Control of surface functionality in poly(phenylenevinylene) dendritic architectures

Article abstract of DOI:10.1021/jo070210v

(Chemical Equation Presented) The efficient synthesis of new asymmetric poly(phenylenevinylene) dendritic macromolecules using a stepwise convergent-growth approach is described. By an iterative methodology that made use of the Horner-Wadsworth-Emmons (HW

Full text of DOI:10.1021/jo070210v

Control of Surface Functionality in Poly(phenylenevinylene)
Dendritic Architectures
Juan Tolosa, Carlos Romero-Nieto, Enrique D´ıez-Barra, Prado Sa´nchez-Verdu´,* and
Julia´n Rodr´ıguez-Lo´pez*
Facultad de Qu´ımica, UniVersidad de Castilla-La Mancha, 13071 Ciudad Real, Spain
julian.rodriguez@uclm.es
ReceiVed February 1, 2007
The efficient synthesis of new asymmetric poly(phenylenevinylene) dendritic macromolecules using a
stepwise convergent-growth approach is described. By an iterative methodology that made use of the
Horner-Wadsworth-Emmons (HWE) reaction, dendrons and dendrimers up to the third generation,
with eight different functional groups located at the periphery, were prepared in good yields. Both the
number and placement of functionalities can be accurately controlled to afford a large variety of dendritic
architectures.
Introduction
each other.4 They prepared benzyl ether-based dendritic struc-
tures, although the synthesis of dendrimers based on melamine
with multifunctional periphery has also been achieved.5 Diver-
sity in functional group display has been also performed through
divergent approaches;6 however, their inherent nature does not
allow generating structures in which every peripheral unit is
different.
Dendritic poly(phenylenevinylene)s (PPVs), also called stil-
benoid dendrimers, represent an important group within this
class of material. Different studies have been published to date
concerning their synthesis and properties.7 For example, such
compounds have been used successfully as charge transporting,8
In the past two decades a large number of functional
dendrimers have been developed. Synthetic methodologies for
their preparation, involving convergent and divergent methods,
are well established,1 but the wide scope of their applications
is continuously growing.2 This further increases the burden of
synthesis. The convergent approach appears ideally suited for
the preparation of dendrimers in which control over both the
number and the placement of end functionalities is achieved.
Thus, this methodology has been widely used by different
authors for the synthesis of highly asymmetrical dendrimers
containing a predetermined and well-defined number and
arrangement of functional groups at their periphery.3 Th-
ayumanavan et al. were the first to build dendrons and
dendrimers in which all the monomer units are different from
(3) (a) Hawker, C. J.; Fre´chet, J. M. J. Macromolecules 1990, 23, 4726-
4729. (b) Wooley, K. L.; Hawker, C. J.; Fre´chet, J. M. J. J. Chem. Soc.,
Perkin Trans. 1 1991, 1059-1076. (c) Bo, Z.; Scha¨fer, A.; Franke, P.;
Schlu¨ter, A. D. Org. Lett. 2000, 2, 1645-1648. (d) Zhang, W.; Nowlan,
D. T., III; Thomson, L. M.; Lackowski, W. M.; Simanek, E. E. J. Am.
Chem. Soc. 2001, 123, 8914-8922. (e) Ganesh, R. N.; Shraberg, J.;
Sheridan, P. G.; Thayumanavan, S. Tetrahedron Lett. 2002, 43, 7217-
7220.
(1) (a) Newkome, G. R.; Moorefield, C. N.; Vo¨gtle, F. Dendrimers and
Dendrons; Wiley-VCH: Weinheim, 2001. (b) Dendrimers and Other
Dendritic Polymers; Fre´chet, J. M. J., Tomalia, D. A., Eds.; Wiley:
Chichester, 2001. (c) Vo¨gtle, F., Ed. Top. Curr. Chem. 1998, 197. (d)
Bosman, A. W.; Janssen, H. M.; Meijer, E. W. Chem. ReV. 1999, 99, 1665-
1688. (e) Majoral, J. P.; Caminade, A. M. Chem. ReV. 1999, 99, 845-880.
(f) Zeng, F.; Zimmerman, S. C. Chem. ReV. 1997, 97, 1681-1712. (g)
Smith, D. K.; Diederich, F. Chem. Eur. J. 1998, 4, 1353-1361.
(2) (a) Fischer, M.; Vo¨gtle, F. Angew. Chem., Int. Ed. 1999, 38, 884-
905. (b) Issberner, J.; Moors, R.; Vo¨gtle, F. Angew. Chem., Int. Ed. Engl.
1994, 33, 2413-2420.
(4) (a) Sivanandan, K.; Vutukuri, D.; Thayumanavan, S. Org. Lett. 2002,
4, 3751-3753. (b) Vutukuri, D.; Bharathi, P.; Yu, Z.; Rajasekaran, K.; Tran,
M.-H.; Thayumanavan, S. J. Org. Chem. 2003, 68, 1146-1149. (c)
Vutukuri, D. R.; Sivanandan, K.; Thayumanavan, S. Chem. Commun. 2003,
796-797. (d) Sivanandan, K.; Sandanaraj, B. S.; Thayumanavan, S. J. Org.
Chem. 2004, 69, 2937-2944.
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10.1021/jo070210v CCC: $37.00 © 2007 American Chemical Society
Published on Web 04/18/2007
J. Org. Chem. 2007, 72, 3847-3852
3847

SCHEME 1. Synthesis of Asymmetrical First and Second Generation Dendrons
light-emitting,9 and electron-transfer materials.10 It has also been
demonstrated that phenylenevinylene dendritic arms can function
as light-harvesting antennae.9b Nevertheless, the routes that
afford the buildup of this class of materials in an asymmetrically
surface-functionalized fashion are exceedingly few.11
In this context and as a part of our research program aimed
at the construction of extended and cross-conjugated π-electronic
systems,11a we planned to develop an efficient orthogonal and
convergent-growth methodology of new asymmetric dendrimer
architectures containing phenylenevinylene chromophores within
the branches. This has been achieved by the stepwise incorpora-
tion of functionalities in a controlled manner onto an AB2-type
monomer unit, using the Horner-Wadsworth-Emmons (HWE)
reaction. This reaction has already produced interesting results
when applied to the synthesis of dendrimers.7a-i,9a,b,10,12 In this
way, a large variety of dendritic structures were prepared in
good yields, including dendrons and dendrimers up to the third
generation with eight different functional groups located at the
periphery.
