A Convenient and Direct Route to Phosphinoalkynes via Copper-Catalyzed Cross-Coupling of Terminal Alkynes with Chlorophosphanes

Article abstract of DOI:10.1055/s-2003-42493

A new efficient method to obtain various alkynylphosphanes R _nP(≡R′)_3-n [R = Ar, Alk, alkoxy, amido R′ = Ar, Het, Alk, CH₂Z (Z = OMe, NMe₂), n = 0-2] has been developed by means of cross-coupling reaction of chl

Full text of DOI:10.1055/s-2003-42493

PAPER
2835
A Convenient and Direct Route to Phosphinoalkynes via Copper-Catalyzed
Cross-Coupling of Terminal Alkynes with Chlorophosphanes
C
opper-Catalyzed
l
Cross-C
a
oupling of
d
T
erminal
A
i
lkynes
m
with Chlorophospha
i
nes r V. Afanasiev,a Irina P. Beletskaya,*a Marina A. Kazankova,a Irina V. Efimova,a Mikhail U. Antipinb
a
Department of Chemistry, Moscow State University (MSU), Leninskie Gory 1, Building 3, 119992 Moscow, Russia
Fax +7(095)9393618; E-mail: beletska@org.chem.msu.ru
b
INEOS, Vavilova str., 28, 119991, GSP-1, Moscow Russia
Received 7 October 2003; revised 11 October 2003
hours. The resulting phosphanes 3 are formed in nearly
quantitative yields.
Abstract: A new efficient method to obtain various alkynylphos-
phanes RnP(– –R
[R = Ar, Alk, alkoxy, amido R = Ar, Het,
3–n
Alk, CH2Z (Z = OMe, NMe2), n = 0–2] has been developed by
means of cross-coupling reaction of chlorophosphanes RnPCl3–n
(R = Ar, Alk, Alkoxy) with terminal alkynes catalyzed by cuprous
salts.
Under optimal conditions terminal alkynes easily react
with diaryl- and dialkylchlorophosphanes (Table 1, en-
tries 1–12), aryldichlorophosphanes (Table 1, entry 14)
and PCl3 (Table 1, entries 15, 16). In all cases mono-, bis-
or tris(alkynyl)phosphanes are isolated in high yields with
the exception of phosphane 3m, which is formed from
bulky t-Bu2PCl in 50% yield only after heating at 120 °C
for 24 hours (Table 1, entry 13). Poor electrophiles such
as (RO)2PCl, (R2N)2PCl and R2NPCl2 also reacted with
terminal alkynes in the presence of Cu catalyst to give
alkynyl phosphonites and phosphinites in high yields.
Key words: phosphorus, cross-coupling, alkynes, copper, homoge-
nous catalysis
Alkynylphosphanes are an attractive class of compounds
useful in organic synthesis.1 They can be identified as
common building blocks in constructing a broad variety
of alkenyl- and alkylphosphanes2 bearing functional
groups and phosphorus heterocycles.3 Also alkynylphos-
phanes can be utilized for the preparation of neutral and
cationic, homo- and hetero-bridged complexes,4 metalla-
cycles,5 and transition metal clusters bearing polyyne
ligand.6
Terminal alkynes bearing alkyl and aryl substitutes at the
triple bond could be introduced using this reaction with
halogenophosphanes under the above conditionsThe use
of Cu(I) catalyst makes it possible to carry out the reaction
with alkynes containing sensitive functional groups
(Table 1, entries 3, 10, 11) as well as alkynes bearing
heteroaryl substituents (Table 1, entries 7–9). One should
notice that the reaction with alkynes (Table 1, entries 3, 6,
10, 11) in the presence of Ni or Pd catalysts failed to pro-
vide efficiently products of cross-coupling since the reac-
tion led to complex mixture of unidentified compounds.7
We have previously shown that alkynylphosphanes com-
prising one, two or three acetylenic substitutes at phos-
phorus atom, could be obtained by cross-coupling
reaction between terminal alkynes and aryl (or alkyl)
chlorophosphanes catalyzed by Ni or Pd complexes.7 The
reaction represents the heteroanalog of Sonogashira reac-
tion.8
The mechanism of Cu-catalyzed cross-coupling may in-
clude either P–Cl bond activation as it proceeds under ca-
talysis by Ni complexes7 or formation of copper-
acetylenic intermediate by reacting a Cu complex with a
terminal alkyne in the presence of Et3N.
We report here a convenient method of preparing alky-
nylphosphanes which is based on utilizing Cu(I) salts as
catalyst in the reaction between terminal alkynes and
chlorophosphanes (Equation 1).
We have demonstrated that the interaction of Ph2PCl with
CuI in toluene led to the formation of a complex. By per-
forming an X-ray analysis it was shown that the above
complex proved to be a tetrahedral complex bearing three
molecules of chlorophosphane (Ph2PCl)3CuI (Figure 1).9
Assuming the above intermediate, the mechanism of Cas-
tro reaction looks most reasonable10 (Scheme 1).
1 mol% CuX, Et3N
RnPCl3-n
+
R'
MePh, r.t.
1
2
RnP(
R')3-n
3
Equation 1
The reaction proceeds smoothly by stirring a toluene solu-
tion of chlorophosphane 1, alkyne 2, Et3N and CuI or
CuBr (1 mol%) under argon at room temperature for 1–6
Phosphinoalkynes 3; General Procedure
Chlorophosphane 1, CuI (1 mol%), Et3N, alkyne 2, and solvent
were mixed in a Schlenk flask and stirred for an appropriate period
of time at r.t. (see Table 1 for molar amounts used). The progress of
the reaction was monitored by 31P NMR measurements every hour.
After completion of the reaction (disappearance of the signal of
chlorophosphane), the ammonium salt was removed by filtration,
and the solvent was evaporated under reduced pressure. The crude
product was then purified by passing through a silica gel column
(CH2Cl2–hexane) or distilled under reduced pressure (Table 1).
SYNTHESIS 2003, No. 18, pp 2835–2838
x
x.
x
x
.
2
0
0
3
Advanced online publication: 19.11.2003
DOI: 10.1055/s-2003-42493; Art ID: Z14903SS
© Georg Thieme Verlag Stuttgart · New York

