Published on the web June 6, 2013
1065
Selective Addition of P(O)-H Bonds to Alkynes Catalyzed by Transition Metals Immobilized
on Polystyrene-bound Triphenylphosphine
Tieqiao Chen,1 Yongbo Zhou,1 Cancheng Guo,*1 and Li-Biao Han*2
1College of Chemistry and Chemical Engineering, Hunan University, Changsha 410082, P. R. China
2National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565
(Received April 22, 2013; CL-130374; E-mail: ccguo@hnu.edu.cn, libiao-han@aist.go.jp)
Addition of P(O)-H bonds to alkynes catalyzed by transition
metals (Rh, Pd, and Ni) immobilized on polystyrene-bound
triphenylphosphine proceeded efficiently to afford high yields of
the addition products with high regioselectivity. The immobi-
lized catalysts were easily recovered from the reaction mixture
via simple centrifugal separation and could be reused several
times without severe deactivation.
selective addition of P(O)-H bonds to alkynes catalyzed by
recyclable transition-metal catalysts immobilized on this poly-
mer-bound triphenylphosphine (Figure 1). We found that being
similar to homogeneous counterparts, the immobilized rhodium
catalyst showed high catalytic activity and functional tolerance
to produce the anti-Markovnikov addition product in high yield,
while the immobilized nickel and palladium catalysts could
produce the Markovnikov adducts selectively in high yields.
These immobilized metal catalysts could be recovered by simple
filtration and reused several times without deactivation.
Transition-metal-catalyzed addition of P(O)-H bonds to
alkynes is one of the most efficient and direct methods for the
synthesis of organophosphorus compounds,1 which have wide
applications in medicine, agriculture,2 asymmetric catalysis3 and
industrial processes.4 Many catalytic reactions for their prepa-
ration by homogeneous catalysts have been developed such as
Pd-catalyzed, Ni-catalyzed, Rh-catalyzed, and Cu-catalyzed
reactions.1,5,6 In 1996, we reported the Pd-catalyzed addition
of (MeO)2P(O)H to alkynes affording Markovnikov adducts;6a
In 2001, an efficient Rh-catalyzed system for the addition of
diphenylphosphine oxide and a five-member cyclic H-phosphite
to alkynes was developed for the synthesis of anti-Markovnikov
alkenylphosphorus compounds;6h,6i Subsequently, an efficient
Ni-catalyzed hydrophosphorylation of alkynes with a variety
of P(O)-H bonds to generate both anti-Markovnikov and
Markovnikov adducts was developed.6g Although those homo-
geneous catalytic systems can efficiently produce the products,
they are not favorable for a large-scale industrial process
because those catalysts are difficult to reuse and the removal of
the metals from the products are usually time-consuming.
Supported catalysts have advantages in that they can be
easily separated and recovered from the reaction mixtures by
simple filtration and can be reused. Thus, the application of
transition-metal catalysts immobilized on a support could be one
of the best methods to maximize the product quantity and
minimize waste.7 Recently, Cai et al. reported an immobilized
rhodium catalyst on silica which catalyzed the addition of
Ph2P(O)H to terminal alkynes.8 However, its preparation is time-
consuming and breakdown of the catalyst can take place by the
hydrolysis of the labile Si-O bonds. In comparison, a polymer-
bound triphenylphosphine is commercially available and stable
toward hydrolysis (Figure 1). Herein, as a part of our ongoing
project on the development of transition-metal-catalyzed phos-
phorous-carbon bond-forming reactions,1b,6 we report the
Thus, as a model reaction, a rhodium catalyst was
immobilized by mixing [Rh(COD)Cl]2 (0.1 mmol) and polysty-
rene-bound triphenylphosphine9 (250 mg containing 0.6 mmol
PPh3) in toluene (3 mL) at room temperature overnight. The
polymer was collected by filtration under nitrogen and washed
three times with toluene.10 After drying under high vacuum,
deep brown solid was obtained. The catalytic activity of this
immobilized catalyst was tested as follows: a mixture of 34.7 mg
of the immobilized catalyst (ca. 5 mol % Rh based on
[Rh(COD)Cl]2 used),10 1-octyne (0.5 mmol) and diphenylphos-
phine oxide (0.5 mmol) were mixed in toluene (1 mL). The
mixture was heated at 70 °C for 3 h. As confirmed by GC
chromatography, the starting diphenylphosphine oxide was
completely consumed and the adduct 3a was obtained quanti-
tatively. By centrifugal separation, the catalyst was removed and
removal of volatiles under vacuum gave NMR spectroscopically
pure 3a as confirmed by 1H and 31P NMR spectroscopies
(131.0 mg, 84% isolated yield).11 The regioselectivity is suffi-
ciently high that only the anti-Markovnikov product could
be detected by 1H NMR spectroscopy. It is noted that the
immobilized rhodium catalyst could be used again without
deactivation. Thus, after centrifugal separation, the catalyst was
reused for the next reaction to give the adduct 3a quantitatively
(Table 1). The above procedures have been repeated 5 times and
the immobilized rhodium catalyst retained its catalytic activity
and selectivity, indicating that this immobilized transition-metal
catalytic system can be efficiently applied to the selective
addition of Ph2P(O)H to 1-octyne which greatly simplify the
reaction process.11
The immobilized rhodium catalyst could be used for the
addition of other P(O)-H bonds to a variety of alkynes.11 As
demonstrated in Table 2, the immobilized rhodium catalyst
achieved satisfying yields and selectivity for the addition
reactions of diphenylphosphine oxide to both aromatic and
aliphatic alkynes. This reaction features wide functional groups
tolerance and many functional groups such as Cl (Runs 2 and 6),
hydroxy (Run 3), silyl (Run 4), olefin (Run 5), and ferrocenyl
(Run 8) were all compatible under the present heterogeneous
reaction conditions. Two phosphorus groups also could be easily
introduced into diynes in one-pot as exemplified by the addition
P(O)R1R2
[Ni]/L or [Pd]/L
Markovnikov addition
[Rh]/L
1
2
+
R R P(O)H
R
R
anti-Markovnikov addition
P(O)R1R2
R
L: polystyrene
PPh2
Figure 1. Addition of P(O)-H bonds to alkynes catalyzed by
supported metal catalysts.
Chem. Lett. 2013, 42, 1065-1067
© 2013 The Chemical Society of Japan
Chen, Tieqiao
