Efficient pseudo-five-component coupling-Fiesselmann synthesis of luminescent oligothiophenes and their modification

Article abstract of DOI:10.1039/c3ob40124c

(Hetero)aryl bis-acid chlorides and terminal alkynes, or likewise acid chlorides and terminal dialkynes, and ethyl 2-mercaptoacetate can be reacted to give highly luminescent symmetrical terthiophenes and quinquethiophenes in the sense of a consecutive pseudo-five-component reaction in good to excellent yields. Further functionalization of the obtained oligomers can be readily achieved by halogenation followed by a metal-catalyzed coupling reaction to give α,ω-diester substrates for subsequent transformations into highly functionalized materials. The Royal Society of Chemistry.

Full text of DOI:10.1039/c3ob40124c

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Efficient pseudo-five-component coupling-Fiesselmann synthesis Voiefw Article Online
luminescent oligothiophenes and their modification†‡
Marco Teiber,a Sönke Giebeler, a Timo Lessing,a and Thomas J. J. Müller*a
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
First published on the web Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
5
(Hetero)aryl bisacidchlorides and terminal alkynes, or likewise acidchlorides and terminal
dialkynes, and ethyl 2-mercapto acetate can be reacted to give highly luminescent symmetrical
terthiophenes and quinquethiophenes in the sense of a consecutive pseudo-five-component reaction
10 in good to excellent yield. Further functionalization of the obtained oligomers can be readily
achieved by halogenation followed by a metal-catalyzed coupling-reaction to give ,-diester
substrates for subsequent transformations into highly functionalized materials.
In the past years we have developed rapid diversity-oriented
accesses to functional chromophores9 and electrophores based
upon the productive concepts of consecutive multicomponent
synthesis of heterocycles and domino transformations initiated
55 by transition metal catalyzed alkyne coupling.10 Furthermore
rapid one-pot sequences to (oligo)thiophenes could be scouted
and methodologically developed.11 Now, we set out to expand
our recently reported three-component coupling-Fiesselmann
synthesis of 2,4-disubstituted thiophene 5-carboxylates to an
60 access of functionalized oligothiophenes as electronically
tunable extended -system building blocks.12 Here, we report
on the synthesis and optical properties of selected
oligothiophenes. In addition, we disclose various
functionalizations of the multicomponent products for rapidly
65 accessing interesting building blocks for materials syntheses.
Introduction
Thiophenes and oligothiophenes represent important building
15 blocks in the synthesis of natural products1 and
pharmaceuticals.2
Additionally,
in
recent
years
oligothiophenes have adopted a major role among functional
-electron systems,3 in particular, as hole transport materials
in organic light emitting diodes,4 organic field-effect
20 transistors,5 and organic photovoltaics.6 Besides the molecular
structure especially the conformation and morphology of these
electroactive oligomers exert a decisive influence on the bulk
materials’ properties.
For a long time polythiophenes with a 2,5-linking pattern have
25 efficiently been synthesized, e.g. by electropolymerisation.7
Functionalized monomers can also be applied to improve the
typically poor solubility of oligo- and polythiophenes as a
necessary prerequisite for solution-based processing. In
contrary to 2,5-linked polymers with variable polydispersity,
30 the efficient synthesis of monodisperse well-defined
oligothiophenes still remains a challenge. The latter are
Results and discussion
Recently we communicated a concise, consecutive three-
component transformation of (hetero)aroyl chlorides 1,
alkynes 2, and ethyl 2-mercapto acetate (3) to give 2,4-
particularly interesting for vacuum deposition processing 70 disubstituted thiophene 5-carboxylates 4 in moderate to
finally furnishing defectfree high-quality films.8 Furthermore,
functionalized oligo- and polythiophene scaffolds do not only
35 influence the solubility or self-organization, but even more the
photophysical and electronic molecular properties. In addition
oligomer conformations largely depend on the substituent
decoration and they are responsible for extended -electron
conjugation and for bulk charge transport properties.3
40 Particularly interesting are functionalities on oligothiophene
scaffolds that can be addressed under mild enzymatic
conditions. Thereby conformational organization of electronic
functional oligothiophenes under kinetic control leading to
highly tunable electronic materials can be enabled. Finally,
45 the ease of synthetic accessibility of functional organic
materials such as conjugated oligomers by diversity oriented
synthesis9 is a highly demanding methodological challenge,
which can be efficiently reached by way of one-pot syntheses
where all functionalities can be introduced in a very concise
50 and convergent fashion.
excellent yields in the sense of a coupling-Fiesselmann
synthesis (Scheme 1).12
Scheme 1 Consecutive three-component Sonogashira alkynylation-
75 Fiesselmann cyclocondensation synthesis of 2,4-disubstituted thiophene
5-carboxylates 4.
