Λ-type regioregular oligothiophenes: Synthesis and second-order NLO properties

Article abstract of DOI:10.1021/jo070888a

(Chemical Equation Presented) The synthesis of a new series of Λ-type, D-Π-A regioregular oligothiophenes is described. The simultaneous presence of the chiral centers and the Λ-type structure disfavored the formation of centro-symmetrical dimeric assembl

Full text of DOI:10.1021/jo070888a

high stability and processability. However, the D-Π-A structure
presents some drawbacks. First, the transparency-efficiency
tradeoff is difficult to settle with conventional D-Π-A systems
because the desirable âHRS increase is associated with a
bathochromatic shift of the electronic transition.4 Moreover,
most one-dimensional (1D) NLO-phores favor the formation
of a centrosymmetric arrangement in the crystal because of
dipole-dipole intermolecular interactions and exhibit no SHG
response. Concerning phase matching conditions, the optimal
molecular orientation of the 1D NLO-phore in the crystal does
not allow one to recover more than 38% of the microscopic
nonlinear optical response at the macroscopic scale.5
Λ-Type Regioregular Oligothiophenes: Synthesis
and Second-Order NLO Properties
Samia Zrig,†,‡ Guy Koeckelberghs,‡ Thierry Verbiest,*,‡
Bruno Andrioletti,*,† Eric Rose,*,† Andre´ Persoons,‡
Inge Asselberghs,‡ and Koen Clays‡
Laboratoire de chimie organique (UMR CNRS 7611), Institut de
chimie mole´culaire (FR 2769), UniVersite´ Pierre et Marie
Curie-Paris 6, case 181, 4 place Jussieu, F-75252 Paris cedex
05, France, and Laboratory for Molecular Electronics and
Photonics, Department of Chemistry, Katholieke UniVersiteit
LeuVen, Celestijnenlaan 200 D, B-3001, Belgium
Different approaches such as the use of electric field poling
or the preparation of Langmuir-Blodgett (LB) thin films were
proposed to limit the natural antiparallel dipolar interaction.
However, those strategies suffer from inherent relaxation or
limitations due to the tedious preparation of multilayered LB
films. The preparation of chiral oligothiophenes was also
proposed.6
thierry.Verbiest@fys.kuleuVen.be; andriole@ccr.jussieu.fr;
rose@ccr.jussieu.fr
ReceiVed May 9, 2007
An alternative approach that can rule out the formation of
centrosymmetric supramolecular arrays involves the preparation
of Λ-type molecules that consists in the pre-organization of the
NLO-phore by pairing two chromophores in a predetermined
two-dimensional configuration (2D).7 Additionally, Λ-type
molecules exhibit large off-diagonal â-tensor components
beneficial for the observation of large phase matched second-
order NLO responses,5,8 and high thermal stability.9
Accordingly, following preliminary work that had been
carried out in our groups,10 we designed a new series of regio-
regular11 Λ-type oligothiophenes (bi-, quater-, and sexithiophene)
end-capped with a thermally stable diphenylamino-donating
group, and an imino group, respectively. Despite a modest
accepting character, we retained the versatile imine function
because it allows the easy preparation of a large variety of
The synthesis of a new series of Λ-type, D-Π-A regioregular
oligothiophenes is described. The simultaneous presence of
the chiral centers and the Λ-type structure disfavored the
formation of centro-symmetrical dimeric assemblies. Hence,
enhanced first hyperpolarizabilities âHRS were measured in
comparison with those of the corresponding monomers.
(4) (a) Kanis, D. R.; Ratner, M. A.; Marks, T. J. Chem. ReV. 1994, 94,
195-242. (b) Zyss, J.; Ledoux, I.; Bertault, K.; Toupet, E. Chem. Phys.
1991, 150, 125-135. (c) Marder, S. R.; Kippelen, B.; Jen, A. K.-Y.;
Peyghambarian, N. Nature 1997, 388, 845-851.
