A second-generation dendrimer with six 2,9-dimethyl-1,10-phenanthroline units as ligand for copper-catalyzed reactions

Article abstract of DOI:10.1002/ejoc.200600033

2,9-Dimethyl-1,10-phenanthroline (neocuproine, 1) has been attached to dendritic structures through its 5-position providing a trimer 7 and the hexamers 11 and 12. The copper-binding capability of the hexamer 12 has been studied, and the 6:1 complex has been used to catalyze the Cu ⁺-promoted substitution of an iodoarene 14 to give an aryl ether 15. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.

Full text of DOI:10.1002/ejoc.200600033

FULL PAPER
DOI: 10.1002/ejoc.200600033
A Second-Generation Dendrimer with Six 2,9-Dimethyl-1,10-phenanthroline
Units as Ligand for Copper-Catalyzed Reactions[‡]
Ulrich Lüning,*[a] Jan P. W. Eggert,[a] and Kathrin Hagemann[a]
Keywords: Catalysis / Dendrimer / Homogeneous catalysis / Sonogashira / Supramolecular Chemistry
2,9-Dimethyl-1,10-phenanthroline (neocuproine, 1) has been
attached to dendritic structures through its 5-position provid- substitution of an iodoarene 14 to give an aryl ether 15.
6:1 complex has been used to catalyze the Cu+-promoted
ing a trimer 7 and the hexamers 11 and 12. The copper-bind-
ing capability of the hexamer 12 has been studied, and the
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2006)
Introduction
An effective and cheap synthesis should not only produce
the desired compound in high yield, it must also provide
an easy workup which includes the removal of reagents or
catalysts from the product. Such a separation is facilitated
if the reagents or catalysts are bound to a polymer because
they can then be removed by filtration.[1,2] However, the
polymeric backbone sometimes influences the outcome of
a reaction, especially if the diffusion of substrates into the
polymeric compound is uneven at different regions of a
polymer. Dendrimers are a special class of polymers which
combine two properties from polymer and non-polymer
chemistry: they possess a high molecular weight but they
are monodispers, well-defined molecules.[3,4] Therefore, the
reactivity and selectivity of a catalyst bound to the surface
of a dendrimer should be very similar to that of the non-
polymeric analog.
Many catalytic systems consist of transition metal ions
complexed to suitable ligands. Chelating ligands play an im-
portant role because their binding is stronger than that of
the substrate to be altered. An important chelating ligand
is 1,10-phenanthroline, and especially its 2,9-dimethyl deriv-
ative neocuproine (1).[5–7] In order to prevent interference
with the metal ion bound to the nitrogen atoms of 1,10-
phenanthroline, in a polymeric or dendritic scaffold, neocu-
proine should be connected by its backside, i.e. through po-
sitions 4, 5, 6 or 7. Recently, we developed an efficient route
to 5-bromo-substituted neocuproines 2 and 3,[8] which have
proven to be good building blocks for 5-substituted deriva-
tives.
Results and Discussion
Crucial for the synthesis of 2 and 3 is the introduction of
tert-butyldimethylsilyl (TBDMS) substituents at the methyl
groups of the 2,9-dimethyl-1,10-phenanthroline system.
This substitution protects the methyl groups from side reac-
tions and drastically improves the solubility. After bromina-
tion, the bromine atom in 5-position can easily be replaced
by a variety of substituents using palladium-catalyzed
cross-coupling reactions. For example, the trimethylsilyl-
protected ethynyl-neocuproine 4 has been synthesized from
bromide 3 in 44% yield.[8] Treatment with tetrabutylammo-
nium fluoride (TBAF) at –78 °C selectively desilylates the
trimethylsilylethynyl group in compound 4 and produces
the free alkyne 5 in 71% yield.
With the terminal alkyne functionality, again Sonoga-
shira couplings are possible. Under standard Sonogashira
conditions with additional use of ultrasound, three alkynes
5 can be coupled to triiodobenzene (6)[9] to give a symmetri-
cal trimer 7 in 58% yield.
But the alkyne 5 can also be coupled to a branching unit
8[10] possessing two iodide functionalities and one ad-
ditional, trimethylsilyl-protected alkyne. By using more
than 2 equiv. (2.5:1) of the alkyne 5 in the reaction with the
diiodide 8, a first-generation dendron 9 can be obtained in
56% yield under Sonogashira conditions with ultrasound.
