Synthesis of calixarene-based bis(iminophosphoranes) and their use in Suzuki-Miyaura cross-coupling

Article abstract of DOI:10.1002/ejoc.201200082

Calix[4]arene-derived bis(iminophosphoranes) have been synthesised and assessed in palladium-catalysed cross-couplings between phenylboronic acid and aryl bromides orchlorides. TOFs of up to 35100 mol(ArPh formed) mol(Pd) ^-1 h^-1were

Full text of DOI:10.1002/ejoc.201200082

FULL PAPER
DOI: 10.1002/ejoc.201200082
Synthesis of Calixarene-Based Bis(iminophosphoranes) and Their Use in
Suzuki–Miyaura Cross-Coupling
Laure Monnereau,[a] David Sémeril,*[a] and Dominique Matt*[a]
Keywords: Calixarenes / Iminophosphoranes / Cross-coupling / Palladium
Calix[4]arene-derived bis(iminophosphoranes) have been
synthesised and assessed in palladium-catalysed cross-cou-
plings between phenylboronic acid and aryl bromides or
gands showed higher activities than the parent calixarene–
diphosphanes. Their relatively good performances possibly
arise from their ability to generate chelated intermediates in
chlorides. TOFs of up to 35100 mol(ArPh formed)mol(Pd)–1 h–1 highly crowded metal environments, which incidentally fa-
were observed in the reaction with 4-bromoanisole. The li-
cilitates the reductive elimination step.
Introduction
Results and Discussion
The bis(iminophosphoranyl)calix[4]arenes 2–6 were pre-
pared through Staudinger condensations[30] of calixarenyl-
phosphane 1 with the appropriate aryl azides (Scheme 1).
The azides themselves were obtained by treatment of substi-
tuted anilines with freshly prepared TfN3 (Tf = CF3SO2)
in the presence of CuSO4 and NEt3.[31] The products were
characterised by elemental analyses, mass spectrometry
(MALDI-TOF) and NMR spectroscopy. Each mass spec-
trum displays a strong peak corresponding to the expected
[M + H]+ ion. In the 31P NMR spectra the phosphorus
atoms appear in each case as a singlet in the δ = –10 to
+1 ppm range. The conical structure of the calixarene unit
was maintained in each case, as deduced from the 13C
NMR spectra, all of which display ArCH2Ar signals at δ ≈
Organic imines are commonly used as ligands in homo-
geneous catalysis, in particular for carbon–carbon bond-
forming reactions.[1–8] In comparison, the related imino-
phosphoranes R3P=NR, also termed phosphazenes, have
only rarely been employed for the preparation of transition-
metal-based catalysts.[9–16] This is mainly due to the nature
of the P=N bond, which involves a zwitterionic contri-
bution, thus making stabilisation of coordinated metal
atoms in low oxidation states difficult.[17,18] However, recent
studies have shown that functionalised iminophosphoranes
capable of forming chelate complexes can be used both in
carbon–carbon and carbon–heteroatom bond forma-
tion.[19–26]
We have recently described conical calix[4]arenes in
which two distal phosphanyl groups are attached at the up-
per rim of the macrocycle and have shown that such phos-
phanes, when associated with palladium, could function as
efficient cross-coupling catalysts.[27,28] The good perform-
ances of the catalysts were shown to be related to the size
and structural properties of the calixarene backbone. As a
logical extension of these studies, we embarked on the syn-
thesis of the corresponding iminophosphorane derivatives,
which were assessed in Suzuki–Miyaura cross-couplings.
The five ligands reported in this study are the first bis-
(iminophosphoranes) based on a calix[4]arene skeleton. It
should be noted that an iminophosphorane based on a
closely related resorcin[4]arene has been reported re-
cently.[29]
1
31 ppm.[32] The H NMR spectra are consistent with C2v-
symmetrical compounds. The bis(iminophosphoranes) were
only moderately air-stable, contact with air leading to the
the expected hydrolysis products – namely the correspond-
ing aniline and the bis(phosphane oxide) 7. They were
therefore stored under nitrogen.
[a] Laboratoire de Chimie Inorganique Moléculaire et Catalyse,
Institut de Chimie UMR 7177 CNRS, Université de Strasbourg,
67008 Strasbourg Cedex, France
E-mail: dsemeril@unistra.fr
dmatt@unistra.fr
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201200082.
