Synthesis of water-soluble dendritic phosphine ligands and their application to hydration of alkynes in aqueous media

Article abstract of DOI:10.1246/bcsj.82.261

A series of water-soluble dendritic ligands with a phosphine core was synthesized through the coupling of tris(4-hydroxyphenyl)phosphine oxide with poly(benzyl ether) dendron having tri(ethylene glycol) units, followed by reduction. By employing the corresponding water-soluble phosphine-gold(I) dendrimers as a catalyst, the hydration of alkynes proceeded smoothly. Furthermore, by membrane separation based on the nano-order size of the dendritic catalyst, the gold(I) catalyst was recycled without deactivation. ? 2009 The Chemical Society of Japan.

Full text of DOI:10.1246/bcsj.82.261

© 2009 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 82, No. 2, 261–266 (2009)
261
Synthesis of Water-Soluble Dendritic Phosphine Ligands and
Their Application to Hydration of Alkynes in Aqueous Media
Ken-ichi Fujita,* Masato Kujime, and Takahito Muraki
National Institute of Advanced Industrial Science and Technology (AIST),
AIST Tsukuba Central 5, 1-1-1 Higashi, Tsukuba 305-8565
Received September 8, 2008; E-mail: k.fujita@aist.go.jp
A series of water-soluble dendritic ligands with a phosphine core was synthesized through the coupling of tris(4-
hydroxyphenyl)phosphine oxide with poly(benzyl ether) dendron having tri(ethylene glycol) units, followed by reduction.
By employing the corresponding water-soluble phosphineÍgold(I) dendrimers as a catalyst, the hydration of alkynes
proceeded smoothly. Furthermore, by membrane separation based on the nano-order size of the dendritic catalyst, the
gold(I) catalyst was recycled without deactivation.
Organic reactions in water are currently of great interest
O-Gn[R]
because water is a readily available, economical, safe, and
environmentally friendly solvent.1 To date, various water-
soluble ligands have been prepared, and their applications to
aqueous media organic syntheses have been reported. Above
all, water-soluble phosphineÍtransition metal catalysts have
been widely investigated.2
P
O-Gn[R]
Gn[R]-O
1(Gn[R])
In recent years, organogold compounds as homogeneous
catalysts have been widely investigated.3 Gold catalysts
activate the addition of nucleophiles to unsaturated carbon
compounds.4 It has been reported that several phosphineÍgold
catalysts cause the hydration of alkynes with high efficiency.5
However, there are few examples of the use of water-soluble
phosphineÍgold catalysts.4g,5a
(Z = H, K)
CO2Z
CH2
R =
[CO2Z]
-(CH2CH2O)3CH3
[TEG]
O-R
Dendrimers are fascinating molecules due to their unique
physical and chemical properties caused by their well-defined
hyperbranched frameworks.6 From the perspective of their
character, immobilization of functional or catalytic sites on
dendrimers is one of the important goals. In particular,
dendritic catalysts have received considerable attention due to
the possibility of catalyst recovery using membrane separation
by nanofiltration techniques7 and due to the alteration of
catalyst solubility by peripheral modification.8
G1[R]:
G2[R]:
CH2
O-R
O-R
O
O
O-R
O-R
CH2
O-R
O-X
We have recently synthesized a series of dendritic phosphine
core ligands having carboxy groups at the peripheral layer
1(Gn[CO2H]), which is shown in Figure 1. By employing a
water-soluble 1(Gn[CO2K])Ípalladium catalyst, an aqueous
media SuzukiÍMiyaura reaction was carried out smoothly.9
However, the dendritic phosphine ligand 1(Gn[CO2K]), which
is easily dissolved in water, cannot be utilized under neutral or
acidic conditions. We wish to report herein the preparation of a
series of water-soluble dendritic phosphines having tri(ethylene
glycol) units at the peripheral layer 1(Gn[TEG]), hydrations of
alkynes, conducted by employing the corresponding water-
soluble phosphineÍgold(I) catalyst, and the recycling of the
higher generation dendritic gold(I) catalyst by membrane
separation based on its nano-order size. We were able to
successful gold(I) catalyst recycling in hydrations of alkynes
without any organic solvent.
O
O
O-X
O-X
O
O
O-X
O-X
CH2
O
O
O-X
O-X
G3[R]: X = R
G4[R]: X =
O-R
O-R
O-X
CH2
Figure 1. Structural formulas of dendrimer 1(Gn[R]) and
Gn[R] dendrons (n = 1Í4).