Again, the trimethylsilyl group can be removed with TBAF
thereby setting free the alkyne 10 (81%).
[‡] Concave Reagents, 48. Part 47: U. Lüning, F. Fahrenkrug, Eur.
J. Org. Chem. 2006, 916–923.
[a] Otto-Diels-Institut für Organische Chemie, Christian-Al-
brechts-Universität zu Kiel,
Olshausenstr. 40, 24098 Kiel, Germany
Fax: + 49-431-880-1558
E-mail: luening@oc.uni-kiel.de
With 3.3 equiv. of the dendron 10, three branched units
can then be connected to triiodobenzene (6)[9] to give 58%
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U. Lüning, J. P. W. Eggert, K. Hagemann
FULL PAPER
of a second-generation dendrimer 11, decorated with six chosen as metal ion, and the stoichiometry of the complex
1,10-phenanthroline units on the outside. In addition, the formation with 12 has been investigated by Job plots.[11,12]
silyl groups in this dendrimer can be removed by reaction The experiments have also been carried out with 2,9-di-
with tetrabutylammonium fluoride, thus generating the methyl-5-(phenylethynyl)-1,10-phenanthroline (13) for com-
hexakis(neocuproine) dendrimer 12 (86%).
parison (see Figure 1).
In contrast to monomer 13, the Job plot for dendrimer
12 shows two separated maxima which correspond to Cu+
ions bound to one or two 1,10-phenanthroline moieties.
This double maximum indicates that depending on the mo-
Complexation Behaviour of the Dendrimer 12 and Its Use
as Ligand in a Cu+-Catalyzed Reaction
1,10-Phenanthrolines are good ligands for transition lar ratio chosen, 2:1 or 1:1 complexes will predominantly
metal ions, and many of the resulting complexes are cata- exist for each Cu+ ion. A 1:6 ratio of 12/CuPF6 corresponds
lysts for a variety of reactions.[5–7] Therefore, the complex to a situation in which each Cu+ ion is bound to one neocu-
formation of the hexamer 12 has been studied. Cu+ was proine unit.
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Dendrimer with Six 2,9-Dimethyl-1,10-phenanthroline Units
FULL PAPER
lyzed by copper salts under drastic conditions (high tem-
perature, strong bases). Buchwald has developed a milder
reaction using copper() triflate in the presence of cesium
carbonate.[13] To avoid the use of the air-sensitive and ex-
pensive triflate, copper() iodide can be used if a suitable
ligand is present, for instance unsubstituted 1,10-phenan-
throline.[14] To allow a comparison with the dendrimer 12,
we have first checked this catalysis in the presence of 2,9-
dimethyl-1,10-phenanthroline (1), and then applied the
same conditions to dendrimer 12. To promote the forma-
tion of the catalytically active 1:1 complexes, copper() io-
dide and the ligand were used in equal amounts. The reac-
tions were carried out using 20 mol-% of the catalysts, cal-
culated per 1,10-phenanthroline unit. Table 1 lists the re-
sults obtained with the monomeric neocuproine 1 and the
dendritic hexamer 12. Furthermore, reactions have been
carried out which lacked the ligand or Cu+ ions (see
Table 1).
Figure 1. Normalized Job plots for mixtures of the hexamer 12 and
CuPF6 (left), and of the monomer 13 and CuPF6 (right).
Table 1. Cu+-catalyzed substitution of 4-iodoanisol (14) to give 1,4-
dimethoxybenzene (15) using different ligands.