In 1964, Rentzepis et al. and Heilmeier et al. first described
the use of organic molecules for the generation of optical second
harmonics (SHG).1 These unprecedented results pioneered the
amazing development of organic nonlinear optic chromophores
(NLO-phores).2 Indeed, as compared to the inorganic analogues,
organic NLO-phores exhibit high versatilities and processabili-
ties together with a low refractive index.3 Considering the high
academic and industrial impact of the second-order NLO
phenomenon, a special emphasis was dedicated to the prepara-
tion of efficient second-order NLO-phores. Among the plethora
of organic NLO-phores, oligothiophenes end-capped with donor
(D) and acceptor (A) moieties, D-Π-A type molecules, are
particularly promising because of a low HOMO-LUMO gap
favoring a high electron mobility, a decent transparency, and a
(5) (a) Yamamato, H.; Katogi, S.; Watanabe, T.; Sato, H.; Miyata, S.;
Hosomi, T. Appl. Phys. Lett. 1992, 60, 935-937. (b) Kuo, W.-J.; Hsiue,
G.-H.; Jeng, R.-J. Macromolecules 2001, 34, 2373-2384.
(6) See, for instance: Kinbinger, A. F. M.; Shenning, A. P. H. J.; Goldoni,
F.; Feast, W. J.; Meijer, E. W. J. Am. Chem. Soc. 2000, 122, 1820-1821.
Shenning, A. P. H. J.; Kinbinger, A. F. M.; Biscari, F.; Cavallini M.; Cooper,
H. J.; Derrick, P. J.; Feast, W. J.; Lazzaroni, R.; Lecle`re, P.; McDonnell,
L. A.; Meijer, E. W.; Meskers, S. C. J. J. Am. Chem. Soc. 2002, 124, 1269-
1275.
(7) Selected examples: (a) Ostroverkhov, V.; Petschek, R. G.; Singer,
K. D.; Twieg, R. J. Chem. Phys. Lett. 2001, 340, 109-115. (b) Coe, B. J.;
Harris, J. A.; Brunschwig, B. S.; Garin, J.; Orduna, J. J. Am. Chem. Soc.
2005, 127, 3284-3285. (c) Moylan, C. R.; Ermer, S.; Lovejoy, S. M.;
McComb, I.-H.; Leung, D. S.; Wortmann, R.; Krdmer, P.; Twieg, R. J. J.
Am. Chem. Soc. 1996, 118, 12950-12955. (d) Van Elshocht, S.; Verbiest,
T.; Kauranen, M.; Ma, L.; Cheng, H.; Musick, K. Y.; Pu, L.; Persoons, A.
Chem. Phys. Lett. 1999, 309, 315-320. (e) Langeveld-Voss, B. M. W.;
Beljonne, D.; Shuai, Z.; Janssen, R. A. J.; Meskers, S. C. J.; Meijer, E. W.;
Bre´das, J.-L. AdV. Mater. 1998, 10, 1343-1348.
† Universite´ Pierre et Marie Curie-Paris 6.
‡ Katholieke Universiteit Leuven.
(1) (a) Rentzepis, P. M.; Pao, Y.-H. Appl. Phys. Lett. 1964, 5, 156-
158. (b) Heilmeier, G. H.; Ockman, N.; Braunstein, R. J.; Kramer, D. A.
Appl. Phys. Lett. 1964, 5, 229-230.
(8) Yang, M. L.; Champagne, B. J. Phys. Chem. A 2003, 107, 3942-
3951.
(2) (a) Prasard, P. N.; Williams, D. J. Introduction to Nonlinear Optical
Effects in Molecules and Polymers; Wiley: New York, 1991. (b) Nonlinear
Optics of Organic and Molecules and Polymers; Nalwa, H. S., Miyata, S.,
Eds.; CRC Press: Boca Raton, FL, 1997.
(3) Hoeben, F. J. M.; Jonkheijm, P.; Meijer, E. W.; Schenning, A. P. H.
J. Chem. ReV. 2005, 105, 1491-1546.
(9) Moylan, C. R.; Twieg, R. J.; Lee, V. Y.; Swanson, S. A.; Betterton,
K. M.; Miller, R. D. J. Am. Chem. Soc. 1993, 115, 12599-12600.
(10) Loire, G.; Prim, D.; Andrioletti, B.; Rose, E.; Persoons, A.; Sioncke,
S.; Vaissermann, J. Tetrahedron Lett. 2002, 43, 6541-6544.