Scheme 1. Synthesis of bis(iminophosphoranes) 2–6.
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Eur. J. Org. Chem. 2012, 2786–2791
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Calixarene-Based Bis(iminophosphoranes) in Suzuki–Miyaura Cross-Coupling
dergoes a fast balance-wheel motion centred on the calixar-
ene axis (Scheme 3).
The five bis(iminophosphoranes) 2–6 were assessed in
palladium-catalysed Suzuki–Miyaura couplings (Scheme 4).
The catalytically active species were generated in situ by
mixing [Pd(OAc)2] and the iminophosphoranes.
The above ligands were found to be suitable for metal
binding. For example, upon treatment of 2 (Scheme 2) with
2 equiv. of [AuCl(THT)] (THT = tetrahydrothiophene), the
dinuclear complex 8 was formed quantitatively. In the cor-
responding 31P NMR (C6D6) spectrum, the phosphorus
atoms appear as a singlet at δ = 28.6 ppm (cf. δ = –9.2 ppm
for the free ligand).
Scheme 4. Suzuki–Miyaura cross-coupling.
To determine optimal catalytic conditions, we first inves-
tigated the reaction between 4-bromoanisole and phenyl-
boronic acid in the presence of bis(iminophosphorane) 3
(Table 1). With Cs2CO3 as base, higher levels of conversion
were observed at 100 °C in dioxane than at 130 °C in DMF
(Table 1, Entries 1 and 2). Replacement of the base by NaH
slightly increased the level of conversion (Table 1, Entries 2
and 6). The other bases tested – K2CO3, KOH and NEt3 –
did not improve the levels of conversion (Table 1, Entries 3–
5). As expected, reduction of the temperature decreased the
reaction rate (Table 1, Entries 6–8). We also found that the
kinetics were not affected by use of more than 1 equiv. of
ligand relative to palladium (Table 1, Entries 9–11).
Scheme 2. Synthesis of the digold complex 8.
Finally, we observed that the absence of any ligand dras-
Whereas the above reaction led to a single product, the tically reduced the catalytic outcome (Table 2, Entry 1).
reaction between 6 and [PdCl2(MeCN)2] (1 equiv.) gave a This was also the case when the catalytic runs were carried
mixture of complexes that could not be separated. The 31P out in the presence of palladium associated either with
NMR spectrum of the crude reaction mixture revealed the bis(phosphane oxide) 7 or with 2-methoxyaniline, two prod-
presence of three peaks at δ = 34.2, 31.0 and 30.6 ppm, all ucts that should be formed upon hydrolysis of 5 during ca-
consistent with the presence of coordinated palladium.[33] talysis (Table 2, Entries 4 and 5).
Unreacted iminophosphorane was not detected. The mass
The bis(iminophosphoranes) 2–6 were then tested in pal-
spectrum of the reaction mixture showed a peak at m/z = ladium-catalysed Suzuki–Miyaura cross-coupling reactions
1573.41, corresponding to the cation [PdCl2(6) + H]+ (see of aryl bromides under the optimised conditions (NaH as
Scheme 2 in the Supporting Information) and therefore sug- base, dioxane, 100 °C, 1 h). An ArBr/Pd ratio of 10000, cor-
gesting the formation of a [PdCl2(6)] complex with a che- responding to a palladium loading of 0.01 mol-%, was ap-
lated structure. The ability of 6 to form chelate complexes plied for the runs (Table 3). Under these conditions, even
was formally demonstrated by treatment with AgBF4 for the hindered 2-bromoanisole and 2-bromotoluene, levels
(Scheme 3), which quantitatively gave complex 9 (see the of conversion Ͼ51% were obtained within 1 h. As expected,
1
Experimental Section). The H and 31P NMR spectra of 9 increasing the reaction time to 2 h led to almost full conver-
are consistent with a complex of C2v-symmetrical structure. sion. The highest level of conversion was observed in the
It is likely that the apparent C2v symmetry reflects a dy- arylation of 4-bromoanisole in the presence of bis(imino-
namic structure in which the linear N–Ag–N system un- phosphorane) 6, with p-anisole substituents (Table 3, En-
Scheme 3. Synthesis of the chelate complex 9 and proposed molecular motion of 9.
