A stable fullerene-azide building block for the construction of a fullerene-porphyrin conjugate

Article abstract of DOI:10.1016/j.tetlet.2009.02.185

A stable C₆₀ derivative bearing an azide functional group was prepared and used as a building block under the copper-mediated Huisgen 1,3-dipolar cycloaddition conditions for the preparation of a fullerene-porphyrin conjugate.

Full text of DOI:10.1016/j.tetlet.2009.02.185

Tetrahedron Letters 50 (2009) 2245–2248
Contents lists available at ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
A stable fullerene-azide building block for the construction
of a fullerene–porphyrin conjugate
Julien Iehl a, Iwona Osinska b, Rémy Louis b, Michel Holler a, Jean-François Nierengarten a,
*
a Laboratoire de Chimie des Matériaux Moléculaires, CNRS et Université de Strasbourg, Ecole Européenne de Chimie, Polymères et Matériaux, 25 rue Becquerel, 67087
Strasbourg Cedex 2, France
b Groupe de Radiocristallographie, Institut de Chimie, CNRS et Université de Strasbourg, 1 rue Blaise Pascal, BP 296 R8, 67008 Strasbourg Cedex, France
a r t i c l e i n f o
a b s t r a c t
Article history:
A stable C60 derivative bearing an azide functional group was prepared and used as a building block under
the copper-mediated Huisgen 1,3-dipolar cycloaddition conditions for the preparation of a fullerene–por-
phyrin conjugate.
Received 23 January 2009
Accepted 24 February 2009
Available online 28 February 2009
Ó 2009 Elsevier Ltd. All rights reserved.
Keywords:
Fullerene
Porphyrin
Cycloaddition
Azide
Alkyne
The synthetic appeal of click reactions relies upon their toler-
ance of water and oxygen, simple reaction conditions, and high
yield.1 The copper-mediated Huisgen 1,3-dipolar cycloaddition of
organic azides and alkynes leading to 1,2,3-triazoles is without
any doubt the most useful member of this family of reactions.2 It
quickly found applications in chemistry, biology, and materials sci-
ence.3 As part of this research, we have recently shown that this
click reaction is an interesting tool for the functionalization of ful-
lerene building blocks.4 In general, the reactivity of C60 toward
azides5 is not significantly competing with the cycloaddition lead-
ing to the desired 1,2,3-triazole derivatives and good yields can be
obtained when fullerene derivatives with reasonable solubility are
used as starting materials.4,6 Whereas fullerene alkyne building
blocks are easy to produce, the preparation of fullerene azide
derivatives is difficult due to their fast decomposition resulting
from intermolecular cycloaddition reactions between the C60 and
the azide groups.4 We could however develop a fullerene bis-
adduct (1) that was reasonably stable.4 Indeed, upon preparation
and purification, compound 1 must be used for the click reactions
within the next couple of hours to obtain good yields. Therefore,
the availability of this synthetic intermediate is quite limited and
the preparation of a stable fullerene azide derivative remains a
challenge. In this Letter, we report the synthesis of such a com-
pound as well as its subsequent grafting onto a porphyrin core un-
der the copper-mediated Huisgen 1,3-dipolar cycloaddition
conditions. Indeed, porphyrins and fullerenes are interesting com-
plementary building blocks for the preparation of artificial photo-
synthetic systems as photoinduced electron transfer is usually
evidenced in fullerene–porphyrin conjugates.7,8
O
O
O
O
O
O
O
O
N3
N3
1
In the design of C60 derivative 8 (Scheme 1), we have decided to
take advantage of the encapsulation of the fullerene sphere in a
cyclic addend surrounded by two 3,5-didodecylbenzyl ester moie-
ties;9 the azide function being attached onto the bridging subunit.
In this way, steric hindrance should prevent the reaction of the
azide group with the C60 core and, thus, provide a stable com-
pound. The synthesis of building block 8 is depicted in Scheme 1.