(6) (a) Newkome, G. R.; Weis, C. D.; Moorefield, C. N.; Baker, G. R.;
Childs, B. J.; Epperson, J. Angew. Chem. Int. Ed. 1998, 37, 307-310. (b)
Newkome, G. R.; Kim, H. J.; Moorefield, C. N.; Maddi, H.; Yoo, K.-S.
Macromolecules 2003, 36, 4345-4354. (c) Newkome, G. R.; Yoo, K. S.;
Hwang, S.-H.; Moorefield, C. N. Tetrahedron 2003, 59, 3955-3964. (d)
Larre´, C.; Donnadieu, B.; Caminade, A.-M.; Majoral, J.-P. J. Am. Chem.
Soc. 1998, 120, 4029-4030. (e) Latigue, M.-L.; Slany, M.; Caminade, A.-
M.; Majoral, J.-P. Chem. Eur. J. 1996, 2, 1417-1426. (f) Woller, E. K.;
Walter, E. D.; Morgan, J. R.; Singel, D. J.; Cloninger, M. J. J. Am. Chem.
Soc. 2003, 125, 8820-8826.
(7) (a) Maddux, T. M.; Yu, L. J. Am. Chem. Soc. 1997, 119, 9079-
9080. (b) Meier, H.; Lehmann, M. Angew. Chem., Int. Ed. Engl. 1998, 37,
643-645. (c) Lehmann, M.; Schartel, B.; Hennecke, M.; Meier, H.
Tetrahedron 1999, 55, 13377-13394. (d) Pilow, J. N. G.; Burn, P. L.;
Samuel, I. D. W.; Halim, M. Synth. Met. 1999, 102, 1468-1469. (e) Meier,
H.; Lehmann, M.; Kolb, U. Chem. Eur. J. 2000, 6, 2462-2469. (f) Segura,
J. L.; Go´mez, R.; Mart´ın, N.; Guldi, D. M. Org. Lett. 2001, 3, 2645-2648.
(g) Palsson, L.-O.; Beavington, R.; Frampton, M. J.; Lupton, J. M.;
Magennis, S. W.; Markham, J. P. J.; Pillow, J. N. G.; Burn, P. L.; Samuel,
I. D. W. Macromolecules 2002, 35, 7891-7901. (h) Lehmann, M.;
Fischbach, I.; Spiess, H. W.; Meier, H. J. Am. Chem. Soc. 2004, 126, 772-
784. (i) Lehmann, M.; Ko¨hn, C.; Meier, H.; Renker, S.; Oehlhof, A. J.
Mater. Chem. 2006, 16, 441-451. (j) Sengupta, S.; Sadhukhan, S. K.; Singh,
R. S.; Pal, N. Tetrahedron Lett. 2002, 43, 1117-1121. (k) Meier, H.;
Lehmann, M. In Encyclopedia of Nanoscience and Nanotechnology; Nalwa,
H. S., Ed.; American Scientific: Stevensons Ranch, 2004; Vol. 10, pp 95-
106. (l) Rosenfeldt, S.; Karpuk, E.; Lehmann, M.; Meier, H.; Lindner, P.;
Harnau, L.; Ballauff, M. Chem. Phys. Chem. 2006, 7, 2097-2104.
(8) Lupton, J. M.; Samuel, I. D. W.; Beavington, R.; Burn, P. L.; Ba¨ssler,
H. AdV. Mater. 2001, 13, 258-261.
Results and Discussion
Our plan was based on our previous work directed toward
symmetrical or uniformly functionalized PPV dendrimers11a and
(11) (a) D´ıez-Barra, E.; Garc´ıa-Mart´ınez, J. C.; Merino, S.; del Rey, R.;
Rodr´ıguez-Lo´pez, J.; Sa´nchez-Verdu´, P.; Tejeda, J. J. Org. Chem. 2001,
66, 5664-5670. (b) Weil, T.; Wiesler, U. M.; Herrmann, A.; Bauer, R.;
Hofkens, J.; De Schryver, F. C.; Mu¨llen, K. J. Am. Chem. Soc. 2001, 123,
8101-8108.
(12) See, for example: (a) Pre´voˆte´, D.; Le Roy-Gourvennec, S.;
Caminade, A.-M.; Masson, S.; Majoral, J.-P. Synthesis 1997, 1199-1207.
(b) McElhanon, J. R.; Wu, M.-J.; Escobar, M.; Chaudhry, U.; Hu, C.-L.;
McGrath, D. V. J. Org. Chem. 1997, 62, 908-915. (c) Mongin, O.; Brunel,
J.; Porre`s, L.; Blanchard-Desce, M. Tetrahedron Lett. 2003, 44, 2813-
2816. (d) Jiang, Y.; Wang, J.-Y.; Ma, Y.; Cui, Y.-X.; Zhou, Q.-F.; Pei, J.
Org. Lett. 2006, 8, 4287-4290.
(9) (a) Pillow, J. N. G.; Halim, M.; Lupton, J. M.; Burn, P. L.; Samuel,
I. D. W. Macromolecules 1999, 32, 5985-5993. (b) Halim, M.; Pillow, J.
N. G.; Samuel, I. D. W.; Burn, P. L. AdV. Mater. 1999, 11, 371-374. (c)
Ma, D.; Lupton, J. M.; Beavington, R.; Burn, P. L.; Samuel, I. D. W. AdV.