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FULL PAPER
Table 1. Suzuki–Miyaura cross-coupling between 4-bromoanisole and phenylboronic acid – search for optimal conditions in the presence
of bis(iminophosphorane) 3.[a]
Entry
Solvent
Base
[Pd(OAc)2] [%]
3 [mol-%]
T [°C]
Conversion [%]
1
2
3
4
5
6
7
8
9
DMF
Cs2CO3
Cs2CO3
K2CO3
KOH
NEt3
NaH
NaH
NaH
NaH
NaH
NaH
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
1.0
130
100
100
100
100
100
80
34.6
96.6
88.8
21.4
4.6
99.2
73.0
34.3
57.3
54.9
55.4
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
dioxane
65
0.01
0.01
0.01
0.01
0.015
0.02
100
100
100
10
11
[a] [Pd(OAc)2], bis(iminophosphorane) 3, 4-bromoanisole (0.25 mmol), PhB(OH)2 (0.061 g, 0.50 mmol), NaH (60% dispersion in mineral
oil, 0.040 g, 1.0 mmol), decane (0.050 mL), solvent (0.75 mL), 1 h. The levels of conversion were determined by GC, with calibrations
based on decane.
Table 2. Suzuki–Miyaura cross-coupling between 4-bromotoluene
and phenylboronic acid – comparison with other ligands.[a]
Table 3. Palladium-catalysed Suzuki–Miyaura cross-couplings of
aryl bromides in the presence of bis(iminophosphoranes) 2–6 and
with an ArBr/Pd ratio of 10000:1.[a]
Entry
Ligand
Conversion [%]
1
2
3
4
5
none
1 (1 equiv.)
16.7
35.4
56.3
30.7
27.3
5 (1 equiv.)
7 (1 equiv.)
o-MeOC6H4NH2 (2 equiv.)
[a] [Pd(OAc)2] (5ϫ10–5 mmol, 0.01 mol-%), ligand, 4-bromotolu-
ene (0.5 mmol), PhB(OH)2 (0.122 g, 1.0 mmol), NaH (60% disper-
sion in mineral oil, 0.040 g, 1.0 mmol), dioxane (1.5 mL), decane
(0.050 mL), 100 °C, 1 h. The levels of conversion were determined
by GC, with calibrations based on decane.
try 1). With this substrate, the activity reached 35100 mol-
(ArBr)mol(Pd)–1 h–1 when the palladium loading was re-
duced to 0.001 mol-% (Table 3, Entry 2).
The calixarenyl-iminophosphoranes 3 and 6 were further
tested in arylations of aryl chlorides, which are less reactive
substrates (Table 4). Use of a palladium loading of 1 mol-%
led, after 3 h, to good levels of conversion in the case of
the three activated aryl chlorides 1-chloro-4-nitrobenzene,
4-chloroacetophenone and 4-chlorobenzonitrile (Table 4,
Entries 1–6). Lower levels of conversion were obtained in
arylations of 4-chloroanisole and 4-chlorotoluene (Table 4,
Entries 7–10). We further noted that bis(iminophosphor-
ane) 6 gave slightly higher levels of conversion than ligand
3: whereas 1-chloro-4-nitrobenzene, for example, was 61.4%
converted with 3, its degree of conversion reached 73.1%
with 6 (Table 4, Entries 1 and 2).
The results outlined above clearly show that combina-
tions of [Pd(OAc)2] with the bis(iminophosphoranes) 2–6
functioned as active Suzuki–Miyaura cross-coupling cata-
lysts. In order to rank these ligands, the arylation of 4-bro-
motoluene was carried out with the previously reported
high-performing bis(phosphane) 1, a ligand that quantita-
tively forms chelate complexes upon reaction with PdII. The
[a] [Pd(OAc)2] (5ϫ10–5 mmol, 0.01 mol-%), bis(iminophosphor-
ane) (5ϫ10–5 mmol, 0.01 mol-%), dioxane (1.5 mL), ArBr
(0.5 mmol), PhB(OH)2 (0.092 g, 0.75 mmol), NaH (60% dispersion
in mineral oil) (0.040 g, 1.0 mmol), decane (0.050 mL), 100 °C, 1 h.
The levels of conversion were determined by GC, with calibrations
based on decane. TOFs expressed in mol(ArBr)mol(Pd)–1 h–1.
