An efficient synthesis of quaterrylenedicarboximide NIR dyes

Article abstract of DOI:10.1021/jo702019p

(Chemical Equation Presented) Quaterrylenedicarboximides were prepared from 9-bromoperylene-3,4-dicarboximides by palladium-catalyzed coupling with 3-perylene boronic ester, followed by oxidative cyclodehydrogenation of the resulting perylene-perylenedica

Full text of DOI:10.1021/jo702019p

An Efficient Synthesis of
Quaterrylenedicarboximide NIR Dyes
Yuri Avlasevich and Klaus Mu¨llen*
Max Planck Institute for Polymer Research, Ackermannweg 10,
D-55128 Mainz, Germany
muellen@mpip-mainz.mpg.de
ReceiVed September 14, 2007
FIGURE 1. Rylenebis(dicarboximides) 1 and rylenedicarboximides
2-4.
and then base-induced cyclodehydrogenation of the precursors
into penta- and hexarylenebis(dicarboximides) 1d-e.5 This two-
step approach required compounds 2 and 3 as synthetic building
blocks. Perylenedicarboximides 2 (PMIs, λmax ) 520 nm), which
are easily available by the imidization-decarboxylation route,6
are useful as highly fluorescent orange dyes7 and precursors
for the synthesis of other dyes.2,3,5,8 A multistep route to
terrylenedicarboximide 3 (λmax ) 643 nm) was recently
described and used for the synthesis of higher rylenes only.5
Although the formation of a quaterrylenedicarboximide-
perylenedicarboximide dyad was previously reported during the
synthesis of 1e,5 the isolation and characterization of the higher
homologue of 2 and 3, quaterrylenedicarboximide 4 (QMI), until
now has not been described. The synthesis of 4 as a dye, which
is expected to have an intense absorption in the NIR region
and be useful as a synthetic building block for the synthesis of
higher rylene dyes (due to the free peri-positions) seems to be
an important target in modern dyestuff chemistry.
Quaterrylenedicarboximides were prepared from 9-bromo-
perylene-3,4-dicarboximides by palladium-catalyzed coupling
with 3-perylene boronic ester, followed by oxidative cyclo-
dehydrogenation of the resulting perylene-perylenedicar-
boximide dyads with iron(III) chloride. The quaterrylenedi-
carboximides, described here, are highly photochemically and
thermally stable dyes, which may be useful as green NIR
dyes (λmax ) 735 nm) and as building blocks for the synthesis
of higher rylene dyes.
In this Note, we present a facile synthetic route to QMIs
having the general formula 4 and an absorption maxima at 735-
740 nm starting from PMI and perylene. The key units in our
synthetic approach (Scheme 1) are perylene derivatives 2 and
6, which are functionalized on one side only. The preparation
of PMI derivatives 2 was achieved by known procedures.5,9
3-Bromoperylene was obtained in 92% yield by NBS bromi-
Rylenebis(dicarboximide)s, 1 (Figure 1), are photochemically
and thermally stable dyes which absorb in the visible (n ) 0,
1) and the near-infrared ranges (n ) 2-4). Whereas perylenebis-
(dicarboximide)s (n ) 0, λmax ) 524 nm) with a variety of
applications1 are well-described, the syntheses of terrylene- (n
) 1, λmax ) 660 nm)2 and quaterrylenebis(dicarboximide)s3,4
(n ) 2, λmax ) 760 nm) have been reported only in the past
decade. The syntheses of 1a-c have been achieved by direct
base-induced homo-4 or heterocoupling2,3 of naphthalene- and
perylenedicarboximides 2, which contain only one imide group
in the molecule as compared to rylenebis(dicarboximides) 1.
The synthesis of higher homologues required initial coupling
of perylene- and terrylenedicarboximides with a single bond
(2) (a) Hortrup, F. O.; Mu¨ller, G. R. J.; Quante, H.; de Feyter, S.; de
Schryver, F. C.; Mu¨llen, K. Chem.sEur. J. 1997, 3, 219-225. (b) Nolde,
F; Qu, J.; Kohl, C.; Pschirer, N. G.; Reuther, E.; Mu¨llen, K. Chem.sEur.
