Metallodendritic grafted core-shell γ-Fe2O3 nanoparticles used as recoverable catalysts in Suzuki C-C coupling reactions

Article abstract of DOI:10.1002/chem.201103147

The use of dendritic structures for the grafting of core-shell γ-Fe₂O₃/polymer 300 nm superparamagnetic nanoparticles (MNPs) has been performed with four metallodendrons that were functionalized with diphosphinopalladium complexes. The catalytic performance of these nanocatalysts was optimized for the Suzuki C-C cross-coupling reaction. These results demonstrated the importance of optimizing the catalytic efficiency of grafted MNPs by optimizing the dendritic structures and the nature of the peripheral phosphine ligands. All of these nanocatalysts showed remarkable reactivity towards bromoarenes and they were recovered and efficiently reused by magnetic separation with almost no loss of reactivity, even after 25 cycles. Copyright

Full text of DOI:10.1002/chem.201103147

FULL PAPER
DOI: 10.1002/chem.201103147
Metallodendritic Grafted Core–Shell g-Fe2O3 Nanoparticles Used as
ꢀ
Recoverable Catalysts in Suzuki C C Coupling Reactions
D. Rosario-Amorin,*[a, b] M. Gaboyard,[d] R. Clꢀrac,[e, f] L. Vellutini,[a, b] S. Nlate,*[c] and
K. Heuzꢀ*[a, b]
Abstract: The use of dendritic struc-
tures for the grafting of core–shell g-
Fe2O3/polymer 300 nm superparamag-
netic nanoparticles (MNPs) has been
performed with four metallodendrons
that were functionalized with diphos-
phinopalladium complexes. The cata-
lytic performance of these nanocata-
cross-coupling reaction. These results
demonstrated the importance of opti-
mizing the catalytic efficiency of graft-
ed MNPs by optimizing the dendritic
structures and the nature of the periph-
eral phosphine ligands. All of these
nanocatalysts showed remarkable reac-
tivity towards bromoarenes and they
were recovered and efficiently reused
by magnetic separation with almost no
loss of reactivity, even after 25 cycles.
Keywords: catalyst recovery · core–
shell magnetic nanoparticles · cross-
coupling · dendrimers · magnetic
properties · nanoparticles
ꢀ
lysts was optimized for the Suzuki C C
Introduction
al partners.[1] In this area, “smart” supports, such as super-
paramagnetic nanoparticles[2] (MNPs), have come to the
fore, opening up great potential for catalyst recovery be-
cause the recovery step requires only a simple and cheap ex-
ternal magnet unlike conventional techniques (such as filtra-
tion), which are difficult to carry out owing to the nanome-
ter size of the catalyst particles. In general, these nanoparti-
cles (usually nanometer to submicrometer in size) have en-
hanced surface areas relative to bulk materials and provide
better access to substrate molecules and higher reactivities
than conventional supports.[3] Furthermore, their magnetic
behavior ensures that their flocculation or dispersion is re-
versibly controlled by a static magnetic field. As a result, in
the absence of an external magnetic field, superparamagnet-
ic nanoparticles can be well-dispersed in the reaction
medium for their reuse. Indeed, the recent development of
MNP-supported catalysts has emerged because of significant
advances in the synthesis of size-controlled and monodis-
perse MNPs[4] as well as in their surface stabilization by
simple organic compounds, such as silanes,[5] carboxylic
acids,[6] and phosphonic acids.[7] This surface modification is
often performed through a process that involves the ex-
change of stabilizing ligands or the coating of the magnetic
core with an organic/inorganic polymer shell.[8,9] In those
cases, the polymer or the silica shell allows the formation of
core–shell nanostructures, which are used as supports for
the immobilization of homogeneous catalysts. These shells
ensure the confinement of the magnetic core and prevent
the aggregation of the nanoparticles in suspension. More-
over, they provide chemical stability and a wide range of an-
choring sites for catalytic species. Many applications of
Nowadays, chemistry appears to be a stakeholder in eco-
nomic issues that need to be addressed by means of sustain-
able and compliant science. Over the last few years, “green”
methodologies in accordance with economic and environ-
mental issues have been widely investigated in many re-
search areas, including catalysis in the pursuit of sustainable
catalysts. Indeed, the recovery and the reuse of catalysts and
the eviction of toxic metal waste from reaction media are
the two predominant current research axes of the scientific
community, encouraged by the strong demand from industri-
[a] Dr. D. Rosario-Amorin, Dr. L. Vellutini, Dr. K. Heuzꢀ
UMR 5255, ISM, Universitꢀ de Bordeaux
351 Cours de la Libꢀration, Talence, 33405 (France)
E-mail: k.heuze@ism.u-bordeaux1.fr
[b] Dr. D. Rosario-Amorin, Dr. L. Vellutini, Dr. K. Heuzꢀ
CNRS, UMR 5255, ISM
Talence, 33405 (France)
[c] Dr. S. Nlate
IECB-CBMN UMR 5248, Universitꢀ de Bordeaux
2 Rue Robert Escarpit, Pessac, 33607 (France)
E-mail: s.nlate@iecb.u-bordeaux.fr
[d] Dr. M. Gaboyard
Ademtech SA., Parc Scientifique Unitec 1
4 Allꢀe du Doyen Georges Brus Pessac, 33600 (France)
[e] Dr. R. Clꢀrac
CNRS, UPR 8641, Centre de Recherche Paul Pascal (CRPP)
Equipe “Matꢀriaux Molꢀculaires Magnꢀtiques”
115 avenue du Dr. Albert Schweitzer
Pessac, 33600 (France)
[f] Dr. R. Clꢀrac
ꢀ
theses catalysts have been explored, mainly in C C coupling
Universitꢀ de Bordeaux, UPR 8641
Pessac, 33600 (France)
reactions (such as Suzuki, Heck, Sonogashira, and Stille cou-
pling), as well as for hydroformylation, hydrogenation, and
olefin metathesis.[10] All of these reported reactions involved
Supporting information for this article is available on the WWW
under http://dx.doi.org/10.1002/chem.201103147.
Chem. Eur. J. 2012, 18, 3305 – 3315
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3305

the immobilization of metal-based catalysts (Pd, Pt, Rh, or
Ru). It is noteworthy that recent applications and perspec-
tives have dealt with the development of organocatalysis
and biocatalysis for the entrapment of enzymes into
MNPs.[11]
ent catalytic part. Indeed, dicyclohexylphophine palladium
complex N
(CH2PCy2)2-[PdII] was replaced by its tert-butyl
counterpart N
(CH2PtBu2)2-[PdII]. In the case of dendron 3,
AHCTUNGTRENNUNG
AHCTUNGTRENNUNG
spacer groups were introduced into the dendritic structure
of compound 1 to minimize the steric hindrance between
the catalytic sites at the dendron periphery. As for dendron
4, it represents the second generation of dendron 1, with the
Dendrimer-[12] or dendron-functionalized MNPs have re-
ceived great attention over the past decade owing to the
ability to tune their properties by functionalization.[13–15]
Each dendron is made of an anchoring site (focal point) and
branches that are terminated by catalytic sites. The synthesis
of dendron-grafted MNPs has been typically carried out by
using similar procedures to the synthesis of NPs by ligand
exchange or by direct functionalization of the nanoparticle
core or shell.[16] We have previously demonstrated[17] that
the grafting of dendritic architectures onto MNPs afforded
an enhancement of the surface functionalization with re-
spect to their grafting with linear ligands.
Herein, we studied the effect of modulation of the catalyst
structure on the reactivity and recovery of 300 nm core–
shell g-Fe2O3/polymer MNP-grafted catalysts.[18] In particu-
lar, we evaluated the effect of the dendritic structure and/or
the nature of the catalytic site toward the reactivity and re-
covery of the MNP-grafted catalysts. Previously, we studied
the efficiency of these supported catalysts in Suzuki and So-
nogashira cross-coupling reactions.[19,20] The grafting condi-
tions (solvent, dendron loading, coupling reagent, nanoparti-
cle size) were optimized using dendron 1 and its correspond-
ing supported catalyst, MNP-1. The remarkable efficiency
same catalytic site NACTHNUTRGNEUNG
(CH2PCy2)2-[PdII]. These structural
studies of two generations of dendron-grafted catalysts will
help us to evaluate the dendritic effect on catalytic perfor-
mance.