[b] [Pd(OAc)2] (5ϫ10–6 mmol, 0.001 mol-%), bis(iminophosphor-
ane) (5ϫ10–6 mmol, 0.001 mol-%).
high activities observed with these complexes arise from shown in Table 2, the degree of conversion obtained with
their dynamic behaviour in solution, which periodically the bis(iminophosphorane) 6 reached 61.7% (Table 2, En-
generates increased ligand bite-angle values that impact on try 2 and Table 3 Entry 7). The reason why 6 performs bet-
the reductive elimination step.[28] Significantly, whereas di- ter than 1 is a matter for discussion. According to molecu-
phosphane 1 gave 35.4% conversion under the conditions lar mechanics calculations,[34] the hypothetical chelate com-
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Calixarene-Based Bis(iminophosphoranes) in Suzuki–Miyaura Cross-Coupling
Table 4. Palladium-catalysed Suzuki–Miyaura cross-couplings of formances of these ligands can reasonably be ascribed to
aryl chlorides in the presence of bis(iminophosphoranes) 3 and 6.[a]
the formation of intermediate chelate complexes, which cre-
ates a highly crowded metal environment and incidentally
facilitates the reductive elimination step.
Experimental Section
General Methods: All reactions were performed in Schlenk-type
flasks under dry nitrogen. Solvents were dried by conventional
methods and distilled immediately prior to use. Routine 1H, 13C
and 31P NMR spectra were recorded with an FT Bruker AV-300
instrument. 1H NMR spectra were referenced to residual protiated
solvent (δ = 7.16 ppm for C6D6, 7.26 ppm for CDCl3 and 5.32 ppm
for CD2Cl2), 13C chemical shifts are reported relative to deuterated
solvent (δ = 128.0 ppm for C6D6, 77.16 ppm for CDCl3 and
53.8 ppm for CD2Cl2) and the 31P data are given relative to external
H3PO4. Chemical shifts and coupling constants are reported in
ppm and in Hz, respectively. Infrared spectra were recorded with a
Bruker FT-IR Alpha-P spectrometer. The catalytic solutions were
[a] [Pd(OAc)2] (2.5ϫ10–3 mmol, 1 mol-%), bis(iminophosphorane)
(2.5ϫ10–3 mmol, 1 mol-%), dioxane (0.75 mL), ArCl (0.25 mmol),
PhB(OH)2 (0.061 g, 0.5 mmol), NaH (60% dispersion in mineral
analysed with a Varian 3900 gas chromatograph fitted with a
WCOT fused silica column (25 mϫ0.25 mm, 0.25 μm film thick-
ness). Elemental analyses were performed by the Service de Micro-
analyse, Université de Strasbourg. 5,17-Bis(diphenylphosphanyl)-
25,26,27,28-tetrabenzyloxycalix[4]arene (1),[37] [AuCl(THT)][38] and
[PdCl2(MeCN)2][39] were prepared according to literature pro-
cedures. Aryl azides were synthesized by using TfN3 according to
a procedure developed by Tor.[31] Although we have not experienced
any difficulty in handling TfN3, care should be taken owing to the
potentially explosive natures of certain azides. The reagent should
be kept in solution and used immediately after its synthesis. NMR
spectroscopic data for the formed 1-azido-4-butylbenzene,[31] 1-
azido-4-methoxybenzene,[31] 1-azido-2,6-diisopropylbenzene,[31] 1-
azido-2-methoxybenzene[40] and 2-azido-1,3,5-trimethylbenzene[40]
were in agreement with those reported in the literature.
oil) (0.020 g, 0.5 mmol), decane (0.025 mL), 100 °C. The levels of
conversion were determined by GC, with calibrations based on dec-
ane.
plex [cis-PdCl2(6)] (Figure 1) displays a sterically more
crowded metal environment (presence of six phenyl rings
close to the palladium atom) than in the related chelate
complexes derived from 1. Steric crowding is known to fav-
our the reductive elimination step, namely the coupling of
two cis-positioned aryl moieties.[35,36] However, the ability
of 6 to operate as a ligand with two η1-coordination sites
during catalysis cannot be ruled out at this stage.
