Synthesis of calixarene-capped carbosilane dendrimers

Article abstract of DOI:10.1021/jo802714q

A new class of polycalix[4]arene hosts has been constructed based on a carbosilane dendrimer architecture, in which each dendritic branch terminates with a calix[4]arene entity. This study reports the synthesis and characterization of the zeroth generatio

Full text of DOI:10.1021/jo802714q

Synthesis of Calixarene-Capped Carbosilane Dendrimers
Joseph B. Lambert,* Seung-Hyun Kang, Kuangbiao Ma, Chunqing Liu, and
Allison G. Condie
Department of Chemistry, Northwestern UniVersity, EVanston, Illinois 60208
jlambert@northwestern.edu
ReceiVed December 12, 2008
A new class of polycalix[4]arene hosts has been constructed based on a carbosilane dendrimer architecture,
in which each dendritic branch terminates with a calix[4]arene entity. This study reports the synthesis
and characterization of the zeroth generation example with four calix[4]arenes and of the first generation
example with 12 calix[4]arenes.
Introduction
workers11 demonstrated that a branched architecture improves
and intensifies the ability of calixarenes to bind with metal
cations, possibly by creating new or multiple binding sites.
Dendrimers have been widely explored for about two decades
for a variety of very general applications.12 Crooks,13 Tomalia,14
and their co-workers have used dendrimers with a number of
terminal groups to bind copper(II).
Calixarenes have been an active subject of research since their
development by Gutsche.1-6 Readily accessible synthetically,
they can serve as hosts for a wide variety of inorganic cations
and organic molecules. As metal binders,7 they have found uses
in catalysis,8 separations,9 and chemosensing.10 Shinkai and co-
To date, there have been limited synthetic approaches to
calixarenes with a branched architecture. The largest branched
systems contain only five calixarene units: a central calixarene
attached to four terminal calixarenes.11,15,16 Branching occurs
only around the core calixarene in these pentacalixarenes,
so they are zeroth generation dendrimers. Although Lhotak
and Shinkai11 demonstrated that nondendritic dicalixarenes
bind with up to two Li+ ions, the equilibria of their tri- and
(1) Gutsche, D. C. Calixarenes: An Introduction; Royal Society of Chemistry:
Cambridge, UK, 2008.
(2) Takeshita, M.; Shinkai, S. Bull. Soc. Chem. Jpn. 1995, 68, 1088–1097.
(3) Bo¨hmer, V. Angew. Chem., Int. Ed. Engl. 1995, 34, 713–745.
(4) Diamond, D.; McKervey, M. A. Chem. Soc. ReV. 1996, 25, 15–24.
(5) Wieser, C.; Dieleman, C. B.; Matt, D. Coord. Chem. ReV. 1997, 165,
93–161.
(6) Gutsche, D. C. Calixarenes ReVisited; Royal Society of Chemistry:
Cambridge, UK, 1998.
(7) Arnaud-Neu, F.; Collins, E. M.; Deasy, M.; Ferguson, G.; Harris, S. J.;
Kaitner, B.; Lough, A. J.; McKervey, M. A.; Marques, E.; Ruhl, B. L.; Schwing-
Weill, M. J.; Seward, E. M. J. Am. Chem. Soc. 1989, 111, 8681–8691.
(8) (a) Molenveld, P.; Engbersen, J. F. J.; Kooijman, H.; Spek, A. L.;
Reinhoudt, D. N. J. Am. Chem. Soc. 1998, 120, 6726–6737. (b) Molenveld, P.;
Engbersen, J. G. J.; Reinhoudt, D. N. J. Org. Chem. 1999, 64, 6337–6341. (c)
Cacciapaglia, R.; Casnati, M.; Mandolini, L.; Reinhoudt, D. N.; Salvio, R.; Sartori,
A.; Ungaro, R. J. Org. Chem. 2005, 70, 624–630.
(9) Matthews, S. E.; Parzuchowski, P.; Bo¨hmer, V.; Garcia-Carrera, A.;
Dozol, J.-F.; Gru¨ttner, C. Chem. Commun. 2001, 417–418.