(11) For other regioregular oligothiophenes, see, for instance: Sakurai,
S.; Goto, H.; Yashima, E. Org. Lett. 2001, 3, 2379-2382.
10.1021/jo070888a CCC: $37.00 © 2007 American Chemical Society
Published on Web 06/27/2007
J. Org. Chem. 2007, 72, 5855-5858
5855

The key step for the preparation of the quater- and
sexithiophenes 8 and 13 (Scheme 2) consisted in the de-
symmetrization of the oligomer. As the incorporation of an
already formylated thiophene on the oligothiophene chain was
low yielding and hardly reproducible, we decided to carry out
the preliminary coupling of a thiophene subunit followed by a
subsequent formylation. The optimized conditions for the
preparation of terthiophene 6 involved a Suzuki coupling
between 1 and 1.14 equiv of the boronic ester 5. Using Pd-
(PPh3)4 as catalyst and K2CO3aq as base, 6 was isolated in 45%
yield. Using the same conditions, the symmetrical quater-
thiophene 9 was isolated in 86% yield by condensation of 1
with 2.5 equiv of 5. After double bromination of 9, an iterative
procedure allowed the preparation of quinquethiophene 11 from
10 in 35% yield. Subsequently, ter- and quinquethiophene 6
and 11 were efficiently formylated using a classical Vilsmeier-
Haack procedure in 91% and 100% yield, respectively. Finally,
a Stille coupling using Pd2(dba)3-AsPh3 as catalyst afforded
the unsymmetrical quater- and sexithiophenes 8 and 13 in 95%
and 89% yield, respectively. Oligothiophenes 4, 8, and 13 were
fully characterized using the usual techniques (see Experimental
Section).
Ultimately, the Λ-type structures were readily prepared by
condensation of two equivalents of formyl D-Π-A oligo-
thiophenes 4, 8, and 13 with stoichiometric amounts of (R)-
(+)-1,1′-binaphthyl-2,2′diamine 14 or (1R, 2R)-(-)-1,2-diami-
nocyclohexane 15 in the presence of 4 Å molecular sieves,
respectively. The same experimental procedure involving aniline
16 and cyclohexylamine 17 afforded the corresponding linear
analogues (Table 1).
Preliminary NLO experiments carried out in THF in the
presence of triethylamine indicate that our strategy to enhance
the nonlinear optical response in the Λ-shaped molecules was
successful. In Table 1, we listed the first hyperpolarizability
FIGURE 1. General structure of the Λ-type chromophores.
SCHEME 1. Preparation of Dibromobithiophene 1
analogues. Among the parameters we could possibly investigate,
we decided to evaluate the contribution of the θ angle value
defined by the two chromophores, the nature of the imine
function (aryl vs aliphatic), and the number of thiophenes to
the overall second-order NLO response (Figure 1).
To maximize the efficiency of the synthetic approach, we
adopted a convergent strategy based on the exploitation of the
key dibromobithiophene 1. The choice of 1 relies on two
different considerations. First, the two C8 alkyl chains that
functionalize the central “tail to tail” bithiophene are required
for ensuring a good solubility of the oligothiophene moiety in
most organic solvent without disrupting the overall molecular
orbital overlap. 1 was readily prepared by dimerization of
2-bromo-3-octylthiophene using the PdCl2(PhCN)2/AgF system
as catalyst and DMSO as solvent (Scheme 1). In comparison
with the classical two step Stille coupling/bromination generally
proposed for the preparation of oligothiophenes, use of Mori’s
conditions12 (PdCl2(PhCN)2, AgF, DMSO) allowed the efficient
one-step preparation of 1 in 96% yield.