J. 2005, 11, 3959-3967.
(3) (a) Quante, H.; Mu¨llen, K. Angew. Chem., Int. Ed. Engl. 1995, 34,
1323-1325. (b) Geerts, Y.; Quante, H.; Platz, H.; Mahrt, R.; Hopmeier,
M.; Bo¨hm, A.; Mu¨llen, K. J. Mater. Chem. 1998, 8, 2357-2369. (c)
Langhals, H.; Bu¨ttner, J.; Blanke, P. Synthesis 2005, 364-366.
(4) Langhals, H.; Schoenmann, G.; Feiler, L. Tetrahedron Lett. 1995,
36, 6423-6424.
(5) Pschirer, N. G.; Kohl, C.; Nolde, F.; Qu, J.; Mu¨llen, K. Angew. Chem.
2006, 118, 1429-1432; Angew. Chem., Int. Ed. 2006, 45, 1401-1404.
(6) Nagao, Y.; Misono, T. Bull. Chem. Soc. Jpn. 1981, 54, 1191-1198.
(7) (a) Weil, T.; Wiesler, U. M.; Herrmann, A.; Bauer, R; Hofkens, J.;
De Schryver, F. C.; Mu¨llen, K. J. Am. Chem. Soc. 2001, 123, 2388-2395.
(b) Gensch, T.; Hofkens, J.; Herrmann, A.; Tsud, K.; Verheijen, W.; Vosch,
T.; Christ, T.; Basche, T.; Mu¨llen, K.; De Schryver, F. C. Angew. Chem.
1999, 111, 3970-3974; Angew. Chem., Int. Ed. 1999, 38, 3752-3756.
(8) (a) Kohl, C.; Becker, S.; Mu¨llen, K. Chem. Commun. 2002, 2778-
2779. (b) Mu¨ller, S.; Mu¨llen, K. Chem. Commum. 2005, 4045-4046. (c)
Avlasevich, Yu.; Mu¨llen, K. Chem. Commun. 2006, 4440-4442.
(1) (a) Bhosale, Sh.; Sisson, A. L.; Talukdar, P.; Fuerstenberg, A.; Banerji,
N.; Vauthey, E.; Bollot, G.; Mareda, J.; Roeger, C.; Wuerthner, F.; Sakai,
N.; Matile, S. Science 2006, 313, 84-86. (b) Sinks, L. E.; Rybtchinski, B.;
Iimura, M.; Jones, B. A.; Goshe, A. J.; Zuo, X. B.; Tiede, D. M.; Li. X. Y.;
Wasielewski, M. R. Chem. Mater. 2005, 17, 6295-6303. (c) Sautter, A.;
Kaletas, B. K.; Schmid, D. G.; Dobrawa, R.; Zimine, M.; Jung, G.; Van
Stokkum, I. H. M.; De Cola, L.; Williams, R. M.; Wu¨rthner, F. J. Am.
Chem. Soc. 2005, 127, 6719-2729. (d) Segura, J. L.; Gomez, R.; Blanco,
Reinold; R. E.; Ba¨uerle, P. Chem. Mater. 2006, 18, 2834-2847. (e) Cremer,
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10.1021/jo702019p CCC: $37.00 © 2007 American Chemical Society
Published on Web 11/29/2007
J. Org. Chem. 2007, 72, 10243-10246
10243

SCHEME 1a
SCHEME 2a
a Conditions: (i) B2(pin)2, dioxane, KOAc, 70 °C, 15 h, 91%; (ii)
Pd(PPh3)4, aq K2CO3, toluene, 95 °C, 15 h, 72% (a), 81% (b); (iii) FeCl3/
MeNO2, CH2Cl2, 25 °C, 24 h, 80% (a), 54% (b).
a Conditions: (i) Pd(PPh3)4, aq K2CO3, toluene, 70 °C, 6 h, 69%; (ii)
FeCl3/MeNO2, CH2Cl2, 25 °C, 24 h, 60%.
nation of perylene in DMF.10,11 For the synthesis of perylene-
PMI dyads, active boronic esters of PMI were initially consid-
ered.5,9 However, the chromatographic purification of these
esters on silica gel was plagued by the sticking of the product
on the column, and low yields were consequently obtained.