Results and Discussion
Synthesis of [Pd]-functionalized dendrons 1 and 2: First, we
ACTHNUTRGNEUNG
prepared the PdII catalyst tri-N(CH2PCy2)2-[PdII] dendron 1
as described in our previous work[19] from 4-methoxytriallyl-
methylbenzene. Tri-N
(CH2PtBu2)2-[PdII] dendron 2 was also
AHCTUNGTRENNUNG
prepared by following by a slightly modified procedure
(Scheme 2), as reported previously.[20] Thus, aminophosphine
dendrons 6a and 6b were obtained by double phosphinome-
thylation[19–21] of compound 5. The deprotection of the termi-
nal amino groups was carried out with Bu4NF, thereby lead-
ing to dendrons 7a and 7b, respectively. Complexation of
the phosphine groups of compound 7 with [PdII] led to the
corresponding metallodendrons 1 and 2, respectively, which
contained three NACTHNUTRGENNGU ACHTUGNTRENNUGN
(CH2PCy2)2-[PdII] or N(CH2PtBu2)2-[PdII]
ꢀ
and recoverability of MNP-1 in Suzuki C C cross-coupling
catalytic groups. The completion of the reaction was con-
firmed by the disappearance of the signals in the 31P NMR
spectra at d=ꢀ18.3 (for 7a) and d=12.8 ppm (for 7b),
which were attributed to the free phosphines, and the ap-
pearance of signals at d=26.7 ppm (for 1) and d=36.5 ppm
(for 2), which were attributed to the coordinated phos-
phines. All of these dendritic palladium complexes were
stable towards moisture; however, they were stored under
nitrogen to avoid slow degradation.
reactions was emphasized. Indeed, this catalyst was able to
catalyze the cross-coupling reaction between bromoarenes
(and even chloroarenes) and phenylboronic acid with high
conversions in a few hours and a catalyst loading of below
5 mol% at 658C. The recovery of the catalyst using an ex-
ternal magnet was studied and complete conversion was
maintained until at least the 25th recovery cycle. To extend
this study, herein, we report the synthesis of various support-
ed nanoparticles that have been grafted with related tri- or
nona-branched dendritic structures that contain diphosphi-
nopalladium complexes with cyclohexyl or tert-butyl ligands
at their periphery. Thus, four dendron-grafted nanoparticles
(MNP-1 to MNP-4) were synthesized from tri- or nona-
branched dendrons 1 to 4 (Scheme 1). These dendrons were
composed of a primary amine group at their focal point,
which was necessary for anchoring onto the core–shell
MNPs, and catalytic sites at their periphery. The structure of
their inner dendritic part was modulated, either by dendritic
generation or by the addition of a spacer group. Their active
catalytic sites were either composed of bis(cyclohexylamino-
Synthesis of [Pd]-functionalized dendron 3: Dendritic com-
pound 3 was a three-branched dendron that was functional-
ized by a bis(dicyclohexylaminomethylphosphine)palladiu-
m(II) NACHTUNGTRNEUNG
(CH2PCy2)2-[PdII] catalyst. Compound 3 was synthe-
sized as described in Scheme 3. The first step was the prepa-
ration of spacer group 9 from tyrosol by substitution of the
alcohol group by treatment with NaI in the presence of tri-
methylsilylchloride (TMSCl) at 708C to give iodoalcohol 8;
treatment of compound 8 with NaN3 yielded azidoalcohol 9.
Then, tri-iodo dendron 10[22] was coupled with compound 9
in the presence of K2CO3 to afford triazide dendron 11. The
latter was treated with KOH and then coupled with 2-(tri-
methylsilyl)ethoxycarbonyl (Teoc)-protected 1-iodoamino-
hexane[23] to generate dendron 12. The Staudinger reduction
of compound 12 in the presence of PPh3 and water gave tri-
amine dendron 13. Aminophosphine dendron 14 was then
obtained by the phosphinomethylation of compound 13. De-
protection of the terminal amino group was carried out with
Bu4NF at 608C to give dendron 15. Complexation of the
methylphosphine)palladium(II), N
(di-tert-butylaminomethylphosphine)palladium(II), N(CH2-
PtBu2)2-[PdII] ([PdII]=Pd
(OAc)2). These dendrons were
(CH2PCy2)2-[PdII], or bis-
ACHTUNGTRENNUNG
ACHTUNGTRENNUNG
A
ACHTUNGTRENNUNG
grafted onto a core–shell g-Fe2O3/polymer (Carboxyl-Adem-
beads 300 nm, Ademtech, France, COOH: 300 mmolgꢀ1).
Indeed, the dendritic structure of dendron 1 involved a
three-branched dendron, ended by
whilst dendron 2 had the same dendritic frame with a differ-
NACTHNGUTERNNUG
(CH2PCy2)2-[PdII]
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Metallodendritic Core–Shell g-Fe2O3 Nanoparticles
FULL PAPER
Scheme 1. Synthesis of grafted core–shell g-Fe2O3-polymer MNPs (Carboxyl-Adembeads, 300 nm) MNP-1–MNP-4 from metallodendritic catalysts 1–4,
respectively.
phosphine groups of compound 15 with PdII gave metallo-
dendron 3, which contained three N
(CH2PCy2)2-[PdII] cata-
Synthesis of [Pd]-functionalized dendron 4: The nona-
branched dendron 4 was functionalized at its periphery by
AHCTUNGTRENNUNG
lytic groups. The completion of the reaction was determined
by 31P NMR spectroscopy with the disappearance of a signal
at d=ꢀ17.7 ppm, which was assigned to the free phosphine,
and the appearance of a signal at d=27.7 ppm, which was
assigned to the coordinated phosphine.
bis(dicyclohexylaminomethylphosphine)palladium(II),
N-
A
CHTUNGTRENNUNG
shown in Scheme 4. Coupling of triazido phenol dendron 16
with compound 10[22] in the presence of K2CO3 in DMF
yielded dendron 17, which contained nine peripheral azide
groups. Nona-azido dendron 17 was treated with KOH and
then coupled with Teoc-protected 1-iodoaminohexane[23] to
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3307

D. Rosario-Amorin, S. Nlate, K. Heuzꢀ et al.
with [PdII] led to metalloden-
dron 4, which contained nine
N
G
catalytic
groups. Completion of this
final step was confirmed by the
disappearance of the free-
phosphine
signal
in
the
31P NMR spectrum at d=
ꢀ18.4 ppm and the appearance
of the coordinated-phosphine
signal at d=27.3 ppm.
The optimization of the
grafting of 1 versus 2 versus 3
versus
Fe2O3/polymer
was evaluated through the cat-
alytic efficiencies of their cor-
responding MNPs, (MNP-1–
4
onto core–shell g-
nanoparticles
Scheme 2. Synthesis of dendrons 1 and 2. Reagents and conditions: i) HCHO, HPR2, MeOH/toluene 2:1?,
12 h, 708C!RT; ii) Bu4NF, THF, 5 h, 608C; iii) Pd(OAc)2, CH2Cl2, 2 h, RT.
AHCTUNGTRENNUNG
ꢀ
generate dendron 18. Azido groups of compound 18 were
reduced into primary amine groups by using the Staudinger
reduction described previously, thereby leading to nona-
amine dendron 19. Aminophosphine dendron 20 was then
obtained by the phosphinomethylation of compound 19 in
the presence of HPCy2 and paraformaldehyde. The depro-
tection of the terminal amino group of compound 20 was
carried out with Bu4NF at 608C, thereby leading to dendron
21. Complexation of the phosphine groups of compound 21
MNP-4) in Suzuki C C cross-coupling reactions.
Grafting of the dendrons onto MNPs: Core–shell g-Fe2O3/
polymer 300 nm superparamagnetic nanoparticles (Carbox-
yl-Adembeads 300 nm, Ademtech, France, COOH:
300 mmolgꢀ1 of particles) were used as MNP supports.[24]
The grafting of dendrons 2–4 were performed and optimized
as reported previously for dendron 1.[19] By using covalent
interactions, the terminal amine groups at the focal point of
Scheme 3. Synthesis of dendron 3. Reagents and conditions: i) TMSCl, NaI, MeCN, 708C, 24 h; ii) NaN3, DMF, RT, 12 h; iii) 9, K2CO3, DMF, RT, 48 h;
iv) K2CO3, H2O, DMF, 408C, 48 h; v) KOH, DMF, RT, 20 min; vi) DMF, RT, 4 h; vii) PPh3, H20, THF, 408C, 12 h; viii) HCHO, HPCy2, MeOH/toluene
2:1, 12 h, 708C!RT; ix) Bu4NF, THF, 608C, 5 h; x) Pd
ACHTUGNTRENNUN(G OAc)2, CH2Cl2, RT, 20 min.
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Metallodendritic Core–Shell g-Fe2O3 Nanoparticles
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Scheme 4. Synthesis of dendron 4. Reagents and conditions: i) 10, K2CO3, DMF, RT, 72 h; ii) K2CO3, H2O, DMF, 408C, 48 h; iii) KOH, Teoc-protected 6-
iodo-aminohexane, DMF, RT, 3 h; iv) PPh3, H2O, THF, 408C, 12 h; v) HCHO, HPCy2, MeOH/toluene 2:1, 12 h, 708C!RT; vi) Bu4NF, THF, 608C, 5 h;
vii) PdACHTUNGTRENNUNG(OAc)2, CH2Cl2, RT, 2 h.
dendrons 1–4 were coupled with COOH groups on the
MNP polymer shells. The grafting solvents and the coupling
agents were chosen to obtain optimal colloidal states of
both the starting MNPs and of the resulting grafted MNPs.
