PAPER
A New and Efficient Electrosynthesis of 2-Substituted 1,1-Cylopropanediylbis-(phosphonates)
1905
75.4 MHz for carbon, 121.5 MHz for phosphorus; chemical shifts
(d) are expressed in ppm relative to TMS for 1H and 13C nuclei, and
to H3PO4 for 31P nucleus; coupling constants (J) are given in Hertz;
coupling multiplicities are reported using conventional abbrevia-
tions. Starting phosphonate 1 was prepared according to Ref. 19.
cerned by the bielectronic electrochemical reduction of
8a, which led to 4a, after ring closure (path B2). Such a
phenomenon was not observed with other Michael accep-
tors.
In conclusion, we have developed a new and efficient syn-
thesis of 2-subtituted cyclopropanediyl bis(phosphonates)
from the readily available tetraethyl dichloromethyl-
bis(phosphonate) by the electrosynthetic way. This meth-
od avoids the use of sophisticated bases such as thallium
ethoxide. The yields are similar to the ones previously ob-
tained by chemical procedures.
Electrosynthesis of 2-Substituted 1,1-Cyclopropanediyl(bis)-
phosphonates 4; General Procedure
In a purged two-compartments cell, equipped with a carbon felt
cathode (S = 20 cm2) and a platinium wire anode, a solution of 1
(2.15g, 6 mmol) and the Michael acceptor 3 (12 mmol) in MeCN
(50 mL) containing Et4NBr (0.1 mol.L–1) was introduced in the ca-
thodic chamber. MeCN containing Et4NBr (0.4 mol.L–1) was intro-
duced in the anodic chamber as well as cyclohexene (2 mL) just
before the begining of the electrolysis. A 150 mA constant current
was applied. The complete formation of phosphonate 4 was
achieved after 2 h 15 min (2 F.mol–1 of 1). The reaction mixture was
evaporated in vacuo. The residue was washed with THF (30 mL)
and Et4NBr was separated by filtration. The organic layer was evap-
orated in vacuo to give 4. Further purification by bulb-to-bulb dis-
tillation led to pure 4a–e, whose structures were etablished by NMR
and mass spectroscopy (Table 2).
Reagents and solvents were purchased from commercial suppliers.
MeCN was distilled over CaH2 and kept on 4 Å molecular sieves
under argon. Et4NBr was purified by crystallization (EtOH/Et2O)
and dried at 120 °C under vaccum for 5 h. Cathodes, purchased
from Le Carbone Lorraine, are carbon felt plates (50 mm × 40 mm,
depth: 5 mm, specific area: 0.3 m2.g–1). TLC was performed on
Merck 60 F-254 silica gel plates. Mass spectra under electronic im-
pact at 70 eV (m/z and relative abundance in % are given) were ob-
tained with a GC-MS Hewlett Packard 5970 mass selective
detector. HRMS measurements under chemical ionisation were per-
formed on a Jeol AX 500 spectrometer. NMR spectra were recorded
on a Bruker AC 300 spectrometer operating at 300 MHz for proton,
Separation and Characterization of Compound 8a
When methyl acrylate (3d) was used as Michael acceptor, stopping
the electrolysis after the complete disappearance of 1 led to the
crude mixture containing 4a, 5, 6 and 8a in the ratio 63:7:3:27, re-