However, conversion of 3-bromoperylene 5 into the previously
unknown boronic ester 6 circumvented this problem, and the
product could be isolated in 91% yield.
The preparation of perylene-PMI dyads 7a,b was achieved
by palladium-catalyzed Suzuki cross-coupling of 9-bromoPMI
derivatives 2a,b with perylene boronic ester 6. After the
chromatographic purification, the dyads 7a,b were isolated as
dark red solids in high yields (60-80%). The next step was
the oxidative cyclodehydrogenation of dyads 7a,b into the target
QMI molecules 4a,b. The known method for conversion of
bisPMI precursors into 1c uses base-assisted cyclodehydroge-
nation (molten KOH/glucose, K2CO3/ethanolamine, t-BuOK/
DBN), which requires the presence of strong electron-
withdrawing groups on both parts of the precursor.2,3,5 However,
dyads 7a,b only contain such groups in the PMI component.
Therefore, other conditions for the cyclodehydrogenation had
to be used.
Cationic cyclodehydrogenation of 7 with aluminum chloride,
which had previously been applied successfully for terrylene
synthesis,12 afforded a green product in which the desired bond
had been formed. However, MALDI-TOF mass spectrometry
revealed that it was a mixture of QMIs containing significant
amounts of chlorinated and dealkylated derivatives. Therefore,
milder conditions for the cyclodehydrogenation had to be
employed to avoid side reactions. Iron(III) chloride is known
as a mild oxidizing agent for the cyclodehydrogenation of
hexaphenylbenzenes to hexabenzocoronenes.13 Recently, this
reagent was successfully applied for the preparation of novel
perylene chromophores from substituted acenaphthenes14 and
for the fusion of poly(perylene) to poly(quaterrylene).15 Cyclo-
dehydrogenation of 7 with an 8-10-fold excess of FeCl3 led to
the formation of the desired QMI chromophores 4a,b in good
yields (55-80%).
The synthesis of monobromoQMI required another approach
(Scheme 2). Since the selective bromination of 4a,b is a
challenge, the active boronic ester of PMI 2c was allowed to
react with an excess of 3,9(10)-dibromoperylene11 8 under mild
conditions to give dyad 7c. Both the starting dibromoperylene
8 and dyad 7c consist of a mixture of two regioisomers that are
not separable by column chromatography. This is no conse-
quence because cyclodehydrogenation of each isomer affords
the same product, namely, 13-bromoQMI 4c. Fortunately, this
reaction was not accompanied by halogen exchange. The
regioselective synthesis of monofunctional dye 4c, which
contains a bromide in a free peri-position, not only provides an
opportunity to use this dye as NIR label but also to tune the
electronic properties via the introduction of donor or acceptor
groups or to generate even larger chromophoric systems.
QMIs 4a-c possess different solubilities depending on their
substituents. Compound 4a is only slightly soluble in organic
solvents at room temperature and is better regarded as a pigment
than a dye. The introduction of bulky tert-octylphenoxy groups
into the bay region of starting PMI 2b enhanced the solubility
of 4b as compared to 4a. However, the presence of the planar,
highly hydrophobic part of the molecule leads to aggregation
in solution. This was confirmed by NMR spectroscopy since
the signals of quaterrylene protons appeared as broad peaks at
room and even at higher temperatures (up to 400 K). Only by
using a dilute solution (1 mg/mL) in 1,3,5-trichlorobenzene-d3
at 443 K allowed for the observation of narrow resonance
signals. A full assignment of the signals was achieved using a
1H-1H COSY experiment.