(10) (a) Kubo, Y.; Meade, S.; Nakamura, M.; Tokita, S. J. Chem. Soc., Chem.
Commun 1994, 172, 5–1726. (b) Liu, Y.; Wang, H.; Wang, L.-H.; Li, Z.; Zhang,
H. Y.; Zhang, Q. Tetrahedron 2003, 59, 7967–7972. (c) Ikeda, A.; Shinkai, S.
Chem. ReV. 1997, 97, 1713–1734.
(11) Lhotak, P.; Shinkai, S. Tetrahedron 1995, 51, 7681–7696.
(12) (a) Newkome, G. R.; Yao, Z.-Q.; Baker, G. R.; Gupta, V. K. J. Org.
Chem. 1985, 50, 2003–2004. (b) Tomalia, D. A.; Naylor, A. M.; Goddard, W. A.
Angew. Chem., Int. Ed. Engl. 1990, 29, 138–175. (c) Wooley, K. L.; Hawker,
C. J.; Fre´chet, J. M. J. Am. Chem. Soc. 1991, 113, 4252–4261. (d) Tomalia,
D. A.; Durst, H. D. Top. Curr. Chem. 1993, 165, 193–313.
(13) (a) Crooks, R. M.; Lemon, B. I.; Sun, L.; Yeung, L. K.; Zhao, M. Top.
Curr. Chem. 2001, 212, 81–135. (b) Crooks, R. M.; Zhao, M.; Sun, L.; Chechik,
V.; Yeung, L. K. Acc. Chem. Res. 2001, 34, 181–190.
(14) Balogh, L.; Tomalia, D. A. J. Am. Chem. Soc. 1998, 120, 7355–7356.
(15) Radzevich, K.; Fischer, M.; Schmidt, M.; Bo¨hmer, V. Org. Biomol.
Chem. 2005, 3, 3916–3925.
(16) Wang, J.; Gutsche, C. J. Org. Chem. 2002, 67, 4423–4429.
10.1021/jo802714q CCC: $40.75
Published on Web 02/17/2009
2009 American Chemical Society
J. Org. Chem. 2009, 74, 2527–2532 2527

Lambert et al.
SCHEME 1
pentacalixarenes were characterized only qualitatively. Wang
and Gutsche demonstrated that a tricalixarene exhibited
cooperative binding with C60.16 Thus multiple calixarene
units can accomplish binding not possible with single units.
The only truly dendritic calixarene reported to date, without
complexation studies, is a heptacalixarene, in which a core
calix[4]arene is attached to two calix[4]arene units.17 These
units serve as 2-fold branch points that lead to a total of
four peripheral calix[4]arenes. Polymeric dendrimers also
have been reported.18
et al. concluded that Cu(II) binds with terminal amines.
Stoichiometry indicated that each copper ion is bound to two
terminal amines (thus the second generation binds with 4
copper ions, the fourth with 16, and the sixth with 64). Since
PAMAM only doubles the number of binding sites with each
generation, very high generations were required before a large
number of ions could be bound. In these systems peripheral
units seem to be most effective in binding.
It was the purpose of the current study to find an efficient
route to calixarene dendrimers as possible substrates to exhibit
cooperative and enhanced binding. The dendritic architecture
we envisioned is quite different from those of Shinkai,11
Bo¨hmer,15 Gutsche,16 or Beer.17 The systems of these authors
used calixarenes as the core, the branching points (in the single
case of Beer’s work), and the termini. Interior calixarenes might
be less accessible and hence less available for binding. The
systems of these authors would be difficult to build up to higher
level dendrimers. Our calixarene units are designed to be located
only at the dendritic termini and hence should be fully accessible
Tomalia, Crooks, and their co-workers19 used PAMAM
[poly(amidoamine)] dendrimers to bind Cu(II). Although
these dendrimers have potential internal binding sites, Crooks
(17) Szemes, G.; Drew, M. G. B.; Beer, P. D. Chem. Commun. 2002, 1228–
1229.
(18) Yamagishi, T.-A.; Moriyama, E.; Konishi, G.-i.; Nakamoto, Y. Mac-
romol 2005, 38, 6871–6875.