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V. V. Afanasiev et al.
PAPER
Table 1 Cross-Coupling Chlorophosphanes and Chlorophosphites with Terminal Alkynesa
Entry
Chlorophosphane
R in
Product
Yield (%)b
R'
Ph2P
Ph
1
2
Ph2PCl (1a)
Ph
99 (95)c
95 (92)c
3a
Ph2P
1a
4-MeC6H4
C6H4Me-4
C6H4OMe-4
C6H4NMe2-4
3b
Ph2P
3
4
1a
4-MeOC6H4
4-Me2NC6H4
2-Me2NC6H4
3-CF3C6H4
2-pyridyl
2-thienyl
6-quinolinyl
MeOCH2
Me2NCH2
Ph
99 (96)c
96 (93)c
98 (94)c
95 (92)c
99 (93)c
94 (90)c
96 (92)c
83 (49)c
96 (92)c
98 (80)c
50c,d
3c
Ph2P
1a
3d
Ph2P
5
1a
C6H4NMe2-2
C6H4CF3-3
Py-2
3e
Ph2P
6
1a
3f
Ph2P
7
1a
3g
Ph2P
8
1a
Thienyl-2
Quinol.-6
CH2OMe
CH2NMe2
3h
Ph2P
9
1a
3i
Ph2P
10
11
12
13
14
15
16
17
1a
3j
Ph2P
1a
3k
3l
i-Pr2PCl (1b)
t-Bu2PCl (1c)
PhPCl2 (1d)
PCl3 (1e)
PCl3 (1e)
Ph
3m
PhP(
Ph
99 (96)e
98 (78)f
95 (81)f
96 (42)c,g
Ph)2
Ph)3
3n
P(
Ph
3o
P(
4-MeC6H4
Ph
Tol-p)3
3p
O
P
O
O
PCl
O
Ph
3q
1f
18
(i-PrO)2PCl (1g)
Ph
98 (36)c,g
3r
(Et2N)2P
19
20
(Et2N)2PCl (1h)
Et2NPCl2 (1i)
Ph
Ph
98c,g
99c,g
Ph
3s
Et2NP(
Ph)2
3t
a Reaction conditions: chlorophosphane (1 mmol), CuI (1 mol%), toluene, r.t.
b Based on 31P NMR spectrum, isolated yields are given in parentheses.
c Alkyne (1.25 mmol), Et3N (3 mmol), 6–8 h.
d 120 °C, 24 h.
e Alkyne (2.5 mmol), Et3N (6 mmol), 4 h.
f Alkyne (3.75 mmol), Et3N (9 mmol), 45 min.
g Decomposes during distillation.
Synthesis 2003, No. 18, 2835–2838 © Thieme Stuttgart · New York

