Mendeleev Commun., 2010, 20, 145–147
Ph2POEt ([hmim]Br, room temperature). After work-up, 2,3-
by the Arbuzov reaction of trimethylphosphite with dimethyl
(3-bromoprop-1-en-2-yl)phosphonate [110 °C, (MeO)3P as a
solvent, compound 7].8 Note that the above-mentioned ruthenium
catalyzed reaction was supposed to proceed via Ph2P(O)H addition
bis(diphenylphosphoryl)prop-1-ene 1b was isolated in 30% yield
as an off-white solid while the yield of its analogue 1a was only
12% (>90% purity) after distillation.‡ However, in both cases
the structures of propenes 1a,b were unambiguously confirmed
by the multinuclear NMR spectra. The compounds demonstrated
two doublets in the 31P NMR spectra (AB-system) at 17.55 and
either to the intermediate terminal acetylene Ph2P(O)CH(Ar)C
ºCH
or to the product of its acetylene-allene rearrangement.6
Ar
O
O
3
25.31 ppm with the coupling constant JPP 32.0 Hz (for 1a)
PPh2
P(Ph)But
3
and at 30.79 and 32.80 ppm with JPP 22.1 Hz (for 1b) and the
Ph2P
O
Ph2P
O
corresponding sets of signals in the 1H and 13C NMR spectra.
Previously, the products of the similar structure were obtained
via double phosphorylation of α-aryl substituted propargylic
alcohols with diphenylphosphine oxide catalyzed by thiolate-
bridged diruthenium complex [Cp*RuCl(μ2-SMe)2-RuCp*Cl,
(Cp* = 5-C5Me5)]6 (60 °C, 18 h, compound 5), by thermal
induced tert-butylphenylphosphine addition to (allenyl)diphenyl-
phosphine oxide in refluxing toluene (48 h, compound 6)7 or
CH2
CH2
5
6
O
P(OMe)2
(MeO)2P
O
CH2
7
Taking into account the formation of the corresponding
hydrophosphoryl compound from starting PIII-esters, i.e., diethyl-
phosphite or diphenylphosphinous acid in ILs in the case of
inactive alkyl and aryl halides, we suggested that formation
of products 1a,b can be attributed to the general reaction
scheme similar to those for metal-catalyzed or thermally induced
processes mentioned in refs. 6, 7. In other words, the reaction
of phosphite or phosphinite with propargyl bromide in ILs
according to Scheme 3 could initially result in the Arbuzov-
type products 2a,b with terminal triple bonds which may undergo
further acetylene-allene rearrangement to afford allenes 3a,b.
The subsequent addition of the corresponding hydrophosphoryl
compounds, formed under reaction conditions, to either of these
intermediates could produce the final bisphosphorylated propenes
1a,b. At that, ionic liquid could activate all steps of the process.
To verify this supposition, we performed the reactions of Ph2P(O)H
with either of Ph2P(O)CH2CºCH and Ph2P(O)CH=C=CH2 in ILs.
However, these test experiments revealed that Ph2P(O)H did not
add to either of these compounds in [hmim][Br] or [bmim][NTf2]
even at prolonged reaction times. That means that the above
reactions proceed via different reaction pathway.
To elucidate it, the reaction of ethyl diphenylphosphinite
with propargyl bromide was performed in [bmim][BF4] capable
of stabilizing the intermediate phosphonium salts due to the
presence of non-nucleophilic anion.3 Under these conditions,
the 31P NMR spectra of the reaction mixture comprised two
doublets at 44.9 and 61.8 ppm with the coupling constant equal
to 73 Hz which slowly transformed into the signals of the final
product 1b (dP1 30.79 ppm, dP2 32.80 ppm, 3JPP 22.1 Hz). These
data allow us to suggest that the above reaction involves the
first attack of a phosphorus lone pair of diphenylphosphinite on
the electrophilic carbon atom in propargyl bromide to form an
intermediate salt A which can rearrange to the corresponding
allenic intermediate B. The further addition of the second molecule
of Ph2POEt either to A or to B salts results in formation of the
31P NMR detected intermediate C bearing phosphonuim and
ylidic phosphorus atoms. In time, the intermediate C transforms
into the final product 1b by dealkylation and hydrolysis of
ethoxy groups at phosphonium and ylidic phosphorus atoms,
respectively (Scheme 4).
CH2
[hmim]Br
R2POEt +
BrCH2C CH
R2P(O)CH2
1a,b
room
temperature
P(O)R2
R2P(O)CH2C CH
R2P(O)CH=C=CH2
2a,b
3a,b
a R = OEt
b R = Ph
R2P(O)
C
C Me
4a,b
Scheme 3
‡
NMR spectra were recorded on a Bruker Avance-400 spectrometer
and the chemical shifts (d) were internally referenced by the residual solvent
signals relative to TMS (1H and 13C) or externally to H3PO4 (31P).