General Procedure for the Synthesis of 25,26,27,28-Tetrabenzyloxy-
5,17-bis(aryliminodiphenylphosphoranyl)calix[4]arenes 2–6: A solu-
tion of aryl azide (2.00 mmol) in toluene (10 mL) was added to a
solution of 1 (1.00 mmol) in toluene (10 mL). After the solution
had been stirred at 60 °C for 16 h, the reaction mixture was concen-
trated to dryness under vacuum to afford the bis(iminophosphor-
ane) in quantitative yield.
25,26,27,28-Tetrabenzyloxy-5,17-bis(mesityliminodiphenylphosphor-
anyl)calix[4]arene (2): 1H NMR (300 MHz, C6D6): δ = 7.99–7.93
3
(8 H, arom. CH), 7.41 (d, J = 11.5 Hz, 4 H, arom. CH), 7.30 (d,
3J = 6.3 Hz, 4 H, arom. CH), 7.21–6.97 (arom., 32 H CH), 6.49 (t,
3J = 7.6 Hz, 2 H, arom. CH), 6.06 (d, 3J = 7.6 Hz, 4 H, arom. CH),
5.22 (s, 4 H, CH2Ph), 4.40 (s, 4 H, CH2Ph), 4.21 and 2.70 (AB spin
system, 2J = 13.6 Hz, 8 H, ArCH2Ar), 2.44 (s, 12 H, o-CH3 of
mesityl), 2.32 (s, 6 H, p-CH3 of mesityl) ppm. 13C {1H} NMR
Figure 1. Calculated structure of [cis-PdCl2(6)]. Left: side view;
right: partial view from top.
4
(75 MHz, C6D6): δ = 158.76 (d, JP,C = 3.1 Hz, arom. Cquat.–O),
154.67 (s, arom. Cquat.–O), 145.52–122.89 (arom. C), 77.19 (s,
OCH2Ph), 75.23 (s, OCH2Ph), 31.36 (s, ArCH2Ar), 21.69 (s, o-CH3
of mesityl), 20.70 (s, p-CH3 of mesityl) ppm. 31P {1H} NMR
Conclusions
(121 MHz, C D ): δ = –9.6 (s, PPh ) ppm. IR: ν = 1328 (P=N)
˜
6
6
2
cm–1. MS (MALDI-TOF): m/z = 1419.63 [M + H]+ (expected iso-
topic profile). C98H88N2O4P2 (1419.71): calcd. C 82.91, H 6.25, N
1.97; found C 83.01, H 6.24, N 1.80.
We have described the synthesis of the first bis(imino-
phosphoranes) based on a calix[4]arene platform. In combi-
nations with [Pd(OAc)2] and a base, these ligands efficiently
catalyse Suzuki–Miyaura cross-coupling reactions of aryl
bromides and aryl chlorides. The highest activity [TOF =
35100 mol(ArPh formed)mol(Pd)–1 h–1] was observed in the
25,26,27,28-Tetrabenzyloxy-5,17-bis(2,6-diisopropylphenylimino-
diphenylphosphoranyl)calix[4]arene (3): 1H NMR (300 MHz, C6D6):
3
δ = 7.83–7.78 (8 H, arom. CH), 7.52 (d, J = 11.8 Hz, 4 H, arom.
arylation of 4-bromoanisole. The origin of the good per- CH), 7.30–6.97 (38 H, arom. CH), 6.51 (t, 3J = 7.6 Hz, 2 H, arom.
Eur. J. Org. Chem. 2012, 2786–2791
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L. Monnereau, D. Sémeril, D. Matt
FULL PAPER
3
CH), 6.21 (d, J = 7.6 Hz, 4 H, arom. CH), 5.29 (s, 4 H, CH2Ph), 25,26,27,28-Tetrabenzyloxy-5,17-bis(diphenylphosphinoyl)calix[4]-
arene (7): H2O2 (30% in water, 4 mL, 5.0 mmol) was added to a
8 H, ArCH2Ar), 3.83 [sept, J = 6.8 Hz, 4 H, CH(CH3)2], 1.12 [d, solution of 25,26,27,28-tetrabenzyloxy-5,17-bis(diphenylphos-
4.42 (s, 4 H, CH2Ph), 4.25 and 2.78 (AB spin system, 2J = 13.6 Hz,
3
3J = 6.8 Hz, 24 H, CH(CH3)2] ppm. 13C {1H} NMR (75 MHz,
CDCl3): δ = 157.65, 153.86 (2 s, arom. Cquat.–O), 142.56–118.62
(arom. C), 76.77 (s, OCH2Ph), 74.40 (s, OCH2Ph), 30.53 (s, Ar-
phanyl)calix[4]arene (1, 0.576 g, 0.5 mmol) in CH2Cl2 (10 mL). The
resulting solution was stirred at room temperature for 2 h. The mix-
ture was treated with a mixture of CH2Cl2 (10 mL) and water
CH2Ar), 27.49 [s, CH(CH3)2], 22.78 [s, CH(CH3)2] ppm. 31P {1H} (20 mL). After extraction of the aqueous layer with CH2Cl2
NMR (121 MHz, C D ): δ = –3.3 (s, PPh ) ppm. IR: ν = 1329 (2ϫ10 mL), the organic phases were combined. The resulting solu-
˜
6
6
2
(P=N) cm–1. MS (MALDI-TOF): m/z = 1503.69 [M + H]+ (ex-
pected isotopic profile). C104H100N2O4P2 (1503.86): calcd. C 83.06,
H 6.70, N 1.82; found C 82.82, H 6.54, N 1.80.