Funct. Mater. 2002, 12, 507-511.
(10) (a) Guldi, D. M.; Swartz, A.; Luo, C.; Go´mez, R.; Segura, J. L.;
Mart´ın, N. J. Am. Chem. Soc. 2002, 124, 10875-10886. (b) Kwon, T. W.;
Alam, M. M.; Jenekhe, S. A. Chem. Mater. 2004, 16, 4657-4666.
3848 J. Org. Chem., Vol. 72, No. 10, 2007

SCHEME 2. Synthesis of Asymmetrical Third Generation Dendron 9
SCHEME 3. Synthesis of Asymmetrical Dendrimer 12
made use of the HWE reaction. Diphosphonate 1 was required
as starting material,13 which contains two coupling sites, as well
as a set of either commercially or easily available differently
substituted benzaldehyde derivatives.
Scheme 1 shows our iterative approach to obtain homoge-
neous single functionality dendrons, which contained either an
iodo or formyl group at the focal point. The first reaction
sequence involved the HWE reaction of one molecule of a
benzaldehyde derivative with monomer 1 to form compounds
2a-f, having a free reactive phosphonate group for further
coupling. The synthesis was carried out by using only 1.2 equiv
of 1 and KtBuO in THF at 0 °C. Although the presence of
starting material 1 and the corresponding dicoupled products
were also observed in the crude mixture, all of the monophos-
phonates 2 could be easily separated by column chromatography
(silica gel) in good yields (50-80%). A second HWE reaction
with a different benzaldehyde derivative gave the desired
asymmetrical, first-generation dendrons, 3a-d. Ultimately, two
different functional groups are located at the periphery or chain
end of the final branched molecules.14
The selectivity of the HWE reactions was sufficiently high
to generate all-trans isomers within the limits of NMR detection.
This stereochemistry for the double bonds was unequivocally
established on the basis of the coupling constant of the vinylic
1
protons in the H NMR spectra (J ≈ 16 Hz).
n
Subsequent treatment of dendrons 3 with BuLi at -78 °C
followed by reaction with DMF gave the corresponding first-
generation compounds 4a-d bearing a formyl group at the focal
point. These aldehydes are the precursors of the next generation
dendrons 6, which were synthesized by a two-step iterative
procedure. Thus, in a similar way as above, compounds 4a and
4c were coupled with a slight excess of diphosphonate 1 to
afford the monocoupled products 5a and 5b, respectively, which
after a new HWE reaction with a different first-generation
aldehyde 4 formed the asymmetric second-generation dendritic
wedges 6a,b. Transformation into the corresponding aldehyde
derivatives 7a,b could be also obtained in good yields.
Proceeding to generation three, the synthesis of compound 9
was taken as a model, in which all eight branches are different.
Its preparation involved the HWE reaction of the second-
generation dendron 7a with a slight excess of monomer 1. In
this way, monophosphonate derivative 8 was isolated in 84%
yield after purification. Then, its coupling with the second-
generation aldehyde 7b led to the desired target with a wide
variety of peripheral groups (Scheme 2).
In principle, these reaction sequences could be further
progressed through multiple cycles, although in practice one
would expect that higher molecules would be difficult to prepare
because of the well-documented progressive reduction in the
reactivity of the focal point in successive generations.13,15
(13) D´ıez-Barra, E.; Garc´ıa-Mart´ınez, J. C.; Rodr´ıguez-Lo´pez, J. J. Org.
Chem. 2003, 68, 832-838.
(14) Tolosa, J.; D´ıez-Barra, E.; Sa´nchez-Verdu´, P.; Rodr´ıguez-Lo´pez, J.
Tetrahedron Lett. 2006, 47, 4647-4651.
J. Org. Chem, Vol. 72, No. 10, 2007 3849

FIGURE 1. MALDI-TOF mass spectrum of compound 12 in a matrix of dithranol.
The groups selected in this work provided good control of
the solubility. Indeed, all new molecules prepared are highly
soluble in THF as well as in chlorinated solvents such as
dichloromethane and chloroform, thus allowing purification by
conventional silica gel chromatography. A suitable choice of
starting materials could provide a wide variety of dendritic
architectures with different peripheral moieties, although pe-
ripheral pendant groups should be adequately chosen in order
to impart solubility. An example of this potential is shown by
the synthesis of the third generation dendrimer 12 starting from
the nucleus 10 and the dendrons 7a,b (Scheme 3).
All compounds were characterized using various analytical
techniques. MS and NMR experiments proved very useful to
confirm the structures of the compounds (see Experimental
Section and Supporting Information). Assessment of the overall
purity of these molecules proved difficult. The 1H NMR spectra
of dendrons up to generation two are well-resolved in CDCl3
and do not reveal impurities, but the high number of lines in
the 7-8 ppm zone could obscure the presence of small amounts
of other compounds. Compounds 9 and 12 showed considerable
line broadening at 25 °C, which has its origin in reduced
segment mobility, a behavior that has been previously observed
in high generation PPV dendrimers.7b,e However, their spectra
were temperature-dependent, and quite normally resolved signals
were obtained by heating the sample at 72 °C. The MALDI-
TOF technique proved to be very useful for the identification
of the higher structures. All of the spectra registered for the
higher generations showed peaks matching the calculated
molecular weights. As an example, the MALDI-TOF mass
spectrum for the third generation dendrimer 12 is given in Figure
1, showing a perfect agreement between the calculated and
experimentally determined m/z ratio and demonstrating the
absence of molecules that contain only one dendron.
FIGURE 2. Elution profile in size exclusion chromatography for
dendrimer 12.
FIGURE 3. UV-vis absorption and fluorescence spectra of dendron
9 (dotted line, λexc ) 325 nm) and dendrimer 12 (solid line, λexc) 329
nm) (c ) 10-6 M in CH2Cl2 at room temperature).
The size exclusion chromatography elution profile of com-
pound 12 is also shown in Figure 2. It confirms that this
molecule is clean and obtained in good purity.