(19) (a) Tomalia, D. A.; Baker, H.; Dewald, J.; Hall, M.; Kallos, G.; Martin,
S.; Roeck, J.; Ryder, J.; Smith, P. Polymer J. (Tokyo) 1985, 17, 117–132. (b)
Balogh, L.; Tomalia, D. A. J. Am. Chem. Soc. 1998, 120, 7355–7356. (c) Zhao,
M.; Sun, L.; Crooks, R. M. J. Am. Chem. Soc. 1998, 120, 4877–4878.
2528 J. Org. Chem. Vol. 74, No. 6, 2009

Synthesis of Calixarene-Capped Carbosilane Dendrimers
SCHEME 2
to binding. By using a 3-fold branching carbosilane structure20
(the sole existing dendritic calixarene17 contains 2-fold branch-
ing) we can assemble higher level dendrimers quickly and
efficiently. Moreover, the carbosilane interior does not allow
binding, in contrast to the linkages of the PAMAM dendrimers.
We report herein the successful synthesis and characterization
of zeroth and first generation dendrimers that respectively
contain 4 and 12 surface calixarene units. These dendrimers
provide multiple surface calixarenes capable of potential
cooperative binding without competition from interior binding
sites.
The final step f involves hydrosilylation with TMDS of the
functionalized monoallyl compound 5 to form the calix[4]arene
attached to the linker (6). This synthesis may be modified to
accommodate many calixarene types.
Reaction of tetrachlorosilane with 4 equiv of allylmagnesium
bromide yielded the zeroth generation carbosilane (tetraallyl-
silane, G0) (Scheme 2). Hydrosilylation of G0 with 4 mol of
the linker-attached calix[4]arene 6 produced the zeroth genera-
tion carbosilane attached to four calix[4]arene units (Scheme
2), which we designate G0-CX4, for dendritic generation zero
with four calix[4]arenes.
Hydrosilylation of tetraallylsilane (G0) with trichlorosilane
gave the dodecachloro first generation dendrimer (G1-Cl in
Scheme 3), which on reaction with 12 equiv of allylmagnesium
bromide gave the first generation dodecaallyl carbosilane (G1).
Hydrosilylation of G1 with 12 mol of the linker-attached
calix[4]arene 6 produced the first generation carbosilane attached
to 12 calixarene units (Scheme 3), which we designate G1-
CX12, for dendritic generation one with 12 calix[4]arenes.
This approach is easily adapted for higher generations. To
achieve a second generation dendrimer (with 36 calixarene
units), the compound G1 in Scheme 3 would be hydrosilylated
12 times with HSiCl3, and the resulting polychloride would be
reacted with allylmagnesium bromide to give a 36-tipped
polyallyl dendrimer. This second generation product could either
be ligated with 36 calixarenes to complete the second generation
synthesis or hydrosilylated 36 times with HSiCl3 to begin the
third generation synthesis.
Results and Discussion
Synthesis. The scheme in the abstract presents the overall
strategy of this study. A carbosilane dendrimer of the appropriate
generation is prepared with multiple surface functionalities
capable of being tied to a calix[4]arene unit, which can bind
with a metal cation. A convergent synthesis (eq 1) optimizes
the yield, as the calixarene and carbosilane pieces are assembled
separately and subsequently are tied together. This approach
involves synthesis of two major components, one of which
contains a single calixarene (calix-CH2CHdCH2), and the other
is the allyl-tipped carbosilane dendrimer [carbosilane(CH2CHd
CH2)n]. These components then are brought together in a ligation
step (eq 1), whereby n calixarenes are attached to the n chains
of the dendrimer. We used double hydrosilylation for the ligation
process, in which 1,1,3,3-tetramethyldisiloxane (TMDS) is the
ligating element.
