Synthesis of phosphiranes

Article abstract of DOI:10.1134/S1070363215020140

Phosphiranes, three-membered phosphorus-containing heterocycles, have been prepared via reaction of tertiary phosphines dilithium derivatives with carbon tetrachloride. The elaborated method can be applied for preparation of some phosphiranes which are not easily accessible.

Full text of DOI:10.1134/S1070363215020140

ISSN 1070-3632, Russian Journal of General Chemistry, 2015, Vol. 85, No. 2, pp. 436–440. © Pleiades Publishing, Ltd., 2015.
Original Russian Text © O.O. Kolodyazhnaya, O.I. Kolodyazhnyi, 2015, published in Zhurnal Obshchei Khimii, 2015, Vol. 85, No. 2, pp. 263–267.
To the 80th Anniversary of B.I. Ionin
Synthesis of Phosphiranes
O. O. Kolodyazhnaya and O. I. Kolodyazhnyi
Institute of Bioorganic Chemistry and Petrochemistry, National Academy of Sciences of Ukraine,
ul. Murmanskaya 1, Kiev, 02094 Ukraine
e-mail: olegkol321@rambler.ru
Received September 18, 2014
Abstract—Phosphiranes, three-membered phosphorus-containing heterocycles, have been prepared via
reaction of tertiary phosphines dilithium derivatives with carbon tetrachloride. The elaborated method can be
applied for preparation of some phosphiranes which are not easily accessible.
Keywords: phosphirane, tertiary phosphine, dicarbanion, P-chloro ylide, bis(alkylidene)phosphorane
DOI: 10.1134/S1070363215020140
Phosphiranes (three-membered phosphorus-containing
heterocycles) are of practical and fundamental interest.
Phosphiranes were described for the first time in 1963
[1, 2], and their formation was unambiguously
confirmed later in [3, 4]. Compounds derived from
phosphiranes can act as ligands for transition metals
complexes; some of the latter revealed valuable
catalytic properties [5, 6]. In general, phosphiranes are
not enough stable; however, their complexes with
transition metals are less reactive and can be isolated
in pure form [3]. Overall, this class of compounds has
been scarcely studied so far; therefore, development of
new methods of phosphiranes preparation is of apparent
interest.
A multi-step preparation route has been discussed,
using diazoalkanes as a source of carbene. The 4π-
electrocyclic closing of bis(methylene)phosphorane a
into three-membered ring is a conrotator process
following the Woodward–Hoffman rule [9, 10].
Similarly, alkylidendiazophosphols were used for
preparation of alkylidenephosphiranes. Other carbene
sources for preparation of phosphiranes include organo-
metallic carbenoids and bis-ylides [11–15].
In the present work we describe synthesis of
phosphiranes via the intermediate formation of tertiary
phosphines dilithium derivatives followed by their
reaction with carbon tetrachloride. The starting tertiary
phosphines II were prepared in high yield (70–90%)
via the phosphorus(III) chlorides I interaction with the
Grignard reagents (Scheme 2).
To date, several convenient methods of phos-
phiranes synthesis have been proposed. In particular,
their preparation via reaction of phosphaalkenes or
phosphaalkynes with different carbenes has been
described [7, 8] (Scheme 1).
Tertiary dibenzylphosphines IIa–IIc could be
metalated with n-butyllithium in the presence of tetra-
methylethylenediamine (TMEDA) with formation of
Scheme 1.
R
R
H
H
R
H
RCHN2
H
R
R2N
R2N
P
P
P
R2N
H
R
R = SiMe3.
436

437
SYNTHESIS OF PHOSPHIRANES
Scheme 2.
R'
Li
H
H
CH2R'
CH2R'
CCl4
R'
R'
ClMgCH2R'
BuLi
RPCl2
P
R
R
P
P
R
Li
R'
H
H
I
II
Scheme 3.
Li
H
CH2Ph
CH2Ph
CH2Ph
Ph
Ph
BuLi/TMEDA
BuLi/TMEDA
H2O/NH4Cl
R
P
P
R
P
R
Ph
Li
H
Li
H
IIIa−IIIc
IVa−IVc
IIa−IIc
CCl4
CCl4
H
CH2Ph
Ph
Ph
Ph
t-Bu
R
P
Li+
−
P
Cl
Cl
H
H
VI
V
MeOH
−LiCl
Ph
H
H
Bn
Bn
O
P
R
P
t-Bu
Ph
VIIIa−VIIIc
VII
R = t-Bu (a), Et2N (b), Bn (c).