Published on the web February 13, 2009; doi:10.1246/bcsj.82.261

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Bull. Chem. Soc. Jpn. Vol. 82, No. 2 (2009)
Gn[TEG]-Br
Water-Soluble Phosphine Core Dendrimer
Table 2. Hydration of Various Alkynes Using 1(G1[TEG])Í
Gold(I) Catalyst
3(Gn[TEG])
(n = 1−4)
K2CO3
1(G1[TEG]) + AuCl(SMe2)
18-Crown-6
O
(0.5 mol %)
O P
OH
R1
R2
R2
O P
OGn[TEG]
DMF
70 °C
R1
3
AgOTf, TfOH
3
2
80 °C
4(Gn[TEG])
G1 : 99%
G2 : 98%
G3 : 99%
G4 : 96%
AgOTf Time Yielda)
Entry
R1
R2
Solvent
/mol % /h
/%
1
2
3
4
5
6
7
Ph
Ph
n-C6H13
n-C3H7
CH3
H
Ph
H
MeOHÍH2Ob)
MeOHÍH2Ob)
MeOHÍH2Ob)
0.5
0.5
0.5
0.5
0
2
2
5
5
0.5
0.5
0.5
91
84
73
54
98
97
98
HSiCl3
Et3N
P
OGn[TEG]
Xylene
120 °C
3
n-C3H7 MeOHÍH2Ob)
C2H4OH
1(Gn[TEG])
H2O
H2O
H2O
G1 : 97%
G2 : 97%
G3 : 90%
G4 : 96%
HOC3H6
HO2CC2H4
H
H
0
0
a) Determined by integration of 1H NMR absorptions referred to
an internal standard. b) MeOH:H2O = 9:1 (v/v).
Scheme 1. Synthesis of dendrimer 1(Gn[TEG]).
Table 1. Hydration of Phenylacetylene Using 1(Gn[TEG])Í
Gold(I) Catalyst
phosphineÍgold(I) catalyst 1(G1[TEG])ÍAuCl was easily dis-
solved in water, hydration of phenylacetylene did not proceed
in water, probably due to low solubility of phenylacetylene in
water (Entry 1). In contrast, by carrying out the hydration in
aqueous methanol (MeOH:H2O = 9:1 (v/v)), the hydration of
phenylacetylene proceeded to afford acetophenone in a 39%
chemical yield (Entry 3). Furthermore, by the preparation of
the corresponding gold(I) triflate 1(G1[TEG])ÍAuOTf as a
catalyst with the addition of AgOTf, the chemical yield of
acetophenone was enhanced (91% for Entry 4) because of an
increase of cationic property of the gold(I) catalyst.4a Even in
the case of using gold(I) triflate as a catalyst, the absence of
TfOH significantly decreased the chemical yield of acetophe-
none (9% for Entry 5).10
We subsequently performed this hydration using the second-
and third-generation dendritic gold(I) catalysts. However the
chemical yield of acetophenone was decreased by increasing
the generation of the dendritic catalyst, probably due to steric
hindrance of the dendron, contrary to our expectations (55% for
Entry 6 and 47% for Entry 7).
Next, the hydrations of various alkynes were carried out
through the use of the first-generation 1(G1[TEG])Ígold(I)
catalyst (Table 2). In all cases, the hydration of alkynes
proceeded smoothly to afford the corresponding ketones in fair
yields. Especially in the case of alkynes having a hydroxy or
carboxy group, the hydration reactions proceeded in water for
0.5 h in high chemical yields even without preparation of the
corresponding gold(I) triflate, probably due to high solubility of
these alkynes in water and the intramolecular nucleophilic
coordination of ÍOH to a triple bond11 (more than 97% for
Entries 5Í7).
Because water-soluble alkynes afforded high reactivity, we
performed the hydration of 4-pentyn-1-ol through the use of
various generation 1(Gn[TEG])Ígold(I) catalysts at room
temperature (Table 3). As a result, the first-generation dendritic
gold(I) catalyst gave the highest chemical yield (93%), and the
higher generation dendritic catalysts also afforded compara-
tively high chemical yields (G2: 89%, G3: 86%, and G4: 89%).
Since dendrimers with high generation are nano-order sized
polymers, membrane separation by nanofiltration techniques is
1(Gn[TEG]) + AuCl(SMe2)
(0.5 mol % )
O
Ph
AgOTf, TfOH
Ph
80 °C
AgOTf TfOH Time Yielda)
Entry Gn
Solvent
/mol % /mol %
/h
/%
1
2
3
4
5
6
7
G1
G1
H2O
H2O
0
0.5
0
0.5
0.5
0.5
0.5
8
8
8
8
0
8
8
6
6
2
2
2
2
2
0
0
G1 MeOHÍH2Ob)
G1 MeOHÍH2Ob)
G1 MeOHÍH2Ob)
G2 MeOHÍH2Ob)
G3 MeOHÍH2Ob)
39
91
9
55
47
a) Determined by integration of 1H NMR absorptions referred to
an internal standard. b) MeOH:H2O = 9:1 (v/v).
Results and Discussion
Novel phosphine core dendrimers having the tri(ethylene
glycol) unit 1(Gn[TEG]) were synthesized according to
Scheme 1. An N,N-dimethylformamide (DMF) solution of
tris(4-hydroxyphenyl)phosphine oxide (2) and poly(benzyl
ether) dendritic bromide 3(Gn[TEG]) was stirred at 70 °C in
the presence of potassium carbonate and a catalytic amount of
18-crown-6 under an argon atmosphere. The obtained dendritic
phosphine oxide 4(Gn[TEG]) was reduced by trichlorosilane
in degassed xylene at 120 °C to afford dendritic phosphine
1(Gn[TEG]). Both transformations were carried out in fair
yields in all generations.
