gem-Bis(phosphonates): Unexpected Rearrangement of Michael-Type Acceptors
FULL PAPER
propoxide (1.0 , 10 mL) was added under argon to a solution of
compound 5 (160 mg, 0.51 mmol) in anhydrous propanol (5 mL).
The reaction mixture was treated as described for 14. The product
was purified by column chromatography (silica gel) with a mixture
of hexane/EtOAc (9:1) as eluent to afford pure compound 16
(58 mg, 51% yield) as a colorless oil.
J = 14.4, 9.2 Hz, 1 H, 2-Ha), 3.48 (dddd, J = 14.4, 7.1, 3.3, 2.8 Hz,
1 H, 2-Hb), 4.19 (m, 8 H, CH2CH3), 4.74 (dddd, J = 10.5, 9.6, 8.3,
3.3 Hz, 1 H, 1-H), 7.23 (tt, J = 7.5, 1.9 Hz, 1 H, aromatic proton),
7.31 (m, 2 H, aromatic protons), 7.46 (m, 2 H, aromatic protons)
ppm. 13C NMR (CDCl3): δ = 15.99 (t, J = 6.8 Hz, CH3), 16.36 (t,
J = 5.5 Hz, CH3), 36.11 (t, J = 3.8 Hz, C-2), 63.19 (dd, J = 6.8,
5.1 Hz, CH2), 64.27 (dd, J = 37.3, 5.9 Hz, CH2), 71.46 (dd, J =
165.3, 7.6 Hz, C-1), 126.98 (C-6), 129.12 (C-5), 130.69 (C-4), 134.87
(C-3) ppm. 31P NMR (D2O): δ = –4.03 [d, J = 16.6 Hz, O–
P(O)(OEt)2], 15.45 [d, J = 16.6 Hz, C–P(O)(OEt)2] ppm. IR (film):
Diethyl (2-Butoxyethyl)phosphonate (17). Method A: A solution of
compound 4 (179 mg, 0.60 mmol) in anhydrous n-butanol (5 mL)
was treated as described for the preparation of 14. The product
was purified by column chromatography (silica gel) with a mixture
of hexane/EtOAc (9:1) as eluent to afford pure compound 17
ν = 2983, 2931, 1538, 1481, 1440, 1394, 1263, 1164, 792, 746,
˜
534 cm–1. MS: m/z (%) = 427 (2) [M + 1+], 272 (57), 195 (18), 163
1
(25 mg, 30% yield) as a colorless oil. Rf = 0.60 (AcOEt). H NMR
(100), 135 (23), 109 (24).
(CDCl3): δ = 0.92 (t, J = 7.4, Hz, 3 H, 7-H), 1.32 (t, J = 7.0 Hz, 6
H, CH2CH3), 1.35 (sext, J = 7.4 Hz, 2 H, 6-H), 1.55 (m, 2 H, 5-
H), 2.10 (dt, J = 18.7, 7.5 Hz, 2 H, 1-H), 3.43 (t, J = 6.7 Hz, 2 H,
4-H), 3.67 (dt, J = 11.6, 7.5 Hz, 2 H, 2-H), 4.10 (m, 4 H, CH2CH3)
ppm. 13C NMR (CDCl3): δ = 13.74 (C-7), 16.29 (d, J = 6.1 Hz,
CH2CH3), 19.17 (C-6), 26.99 (d, J = 139.4 Hz, C-1), 31.61 (C-5),
61.46 (d, J = 6.1 Hz, CH2CH3), 64.44 (C-2), 70.64 (C-4) ppm. 31P
NMR (CDCl3): δ = 26.26 ppm. MS: m/z (%) = 239 (6) [M + 1]+,
195 (11), 181(100), 166 (55), 138 (70), 109 (85). Method B: A solu-
tion of sodium n-butoxide (1.0 m, 10 mL) was added under argon
to a solution of compound 5 (120 mg, 0.38 mmol) in anhydrous
butanol (5 mL). The reaction mixture was treated as described for
14. The product was purified by column chromatography (silica
gel) with a mixture of hexane/EtOAc (9:1) as eluent to afford pure
compound 17 (61 mg, 61% yield) as a colorless oil.