This parameter could be directly evaluated by the catalytic
activity of the grafted MNPs, because it had a direct effect
on the catalytic activity. For all of the dendrons studied, the
grafting was performed in organic/aqueous media with
MeOH/Tx[25] (1:2) in the presence of carbodiimide CHMC
(CHMC=N-cyclohexyl-N’-(2-morpholinoethyl)carbodiimide
metho-p-toluenesulfonate) as a coupling agent, with 10
equivalents of dendron for compounds 1–3 and 4 equiva-
lents of dendron for compound 4, overnight at room temper-
ature. Indeed, in our previous work, the optimized dendron
loading during the grafting procedure was found to be 10
equivalents for three branched dendrons.[19] For comparison,
this parameter needed to be re-evaluated in the case of
nona-branched dendrons. The loading of dendron 4 was in-
creased from 2 to 8 equivalents, based on the number of ac-
cessible free carboxylic acid groups on the polymer shell.[26]
The grafting efficiency was then estimated by performing a
Suzuki reaction (Figure 1). However, to perform these ex-
periments, a preliminary dissolution of the dendron in DMF
(30 mm) was necessary to improve its solubility in the graft-
ing reaction medium. ICP-MS (inductively coupled plasma
mass spectroscopy) measurements showed an effective graft-
ing of 60% for three branched dendrons 1–3, which corre-
sponded to 544–552 mmol of catalytic sites per gram of parti-
cles and an effective grafting of 19.5% for nona-branched
dendron 4,[27] which corresponded to 526 mmolgꢀ1. It is note-
worthy that this number of catalytic sites was about twice
the initial amount of free COOH group available on the
Figure 1. Catalytic activity of MNP-4 versus the number of equivalents of
dendron 4 used during the grafting reaction. Catalytic reactions were per-
formed with 0.125 mg MNP, according to the general procedure (see the
Experimental Section).
MNP surface (300 mmolgꢀ1). We should also note that the
amount of catalytic sites at the MNPs surface was approxi-
mately the same whichever dendron was used. We suggested
that, under these conditions, we had reached the best graft-
ing as possible.
Catalytic performance of dendron-grafted MNPs in Suzuki
ꢀ
C C cross-coupling reactions: First, the effect of the ligand
on the catalytic performance of the grafted catalysts was
studied. Thus, the catalytic activity of MNP-1, which con-
tained PCy2 ligands, was compared to the reactivity of
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D. Rosario-Amorin, S. Nlate, K. Heuzꢀ et al.
Table 2. Dendritic structural effect: comparison of the catalytic efficien-
MNP-2, which contained PtBu2 ligands. Compounds MNP-1
and MNP-2 had the same tridentate dendritic structures and
only the nature of the phosphine ligand at the catalytic sites
was different. Their reactivities were studied for a range of
aryl iodide and bromide substrates and for phenylboronic
acid (Table 1).
cies of MNP-1, MNP-3, and MNP-4 in the Suzuki cross-coupling re-
AHCTUNGTRENNUNG
action.[a]
Aryl
halide
Aryl boronic
acid
MNP-1
Conv.
[h] [%]
MNP-3
Conv.
[h] [%]
MNP-4
Conv.
[h] [%]
t
t
t
1
2
1
2
100
1
100
1
1
100
100
Table 1. Ligand effect: comparison of the catalytic activities of MNP-1
and MNP-2 in the Suzuki cross-coupling reaction.[a]
89 0.5 100
3
2
76
1
1
98
2
2
91
94
Aryl
halide
Aryl boronic
acid
MNP-1
Conv.
MNP-2
Conv.
t
t
[h]
[%]
100
89
[h]
[%]
100
99
4
5
6
4
1
1
>99
100
1
2
1
2
1
1
100 0.5 100
100 0.5 100
0.5 100
0.5 100
3
2
76
2
99
7
8
1
4
93
92
1
1
100
92
1
2
100
91
4
5
6
4
1
1
99
100
100
2
100
100
92
0.5
0.5
9
4
4
68
43
2
–
100
–
3
3
98
88
7
4
68
3
96
10
[a] Reaction conditions: see the Experimental Section. T=658C, THF/Tx
(1:9), 2.4 mol% [Pd]. Conversions were determined by GC analysis.
[a] Reaction conditions: see the Experimental Section. T=658C, THF/Tx
(1:9), 2.4 mol% [Pd]. Conversions were determined by GC analysis.
dered aryl boronic acid (Table 2, entries 7–9). The second-
generation catalyst MNP-4 (nona-branched analogue of
MNP-1) also showed improved reactivity, but to a lesser
extent. Indeed, the increased number of catalytic sites at the
dendron periphery allowed the complete conversion of steri-
cally hindered substrates in 1–2 h (Table 2, entries 7–9).
However, the most-significant improvement was with MNP-
3, in which the dendritic branches were lengthened by
spacer groups.
Catalyst MNP-2, which contained di-tert-butyl phosphine
ligands, appeared to be much more efficient than its dicyclo-
hexylphosphine counterpart, MNP-1: complete conversion
of bromobenzene was obtained within 1 h with MNP-2
whilst 2 h was necessary to afford 89% conversion with
MNP-1 (Table 1, entry 2). This difference in reactivity was
more pronounced for activated and sterically hindered aryl
bromide substrates (Table 1, entries 3–7): for example, with
2,6-dimethylbenzene (Table 1, entry 7) 96% conversion was
reached in 3 h with MNP-2 whereas 4 h was required to
afford 68% conversion with MNP-1.
To investigate the dendritic effect, we compared the cata-
lytic performances of MNP-1 and MNP-3 to those of MNP-
4. These three MNPs all contained the same catalytic groups
and PCy2 ligands. Thus, tri-branched MNP-3, which con-
tained a spacer group, was compared to MNP-1, and to
MNP-4, which was the nona-branched analogue of MNP-1.
These structural modifications had a dramatic effect on the
catalytic performance of these catalysts (Table 2). The re-
sults clearly indicated an increase in the catalytic reactivities
for MNP-3 and MNP-4 with respect to MNP-1: for MNP-3
(with spacer groups), a decrease in the steric hindrance be-
tween catalytic sites, owing to lengthening of the branches,
improved its catalytic performance compared to MNP-1.
This improvement was noted for activated (Table 2, entries 5
and 6) and deactivated aryl bromide substrates (Table 2, en-
tries 3, 4, 8, and 10) and in the presence of sterically hin-
Recovery of dendron-grafted MNPs: The recovery proce-
dure of MNP-1–MNP-4 was optimized by using an external
permanent magnet.[28] Thus, once the reaction had been
completed, a magnet was used to separate the MNPs from
the supernatant. After the separation was complete, and
when the particles were held against the walls of the vial,
the supernatant was removed. This procedure was repeated
after each catalytic cycle. An interesting feature of this soft-
separation technique was that it ensured minimal loss and
easy separation of the grafted MNPs as well as the reusabili-
ty of the catalyst. Thus, the recovery of MNP-1–MNP-4
from the coupling reaction between iodobenzene and
phenyl boronic acid (Figure 2) was investigated.[29] In the
same way as for MNP-1,[19] almost no significant loss of ac-
tivity was observed for all of the catalysts, even after 25
cycles. Remarkably, the conversions remained between 95
and 100% up to the 25th cycle. The slight decrease in reac-
tivity was probably due a progressive aggregation of the par-
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Metallodendritic Core–Shell g-Fe2O3 Nanoparticles
FULL PAPER
the low amount of Pd leaching (0.36% loss of [Pd] per
cycle; 14 ppm [Pd] in thr crude product) and their efficient
recovery (0.006% loss of Fe per cycle; 4 ppm Fe in the
crude product). Therefore, nanocatalysts appear to be prom-
ising tools both economically and environmentally for the
development of sustainable catalysts in accordance with
green methodologies.
Experimental Section
All reactions were performed under a nitrogen atmosphere using stan-
dard glassware. The starting materials were obtained commercially and
used without further purification. The solvents were dried according to
standard procedures and saturated with nitrogen. 1H, 13C, and 31P NMR
spectra were recorded on the following spectrometers: Bruker DPX 200
FT NMR spectrometer (1H: 200.16, 13C: 50.33, 31P: 81.02 MHz), Bruker
AC 250 FT NMR spectrometer (1H: 250.13, 13C: 62.90 MHz), Bruker
Avance 300 FT NMR spectrometer (1H: 300.13, 13C: 75.46, 31P:
121.49 MHz), Bruker Avance II 400 FT NMR spectrometer (1H: 400.13,
13C: 100.62, 31P: 161.97 MHz). Chemicals shifts are reported in parts per
million (d) against referenced solvent signals. MALDI-TOF spectra were
performed by CESAMO (Universitꢀ Bordeaux 1, France) on a Voyager
mass spectrometer (Applied Biosystems). The instrument was equipped
with a pulsed N2 laser (337 nm) and a time-delayed extracted-ion source.
Spectra were recorded in positive-ion mode by using a reflectron and
with an accelerating voltage of 20 kV. Elemental analyses were carried
out at the CNRS-Vernaison, France. GC spectra were recorded on a
Varian star 3900 gas chromatograph equipped with a fused-silica capillary
column heated gradually from 408C to 2508C (rate 108C minꢀ1) with He
as a vector gas at a column head pressure of 10 psi. An FID detector was
used. Yields were calculated by integration of the product peaks (Star
chromatography workstation 5.50) after determination of the response
coefficient of each product versus each bromoarene reagent. For column
chromatography, Merck silica gel 60 (230–400 mesh) was used.
Figure 2. Recovery of grafted MNP-1–MNP-4. Reaction conditions: see
the Experimental Section, with grafted MNP materials (5 mg, 4.8 mol%
[Pd]). The mixture was stirred for 1 h at 658C in THF/Tx (1:9).
ticles in the reaction medium as the number of recovery
cycles increased. This aggregation mostly resulted from
slight alterations in the polymer shells of the particles.
Indeed, in the case of MNP-1, the amount of particles lost
between each cycle was negligible: ICP-MS analysis showed
4 ppm of Fe in the crude product (0.006% loss of Fe per
cycle).
Also, the leaching or decomposition, as often observed in
these catalytic systems,[29] was weak: 14 ppm of [Pd] in the
crude product by ICP-MS (0.36% loss of [Pd] per cycle).