The UV-vis absorption and photoluminescence (PL) spectra
of compounds 9 and 12 were recorded in CH2Cl2 at room
temperature (Figure 3). Owing to the meta arrangement through
which the stilbene units are linked, it was expected that the
absorption spectra would consist of a simple superposition of
the absorptions due to the constituent independent chro-
mophores. Indeed, strong bands with maxima at 325 nm for 9
and 329 nm for 12 and large extinction coefficients (ꢀ ) 348000
and 355300 M-1 cm-1, respectively) are observed. The mol-
ecules are absolutely transparent above 440 nm. They are also
fluorescent and emit strong light when irradiated at the
absorption maxima, showing a typical response for the PPV
dendrimers,11a with a maximum at 509 nm and a shoulder at
ca. 434 nm for 9 and a maximum at 510 nm and shoulders at
ca. 412 and 434 nm for 12. The emission spectra obtained by
irradiation at different wavelengths are the same regardless of
the excitation frequency.
(15) Grayson, S. M.; Fre´chet, J. M. J. Chem. ReV. 2001, 101, 3819-
3868.
3850 J. Org. Chem., Vol. 72, No. 10, 2007

(d, J ) 7.2 Hz, CH2), 40.1 (CH3), 32.9 (d, J ) 137.0 Hz, CH2),
16.2 (d, J ) 5.6 Hz, CH3). MS (EI) m/e 499.1 (100). HRMS, m/e
calcd for C21H27INO3P 499.0773; found 499.0765.
Conclusions
New PPV dendritic structures with differentiated surface
functionalities have been effectively synthesized up to the third
generation using an orthogonal, convergent-growth sequencing
methodology based on the HWE reaction. This iterative strategy
is extremely general, permitting not only the use of a wide
variety of functional groups but also an exquisite control over
their placement. The stepwise incorporation of functionalities
onto an AB2 monomer unit proceeds with good yields in the
desired product. This approach has its obvious drawback: the
desired monosubstituted product is obtained in statistical yield
together with the corresponding undesired disubstituted byprod-
uct. However, it avoids the need for protection-deprotection steps
that are much more time-consuming. Thus, the methodology
reported here may be used as an accelerated access to a wide
range of asymmetrically conjugated dendritic architectures. With
this methodology the synthesis of many PPV dendrimers with
specific substitution patterns would become possible.
Compound 3b. Purified by column chromatography (SiO2,
hexanes/EtAcO, 9:1) and washed with cold ethanol. Yield: 86%.
1
Colorless solid. Mp 84-86 °C. H NMR (CDCl3, 500 MHz) δ:
0.91 (t, 3H, J ) 7.0 Hz), 1.32-1.38 (m, 4H), 1.43-1.50 (m, 2H),
1.79 (m, 2H), 3.83 (s, 3H), 3.98 (t, 2H, J ) 6.5 Hz), 6.85 (A of
ABq, 1H, J ) 16.5 Hz), 6.86 (A of ABq, 1H, J ) 16.5 Hz), 6.89
(A of ABq, 2H, J ) 9.0 Hz), 6.91 (A of ABq, 2H, J ) 9.0 Hz),
7.06 (B of ABq, 1H, J ) 16.5 Hz), 7.06 (B of ABq, 1H, J ) 16.5
Hz), 7.43 (B of ABq, 2H, J ) 9.0 Hz), 7.45 (B of ABq, 2H, J )
9.0 Hz), 7.48 (broad s, 1H), 7.69 (s, 1H), 7.69 (s, 1H). 13C NMR
and DEPT (CDCl3, 125 MHz) δ: 159.6 (C), 159.2 (C), 140.0 (C),
140.0 (C), 133.5 (CH), 133.4 (CH), 129.8 (CH), 129.7 (CH), 129.6
(C), 129.4 (C), 127.9 (CH), 127.9 (CH), 124.8 (CH), 124.6 (CH),
123.7 (CH), 114.8 (CH), 114.2 (CH), 95.2 (C), 68.1 (CH2), 55.3
(CH3), 31.6 (CH2), 29.2 (CH2), 25.7 (CH2), 22.6 (CH2), 14.0 (CH3).
MS (EI) m/e 538.1 (M+, 100), 454.0 (53). HRMS, m/e calcd for
C29H31IO2 538.1369; found 538.1367. Anal. Calcd for C29H31IO2:
C, 64.69; H, 5.80; I, 23.57. Found: C, 64.74; H, 5.78; I, 23.32.
Compound 4a. Purified by column chromatography (SiO2,
hexanes/EtAcO, 9.9:0.1). Yield: 87%. Yellow oil that solidified
Experimental Section
General Procedures for Horner-Wadsworth-Emmons Re-
actions. Method A (Synthesis of Monosubstituted Phospho-
nates). To a stirred solution of diphosphonate 1 (1.2 mmol) in
anhydrous THF (15 mL), under argon at 0 °C, was added potassium
tert-butoxide in small portions (1.2 mmol). Ten minutes later the
corresponding aromatic aldehyde (1 mmol) dissolved in THF was
added, and the reaction mixture was stirred at that temperature for
2 h. After hydrolysis with water, the mixture was extracted with
EtAcO (×3). The combined organic layers were successively
washed with water and brine and then dried (MgSO4). The solution
was filtered, and the solvent was evaporated under reduced pressure.
The crude products were purified by column chromatography (silica
gel) as indicated. Method B (Synthesis of Dendritic Iodides). All
operations were identical with those described for method A except
that the corresponding monosubstituted phosphonate was used as
starting material (1 mmol/mmol of aldehyde). The reactions were
carried out at room temperature. After hydrolysis with water, the
mixture was extracted with CH2Cl2 (×3). The combined organic
layers were successively washed with water and brine and then
dried (MgSO4). The solution was filtered, and the solvent was
evaporated under reduced pressure. The crude products were
purified by column chromatography (silica gel) and/or crystallization
as indicated.