This efficient methodology can be readily expanded to the
synthesis of more extended conjugated oligomers. By
choosing thiophene-2,5-dicarbonyl dichloride (5) as
a
80 coupling partner symmetrically substituted ter- and
quinquethiophenes 6 can be synthesized in good yields in a
one-pot fashion and in the sense of a pseudo-five-component
reaction (Scheme 2, Figure 1).
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half set of signals. The thiophene based systems 6 and 8
display two characteristical singlets with identical ViinetwenAsrtiitcyle Oinnline
the aromatic region of the 1H NMR spectra, whereas the
30 phenylene analogues 10 and 12 exhibit two singlets with an
integral ratio of 1:2. In all cases the typical triplet and quartet
of the ethyl ester is most characteristically found. The MALDI
spectra of all compounds likewise reveal a characteristic
fragmentation pattern arising from the loss of an ethoxy
35 radical from the molecular peak.
As previously shown for the synthesis of 2,4-disubstituted
thiophene 5-carboxylates 4 the Fiesselmann thiophene
synthesis13,14 via the multicomponent approach to the
oligothiophenes 6, 8, 10, and 12 advantageously applies a
40 small set of mono- and dialkynes or mono- and
diacidchlorides. They are readily available or easily accessible
substrates for rapidly creating a library of functional -
systems in a one-pot fashion. In the series of the derivatives 6
the electronic nature of the alkynes 2 was scouted to give that
45 electron deficient, electroneutral, electron rich, heterocyclic
and even cyclopropyl alkynes are equally well tolerated. Even
the highly sensitive 2,5-diethynylthiophene (7) furnishes the
corresponding symmetrical oligothiophenes 8 in an average
isolated yield of 68 %, which equals a yield of 88 % per bond
50 forming step.
Scheme 2 Consecutive pseudo-five-component Sonogashira alkynylation-
Fiesselmann cyclocondensation synthesis of symmetrically substituted
ter- and quinquethiophenes 6.
5
Likewise 2,5-diethynylthiophene (7) furnishes centrally ,’-
disubstituted ter- and quinquethiophenes 8 in good yields
(Scheme 3, Figure 1). It should be noted that the use of
dialkyne 7 is not trivial, since it is known to be very unstable
and to decompose already at -25 °C. Only under nitrogen and
10 upon exclusion of light it can be handled for a few hours.
The electronic properties of the oligothiophene derivatives 6,
8, 10, and 12 were thoroughly studied by UV/vis and
fluorescence spectroscopy (Table 1, Figure 2 and 3). Most
strikingly, large Stokes shifts ṽ are observed for all
55 representatives. In addition, the fluorescence quantum yields
f were determined with coumarin 1 (f = 0.73) as a standard.
Expectedly, the absorption maxima max,abs of the
oligothiophenes 6 are blueshifted by 2700-7600 cm-1 in
comparison to the bands of the analogous oligothiophenes 8.
60 Only the oligothiophenes 6 can be finetuned in their
absorption behavior by the electronic nature of the remote
terminal substituents, displaying max,abs in the range from 307
to 359 nm. In contrast the absorption maxima max,abs of the
analogous oligothiophenes 8 are found around 395 nm.
65 Interestingly, all compounds 6 and 8 display emission maxima
around 445 nm, independent of both the ligation and the
substitution pattern. The common structural feature of all
oligothiophene derivatives is the conjugated terthienyl moiety
Scheme 3 Consecutive pseudo-five-component Sonogashira alkynylation-
Fiesselmann cyclocondensation synthesis of centrally ,’-disubstituted
ter- and quinquethiophenes 8
15 Terephthaloyl dichloride (9) reacts with alkynes 2 giving rise
to the formation of the thienyl terminated dumbbells 10,
whereas 1,4-diethynylbenzene (11) and the acid chlorides 1
furnish the p-phenylene bridged symmetrical molecules 12 in
moderate to good yields (Scheme 4, Figure 1).
symmetrically
substituted
with
ethyl
carboxylate
70 functionalities
6 and 8. It can be concluded that the
vibrationally relaxed excited state structures of both series are
geometrically very similar, presumably, other than in the
electronic ground state, with extended coplanarity of all three
thienyl units. Since significant deviations from coplanarity are
75 known for 2,5-linked oligothiophenes with sterically crowded
substituents causing a twisting of the conjugated backbone,15
it is obvious that second redshifted emission shoulders are
detected around 471 nm for the systems 8 (Figure 2). The
occurrence of this additional redshifted emission might indeed
80 arise from a planarized excited state geometry with increased
overall delocalization and thereby lowering the vibrationally
relaxed excited state.