Table 2 1H and 13C NMR and MS Data of Compounds 4
Product
1H NMR (CDCl3 / TMS)
13 C{1H} NMR (CDCl3 / TMS)
MS (70 eV)
δ, J (Hz)
δ, J (Hz)
m/ z (%)
4a
1.35 (m, 12 H, 2 × [CH3-CH2O]2P), 1.65
(m, 1 H, CH2-cycle), 1.85 (m, 1 H, CH2-
cycle), 2.6 (m, 1 H, CHCO2CH3), 4.2
(m, 8 H, 2 × [CH3CH2O]2P)
14.4 (t, 2JC,P = 3.9, C-3), 16 (2 d, 2JC,P
=
372 (M+, 82), 341(37), 327 (25), 313
(77), 299 (32), 285 (45), 243 (55), 235
(100), 177 (40), 152 (35), 121 (20), 99
(23), 84 (20), 65 (25)
3, [CH3CH2O]2P), 17.8 (dd, 1JC,P
=
175.8, 175.6, C-1), 26 (t, 2JC,P = 3.5, C-
2), 52.1 (s, CO2CH3), 62.7 (4 d, 2JC,P
=
6.5, [CH3CH2O]2P), 168 (dd, 3JC,P
7.4, 5.2, CO2CH3)
=
4b
4c
1.4 (m, 12 H, 2 × [CH3CH2O]2P), 1.8
(m, 1 H, CH2-cycle), 2 (m, 1 H, CH2-cy-
cle), 2.2 (m, 1 H, CHCN), 4.2 (m, 8 H, 2
× [CH3CH2O]2P)
8.3 (d, 2JC,P = 5, C-3), 15.8 (2 d, 2JC,P
=
339 (M+, 57), 327 (38), 311 (54), 285
(27), 241 (44), 231 (100), 173 (28),
147 (58), 117 (17), 99 (28), 84 (17), 65
(31)
3, [CH3CH2O]2P + C-2), 16.6 (dd, 1JC,P
= 168.5, 168.3, C-1), 62.7 (4 d, 2JC,P
6.5, [CH3CH2O]2P), 116.3 (dd, 3JC,P
10.6, 5.1, CN)
=
=
1.3 (m, 12 H, 2 × [CH3CH2O]2P), 1.5
(m, 1 H, CH2-cycle), 1.9 (m, 1 H, CH2-
cycle), 2.2 (s, 3 H, COCH3), 2.6 (m, 1 H,
CHC)
15.0 (t, 2JC,P = 4, C-3), 16.6 (2 d, 2JC,P
=
356 (M+, 8), 341 (42), 314 (100), 299
(11), 285 (23), 257 (20), 229 (29), 219
(18), 177 (30), 147 (?)
3, [CH3CH2O]2P + C-2), 20.2 (dd, 1JC,P
= 169.1, 177.8, C-1), 31.0 (s, COCH3),
33.2 (t, 2JC,P = 3.4, C-3), 63.3 (4 d, 2JC,P
= 6.5, [CH3CH2O]2P), 202 (dd, 3JC,P
5.4, 3.7 COCH3)
=
4d
4e
1.3 (m, 12 H, 2 × [CH3CH2O]2P), 1.55
(m, 1 H, CH2-cycle); 1.6 (s, CH3), 1.85
(ddd, 1 H, 3JH,P(cis) = 17.8, 3JH,P(trans)
= 12.9, 2JH,H = 4.7, CH2-cycle);3.6 (s, 3
H, CO2CH3), 4.2 (m, 8 H, 2 ×
16.5 (2 d, 2JC,P = 3, [CH3CH2O]2P),
386 (M+, 6), 355 (4), 322 (5), 301 (4),
288 (52), 261 (57), 243 (25), 233 (40),
215 (19), 205 (26), 187 (21), 177 (30),
159 (78), 152 (100), 125 (46), 108
(13), 97 (22), 79 (18), 65 (27)
18.4 (dd, 3JC,P = 4.5, 2.6, CH3), 21.4 (t,
3JC,P = 4.3, C-3), 22.5 (dd, 1JC,P
=
168.1, 168.3, C-1), 34.8 (t, 3JC,P = 4.3,
C-2), 52.7 (s, CO2CH3), 62.8 (4 d, 2JCP
[CH3CH2O]2P)
= 6.5, [CH3CH2O]2P), 172 (dd, 3JC,P
7.5, 5.4, CO2CH3)
=
1.3 (m, 12 H, 2 × [CH3CH2O]2P), 1.7
(ddd, 1 H, 3JH,P(trans) = 18, 3JH,P(cis) =
13.3, 2JH,H = 4.9, CH2-cycle); 1.8 (s, 3 H,
CH3), 2.0 (ddd, 1 H, 3JH,P(trans) = 18,
3JH,P(cis) = 13.3, 2JH,H = 4.9, 1 H, CH2-
cycle), 4.2 (m, 8 H, 2 × [CH3CH2O]2P)
16.5 (2 d, 2JC,P = 3,
353 (M+, 58), 338 (9), 322 (24), 301
(53), 273 (29), 261 (100), 245 (23),
233 (79), 224 (42), 216 (78), 205 (50),
189 (36), 171 (51), 161 (44), 152 (18),
124 (14), 109 (22), 99 (30), 81 (28), 65
(35)
[CH3CH2O]2P),17.6 (dd, 3JC,P = 5.2,
0.7, C-2), 19.8 (dd, 3JC,P = 3.1, 1.8,
CH3), 23.5 (t, 3JC,P = 4.3, C-3), 24.4
(dd, 1JC,P = 165.8, 165.9, C-1), 64.2 (4
d, 2JC,P = 6.5, [CH3CH2O]2P), 120.5
(dd, 3JC,P = 8, 5.2, CN)
Synthesis 1999, No. 11, 1903–1906 ISSN 0039-7881 © Thieme Stuttgart · New York