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Copper-Catalyzed Cross-Coupling of Terminal Alkynes with Chlorophosphanes
2837
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Figure 1 X-ray crystal structure of (Ph2PCl)3CuI9
Compounds were obtained in sufficiently pure state as indicated by
their 1H and 13C NMR spectra.11
Acknowledgments
(8) Handbook of Organopalladium Chemistry for Organic
Synthesis; Negishi, E., Ed.; Wiley-VCH: New York, 2002.
(9) As found from X-ray data (Figure 1), the copper atom in the
structure of (Ph2PCl)3CuI adopts a tetrahedral coordination.
The copper and chlorine atoms are situated on either sides of
the plane of phosphorus atoms. The Cu(1) atom is deviated
from the plane of P(1), P(2) and P(3) atoms to 0.75 Å. Also,
the chlorine atoms are antiperiplanar to the iodine atom, the
torsion angle ClPCuI is equal to 167° on an average. X-ray
investigation of structure 1 was carried out on Bruker Smart
CCD 1000 diffractometer at 293 K. Crystals are monoclinic,
a = 20.381(4), b = 9.462(2), 20.411(4) Å, = 112.395(4)°,
space group P21/c, Z = 4 M = 852.3, F(000) = 1696,
[MoK& agr;] = 18.25 cm–1. Intensities of 27979 reflections
were measured and 10473 independent reflections were used
for further refinement. The refinement was converged to
wR2 = 0.0623 and GOF = 0.980 for all independent
reflections [R1 = 0.0325 was calculated against F2 for 5790
observed reflections with I > 2 (I)]. Experimental and
crystal data were submitted to Cambridge Crystallographic
Data Centre.
Vladimir V. Afanasiev is grateful to INTAS YSF 169 for financial
support. We thank Prof. Anatoly A. Borisenko for recording the
NMR spectra and Alexander Korlyukov for crystallographic inve-
stigation. We thank The Grant of Russian Federation President Sup-
porting Leading Scientific Schools – 1611.2003.03 of financial
support.
References
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organischen Chemie, Part 2, Vol. 5; Müller, E., Ed.; Thieme
Verlag: Stuttgart, 1977.
Synthesis 2003, No. 18, 2835–2838 © Thieme Stuttgart · New York

2838
V. V. Afanasiev et al.
PAPER
(10) (a) Stephens, R. D.; Castro, C. E. J. Org. Chem. 1963, 28,
2163. (b) Stephens, R. D.; Castro, C. E. J. Org. Chem. 1963,
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(11) For example: 2-(2-Pyridyl)ethynyldiphenylphosphane(3g):
Yield: 93%; light yellow solid; mp 32 °C. 31P{H} NMR
(162.6 MHz, CDCl3): = –34.44 (s). 1H NMR (400 MHz,
CDCl3): = 6.98 (m, 1 H), 7.19 (m, 1 H), 7.21 (m, 7 H), 7.37
(m, 1 H), 7.61 (dt, 4 H, J = 1.4 Hz), 8.43 (m, 1 H). 13C NMR
(100.6 MHz, CDCl3): = 86.11 (d, J = 9.8 Hz), 106.22,
122.74, 126.78, 128.15 (d, J = 7.6 Hz), 128.69, 132.30 (d,
J = 21.3 Hz), 134.79 (d, J = 7.5 Hz), 135.55, 142.04, 149.46.
(3-Methoxyprop-1-ynyl)(diphenyl)phosphane(3j): Yield:
49%; light yellow oil; bp 160 °C/0.1 Torr. 31P{H} NMR
(162.6 MHz, CDCl3): = –34.62 (s). 1H NMR (400 MHz,
CDCl3): = 3.31 (s, 3 H), 4.17 (s, 2 H), 7.24 (m, 6 H), 7.61
(dt, 4 H, J = 1.7 Hz). 13C NMR (100.6 MHz, CDCl3):
57.23, 60.20, 83.22 (d, J = 7.6 Hz), 104.36, 128.26 (d,
J = 7.6 Hz), 128.72, 132.14 (d, J = 21.3 Hz), 135.59.
=
Synthesis 2003, No. 18, 2835–2838 © Thieme Stuttgart · New York