General Procedure for the Synthesis of Dendritic Aldehydes.
To a stirred solution of the corresponding iodide derivative in
anhydrous THF (15 mL per mmol), under argon at -78 °C, was
added dropwise nBuLi (1.1 equiv). After 10 min, 3 equiv of DMF
was added to quench the reaction mixture, which was then allowed
to reach room temperature over a period of 3 h. The mixture was
concentrated, taken up in chloroform, washed with water twice,
and dried (MgSO4). The solution was filtered, and the solvent was
evaporated under reduced pressure. The crude products were
purified by column chromatography (silica gel) and/or crystallization
as indicated.
1
upon standing. H NMR (CDCl3, 500 MHz) δ: 0.97 (t, 6H, J )
7.5 Hz), 1.30-1.40 (m, 4H), 1.56-1.62 (m, 4H), 2.37 (s, 3H), 3.30
(t, 4H, J ) 7.5 Hz), 6.64 (A of ABq, 2H, J ) 9.0 Hz), 6.91 (A of
ABq, 1H, J ) 16.5 Hz), 7.10 (A of ABq, 1H, J ) 16.0 Hz), 7.16
(B of ABq, 1H, J ) 16.5 Hz), 7.19 (A of ABq, 2H, J ) 8.0 Hz),
7.21 (B of ABq, 1H, J ) 16.0 Hz), 7.40 (B of ABq, 2H, J ) 9.0
Hz), 7.44 (B of ABq, 2H, J ) 8.0 Hz), 7.78 (s, 1H), 7.81 (s, 1H),
7.84 (s, 1H), 10.05 (s, 1H). 13C NMR and DEPT (CDCl3, 125 MHz)
δ: 192.6 (CH), 148.2 (C), 139.8 (C), 138.7 (C), 138.0 (C), 137.1
(C), 134.1 (C), 130.9 (CH), 130.3 (CH), 129.6 (CH), 129.5 (CH),
128.0 (CH), 126.6 (CH), 126.3 (CH), 125.7 (CH), 125.1 (CH), 123.7
(C), 121.7 (CH), 111.6 (CH), 50.8 (CH2), 29.5 (CH2), 21.3 (CH3),
20.3 (CH2), 14.0 (CH3). IR ν: 1670 (CdO) cm-1. MS (EI) m/e
451.3 (M+, 82), 408.2 (100), 366.2 (41). HRMS, m/e calcd for
C32H37NO 451.2875; found 451.2885. Anal. Calcd for C32H37NO:
C, 85.10; H, 8.26; N, 3.10. Found: C, 84.89; H, 8.27; N, 3.12.
Compound 5b. Purified by column chromatography (SiO2,
1
hexanes/EtAcO, 1:1, then EtAcO). Yield: 83%. Yellow oil. H
NMR (CDCl3, 500 MHz) δ: 0.88 (t, 6H, J ) 7.0 Hz), 0.89 (t, 3H,
J ) 7.0 Hz), 1.20-1.40 (m, 54H), 1.45-1.53 (m, 6H), 1.76 (m,
2H, J ) 7.0 Hz), 1.84 (m, 4H, J ) 7.0 Hz), 3.01 (s, 6H), 3.11 (d,
2H, J ) 21.6 Hz), 3.98 (t, 2H, J ) 6.6 Hz), 4.03-4.10 (m, 8H),
6.75 (broad s, 4H), 6.94 (A of ABq, 1H, J ) 16.3 Hz), 7.00 (A of
ABq, 1H, J ) 16.2 Hz), 7.05 (A of ABq, 1H, J ) 16.3 Hz), 7.09
(B of ABq, 1H, J ) 16.3 Hz), 7.13 (B of ABq, 1H, J ) 16.5 Hz),
7.13 (B of ABq, 1H, J ) 16.3 Hz), 7.35-7.54 (m, 7H), 7.79 (d,
1H, J ) 1.6 Hz). 13C NMR and DEPT (CDCl3, 125 MHz) δ: 153.3
(C), 150.1 (C), 139.5 (d, J ) 3.1 Hz, C), 138.9 (C), 139.3 (C),
138.0 (C), 137.4 (d, J ) 6.8 Hz, CH), 137.2 (C), 134.1 (d, J ) 8.9
Hz, C), 133.8 (d, J ) 3.0 Hz, CH), 132.4 (C), 130.2 (CH), 129.4
(CH), 129.3 (CH), 127.7 (CH), 127.4 (d, J ) 6.4 Hz, CH), 127.3
(CH), 126.9 (CH), 125.5 (C), 123.9 (CH), 123.5 (CH), 122.8 (CH),
120.6 (CH), 112.4 (CH), 105.1 (CH), 94.6 (d, J ) 3.5 Hz, C), 73.5
(CH2), 69.1 (CH2), 62.3 (d, J ) 6.8 Hz, CH2), 40.4 (CH3), 33.2 (d,
J ) 138.4 Hz, CH2), 31.9 (CH2), 31.9 (CH2), 30.3 (CH2), 29.7
(CH2), 29.7 (CH2), 29.7 (CH2), 29.7 (CH2), 29.6 (CH2), 29.6 (CH2),
29.4 (CH2), 29.4 (CH2), 29.4 (CH2), 29.3 (CH2), 26.1 (CH2), 22.7
(CH2), 22.6 (CH2), 16.4 (d, J ) 5.9 Hz, CH3), 14.1 (CH3). 31P NMR
(CDCl3, 162 MHz) δ: 26.1. MS (MALDI) m/e 1256.7 (MH+),
1129.8 (MH+ - 127). HRMS, m/e calcd for C73H111INO6P:
1255.7194; found 1255.7206.
Representative examples for the preparation of different dendrons
and dendrimers are described below.