20
Scheme 4 Consecutive pseudo-five-component Sonogashira
alkynylation-Fiesselmann cyclocondensation synthesis of the
dithienyl dumbbells 10 and 12.
The structure of all compounds is unambiguously supported
25 by NMR spectroscopy and MALDI spectrometry. Due to the
inherent molecular C2-symmetry all NMR spectra show only a
2
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Figure 1 Symmetrically substituted oligothiophenes 6, 8, 10, and 12 synthesized by consecutive pseudo-five-component Sonogashira alkynylation-
Fiesselmann cyclocondensation synthesis (all yields are isolated yields after chromatographic purification).
10
Table 1 Selected absorption and emission data of the compounds 6,
5 8, 10, and 12.
[a]
[b]
Absorption
Emission
Stokes shift
Entry Compound max,abs [nm]

max,em [nm]
ṽ [d] [cm-1]
(, M-1 cm-1)
(f) [c]
1
2
340 (54800)
328 (51500)
344 (63800)
305 (42300)
307 (43300)
321 (55500)
359 (21500)
398 (30900)
396 (42200)
397 (35300)
395 (30800)
395 (42000)
395 (41300)
318 (42000)
328 (43200)
361 (43000)
347 (37300)
443 (0.08)
6800
7900
6600
10300
10100
8900
5100
2900
3000
3000
3000
3100
2900
6200
6000
2900
4300
6a
6b
6c
442 (0.09)
3
445 (0.11)
4
444 (0.07)
6d
6e
5
445 (0.10)
6
449 (0.10)
6f
7
440 (0.08)
6g
8
449, 472 (<0.01)
449, 472 (<0.01)
450, 472 (<0.01)
449, 470 (<0.01)
451, 473 (<0.01)
446, 470 (<0.01)
396 (<0.01)
8a
9
8b
8c
10
11
12
13
14
15
16
17
8d
8e
Figure 2 Normalized absorption (solid line) and emission spectra
(dotted line) of compound 8c (recorded in CH2Cl2, T = 293 K,
8f

max,exc 397 nm).
10a
10b
12a
12b
15 Likewise, the phenylene bridged dumbbells 12, obtained from
1,4-diethynyl benzene (11), display two emissions (around
405 and 425 nm) as the thienyl bridged systems 8, whereas
the emission of the dumbbells 10 behaves similarly to the
oligothiophenes 6 and only possess a single maximum around
20 400 nm (Table 1).
408 (<0.01)
404, 425 (<0.01)
408, 428 (<0.01)
[a] Recorded in CH2Cl2, T = 293 K, c0 = 10-3 м. [b] Recorded in CH2Cl2,
[c]
T = 293 K, c0 = 10-6 м.
Fluorescence quantum yields were
determined relative to Coumarin 1 (f = 0.73) as a standard in
ethanol. [d] ṽ = 1/max,abs  1/max,em [cm-1].
Among the synthesized series of oligothiophenes only the
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derivatives 6 reveal substantial quantum yields f ranging
electrophilic brominating agent in a mixture of glacial acetic
from 7 to 11 %, whereas all other systems 8, 10, and 11 are 30 acid and chloroform furnishing the dibromo derVivieawtiAvretiscle1O3nline
only weakly fluorescent with quantum yields below 1 %.
In comparison to their solution luminescence all
oligothiophenes display a pronounced red-shifted emission as
a film and in the solid state. This effect is most remarkable for
the series 6, as illustrated for the emission of
quinquethiophene 6c in solution, in film and in solid state
(Figure 3). Since packing largely influences the preferred
10 ground state conformation in favor of planarization an
extended -conjugation rationalizes the red shift of the
emission. In addition, it is known from 2,5-linked
oligothiophenes that stacking in the solid state occurs directly
or via herringbone packing.16
and 14 (Scheme 5).17
By Sonogashira coupling of the dibromides 13 and 14 with the
ethyl hept-6-ynoate as a coupling partner almost quantitative
yields of ,’-bisethoxycarboxylates 15 and 16 containing
35 conjugated alkynyl moieties were obtained (Scheme 6). These
functionalized oligothiophenes display intense longest
wavelength absorption bands at 340 and 363 nm (15) and 366
nm (16), respectively. The emission maxima are comparable
to the ,-unsubstituted precursors 4a and 6c (max,em around
40 445 nm) and they are found as unstructured bands around 445
nm with fluorescence efficiencies f of 0.05 and 0.08, i.e. also
comparable to 4a and 6c. By introducing long chain aliphatic
substituents, the solubility of the targets in most organic
solvents significantly increases and allows an easy processing
45 from solution, e.g. in transesterification reactions.