tion was washed with water (2ϫ10 mL), dried with Na2SO4 and
concentrated under reduced pressure to afford the bis(phos-
phane oxide) 7 as a white solid in quantitative yield. 1H NMR
(300 MHz, CDCl3): δ = 7.58–7.34 (20 H, arom. CH), 7.24–6.96 (24
H, arom. CH), 6.16 (t, J = 7.5 Hz, 2 H, arom. CH), 5.90 (d, J =
7.5 Hz, 4 H, arom. CH), 5.12 (s, 4 H, CH2Ph), 4.56 (s, 4 H,
CH2Ph), 4.12 and 2.82 (AB spin system, 2J = 13.8 Hz, 8 H, Ar-
CH2Ar) ppm. 13C{1H} NMR (75 MHz, CDCl3): δ = 158.97 (d,
4JP,C = 2.8 Hz, arom. Cquart.–O), 154.29 (s, arom. Cquart.–O),
137.64–122.21 (arom. C), 77.12 (s, OCH2Ph), 75.03 (s, OCH2Ph),
30.89 (s, ArCH2Ar) ppm. 31P {1H} NMR (121 MHz, CDCl3): δ =
31.0 (s, O=PPh2) ppm. C80H66O6P2 (1185.32): calcd. C 81.06, H
5.61; found C 80.89, H 5.72.