In parallel, the donating 2-(N,N-diphenylamino)thiophene
brick 2 was prepared according to Hartmann’s procedure13
knowing that neither nucleophilic14 nor palladium-catalyzed15
amination of thiophene were successful in our hands. Undoubt-
edly, the absence of an activating electron-withdrawing group
appended on the heterocycle was responsible for the lack of
reactivity. 2 was further quantitatively converted to the corre-
sponding 5-tri-n-butylstannyl analogue 3 after deprotonation
with stoichiometric amounts of n-butyllithium followed by
quenching with chlorotri-n-butylsilane.
â
HRS, measured by hyper-Rayleigh scattering (HRS) at 800 nm,17
for several compounds. In all samples, no multiphoton fluores-
cence was observed. Importantly, we used âHRS instead of the
traditional âzzz value in a Cartesian coordinate system.18 The
reason is two-fold: while it is very straightforward to determine
âzzz from âHRS values for 1D dipolar molecules, it is not the
case for the two-dimensional chromophores used in this study.
For such molecules, there are several nonvanishing tensor
components whose values are highly dependent on the choice
of the coordinate system. Furthermore, it is experimentally very
difficult to deduce the value of all of these components from
HRS measurements. Therefore, we opted for âHRS, which is a
relatively simple combination of all of the tensor components
contributing to the nonlinear optical response. As âHRS can be
considered as the “overall” nonlinear response of the molecules,
an increase in âHRS value of the Λ-shaped dimeric molecules
as compared to that of the monomeric compounds will reflect
an increase in magnitude of one of the hyperpolarizability
components and/or the contribution of new hyperpolarizability
components that are not present in the monomeric system.
The preparation of the accepting imino moiety required the
preparation of the corresponding formyl oligothiophene. Stille
coupling between 3 and the commercially available 5-bromo-
thiophen-2-carboxaldehyde afforded 416 in 74% yield (Scheme
2).
The results listed in Table 1 reveal a general trend. Despite
the fluctuations due to the rather large 10-20% experimental
(12) Masui, K.; Ikegami, H.; Mori, A. J. Am. Chem. Soc. 2004, 126,
5074-5075.
(16) Bedworth, P. V.; Cai, Y.; Jen, A.; Marder, S. R. J. Org. Chem.
1996, 61, 2242-2246.
(13) Heyde, C.; Zug, I.; Hartmann, H. Eur. J. Org. Chem. 2000, 19,
3273-3278.
(17) Olbrechts, G.; Strobbe, R.; Clays, K; Persoons, A. ReV. Sci. Instrum.
1998, 69, 2233-2241.
(14) Prim, D.; Kirsch, G. Tetrahedron 1999, 55, 6511-6526.
(15) Driver, M. S.; Hartwig, J. F. Tetrahedron Lett. 1995, 36, 3609-
3612.
(18) Hendrickx, E.; Clays, K.; Persoons, A. Acc. Chem. Res. 1998, 31,
675-683.
5856 J. Org. Chem., Vol. 72, No. 15, 2007

SCHEME 2. Syntheses of the D-Π-A Oligothiophenes 4, 8, and 13
TABLE 1. Synthesis and Properties of the Imine NLOphores
119° for compound 27. This is in good agreement with the
expected values of 90° for 1,1′-binaphthyl compounds and 109°
for diaminocyclohexane derivatives (19 and 27).
In conclusion, we have developed an efficient strategy leading
to a new type of Λ-shaped D-Π-A oligothiophenes. The
convergent synthetic approach presented here afforded a new
series of chromophores whose second-order nonlinear properties
were estimated. Preliminary âHRS measurements proved the
efficiency of the strategy developed here, as the âHRS values of
the Λ-shaped molecules generally exceed those of the corre-
sponding monomers. Work is currently in progress to elucidate
the independent contributions to the overall NLO response.