colored solutions of mono- or dilithium derivatives of
tertiary phosphines. Interaction of tertiary phosphines
IIa–IIc with equivalent amount of n-butyllithium
provided monolithium derivatives IIIa–IIIc. The
reaction with twofold excess of n-butyllithium in the
presence of TMEDA upon prolonged refluxing in
hexane led to dilithium derivatives IVa–IVc (Scheme 3).
coloration of the reaction mixture. Generally, lithium
derivatives of benzyl-containing compounds are red-
colored due conjugation of the phenyl ring with the
negative charge of carbanion localized at the CH-
group. On top of that, the upfield shift of the 31P NMR
spectra signals was observed in the cases of lithium
derivatives III (by 13–15 ppm) and dilithium
derivatives IV (by 35–40 ppm) as compared to the
starting tertiary phosphines II. In particular, treatment
of (tert-butyl)dibenzylphosphine IIa (δP 11.3 ppm)
Formation of lithium derivatives of tertiary di-
benzylphosphines IIa–IIc was accompanied by deep-red
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KOLODYAZHNAYA, KOLODYAZHNYI
with one equivalent of n-butyllithium yielded mono-
lithium derivative of tertiary phosphine IIIa (δP
–1.5 ppm); refluxing of tertiary phosphine IIa with
twofold excess of n-butyllithium in the presence of
TMEDA in hexane provided dilithium derivative IVa
(δP –25 ppm). Similarly, lithiation of tribenzyl-
phosphine IIc (δP –12 ppm) led to formation of
dicarbanion IVc (δP –51 ppm). Treatment of the
lithium derivatives with aqueous solution of ammo-
nium chloride allowed regeneration of the starting
tertiary phosphines.
Phosphiranes VIIIa–VIIIc could be isolated in
individual form and stored in a refrigerator at –20ºC.
Phosphirane VIIIa containing a P-bound tert-butyl
group was isolated via vacuum distillation; phosphi-
ranes VIIIb and VIIIc were less stable and partially
decomposed during distillation. Nevertheless, those
compounds could be isolated via column chromato-
graphy on oxygen-free silica gel under inert atmosphere.
Structures of phosphiranes VIIIa–VIIIc were
1
confirmed by H, 13C, and 31P NMR spectroscopy as
1
well as by mass spectrometry. The H NMR spectra
Monolithium derivative IIIa reacted with carbon
tetrachloride to form the P-chloro ylide V, the
phosphorus chemical shift (δP 73 ppm) being typical of
such compounds [16, 17]. Reaction of the P-chloro
ylide V with methanol afforded the corresponding
tertiary phosphine oxide VII in quantitative yield.
Halogenating of dilithium derivatives IVa–IVc with
carbon tetrachloride at –70°С gave phosphiranes
VIIIa–VIIIc. The solution color changed from red to
yellow in the course of the reaction; simultaneously,
signals of the starting lithium derivatives IVa–IVc
disappeared and the strong-field signals characteristic
of phosphiranes (from –100 to –180 ppm) appeared in
the reaction mixture 31P NMR spectrum. Likely, the
reaction proceeded via formation of P-chloro ylides
VIa–VIc, similarly to the reaction of monolithium
derivatives III with carbon tetrachloride. The
subsequent elimination of lithium chloride resulted in
conversion of P-chloro ylides VI into bis(alkylidene)
phosphoranes IX undergoing further cyclization to
yield the phosphiranes. Bis(alkylidene)phosphoranes
IX could not be detected by means of NMR method.
Those compounds are known to be stable their
molecules contain bulky substituents (tert-Bu, TMS,
2,4,6-tert-BuC6H3, etc.) at the carbon or phosphorus,
suppressing the intramolecular cyclization [7, 8]. In the
case of bis(benzylidene)phosphiranes, the phenyl
group could not provide sufficient steric stabilization,
and the compounds easily underwent cyclization to
form phosphiranes VIIIa–VIIIc.
contained doublet signals of endocyclic CH-protons at
3.0 ppm with the coupling constant of 2–3 Hz. The 13C
NMR spectra showed doublet signals of carbon atoms
in three-membered ring directly bound to phosphorus,
at 35–40 ppm with 1JCP ≈ 80 Hz. The chemical shift in
31P NMR spectra ranged from –150 to –180 ppm,
being typical of P(III) atom in a three-membered
phosphirane ring.