Compound 1, 5, 6a, and 7a: Compounds 1, 5, 6a, and 7a were synthe-
sized according to a literature procedure, see Ref. [19].
Conclusion
Compound 2, 6b and 7b: Compounds 2, 6b, and 7b were synthesized ac-
cording to a literature procedure, see Ref. [20].
This work has highlighted the widespread use of dendritic
structures for the grafting of core–shell g-Fe2O3/polymer
300 nm superparamagnetic nanoparticles. We have synthe-
sized highly active catalysts for a range of arylbromo deriva-
tives. The presence of chelating diphosphine groups on the
dendron ensured their stability and was a key feature in
their efficiency. The catalytic performance of the nanocata-
Compound 3: A mixture of compound 15 (1.14 g, 0.57 mmol) and Pd-
AHCTUNGTREN(GUNN OAc)2 (384 g, 1.71 mmol) was stirred in CH2Cl2 (15 mL) at RT under an
inert atmosphere for 20 min. Then, the mixture was evaporated and the
product dried under vacuum to give compound 3 as a brown powder
1
3
(1.5 g, 100%). H NMR (200 MHz, CD2Cl2, 258C): d=7.09 (d, J
8 Hz, 8H; CHar), 6.80 (d, 3J
(H,H)=8 Hz, 8H; CHar), 3.86 (m, 8H;
CH2O), 2.78 (m, 6H; CH2CH2N), 2.7–2.5 (m, 20H;
ACHTUNGTRENNUNG(H,H)=
AHCTUNGTRENNUNG
NCH2P+CH2NCH2P+CH2NH2), 1.94 (s, 18H; CH3(OAc)), 1.7–1.1 ppm (m,
152H; CH(Cy)+CH2(Cy)+CH2); 13C NMR (75.46 MHz, CD2Cl2, 258C): d=
177.2 (Cq(OAc)), 158.2 (COar), 39.0 (Cq(ar)), 31.2 (Cq(ar)), 130.0 (CHar), 127.9
(CHar), 114.8 (CHar), 68.9 (CH2O), 64.4 (CH2NCH2P), 48.6 (d; CH2P),
35.8 (CH2Cq), 35.5 (CH3(OAc)), 31.9 (CH2CH2N), 29.1 (d,
CH2(Cy)+PCH(Cy)), 27.5 (CH2(Cy)), 26.3 (CH2(Cy)), 24.1 ppm (CH2);
31P NMR (81.02 MHz, CD2Cl2, 258C): d=26.4 ppm; elemental analysis
calcd (%) for C136H222N4O16P6Pd3: C 61.1, H 8.37, N 2.1, Pd 11.9; found:
C 59.9, H 7.5, N 2.0, Pd 12.7.
ꢀ
lysts was optimized for the Suzuki C C cross-coupling reac-
tion, and we found that compound MNP-3, which had long
dendritic branches, was the most-suitable catalyst. Indeed,
its catalytic sites were kept apart from each other, thereby
preventing the steric hindrance that is often responsible for
lower catalytic efficiency. Furthermore, we have demonstrat-
ed the remarkable importance of adjusting the dendritic
structures and the nature of the phosphine to optimize the
catalytic efficiency of the grafted MNPs. Interestingly, all of
these grafted catalysts could be recovered—and efficiently
reused—by magnetic separation with no significant loss of
reactivity, even after 25 cycles. These results indicated a
good stability of these MNP catalysts towards the reaction
medium, which was converse to the precipitation techniques
we have previously experienced.[31] In fact, these grafted cat-
alysts were stable and environmentally friendly, as shown by
Compound 4: A mixture of compound 22 (2.5 g, 0.5 mmol) and PdACHTUNGTRENNUNG(OAc)2
(1.02 g, 4.5 mmol) was stirred in CH2Cl2 (10 mL) at RT under an inert at-
mosphere for 2 h. Then, the reaction mixture was evaporated and the
product was dried under vacuum to give compound 4 as a brown powder
(3.5 g, 100%). 1H NMR (400 MHz, CD2Cl2, 258C): d=7.18 (m, 8H;
CHar), 6.84 (m, 8H; CHar), 3.87 (m, 8H; CH2O), 2.5–2.2 (m, 56H;
NCH2P+CH2NCH2P+CH2NH2), 1.90 (s, 54H; CH3(OAc)), 1.8–1.1 ppm (m,
452H; CH2); 13C NMR (100 MHz, CD2Cl2, 258C): d=157.6 (COar), 137.7
(Cq(ar)), 127.5 (CHar), 114.2 (CHar), 68.4 (CH2O), 63.5 (CH2NCH2P), 59.0
(CarCq), 48.6 (CH2P), 43.1 (CH2Cq+CH2NH2), 35.5 (CH3(OAc)), 30.2
(PCH(Cy)), 29.6 (CH2(Cy)), 27.2 (CH2(Cy)), 26.2 ppm (s, CH2(Cy)); 31P NMR
Chem. Eur. J. 2012, 18, 3305 – 3315
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3311

D. Rosario-Amorin, S. Nlate, K. Heuzꢀ et al.
(160 MHz, CD2Cl2, 258C): d=27.3 ppm; elemental analysis calcd (%) for
340H588N10O40P18Pd9: C 58.5, H 8.5, P 8.0, Pd 13.7; found: C 56.1, H 8.2,
P 7.8, Pd 13.7.
(CH2), 23.7 (CH2), 17.9 (CH2Si), ꢀ1.3 ppm (CH3Si); MS (MALDI): m/z
calcd for C52H72N10O6Si+Na+: 983.58 [M+Na]+; found: 983.53; elemental
analysis calcd (%) for C52H72N10O6Si: C 65.0, H 7.6, N 14.5; found:
C 65.3, H 8.0, N 13.2.
C
Compound 8:
A mixture of tyrosol (4 g, 28.9 mmol), NaI (21.6 g,
145 mmol), TMSCl (18.4 mL, 145 mmol), and CH3CN (25 mL) was
stirred at 708C in a sealed Schlenk tube for 24 h. The solvent was re-
moved and the crude product was dissolved in water (20 mL) and ex-
tracted with EtO2 (4ꢂ20 mL). The organic layers were collected, washed
with a saturated aqueous solution of Na2S2O3, and dried over MgSO4.
The solvent was removed under reduced pressure to give compound 8 as
a white solid (6.8 g, 95%). 1H NMR (250 MHz, CDCl3, 258C): d=7.06
Compound 13: A mixture of triazo dendron 12 (990 mg, 1.03 mmol),
PPh3 (4.05 g, 15.4 mmol), and H2O (20 mL, 15.5 mmol) in THF (5 mL)
was heated to 408C for 12 h. Then, the solvent was removed under re-
duced pressure. The residue was dissolved in a minimum volume of
CH2Cl2, and pentane was added to form a precipitate, which was washed
several times with pentane to yield compound 13 as a light-yellow
powder (630 mg, 69%). 1H NMR (200 MHz, CDCl3, 258C): d=7.07 (d,
(d, 3J
(t, 3J
A
U
3J
3J
A
ACHTUNGTRENN(NUG H,H)=8.5 Hz, 8H; CHar), 4.14 (t,
A
U
ACHTUNGTRENNUNG
CH2CH2I); 13C NMR (62.90 MHz, CDCl3, 258C) d=154.4 (COar), 133.1
(Cq(ar)), 129.7 (CHar), 115.6 (CHar), 39.6 (CH2), 6.6 ppm (CH2I); MS (EI):
m/z (%): 247.8 (12) [M]+, 120.8 (100) [MꢀI]+.
A
E
2.66 (t, 3J
3J
(50.33 MHz, CDCl3, 258C) d=157.4 (C=O+COar), 156.8 (COar), 138.1
(Cq(ar)), 131.5 (Cq(ar)), 129.6 (CHar), 127.3 (CHar), 114,4 (CHar), 113.9
(CHar), 68.2 (CH2O), 67.6 (CH2O), 62.7 (CH2OCO), 43.5 (CH2NH2), 41.8
(CarCq), 40.8 (CH2NH), 38.9 (CH2CH2NH2), 33.6 (CH2Cq), 29.9 (CH2),
29.2 (CH2CH2O), 26.4 (CH2), 25.7 (CH2), 23.6 (CH2), 17.7 (CH2Si),
ꢀ1.5 ppm (CH3Si); MS (MALDI): m/z calcd for C52H78N4O6Si+2H+:
442.80 [M+2H]+; found: 442.79.
Compound 9: A mixture of compound 8 (1.6 g, 6.45 mmol) and NaN3
(2.1 g, 32.2 mmol) was stirred in DMF (5 mL) at RT for 12 h under a ni-
trogen atmosphere. Water (15 mL) was added and the mixture was ex-
tracted with Et2O (3ꢂ20 mL). The organic layers were collected, washed
with water (10ꢂ20 mL), and dried over anhydrous MgSO4. The solvent
was removed under reduced pressure to afford compound 9 as a brown
oil (1.0 g, 95%). 1H NMR (250 MHz, CDCl3, 258C): d=7.11 (d, 3J-
A
G
Compound 14: A mixture of dicyclohexylphosphine (1.56 g, 47.89 mmol)
and paraformaldehyde (1.25 g, 41.6 mmol) in MeOH/toluene (2:1, 5 mL)
was heated to 708C for 10 min. A solution of triamino dendron 13
(900 mg, 1.02 mmol) in MeOH/toluene (2:1, 10 mL) was added, and the
mixture was stirred at 708C for 10 min and then at RT for 12 h. The
volume of the reaction mixture was reduced under vacuum and MeOH
was added. The residue was isolated from the medium, washed several
times with MeOH, and dried under vacuum to yield compound 14 as a
light-gray powder (1.6 g, 73%). 1H NMR (250 MHz, CDCl3, 258C): d=
E
ACHTUNGTRENNUNG
13C NMR (62.90 MHz, CDCl3, 258C) d=154.1 (COar), 130.0 (Cq(ar)), 129.8
(CHar), 115.4 (CHar), 52.4 (CH2N3), 34.1 ppm (CH2CH2N3); MS (EI): m/z
(%): 162.9 (16) [M]+, 106.8 (100) [MꢀCH2N3]+.