Alkylation of phenol 29 with tosylate 310 afforded 4 in a moderate
yield (33%). Subsequent treatment of 4 with tetra-n-butylammo-
nium fluoride (TBAF) gave diol 5 in 73% yield. The reaction of
5 with acid 6 and N,N0-dicyclohexylcarbodiimide (DCC) in the pres-
ence of 4-dimethylaminopyridine (DMAP) and 1-hydroxy-benzo-
triazole (HOBt) gave bis-malonate 7 in 65% yield. Fullerene
derivative 8 was then prepared under the reaction conditions
* Corresponding author. Tel.: +33 390 242764; fax: +33 390 242774.
E-mail address: nierengarten@chimie.u-strasbg.fr (J.-F. Nierengarten).
0040-4039/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tetlet.2009.02.185

2246
J. Iehl et al. / Tetrahedron Letters 50 (2009) 2245–2248
RO
RO
TIPS
N3
CHO
O
O
O
OH
TsO
N3
6
OH
O
3
TIPS
N
M
N
10
(i)
(iii)
(i)
(iii)
+
N
N
TBDMSO
OTBDMS
RO
OR
2
4
R = TBDMS
(ii)
O
N3
N3
O
5 R = H
12
M = H2
TIPS
H
NH HN
11
(ii)
13M = Zn
O
O
N
N
N
Ph
(iv)
O
O
O
O
O
O
O
O
O
O
N
N
(iv)
O
O
O
O
N
Zn
N
N
N
Zn
N
N
OR
RO
N
RO
OR
RO
OR
OR
RO
Ph
Ph
H25
8 R = C12
N
7 R = C12H25
N
14
15
H
N
N
N
Scheme 2. Reagents and conditions: (i) BF3ꢀEt2O, CHCl3, rt, 16 h, then p-chloranil,
2 h (23%); (ii) Zn(OAc)2, MeOH/CHCl3, , 2 h (95%); (iii) TBAF, THF, 0 °C, 2 h (94%);
(iv) benzyl azide, CuSO4ꢀ5H2O, sodium ascorbate, CH2Cl2/H2O, rt, 12 h (63%).
D,
D
O
(v)
O
O
O
O
O
the preparation of a porphyrin-fullerene conjugate. For this pur-
pose, we have developed a porphyrin building block bearing two
terminal alkyne units. The synthesis of this compound is depicted
in Scheme 2.
O
O
O
OR
RO
RO
OR
Compounds 1016 and 1117 were prepared according to previ-
ously reported methods. The condensation of 10 and 11 was per-
formed in CHCl3 (commercial CHCl3 containing 0.75% ethanol as
stabilizer) in the presence of BF3ꢀEt2O.17 After 16 h, p-chloranil (tet-
rachlorobenzoquinone) was added to irreversibly convert the por-
phyrinogen to the porphyrin. The desired tetraphenylporphyrin 12
was subsequently isolated in 23% yield. Metalation of porphyrin 12
with Zn(OAc)2 afforded 13 in 95% yield which after treatment with
TBAF gave terminal alkyne 14 as a crystalline purple solid. Crystals
suitable for X-ray crystal-structure analysis were obtained by slow
diffusion of hexane into a CHCl3 solution of 14 (Fig. 1).18
H25
9 R = C12
Scheme 1. Reagents and conditions: (i) K2CO3, LiBr, DMF, 80 °C, 96 h (33%);
(ii) TBAF, THF, 0 °C, 3 h (73%); (iii) DCC, DMAP, HOBt, CH2Cl2, 0 °C to rt, 72 h (65%);
(iv) C60, DBU, I2, PhMe, rt, 12 h (56%); (v) phenylacetylene, CuSO4ꢀ5H2O, sodium
ascorbate, CH2Cl2/H2O, rt, 16 h (73%).