Even though phosphirane VIIIa–VIIIc molecules
contained three asymmetric centers, a single set of
signals in the NMR spectra indicated formation of the
only one stereoisomer; NMR data allowed elucidation
of phosphiranes VIIIa–VIIIc stereochemistry. In
detail, parameters of 1H and 13C NMR spectra
indicated symmetric structure of the phosphirane
molecule with respect to the plane passing through the
phosphorus atom and a midpoint of the СН–СН bond
perpen-dicularly to the phosphirane ring plane. A
single signal of the endocyclic CH-groups and a very
2
1
small constant JHP of 1–3 Hz in the H NMR spectra
was assigned to the cis-configuration of the hydrogen
atoms in the groups with respect to lone-electron pair
of trivalent phosphorus atom and trans-configuration
with respect to the substituent at the phosphorus atom.
High stereoselectivity of the reaction of dilithium
derivatives IVa–IVc with carbon tetrachloride coin-
cided with intermediate formation of bis(alkylidene)-
phosphoranes IX and conrotator mechanism of their
cyclization following the rules of orbital symmetry reten-
tion in concerted reactions (the Woodward–Hoffman rule).
The spectral parameters of the phosphiranes
(extremely low chemical shift of the phosphorus
nucleus, up-field shift of the signals of endocyclic CH-
Ph
H
1
groups, and low spin-spin coupling constants JPC and
VIIIa−VIIIc
2JНP) were typical of the three-membered rings and
could be explained by significant difference between
HOMO and LUMO levels and by p-character of the
lone-electron pair of the phosphorus [3].
VI
R P
−LiCl
Ph
H
IX
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439
SYNTHESIS OF PHOSPHIRANES
centrifuged off, and the solvent was evaporated in
vacuum. The signal of P-chloro ylide V at 73.0 ppm
was observed in 31P NMR spectrum of the residue
(yellow liquid). 0.015 mol of methanol was added to a
solution of ylide V in 5 ml of diethyl ether cooled to 0°С.
The reaction mixture was incubated during 0.5 h at
0°С, and then evaporated. The residue was yellowish
To conclude, a convenient method to prepare
phosphiranes has been elaborated.
EXPERIMENTAL
In this experimental work chemicals, silica gel, and
TLC plates (Polіgram SIL G/UV254) from Fluka and
Acros were used. The solvents were distilled under
inert atmosphere before use.
1
crystalline product. Yield 80%, mp 156–158°С. Н
NMR spectrum (CDCl3), δ, ppm: 1.04 d (9Н, CH3C,
JHР 14.4 Hz), 3.01 d q (4Н, РСН2, J 15, J 12 Hz), 7.21
m (10Н, С6H5). 31Р NMR spectrum (CDCl3): δP
53.0 ppm. Found, %: С 75.41; Н 8.08; Р 10.76.
С18Н23ОР. Calculated, %: С 75.50; Н 8.10; Р10.82.
NMR spectra were registered using a Varian VXR-
300 instrument [300 MHz (1H), 75 MHz (13C), and
126.16 MHz (31P)] relative to internal Me4Si (1H and
13C) or external 85% H3PO4 (31P) references.
1-tert-Butyl-2,3-diphenylphosphirane
(VIIIa).
tert-Butyldibenzylphosphine (IIa). A solution of
0.22 mol of benzylmagnesium chloride in diethyl ether
was added to a solution of 0.1 mol of tert-butyl-
dichlorophosphine in 100 mL of diethyl ether upon
stirring and cooling to 0°С. The reaction mixture was
stirred during 1 h at room temperature, and then
refluxed during 2 h. The formed precipitate was
centrifuged off, the solvent was distilled off, and the
product was extracted from the residue with hot
hexane. The extract was evaporated, and the residue
was distilled in vacuum. Yield 60%, bp 130–140°С
(0.1 mmHg). 1Н NMR spectrum (CDCl3), δ, ppm: 1.1 d
(9H, CH3, J 8 Hz), 2.9 d (4H, CH2Ph, J 4 Hz), 7.1–7.5
m (10H, Ph). 31Р NMR spectrum (CDCl3): δР 11.3
ppm. Found, %: C 79.45; H 8.68; P 11.71. C18H23P.
Calculated, %: C 79.97; H 8.58; P 11.46.
0.025 mol of tetramethylethylenediamine and a
solution of 0.025 mol of n-butyllithium in hexane were
sequentially added to a solution of 0.01 mol of tert-
butyldibenzylphosphine (IIa) in 10 mL of hexane. The
reaction mixture was heated at 50°С during 3 h. After
the complete conversion, the only signal at –25.5 ppm
was observed in 31P NMR spectrum of the reaction
mixture, assigned to dilithium derivative of tert-
butyldibenzylphosphine IVa. Next, 0.03 mol of carbon
tetrachloride was added to a solution of the dilithium
derivative in hexane at –60°С. The reaction mixture
turned yellow. Precipitate of lithium chloride was
filtered off, the solvent was evaporated, and the residue
was distilled in vacuum. Yield 50%, bp 130°С
1
(0.05 mmHg), mp 46–47°C [19]. Н NMR spectrum
(CDCl3), δ, ppm: 1.18 d (9Н, СН3С, JHP 12.6 Hz), 3.13
d (2Н, РСН, JHP 2.6 Hz), 7.05–7.45 m (10Н, С6Н5).