âHRS
entry
aldehyde
amine
iminea
(10-30 esu)
1
2
3
4
5
6
7
8
9
4
4
4
4
8
8
8
8
13
13
13
13
14
15
16
17
14
15
16
17
14
15
16
17
18 (32)
19 (12)
20 (29)
21 (29)
22 (86)
23 (86)
24 (65)
25 (75)
26 (47)
27 (46)
28 (57)
29 (82)
190
122
126
110
185
335
ND
125
1535
262
277
257
Experimental Section
5,5′-Dibromo-4,4′-dioctyl-2,2′-bithiophene, 1. A two-neck round-
bottom flask shed from light was charged with AgF (2.11 g, 16.78
mmol), 2-bromo-3-octylthiophene (2.3 g, 8.39 mmol), Pd(PhCN)2Cl2
(96 mg, 0.251 mmol), and DMSO (30 mL). The reaction was
allowed to proceed for 16 h at 30 °C. The black reaction mixture
was filtered over celite and extracted with AcOEt (200 mL). The
filtrate was washed with water (2 × 150 mL) and brine (100 mL),
before being dried over Na2SO4, filtered, and concentrated. The
crude product was purified by silica gel column chromatography
(cyclohexane) to afford 1 as a yellow oil (2.21 g, 96%). 1H
(CDCl3): 6.77 (s, 2H, H3Th), 2.51 (t, J ) 7.70 Hz, 4H, H1Oct), 1.57
(m, 4H, H2Oct), 1.29 (m, 20H, H3-7Oct), 0.88 (t, J ) 6.80 Hz, 6H,
10
11
12
a Yields are given in parentheses; ND ) not determined.
error, λmax is very close to the frequency doubled, it is clear
that âHRS of dimeric compounds is generally significantly higher
than that of the corresponding monomeric compounds. Further-
more, it has been shown that it should be possible to determine
the dihedral angle19 between the chromophores in bisdipolar
compounds of the type measured here, provided that some
assumptions are made. For example, one needs to assume that
the monomeric compound has only one hyperpolarizability
component âzzz and that off-diagonal tensor components do not
contribute to the nonlinear optical response of the dimeric
compound. Using these assumptions, âHRS can be expressed
solely in terms of âzzz for the monomer or âzzz for the dimer,
and the relation between the two is given19 by âzzz ) 2(cos(θ/
2))3âzzz with θ being the (full) dihedral angle between the two
monomeric chromophore parts. In this way, we calculated the
angle to be 82° for compound 18, 112° for compound 19, and
H
8Oct). 13C (CDCl3): 143.3 (C4Th), 136.5 (C2Th), 124.8 (C3Th), 108.2
(C5Th), 32.2, 30.1, 30.0, 29.9, 29.7, 29.6, 29.0, 14.5 (COct). MS
(MALDI-TOF) m/z (relative intensity) calcd for [C24H36Br2S2]+:
548.0605. Found: 469 (100) [M - Br]+, 548 (10) [M]+. Anal.
Calcd for C24H36Br2S2: C, 52.56; H, 6.62. Found: C, 52.71; H,
6.87.
Typical Procedure for the Suzuki-type Couplings: Synthesis
of 5′′-Bromo-3′,4′′-dioctyl-2,2′:5′,2′′-terthiophene, 6. 2-(4,4,5,5-
Tetramethyl-1,3,2-dioxaborane)-thiophene 5 (3.06 g, 14.5 mmol),
5,5′-dibromo-4,4′-dioctyl-2,2′-bithiophene 1 (6.98 g, 12.7 mmol),
and Pd(PPh3)4 (820 mg, 0.71 mmol) were dissolved in THF (120
mL) before aqueous K2CO3 (2M, 32 mL, 63.7 mmol) was added.
The reaction mixture was brought to reflux for 36 h. After being
cooled to room temperature, the mixture was poured in water (100
mL) and extracted with CH2Cl2 (3 × 100 mL). The organic layers
were combined, washed with water (100 mL), dried over Na2SO4,
(19) Deussen, H.-J.; Hendrichx, E.; Boutton, C.; Krog, D.; Clays, K.;
Bechgaard, K.; Persoons, A.; Bjørnholm, T. J. Am. Chem. Soc. 1996, 118,
6841-6852.