developed by Diederich and co-workers,11 which led to macro-
cyclic bis-adducts of C60 by a regioselective cyclization reaction
at the carbon sphere with bis-malonate derivatives in a double Bin-
gel12 cyclopropanation. Reaction of 7 with C60, I2, and 1,8-diazabi-
cyclo[5.4.0]undec-7-ene (DBU) in toluene at room temperature
afforded the desired cyclization product 8 in 56% yield. The relative
position of the two cyclopropane rings in 8 on the C60 core was
determined based on the molecular symmetry (Cs) deduced from
the 1H and 13C NMR spectra.13 It is also well established that the
1,3-phenylenebis(methylene)-tethered bis-malonates produce
regioselectively the Cs symmetrical cis-2 addition pattern at
14
C60
.
Importantly, fullerene azide derivative 8 was found to be a
stable compound under normal laboratory conditions. A sample
was stored in the refrigerator for several months without any
detectable decomposition. The reaction conditions for the 1,3-
dipolar cycloaddition of compound 8 with terminal alkynes were
first adjusted with phenylacetylene (Scheme 1). Under optimized
conditions, a mixture of 8 (1 equiv), phenylacetylene (2 equiv), Cu-
SO4ꢀ5H2O (0.1 equiv), and sodium ascorbate (0.3 equiv) in CH2Cl2/
H2O was vigorously stirred at room temperature for 12 h. After
work-up and purification, compound 9 was thus obtained in 73%
yield. The structure of compound 9 was confirmed by its 1H and
13C NMR spectra as well as by mass spectrometry.15 Inspection of
the 1H NMR spectrum clearly indicates the disappearance of the
CH2-azide signal at d 3.55 ppm. Importantly, the 1H NMR spectrum
of 9 shows the typical singlet of the 1,2,3-triazole unit at d
7.80 ppm as well as the signal corresponding to the CH2-triazole
protons at d 4.65 ppm.
Figure 1. ORTEP plot of the structure of 14. Thermal ellipsoids are drawn at the 50%
probability level. The prime (0) characters in the atom labels indicate that these
atoms are at equivalent position. Selected bond lengths and bond angles: Zn(1)–
N(1): 2.030(2) Å; Zn(1)–N(2): 2.034(2) Å; C(21)–C(22): 1.170(4) Å; N(1)–Zn(1)–
N(2): 90.55(8)°; N(1)–Zn(1)–N(20): 89.45(8)°; C(20)–C(21)–C(22): 175.8(3)°.
Having developed a stable fullerene azide building block allow-
ing its further transformation under the copper-mediated Huisgen
1,3-dipolar cycloaddition conditions, we have decided to use it for

J. Iehl et al. / Tetrahedron Letters 50 (2009) 2245–2248
2247
RO
RO
O
O
O
O
O
O
N
N
N
RO
O
O
O
RO
N
Zn
(i)
N
8
N
N
OR
N
N
O
O
O
O
OR
N
O
O
O
O
16R = C12H25
O
OR
OR
Scheme 3. Reagents and conditions: (i) 14, CuSO4ꢀ5H2O, sodium ascorbate, CH2Cl2/
H2O, rt, 1 h (64%).
The absorption spectrum of 16 recorded in CH2Cl2 shows the
characteristic Zn(II)-porphyrin absorptions.17 The Soret band
(423 nm) and the two Q bands (551 and 585 nm) are clearly visi-
ble. Furthermore, the characteristic fullerene cis-2 bis-adduct
absorption profile13 is also distinguishable in the UV region and
the absorption coefficients are consistent with a 2:1 fullerene to
porphyrin ratio. Finally, preliminary luminescence measurements
reveal no emission from the porphyrin moiety in 16 indicating a
strong quenching of its fluorescence by the fullerene subunits
and thus, the occurrence of intramolecular photo-induced pro-
cesses. Detailed photophysical studies are currently under investi-
gation and will be reported in due time.