Compound 11: A mixture of azoture 9 (1.0 g, 6.13 mmol) and K2CO3
(1.69 g, 12.2 mmol) was stirred in dry DMF (3 mL) at RT for 20 min. A
solution of tri-iodo dendron 10 (1.36 g, 2.04 mmol) in DMF (3 mL) was
added under an inert atmosphere and the reaction mixture was stirred at
RT for 48 h. Then, water (5 mL) and K2CO3 (2.5 g, 18.4 mmol) were
added and the resulting mixture was stirred at 408C for 48 h. Water
(20 mL) was added and the product was extracted with Et2O. The organic
layers were collected, washed with water (10ꢂ20 mL), and dried over an-
hydrous MgSO4. Solvent was removed under reduced pressure to give a
brown oil, which was purified by column chromatography on silica gel
(petroleum ether/Et2O 90:10, then Et2O) to yield compound 11 as a
7.06 (d, 3J
(H,H)=7 Hz, 8H; CHar), 6.73 (d, 3J
ACHTUGTNRNENUG CAHUTGNTREN(NNGU H,H)=7 Hz, 8H; CHar),
4.11 (t, 3J
AHCTUNGTRENNUNG
2H; CH2NH), 2.90 (t, 6H; CH2CH2NH2), 2.79 (s, 12H; NCH2P) 2.63 (t,
6H; CH2NCH2P), 1.7–1.1 (m, 152H; CH(Cy)+CH2(Cy)+CH2), 0.97 (t, 2H;
CH2Si), 0.00 ppm (s, 9H; CH3Si); 13C NMR (75.46 MHz, CDCl3, 258C)
d=157.3 (C=O+COar), 156.9 (COar), (132.6 (Cq(ar)), 129.8 (CHar), 128.5
(CHar), 114,3 (CHar), 68.5 (CH2O), 62.8 (CH2OCO), 58.1 (CH2NCH2P),
52.6 (CH2P), 41.8 (CarCq), 40.7 (CH2NH), 33.7 (3C; CH2Cq), 33.0 (d,
PCH(Cy)), 31.3 (3C; CH2CH2N), 29.8 (dd; CH2(Cy)), 27.6 (CH2(Cy)), 26.7
(CH2(Cy)), 25.9 (CH2), 23.9 (CH2), 17.8 (CH2Si), ꢀ1.4 ppm (CH3Si);
31P NMR (81.02 MHz, CDCl3, 258C, H3PO4) d=ꢀ17.7 ppm; MS
(MALDI): m/z calcd for C130H216N4O6P6Si+H+: 2144.49 [M+H]+; found:
brown oil (1.09 g, 74%). 1H NMR (250 MHz, CDCl3, 258C): d=7.09 (d,
3J
A
N
(H,H)=8 Hz, 8H; CHar), 3.86 (t, 3J-
ACHTUGNTREN(UNNG H,H)=7 Hz, 6H; CH2N3), 2.81 (t,
3
ACHTUNGTRENNUNG
(75.46 MHz, CDCl3, 258C) d=157.8 (COar), 154.8 (COar), 138.2 (Cq(ar)),
129.9(Cq(ar)), 129.7 (CHar), 128.2 (CHar), 115,6 (CHar), 114.7 (CHar), 68.3
(CH2O), 52.7 (CH2N3), 42.0 (CarCq), 34.5 (CH2CH2N3), 33.7 (CqCH2),
23.6 ppm (CH2CH2O); elemental analysis calcd (%) for C40H47N9O4:
C 66.9, H 6.6; found: C 66.8, H 6.9.
2143.86; elemental analysis calcd (%) for
H 10.1, N 2.6; found: C 70.9, H 10.0, N 2.6.
C130H216N4O6P6Si: C 72.8,
Compound 15: A mixture of compound 14 (1.58 g, 0.74 mmol), tetrabuty-
lammonium fluoride (1m in THF, 7.4 mL, 7.4 mmol), and THF (10 mL)
was stirred under an inert atmosphere at 608C for 5 h. Then, the solvent
was removed under reduced pressure and the residue was washed several
times with ice-cold MeOH. The product was dried under vacuum to give
compound 15 as a white powder (1.08 g, 73%). 1H NMR (250 MHz,
Compound 12: Triazo dendron 11 (1.44 g, 2 mmol) and KOH (337 mg,
6 mmol) were dissolved in dry DMF (4 mL) in a Schlenk tube and stirred
for 20 min at RT. A solution of Teoc-protected 6-iodo-aminohexane
(743 mg, 2 mmol) in DMF (2 mL) was added to the reaction mixture,
which was then stirred at RT for 4 h. Water was added and the product
was extracted with CH2Cl2. The organic layer was washed several times
with water, dried over MgSO4, and evaporated under reduced pressure.
The crude product was purified by column chromatography on silica gel
(petroleum ether/Et2O, 90:10 to 50:50) to give compound 12 as a light-
yellow oil (1.4 g, 73%). 1H NMR (250 MHz, CDCl3, 258C): d=7.12 (m,
CDCl3, 258C): d=7.11 (d, 3J(H,H)=8 Hz, 8H; CHar), 6.78 (d, 3J
ACTHNUTRGENNUG ACHTUNGTRENNUNG(H,H)=
8 Hz, 8H; CHar), 3.9–3.8 (m, 8H; CH2O), 2.9 (m, 6H; CH2CH2NH2),
2.84 (s, 12H; NCH2P), 2.7–2.6 (m, 8H; CH2NCH2P+CH2NH2), 1.8–
1.1 ppm (m, 152H; CH(Cy)+CH2(Cy)+CH2); 13C NMR (50.33 MHz, CDCl3,
258C) d=157.4 (COar), 144.9 (Cq(ar)), 132.1 (Cq(ar)), 129.8 (CHar+Cq(ar)
)
127.5 (CHar), 114,3 (CHar), 68.5 (CH2O), 58.1 (CH2NCH2P), 52.6 (CH2P),
42.1 (CH2NH2), 33.5 (CH2Cq), 33.0 (d, PCHCy), 31.3 (CH2CH2N), 29.8
(dd; CH2(Cy)), 27.4 (CH2(Cy)), 26.7 (s; CH2(Cy)), 23.9 ppm (CH2); 31P NMR
(81.02 MHz, CDCl3, 258C, H3PO4) d=ꢀ17.7 ppm; elemental analysis
calcd (%) for C124H204N4O4P6: C 74.4, H 10.3, N 2.8; found: C 72.4,
H 10.2, N 3.0.
8H; CHar), 6.82 (m, 8H; CHar), 4.64 (brs, 1H; NH), 4.15 (t, 3J
8.5 Hz, 2H; CH2OCO), 3.93 (t, 3J(H,H)=6 Hz, 2H; CH2O), 3.86 (t, 3J-
(H,H)=7 Hz, 6H; CH2O), 3.44 (t, 3J
(H,H)=7 Hz, 6H; CH2N3), 3.17 (q,
3J(H,H)=6 Hz, 2H; CH2NH), 2.81 (t, 3J
(H,H)=7 Hz, 6H; CH2CH2N3)
1.8–1.2 (m, 20H; CH2), 0.97 (t, 3J
(H,H)=8.5 Hz, 2H; CH2Si), 0.04 ppm
ACHTUNGTRNE(NUNG H,H)=
AHCTUNGTRENNUNG
N
ACHTUNGTRENNUNG
E
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
(s, 9H; CH3Si); 13C NMR (75.46 MHz, CDCl3, 258C) d=157.8 (C=
O+COar), 156.8 (COar), 138.6 (Cq(ar)), 130.0 (Cq(ar)), 129.8 (CHar), 127.5
(CHar), 114,7 (CHar), 114.1 (CHar) 68.4 (CH2O), 67.9 (CH2O), 63.0
(CH2OCO), 52.8 (CH2N3), 42.1 (CarCq), 41.0 (CH2NH), 34.6
(CH2CH2N3), 33.8 (CH2Cq), 30.1 (CH2), 29.3 (CH2), 26.6 (CH2), 26.0
Compound 17: A mixture of triazo dendron 16 (3.06 g, 8.42 mmol) and
K2CO3 (1.75 g, 12.6 mmol) was stirred in dry DMF (2 mL) at RT for
20 min. A solution of triiodo dendron 10 (1.27 g, 1.87 mmol) in DMF
(3.5 mL) was added under an inert atmosphere and the reaction mixture
was stirred at RT for 72 h. Then water (6.5 mL) and K2CO3 (3.25 g,
3312
www.chemeurj.org
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 3305 – 3315

Metallodendritic Core–Shell g-Fe2O3 Nanoparticles
FULL PAPER
23.5 mmol) were added and the resulting mixture was heated to 408C for
48 h. Water (20 mL) was added and the product was extracted with Et2O.