This should enable the resulting complex to coordinate
additional molecules such as substrates. As a model reac-
tion for catalytic activity of Cu+ complexes of 12, we
checked the formation of dimethoxybenzene (15) from 4-
iodoanisole (14). The nucleophilic substitution of halogen
atoms by alkoxy groups (Ullmann reaction) can be cata-
Ligand
Product 15/anisol 14
1
85:15
86:14
35:65
11:89
12
No ligand
No copper salt
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U. Lüning, J. P. W. Eggert, K. Hagemann
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1 H, Phen-H6), 7.35 (d, J = 8.4 Hz, 1 H, Phen-H3), 7.28 (d, J =
8.3 Hz, 1 H, Phen-H8), 3.45 (s, 1 H, CϵCH), 2.78 (s, 2 H, PhenC2-
CH2), 2.77 (s, 2 H, PhenC9-CH2), 0.94 [s, 9 H, PhenC2CH2Si-
C(CH3)3], 0.94 [s, 9 H, PhenC9CH2SiC(CH3)3], –0.01 [s, 12 H,
PhenC2,9CH2Si(CH3)2] ppm. 13C NMR (75 MHz, CDCl3): δ =
163.49 (Phen-C9), 162.72 (Phen-C2), 145.78 (Phen-C10a), 145.17
(Phen-C10b), 135.29 (Phen-C7), 133.86 (Phen-C4), 130.20 (Phen-
C6), 125.54 (Phen-C4a), 124.94 (Phen-C6a), 123.20 (Phen-C3,8),
116.53 (Phen-C5), 81.69 (Phen-CϵCH), 81.05 (Phen-CϵCH),
27.86 (PhenC9-CH2), 27.54 (PhenC2-CH2), 26.53 [PhenC2,9CH2-
SiC(CH3)3], 17.06 [PhenC2,9CH2SiC(CH3)3], –6.06 [PhenC2,9CH2-
Si(CH3)2] ppm. C28H40N2Si2 (460.27): calcd. C 72.98, H 8.75, N
6.08; C28H40N2Si2·0.2H2O (463.87): calcd. C 72.41, H 8.77, N 6.03;
With 1, the reported yield was almost confirmed
(88%[14]). The hexamer 12 gives nearly identical results.
This proves that each Cu+ center in the dendrimer complex
operates separately and that the dendritic core has no influ-
ence on the reactivity of the metal ion complex.
Conclusion
Therefore, dendritic neocuproines can be used as a sub-
stitute for the monomer with the potential of easy recovery.
Dendrimers of higher generation should easily be separat-
able from the reaction mixture by ultrafiltration as shown found C 72.51, H 8.64, N 6.25. The product is sensible to acid and
for many other dendritic structures.[3,15]
heat. It was stored under argon at –18 °C.
1,3,5-Tris[2,9-(tert-butyldimethylsilylmethyl)-1,10-phenanthrolinyl-
5-ethynyl]benzene (7): 1,3,5-Triiodobenzene[9] (6, 5.71 mg,
30.0 µmol) and 2,9-bis(tert-butyldimethylsilylmethyl)-5-ethynyl-
1,10-phenanthroline (5, 184 mg, 400 µmol) were dissolved in a mix-
ture of dry benzene (5 mL) and dry triethylamine (1 mL). After
Experimental Section
General Remarks: The following chemicals were obtained commer-
cially and were used without further purification: bis(triphenylpho-
sphane)palladium() dichloride (Fluka), 4-iodoanisol (Fluka), neo-
cuproine (Chempur), tetrabutylammonium fluoride trihydrate
(Fluka), tetrakis(acetonitrile)copper() hexafluorophosphate (Ald-
rich). 1,3,5-Triiodobenzene[9] and 1,3-diiodo-5-(trimethylsilylethyn-
yl)benzene,[9] were prepared according to literature procedures.
HPLC grade THF was used. Other dry solvents were obtained with
suitable desiccants. Column chromatography was carried out on
neutral alumina (Fluka) or silica gel (Macherey–Nagel). The chro-
degassing in an ultrasound bath under a flow of argon for 30 min,
copper() iodide (5.71 mg, 30.0 µmol) and bis(triphenylphosphane)
palladium() dichloride (10.5 mg, 15.0 µmol) were added and the
mixture was sonicated in an ultrasound bath at 50 °C (the heating
was caused by the energy of the sonification) for 18 h. After evapo-
ration of the solvent in vacuo, the residue was dissolved in dichloro-
methane (5 mL) and the organic layer was washed with 0.1  potas-
sium cyanide solution (5 mL) and deionized water (5 mL). After
drying with sodium sulfate, the solvent was evaporated in vacuo
and the residue was purified by chromatography [chromatotron,
neutral alumina, cyclohexane/ethyl acetate (10:1); Rf = 0.1] yielding
1
matotron was model 7924T from Harrison Research. H and 13C
NMR spectra were recorded with Bruker ARX 300 (300 MHz or
75 MHz) or DRX 500 (500 MHz or 125 MHz) instruments, using
tetramethylsilane as internal standard. IR spectra were measured
with a Perkin–Elmer 1600 instrument. Mass spectra were recorded
with Finnigan MAT 8200 or 8230 instruments, a MALDI-TOF
mass spectrometer Biflex III (Bruker-Daltonics; using 4-hydroxy-
α-cinnamic acid as matrix), or an ESI mass spectrometer Esquire-
LC (Bruker-Daltonics; using methanol/dichloromethane, 1:1, as
solvent). UV/Vis spectra were recorded with a Lambda 14 instru-
ment (Perkin–Elmer) at 25.0 0.1 °C. Elemental analyses were car-
ried out with a VarioEl instrument (Elementaranalysensysteme
GmbH). Gas chromatography was performed with a 6890 N instru-
ment (Agilent); injector: split/splitless, split ratio: 11:1, injector
temp.: 250 °C, detector: FID, detector temp.: 300 °C.