Figure 2. (A) and (B): views of the structure of 14 highlighting the dihedral angles
between the central porphyrin ring and the phenyl substituents; (C) stacking within
the 14 lattice showing the intermolecular CH–
p interactions of the para-disubsti-
tuted phenyl rings with the neighboring porphyrin moieties; (a) 2.815(3) Å [H(23)–
C(16)]; (b) 2.807(3) Å [H(23)–C(15)] (see Fig. 1 for the numbering).
As shown in Figures 1 and 2, the aromatic porphyrin ring is
nearly perfectly planar. It can also be noted that the central Zn
atom lies on an inversion center. Whereas the two mesityl units
are almost perpendicular to the porphyrin core, a dihedral angle
of ca. 63° is observed for the two other phenyl substituents with
respect to the porphyrin plane. The peculiar orientation of these
aromatic subunits can be explained by close inspection of the
packing. Indeed, this orientation allows the establishment of inter-
Acknowledgments
This work was supported by the CNRS and the University of
Strasbourg. We further thank Dr. L. Brelot for helpful discussions.
molecular CH–p interactions between the para-disubstituted phe-
Supplementary data
nyl rings and the neighboring aromatic porphyrin rings (Fig. 2C).
The packing forces resulting from these interactions also explain
why the angle Zn(1)–C(16)–C(17) deviates from 180°. The ob-
served angle is effectively 173.7°. Furthermore, attractive interac-
tions of the acetylenic protons with the mesityl units of other
neighboring molecules (not shown) explain the slight distortion
of the terminal alkyne group with a value of 175.8(3)° for the
C(20)–C(21)–C(22) angle.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.tetlet.2009.02.185.
References and notes
1. Kolb, H. C.; Finn, M. G.; Sharpless, K. B. Angew. Chem., Int. Ed. 2001, 40,
2004–2021.
The reaction conditions used for the preparation of 9 from phen-
ylacetylene and 8 were then applied to porphyrin 14 and benzyl
azide. The clicked derivative 15 was thus obtained in 63% yield
(Scheme 2). Similarly, treatment of 14 with fullerene azide 8 in the
presence of CuSO4ꢀ5H2O and sodium ascorbate gave the targeted ful-
lerene–porphyrin conjugate 16 in 64% yield (Scheme 3). The 1H and
13C NMR spectra of 16 are in perfect agreement with proposed for-
mulation.19 IR data also revealed that no terminal alkyne
(3294 cmꢁ1) or azide (2092 cmꢁ1) residues remain in the final prod-
uct. The MALDI-TOF mass spectrum confirmed the structure of 16
with a very intense signal at 4898.5 corresponding to the expected
molecular ion peak ([MH]+, calcd for C332H287N10O26Zn: 4898.36).
2. (a) Huisgen, R. Pure Appl. Chem. 1989, 61, 613–628; (b) Huisgen, G.; Szeimies,
W.; Moebius, L. Chem. Ber. 1967, 100, 2494–2507; (c) Rostovtsev, V. V.;
Green, L. G.; Fokin, V. V.; Sharpless, K. B. Angew. Chem., Int. Ed. 2002, 41, 2596–
2599.
3. For selected examples, see: (a) Ornelas, C.; Aranzaes, J. L.; Cloutet, E.; Alves, S.;
Astruc, D. Angew. Chem., Int. Ed. 2007, 46, 872–877; (b) Helms, B.; Mynar, J. L.;
Hawker, C. J.; Fréchet, J. M. J. J. Am. Chem. Soc. 2004, 126, 15020–15021; (c)
Wilkinson, B. L.; Bornaghi, L. F.; Poulsen, S.-A.; Houston, T. A. Tetrahedron 2006,
62, 8115–8125; (d) Lee, B.-Y.; Park, S. R.; Jeon, H. B.; Kim, K. S. Tetrahedron Lett.
2006, 47, 5105–5109; (e) Wu, P.; Feldman, A. K.; Nugent, A. K.; Hawker, C. J.;
Scheel, A.; Voit, B.; Pyun, J.; Fréchet, J. M. J.; Sharpless, K. B.; Fokin, V. V. Angew.