The absorption spectrum of dyad 7b (Figure 2) consists of
distinct perylene and PMI parts, which are bathochromically
shifted compared to their parent chromophores due to π-con-
jugation. When the dyad was excited at 418 nm (perylene
absorption only), PMI emission (λmax ) 604 nm) was observed.
(9) Weil, T.; Reuther, E.; Beer, C.; Mu¨llen, K. Chem.sEur. J. 2004,
10, 1398-1414.
(10) Mitchell, R. H.; Lai, Y.-H.; Williams, R. V. J. Org. Chem. 1979,
44, 4733-4735.
(11) Schlichting, P.; Rohr, U.; Mu¨llen, K. Liebigs Ann. 1997, 395-407.
(12) Avlasevich, Yu.; Kohl, C.; Mu¨llen, K. J. Mater. Chem. 2006, 16,
1053-1057.
(14) Wehmeier, M.; Wagner, M.; Mu¨llen, K. Chem.sEur. J. 2001, 7,
2197-2205.
(15) Former, C.; Becker, S.; Grimsdale, A. C.; Mu¨llen, K. Macromol-
ecules 2002, 35, 1576-1582.
(13) Iyer, V. S.; Wehmeier, M.; Brand, J. D.; Keegstra, M. A.; Mu¨llen,
K. Angew. Chem. 1997, 109, 1676-1682; Angew. Chem., Int. Ed. Engl.
1997, 36, 1604-1607.
10244 J. Org. Chem., Vol. 72, No. 26, 2007

18 h of irradiation. Thus, the QMI chromophore shows slightly
lower photostability than perylenebis(dicarboximide)s 1a, which
are known for their excellent photostabilities.17 The presence
of free active peri-positions in QMI dyes, which can be
susceptible to photooxidation, may explain this decrease of the
photostability. According to thermogravimetric analysis, com-
pound 4b is thermally stable up to 380 °C. Such a high thermal
stability is important for its practical applications, such as
blending with thermoplastics during processing.
The synthesis and spectroscopic data for new NIR chro-
mophores, quaterrylenedicarboximides, are described. Depend-
ing on its structure, the new chromophore 4 may be a pigment
(4a) or a soluble dye (4b) that is expected to have a wide range
of applications. These dyes display narrow absorption peaks in
the range of 730-740 nm and weak fluorescence in solutions
with an emission at 814 nm. The incorporation of a bromide
into the free peri-position offers the possibility of using the dye
4c as NIR labels, as in spectroscopic optical coherence tomog-
raphy, where a sharp absorption at 740 nm is required.18
Moreover, one can envision the potential application of 4c as a
synthetic precursor for the synthesis of new core-extended rylene
dyes, like 1 (n ) 5, 6).
FIGURE 2. Normalized spectra of perylene 6 (yellow), solid line )
absorption, dashed line ) emission (λexc ) 450 nm); PMI-perylene
dyad 7b (red), solid line ) absorption, dashed line ) emission (λexc
418 nm). Solvent ) toluene.
)
Experimental Section
General: The solvents and chemicals used were of commercial
grade. Compounds 2a-c were synthesized as described else-
where.5,9 Column chromatography was performed on silica gel
(Silicagel 60A, 0.06-0.2 mm, Acros). Melting points were
performed on a Bu¨chi MP B-545 melting point apparatus and are
not corrected. Thermal gravimetric analyses were performed using
Mettler TGA851e apparatus. 1H and 13C NMR spectra were
recorded on Bruker DPX250, Bruker AMX300, Bruker DRX500,
and Bruker WS700 spectrometers. Infrared spectra were obtained
on a Nicolet FTIR320. FD mass spectra were recorded with a VG
Instruments ZAB 2-SE-FPD instrument. MALDI-TOF mass spectra
were recorded on a Bruker Reflex II-TOF spectrometer. UV/vis
spectra were recorded on a Perkin-Elmer Lambda 900 spectropho-
tometer. Fluorescence spectra were recorded on a Spex Fluorolog
3 spectrometer. Fluorescence quantum yield of compound 4b was
determined by the relative method using Rhodamine 800 as a
reference (φF ) 39% in dichloroethane19). Elemental analyses were
performed on a Foss Heraeus Vario EL in the Institute for Organic
Chemistry at the University of Mainz.