Syntheses were optimized by identification of the byproducts
and appropriate adjustment of conditions. In the conversion of
the allyl compound 5 to the first hydrosilylation product 6
(Scheme 1), byproducts included double bond migration,
hydrogenation, hydrolysis, and reaction with the solvent tet-
ncalix-CH2CH)CH2 + nH-SiMe2OSiMe2Si-H +
carbosilane(CH2CH)CH2)n f calix-dendrimers (1)
Scheme 1 outlines the synthesis of the calix[4]arene portion
5, based largely on the work of Gutsche and co-workers.21,22
J. Org. Chem. Vol. 74, No. 6, 2009 2529

Lambert et al.
SCHEME 3
rahydrofuran (Scheme 4). Other byproducts included the result
of reaction of only three of the four allyl groups of G0 in
Scheme 2. All these byproducts could be recognized in the NMR
spectra. The products of hydrolysis and hydrogenation could
be reduced by using strictly anhydrous conditions. Reaction with
solvent was reduced by using mixed dimethylformamide and
tetrahydrofuran. Column chromatography was effective in
purifying the desired product from the remaining byproducts
to give a 61% isolated yield of G0-CX4 and a 42% isolated
yield of G1-CX12.
SCHEME 4
Characterization. Compounds 1-5 were known from the
work of Gutsche and co-workers.21,22 The dendrimers G0-CX4
and G1-CX12 were characterized by NMR spectroscopy,
electrospray mass spectrometry, and elemental analysis (see the
Experimental Section and the Supporting Information). All 236
protons in the first generation dendrimer and 732 protons in
the second generation dendrimer were accounted for. The
respective expected molecular weights of 3858 and 5888.5 were
corroborated, and the elemental analyses were very accurate.
Thus the molecules are well characterized in bulk.
The conformations in solution of both G0-CX4 and G1-CX12
could be determined by examination of the Overhauser cross
peaks in the NOESY spectra. The methylene group labeled R
in the illustrated numbering scheme below showed a cross peak
with the 4 and 6 protons but not with any of the protons on the
other aromatic rings. The 2 and 8 methylene protons directed
2530 J. Org. Chem. Vol. 74, No. 6, 2009

Synthesis of Calixarene-Capped Carbosilane Dendrimers
downward (in the same direction as the R methylene group)
exhibited cross peaks with the 4, 6, 10, and 24 aromatic protons,
indicating that all three phenyl rings point in the same direction.
The 14 and 20 methylene protons directed downward exhibited
cross peaks with the 12 and 22 aromatic protons, but the 14
and 20 methylene protons directed upward had cross peaks with
the 16 and 18 aromatic protons. These spectral observations
are consistent with a partial cone (paco) conformation with the
middle benzoyloxy-substituted aromatic ring directed to the
opposite side of the cone from the other three aromatic rings.
This assignment is based on the assumption that the downward-
directed methylene protons are at lower frequency because of
shielding by the faces of the adjacent aromatic rings.23
core. Each additional generation would require two more
synthetic steps.
The resulting dendrimers permit maximum accumulation of
calixarene units because the interior is composed of the relatively
unencumbered carboxilane units (previous branched and den-
dritic calixarenes used calixarenes as core and branching points
as well as termini). Moreover, the interior carbosilane dendritic
structure is not capable of binding, so that the terminal
calixarenes are the only potential binding points in these
molecules. The next stage of this program involves selection
of the substituents on the calix[4]arene host 5 for optimal
binding with metal cations.