Chem., Int. Ed. 2004, 116, 4018–4022.
4. (a) Iehl, J.; Pereira de Freitas, R.; Nierengarten, J.-F. Tetrahedron Lett. 2008, 49,
4063–4066; (b) Pereira de Freitas, R.; Iehl, J.; Delavaux-Nicot, B.; Nierengarten,
J.-F. Tetrahedron 2008, 64, 11409–11419.

2248
J. Iehl et al. / Tetrahedron Letters 50 (2009) 2245–2248
5. (a) Prato, M.; Li, Q. C.; Wudl, F.; Lucchini, V. J. Am. Chem. Soc. 1993, 115, 1148–
1150; (b) Yamakoshi, Y. N.; Yagami, T.; Sueyoshi, S.; Miyata, N. J. Org. Chem.
1996, 61, 7236–7237; (c) Hawker, C. J. Org. Chem. 1994, 59, 3503–3505; (d)
Yashiro, A.; Nishida, Y.; Ohno, M.; Eguchi, S.; Kobayashi, K. Tetrahedron Lett.
1998, 39, 9031–9034.
6. For other examples of copper mediated Huisgen 1,3-dipolar cycloaddition
reactions from fullerene building blocks, see: (a) Isobe, H.; Cho, K.; Solin, N.;
Werz, D. B.; Seeberger, P. H.; Nakamura, E. Org. Lett. 2007, 9, 4611–4614; (b)
Iehl, J.; Pereira de Freitas, R.; Delavaux-Nicot, B.; Nierengarten, J.-F. Chem.
Commun. 2008, 2450–2452; (c) Zhang, W.-B.; Tu, Y.; Ranjan, R.; Van Horn, R.
M.; Leng, S.; Wang, J.; Polce, M. J.; Wesdemiotis, C.; Quirk, R. P.; Newkome, G.
R.; Cheng, S. Z. D. Macromolecules 2008, 41, 515–517; (d) Mahmud, I. M.; Zhou,
N.; Wang, L.; Zhao, Y. Tetrahedron 2008, 64, 11420–11432.
7. For reviews on fullerene–porphyrin conjugates, see: (a) Guldi, D. M. Chem. Soc.
Rev. 2002, 31, 22–36; (b) Imahori, H.; Sakata, Y. Eur. J. Org. Chem. 1999, 2445–
2457; (c) Gust, D.; Moore, T. A.; Moore, A. L. Acc. Chem. Res. 2001, 34, 40–48; (d)
Imahori, H. J. Phys. Chem. B 2004, 108, 6130–6143; (e) Imahori, H. Org. Biomol.
Chem. 2004, 2, 1425–1433; (f) Nierengarten, J.-F. J. Porphyrins Phthalocyanines
2008, 12, 1022–1029.
8. During the preparation of this manuscript, the synthesis of fullerene–porphyrin
conjugates under the copper mediated Huisgen 1,3-dipolar cycloaddition
conditions has been reported, see: Fazio, M. A.; Lee, O. P.; Schuster, D. I. Org.
Lett. 2008, 10, 4979–4982.
9. This strategy was already used to prevent the fullerene-fullerene interactions
usually observed for amphiphilic C60 derivatives, see: Nierengarten, J.-F.;
Schall, C.; Nicoud, J.-F.; Heinrich, B.; Guillon, D. Tetrahedron Lett. 1998, 39,
5747–5750.
10. Aucagne, V.; Hänni, K. V.; Leigh, D. A.; Lusby, P. J.; Walker, D. B. J. Am. Chem. Soc.
2006, 128, 2186–2187.
11. (a) Nierengarten, J.-F.; Gramlich, V.; Cardullo, F.; Diederich, F. Angew. Chem., Int.