5
Conclusions
In conclusion, we have disclosed an efficient consecutive
pseudo-five-component synthesis of oligothiophenes, in
particular,
symmetrically
disubstituted
ter-
and
50 quinquethiophenes and phenylene analogues in good to
excellent yields. All represenatives are luminescent, yet, with
variable fluorescence efficiency. Furthermore, these systems
can be readily modified in post-MCR transformations to
valuable halogenated substrates for metal-catalyzed reactions.
55 For illustration Sonogashira coupling of dibrominated ter- and
quinquethiophenes with an -carboethoxy functionalized
alkyne furnishes ,’-diesters, suitable substrates for
polymerizations and enzymatic transformations. Further
synthetic and photophysical studies with these building blocks
60 are currently underway.
15
Figure 3 Normalized absorption (solid line), and emission spectra of
compound 6c in solution (dotted line), as a film (dashed line), and as
a solid (dotted-dashed line) (recorded at T = 293 K, max,exc
=
344 nm).
20 With this efficient, diversity-oriented synthetic access to
oligothiophenes in hands the stage was set for various post-
MCR modifications. Here, we particularly focused on the
,-functionalization of quinquethiophenes. Provided with
functional groups, e.g. for further ligation, these bifunctional
25 -systems can represent valuable building blocks for the
synthesis of organic materials.
Acknowledgments
The support of this work by CLIB graduate cluster
(scholarship for M. T.) and the Fonds der Chemischen
Industrie is gratefully acknowledged.
The terminal dibromation of the oligothiophenes 4a and 6c
can be achieved in excellent yields with NBS as an
65
Scheme 5 Halogenation of oligothiophenes 4a and 6c via NBS bromination.
4
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Scheme 6 Diterminal functionalization of the dibromides 13 and 14 by Sonogashira coupling.
45
Experimental
Table 2 Experimental details for the synthesis of the oligothiophenes
6.
General considerations
5 All reactions involving palladium-copper catalysis were performed in
degassed oxygen-free solvents under an argon atmosphere in sealed
reaction vessels. All starting materials were purchased from Aldrich,
Fluka, Merck, Acros or ABCR and used without further purification.
Solvents were dried by the solvent purification system: MBraun MB
10 SPS-800. Column chromatography: silica gel 60 (Merck, Darmstadt),
mesh 230-400, Biotage SP-4. TLC: silica gel plates (60 F254 Merck,
Darmstadt). 1H, 13C and DEPT NMR spectra were recorded with a
500 MHz NMR spectrometer by using CDCl3 and DMSO-d6 as
solvent. The assignments of quaternary C, CH, CH2 and CH3 have
15 been made by using DEPT spectra. IR: Perkin-Elmer Lambda 3.
UV/vis and fluorescence: Perkin-Elmer Model Lambda 16 and LS-55.