13C NMR spectrum (CDCl3), δС, ppm: 16.0, 17.8, 33.5,
38.6, 35.7, 125.9, 128.0, 130.2, 130.3, 137.0, 137.1.
31Р NMR spectrum (CDCl3): δР 151 ppm. Mass
spectrum (70 eV): m/e 268 [M+]. Found P, %: 11.65.
С18Н21Р. Calculated P, %: 11.54.
N,N-Diethylaminodibenzylphosphine (IIb) was
prepared similarly from diethylaminodichlorophosphine.
Yield 60%, bp 145°С (0.1 mmHg). 1Н NMR spectrum
(CDCl3), δ, ppm: 0.95 t (6H, CH3, J 7 Hz), 2.9 m (4H,
CH2Ph), 3.1 m (4H, CH2CH3), 7.1–7.5 m (10H, Ph).
31Р NMR spectrum (CDCl3): δP 66.0 ppm. Found, %:
N 4.91; P 10.85. C18H24NP. Calculated, %: N 4.91; P
10.85.
1-Diethylamino-2,3-diphenylphosphirane (VIIIb)
was prepared similarly. The product was isolated by
column chromatography eluting with the 1 : 1 toluene–
Tribenzylphosphine (IIc) was prepared similarly
from phosphorus trichloride [18]. Yield 85%. 1Н NMR
spectrum (C6D6), δ, ppm: 2.95 d (6H, CH2, J 2 Hz),
6.8–7.3 m (15Н, С6Н5). 31Р NMR spectrum (CDCl3):
δP 12.0 ppm. Found P, %: 10.25. C21H21P. Calculated
P, %: 10.18.
1
hexane mixture. Yield 35%, yellow oily substance. Н
NMR spectrum (С6D6), δ, ppm: 0.93 t (6H, CH3, JHH
7.0 Hz), 2.8 m (4H, NCH2), 3.9 d (2H, PCH, JPH
≈
2 Hz), 7.0 m (10H, Ar). 13C NMR spectrum (С6D6), δC,
ppm: 16.0, 39.0 d (JСР 44.3 Hz), 45.6, 45.8, 125.9,
128.0, 130.2, 130.3, 137.0, 137.1. 31Р NMR spectrum
(C6D6): δP –95 ppm. Mass spectrum (70 eV): m/e 283
[M+]. Found, %: N 4.91; P 11.05. C18H22NP. Cal-
culated, %: N 4.94; P 10.93.
tert-Butyldibenzylphosphine oxide (VII). 0.015 mol
of tetramethylethylenediamine and a solution of
0.012 mol of n-butyllithium in hexane were
sequentially added to a solution of 0.01 mol of tert-
butyldibenzylphosphine IIa in 10 mL of hexane. The
reaction mixture was stirred at 50°C during 1 h and
then cooled to –60°C; 0.015 mol of carbon tetra-
chloride was added. The formed precipitate was
1-Benzyl-2,3-diphenylphosphirane (VIIIc) was
prepared similarly. The product was isolated by
column chromatography eluting with the 1 : 1 toluene–
hexane mixture, followed by recrystallization from
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KOLODYAZHNAYA, KOLODYAZHNYI
1
8. Niecke, E., Leuer, M., and Nieger, M., Chem. Ber.,
hexane. Yield 25%, mp 80°C. Н NMR spectrum
(C6D6), δ, ppm: 2.30 d (PCH2, JPH 4.0 Hz), 2.90 d (2H,
PCH, JPH 2.0 Hz), 6.5–7.8 m (15Н, Ph). 13C NMR
spectrum (C6D6), δС, ppm: 35.0, 36.0, 36.5 d (JPC 45
Hz), 123.6, 123.7, 125.5, 125.7, 126.9, 128.0, 130.8,
130.9, 137.2, 137.6. 31Р NMR spectrum (CDCl3): δP
–180 ppm. Mass spectrum (70 eV): m/e 302 [M+].
Found, %: C 83.42; H 6.33; P 10.35. C21H19P.
Calculated, %: C 84.0; H 6.38; P 10.24.
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