By the use of 1(Gn[TEG]), we performed gold(I)-catalyzed
hydration of phenylacetylene under acidic conditions. After the
preparation of phosphineÍgold(I) catalyst (0.5 mol %) by treat-
ment of AuCl(SMe2) with 1(Gn[TEG]) and AgOTf (except for
Entries 1 and 3), hydration of phenylacetylene was carried out
at 80 °C in the presence of TfOH (except for Entry 5) (Table 1).
We first performed hydration of phenylacetylene through the
use of the first-generation dendritic catalyst. Although dendritic

K. Fujita et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 2 (2009)
263
Table 3. Hydration Using Various Generation 1(Gn[TEG])Í
Gold(I) Catalysts
tography. Reagents and dry solvents were commercially available
and were used as received. The dendritic bromides 3(Gn[TEG])
(n = 1Í3), which had been reported by McKeown et al.15 were
prepared by our previously reported synthetic procedures.16
3(G4[TEG]) was newly synthesized from 3(G3[TEG]) via the
fourth-generation dendritic alcohol G4[TEG]ÍOH 5. Tris(4-
hydroxyphenyl)phosphine oxide (2) was prepared according to
the literature method.17
Membrane separation was carried through the use of AS ONE
pump tubing (7520-50) and PALL MinimateTM (tangential flow
filtration capsule) with a molecular weight cut-off (MWCO) of 650
Dalton.
IR spectra were recorded on a Thermo Electron Nicolet Nexus
470 FT-IR spectrophotometer. 1H, 13C, and 31P NMR spectra
were measured with a JEOL LA-500 spectrometer (1H: 500 MHz,
13C: 125 MHz, and 31P: 202 MHz) or a JEOL JNM-LA400WB
spectrometer (1H: 400 MHz, 13C: 100 MHz, and 31P: 162 MHz). 1H
and 13C NMR chemical shifts were recorded as ppm downfield
from TMS as an internal standard. 31P NMR data are given relative
to external 85% H3PO4. Signal patterns are indicated as follows:
brs, broad singlet; s, singlet; d, doublet; t, triplet; q, quartet; m,
multiplet. Coupling constants (J) are given in hertz (Hz). Mass
spectra were measured with JEOL MS 600H (FAB; matrix: 3-
nitrobenzyl alcohol) and Shimadzu AXIMA-CFR (MALDI-TOF;
matrix: 2,5-dihydroxybenzoic acid) mass spectrometers. Micro-
analyses were performed with a CE Instruments EA1110 elemental
analyzer.
1(Gn[TEG]) + AuCl(SMe2)
(0.5 mol %)
O
HO
HO
TfOH
H2O, rt, 14 h
Gn
G1
93
G2
G3
86
G4
89
Yielda)/%
89
1
a) Determined by integration of H NMR absorptions referred
to an internal standard.
Table 4. Catalyst Recycling in Hydration
1(G4[TEG]) + AuCl(SMe2)
O
(0.5 mol %)
X
X
TfOH
H2O, rt, 14 h
Yielda)/%
X
First
Second
Third
Fourth
CH2OH
CO2H
89
80
90
86
1
93
93
91
88
a) Determined by integration of H NMR absorptions referred
to an internal standard.
Synthesis of the Fourth-Generation Dendritic Alcohol 5.
A
dry acetone solution (20 mL) of 3,5-dihydroxybenzyl alcohol
(106 mg, 0.756 mmol), 3(G3[TEG]) (3.416 g, 1.623 mmol), anhy-
drous potassium carbonate (281 mg, 2.03 mmol), and 18-crown-6
(36 mg, 0.136 mmol) was refluxed for 14 h under an argon
atmosphere. The reaction mixture was filtered with Celite to
remove inorganic salts, and the filtrate was evaporated to dryness.
The residue was purified with silica gel column chromatography
(ethyl acetate/methanol = 5/1 as eluent) to obtain the fourth-
generation dendritic alcohol 5 (2.891 g, 0.6902 mmol) in a 91%
yield.
often used to recover the dendritic catalysts.12 In this study, we
examined the recycling of the dendritic catalyst in the hydration
of 4-pentyn-1-ol and 4-pentynoic acid using 0.5 mol % of the
fourth-generation 1(G4[TEG])Ígold(I) catalyst (Table 4). After
the hydration had proceeded, the dendritic gold(I) catalyst
was recovered by membrane separation by means of cross-
flow mode nanofiltration of the aqueous reaction mixture.13
The separated dendritic catalyst, which was not filtered, was
subsequently reused. In both cases of 4-pentyn-1-ol and 4-
pentynoic acid, 1(G4[TEG])Ígold(I) catalyst could be used
four times without deactivation.14 By membrane separation
of the dendrimers based on their nano-order size, we could
perform the recycling of the gold(I) catalyst in hydrations of
alkynes without any organic solvent.