Supporting Information (see footnote on the first page of this arti-
cle): 1H NMR, 13C NMR, and 31P NMR spectra and mass spectra
for all compounds described in this work. DEPT spectra, 1H-1H
1
COSY spectra, and H-13C 2D correlation spectra for compounds
1
8 and 19; H-31P HMBC for compound 8.
Acknowledgments
We thank the Fundación Antorchas, the National Research Coun-
cil of Argentina (grant PIP635/98), and the Universidad de Buenos
Aires (grant X-252) for financial support. We would like to thank
one of the reviewers for very helpful suggestions.
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Diethyl
[1-(Diethoxyphosphoryl)-2-thiocyanatoethyl]phosphonate
(18): Potassium thiocyanate (22 mg, 0.22 mmol) was added to a
solution of tetraethyl ethane-1,1-diylbis(phosphonate) (4; 50 mg,
0.16 mmol) in water (2 mL). The reaction mixture was stirred at
room temperature for 24 h. The mixture was extracted with dichlo-
romethane (3×5 mL), the combined organic layers were washed
with water (5 mL) and dried (MgSO4), and the solvent was evapo-
rated. The residue was purified by column chromatography (silica
gel) with a mixture of hexane/EtOAc (7:3) as eluent to afford pure
compound 18 (43 mg, 72% yield) as a colorless oil. Rf = 0.1
(EtOAc/MeOH, 97:3). 1H NMR (CDCl3): δ = 1.35 (t, J = 7 Hz, 12
H, CH2CH3), 2.61 (tt, J = 23.2, 5.5 Hz, 1 H, 1-H), 4.08 (dt, J =
17.1, 5.5 Hz, 2 H, 2-H), 4.18 (m, 8 H, CH2CH3) ppm. 13C NMR
(CDCl3): δ = 16.30 (d, J = 6.8 Hz, CH2CH3), 40.47 (d, J =
131.8 Hz, C-1), 58.59 (t, J = 5.1 Hz, C-2) 62.73 (d, J = 6.8 Hz,
CH2CH3), 63.03 (d, J = 6.8 Hz, CH2CH3), 149.03 (C-3) ppm. 31P
NMR (D O): δ = 19.10 ppm. IR (film): ν = 2986, 2357, 1662, 1392,
˜
2
1242, 1026, 976, 856, 802; 679 cm–1. MS: m/z (%) = 333 (1) [M]+,
319 (2), 301(6), 288 (12), 261 (20), 195 (45), 181 (100), 171 (43),
163 (58), 125 (43), 109 (73), 81 (65), 65 (72).
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Diethyl [1-(Diethoxyphosphoryloxy)-2-(phenylsulfanyl)ethyl]phos-
phonate (19): Potassium hydroxide (530 mg, 9.5 mmol) was added
to a solution of thiophenol (1.04 g, 9.5 mmol) in water (5 mL). The
mixture was stirred at room temperature for 5 min, tetraethyl oxir-
ane-2,2-diylbis(phosphonate) (300 mg, 0.94 mmol) was then added,
and the reaction mixture was stirred at room temperature for
30 min. The mixture was extracted with ethyl acetate (2×10 mL).
The combined organic layers were washed with a saturated aqueous
solution of sodium chloride (2×10 mL) and dried (MgSO4), and
the solvent was evaporated. The residue was purified by column
chromatography (silica gel) with a mixture of hexane/EtOAc (7:3)
as eluent to yield pure compound 19 (123 mg, 30% yield) as a col-
1
orless oil. Rf = 0.66 (EtOAc/iPrOH, 9:1). H NMR (CDCl3): δ =
1.328 (t, J = 7.1 Hz, 6 H, CH2CH3), 1.329 (dt, J = 7.1, 1.2 Hz, 3
H, CH2CH3), 1.335 (dt, J = 7.1, 1.2 Hz, 3 H, CH2CH3), 3.27 (dt,
Eur. J. Org. Chem. 2005, 3687–3696
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