7.53 (m, C6H4);
3
13C NMR 16.44 (d, JPC = 5.56 Hz, CH3CH2O), 55.93 (s,
OCH3), 64.52 (d, 2JPC = 6.71 Hz, CH3CH2O), 112.13 (s, CF2),
2
115.23 (d, JFC = 20.67 Hz, C6H4), 120.28 (s), 123.87 (d,
Diethyl a-fluoro-4-methoxybenzylphosphonate (1a) [14],
diethyl a,a-difluoro-4-methoxybenzylphosphonate (1b) [19],
diethyl a,a-difluoro-2-methoxybenzylphosphonate (2b) [19],
diethyl a-fluorobenzylphosphonate (4a) [14], and diethyl a,a-
difluoro-4-iodobenzylphosphonate (5b) [20] were identified by
spectroscopic data in the references.
3JFC = 3.30 Hz), 128.06 (s), 129.83 (d, 4JFC = 7.25 Hz), 152.82
3
2
(d, JFC = 16.5 Hz); 19F NMR d-27.99 (d, JPF = 116.61 Hz);
MS: 294 (69), 263 (1), 157 (88), 127 (14), 109 (100); HRMS m/
z Calcd. for C12H17F2O4P 294.0830 and found: 294.0822.
Diethyl a-fluoro-4-iodobenzylphosphonate (5a). Yellow oil;
1H NMR (CDCl3) d 7.74 (d, J = 8.08 Hz, 2H), 7.21 (d,
J = 8.08 Hz, 2H), 5.63 (dd, JFH = 44.82 Hz, JPH = 8.10 Hz, 1H,
CHF), 4.16–4.05 (m, 4H, 2 ꢀ MeCH2O), 1.30 (t, J = 6.48 Hz,
3H, CH3CH2O), 1.27 (t, J = 6.48 Hz, 3H, CH3CH2O); 13C
NMR (CDCl3) 137.5 (t, JPC = JFC = 2.24 Hz), 132.6 (d,
Diethyl a fluoro-2-methoxybenzylphosphonate (2a). 1H
3
NMR d 1.24 (t, CH3CH2O, JHH = 7.02 Hz, 3H), 1.32 (t,
3
CH3CH2O, JHH = 7.02 Hz, 3H), 3.85 (s, OCH3, 3H,), 3.88–
4.21 (m, CH3CH2O, 4H), 6.23 (dd, CHF, 2JPH = 7.29, 44.01 Hz,
1H), 6.88–7.62 (m, C6H4); 13C NMR 16.44 (dd, CH3CH2O,
5JFC = 8.90, 6.10 Hz,), 55.63 (s, OCH3), 63.29 (dd, CH3CH2O,
2JPC = 6.70 Hz, 4JFC = 14.50 Hz), 83.31 (dd, 1JPC = 174.04 Hz,
1JFC = 179.05 Hz), 110.46 (d, C6H4, 4JFC = 1.08 Hz), 119.63 (s,
JFC = 18.90 Hz), 128.2 (t, JPC = JFC = 6.71 Hz), 95.0, 88.9
(dd, JPC = 169.0 Hz, JFC = 184.1 Hz, CHF), 63.7 (dd,
J
J
J
PC = 6.64 Hz, JFC = 27.90 Hz, CH3CH2O), 16.5 (d,
PC = 5.56 Hz, CH3CH2O); 19F NMR (CDCl3) d-125.39 (dd,
PF = 83.15 Hz, JHF = 44.45 Hz); MS, m/z (%), 372 (M+, 20),
5
C6H4), 120.66 (d, C6H4, JFC = 1.15 Hz), 128.47 (d, C6H4,
4
2JPC = 4.47 Hz), 128.59 (d, C6H4, JFC = 3.93 Hz), 130.43 (d,
3
2
C6H4, JFC = 4.51 Hz); 19F NMR d-124.01 (dd, JPF
=
245 (33), 235 (59), 109 (100) and 81 (65); HRMS, m/z Calcd.
for C11H15FIO3P 371.9788 and found: 371.9772.
2
46.23 Hz, JFH = 44.20 Hz); MS: 276 (9), 139 (59), 121
(14), 109 (23) and 91(100); HRMS m/z Calcd. for C12H18FO4P
276.0927 and found: 276.0934.
4. Conclusions
Diethyl a-fluoro-3-methoxybenzylphosphonate (3a). 1H
3
NMR d 1.23 (t, JHH = 7.02 Hz, 3H, CH3CH2O), 1.32 (t,
Anodic fluorination reaction of o-, m- and p-methoxyben-
zylphosphonates resulted in the formation of a-fluoro- and/or
a,a-difluoro-methoxybenzylphosphonates in moderate to good
3JHH = 7.02 Hz, 3H, CH3CH2O), 3.85 (s, OCH3), 4.08–4.19 (m,
4H, CH3CH2O), 6.23 (dd, 2JPH = 7.29 Hz, 2JFH = 44.01 Hz, 1H,