3,5-Bis(3,5-bis{3,5-bis[3,5-di(1,4,7,10-tetraoxaundecyl)ben-
zyloxy]benzyloxy}benzyloxy)benzyl Alcohol (5): Colorless oil;
IR (Neat): 2875, 1596, 1449, 1373, 1350, 1322, 1297, 1247, 1173,
1
1145, 1068, 949, 843, 684 cmÕ1; H NMR (400 MHz, CDCl3): ¤
6.68Í6.43 (m, 45H, ArH), 4.97 (brs, 12H, ÍCH2Ar), 4.94 (brs,
16H, ÍCH2Ar), 4.58 (d, J = 12.0 Hz, 2H, ÍCH2Ar), 4.09 (t, J =
4.7 Hz, 32H, OCH2CH2O), 3.82 (t, J = 4.7 Hz, 32H, OCH2-
CH2O), 3.73Í3.62 (m, 96H, OCH2CH2O), 3.53 (t, J = 4.7 Hz,
32H, OCH2CH2O), 3.36 (s, 48H, OCH3); 13C NMR (100 MHz,
CDCl3): ¤ 160.1, 144.0, 139.4, 139.2, 139.1, 106.5, 106.1, 101.6,
101.2, 71.9, 70.8, 70.6, 70.5, 70.1, 70.0, 69.7, 67.5, 59.0; Anal.
Calcd for C217H316O79: C, 62.22; H, 7.60%. Found: C, 61.85; H,
7.57%.
Synthesis of the Fourth-Generation Dendritic Bromide
(3(G4[TEG])). To a dry THF solution (25 mL) of the fourth-
generation dendritic alcohol 5 (2.598 g, 0.6202 mmol) and carbon
tetrabromide (713 mg, 2.15 mmol) was added triphenylphosphine
(567 mg, 2.16 mmol), and the reaction mixture was stirred at 40 °C
for 2 h under an argon atmosphere. The reaction mixture was
filtered with Celite, and the filtrate was evaporated to dryness. The
residue was purified with silica gel column chromatography (ethyl
acetate/methanol = 3/1 as eluent) to obtain the fourth-generation
dendritic bromide 3(G4[TEG]) (2.415 g, 0.5677 mmol) in a 92%
yield.
Conclusion
We have newly synthesized water-soluble phosphine core
dendrimer having tri(ethylene glycol) units at the peripheral
layer. By the use of this dendritic phosphine ligand, we
prepared water-soluble dendritic phosphineÍgold(I) catalyst,
which caused the efficient hydration of alkynes. Furthermore,
by membrane separation of the dendrimer based on nano-
filtration of the reaction mixture, the dendritic phosphineÍ
gold(I) catalyst was recovered and then subsequently reused.
The immobilization of transition metal on water-soluble
dendritic ligand appears to make possible the aqueous media
catalyst-recyclable transformation.
Experimental
General. Kieselgel 60 F254 (Merck) was used for TLC, and
Wakogel C-300 (Wako) was used for silica gel column chroma-

264
Bull. Chem. Soc. Jpn. Vol. 82, No. 2 (2009)
Water-Soluble Phosphine Core Dendrimer
1350, 1323, 1297, 1174, 1144, 1120, 1069 cmÕ1 1H NMR
3,5-Bis(3,5-bis{3,5-bis[3,5-di(1,4,7,10-tetraoxaundecyl)ben-
zyloxy]benzyloxy}benzyloxy)benzyl Bromide (3(G4[TEG])):
Colorless oil; IR (Neat): 2875, 1595, 1449, 1374, 1349, 1322,
;
1297, 1247, 1173, 1145, 1068, 949, 843, 684 cmÕ1 1H NMR
(400 MHz, CDCl3): ¤ 6.69Í6.44 (m, 45H, ArH), 4.97 (brs, 12H,
ÍCH2Ar), 4.95 (brs, 16H, ÍCH2Ar), 4.40 (s, 2H, ÍCH2Ar), 4.10 (t,
J = 4.8 Hz, 32H, OCH2CH2O), 3.83 (t, J = 4.7 Hz, 32H, OCH2-
CH2O), 3.72Í3.63 (m, 96H, OCH2CH2O), 3.53 (t, J = 4.6 Hz,
32H, OCH2CH2O), 3.36 (s, 48H, OCH3); 13C NMR (100 MHz,
CDCl3): ¤ 160.0, 139.8, 139.0, 138.9, 106.4, 101.5, 101.0, 71.9,
70.7, 70.6, 70.5, 70.0, 69.9, 69.6, 67.4, 59.0; Anal. Calcd for
;
(500 MHz, CDCl3): ¤ 7.61 (dd, J = 11.5, 8.0 Hz, 6H, ArH), 7.06
(dd, J = 9.0, 1.5 Hz, 6H, ArH), 6.71 (d, J = 2.0 Hz, 6H, ArH),
6.67 (d, J = 2.5 Hz, 12H, ArH), 6.60 (t, J = 2.5 Hz, 3H, ArH),
6.58 (d, J = 2.0 Hz, 24H, ArH), 6.54 (t, J = 2.5 Hz, 6H, ArH),
6.44 (t, J = 2.5 Hz, 12H, ArH), 5.02 (s, 6H, OCH2Ar), 4.97 (s,
12H, OCH2Ar), 4.95 (s, 24H, OCH2Ar), 4.10 (t, J = 4.5 Hz, 48H,
OCH2CH2O), 3.83 (t, J = 4.5 Hz, 48H, OCH2CH2O), 3.74Í3.69
(m, 48H, OCH2CH2O), 3.68Í3.62 (m, 96H, OCH2CH2O), 3.53
(dd, J = 5.5, 3.0 Hz, 48H, OCH2CH2O), 3.36 (s, 72H, OCH3);
13C NMR (125 MHz, CDCl3): ¤ 161.4, 160.1, 160.0, 138.9, 138.5,
133.8 (2JCÍP = 10 Hz), 114.3 (3JCÍP = 13 Hz), 106.5, 106.0, 101.5,
101.4, 101.0, 71.8, 70.7, 70.55, 70.46, 70.0, 69.9, 69.6, 67.4, 58.9;
C
217H315O78Br: C, 61.31; H, 7.47; Br, 1.88%. Found: C, 60.99; H,
7.36; Br, 1.59%.