84.0 mg (58%) of 7 as a yellow solid, m.p. 222 °C. IR (KBr): ν =
˜
2924 (aliph. C–H), 1602 (arom. C=C), 1483 (aliph. C–H), 843
(arom. C–H) cm–1. MS (MALDI-TOF): m/z (%) = 1478 (26)
[M+Na]+, 1456 (100) [M +H]+, 1341 (23) [M + H – TBDMS]+.
HRMS: C90H121N6Si6: found 1453.8377, calcd. 1453.8286
(–7.4 ppm); C8913CH121N6Si6: found 1454.8303, calcd. 1454.8301
1
(–0.1 ppm). H NMR (300 MHz, CDCl3): δ = 8.64 (d, J = 8.3 Hz,
3 H, Phen-H4), 8.02 (d, J = 8.4 Hz, 3 H, Phen-H7), 7.99 (s, 3 H,
Phen-H6), 7.95 (s, 3 H, Ar-H2,4,6), 7.43 (d, J = 8.4 Hz, 3 H, Phen-
H3), 7.32 (d, J = 8.3 Hz, 3 H, Phen-H8), 2.82 (s, 6 H, PhenC2-CH2),
2.81 (s, 6 H, PhenC9-CH2), 0.97 [s, 54 H, PhenC2,9CH2SiC(CH3)3],
0.03 [s, 18 H, PhenC2CH2Si(CH3)2], 0.02 [s, 18 H, PhenC9CH2-
Si(CH3)2]. 13C NMR (75 MHz, CDCl3): δ = 163.57 (Phen-C9),
162.85 (Phen-C2), 145.82 (Phen-C10a), 145.33 (Phen-C10b), 135.35
(Phen-C7), 134.32 (Ar-C2,4,6), 133.92 (Phen-C4), 129.70 (Phen-C6),
125.44 (Phen-C4a), 125.19 (Phen-C6a), 124.29 (Ar-C1,3,5), 123.43
(Phen-C8), 123.29 (Phen-C3), 117.11 (Phen-C5), 92.25 (Phen-CϵC),
88.42 (Phen-CϵC), 27.96 (PhenC9-CH2), 27.67 (PhenC2-CH2),
26.58 [PhenC9CH2SiC(CH3)3], 26.56 [PhenC2CH2SiC(CH3)3],
17.09 [PhenC9CH2SiC(CH3)3], 17.08 [PhenC2CH2SiC(CH3)3],
–6.01 [PhenC2,9CH2Si(CH3)2] ppm.
2,9-Bis[(tert-butyldimethylsilyl)methyl]-5-ethynyl-1,10-phenan-
throline (5): 2,9-Bis[(tert-butyldimethylsilyl)methyl]-5-[(trimethyl-
silyl)ethynyl]-1,10-phenanthroline (4, 107 mg, 200 µmol) was dis-
solved in dry THF (8 mL) and cooled to –78 °C. Then, tetra-n-
butylammoniumfluoride trihydrate (TBAF·3H2O, 63.1 mg,
200 µmol) dissolved in dry THF (1 mL) was added dropwise. After
stirring for 1 h at –78 °C, deionized water (9 mL) was added, and
after warming to room temp., the mixture was extracted with
dichloromethane (2 × 10 mL), the organic layers were combined,
washed with brine (10 mL), dried with sodium sulfate, and the sol-
vents were evaporated in vacuo. Chromatography [chromatotron,
neutral alumina, cyclohexane/ethyl acetate (20:1); DC (10:1), Rf =
0.43] yielded 65.0 mg (71%) of 5 as a colorless solid, m.p. 141 °C.