Experimental Section
4-tert-Butylcalix[4]arene (1) was synthesized on a ca. 50 g scale
in 49% yield by the method of Gutsche et al.21
25,26,27,28-Tetrahydroxylcalix[4]arene (2) was synthesized on
a ca. 15 g scale in 75% yield by the method of Gutsche and Lin.22
25,26,27-Tris(benzoyloxy)-28-hydroxycalix[4]arene (3) was
synthesized on a ca. 20 g scale in 78% yield by the method of
Gutsche and Lin.22
25-(Allyloxy)-26,27,28-tris(benzoyloxy)calix[4]arene (4) was
synthesized on a ca. 6 g scale in 42% yield by the method of
Gutsche and Lin.22
5-Allyl-25-hydroxy-26,27,28-tris(benzoyloxy)calix[4]arene (5)
was synthesized on a ca. 6 g scale in 77% yield by the method of
Gutsche and Lin.22
5-[3-(1,1,3,3-Tetramethyldisiloxyl)propyl]-25-hydroxy-26,27,28-
tris(benzoyloxy)calix[4]arene (6). Compound 5 (2.11 g, 0.0027
mol), dried THF (20 mL), TMDS (3.62 g, 0.0269 mol), and
Karstedt’s catalyst25 (100 µL, 2.1-2.4% Pt in xylene) were placed
in a 250-mL, two-necked, round-bottomed flask equipped with a
condenser and a magnetic stirrer under N2 atmosphere. The mixture
was stirred at room temperature for 0.5 h and then warmed to 50
°C for 24 h. The solvent and excess TMDS were removed under
vacuum. The residue was dried under the vacuum overnight to give
2.01 g (82%) of 6: 1H NMR (CDCl3, 500 MHz) δ 8.07 (d, J ) 7.7
Hz, 4H, H30,34,36,40), 7.74 (t, J ) 7.3 Hz, 2H, H32,38), 7.56-7.52 (m,
5H, H31,33,37,39,44), 7.28-7.22 (m, 4H, H42,43,45,46), 7.03 (d, J ) 6.6
Hz, 2H, H10,24), 6.87 (d, J ) 6.6 Hz, 2H, H16,18), 6.81 (s, 2H, H4,6),
6.70 (t, J ) 7.7 Hz, 1H, H17), 6.60-6.58 (m, 4H, H11,12,22,23) 5.18
(s, 1H, OH), 4.68 (br s, 1H, SiH), 3.86 (d, J ) 15.1 Hz, 2H, H2,8
up), 3.82 (d, J ) 15.1 Hz, 2H, H14,20 up), 3.70 (d, J ) 15.1 Hz, 2H,
H14,20 down), 3.50 (d, J ) 15.1 Hz, 2H, H2,8 down), 2.42 (t, J ) 7.4
Hz, 2H, ArCH2CH2), 1.57-1.53 (m, 2H, ArCH2CH2), 0.53 (t, J )
7.5 Hz, 2H, CH2Si), 0.18-0.04 (m, 12H, SiCH3); 13C NMR (CDCl3)
δ 0.4, 1.7, 18.3, 25.9, 33.2, 37.3, 38.9, 125.3, 126.2, 127.7, 128.0,
128.3, 128.9, 129.1, 129.4, 129.7, 130.5, 131.0, 131.6, 133.0, 133.0,
133.13, 133.4, 133.7, 133.9, 133.9, 147.0, 148.5, 151.0, 164.1,
164.5; 29Si NMR (CDCl3) δ 7.34, -11.65. Anal. Calcd. (found)
for C56H54O8Si2: C, 73.82 (73.84); H, 5.97 (5.85).
Summary and Conclusions
We have prepared a new architecture of relatively im-
mobilized calixarenes by attaching calix[4]arenes to dendritic
carbosilanes. The largest previous branched system contained
five calixarenes.11,15,16 The only reported calixarene-terminated
dendrimer is a heptacalixarene,17 but various other end-group
hosts have been examined.24 The new family of hosts was
prepared by ligating a polyallyl carbosilane with independently
synthesized allyl-substituted calix[4]arene (Schemes 2 and 3).
The ligating agent was 1,1,3,3-tetramethyldisiloxane, containing
two Si-H groups. One Si-H hydrosilylates the allyl group on
the derivatized calix[4]arene 5 and the other Si-H hydrosilylates
the allyl groups on the polylallyl carbosilane (G0 or G1). The
zeroth order tetrabranched G0-CX4, prepared in two steps,
contains four calix[4]arene units arranged via carbosilane linkers
to a silicon core. The first generation dendritic G1-CX12,
prepared in four steps, contains 12 calix[4]arene units connected
via a 3-fold branching point to the 4-fold-substituted silicon
Tetraallylsilane (G0) was synthesized on a ca. 25 g scale in
93% yield by the method of van der Made and van Leeuwen.19
First Generation Dodecaallyl Carbosilane (G1). Tetraallylsi-
lane was hydrosilyated with HSiCl3, and the product was allowed
to react with 12 equiv of allylmagnesium bromide according to
the method of van der Made and van Leeuwen19 to produce G1 on
a scale of ca. 20 g in 90% yield: 29Si NMR (CDCl3) 0.66, -1.05.