Diphenyl-1-propynylphosphine oxide9 and diphenyl(1,2-propadienyl)-
phosphine oxide10 were obtained according to the published procedures.
2,3-Bis(diethoxyphosphoryl)prop-1-ene 1a. Triethylphosphite (0.02 mol)
was added to a solution of propargyl bromide (0.011 mol) in [bmim]NTf2
(5 g) at room temperature followed by stirring of the final mixture for
3 days. Then the reaction mixture was extracted with Et2O (3×20 ml),
the solvent was evaporated under reduced pressure and the residue was
distilled in a vacuum to give 0.4 g (12%) of bisphosphorylated propene
1a with 90% purity according to the spectral data. Bp 170–190 °C (20 Torr),
31P NMR (162 MHz, CDCl3): AB-system, 17.55 [P(1)], 25.31 [P(2),
3JPP 32 Hz]. H NMR (400 MHz, CDCl3) d: 1.28–1.33 (m, 12H, Me),
2.75 [dd, 2H, CH2P(1), JP(1)H 21.4 Hz, JP(2)H 12.3 Hz], 4.05–4.14 (m,
8H, OCH2), 6.24 (dd, 1H, HA, 3JP(2)H 21.8 Hz, 4JP(1)H 4.9 Hz), 6.25 (dd,
1H, HB, 3JP(2)H 47.4 Hz, 4JP(1)H 3.7 Hz).
2,3-Bis(diphenylphosphoryl)prop-1-ene 1b. Ethyl diphenylphosphinite
(2 mmol) was added to a solution of propargyl bromide (1 mmol) in
[hmim]Br (0.5 g) at room temperature. After stirring (for 3.5 h, 69% of
1b; 3 days, 78% of 1b) water (1 ml) was added to the reaction mixture
and this solution was extracted with CH2Cl2 (3×10 ml). The combined
extracts were dried over Na2SO4. After evaporation of the solvent under
reduced pressure, the residue was separated by column chromatography
(SiO2, CH2Cl2–methanol, 100:2) to afford propene 1b as off-white solid.
Yield 30%, mp 142 °C. 31P NMR (162 MHz, CDCl3): AB-system, 30.79
1
2
3
3
1
[P(1)], 32.80 [P(2), JPP 22.1 Hz]. H NMR (400 MHz, CDCl3) d: 3.41
2
3
[dd, 2H, CH2P(1), JP(1)H 13.0 Hz, JP(2)H 8.3 Hz], 5.52 (dd, 1H, HA,
3JP(2)H 21.0 Hz, 4JP(1)H 3.0 Hz), 6.77 (dd, 1H, HB, 3JP(2)H 43.2 Hz, 4JP(1)H
2.3 Hz), 7.38–7.56, 7.72–7.79 (m, 20H, 4Ph). 13C NMR (101 MHz,
CDCl3) d: 29.63 (dd, 1JP(1)C 67.0 Hz, 2JP(2)C 9.9 Hz), 128.60 (d, meta-C
In conclusion, we have found that imidazolium ionic liquids
as a reaction medium change the reaction course of phos-
phorus(III) acid esters with primary alkyl halides, aryl halides
and propargyl bromide affording in hydrophosphoryl compounds,
the products of oxidation of the starting phosphorus substrate,
and 2,3-bis(phosphoryl)prop-1-enes, respectively, instead of the
typical Arbuzov products. The procedure for the synthesis of
2,3-bis(phosphoryl)prop-1-enes in ionic liquids is advantageous
over other known methods.
3
1
in Ph, JPC 11.5 Hz), 129.09 (d, ipso-C in Ph, JP(1)C 81.1 Hz), 130.97
2
(d, ortho-C in Ph, JP(1)C 9.9 Hz), 131.83 (s, para-C in Ph), 131.96 (d,
ortho-C in Ph, 2JP(2)C 9.3 Hz), 132.15 (s, para-C in Ph), 132.59 (d, ipso-C
in Ph, 1JP(2)C 81.5 Hz), 134.33 (appar. t, =CH2, JP(2)C = 3JP(1)C = 8.0 Hz),
2
134.72 (dd, C=, 1JP(2)C 51.6 Hz, 2JP(1)C 7.4 Hz). IR (KBr, n/cm–1): 3055
(C=CH2), 1198, 1174 (P=O). Found (%): C, 72.28; H, 5.27; P, 13.46.
Calc. for C27H24O2P2·0.1CH2Cl2 (%): C, 72.28; H, 5.41; P, 13.76.
– 146 –