J. Org. Chem, Vol. 72, No. 15, 2007 5857

filtered, and concentrated in vacuo. The crude product was purified
thiophen-5-carboxaldehyde, 8. Triphenylarsine (282 mg, 0.92
mmol) was added to a solution of Pd2dba3 (211 mg, 0.23 mmol) in
THF (10 mL). After being stirred for 30 min, the purple solution
turned yellow. Separately, 5′′-bromo-3′,4′′-dioctyl-2,2′:5′,2′′-ter-
thiophen-5-carboxaldehyde 7 (2.67 g, 4.61 mmol) and 2-(N,N-
diphenylamino)-5-tri-n-butylstannylthiophene 3 (3.42 g, 5.07 mmol)
were dissolved in THF (60 mL), and the Pd(AsPh3)4 catalyst
prepared above was added. The reaction mixture was refluxed for
24 h. After being cooled to room temperature, the mixture was
poured in water (60 mL) and extracted with CH2Cl2 (3 × 50 mL).
The organic layers were combined, washed with water (100 mL),
dried over Na2SO4, filtered, and concentrated in vacuo. The
expected compound 8 (3.11 g, 90%) was isolated as a red oil after
silica gel column chromatography (cyclohexane/CH2Cl2: 1/1). 1H
(CDCl3): 9.88 (s, 1H, HCHO), 7.70 (d, J ) 4.04 Hz, 1H, H4Th),
7.30 (dd, J ) 7.33 Hz, 7.32 Hz, 4H, H3Ph), 7.21 (d, J ) 4.04 Hz,
1H, H3Th), 7.19 (d, J ) 7.33 Hz, 4H, H2Ph), 7.06 (dd, J ) 7.32 Hz,
2H, H4Ph), 7.01 (s, 1H, H4′Th), 6.99 (1H, s, H3′′Th), 6.91 (d, J )
3.79 Hz, 1H, H3′′′Th), 6.63 (d, J ) 3.79 Hz, 1H, H4′′′Th), 2.79 (t, J
) 7.84 Hz, 2H, H1Oct), 2.70 (t, J ) 7.84 Hz, 2H, H1′Oct), 1.65 (m,
4H, H2Oct), 1.27 (m, 20H, H3-7Oct), 0.88 (t, J ) 5.80 Hz, 6H, H8Oct).
13C (CDCl3): 182.9 (CCHO), 152.0 (C5Th), 147.9 (C1Ph), 146.6 (C2Th),
143.5 (C2′Th), 143.1 (C3′Th), 142.3 (C4′′Th), 140.3 (C5′Th), 137.6
(C2′′′Th), 137.3 (C4Th), 133.7 (C5′′Th), 131.6 (C2′′′Th), 129.6 (C3Ph),
128.5 (C5′′′Th), 127.6 (C4′Th), 127.1 (C3′′Th), 126.1 (C3Th), 124.8
(C3′′′Th), 123.6 (C4Ph), 123.1 (C2Ph), 121.1 (C4′′′Th), 32.2, 30.8, 30.5,
30.5, 30.2, 30.0, 29.9, 29.7, 29.6, 23.0, 14.5 (COct). MS (MALDI-
TOF) m/z calcd for [C45H51NOS4]+: 749.2853. Found: 749.2848
[M]+. IR νCO (cm-1): 1665.5. UV λmax (ꢀ) in CH2Cl2: 432 nm
(29 000 M-1 cm-1).
by silica gel column chromatography (cyclohexane) to afford 6 as
1
a yellow oil (3.16 g, 45%). H (CDCl3): 7.31 (dd, J ) 5.25 Hz,
1.14 Hz, 1H, H5Th), 7.12 (dd, J ) 3.66 Hz, 1.14 Hz, 1H, H3Th),
7.06 (dd, J ) 5.25 Hz, 3.66 Hz, 1H, H4Th), 6.92 (s, 1H, H4′Th),
6.84 (s, 1H, H3′Th), 2.71 (t, J ) 7.82 Hz, 2H, H1′Oct), 2.53 (t, J )
7.82 Hz, 2H, H1Oct), 1.62 (m, 4H, H2,2′Oct), 1.30 (m, 20H,
H
3-7,3′-7′Oct), 0.88 (t, J ) 6.84 Hz, 6H, H8,8′Oct). 13C (CDCl3): 143.3
(C4′′Th), 140.6 (C3′Th), 136.9 (C5′Th), 136.1 (C2′′Th or C2′Th), 134.8
(C2′′Th or C2′Th), 130.0 (C2Th), 127.8 (C4Th), 126.6 (C3′′Th), 126.2
(C4′Th), 125.8 (C5Th), 124.6 (C3Th), 107.9 (C5′′Th), 32.2, 32.2, 31.7,
30.0, 29.9, 29.9, 29.7, 29.7, 29.6, 29.5, 28.9, 23.0, 23.0, 14.5 (COct).