3,5-Bis[2,9-bis(tert-butyldimethylsilylmethyl)-1,10-phenanthrolin-5-
ylethynyl]-1-(trimethylsilylethynyl)benzene (9): Under argon, 2,9-bis-
(tert-butyldimethylsilylmethyl)-5-ethynyl-1,10-phenanthroline (5,
340 mg, 738 µmol) was added to a solution of 1,3-diiodo-5-(trime-
thylsilylethynyl)benzene[10] (8, 126 mg, 295 µmol) in a mixture of
dry benzene (10 mL) and dry triethylamine (2 mL). The mixture
IR (KBr): ν = 3138 (CϵC–H), 2951 (aliph. C–H), 2074 (CϵC), was degassed by sonication in an ultrasound bath using an argon
˜
1604 (arom. C=C), 1482 (aliph. C–H), 845 (arom. C–H) cm–1. MS
( EI = 7 0 eV ): m/ z ( % ) = 4 6 1 ( 1 0 0 ) [ M + H ] + , 403 (42)
[M+H – tBu]+. 1H NMR (300 MHz, CDCl3): δ = 8.51 (d, J =
8.4 Hz, 1 H, Phen-H4), 7.96 (d, J = 8.3 Hz, 1 H, Phen-H7), 7.90 (s,
flow for 20 min. Copper() iodide (11.4 mg, 60.0 µmol) and bis(tri-
phenylphosphane)palladium() dichloride (21.1 mg, 30.0 µmol)
were added, and the mixture was sonicated in an ultrasound bath
at 50 °C (the heating was caused by the energy of the sonification)
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Dendrimer with Six 2,9-Dimethyl-1,10-phenanthroline Units
FULL PAPER
for 18 h. After evaporation of the solvent in vacuo, the residue was
dissolved in dichloromethane (10 mL) and the organic layer was
washed with 0.1  potassium cyanide solution (10 mL) and deion-
ized water (10 mL). After drying with sodium sulfate, flash
chromatography (neutral alumina, cyclohexane/ethyl acetate (10:1);
DC (5:1), Rf = 0.44) gave 181 mg (56%) of 9 as colorless solid, m.p.
0.4C6H12 (1059.40): calcd. C 75.19, H 8.33, N 5.28; found C 75.17,
H 8.44, N 5.38. The product is sensitive to acid and heat. It was
stored under argon at –18 °C. The sample used for elemental analy-
sis was purified by chromatography (neutral alumina, cyclohexane/
ethyl acetate (10:1); DC (5:1), Rf = 0.32).
1,3,5-Tris{3,5-bis[2,9-bis(tert-butyldimethylsilylmethyl)-1,10-phen-
anthrolin-5-yl-ethynyl]phenylethynyl}benzene (11): 1,3,5-Triiodoben-
zene[9] (6, 5.95 mg, 12.6 µmol) and 3,5-bis[2,9-bis(tert-butyldi-
methylsilylmethyl)-1,10-phenanthrolin-5-yl-ethynyl]ethynylbenzene
(10, 44.0 mg, 41.9 µmol) were dissolved in dry toluene (2 mL) and
dry triethylamine (3 mL). After degassing in an ultrasound bath
under a flow of argon for 30 min, copper() iodide (95.0 µg,
5.00 µmol) and bis(triphenylphosphane)palladium() dichloride
(1.76 mg, 2.50 µmol) were added and the mixture was sonicated in
an ultrasound bath at 50 °C (the heating was caused by the energy
of the sonification) for 18 h. After evaporation of the solvent in
vacuo, the residue was dissolved in dichloromethane (5 mL) and
the organic layer was washed with 0.1  potassium cyanide solution
(5 mL) and deionized water (5 mL). After drying with sodium sul-
fate, the solvent was evaporated in vacuo and the residue was puri-
fied by chromatography [neutral alumina, cyclohexane/ethyl acetate
(5:1); Rf = 0.17] yielding 23.0 mg (58%) of 11, m.p. 283 °C. 1H
NMR (300 MHz, CDCl3): δ = 8.62 (d, J = 8.4 Hz, 6 H, Phen-H4),
8.10 (d, J = 8.2 Hz, 6 H, Phen-H7), 8.07 (s, 6 H, Phen-H6), 7.92 (s,
3 H, Ar1-H2,4,6), 7.89 (t, J = 1.5 Hz, 3 H, Ar2-H4) 7.81 (d, J =
1.5 Hz, 6 H, Ar2-H2,6), 7.42 (d, J = 8.4 Hz, 6 H, Phen-H3), 7.33 (d,
J = 8.1 Hz, 6 H, Phen-H8), 2.94 (s, 12 H, PhenC2-CH2), 2.88 (s, 12
H, PhenC9-CH2), 0.98 [s, 54 H, PhenC2CH2SiC(CH3)3], 0.96 [s, 54
H, PhenC9CH2SiC(CH3)3], 0.02 [s, 36 H, PhenC2,9CH2Si(CH3)2]
ppm.