Anal. Calcd (found) for C48H84Si5: C, 71.92 (72.09); H, 10.56
(10.65).
(20) van der Made, A. W.; van Leeuwen, P. W. N. M. J. J. Chem. Soc.,
Chem. Commun. 1992, 1400–1401.
(21) Gutsche, C. D.; Igbal, M.; Stewart, D. J. Org. Chem. 1986, 51, 742–
745.
(22) Gutsche, C. D.; Lin, L. G. Tetrahedron 1986, 42, 1633–1640.
(23) Arduini, A.; Pochini, A.; Reverberi, S.; Ungaro, R. J. Chem. Soc., Chem.
Commun. 1984, 981–982.
Dendritic Zeroth Generation Tetracalix[4]arene-End-Capped
Carbosilane (G0-CX4). Compound 6 (1.80 g, 0.0020 mol), dried
THF (30 mL), tetraallylsilane (G0, 0.04 g, 0.32 mmol), and
(24) (a) Buschbeck, R.; Lang, H.; Agarwal, S.; Saini, V. K.; Gupta, V. K.
Synthesis 2004, 1243–1248. (b) Matsuoka, K.; Saito, Y.; Terumura, D.; Kuzuhara,
H. Kobunshi Ronbunshu 2000, 57, 691–695; Chem. Abstr. 2000, 134, 57049.
(25) (a) Karstedt, B. D., U.S. Patent No. 3,775,453, 1973. (b) Karstedt,
B. D., U.S. Patent No. 3,814,593, 1974. (c) Hitchcock, P. B.; Lappert, M. F.;
Warhurst, N. J. W. Angew. Chem., Int. Ed. Engl. 1991, 30, 438–440.
J. Org. Chem. Vol. 74, No. 6, 2009 2531

Lambert et al.
Karstedt’s catalyst25 (20 µL, 2.1-2.4% Pt in xylene) were placed
in a 50-mL, two-necked, round-bottomed flask equipped with a
condenser and a magnetic stirrer under N2 atmosphere. The mixture
was stirred at room temperature for 15 min and then at 45 °C for
3 days. The flask was cooled, and the solvent was removed under
vacuum to produce a light yellow solid. The mixture was purified
by column chromatography over silica gel with ethyl acetate and
hexane as the eluents (38:5) to give 0.76 g (61%) of G0-CX4: 1H
NMR (CDCl3, 400 MHz) δ 8.09 (d, J ) 7.6 Hz, 16H, H30,34,36,40),
7.74 (br s, 8H, H32,38), 7.56-7.51 (m, 20H, H31,33,37,39,44), 7.23 (br
s, 16H, H42,43,45,46), 7.03 (br s, 8H, H10,24), 6.87 (d, J ) 6.6 Hz, 8H,
was removed under vacuum to yield a light yellow solid. The
mixture was purified initially through a silica gel column with
CH2Cl2 and hexane as the eluent (7:1) and then through silica gel
with ethyl acetate, hexane, and CH2Cl2 (4:2:4) to give 0.83 g (42%)
of G1-CX12: 1H NMR (CDCl3, 500 MHz) δ 8.06 (d, J ) 7.6 Hz,
48H, H30,34,36,40), 7.74 (br s, 24H, H32,38), 7.48 (br s, 60H,
H
31,33,37,39,44), 7.25 (br s, 24H, H43,46), 7.22 (br s, 24H, H42,45), 7.03
(br s, 24H, H10,24), 6.86 (d, J ) 6.5 Hz, 24H, H16,18), 6.80 (s, 24H,
4,6), 6.71 (t, J ) 7.6 Hz, 12H, H17), 6.59 (br s, 48H, H11,12,22,23
H
)
5.18 (s, 12H, OH), 3.84 (d, J ) 14.8 Hz, 24H, H2,8 up), 3.81 (d, J