The organic layers were collected, washed with water (10ꢂ20 mL), and
dried over anhydrous Na2SO4. Solvent was removed under reduced pres-
sure to give a brown oil, which was purified by column chromatography
on silica gel (petroleum ether/Et2O 70:30, then Et2O/CH2Cl2 95:5) to
yield a light-brown oil (1.88 g, 77%). 1H NMR (250 MHz, CDCl3, 258C):
d=7.18–7.05 (m, 8H; CHar), 6.83 (m, 8H; CHar), 3.88 (t, 6H; CH2O),
3.22 (t, 18H; CH2N3), 1.7–1.5 (m, 24H; CH2), 1.5–1.2 ppm (m, 24H;
CH2); 13C NMR (50.33 MHz, CDCl3, 258C) d=157.1 (COar), 137.4
(Cq(ar)), 127.2 (CHar), 114,3 (CHar), 68.3 (CH2O), 52.0 (CH2N3), 42.1
(CarCq), 34.5 (CqCH2), 23.3 ppm (CH2); MS (MALDI): m/z calcd for
C64H89N27O4+Na+: 1322.75 [M+Na]+; found: 1322.71.
(CHar), 68.2 (CH2O), 67.7 (CH2O), 62.9 (CH2OCO), 56.8 (CH2NCH2P),
52.3 (CH2P), 42.5 (CarCq), 41.0 (CH2NH) 35.5 (CH2Cq), 32.9 (d; PCH(Cy)),
29.8 (dd; CH2(Cy)), 27.5 (CH2(Cy)), 26.7 (CH2(Cy)), 24.0 (CH2), 20.2 (CH2),
17.8 (CH2Si), ꢀ1.4 ppm (CH3Si); 31P NMR (81.02 MHz, CDCl3, 258C,
H3PO4)
d=ꢀ18.2 ppm;
elemental
analysis
calcd
(%)
for
C
310H546N10O6P18Si: C 73.0, H 10.8, N 2.75, P 10.3; found: C 71.9, H 10.8,
N 2.6, P 10.5.
Compound 21: A mixture of compound 20 (3.5 g, 0.69 mmol), tetrabuty-
lammonium fluoride (1m in THF, 6.9 mL, 6.9 mmol), and THF (10 mL)
was heated under an inert atmosphere to 608C for 5 h. Then, the solvent
was removed under reduced pressure and the residue was washed several
times with ice-cold MeOH. The product was dried under vacuum to give
compound 21 as a white powder (2.75 g, 81%). 1H NMR (200 MHz,
CDCl3, 258C): d=7.12 (m, 8H; CHar), 6.73 (m, 8H; CHar), 3.80 (m, 8H;
CH2O), 2.68 (s, 36H; NCH2P), 2.61 (m, 20H; CH2NCH2P+CH2NH2),
1.7–1.0 ppm (m, 452H; CH(Cy)+CH2(Cy)+CH2); 13C NMR (75.46 MHz,
CDCl3, 258C): d=156.7 (COar), 137.8 (Cq(ar)), 127.5 (CHar), 113.6 (CHar),
67.9 (CH2O), 56.8 (CH2NCH2P), 52.4 (CH2P) 42.6 (CarCq), 35.6 (CH2Cq),
33.0 (d; PCH(Cy)), 30.1 (dd; 72C, CH2(Cy)), 27.5 (CH2(Cy)), 26.7 (CH2(Cy)),
24.3 (CH2), 20.3 (CH2), 19.9 ppm (CH2); 31P NMR (81.02 MHz, CDCl3,
258C, H3PO4) d=ꢀ18.4 ppm; elemental analysis calcd (%) for
Compound 18: Nona-azo dendron 17 (551 mg, 0.42 mmol) and KOH
(120 mg, 2.14 mmol) were dissolved in dry DMF (3.5 mL) in a Schlenk
tube and stirred for 15 min at RT. A solution of Teoc-protected 6-iodo-
aminohexane[32] (157 mg, 0.42 mmol) in DMF (2 mL) was added to the
reaction mixture, which was then stirred at RT for 3 h. Water was added
and the product was extracted with CH2Cl2. The organic layer was
washed several times with water, dried over MgSO4, and evaporated
under reduced pressure to give compound 18 as a beige oil (531 mg,
81%). 1H NMR (300 MHz, CDCl3, 258C): d=7.16 (d, 3J
8H; CHar), 6.82 (d, 3J
(H,H)=8 Hz, 8H; CHar), 4.67 (brs, 1H; NH), 4.14
(t, 3J
(H,H)=8 Hz, 2H; CH2OCO), 3.95–3.8 (m, 8H; CH2O), 3.2–3.0 (m,
20H; CH2NH+CH2N3), 1.84–1.66 (m, 8H; CH2), 1.66–1.3 (m, 30H;
CH2), 1.3–1.1 (m, 18H; CH2), 0.97 (t, 3J
(H,H)=8 Hz, 2H; CH2Si),
ACHTUNGTRENUN(NG H,H)=8 Hz,
C
304H534N10O4P18: C 73.7, H 10.9, P 11.3; found: C 71.8, H 10.7, P 11.05.
ACHTUNGTRENNUNG
General procedure for the grafting of dendrons 1–4 onto core–shell
MNPs: Carboxyl-Adembeads 300 nm nanoparticles[33] (250 mL, 2.5 mg,
0.75 mmol CO2H), a solution of dendron in DMF (see Table 3), and
CHMC[34] (12 mgmLꢀ1, 200 mL, 5.66 mmol) were mixed and MeOH/Tx
(1:2) was added to adjust the reaction mixture to 1 mL (Table 3). The re-
action vessel was shaken in rotators for 16 h at RT. Then, the particles
were collected by using an external magnet field and washed several
times with NaOH (10 mm), Tx[25], and THF/Tx (2:1) solutions (1 mL
each).
ACHTUNGTRENNUNG
AHCTUNGTRENNUNG
0.03 ppm (s, 9H; CH3Si); 13C NMR (50.33 MHz, CDCl3, 258C): d=157.2
(COar), 157.0 (COar), 156.9 (C=O), 138.3 (Cq(ar)), 137.4 (Cq(ar)), 127.5
(CHar), 127.2 (CHar), 114.3 (CHar), 114.1 (CHar), 68.4 (CH2O), 67.7
(CH2O), 62.9 (CH2OCO), 52.0 (CH2N3), 42.1 (CqCar), 42.0 (CqCar), 40.9
(CH2NH), 34.45 (CH2Cq), 33.9 (CH2Cq), 30.1 (CH2), 29.3 (CH2), 26.6
(CH2), 25.9 (CH2), 23.8 (CH2), 23.3 (CH2), 17.8 (CH2Si), ꢀ1.4 ppm
(CH3Si); MS (MALDI): m/z calcd for C76H114N28O6Si+Na+: 1566.92
[M+Na]+; found: 1566.82.
Table 3. Grafting of dendrons 1–4 onto MNPs.
Compound 19: A mixture of nona-azo dendron 18 (400 mg, 0.26 mmol),
PPh3 (920 mg, 3.5 mmol), and H2O (140 mL, 7,78 mmol) in THF (5 mL)
was heated to 408C for 12 h. The solvent was removed under reduced
pressure. Et2O was added and the product was extracted with water. The
aqueous layer was washed several times with Et2O and evaporated under
reduced pressure to yield compound 19 as a yellow powder (320 mg,
Dendron Conc.
Weight (equiv)
[mg]
DMF
[mL]
MeOH/Tx (1:2)
[mmol]
[mL]
1
2
3
4
1
2
3
4
7.5
7.5
7.5
3
17.5 (10)
15 (10)
20 (10)
20.9 (4)
200
200
200
200
350
350
350
350
94%). 1H NMR (250 MHz, [D4]MeOH, 258C): d=7.23 (d, 3J
A
3
8 Hz, 6H; CHar), 7.02 (m, 2H; CHar), 6.80 (d, J
(H,H)=8 Hz, 6H; CHar),
3
6.67 (m, 2H; CHar), 4.11 (t, J
CH2O), 3.07 (m, 2H; CH2NH), 2.52 (m, 18H; CH2NH2), 1.9–1.7 (m, 8H;
CH2), 1.7–1.3 (m, 30H; CH2), 1.22 (m, 18H; CH2), 0.97 (t, 3J
(H,H)=
8 Hz, 2H; CH2Si), 0.04 ppm (s, 9H; CH3Si); 13C NMR (75.46 MHz,
[D4]MeOH, 258C): d=159.1 (COar), 158.2(C=O), 140.2 (Cq(ar)), 128.5
ACHTUNGTERN(NUNG H,H)=8 Hz, 2H; CH2OCO), 3.86 (m, 8H;
AHCTUNGTRENNUNG
General procedure for catalytic reactions and recovery of catalysts:
Grafted MNPs materials (0.05–5 mg), NaOH (168 mmol), boronic acid
arene (84.37 mmol), and aryl halide (56.25 mmol) were mixed in THF/Tx
(1:9, 1 mL). The mixture was stirred at 658C. Then, grafted MNPs were
separated from the mixture by attraction with an external magnet and
washed with THF/Tx (1:9, 2ꢂ500 mL). Then, the MNPs were added to a
freshly made reaction mixture.