3-(4,4,5,5-Tetramethyl-1,3-dioxa-2-borolan-2-yl)perylene (6).
A mixture of 3-bromoperylene (0.99 g, 3 mmol), bis(pinacolato)-
diboron (1.14 g, 4.5 mmol), Pd(dppf)2Cl2 (90 mg, 0.1 mmol), and
1,4-dioxane (150 mL) was flushed with argon for 20 min in a 250
mL Schlenk flask. Potassium acetate (0.9 g, 9 mmol) was added,
and then the mixture was stirred under argon at 70 °C for 15 h.
The mixture was evaporated to dryness, dissolved in a minimal
volume of dichloromethane, and placed on the top of a sinter funnel
loaded with dry silica gel (10 × 10 cm). The funnel was eluted
with petroleum ether/dichloromethane (1:1) under vacuum. The first
colored fractions were combined and evaporated. The product (1.12
g) contains less than 10% of impurities (MS data) and was used in
next reactions without additional purification. For analytical
purposes, the sample of the product (100 mg) was purified by the
column chromatography (silica gel, petroleum ether/dichlo-
romethane (1:1)): yield 92 mg (91%); mp 233 °C; Rf ) 0.26
(hexane/dichloromethane, 3:1); 1H NMR (250 MHz, CD2Cl2,
FIGURE 3. Normalized spectra of QMI 4b in toluene, solid line )
absorption, dashed line ) emission (λexc ) 680 nm).
The absence of the perylene component in the emission of dyad
7 can be attributed to the substantial overlap between the
emission spectrum of the perylene part of the molecule and the
absorption spectrum of the PMI part, which allows for efficient
energy transfer. DiphenoxyQMI 4b shows a bright green color
in solution with an absorption maximum at 735 nm (Figure 3).
As compared to parent PMI 2 (λmax ) 520 nm), the absorption
is shifted bathochromically by 215 nm, owing to the greater
size of the chromophore. A significant increase of the molar
absorption coefficient from 37 000 (for 2b)5 to 143 000 (for
4b) is also observed. The spectrum is similar to that of QDI 1c,
but the bands are shifted hypsochromically by 45 nm as
compared to tetraphenoxy dye (R′ ) phenoxy). Similar to QDI
1c,3 the dye 4b shows only a very weak emission (φF ) 0.15%).
The emission spectrum (Figure 3) reveals mirror symmetry with
the absorption spectrum and a large Stokes shift (80 nm). This
finding, together with a broadening of the emission bands,
additionally supports high aggregation of QMI molecules in
solution. To avoid the complications associated with aggrega-
tion, the emission of QMI derivatives should ideally be tested
by single molecule spectroscopy.16
The photostability of the QMI 4b was estimated by exposing
a nondegassed solution to UV light for a prolonged period of
time. The absorbance dropped to 87% of its initial value after
(17) Seybold, G.; Wagenblast, G. Dyes Pigm. 1989, 11, 303-317.
(18) Xu, C.; Ye, J.; Marks, D. L.; Boppart, S. A. Opt. Lett. 2004, 29,
1647-1649.
(19) Imasaka, T.; Tsukamoto, A.; Ishibashi, N. Anal. Chem. 1989, 61,
2285-2288.
(16) (a) Gohde, W.; Fischer, U. C.; Fuchs, H.; Tittel, J.; Basche, T.;
Herrmann, A.; Mu¨llen, K. J. Phys. Chem. A 1998, 101, 9109-9116. (b)
Christ, T.; Petzke, F.; Bordat, P.; Herrmann, A.; Reuther, E.; Mu¨llen, K.;
Basche, T. J. Lumin. 2002, 98, 23-33.