254–259 °C. IR (KBr): ν = 2950 (aliph. C–H), 1603 (arom. C=C),
˜
1483 (aliph. C–H), 882, 843 (arom. C–H) cm–1. MS (ESI): m/z (%)
= 1092 (100) [M + H]+, 1020 (14) [M + H – TMS]+. 1H NMR
(500 MHz, CDCl3): δ = 8.58 (d, J = 8.4 Hz, 2 H, Phen-H4), 7.99
(d, J = 8.3 Hz, 2 H, Phen-H7), 7.94 (s, 2 H, Phen-H6), 7.86 (t, J =
1.6 Hz, 1 H, Ar-H4), 7.76 (d, J = 1.6 Hz, 2 H, Ar-H2,6), 7.40 (d, J
= 8.4 Hz, 2 H, Phen-H3), 7.30 (d, J = 8.3 Hz, 2 H, Phen-H8), 2.81
(s, 4 H, PhenC2-CH2), 2.79 (s, 4 H, PhenC9-CH2), 0.96 [s, 18 H,
PhenC2CH2SiC(CH3)3], 0.96 [s, 18 H, PhenC9CH2SiC(CH3)3], 0.30
[s, 9 H, CϵCSi(CH3)3], 0.01 [s, 12 H, PhenC2CH2Si(CH3)2], 0.01
[s, 12 H, PhenC9CH2Si(CH3)2]. 13C NMR (125 MHz, CDCl3): δ
= 163.50 (Phen-C9), 162.80 (Phen-C2), 145.80 (Phen-C10a), 145.31
(Phen-C10b), 135.34 (Phen-C7), 134.68 (Ar-C2,6), 134.27 (Ar-C4),
133.92 (Phen-C4), 129.60 (Phen-C6), 125.43 (Phen-C4a), 125.18
(Phen-C6a), 124.24 (Ar-C1), 124.00 (Ar-C3,5), 123.26 (Phen-C3),
123.23 (Phen-C8), 117.15 (Phen-C5), 103.15 (Ar-CϵCTMS), 96.24
(Ar-CϵCTMS), 92.25 (Phen-CϵC), 88.17 (Phen-CϵC), 27.93
(PhenC9-CH2), 27.64 (PhenC2-CH2), 26.56 [PhenC9CH2SiC-
(CH3)3], 26.55 [PhenC2CH2SiC(CH3)3], 17.09 [PhenC9CH2-
SiC(CH3)3], 17.08 [PhenC2CH2SiC(CH3)3], –0.10 [Si(CH3)3], –6.01
[PhenC2,9CH2Si(CH3)2] ppm. C67H90N4Si5 (1090.60): calcd. C
73.70, H 8.31, N 5.13; C67H90N4Si5·0.7H2O·0.5C6H12 (1145.26):
calcd. C 73.32, H 8.56, N 4.89; found C 73.32, H 8.59, N 4.96. The
product is sensitive to acid and heat. It was stored under argon at
–18 °C.
1,3,5-Tris{3,5-bis[2,9-dimethyl-1,10-phenanthrolin-5-yl-ethynyl]-
phenylethynyl}benzene (12): A solution of tetrabutylammonium
fluoride (25.4 mg, 80.5 µmol) in dry THF (1 mL) was added drop-
wise to a solution of 1,3,5-tris{3,5-bis[2,9-bis(tert-butyldimethylsil-
ylmethyl)-1,10-phenanthrolin-5-yl-ethynyl]phenylethynyl}-
benzene (11, 21.0 mg, 6.71 µmol) in dry THF (3 mL). After stirring
for 1 h, deionized water (3 mL) and dichloromethane (3 mL) were
added, and the layers were separated. The aqueous layer was ex-
tracted with dichloromethane (3 × 3 mL), the organic layers were
combined, washed with brine (3 mL) and dried with sodium sulfate.