Compound 2e. Purified by column chromatography (SiO2,
1
hexanes/EtAcO, 1:1). Yield: 67%. Yellow oil. H NMR (CDCl3,
500 MHz) δ: 1.25 (t, 6H, J ) 7.0 Hz), 2.94 (s, 6H), 3.04 (d, 2H,
J ) 21.5 Hz), 4.00-4.10 (m, 4H, J ) 7.0 Hz), 6.67 (A of ABq,
2H, J ) 8.5 Hz), 6.72 (A of ABq, 1H, J ) 16.5 Hz), 6.99 (B of
ABq, 1H, J ) 16.0 Hz), 7.32 (br s, 1H), 7.35 (B of ABq, 2H, J )
8.5 Hz), 7.42 (br s, 1H), 7.67 (br s, 1H). 13C NMR and DEPT
(CDCl3, 125 MHz) δ: 150.0 (C), 140.2 (d, J ) 3.2 Hz, C), 136.1
(d, J ) 6.4 Hz, CH), 133.7 (d, J ) 9.6 Hz, C), 132.9 (d, J ) 3.1
Hz, CH), 130.1 (CH), 127.5 (CH), 126.5 (d, J ) 7.2 Hz, CH),
124.7 (C), 121.8 (CH), 112.1 (CH), 94.4 (d, J ) 4.0 Hz, C), 62.0
Compound 6b. Purified by washing with methanol. Yield: 94%.
Yellow solid. 1H NMR (CDCl3, 500 MHz) δ: 0.85-0.90 (m, 12H),
1.20-1.40 (m, 64H), 1.43-1.53 (m, 8H), 1.73-1.87 (m, 8H), 2.36
(s, 6H), 3.00 (s, 6H), 3.98 (t, 2H, J ) 6.6 Hz), 3.99 (t, 2H, J ) 6.6
Hz), 4.04 (t, 4H, J ) 6.5 Hz), 6.75 (broad s, 4H), 6.91 (A of ABq,
J. Org. Chem, Vol. 72, No. 10, 2007 3851

2H, J ) 9.0 Hz), 6.92-7.22 (m including AB systems, 15H, J )
16.0 Hz, J ) 16.5 Hz), 7.45 (B of ABq, 2H, J ) 8.8 Hz), 7.47 (B
of ABq, 2H, J ) 8.8 Hz), 7.50-7.55 (m, 6H), 7.60 (broad s, 1H),
7.78 (broad s, 2H). 13C NMR and DEPT (CDCl3, 125 MHz) δ:
159.0 (C), 153.3 (C), 150.1 (broad, C), 139.7 (C), 139.6 (C), 138.9
(C), 138.5(C), 138.4 (C), 138.2 (C), 138.1 (C), 138.1 (C), 137.4
(C), 137.3 (C), 137.1 (C), 134.3 (CH), 134.2 (CH), 132.4 (C), 130.2
(CH), 130.1 (CH), 129.7 (C), 129.6 (CH), 129.5 (CH), 129.4 (CH),
129.0 (CH), 127.9 (CH), 127.8 (CH), 127.7 (CH), 127.4 (CH), 127.2
(CH), 127.1 (CH), 125.9 (CH), 124.5 (CH), 124.2 (CH), 123.9 (CH),
123.7 (CH), 123.5 (CH), 123.5 (CH), 123.0 (CH), 114.7 (CH), 112.5
(broad, CH), 105.2 (CH), 95.2 (C), 73.6 (CH2), 69.2 (CH2), 68.1
(CH2), 40.5 (broad, CH3), 31.9 (CH2), 31.9 (CH2), 30.4 (CH2), 29.8
(CH2), 29.7 (CH2), 29.7 (CH2), 29.7 (CH2), 29.7 (CH2), 29.6 (CH2),
29.6 (CH2), 29.6 (CH2), 29.5 (CH2), 29.5 (CH2), 29.4 (CH2), 29.4
(CH2), 29.4 (CH2), 29.3 (CH2), 29.3 (CH2), 26.2 (CH2), 26.1 (CH2),
22.7 (CH2), 21.3 (CH3), 14.1 (CH3). MS (MALDI) m/e 1625.0
(MH+), 1498.0 (MH+ - 127). HRMS, m/e calcd for C106H146INO4
1624.0297; found 1624.0269.
138.6 (C), 138.6 (C), 138.4 (C), 138.4 (C), 138.4 (C), 138.4 (C),
138.3 (C), 138.1 (C), 138.0 (C), 137.9 (C), 137.9 (C), 137.8 (C),
137.8 (C), 137.7, (C), 137.5 (C), 137.4 (C), 137.3 (C), 134.9 (C),
134.6 (CH), 132.7 (C), 130.4 (C), 130.2 (C), 130.1 (CH), 129.6
(CH), 129.6 (CH), 129.5 (CH), 129.2 (CH), 129.1 (CH), 129.0 (CH),
128.9 (CH), 128.7(CH), 128.6 (CH), 128.6 (CH), 128.5 (CH), 128.2
(CH), 128.0 (CH), 127.9 (CH), 127.9 (CH), 127.8 (CH), 127.7 (CH),
127.6 (CH), 127.5 (CH), 126.6 (CH), 126.4 (CH), 126.4 (CH), 124.7
(CH), 124.4 (CH), 124.3 (CH), 124.2 (CH), 124.1 (CH), 124.0 (CH),
124.0 (CH), 123.9 (CH), 123.9 (CH), 123.6 (CH), 123.6 (CH), 123.5
(CH), 123.2 (CH), 115.1 (CH), 114.4 (CH), 112.8 (CH), 106.2 (CH),
95.2 (C), 73.7 (CH2), 69.7 (CH2), 68.4 (CH2), 55.3 (CH3), 51.4
(broad, CH2), 40.5 (CH3), 32.0 (CH2), 32.0 (CH2), 31.7 (CH2), 30.5
(CH2), 29.8 (CH2), 29.7 (CH2), 29.7 (CH2), 29.7 (CH2), 29.7 (CH2),
29.6 (CH2), 29.6 (CH2), 29.5 (CH2), 29.5 (CH2), 29.5 (CH2), 29.4
(CH2), 29.4 (CH2), 29.4 (CH2), 29.3 (CH2), 26.3 (CH2), 26.2 (CH2),
25.8 (CH2), 22.7 (CH2), 22.6 (CH2), 21.3 (CH3), 21.2 (CH3), 20.4
(CH2), 14.0 (CH3), 13.9 (CH3), 13.8 (CH3). MS (MALDI) m/e
2712.7 (MH+), 2585.7 (MH+ - 127).