25,26,27,28-Tetrabenzyloxy-5,17-bis(4-butylphenyliminodiphenyl-
3
3
1
phosphoranyl)calix[4]arene (4): H NMR (300 MHz, C6D6): δ =
8.04–7.98 (8 H, arom. CH), 7.64 (d, 3J = 11.5 Hz, 4 H, arom. CH),
3
3
7.37 (d, J = 8.0 Hz, 4 H, arom. CH), 7.29 (d, J = 7.0 Hz, 4 H,
arom. CH), 7.19–6.96 (32 H, arom. CH), 6.45 (t, 3J = 7.6 Hz, 2 H,
arom. CH), 6.18 (d, 3J = 7.6 Hz, 4 H, arom. CH), 5.19 (s, 4 H,
2
CH2Ph), 4.45 (s, 4 H, CH2Ph), 4.20 and 2.70 (AB spin system, J
3
= 13.7 Hz, 8 H, ArCH2Ar), 2.60 (t, J = 6.5 Hz, 4 H, C6H4CH2),
1.62 (quint, 3J = 6.5 Hz, 4 H, C6H4CH2CH2), 1.33 (sext, 3J =
3
6.4 Hz, 4 H, CH2CH3), 0.86 (t, J = 6.4 Hz, 6 H, CH2CH3) ppm.
13C {1H} NMR (75 MHz, C6D6): δ = 159.74 (d, JP,C = 3.1 Hz,
Digold Complex 8: A solution of [AuCl(THT)] (0.045 g, 0.14 mmol)
4
arom. Cquart.–O), 155.08 (s, arom. Cquart.–O), 150.22–123.28 (arom. in THF (5 mL) was added to a stirred solution of 2 (0.100 g,
C), 77.63 (s, OCH2Ph), 75.80 (s, OCH2Ph), 35.60 (s, C6H4CH2), 0.07 mmol) in CH2Cl2 (15 mL). After 5 h, the solution was concen-
34.63 (s, C6H4CH2CH2), 31.66 (s, ArCH2Ar), 22.79 (s, CH2CH3),
trated to ca. 1 mL. Addition of hexane afforded 8 as a white solid
14.31 (s, CH2CH3) ppm. 31P {1H} NMR (121 MHz, C6D6): δ = (0.112 g, 86%). 1H NMR (300 MHz, C6D6): δ = 7.93–7.72 (8 H,
–0.4 (s, PPh ) ppm. IR: ν = 1325 (P=N) cm–1. MS (MALDI-TOF):
arom. CH), 7.54–7.42 (4 H, arom. CH), 7.32 (d, J = 6.3 Hz, 4 H,
arom. CH), 7.18–6.96 (30 H, arom. CH), 6.71 (s, 4 H, arom. CH),
6.22–6.09 (4 H, arom. CH), 5.25 and 5.21 (AB spin system, 2J =
13.1 Hz, 4 H, CH2Ph), 4.43 (s, 4 H, CH2Ph), 4.20 and 2.74 (AB
spin system, 2J = 13.8 Hz, 8 H, ArCH2Ar), 2.33 (s, 12 H, o-CH3
of mesityl), 2.17 (s, 6 H, p-CH3 of mesityl) ppm. 13C {1H} NMR
3
˜
2
m/z = 1447.59 [M + H]+ (expected isotopic profile). C100H92N2O4P2
(1447.76): calcd. C 82.96, H 6.40, N 1.93; found C 82.83, H 6.25,
N 1.92.
25,26,27,28-Tetrabenzyloxy-5,17-bis(2-methoxyphenyldiphenyl-
1
phosphoranyl)calix[4]arene (5): H NMR (300 MHz, C6D6): δ =
4
(75 MHz, C6D6): δ = 159.85 (d, JP,C = 3.7 Hz, arom. Cquat.–O),
8.04–7.98 (8 H, arom. CH), 7.63 (d, 3J = 11.8 Hz, 4 H, arom. CH),
155.36 (s, arom. Cquat.–O), 141.59–124.31 (arom. C), 78.07 (s,
OCH2Ph), 76.06 (s, OCH2Ph), 32.31 (s, ArCH2Ar), 23.40
(s, o-CH3 of mesityl), 21.54 (s, p-CH3 of mesityl) ppm. 31P {1H}
3
3
7.50 (d, J = 7.6 Hz, 2 H, arom. CH), 7.29 (d, J = 7.3 Hz, 4 H,
arom. CH), 7.20–6.80 (34 H, arom. CH), 6.38 (t, 3J = 7.5 Hz, 2 H,
arom. CH), 6.15 (d, 3J = 7.5 Hz, 4 H, arom. CH), 5.19 (s, 4 H,
NMR (121 MHz, C6D6):
δ
=
28.6 (s, PPh2) ppm.
2
CH2Ph), 4.46 (s, 4 H, CH2Ph), 4.21 and 2.72 (AB spin system, J
C98H88Au2Cl2N2O4P2·C6H14 (1884.54 + 86.17): calcd. C 63.38, H
5.22, N 1.42; found C 63.12, H 5.36, N 1.67.
= 13.6 Hz, 8 H, ArCH2Ar), 3.32 (s, 6 H, CH3OC6H4) ppm. 13C
{1H} NMR (75 MHz, C6D6): δ = 159.17 (d, JP,C = 3.7 Hz, arom.
4
Cquart.–O), 155.08 (s, arom. Cquart.–O), 153.58–112.20 (arom. C), Reaction of 6 with [PdCl2(CH3CN)2]: A solution of 6 (0.150 g,
77.63 (s, OCH2Ph), 75.74 (s, OCH2Ph), 54.84 (s, CH3OC6H4), 31.70
0.011 mmol) in CH2Cl2 (100 mL) was added slowly to a solution
of [PdCl2(CH3CN)2] (0.028 mg, 0.011 mmol) in CH2Cl2 (200 mL).
The resulting solution was stirred overnight and then concentrated
to ca. 5 mL. Addition of hexane (100 mL) afforded a brown pre-
cipitate, which turned out to contain several complexes that could
not be separated. MS (ESI-TOF, crude reaction mixture): m/z (%)
= 1573.41 (1) ([PdCl2(6) + H]+ requires 1573.40; expected isotopic
profile; see Scheme S2 in the Supporting Information).