Evaporation of the solvent in vacuo yielded 10.1 mg (86%) of 12
3,5-Bis[2,9-bis(tert-butyldimethylsilylmethyl)-1,10-phenanthrolin-5-
ylethynyl]-1-ethynylbenzene (10): A solution of tetrabutylammoni-
umfluoride trihydrate (TBAF·3H2O, 80.0 mg, 254 µmol) in dry
THF (4 mL) was added dropwise to a solution of 3,5-bis[2,9-(tert-
butyldimethylsilylmethyl)-1,10-phenanthrolin-5-ylethynyl]-1-(tri-
methylsilylethynyl)benzene (9, 277 mg, 254 µmol) in dry THF
(20 mL). After stirring for 1 h, deionized water (25 mL) and dichlo-
romethane (25 mL) were added, and the layers were separated. The
aqueous layer was extracted with dichloromethane (3 × 25 mL),
the organic layers were combined, washed with brine (25 mL) and
dried with sodium sulfate. Evaporation of the solvent in vacuo
as
a
colorless solid. MS (MALDI-TOF): 891 [M+
yielded 210 mg (81%) of 10 as a yellowish solid. IR (KBr): ν =
˜
1
Na]2+. H NMR (300 MHz, CDCl3): δ = 8.71 (d, J = 8.3 Hz, 6 H,
Phen-H4), 8.14 (d, J = 8.2 Hz, 6 H, Phen-H7), 8.07 (s, 6 H, Phen-
H6), 7.92 (s, 3 H, Ar1-H2,4,6), 7.89 (t, J = 1.5 Hz, 3 H, Ar2-H4) 7.81
(d, J = 1.5 Hz, 6 H, Ar2-H2,6), 7.63 (d, J = 8.3 Hz, 6 H, Phen-H3),
7.54 (d, J = 8.0 Hz, 6 H, Phen-H8), 2.99 (s, 18 H, PhenC2-CH3),
2.97 (s, 18 H, PhenC9-CH3). 13C NMR (75 MHz, CDCl3): δ =
160.68 (Phen-C9), 160.09 (Phen-C2), 145.38 (Phen-C10a), 145.07
(Phen-C10b), 139.46 (Ar1-C2,4,6), 139.46 (Ar2-C4), 136.22 (Phen-C7),
134.80 (Ar2-C2,6), 134.56 (Phen-C4), 130.42 (Phen-C6), 126.37
(Phen-C4a), 126.14 (Phen-C6a), 124.09 (Ar1-C1,3,5), 124.09 (Ar2-
C1,3,5), 123.98 (Phen-C3), 123.98 (Phen-C8), 118.07 (Phen-C5),
94.22 (Phen-CϵC), 92.62 (Phen-CϵC), 78.54 (Ar1-CϵC–Ar2),
78.41 (Ar1-CϵCAr2), 29.71 (PhenC2,9-CH3).
2925 (aliph. C–H), 2154 (CϵC), 1602 (arom. C=C), 1483 (aliph.
C–H), 842 (arom. C–H) cm–1. MS (ESI): m/z (%) = 1020 (100)
[M+H]+, 510 (53) [MH2]2+. 1H NMR (500 MHz, CDCl3): δ = 8.58
(d, J = 8.4 Hz, 2 H, Phen-H4), 8.00 (d, J = 8.3 Hz, 2 H, Phen-H7),
7.95 (s, 2 H, Phen-H6), 7.89 (t, J = 1.6 Hz, 1 H, Ar-H4), 7.77 (d, J
= 1.6 Hz, 2 H, Ar-H2,6), 7.40 (d, J = 8.4 Hz, 2 H, Phen-H3), 7.30
(d, J = 8.3 Hz, 2 H, Phen-H8), 3.20 (s, 1 H, CϵCH), 2.81 (s, 4 H,
PhenC2-CH2), 2.79 (s, 4 H, PhenC9-CH2), 0.96 [s, 18 H,
PhenC2CH2SiC(CH3)3], 0.96 [s, 18 H, PhenC9CH2SiC(CH3)3], 0.01
[s, 24 H, PhenC2,9CH2Si(CH3)2]. 13C NMR (125 MHz, CDCl3):
163.55 (Phen-C9), 162.83 (Phen-C2), 145.82 (Phen-C10a), 145.32
(Phen-C10b), 135.34 (Phen-C7), 134.82 (Ar-C2,6), 134.65 (Ar-C4),
133.88 (Phen-C4), 129.67 (Phen-C6), 125.42 (Phen-C4a), 125.17
(Phen-C6a), 124.15 (Ar-C1), 123.28 (Ar-C3,5), 123.23 (Phen-C3,8), UV/Vis Studies of the Complex Formation of 12 with Cu+: 100 µ
117.05 (Phen-C5), 92.07 (Phen-CϵCH), 88.37 (Phen-CϵCH),
81.94 (Ar-CϵCH), 78.76 (Ar-CϵCH), 27.94 (PhenC9-CH2), 27.65
(PhenC2-CH2), 26.57 [PhenC9CH2SiC(CH3)3], 26.55 [PhenC2CH2-
solutions of neocuproine 1 and tetrakis(acetonitrile)copper() hexa-
fluorophosphate [(CH3CN)4Cu]PF6 and a 16.7 µ solution of 12