MS (MALDI-TOF) m/z calcd for [C28H39BrS3]+: 552.1377.
Found: 552.0930 ([M]+).
Typical Procedure for the Vilsmeier-Haack Formylation:
Synthesis of 5′′-Bromo-3′,4′′-dioctyl-2,2′:5′,2′′-terthiophen-5-
carboxaldehyde, 7. DMF (1.83 mL, 19.6 mmol) was added slowly
to POCl3 (1.52 mL, 19.6 mmol) at 0 °C. After 15 min without
stirring, a white solid was formed and a solution of 5′′-bromo-
3′,4′′-dioctyl-2,2′:5′,2′′-terthiophene 6 (1.08 g, 1.96 mmol) in
dichloroethane (60 mL) was added. The yellow reaction mixture
was stirred and brought to reflux for 12 h. The solution turned red.
After the mixture was cooled to room temperature, an aqueous
solution of AcONa (2 M, 20 mL, 40 mmol) was added and the
biphasic mixture was brought to reflux for 2 h. The mixture was
poured in water (50 mL) and extracted with CH2Cl2 (3 × 100 mL).
The organic layers were combined, washed with water (100 mL),
dried over Na2SO4, filtered, and concentrated in vacuo. The crude
product was purified by silica gel column chromatography (cyclo-
hexane/CH2Cl2: 6/4) to afford 7 as a yellow oil (1.02 g, 91%). 1H
(CDCl3): 9.88 (s, 1H, HCHO), 7.70 (d, J ) 4.0 Hz, 1H, H4Th), 7.21
(d, J ) 4.0 Hz, 1H, H3Th), 6.95 (s, 1H, H4′Th), 6.95 (s, 1H, H3′′Th),
2.78 (t, J ) 7.7 Hz, 2H, H1Oct), 2.54 (t, J ) 7.7 Hz, 2H, H1′Oct),
1.63 (m, 4H, H2-2′Oct), 1.27 (m, 20H, H3-7,3′-7′Oct), 0.88 (t, J ) 5.8
Hz, 6H, H8,8′Oct). 13C (CDCl3): 182.9 (CCHO), 146.3 (C5Th), 143.6
(C3′Th), 143.4 (C4′′Th), 142.5 (C2Th), 137.2 (C2′Th), 137.0 (C5′Th), 136.2
(C2′′Th), 128.2 (C4Th), 127.3 (C3Th), 126.3 (C4′Th), 125.4 (C3′′Th), 109.0
(C5′′Th), 32.2, 30.6, 30.1, 30.0, 29.9, 29.7, 29.7, 29.6, 27.2, 23.0,
14.5 (COct). MS (MALDI-TOF) m/z (relative intensity) calcd for
[C29H39BrOS3]+: 578.1346. Found: 578.1341 (85) [M]+, 579.1372
(31) [M + H]+, 580.1322 (100) [M]+. IR νCO (cm-1): 1664.4.
Typical Procedure for the Stille-type Couplings: Synthesis
of 3′,4′′-Dioctyl-5′′′-N,N-diphenylamino-2,2′:5′,2′′:5′′,2′′′-quater-
Acknowledgment. We thank the KU Leuven (GOA) and
the CNRS for financial support. G.K. and I.A. acknowledge a
fellowship from the fund for scientific research-Flanders FWO-
V. S.Z. acknowledges a fellowship from the KU Leuven GOA
2006/03.
Supporting Information Available: Experimental procedures
1
and complete characterization of all compounds; copies of the H
and 13C spectra of compounds 1, 6-13. This material is available
free of charge via the Internet at http://pubs.acs.org.
JO070888A
5858 J. Org. Chem., Vol. 72, No. 15, 2007