AHCTUNGTRENNUNG
(CHar), 115,1 (CHar), 69.7 (CH2O), 63.5 (CH2OCO) 43.4 (CH2NH2), 43.0
(CqCar), 41.6 (CH2NH), 35.9 (CH2Cq), 30.9 (CH2CH2NH), 30.5
(CH2CH2O), 28.2 (CH2), 27.6 (CH2), 26.8 (CH2), 25.9 (CH2), 25.0 (CH2),
18.6 (CH2Si), ꢀ1.34 ppm (CH3Si); MS (MALDI): m/z calcd for
C76H132N10O6Si+H+: 1310.02 [M+H]+; found: 1309.98.
Compound 20:
4.29 mmol) in n-hexane was added to a Schlenk tube and evaporated
under reduced pressure. solution of paraformaldehyde (690 g,
A solution of 10% dicyclohexylphosphine (8.7 mL,
A
23.0 mmol) in MeOH/toluene (2:1, 10 mL) was added under an inert at-
mosphere and the reaction mixture was heated to 708C for 10 min. A so-
lution of compound 19 (250 mg, 0.19 mmol) in MeOH/toluene (2:1,
5 mL) was added and the mixture was stirred at 708C for 10 min and
then at RT for 12 h. The volume of the reaction mixture was reduced and
MeOH was added. The residue was isolated from the medium, washed
several times with MeOH, and dried under vacuum to yield compound
20 as a fine yellow powder (810 mg, 83%). 1H NMR (200 MHz, CDCl3,
258C): d=7.13 (m, 8H; CHar), 6.74 (m, 8H; CHar), 4.12 (m, 2H;
CH2OCO), 3.81 (m, 8H; CH2O), 3.19 (m, 2H; CH2NH), 2.67 (s, 36H;
NCH2P), 2.61 (m, 18H; CH2NCH2P), 1.7–1.0 (m, 454H;
CH(Cy)+CH2(Cy)+CH2), 0.01 ppm (s, 9H; CH3Si); 13C NMR (50.33 MHz,
CDCl3, 258C): d=156.7 (COar+C=O), 139.4 (Cq(ar)), 127.5 (CHar), 113,5
Acknowledgements
Financial support from the Universitꢀ Bordeaux 1, Centre National de la
Recherche Scientifique (CNRS), the Region Aquitaine, the Ministꢃre de
lꢄEnseignement Supꢀrieur et de la Recherche (DRA), and the Agence
Nationale de la Recherche (ANR-05-JCJC-0245) is gratefully acknowl-
edged.
[1] a) J. H. Clark, D. J. Macquarrie, Handbook of Green Chemistry and
Technology, Blackwell: Oxford, 2002; b) G. Rothenberg, Catalysis,
Concepts and Green Applications, VCH, Weinheim, 2008.
Chem. Eur. J. 2012, 18, 3305 – 3315
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3313

D. Rosario-Amorin, S. Nlate, K. Heuzꢀ et al.
[2] a) S. A. Majetich, T. Wen, R. A. Booth, ACSNano 2011, 5, 6081–
6084; b) A. Schꢅtz, O. Reiser, W. J. Stark, Chem. Eur. J. 2010, 16,
8950–8967; c) C. W. Lim, I. S. Lee, Nano Today 2010, 5, 412–434;
d) V. Polshettiwar, R. Luque, A. Fihri, H. Zhu, M. Bouhrara, J.-M.
Basset, Chem. Rev. 2011, 111, 3036–3075.
[3] a) A. Corma, H. Garcia, Adv. Synth. Catal. 2006, 348, 1391–1412;
b) F. Cozzi, Adv. Synth. Catal. 2006, 348, 1367–1390; c) B. M. L.
Dioos, I. F. J. Vankelecom, P. A. Jacobs, Adv. Synth. Catal. 2006, 348,
1413–1446; d) D. E. Bergbreiter, S. D. Shung, Adv. Synth. Catal.
2006, 348, 1352–1366; e) V. Polshettiwar, A. Molnꢆr, Tetrahedron
2007, 63, 6949; f) N. Madhavan, C. W. Jones, M. Weck, Acc. Chem.
Res. 2008, 41, 1153–1165; g) S. Ikegami, H. Hamamoto, Chem. Rev.
2009, 109, 583–593.
[4] a) J. Liu, X. Peng, W. Sun, Y. Zhao, C. Xia, Org. Lett. 2008, 10,
3933–3936; b) M. S. Kwon, I. S. Park, J. S. Jang, J. S. Lee, J. Park,
Org. Lett. 2007, 9, 3417–3419; c) H. Yoon, S. Ko, J. Jang, Chem.
Commun. 2007, 1468–1470; d) K. Mori, S. Kanai, T. Hara, T. Mizu-
gaki, K. Ebitani, K. Jitsukawa, K. Kaneda, Chem. Mater. 2007, 19,
1249–1256; e) X. Teng, D. Black, N. J. Watkins, Y. Gao, H. Yang,
Nano Lett. 2003, 3, 261–264; f) M. Shokouhimehr, Y. Piao, J. Kim,
Y. Jang, T. Hyeon, Angew. Chem. 2007, 119, 7169–7173; Angew.
Chem. Int. Ed. 2007, 46, 7039–7043; g) T. Zeng, W.-W. Chen, C. M.
Cirtiu, A. Moores, G. Song, C.-J. Li, Green Chem. 2010, 12, 570–
573; h) H. Firouzabadi, N. Iranpoor, M. Gholinejad, J. Hoseini, Adv.
Synth. Catal. 2011, 353, 125–132.
[5] a) S. Luo, X. Zheng, H. Xu, X. Mi, L. Zhang, J-P. Cheng, Adv.
Synth. Catal. 2007, 349, 2431–2434; b) R. Abu-Reziq, D. Wang, M.
Post, H. Alper, Adv. Synth. Catal. 2007, 349, 2145–2150; c) M. Ka-
wamura, K. Sato, Chem. Commun. 2006, 4718–4719; d) S. Ding, Y.
Xing, M. Radosz, Y. Shen, Macromolecules 2006, 39, 6399–6405;
e) N. T. S. Phan, C. W. Jones, J. Mol. Catal. A 2006, 253, 123–131;
f) P. D. Stevens, G. Li, J. Fan, M. Yen, Y. Gao, Chem. Commun.
2005, 4435–4437; g) R. De Palma, S. Peeters, M. J. Van Bael, H.
Van den Rul, K. Bonroy, W. Laureyn, J. Mullens, G. Borghs, G.
Maes, Chem. Mater. 2007, 19, 1821–1831; h) S. Luo, X. Zheng, J.-P.
Cheng, Chem. Commun. 2008, 5719–5721.
[6] a) L. M. Rossi, L. L. R. Vono, F. P. Silva, P. K. Kiyohara, E. L.
Duarte, J. R. Matos, Appl. Catal. A 2007, 330, 139–144; b) T. J.
Yoon, W. Lee, Y.-S. Oh, J.-K. Lee, New J. Chem. 2003, 27, 227–229;
c) T. J. Yoon, J. I. Kim, J-K. Lee, Inorg. Chim. Acta 2003, 345, 228–
234.
[7] a) A. Hu, G. T. Yee, W. Lin, J. Am. Chem. Soc. 2005, 127, 12486–
12487; b) G. Chouhan, D. Wang, H. Alper, Chem. Commun. 2007,
4809–4811; c) Y. Zheng, C. Duanmu, Y. Gao, Org. Lett. 2006, 8,
3215–3217; d) Z. Yinghuai, S. C. Peng, A. Emi, S. Zhenshun, Mona-
lisa, R. A. Kemp, Adv. Synth. Catal. 2007, 349, 1917–1922.
[8] a) C. R. Vestal, J. Zhang, J. Am. Chem. Soc. 2002, 124, 14312–
14313; b) S. Yu, M. Chow, J. Mater. Chem. 2004, 14, 2781–2786;
c) C. Mangeney, M. Fertani, S. Bousalem, M. Zhicai, S. Ammar, F.
Herbst, P. Beaunier, A. Elaissari, M. M. Chehimi, Langmuir 2007,
23, 10940–10949; d) K. M. Ho, P. Li, Langmuir 2008, 24, 1801–
1807; e) A. Schaetz, M. Zeltner, T. D. Michl, M. Rossier, R. Fuhrer,
W. J. Stark, Chem. Eur. J. 2011, 17, 10566–10573; f) F. Caruso, M.
Spasova, A. Susha, M. Giersig, R. A. Caruso, Chem. Mater. 2001, 13,
109–116.
Hudson, G. Song, A. R. Moores, C.-J. Li, Org. Lett. 2011, 13, 442–
445.
[11] a) W. Wang, Y. Xu, D. I. C. Wang, Z. Li, J. Am. Chem. Soc. 2009,
131, 12892–12893; b) X. Wang, P. Dou, P. Zhao, C. Zhao, Y. Ding,
P. Xu, ChemSusChem 2009, 2, 947–950; c) Y. Z. Chen, C. T. Yang,
C. B. Ching, R. Xu, Langmuir 2008, 24, 887–8884.
[12] a) D. A. Tomalia, H. Baker, J. Dewald, M. Hall, G. Kallos, S.
Martin, J. Roeck, J. Ryder, P. Smith, Macromolecules 1986, 19,
2466–2468; b) R. A. Kleij, P. W. N. M. van Leeuwen, Eur. Pat.