in 1:1 mixtures of chloroform/acetonitrile were prepared. At 25 °C,
SiC(CH3)3], 17.09 [PhenC9CH2SiC(CH3)3], 17.08 [PhenC2CH2- aliquots of the ligand and the Cu+ solutions were mixed in various
SiC(CH3)3], –6.01 [PhenC2,9CH2Si(CH3)2] ppm. C64H82N4Si4
(1018.56): calcd. C 75.38, H 8.10, N 5.49; C64H82N4Si4·0.4H2O·
ratios (10 – n):n in the range n = 0–10, i.e. the total volume always
was identical (Job plot[11,12]). The spectra between 225 and 500 nm
Eur. J. Org. Chem. 2006, 2747–2752
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
2751

U. Lüning, J. P. W. Eggert, K. Hagemann
FULL PAPER
[3] G. R. Newkome, C. N. Moorefield, F. Vögtle, Dendrimers and
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[4] Top. Curr. Chem., “Dendrimers I–V”, Springer, Heidelberg,
1998, vol. 197, 2000, vol. 210, 2001, vol. 212, 2001, vol. 217,
2003, vol. 228.
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[6] W. Sliwa, Heterocycles 1979, 12, 1207–1237.
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Thieme, Stuttgart, New York, 1993.
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[9] U. Schöberl, T. F. Magnera, R. M. Harrison, F. Fleischer, J. L.
Pflug, P. F. H. Schwab, X. Meng, D. Lipiak, B. C. Noll, V. S.
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were recorded and the data were analyzed as Job plots at different
wavelengths. Representatively, one plot is shown in Figure 1.
Cu+-Catalyzed Formation of 4-Methoxyanisol from 4-Iodoanisol: 4-
Iodoanisol (14, 23.4 mg, 100 µmol), copper() iodide (4.00 mg,
20.0 µmol), cesium carbonate (45.6 mg, 140 µmol), and the ligand
[(i) 1,3,5-tris{3,5-bis[2,9-dimethyl-1,10-phenanthrolin-5-yl-ethynyl]-
phenylethynyl}benzene (12, 5.87 mg, 3.33 µmol), or (ii) neocupro-
ine (1, 4.17 mg, 20.0 µmol), or (iii) no ligand] were mixed with
methanol (0.3 mL) in a vial (ca. 10 cm long) sealed with a teflon
cap. The resulting mixture was heated to 110 °C for 24 h. After
evaporation of the solvent, the residue was dissolved in diethyl
ether (5 mL) and filtered through silica gel. After evaporation of
the solvent, solutions with a concentration of 2 mg/mL were pre-
pared, and 0.5 mL of these solutions were mixed with 0.5 mL of a
solution of n-dodecane (c = 1 mg/mL), and the mixture was ana-
lyzed by GC [column: HP5, 30 m, flow (N2): 20 mL/min, start at
100 °C, hold for 5 min, then 3 °C/min until 250 °C are reached. rt:
4-iodoanisol: 4.88 min; 1,4-dimethoxybenzene: 2.43; n-dodecane as
internal standard: 2.85 min].
[1]
“Immobilized Catalysts: Solid Phases, Immobilization and Ap-
plications”, in Top. Curr. Chem. (Ed.: A. Kirschning), Springer
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[2] Dendrimers as support for recoverable catalysts and reagents:
R. van Heerbeek, P. C. J. Kamer, P. W. N. M. van Leeuwen,
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Received: January 17, 2006
Published Online: April 10, 2006
2752
www.eurjoc.org
© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2006, 2747–2752