Ed. 1996, 35, 2101–2103; (b) Nierengarten, J.-F.; Habicher, T.; Kessinger, R.;
Cardullo, F.; Diederich, F.; Gramlich, V.; Gisselbrecht, J.-P.; Boudon, C.; Gross,
M. Helv. Chim. Acta 1997, 80, 2238–2276.
158.9, 160.6, 162.7; MALDI-TOF-MS: 2043 ([MH]+, calcd for C139H124N3O13
2042.91).
:
15. Compound 9. IR (neat): 1748 (C@O); 1H NMR (CDCl3, 300 MHz): 0.89 (t, J = 7 Hz,
12H), 1.20–1.45 (m, 72H), 1.72 (m, 8H), 2.48 (m, 2H), 3.85 (t, J = 7 Hz, 8H), 4.06
(t, J = 6 Hz, 2H), 4.65 (t, J = 6 Hz, 2H), 5.04 (d, J = 12 Hz, 2H), 5.29 (AB, J = 12 Hz,
4H), 5.72 (d, J = 12 Hz, 2H), 6.36 (t, J = 2 Hz, 2H), 6.47 (d, J = 2 Hz, 4H), 6.76 (m,
2H), 7.13 (m, 1H), 7.33 (m, 1H), 7.43 (m, 2H), 7.80 (s, 1H), 7.83 (d, J = 8 Hz, 2H);
13C NMR (CDCl3, 75 MHz): 14.3, 22.8, 26.2, 29.4, 29.5, 29.6, 29.7, 29.75, 29.8,
30.1, 32.0, 47.3, 49.2, 64.4, 66.9, 67.3, 68.2, 68.8, 70.7, 101.8, 107.3, 112.5,
115.7, 120.2, 125.8, 128.3, 128.9, 130.6, 134.5, 135.9, 136.2, 136.6, 137.9, 138.5,
140.1, 141.2, 141.3, 142.4, 142.8, 143.3, 143.7, 143.8, 144.1, 144.2, 144.4, 144.7,
145.1, 145.2, 145.3, 145.4, 145.7, 145.8, 146.2, 147.4, 147.5, 147.6, 147.9, 148.7,
158.6, 160.5, 162.7; Anal. Calcd for C147H129N3O13ꢀH2O: C, 81.60; H, 6.10; N,
1.94. Found: C, 81.53; H, 6.11; N, 1.91. MALDI-TOF-MS: 2146 ([M]+, calcd for
C147H139N3O13: 2145.65).
16. Nierengarten, J.-F.; Zhang, S.; Gégout, A.; Urbani, M.; Armaroli, N.; Marconi, G.;
Rio, Y. J. Org. Chem. 2005, 70, 7550–7557.
17. (a) Littler, B. J.; Ciringh, Y.; Lindsey, J. S. J. Org. Chem. 1999, 64, 2864–2872; (b)
Geier, G. R., III; Littler, B. J.; Lindsey, J. S. J. Chem. Soc., Perkin Trans. 2 2001,
701–711.
18. C54H40N4Zn (M = 810.27 g molꢁ1), monoclinic; space group P21/c; a =
13.3374(6) Å; b = 12.1528(9) Å; c = 12.9668(9) Å;
= 90.00°; Z = 2; (Mo K
) = 1.136 mmꢁ1; F(000) = 844; a total of 13,564
reflections collected; 1.57° < h < 27.46°, 4660 independent reflections with
a = 90.00°; b = 103.104(4)°;
c
l
a
3499 having I > 2r
(I); 271 parameters; Final results: R1(F2) = 0.0452;
wR2(F2) = 0.1311, Goof = 1.087. Full data collection parameters and structural
data are available as CIF file (Cambridge Crystallographic Data Centre
deposition number CCDC 717039).