) 14.8 Hz, 24H, H14,20 up), 3.70 (d, J ) 14.8 Hz, 24H, H14,20 down),
3.42 (d, J ) 14.8 Hz, 24H, H2,8 down), 2.42 (br s, 24H, ArCH2CH2),
1.52 (br s, 24H, SiCH2CH2), 1.33 (br s, 24H, SiCH2CH2), 1.24 (s,
18H, SiCH2CH2), 0.58 (br s, 54H, SiCH2), 0.52 (br s, 24H, SiCH2),
0.09 (s, 72H, SiCH3), 0.02 (s, 72H, SiCH3); 13C NMR (CDCl3) δ
0.8, 18.5, 26.0, 33.1, 37.7, 39.0, 125.4, 126.0, 127.8, 128.0, 128.4,
128.9, 129.1, 129.4, 129.8, 130.6, 131.0, 131.6, 133.1, 133.2, 133.5,
133.7, 134.0, 147.1, 148.55, 151.1, 164.2, 164.7; 29Si NMR (CDCl3)
δ 7.37, 6.76, 0.92, -3.99; MS (MALDI-TOF) m/z calcd (found)
for (C720H732O96Si29 + 2Na)2+ 5888.5 (5888.5). Anal. Calcd (found)
for C720H732O96Si29: C, 73.69 (73.76); H, 6.29 (6.19).
H
16,18), 6.81 (s, 8H, H4,6), 6.71 (t, J ) 7.6 Hz, 4H, H17), 6.60-6.58
(m, 16H, H11,12,22,23) 5.18 (s, 4H, OH), 3.86 (d, J ) 15.1 Hz, 8H,
2,8 up), 3.85 (d, J ) 15.1 Hz, 8H, H14,20 up), 3.72 (d, J ) 15.1 Hz,
H
8H, H14,20 down), 3.50 (d, J ) 15.1 Hz, 8H, H2,8 down), 2.44 (br s, 8H,
ArCH2CH2), 1.54 (br s, 8H, ArCH2CH2CH2), 1.47 (br s, 8H,
SiCH2CH2CH2Si), 0.61-0.58 (m, 16H, SiCH2), 0.52 (br s, 8H,
SiCH2), 0.07 (s, 24H, SiCH3), 0.03 (s, 24H, SiCH3); 13C NMR
(CDCl3) δ 0.8, 18.4, 26.0, 33.1, 37.7, 39.0, 125.4, 126.2, 127.8,
128.0, 129.0, 128.9, 129.1, 129.4, 129.8, 130.5, 131.1, 131.6, 133.0,
133.2, 133.4, 133.7, 134.0, 147.1, 148.5, 151.0, 164.2, 164.7; 29Si
NMR (CDCl3) δ 7.47, 6.75, -3.33; MS (MALDI-TOF) m/z calcd
(found) for (C236H236O32Si9 + Na)+ 3858 (3858.7). Anal. Calcd
(found) for C236H236O32Si9: C, 73.87 (73.34); H, 6.20 (6.23).
Dendritic First Generation Dodecacalix[4]arene-End-Capped
Carbosilane (G1-CX12). Compound 6 (2.14 g, 0.24 mol), dried
THF (30 mL), the first generation, dodecaallyl carbosilane (G1,
0.13 g, 0.17 mmol), and Karstedt’s catalyst25 (20 µL, 2.1-2.4%
Pt in xylene) were placed in a 50-mL, two-necked, round-bottomed
flask equipped with a condenser and a magnetic stirrer under N2
atmosphere. The mixture was stirred at room temperature for 15
min and at reflux for 4 days. The flask was cooled, and the solvent
Acknowledgment. This work was supported by the National
Science Foundation (Grant no. CHE-0349412).
Supporting Information Available: 1H spectra of 2-6, G0,
G0-CX4, G1, and G1-CX12, 13C spectra of 6, G0-CX4, and
G1-CX12, and 29Si spectra of 6, G0-CX4, and G1-CX12. This
material is available free of charge via the Internet at http://
pubs.acs.org.
JO802714Q
2532 J. Org. Chem. Vol. 74, No. 6, 2009