Selective reduction of allenyl(diphenyl)phosphine oxides to allyl(diphenyl)phosphine oxides

Article abstract of DOI:10.1134/S1070428017070065

The reduction of allenyl(diphenyl)phosphine oxides with HSiCl₃ or LiAlH₄ selectively afforded the corresponding allyl(diphenyl)phosphine oxides. 3-Methylbut-2-en-1-yl(diphenyl)phosphine oxide reacted with AlCl₃ to give a m

Full text of DOI:10.1134/S1070428017070065

ISSN 1070-4280, Russian Journal of Organic Chemistry, 2017, Vol. 53, No. 7, pp. 995–998. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © S.V. Lozovskiy, M.I. Aleksandrova, A.V. Vasilyev, 2017, published in Zhurnal Organicheskoi Khimii, 2017, Vol. 53, No. 7,
pp. 984–987.
Selective Reduction of Allenyl(diphenyl)phosphine Oxides
to Allyl(diphenyl)phosphine Oxides
S. V. Lozovskiya, M. I. Aleksandrovaa, and A. V. Vasilyeva, b*
a St. Petersburg State University, Universitetskii pr. 26, St. Petersburg, 198504 Russia
b St. Petersburg Forest Technical University, Institutskii per. 5, St. Petersburg, 194021 Russia
*e-mail: aleksvasil@mail.ru
Received June 2, 2017
Abstract—The reduction of allenyl(diphenyl)phosphine oxides with HSiCl3 or LiAlH4 selectively afforded the
corresponding allyl(diphenyl)phosphine oxides. 3-Methylbut-2-en-1-yl(diphenyl)phosphine oxide reacted with
AlCl3 to give a mixture of 4,4-dimethyl-1-phenyl-1,2,3,4-tetrahydro-λ5-phosphinoline 1-oxide and 4,4-di-
methyl-1-phenyl-1,4-dihydro-λ5-phosphinoline 1-oxide.
DOI: 10.1134/S1070428017070065
Allenes are very important reagents for organic
synthesis. Allene fragment is present in molecules of
many natural and biologically active compounds [1–7].
Allenyl(diphenyl)phosphine oxides (diphenylphos-
phorylallenes) are used to obtain phosphorus-con-
taining heterocycles, carbocycles, and unsaturated
alcohols [8–12].
tion of 1a to 2a by the action of HSiCl3 afforded good
yields in benzene or 1,2-dichloroethane (run nos. 1, 2).
No reduction occurred at lower temperature (e.g., in
boiling chloroform; run no. 3). Apart from HSiCl3,
allene 1a can be converted to 2a with the use of
an equimolar amount of LiAlH4 in diethyl ether (run
no. 4), whereas lower yield of 2a was obtained when
the amount of LiAlH4 was diminished to 0.5 or
0.25 equiv. No reaction occurred with NaBH4 as
reducing agent (run nos. 5, 6).
Herein we report the reduction of allenyl(diphenyl)-
phosphine oxides 1a–1e with various reducing agents,
in particular HSiCl3, LiAlH4, NaBH4, and H2–Pd/C.
The reduction of allene 1b with HSiCl3 or LiAlH4
gave compound 2b in a good yield (Scheme 1), and
the reaction rate was appreciably higher (reaction time
4–5 h) than in the reduction of 1a (24 h; see table).
Allene substrates 1c–1e under analogous conditions
(reduction with HSiCl3 or LiAlH4) gave rise to com-
plex mixtures of oligomeric products with a molecular
weight of 400 to 1000 Da (according to the MS data).
Trichlorosilane HSiCl3 is frequently used for the
reduction of phosphine oxides to phosphines [12–14].
However, heating of allene 1a with excess HSiCl3 in
benzene for 24 h in a glass high-pressure reactor
resulted in the reduction of the double bond nearest to
the phosphoryl group with formation of allyl(diphenyl)-
phosphine oxide 2a in 94% yield (see table, run no. 1),
whereas the P=O bond remained intact. Unlike stan-
dard procedure for the reduction with HSiCl3 [13, 14],
addition of 1 equiv of a base (triethylamine or pyri-
dine) considerably impaired the yield of 2a.
The hydrogenation of 1a over carbon-supported
palladium (Pd/C) at room temperature (atmospheric
hydrogen pressure; 24 h) led to the formation of
compound 3 as a result of exhaustive reduction of the
hydrocarbon fragment (yield 95%; Scheme 2).
The results of reduction of allene 1a with different
reducing agents are collected in table. The transforma-
Ph
Me
·
P(O)Ph2
·
P(O)Ph2
·
P(O)Ph2
·
P(O)Ph2
Ph
·
P(O)Ph2
H2C
Me
Ph
1a
1b
1c
1d
1e
995