J. Org. Chem, Vol. 72, No. 26, 2007 10245

25 °C) δ 8.65 (d, 3J ) 8.4 Hz, 1H), 8.26 (d, 3J ) 7.3 Hz, 2H), 8.20
N-(2,6-Diisopropylphenyl)-1,6-bis(4-(1,1,3,3-tetramethylbutyl)-
phenoxy)quaterrylene-3,4-dicarboximide (4b). Compound 7b
(200 mg, 0.175 mmol) was dissolved in dry dichloromethane (10
mL) in a 25 mL Schlenk flask. After stirring for 20 min under
argon, a solution of anhydrous iron(III) chloride (285 mg, 1.75
mmol) in dry nitromethane (2 mL) was added through a syringe.
The solution was stirred at room temperature for 24 h. Dry methanol
(50 mL) was added to the solution. The resulting precipitate was
filtered, rinsed with methanol, and dried. The precipitate was
purified by the column chromatography on silica gel using toluene
as eluent: yield 108 mg (54%); mp >350 °C; Rf ) 0.52 (toluene);
1H NMR (700 MHz, 1,3,5-trichlorobenzene-d3, 170 °C) δ 9.65 (d,
3J ) 8.6 Hz, 2H), 8.58 (s, 2H), 8.44 (d, 3J ) 8.8 Hz, 2H), 8.39 (d,
3J ) 8.2 Hz, 2H), 8.34 (d, 3J ) 8.3 Hz, 2H), 8.28 (d, 3J ) 7.6 Hz,
2H), 7.73 (d, 3J ) 7.9 Hz, 2H), 7.54 (d, 3J ) 7.8 Hz, 2H), 7.52 (d,
3J ) 8.8 Hz, 4H), 7.41 (t, 3J ) 7.6 Hz, 1H), 7.31 (d, 3J ) 7.9 Hz,
3
3
3
(d, J ) 7.4 Hz, 2H), 8.04 (d, J ) 7.6 Hz, 1H), 7.72 (t, J ) 7.6
Hz, 2H), 7.48-7.57 (m, 3H), 1.43 (s, 12H) ppm; 13C NMR (75
MHz, C2D2Cl4, 25 °C) δ 138.2, 136.0, 134.3, 133.8, 131.2, 131.0,
130.9, 130.8, 128.5, 128.4, 127.9, 127.7, 126.8, 126.7, 126.6, 120.9,
120.4, 120.2, 120.1, 119.3, 83.7, 24.9 ppm; IR (KBr) ν 3420, 2970,
2920, 1499, 1369, 1350, 1324, 1272, 1144, 1120, 849, 813, 772
cm-1; UV-vis (toluene) λmax (ꢀ) 451 (31100), 424 (24900), 401
(11700) nm; fluorescence (toluene) λmax 462, 491 nm; MS (FD)
m/z (rel. int.) 378.59 (100%), M+. Anal. Calcd for C26H23BO2: C,
82.55; H, 6.13. Found: C, 82.62; H, 6.07.