Compound 11. Purified by column chromatography (SiO2, CH2-
Cl2, then CH2Cl2/EtOAc 1:1). Yield: 67%. Yellow solid. 1H NMR
(CDCl3, 500 MHz) δ: 0.92 (t, 3H, J ) 7.0 Hz), 0.98 (t, 6H, J )
7.5 Hz), 1.28 (t, 6H, J ) 7.0 Hz), 1.30-1.40 (m, 8H), 1.48 (m,
2H), 1.59 (m, 4H), 1.79 (m, 2H), 2.38 (s, 3H), 3.19 (d, 2H, J )
21.5 Hz), 3.31 (broad t, 4H, J ) 7.5 Hz), 3.85 (s, 3H), 3.99 (t, 2H,
J ) 6.5 Hz), 4.05 (m, 4H), 6.66 (A of ABq, 2H, J ) 7.5 Hz), 6.92
(A of ABq, 2H, J ) 9.0 Hz), 6.94 (A of ABq, 2H, J ) 9.0 Hz),
7.03 (A of ABq, 1H, J ) 16.5 Hz),), 7.04 (A of ABq, 1H, J ) 16.5
Hz), 7.10-7.35 (m, 14H), 7.42-7.54 (m, 21H). 13C NMR (CDCl3,
125 MHz) δ: 159.4, 159.0, 147.9, 139.0, 138.4, 138.3, 138.1, 138.0,
137.8, 137.7, 137.5, 135.9, 134.6, 131.2, 131.1, 130.2, 130.1, 130.1,
129.8, 129.4, 129.3, 129.1, 128.9, 128.8, 128.7, 128.6 128.5, 128.3,
128.1, 127.9, 127.8, 127.8, 127.6, 127.0, 126.9, 126.8, 126.7, 126.7,
126.7, 126.5, 126.3, 126.1, 124.3, 124.1, 124.0, 123.9, 123.7, 123.7,
123.4, 123.4 123.2, 122.8, 114.7, 114.2, 111.6, 68.1 (OCH2), 62.2
(d, J ) 6.8 Hz), 55.3, 50.8, 33.6 (d, J ) 137.5 Hz), 31.6, 29.5,
29.2, 25.7, 22.6, 21.3, 20.3, 16.4 (d, J ) 6.0 Hz), 14.0, 14.0. 31P
NMR (CDCl3, 162 MHz) δ: 26.8. MS (MALDI) m/e 1215.0
(MH+).
Compound 7a. Purified by column chromatography (SiO2,
hexanes/CH2Cl2, 1:1, then CH2Cl2). Yield: 92%. Yellow solid. 1H
NMR (CDCl3, 500 MHz) δ: 0.92 (t, 3H, J ) 7.0 Hz), 0.97 (t, 6H,
J ) 7.0 Hz), 1.30-1.40 (m, 6H), 1.45 (m, 2H), 1.58 (m, 4H), 1.77
(m, 2H), 2.35 (s, 3H), 3.28 (t, 4H, J ) 7.5 Hz), 3.79 (s, 3H), 3.92
(t, 2H, J ) 7.0 Hz), 6.62 (A of ABq, 2H, J ) 9.0 Hz), 6.82-6.92
(m, 7H), 6.99-7.17 (m, 11H), 7.36-7.45 (m, 14H), 7.73 (br s,
1H), 7.79 (br s, 2H), 9.96 (s, 1H). 13C NMR and DEPT (CDCl3,
125 MHz) δ: 192.2 (CH), 159.3 (C), 159.0 (C), 147.9 (C), 138.9
(C), 138.5 (C), 138.4 (C), 138.3 (C), 138.2 (C), 138.0 (C), 137.5
(C), 137.1 (C), 137.0 (C), 134.4 (C), 130.4 (CH), 130.2 (CH), 130.1
(CH), 129.9 (C), 129.7 (C), 129.4 (CH), 128.8 (CH), 128.7 (CH),
128.6 (CH), 127.9 (CH), 127.8 (CH), 127.8 (CH), 127.4 (CH), 127.1
(CH), 126.9 (CH), 126.5 (CH), 126.4 (CH), 126.2 (CH), 126.1 (CH),
125.9 (CH), 124.2 (C), 124.0 (CH), 123.9 (CH), 123.4 (CH), 123.0
(CH), 122.8 (CH), 114.7 (CH), 114.1 (CH), 111.6 (CH), 68.0 (CH2),
55.2 (CH3), 50.7 (CH2), 31.6 (CH2), 29.5 (CH2), 29.2 (CH2), 25.7
(CH2), 22.6 (CH2), 21.2 (CH3), 20.3 (CH2), 14.0 (CH3), 14.0 (CH3).
IR ν: 1697 (CdO) cm-1. MS (MALDI) m/e 990.5 (MH+). HRMS,
m/e calcd for C71H75NO3 989.5746; found 989.5738.