LOZOVSKIY et al.
996
Scheme 1.
HSiCl3, benzene, 80°C, 5 h
or LiAlH4, Et2O, 35°C, 4 h
·
P(O)Ph2
P(O)Ph2
1b
2b
Scheme 2.
H2–Pd/C, MeOH
25°C, 24 h
Me
·
P(O)Ph2
Me
P(O)Ph2
Me
Me
1a
3
The described procedure for the synthesis of allyl
(diphenyl)phosphine oxides 2a and 2b from allenes 1a
and 1b is new. At present, compound 2 is generally
synthesized from diphenylphosphine (Ph2PH) or its
derivatives by reaction with allyl halides [15], metal-
catalyzed coupling with butadienes, followed by
oxidation of the coupling products with hydrogen per-
oxide [16–18], by reaction with butadienes catalyzed
by calcium complexes [19], or by reaction with cyclo-
propenes in the presence of copper(I) salts [20]. Allyl-
phosphine oxides 2 are important building blocks for
organic synthesis [21, 22].
hydrophosphinoline oxide 4, we isolated dihydro-
phosphinoline oxide 5. Compound 5 was obtained by
us previously by treatment of allene 1a with AlCl3 or
Brønsted acids (H2SO4, CF3SO3H) [8, 9]. The product
ratio did not change when the reaction time was
prolonged to 5 h. This indicated that dihydrophos-
phinoline oxide 5 is formed independently rather than
from compound 4. The formation of 5 may be ration-
alized assuming hydride ion abstraction from the
allylic position [α-position with respect to the phos-
phoryl group] of initial compound 2a by the action of
strong Lewis acid (AlCl3), i.e., under conditions of
superelectrophilic activation, which promote analo-
gous reactions [23]. Allyl type cation generated in this
way is transformed to product 5. Derivatives of 4 were
synthesized previously by cyclization of allyl(phenyl)-
phosphine oxides in polyphosphoric acid [24] or of
(β-hydroxyalkyl)(phenyl)phosphine oxides in
83% phosphoric acid [25].
In order to demonstrate the synthetic potential of
compounds 2, we examined their intramolecular
cyclization by the action of Brønsted or Lewis acids.
Compound 2a in H2SO4 or CF3SO3H at different
temperatures (–10, 0, 25°C) was converted to complex
mixtures of oligomeric products. We succeeded in
accomplishing intramolecular cyclization of 2a in the
presence of 5 equiv of AlCl3 in methylene chloride at
room temperature in 5 min (Scheme 3). However, in
addition to the expected cyclization product, tetra-
Thus, the results of this study showed the pos-
sibility of selective reduction of only one C=C double
bond (nearest to the phosphoryl group) in allenyl
Reactions of allene 1a with different reducing agents
Me
·
P(O)Ph2
Me
P(O)Ph2
[H]
Me
Me
1a
2a
Reaction conditions
Run no.
Yield of 2a, %
reducing agent
temperature, °C
time, h
solvent
1
2
3
4
5
6
HSiCl3, 40 equiv
HSiCl3, 40 equiv
HSiCl3, 40 equiv
LiAlH4, 1 equiv
NaBH4, 1 equiv
NaBH4, 1 equiv
80
80
60
25
25
50
24
24
12
24
24
24
Benzene
1,2-Dichloroethane
CHCl3
94
80
No reactiona
Et2O
79
MeOH
No reactiona
No reactiona
EtOH
a
Quantitative recovery of initial compound 1a.
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 53 No. 7 2017