Synthesis of Dendritic Phosphine Oxide 4(Gn[TEG]) from 2
and 3(Gn[TEG]): Typical Procedure. A dry DMF solution
(10 mL) of tris(4-hydroxyphenyl)phosphine oxide (2) (23 mg,
31P NMR (202 MHz, CDCl3):
333H477O118P: C, 62.49; H, 7.53%. Found: C, 62.72; H, 7.53%.
Tris{4-[3,5-bis(3,5-bis{3,5-bis[3,5-di(1,4,7,10-tetraoxaundec-
¤
28.4; Anal. Calcd for
C
0.070 mmol),
the
fourth-generation
dendritic
bromide
yl)benzyloxy]benzyloxy}benzyloxy)benzyloxy]phenyl}phosphine
Oxide (4(G4[TEG])): Colorless oil; IR (Neat): 2875, 1596, 1449,
1373, 1349, 1323, 1297, 1248, 1173, 1149, 1069, 949, 844,
684 cmÕ1; 1H NMR (400 MHz, CDCl3): ¤ 7.64 (t, J = 12.0 Hz, 6H,
ArH), 7.09 (d, J = 7.0 Hz, 6H, ArH), 6.75Í6.42 (m, 135H, ArH),
5.02 (brs, 6H, ÍCH2Ar), 4.98 (brs, 12H, ÍCH2Ar), 4.96 (brs, 24H,
ÍCH2Ar), 4.92 (brs, 48H, ÍCH2Ar), 4.08 (t, J = 4.2 Hz, 96H,
OCH2CH2O), 3.81 (t, J = 5.0 Hz, 96H, OCH2CH2O), 3.71Í3.61
(m, 288H, OCH2CH2O), 3.51 (t, J = 4.7 Hz, 96H, OCH2CH2O),
3.34 (s, 144H, OCH3); 13C NMR (100 MHz, CDCl3): ¤ 160.14,
3(G4[TEG]) (0.988 g, 0.232 mmol), anhydrous potassium car-
bonate (49 mg, 0.36 mmol), and 18-crown-6 (20 mg, 0.076 mmol)
was stirred at 70 °C for 4 h under an argon atmosphere. The
reaction mixture was filtered with Celite to remove inorganic salts,
and the filtrate was evaporated to dryness. The residue was purified
with silica gel column chromatography (ethyl acetate/metha-
nol = 3/1 as eluent) to obtain 4(G4[TEG]) (0.860 g, 0.0670 mmol)
in a 96% yield.
Tris{4-[3,5-di(1,4,7,10-tetraoxaundecyl)benzyloxy]phenyl}-
phosphine Oxide (4(G1[TEG])): Colorless oil; IR (CH2Cl2)
2876, 1596, 1501, 1450, 1294, 1249, 1176, 1119, 834, 672,
543 cmÕ1 1H NMR (500 MHz, CDCl3): ¤ 7.56 (dd, J = 11.5,
;
160.08, 139.1, 139.0, 133.9 (2JCÍP = 11 Hz), 114.8 (3JCÍP
=
13 Hz), 106.7, 106.5, 106.1, 101.5, 101.1, 71.9, 70.8, 70.6, 70.5,
67.0, 69.6, 67.5, 59.0; 31P NMR (162 MHz, CDCl3): ¤ 28.9; Anal.
Calcd for C669H957O238P: C, 62.59; H, 7.51%. Found: C, 62.49; H,
7.44%.