0456317, 1991; <lit c>H. Brunner, J. Fꢈrst, J. Ziegler, J. Organo-
met. Chem. 1993, 454, 87–94; d) A. W. Knapen, J. C. deWilde,
P. W. N. M. van Leeuwen, P. Wijkens, D. Grove, G. van Koten,
Nature 1994, 372, 659–663; e) A. W. Bosman, H. M. Janssen, E. W.
Meijer, Chem. Rev. 1999, 99, 1665–1688; f) G. R. Newkome, E. He,
C. N. Moorefield, Chem. Rev. 1999, 99, 1689–1746; g) G. E. Ooster-
om, J. N. H. Reek, P. C. J. Kamer, P. W. N. M. Leeuwen, Angew.
Chem. 2001, 113, 1878–1901; Angew. Chem. Int. Ed. 2001, 40, 1828–
1849; h) G. R. Newkome, C. N. Moorefield, F. Vçgtle, Dendrimers
and Dendrons, Concepts, Syntheses and Applications, Wiley-VCH,
Weinheim, 2002.
[13] For the stabilization of particles, see: a) M. Kim, Y. Chen, Y. Liu, X.
Peng, Adv. Mater. 2005, 17, 1429–1432; b) B. L. Frankamp, A. K.
Boal, M. T. Tuominen, V. M. Rotello, J. Am. Chem. Soc. 2005, 127,
9731–9735; c) E. Strable, J. W. M. Bulte, B. Moskowitz, K. Viveka-
nandan, M. Allen, T. Douglas, Chem. Mater. 2001, 13, 2201–2209.
[14] For biological applications, see: a) C. Duanmu, I. Saha, Y. Zhang,
B. M. Goodson, Y. Gao, Chem. Mater. 2006, 18, 5973–5981; B.-F.
Pan, F. Gao, L.-M. Ao, J. Magn. Magn. Mater. 2005, 293, 252–258;
b) F. Gao, B.-F. Pan, W.-M. Zheng, L.-M. Ao, H.-C. Gu, J. Magn.
Magn. Mater. 2005, 293, 48–54; c) B.-F. Pan, F. Gao, H.-C. Gu, J.
Colloid Interface Sci. 2005, 284, 1–6; B. Basly, D. F.-F., P. Perriat, C.
Billotey, J. Taleb, G. Pourroy, S. Begin-Colin, Chem. Commun. 2010,
46, 985–987.
[15] For catalysis applications, see: a) R. Abu-Reziq, H. Alper, D. Wang,
M. L. Post, J. Am. Chem. Soc. 2006, 128, 5279–5282; b) see also ref-
erence [14a].
[16] For a general review on dendrimers as stabilizing agents for inorgan-
ic nanoparticles, see: L. M. Bronstein, Z. B. Shifrina, Chem. Rev.
2011, 111, 5301–5344.
[17] K. Heuzꢀ, D. Rosario-Amorin, S. Nlate, M. Gaboyard, A. Bouter,
R. Clꢀrac, New J. Chem. 2008, 32, 383–387.
[18] Commercially available core–shell g-Fe2O3/polymer 300 nm super-
paramagnetic nanoparticles (Carboxyl-Adembeads 300 nm, Adem-
tech, France, COOH: 300 mmolgꢀ1 of particles).
[19] D. Rosario-Amorin, X. Wang, M. Gaboyard, R. Clꢀrac, S. Nlate, K.
Heuzꢀ, Chem. Eur. J. 2009, 15, 12636–12643.
[20] D. Rosario-Amorin, M. Gaboyard, R. Clꢀrac, S. Nlate, K. Heuzꢀ,
Dalton Trans. 2011, 40, 44–46.
[21] a) M. T. Reetz, G. Lohmer, R. Schwickardi, Angew. Chem. 1997,
109, 1559; Angew. Chem. Int. Ed. Engl. 1997, 36, 1526; b) K. Heuzꢀ,
D. Mꢀry, D. Gauss, D. Astruc, Chem. Commun. 2003, 2274; c) K.
Heuzꢀ, D. Mꢀry, D. Gauss, J.-C. Blais, D. Astruc, Chem. Eur. J. 2004,
10, 3936; d) J. Lemo, K. Heuzꢀ D. Astruc, Inorg. Chim. Acta 2006,
359, 4909–4911;, D. Astruc, Org. Lett. 2005, 7, 2253; e) J. Lemo, K.
Heuzꢀ, D. Astruc, J. Am. Chem. Soc. 1999, 121, 2929–2930.
[22] Tri-iodo compound 10 was synthesized according to the procedure:
V. Sartor, L. Djakovitch, J.-L Fillaut, F. Moulines, F. Neveu, V. Mar-
vaud, J. Guittard, J.-C Blais, D. Astruc, J. Am. Chem. Soc. 1999, 121,
2929-2930.
[23] Teoc-protected 1-iodoaminohexane was obtained from a Teoc-pro-
tected aminoalcohol, which was prepared from the commercially
available 6-aminohexanol according to a procedure reported in our
previous article, see Ref. [19].
[24] a) T. C. Granade, S. Workman, S. K. Wells, A. N. Holder, S. M.
Owen, C.-P. Pau, Clin. Vaccine Immunol. 2010, 17, 1034–1039; b) H.
Jans, K. Jans, T. Stakenborg, B. Van de Broek, L. Lagae, G. Maes, G.
Borghs, Nanotechnology 2010, 21, 345102; c) L.-G. Zamfir, I. Geana,
S. Bourigua, L. Rotariu, C. Bala, A. Errachid, N. Jaffrezic-Renault,
Sens. Actuators B 2011, 159, 178–184.
[9] A. P. Philipse, M. P. B. van Bruggen, C. Pathmamanoharan, Lang-
muir 1994, 10, 92–99.
[10] a) P. D. Stevens, J. Fan, H. M. R. Gardimalla, M. Yen, Y. Gao, Org.
Lett. 2005, 7, 2085–2088; b) C. S. Gill, B. A. Price, C. W. Jones, J.
Catal. 2007, 251, 145–152; c) C. ꢇ. Dꢆlaigh, S. A. Corr, Y. Gunꢄko,
S. J. Connon, Angew. Chem. 2007, 119, 4407–4410; Angew. Chem.
Int. Ed. 2007, 46, 4329–4332; d) A. Schꢅtz, M. Hager, O. Reiser,
Adv. Funct. Mater. 2009, 19, 2109–2115; e) S. Shylesh, J. Scheizer, S.
Demeshko, V. Schꢈnemann, S. Ernst, W. R. Thiel, Adv. Synth. Catal.
2009, 351, 1789–1795; f) M.-J. Jin, D.-H. Lee, Angew. Chem. 2009,
121, 1–1; Angew. Chem. Int. Ed. 2009, 48, 1–5; g) C. Pereira, A. M.
Pereira, P. Quaresma, P. B. Tavares, E. Peirera, J. P. Araꢉjo, C.
Freire, Dalton Trans. 2010, 39, 2842–2854; h) T. Zeng, L. Yang, R.
3314
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ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Chem. Eur. J. 2012, 18, 3305 – 3315

Metallodendritic Core–Shell g-Fe2O3 Nanoparticles
FULL PAPER
[25] Tx: triton X405 water solution (0.21%) obtained from triton X405
(70%), purchased from Aldrich.
[30] a) P. W. N. M. van Leeuwen, Appl. Catal. A 2001, 212, 61–81; b) P.
Garrou, Chem. Rev. 1985, 85, 171–185.
[26] Free, accessible carboxylic acid functions were in the range 300–355
mmolgꢀ1 of particles. This value was determined by conductimetric
measurements.
[27] ICP-MS analysis of grafted MNPs showed 1.81% [Pd] for 4 equiva-
lents of compound 4 during the grafting reaction.
[28] The magnet used was based on a neodymium-iron-boron alloy (Nd-
Fe-B) that quickly draws superparamagnetic particles away from the
solution.
[29] See the general procedure with: MNP-1, MNP-2, MNP-3, or MNP-
4 (5 mg, 4.8 mol% [Pd]), NaOH (168 mmol), phenylboronic acid
(84.37 mmol), and iodobenzene (56.25 mmol) were mixed in Tx/
THF (9:1, 1 mL). The mixture was stirred at 658C for 1 h. Then,
grafted MNPs were separated by a simple external magnet and were
washed with Tx/THF (9:1, 2ꢂ500 mL). The particles were washed
twice with Tx/THF (9:1) between each run.
[31] a) K. Heuzꢀ, D. Mꢀry, D. Gauss, D. Astruc, Chem. Commun. 2003,
2274–2275; b) K. Heuzꢀ, D. Mꢀry, D. Gauss, D. Blais J. C. Astruc,
Chem. Eur. J. 2004, 10, 3939–3944; c) J. Lemo, K. Heuzꢀ D. Astruc,
Inorg. Chim. Acta 2006, 359, 4909–4911; d) D. E. Bergbreiter, J.
Frels, K. Heuzꢀ, Reac. & Func. Polym. 2001, 49, 249–254; Func.
Polym. 2001, 49, 249–254.
[32] Teoc-protected 6-iodo-aminohexane was synthesized in two steps
from the commercially available 6-aminohexanol; see Ref. [19].
[33] A suspension of Carboxyl-Adembeads 300 nm nanoparticles 1 wt%
MeOH/Tx (1:2).
[34] A solution of carbodiimide CHMC 12 mgmLꢀ1 in MeOH/Tx (1:2).
Received: October 6, 2011
Published online: February 6, 2012
Chem. Eur. J. 2012, 18, 3305 – 3315
ꢁ 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.chemeurj.org
3315