N-(2,6-Diisopropylphenyl)-1,6-bis(4-(1,1,3,3-tetramethylbutyl)-
phenoxy)-9-(perylen-3-yl)perylene-3,4-dicarboximide (7b). N-(2,6-
Diisopropylphenyl)-1,6-bis(4-(1,1,3,3-tetramethylbutyl)phenoxy)-
9-bromoperylene-3,4-dicarboximide (194 mg, 0.2 mmol) and
compound 6 (115 mg, 0.3 mmol) were dissolved in the mixture of
toluene (40 mL) and ethanol (2 mL) in a 100 mL Schlenk flask
and flushed with argon. After stirring at 95 °C for 20 min, 2 M
aqueous K2CO3 (0.5 mL) and Pd(PPh3)4 (20 mg, 0,02 mmol) were
added to the solution. The reaction mixture was stirred at 100 °C
for 20 h under argon. After cooling, the resulting mixture was
washed with water and extracted with toluene. The combined
organic extracts were evaporated in vacuo and purified by column
chromatography on silica gel using toluene as an eluent: yield 185
3
3
2H), 7.29 (d, J ) 8.4 Hz, 4H), 3.00 (sep, J ) 6.8 Hz, 2H), 1.88
3
(s, 4H), 1.51 (s, 12H), 1.28 (d, J ) 6.8 Hz, 12H), 0.92 (s, 18H)
ppm; 1H-1H COSY experiment (700 MHz, 1,3,5-trichlorobenzene-
d3, 170 °C) coupling of δ ) (9.65, 8.44), (8.39, 8.34), (8.28, 7.54),
(7.73, 7.54), (7.52, 7.29), (7.41, 7.31); IR (KBr) ν 3449, 2956, 2923,
2853, 1700, 1664, 1585, 1502, 1466, 1320, 1302, 1272, 1203, 1172,
806 cm-1; UV-vis (toluene) λmax (ꢀ) 734 (143000), 668 (57000),
614 (15700), 358 (13300) nm; fluorescence (toluene) λmax 814 nm;
MS (FD) m/z (rel. int.) 1138.6 (100%), M+. Anal. Calcd for C82H75-
NO4: C, 86.51; H, 6.64; N, 1.23. Found: C, 86.58; H, 6.61; N,
1.19.
1
mg (81%); mp 300 °C; Rf ) 0.66 (toluene); H NMR (250 MHz,
CD2Cl2, 25 °C) δ 9.50 (d, 3J ) 8.0 Hz, 1H), 9.38 (d, 3J ) 7.8 Hz,
3
3
1H), 8.36 (d, J ) 7.9 Hz, 1H), 8.31 (d, J ) 7.6 Hz, 1H), 8.25-
8.28 (m, 3H), 7.76 (d, 3J ) 7.9 Hz, 2H), 7.66 (t, 3J ) 9.1 Hz, 2H),
3
4
7.42-7.59 (m, 10H), 7.32 (dd, J ) 7.7 Hz, J ) 3.7 Hz, 4H),
7.14 (d, 3J ) 8.7 Hz, 2H), 7.09 (d, 3J ) 8.8 Hz, 2H), 2.72 (sep, 3J
) 6.8 Hz, 2H), 1.75 (s, 2H), 1.74 (s, 2H), 1.39 (s, 6H), 1.38 (s,
Acknowledgment. Financial support of this work by BASF
AG and Deutsche Forschungsgemeinschaft (project SFB 625)
is gratefully acknowledged. We also acknowledge Prof. Graham
Bodwell and Mr. Don Cho for their help in preparing this
manuscript.
3
6H), 1.11 (d, J ) 6.7 Hz, 12H), 0.73 (s, 9H), 0.72 (s, 9H) ppm;
13C NMR (125 MHz, C2D2Cl4, 25 °C) δ 163.0, 153.7, 153.0, 146.4,
145.4, 140.5, 137.5, 134.5, 129.1, 128.4, 127.4, 126.4, 123.9, 121.2,
121.2, 120.5, 120.4, 119.9, 118.3, 57.0, 53.7, 38.1, 31.6, 31.3, 29.6,
28.9, 23.9 ppm; IR (KBr) ν 3440, 2956, 2924, 2853, 1705, 1669,
1596, 1503, 1465, 1332, 1261, 1209, 1125, 1094, 810 cm-1; UV-
vis (toluene) λmax (ꢀ) 523 (64700), 492 (45000), 446 (33500), 418
(31600) nm; fluorescence (toluene) λmax 604 nm; MS (FD) m/z (rel.
int.) 1140.6 (100%), M+. Anal. Calcd for C82H77NO4: C, 86.36;
H, 6.81; N, 1.23. Found: C, 86.46; H, 6.74; N, 1.18.
Supporting Information Available: Experimental procedures,
characterization for compounds 4a, 4c, 7a, and 7c and 1H and 13
C
NMR spectra for 4a-c, 6, and 7a-c. This material is available
free of charge via the Internet at http://pubs.acs.org.
JO702019P
10246 J. Org. Chem., Vol. 72, No. 26, 2007