8.0 Hz, 6H, ArH), 7.00 (d, J = 8.0 Hz, 6H, ArH), 6.58 (s, 6H,
ArH), 6.45 (s, 3H, ArH), 5.01 (s, 6H, OCH2Ar), 4.11 (t,
J = 4.5 Hz, 12H, OCH2CH2O), 3.85 (t, J = 4.5 Hz, 12H, OCH2-
CH2O), 3.74 (t, J = 4.5 Hz, 12H, OCH2CH2O), 3.68 (t, J = 4.5 Hz,
12H, OCH2CH2O), 3.66 (t, J = 4.5 Hz, 12H, OCH2CH2O), 3.55 (t,
J = 4.5 Hz, 12H, OCH2CH2O), 3.37 (s, 18H, OCH3); 13C NMR
(125 MHz, CDCl3): ¤ 161.3 (4JCÍP = 3 Hz), 160.1, 138.5, 133.8
(2JCÍP = 11 Hz), 124.7 (1JCÍP = 110 Hz), 114.7 (3JCÍP = 13 Hz),
106.0, 101.0, 71.8, 70.7, 70.55, 70.46, 69.8, 69.5, 67.4, 58.9;
31P NMR (202 MHz, CDCl3): ¤ 28.5; FABMS for C81H117O28P
m/z: Calcd: 1569.8 [M]+; Found: 1569; Anal. Calcd for
C81H117O28P: C, 61.97; H, 7.51%. Found: C, 61.64; H, 7.44%.
Tris(4-{3,5-bis[3,5-di(1,4,7,10-tetraoxaundecyl)benzyloxy]-
benzyloxy}phenyl)phosphine Oxide (4(G2[TEG])): Colorless
oil; IR (CH2Cl2) 2875, 1596, 1473, 1458, 1449, 1375, 1350, 1296,
1248, 1175, 1119, 1070, 844 cmÕ1; 1H NMR (500 MHz, CDCl3): ¤
7.59 (dd, J = 11.5, 8.8 Hz, 6H, ArH), 7.03 (dd, J = 8.8, 2.0 Hz,
6H, ArH), 6.65 (d, J = 2.0 Hz, 6H, ArH), 6.59 (d, J = 2.0 Hz, 12H,
ArH), 6.55 (t, J = 2.0 Hz, 3H, ArH), 6.44 (t, J = 2.0 Hz, 6H, ArH),
5.01 (s, 6H, OCH2Ar), 4.95 (s, 12H, OCH2Ar), 4.11 (t, J = 4.5 Hz,
24H, OCH2CH2O), 3.84 (t, J = 4.5 Hz, 24H, OCH2CH2O), 3.74Í
3.70 (m, 24H, OCH2CH2O), 3.69Í3.63 (m, 48H, OCH2CH2O),
3.54 (dd, J = 6.5, 4.3 Hz, 24H, OCH2CH2O), 3.36 (s, 36H, OCH3);
13C NMR (125 MHz, CDCl3): ¤ 161.5, 160.13, 160.10, 139.0,
138.6, 134.0 (2JCÍP = 11 Hz), 124.8 (1JCÍP = 109 Hz), 114.8
(3JCÍP = 14 Hz), 106.4, 106.1, 101.6, 101.1, 71.9, 70.8, 70.63,
70.55, 70.02, 69.97, 69.7, 67.5, 59.0; 31P NMR (202 MHz, CDCl3):
¤ 28.6; MALDI-TOFMS for C165H237O58P m/z: Calcd: 3180.5
[M + H]+; Found: 3180.5; Anal. Calcd for C165H237O58P: C,
62.32; H, 7.53%. Found: C, 62.15; H, 7.52%.
Synthesis of Dendritic Phosphine 1(Gn[TEG]) from 4(Gn-
[TEG]): Typical Procedure.
To a solution of 4(G2[TEG])
(1.827 g, 0.575 mmol) in degassed xylene (11 mL) was added
triethylamine (288.4 mg, 2.85 mmol) and trichlorosilane (309 mg,
2.28 mmol) at room temperature with stirring. The mixture was
stirred at 120 °C for 16 h under an argon atmosphere. To a reaction
mixture was added dichloromethane (20 mL), water (1 mL), and
sodium hydrogen carbonate (ca. 0.7 g), and the thus obtained
mixture was stirred at room temperature for 2 h. After the removal
of water by the addition of magnesium sulfate (ca. 2 g), the mixture
was filtered with Celite to remove inorganic salts, and the filtrate
was evaporated to dryness. The residue was purified with silica gel
column chromatography (dichloromethane/methanol = 10/1 as
eluent) to obtain 1(G2[TEG]) (1.751 g, 0.553 mmol) in a 97%
yield.