SELECTIVE REDUCTION OF ALLENYL(DIPHENYL)PHOSPHINE OXIDES
997
Scheme 3.
Me
Me
O
Me
Me
O
AlCl3 (5 equiv), CH2Cl2
25°C, 5 min
Me
P(O)Ph2
+
Me
P
P
Ph
Ph
2a
4
5
(diphenyl)phosphine oxides with formation of allyl(di-
phenyl)phosphine oxides. The latter can be converted
to phosphorus-containing heterocycles, phosphinoline
oxides, by treatment with AlCl3.
mixture was poured into water (10 mL), and the
organic phase was separated, washed in succession
with a saturated aqueous solution of NaHCO3 (15 mL)
and water, and dried over Na2SO4. The solvent was
distilled off under reduced pressure, and the residue
was subjected to silica gel column chromatography
using petroleum ether–ethyl acetate as eluent. The
yields of 2a and 2b were determined after chroma-
tographic isolation.
EXPERIMENTAL
The 1H, 13C, and 31P NMR spectra were recorded at
25°C on a Bruker Avance 400 spectrometer at 400,
100, and 160 MHz, respectively, using CDCl3 as sol-
(3-Methylbut-2-en-1-yl)(diphenyl)phosphine
1
vent and reference (for H and 13C); the phosphorus
oxide (2a). Yield 94 (a), 79% (b); colorless crystals,
chemical shifts were measured relative to H3PO4.
GC/MS analyses were obtained on an Agilent Tech-
nologies G2570A 6850s GC/MSD instrument (HP-
5MS capillary column, 3 m×0.25 mm, film thickness
0.25 μm). The high-resolution mass spectra were
recorded on a Bruker ESI-TOF mass spectrometer. The
purity of the isolated compounds was checked by thin-
layer chromatography on Silufol UV-254 plates. The
products were separated by column chromatography
on silica gel (40–100 μm, Chemapol) using petroleum
ether–ethyl acetate as eluent. The synthesis and prop-
erties of initial allenyl(diphenyl)phosphine oxides
1a–1e were described in [8, 9].
1
mp 151–155°C; published data [15]: 155°C. H NMR
spectrum, δ, ppm: 1.45 d (3H, J = 4 Hz), 1.66 d.d (3H,
J = 4, 1 Hz), 3.11 d.d (2H, J = 15, 8 Hz), 5.23 m (1H),
13
7.47–7.54 m (6H), 7.72–7.78 m (4H). C NMR spec-
trum, δC, ppm: 18.0 d (J = 3 Hz), 25.8 d (J = 2 Hz),
30.8 d (J = 70 Hz), 112.2 d (J = 9 Hz), 128.5 d
(J = 10 Hz), 130.7 d (J = 13 Hz), 131.1 d (J = 11 Hz),
131.7 d (J = 2 Hz), 137.6 d (J = 13 Hz). 31P–{1H}
NMR spectrum: δP 30.99 ppm. Mass spectrum:
m/z 270 [M]+.
(2-Cyclopentylideneethyl)(diphenyl)phosphine
oxide (2b). Yield 95 (a), 87% (b); colorless crystals,
1
mp 171–172°C. H NMR spectrum, δ, ppm: 1.40–
Reduction of allenes 1a and 1b (general proce-
dures). a. With trichlorosilane. A solution of 1 mmol of
allene 1a or 1b and 40 mmol of trichlorosilane in 5 mL
of benzene was heated for 24 or 5 h, respectively, at
80°C with stirring in a glass high-pressure reactor. The
mixture was poured into 10 mL of water, the precip-
itate (silicate) was filtered off, and the filtrate was
washed in succession with a saturated aqueous solution
of NaHCO3 (15 mL) and water and dried over Na2SO4.
The solvent was distilled off under reduced pressure,
and the residue was subjected to silica gel column
chromatography using petroleum ether–ethyl acetate as
eluent. The yields of 2a and 2b were determined after
chromatographic isolation.
1.44 m (4H), 1.90–1.94 m (2H), 2.01–2.05 m (2H),
3.11 d.d (2H, J = 15, 8 Hz), 5.16–5.21 m (1H), 7.18–
7.22 m (1H), 7.47–7.54 m (6H), 7.70–7.76 m (3H).
13C NMR spectrum, δC, ppm: 26.5, 27.1 d (J = 3 Hz),
28.2 d (J = 2 Hz), 29.5 d (J = 130 Hz), 37.1 d (J =
3 Hz), 108.9 d (J = 8 Hz), 128.5 d (J = 8 Hz), 131.1 d
(J = 8 Hz), 131.7 d (J = 2 Hz), 145.1 d (J = 11 Hz).
31P–{1H} NMR spectrum: δP 31.16 ppm. Mass spec-
trum (ESI): m/z 319.1228 [M + Na]+. C19H21NaOP.
Calculated: M + Na 319.1237.
Reduction of allene 1a with hydrogen over Pd/C.
A solution of 0.182 mmol of allene 1a in 20 mL
methanol containing 17.2 mg of 10% Pd/C was stirred
for 24 h at 25°C in a hydrogen atmosphere. The
mixture was filtered through a layer of zelite, and the
solvent was distilled off from the filtrate under reduced
pressure.
b. With lithium tetrahydridoaluminate. A mixture of
1 mmol of allene 1a or 1b and 1 mmol of LiAlH4 in
5 mL of diethyl ether was stirred for 24 h at room
temperature in a hermetically closed glass reactor. The
RUSSIAN JOURNAL OF ORGANIC CHEMISTRY Vol. 53 No. 7 2017

LOZOVSKIY et al.
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ppm: 0.81 d (6H, J = 6 Hz), 1.19–1.39 m (2H), 1.50–
1.60 m (1H), 3.56 d.t (2H, J = 13, 6 Hz), 7.35–7.50 m
(6H), 7.67–7.77 m (4H). Mass spectrum: m/z 272 [M]+.
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aqueous solution of NaHCO3 (25 mL) and water, and
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