19. Compound 16. IR (neat): 1749 (C@O); UV–vis (CH2Cl2): 258 (341400), 423
(486900), 551 (27900), 585 (14800); 1H NMR (CDCl3, 300 MHz): d 0.88 (t,
J = 7 Hz, 24H), 1.20–1.45 (m, 144H), 1.71 (m, 16H), 1.81 (s, 12 H), 2.60 (m,
10H), 3.82 (t, J = 7 Hz, 16H), 4.12 (m, 4H), 4.80 (m, 4H), 5.11 (d, J = 12 Hz,
4H), 5.26 (AB, J = 12 Hz, 8H), 5.73 (d, J = 12 Hz, 4H), 6.33 (m, 4H), 6.44 (d,
J = 2 Hz, 8H), 6.84 (m, 4H), 7.14 (m, 2H), 7.23 (s, 4H), 8.00 (s, 2H), 8.14 (d,
J = 8 Hz, 4H), 8.28 (d, J = 8 Hz, 4H), 8.75 (d, J = 5 Hz, 4H), 8.90 (d, J = 5 Hz,
4H); 13C NMR (CDCl3, 75 MHz): d 14.0, 21.3, 21.8, 22.85, 26.2, 29.4, 29.5,
29.6, 29.7, 29.8, 29.9, 32.1, 49.37, 64.5, 66.9, 67.2, 68.3, 68.8, 70.7, 101.6,
107.1, 112.1, 115.1, 119.4, 120.0, 121.0, 123.9, 127.7, 129.9, 130.7, 132.2,
134.6, 135.1, 135.7, 135.9, 137.5, 135.6, 138.7, 139.1, 139.2, 139.8, 140.9,
141.6, 142.7, 142.8, 142.9, 143.1, 143.2, 143.9, 144.0, 144.1, 144.2, 144.6,
144.7, 144.8, 144.9, 145.1, 145.3, 145.4, 145.8, 147.1, 147.2, 147.3, 147.6,
148.5, 149.8, 149.9, 158.9, 160.5, 162.5, 162.6; Anal. Calcd for
C332H286N10O26Znꢀ2H2O: C, 80.83; H, 5.92; N, 2.84. Found: C, 80.99;
H, 6.22; N, 2.79. MALDI-TOF-MS: 4898.5 ([MH]+, calcd for C332H287N10
O26Zn: 4898.36).
12. Bingel, C. Chem. Ber. 1993, 126, 1957–1959.
13. Zhang, S.; Rio, Y.; Cardinali, F.; Bourgogne, C.; Gallani, J.-L.; Nierengarten, J.-F. J.
Org. Chem. 2003, 68, 9787–9797. and references cited therein.
14. Compound 8. IR (neat): 2096 (–N3), 1748 (C@O); 1H NMR (CDCl3, 300 MHz):
0.89 (t, J = 7 Hz, 12H), 1.20–1.45 (m, 72H), 1.72 (m, 8H), 2.08 (m, 2H), 3.55 (t,
J = 6 Hz, 2H), 3.85 (t, J = 7 Hz, 8H), 4.09 (t, J = 6 Hz, 2H), 5.04 (d, J = 12 Hz, 2H),
5.29 (AB, J = 12 Hz, 4H), 5.75 (d, J = 12 Hz, 2H), 6.36 (t, J = 2 Hz, 2H), 6.47 (d,
J = 2 Hz, 4H), 6.78 (s, 2H), 7.11 (s, 1H); 13C NMR (CDCl3, 75 MHz): 14.3, 22.8,
26.3, 28.9, 29.4, 29.5, 29.6, 29.8, 29.85, 29.9, 31.1, 31.6, 32.1, 48.3, 49.2, 64.8,
67.0, 67.4, 68.3, 68.8, 70.7, 101.8, 107.3, 112.6, 115.6, 134.6, 135.9, 136.3, 136.7,
138.0, 138.4, 140.2, 141.2, 141.3, 142.5, 142.9, 143.3, 143.7, 143.9, 144.1, 144.3,
144.5, 144.7, 145.1, 145.2, 145.3, 145.5, 145.7, 145.9, 146.2, 147.5, 147.6, 148.8,