Tris{4-[3,5-di(1,4,7,10-tetraoxaundecyl)benzyloxy]phenyl}-
phosphine (1(G1[TEG])): Yellow oil; IR (CH2Cl2) 2875, 1594,
1496, 1449, 1350, 1293, 1176, 1109, 1072, 829, 530 cmÕ1
;
1H NMR (500 MHz, C6D6): ¤ 7.42 (dd, J = 9.0, 7.5 Hz, 6H, ArH),
6.89 (d, J = 7.5 Hz, 6H, ArH), 6.65 (d, J = 2.0 Hz, 6H, ArH),
6.54 (t, J = 2.0 Hz, 3H, ArH), 4.69 (s, 6H, OCH2Ar), 3.78 (t,
J = 5.0 Hz, 12H, OCH2CH2O), 3.53 (t, J = 5.0 Hz, 12H, OCH2-
CH2O), 3.48Í3.44 (m, 36H, OCH2CH2O), 3.34 (dd, J = 5.5,
4.0 Hz, 12H, OCH2CH2O), 3.12 (s, 18H, OCH3); 13C NMR
(125 MHz, C6D6): ¤ 160.9, 159.9, 139.8, 135.6 (2JCÍP = 21 Hz),
130.2 (1JCÍP = 9 Hz), 115.6 (3JCÍP = 7 Hz), 106.4, 101.5, 72.4,
71.14, 71.05, 70.9, 70.1, 69.9, 67.7, 58.7; 31P NMR (202 MHz,
C6D6): ¤ Õ9.7; FABMS for C81H117O27P m/z: Calcd: 1553.8 [M]+;
Found: 1553.8; Anal. Calcd for C81H117O27P: C, 62.61; H, 7.59%.
Found: C, 62.61; H, 7.50%.
Tris[4-(3,5-bis{3,5-bis[3,5-di(1,4,7,10-tetraoxaundecyl)ben-
zyloxy]benzyloxy}benzyloxy)phenyl]phosphine Oxide (4(G3-
[TEG])): Colorless oil; IR (CH2Cl2) 2876, 1596, 1449, 1374,
Tris(4-{3,5-bis[3,5-di(1,4,7,10-tetraoxaundecyl)benzyloxy]-

K. Fujita et al.
Bull. Chem. Soc. Jpn. Vol. 82, No. 2 (2009)
265
benzyloxy}phenyl)phosphine (1(G2[TEG])): Colorless oil; IR
(CH2Cl2) 2875, 1595, 1496, 1449, 1374, 1350, 1323, 1296, 1243,
Catalyst Recycling Experiment. The dendritic phosphineÍ
gold(I) complex was prepared by treatment of AuCl(SMe2)
(0.015 mmol) with the fourth-generation dendritic phosphine
1(G4[TEG]) (0.015 mmol) at room temperature in water (3 mL)
under an argon atmosphere, and the mixture was stirred for
0.5 h. To the resulting solution of the dendritic gold(I) complex
1(G4[TEG])ÍAuCl was added an alkyne (3.0 mmol) and CF3SO3H
(0.24 mmol), and the reaction mixture was stirred at room
temperature for 14 h. Under membrane separation system,13 the
aqueous reaction mixture, which was diluted with water (40 mL),
was concentrated to 2Í3 mL by cross-flow mode nanofiltration by
pumping the reaction mixture (repeated 4 times). The concentrated
reaction mixture, which contained the dendritic phosphineÍgold(I)
catalyst, was reused for another hydration by employing an alkyne
(3.0 mmol) and CF3SO3H (0.24 mmol).
1
1175, 1144, 1069, 949, 845 cmÕ1; H NMR (500 MHz, C6D6): ¤
7.44 (t, J = 8.0 Hz, 6H, ArH), 6.93 (d, J = 8.0 Hz, 6H, ArH), 6.77
(d, J = 2.5 Hz, 6H, ArH), 6.74 (t, J = 2.5 Hz, 3H, ArH), 6.69 (d,
J = 2.5 Hz, 12H, ArH), 6.56 (t, J = 2.5 Hz, 6H, ArH), 4.77 (s,
12H, OCH2Ar), 4.74 (s, 6H, OCH2Ar), 3.83 (t, J = 5.0 Hz, 24H,
OCH2CH2O), 3.56 (t, J = 5.0 Hz, 24H, OCH2CH2O), 3.50Í3.45
(m, 72H, OCH2CH2O), 3.35 (dd, J = 5.5, 4.0 Hz, 24H, OCH2-
CH2O), 3.13 (s, 36H, OCH3); 13C NMR (125 MHz, C6D6): ¤
160.85, 160.78, 159.9, 140.0, 139.9, 135.6 (2JCÍP = 21 Hz), 128.5,
115.6 (3JCÍP = 7 Hz), 106.9, 106.4, 102.2, 101.5, 72.4, 71.1, 71.0,
70.9, 70.2, 70.1, 69.9, 67.8, 53.4; 31P NMR (202 MHz, C6D6): ¤
Õ9.6; MALDI-TOFMS for C165H237O57P m/z: Calcd: 3163.55
[M + H]+; Found: 3163.29; Anal. Calcd for C165H237O57P: C,
62.64; H, 7.57%. Found: C, 62.88; H, 7.58%.
