Michael Addition of Dialkylphosphites to Methylvinylketone 229
(J = 146.1 Hz, PCH2), 40.6 (J = 5.0 Hz, C2)*, 41.2
(J = 0.9 Hz, C4)*, 62.1 (J = 7.0 Hz, OCH2CH3), 62.2
(J = 6.9 Hz, OCH2CH3), 209.1 (J = 16.5 Hz, C(O))
(*: may be reserved); δlit [15] 16.4 (J = 5.3 Hz), 24.3
(J = 4.6 Hz), 25.9 (J = 19.1 Hz), 35.8 (J = 145.7 Hz),
40.5 (J = 5.3 Hz), 41.0 (J = 2.0 Hz), 61.8 (J = 4.0 Hz),
61.9 (J = 4.0 Hz), 208.8 (J = 16.5 Hz).
ing bath was removed and the mixture was stirred for
20 h. Then the mixture was hydrolyzed with 20 mL
of 5% HCl and the organic phase was separated
and dried. The crude product was passed through
a small layer of silica gel applying 3% methanol in
chloroform to furnish 0.74 g of a 22:78 mixture of
bis-adduct 5 (31P NMR (CDCl3): δ1 26.5 and δ2 33.0,
(M + H)+ = 347) and hydroxyphosphonate 6 (∼65%,
31P NMR (CDCl3): δ 24.0, (M + H)+ = 209).
Diethyl-2-hydroxy-2-butylphosphonate 4 was Pre-
pared from Ethylmethylketone and Diethylphosphite
by the Method Shown Above Applying a Reaction
Time of 6 h. Yield: 0.12 g (15%); 31P NMR (CDCl3):
δ 27.8; 13C NMR (CDCl3): δ 7.1 (J = 8.2 Hz, CH2CH3),
16.7 (J = 5.5 Hz, OCH2CH3), 21.4 (J = 4.4 Hz,
C(OH)CH3), 30.1 (J = 4.4 Hz, C(OH)CH2), 62.9
(J = 7.0 Hz, OCH2CH3), 72.1 (J = 161.0 Hz, PC).
Using triethylaluminum/hexane instead of
trimethylaluminum/hexane, a 48:19:33 mixture of
1b, 5, and 6 was obtained.
Microwave Synthesis of 3-Oxobutyl-diphenylphos-
phine Oxide 2
A mixture of 0.11 mL (1.42 mmol) of methylvinylke-
tone and 0.10 g (1.42 mmol) of diphenylphosphine
oxide is heated at 95◦C under N2 atmosphere in
a CEM Discovery microwave reactor (applying ca.
50 W) for 1 h. The crude product was purified by
column chromatography (silica gel, 3% methanol in
chloroform) to give 0.15 g (75%) 3-oxobutyl deriva-
tive 2 (31P NMR (CDCl3): δ 32.3).
Alternative Methods for the Synthesis
of Diethyl-3-oxobutylphosphonate 1b
Under Phase-Transfer Catalytic Conditions.
To the solution of 0.35 mL (4.29 mmol) of
methylvinylketone, 0.55 mL (4.29 mmol) of di-
ethylphosphite, and 0.10 g (0.44 mmol) of TEBAC
in 10 mL of dichloromethane, 1.71 g (43.0 mmol)
of sodium hydroxide in 5.7 mL of water was added
dropwise. After a reflux of 3 h, the phases were
separated and the aqueous phase was washed with
chloroform. The combined organic phase was dried
and the crude product obtained after evaporation
was purified by column chromatography (silica gel,
3% methanol in chloroform) to give 0.51 g (57%)
3-oxobutyl derivative 1b (31P NMR (CDCl3): δ 31.4).
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In the Presence of DBU. A solution of 0.12 mL
(1.43 mmol) of methylvinylketone, 0.18 mL
(1.43 mmol) of diethylphosphite, and 0.05 mL
(0.72 mmol) of DBU in 2 mL of chloroform was
stirred at the boiling point for 3 h. Then the mixture
was washed with 5 mL of 5% HCl, the organic phase
was dried and the crude product was obtained
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derivative 1b (∼66%, 31P NMR (CDCl3): δ 31.3) and
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Heteroatom Chemistry DOI 10.1002/hc