Compound 12. Purified by column chromatography (SiO2,
hexanes/CH2Cl2, 1:1, then CH2Cl2). Yield: 90%. Yellow solid. 1H
NMR (CDCl3, 72 °C, 500 MHz) δ: 0.85-0.93 (m, 15H), 0.96 (t,
6H, J ) 7.5 Hz), 1.20-1.40 (m, 66H), 1.49 (m, 12H), 1.61 (m,
6H), 1.72-1.85 (m, 12H), 2.35 (s, 6H), 2.36 (s, 3H), 2.98 (s, 6H),
3.30 (t, 4H, J ) 7.0 Hz), 3.82 (s, 3H), 3.97-4.01 (m, 4H), 4.04 (t,
6H, J ) 7.0 Hz), 6.74-6.76 (A of ABq and s, 6H), 6.89-7.23 (m,
39H), 7.42-7.61 (m, 34H). 13C NMR (CDCl3, 125 MHz) δ: 159.3,
159.0, 153.3, 150.1, 147.9, 138.4, 138.3, 138.2, 138.1, 138.0, 137.9,
137.7, 137.7, 137.2, 136.7, 134.6, 132.5, 130.1, 129.8, 129.8, 129.5,
129.4, 129.3, 128.9, 128.8, 128.7, 128.6, 128.5, 128.5, 128.3, 128.0,
127.9, 127.8, 127.7, 127.5, 127.0, 126.5, 126.3, 126.1, 126.1, 126.1,
124.5, 124.2, 123.9, 123.7, 123.6, 123.5, 123.4, 123.0, 114.7, 114.2,
112.5, 111.6, 105.2, 73.5, 69.1, 68.1, 55.3, 50.8, 40.5, 32.0, 31.9,
31.6, 30.4, 29.8, 29.7, 29.7, 29.6, 29.6, 29.5, 29.5, 29.4, 29.4, 29.3,
29.3, 26.2, 26.1, 25.7, 22.7, 22.6, 21.4, 21.3, 20.3, 14.1, 14.1, 14.0.
MS (MALDI) m/e 2586.9 (MH+).
Compound 8. Purified by column chromatography (SiO2, CH2-
Cl2, then CH2Cl2/EtOAc 1:1). Yield: 84%. Yellow solid. 1H NMR
(CDCl3, 500 MHz) δ: 0.92 (t, 3H, J ) 7.0 Hz), 0.97 (t, 6H, J )
7.5 Hz), 1.28 (t, 6H, J ) 7.0 Hz), 1.30-1.40 (m, 6H), 1.46 (m,
2H), 1.59 (m, 4H), 1.78 (m, 2H), 2.37 (s, 3H), 3.06 (d, 2H, J )
21.5 Hz), 3.29 (t, 4H, J ) 7.5 Hz), 3.82 (s, 3H), 3.92 (t, 2H, J )
7.0 Hz), 4.06 (m, 4H), 6.64 (A of ABq, 2H, J ) 8.5 Hz), 6.86-
7.20 (m, 20H), 7.40-7.52 (m, 18H), 7.57 (br s, 1H), 7.77 (br s,
1H). 13C NMR (CDCl3, 125 MHz) δ: 159.3, 159.0, 147.9, 139.5
(d, J ) 2.8 Hz), 139.0, 138.3, 138.2, 138.1, 138.0, 138.0, 137.6,
137.5 (d, J ) 3.1 Hz), 137.3, 134.5, 134.2 (d, J ) 8.7 Hz), 133.8,
130.0, 129.9, 129.8, 129.4, 129.4, 129.3, 129.1, 128.8, 128.7, 128.6,
128.3, 128.2, 127.9, 127.8, 127.8, 127.6, 127.5 (d, J ) 6.4 Hz),
127.1, 126.5, 126.3, 126.1, 124.5, 124.3, 124.1, 124.0, 123.8, 123.7,
123.3, 123.2, 122.8, 114.7, 114.1, 111.6, 94.7 (d, J ) 3.5 Hz), 68.0,
62.3 (d, J ) 6.9 Hz), 55.3, 50.7, 33.2 (d, J ) 137.0 Hz), 31.6,
29.5, 29.2, 25.7, 22.6, 21.3, 20.3, 16.4 (d, J ) 6.0 Hz), 14.0, 14.0.
31P NMR (CDCl3, 162 MHz) δ: 26.1. MS (MALDI) m/e 1340.9
(MH+), 1213.9 (MH+ - 127).
Compound 9. Purified by column chromatography (SiO2,
hexanes/CH2Cl2 1:1, then CH2Cl2). Yield: 92%. Yellow solid. 1H
NMR (CDCl3, 72 °C, 500 MHz) δ: 0.85-0.91 (m, 15H), 0.94 (t,
6H, J ) 7.5 Hz), 1.20-1.38 (m, 72H, J ) 7.5 Hz), 1.40-1.50 (m,
10H), 1.58 (m, 4H), 1.72-1.82 (m, 10H), 2.31 (s, 6H), 2.32 (s,
3H), 2.93 (s, 6H), 3.26 (t, 4H, J ) 7.5 Hz), 3.77 (s, 3H), 3.93 (t,
4H, J ) 7.0 Hz), 3.96-4.02 (m, 6H), 6.69-6.72 (m including s
and A of ABq, 6H, J ) 8.5 Hz), 6.84-7.21 (m, 39H), 7.37-7.58
(m, 31H), 7.75 (s, 2H). 13C NMR and DEPT (CDCl3, 72 °C, 125
MHz) δ: 159.7 (C), 159.3 (C), 159.3 (C), 153.6 (C), 150.4 (C),
148.1 (C), 139.8 (C), 139.8 (C), 139.3 (C), 139.2 (C), 138.7 (C),
Acknowledgment. Financial support from the Spanish
Ministerio de Educacio´n y Ciencia (NAN2004-08843-C05-02)
and the Junta de Comunidades de Castilla-La Mancha (PAI-
05-022) is gratefully acknowledged. J.T. and C.R.-N. also
acknowledge the receipt of predoctoral fellowships from the
Ministerio de Educacio´n y Ciencia (Spain) and Junta de
Comunidades de Castilla-La Mancha, respectively.
Supporting Information Available: Compound characterization
data and copies of 1H NMR and 13C NMR spectra for all
compounds. This material is available free of charge via the Internet
at http://pubs.acs.org.
JO070210V
3852 J. Org. Chem., Vol. 72, No. 10, 2007