Tris[4-(3,5-bis{3,5-bis[3,5-di(1,4,7,10-tetraoxaundecyl)ben-
zyloxy]benzyloxy}benzyloxy)phenyl]phosphine (1(G3[TEG])):
Yellow oil; IR (CH2Cl2) 2875, 1595, 1496, 1449, 1373, 1350,
1323, 1297, 1244, 1175, 1145, 1069, 950, 845, 684 cmÕ1; 1H NMR
(400 MHz, CDCl3): ¤ 7.26 (t, J = 8.1 Hz, 6H, ArH), 6.97 (d,
J = 8.1 Hz, 6H, ArH), 6.70 (d, J = 2.1 Hz, 6H, ArH), 6.67 (d,
J = 2.1 Hz, 12H, ArH), 6.58 (d, J = 2.3 Hz, 27H, ArH), 6.54
(brs, 6H, ArH), 6.44 (t, J = 2.2 Hz, 12H, ArH), 4.96 (brs, 42H,
ÍCH2Ar), 4.10 (t, J = 4.8 Hz, 48H, OCH2CH2O), 3.82 (t,
J = 4.9 Hz, 48H, OCH2CH2O), 3.74Í3.62 (m, 144H, OCH2CH2O),
3.53 (dd, J = 5.5, 3.0 Hz, 48H, OCH2CH2O), 3.35 (s, 72H, OCH3);
13C NMR (100 MHz, CDCl3): ¤ 160.1, 160.0, 159.2, 139.04,
139.00, 138.6, 134.9 (2JCÍP = 20 Hz), 114.9 (3JCÍP = 7.4 Hz),
101.5, 101.1, 71.8, 70.7, 70.5, 70.4, 69.9, 69.6, 67.4, 60.3,
58.9; 31P NMR (162 MHz, CDCl3): ¤ Õ8.8; Anal. Calcd for
The filtered solution was concentrated under reduced pressure,
and the chemical yield of the hydration product was determined
1
by the integration of H NMR absorption referred to an internal
standard.
This work was supported by Industrial Technology Research
Grant Program in ’04 from New Energy and Industrial
Technology Development Organization (NEDO) of Japan.
Supporting Information
Figure showing membrane separation. This material is available
free of charge on the Web at: http://www.csj.jp/journals/bcsj/.
References
1
a) C.-J. Li, L. Chen, Chem. Soc. Rev. 2006, 35, 68. b)
C
333H477O117P: C, 62.66; H, 7.53%. Found: C, 62.76; H, 7.54%.
Tris{4-[3,5-bis(3,5-bis{3,5-bis[3,5-di(1,4,7,10-tetraoxaundec-
Aqueous-Phase Organometallic Catalysis, ed. by B. Cornils, W. A.
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yl)benzyloxy]benzyloxy}benzyloxy)benzyloxy]phenyl}phosphine
(1(G4[TEG])): Colorless oil; IR (Neat): 2876, 1595, 1449, 1373,
1349, 1323, 1297, 1245, 1174, 1145, 1069, 949, 843, 684 cmÕ1
;
1H NMR (400 MHz, CDCl3): ¤ 6.9 (d, J = 8.8 Hz, 6H, ArH), 6.74Í
6.42 (m, 141H, ArH), 4.95 (brs, 42H, ÍCH2Ar), 4.92 (brs, 48H,
ÍCH2Ar), 4.07 (t, J = 4.7 Hz, 96H, OCH2CH2O), 3.80 (t, J =
4.7 Hz, 96H, OCH2CH2O), 3.70Í3.60 (m, 288H, OCH2CH2O),
3.51 (t, J = 4.7 Hz, 96H, OCH2CH2O), 3.34 (s, 144H, OCH3);
13C NMR (100 MHz, CDCl3): ¤ 160.2, 160.1, 160.0, 139.1, 139.0,
135.0 (2JCÍP = 21 Hz), 114.9 (3JCÍP = 7.2 Hz), 106.5, 106.0, 101.5,
101.1, 71.8, 70.7, 70.5, 70.4, 69.9, 69.6, 67.4, 60.3, 58.9; 31P NMR
(162 MHz, CDCl3): ¤ Õ8.3; Anal. Calcd for C669H957O237P: C,
62.66; H, 7.52%. Found: C, 62.59; H, 7.21%.
2
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Hydration of Alkynes: General Procedure. The dendritic
phosphineÍgold(I) complex was prepared by treatment of
AuCl(SMe2) (0.015 mmol) with 1(Gn[TEG]) (0.015 mmol) at
room temperature in aqueous methanol (3 mL; MeOH:H2O = 9:1
(v/v)) under an argon atmosphere. After stirring for 0.5 h, AgOTf
was subsequently added, and the mixture was stirred for 0.5 h at
room temperature. To the resulting solution of the dendritic gold(I)
complex 1(Gn[TEG])ÍAuOTf was added an alkyne (3.0 mmol)
and CF3SO3H (0.24 mmol), and the reaction mixture was stirred at
80 °C for 2Í5 h. After the addition of saturated aqueous solution of
sodium hydrogen carbonate, the mixture was extracted with diethyl
ether (15 mL © 3). The organic layer was washed with brine and
was dried over magnesium sulfate. After removal of the organic
solvent under reduced pressure, the chemical yield of the hydration
3
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7
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9