(s, ArCH2Ar) ppm. 31P {1H} NMR (121 MHz, C6D6): δ = 0.5 (s,
PPh ) ppm. IR: ν = 1326 (P=N) cm–1. MS (MALDI-TOF): m/z =
˜
2
1395.50 [M + H]+ (expected isotopic profile). C94H80N2O6P2
(1395.60): calcd. C 80.90, H 5.78, N 2.01; found C 80.79, H 5.90,
N 1.81.
25,26,27,28-Tetrabenzyloxy-5,17-bis(4-methoxyphenyliminodi-
phenylphosphoranyl)calix[4]arene (6): 1H NMR (300 MHz, C6D6):
3
δ = 8.04–7.98 (8 H, arom. CH of PPh2), 7.63 (d, J = 11.7 Hz, 4 Silver Complex 9: A solution of AgBF4 (0.028 g, 0.14 mmol) in
3
3
H, arom. CH), 7.30 (d, J = 6.3 Hz, 4 H, arom. CH), 7.28 (d, J =
6.3 Hz, 4 H, arom. CH), 7.20–6.91 (32 H, arom. CH), 6.44 (t, 3J =
7.6 Hz, 2 H, arom. CH), 6.14 (d, 3J = 7.6 Hz, 4 H, arom. CH),
5.19 (s, 4 H, CH2Ph), 4.45 (s, 4 H, CH2Ph), 4.21 and 2.71 (AB spin
THF (10 mL) was added to a stirred solution of 6 (0.200 g,
0.14 mmol) in THF (40 mL). After 2 h, the solution was concen-
trated to ca. 1 mL. Addition of hexane afforded 9 as a white solid
(0.208 g, 92%). 1H NMR (300 MHz, CD2Cl2): δ = 7.73–7.15 (45
system, 2J = 13.5 Hz, 8 H, ArCH2Ar), 3.46 (s, 6 H, CH3OC6H4) H, arom. CH), 7.01–6.96 (6 H, arom. CH), 6.92 (d, J = 12.4 Hz,
3
4
3
ppm. 13C {1H} NMR (75 MHz, C6D6): δ = 159.33 (d, JP, C
=
2 H, arom. CH), 6.79 (d, J = 7.2 Hz, 2 H, arom. CH), 6.58–6.52
3.1 Hz, arom. Cquart.–O), 154.64 (s, arom. Cquart.–O), 152.45–114.63 (4 H, arom. CH), 6.54 (s, 4 H, CH2Ph), 4.88 (s, 4 H, CH2Ph), 4.22
2
(arom. C), 77.24 (s, OCH2Ph), 75.41 (s, OCH2Ph), 54.93 (s,
CH3OC6H4), 31.29 (s, ArCH2Ar) ppm. 31P {1H} NMR (121 MHz,
and 2.89 (AB spin system, 8 H, ArCH2Ar, J = 13.4 Hz), 3.70 (s,
6 H, CH3OC6H4) ppm. 13C {1H} NMR (75 MHz, CD2Cl2): δ =
159.68 (s, arom. Cquart.–O), 155.50 (s, arom. Cquart.–O), 152.50–
114.30 (arom. C), 78.49 (s, OCH2Ph), 76.12 (s, OCH2Ph), 55.87 (s,
CH3OC6H4), 31.89 (s, ArCH2Ar) ppm. 31P {1H} NMR (121 MHz,
CD2Cl2): δ = 24.8 [d, PPh2, 2J(P107,Ag) ≈ 2J(P109,Ag) = 7.7 Hz].
C D ): δ = –0.5 (s, PPh ) ppm. IR: ν = 1328 (P=N) cm–1. MS
˜
6
6
2
(MALDI-TOF): m/z = 1395.54 [M + H]+ (expected isotopic pro-
file). C94H80N2O6P2 (1395.60): calcd. C 80.90, H 5.78, N 2.01;
found C 80.96, H 5.95, N 1.88.
2790
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Eur. J. Org. Chem. 2012, 2786–2791

Calixarene-Based Bis(iminophosphoranes) in Suzuki–Miyaura Cross-Coupling
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Received: January 24, 2012
Published Online: March 28, 2012
Eur. J. Org. Chem. 2012, 2786–2791
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2791