Mass spectra were recorded with quadruple spectrometer. Elemental
analyses were carried out in the microanalytical laboratory of the
Pharmazeutisches Institut of the Heinrich-Heine-Universität
20 Düsseldorf.
entry
alkyne 2
[mg] (mmol)
oligothiophene 6
[mg] (yield)
1
2
3
4
5
6
7
396 (3.00) of 2a
348 (3.00) of 2b
324 (3.00) of 2c
360 (3.00) of 2d
410 (3.00) of 2e
481 (3.00) of 2f
198 (3.00) of 2g
327 (74 %) of 6a
452 (81 %) of 6b
312 (76 %) of 6c
385 (68 %) of 6d
399 (84 %) of 6e
393 (61 %) of 6f
337 (74 %) of 6g
Diethyl 5,5''-bis(4-methoxyphenyl)-[3,2':5',3''-terthiophene]-
50 2,2''-dicarboxylate (6a)
According to the GP 327 mg (74 %) of 6a were obtained as orange
solid; mp 145 °C. 1H NMR (500 MHz, CDCl3):  = 1.37 (t, J = 7.1
Hz, 6 H), 3.85 (s, 6 H), 4.35 (q, J = 7.1 Hz, 4 H), 6.95 (d, J = 8.9 Hz,
4 H), 7.39 (s, 2 H), 7.60 (d, J = 8.8 Hz, 4 H), 7.62 (s, 2 H). 13C NMR
55 (125 MHz, CDCl3):  = 14.3 (2 CH3), 55.3 (2 CH3), 61.1 (2 CH2),
114.5 (CH), 124.0 (CH), 125.7 (Cquat), 126.0 (CH), 127.5 (Cquat),
129.2 (Cquat), 137.5 (Cquat), 140.5 (Cquat), 148.2 (Cquat), 160.4 (Cquat),
162.0 (Cquat). MALDI MS m/z (%): 604 ([M], 85), 559 ([M] – C2H5O,
100). IR (KBr): ṽ [cm-1] 2959 (w), 2930 (w), 2862 (w), 1699 (s),
60 1605 (m), 1541 (w), 1504 (m), 1464 (m), 1427 (m), 1416 (m), 1292
(w), 1236 (s), 1177 (s), 1101 (s), 1074 (s), 1032 (s), 866 (w), 808 (s),
758 (m), 704 (w), 658 (w). UV/vis (CH2Cl2): max () 340 nm
(54800). Emission (CH2Cl2): max (Stokes shift) 443 nm (6800 cm-1).
Quantum yield (CH2Cl2): f = 0.08. Anal. calcd. for C32H28O6S3
65 (604.8): C 63.55, H 4.67; Found: C 63.36, H 4.82.
General Procedure (GP) for the pseudo-five-component
Sonogashira alkynylation - Fiesselmann cyclocondensation of
thiophene-2,5-dicarbonyl dichloride (5) with alkyne 2 to give
25 oligothiophenes 6
Pd(PPh3)4 (92 mg, 0.08 mmol), CuI (30 mg, 0.16 mmol), and dry
THF (15 mL) were successively placed in the reaction vessel under
nitrogen at room temp and stirred for 5 min. After the addition of
thiophene-2,5-dicarbonyldichloride (5) (209 mg, 1.00 mmol), the
30 alkyne 2 (3.00 mmol), and triethylamine (223 mg, 2.20 mmol) the
reaction mixture was stirred at room temp for 4 h (for experimental
details see Table 2). Then, ethanol (2 mL), ethyl 2-mercapto
acetate (3) (300 mg, 2.50 mmol), and DBU (533 mg, 3.50 mmol)
were successively added at 0 °C and the solution was stirred for 20 h
35 and allowed to come to room temp. For workup, the volatiles were
removed under reduced pressure. The crude product was extracted
three times with a mixture of CH2Cl2 and aqueous 1M HCl. The
combined organic layers were dried with anhydrous MgSO4, absorbed
on celite®, and purified by automated column chromatography on fine
40 silica gel (n-hexane/THF, gradient: 20 % to 35 %, 15 column
volumes, 100 g) to give the compounds 6 as yellow to orange solids.
Further purification can easily be achieved by recrystallization from
ethanol.
Diethyl 3,2'-5',3''-terthiophene-5,5''-bis(p-tolyl)-2,2''-
dicarboxylate (6b)
According to the GP 452 mg (81 %) of 6b were obtained as yellow
solid; mp 134 °C. 1H NMR (500 MHz, CDCl3):  = 1.40 (t, J = 7.1
70 Hz, 6H), 2.41 (s, 6H), 4.37 (q, J = 7.1 Hz, 4H), 7.25 (d, J = 7.9 Hz,
4H), 7.48 (s, 2H), 7.58 (d, J = 8.1 Hz, 4H), 7.65 (s, 2H). 13C NMR
(125 MHz, CDCl3): δ = 14.5 (2 CH3), 21.4 (2 CH3), 61.3 (2 CH2),
124.7 (2 Cquat), 126.2 (4 CH), 126.7 (2 CH), 129.3 (2 CH), 129.9 (4
CH) , 130.3 (2 Cquat), 137.6 (2 Cquat), 139.3 (2 Cquat), 140.5 (2 Cquat),
75 148.5 (2 Cquat), 162.1 (2 Cquat). MALDI MS: m/z (%) = 572 ([M], 75),
527 ([M] - C2H5O, 100). IR (KBr): ṽ [cm-1] = 3021 (w), 2984 (w),
2905 (w), 2866 (w), 1699 (m), 1609 (w), 1545 (w), 1504 (m), 1466
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(w), 1427 (m), 1387 (w), 1348 (w), 1273 (w), 1231 (s), 1184 (m),
1157 (w), 1105 (s), 1078 (m), 1043 (w), 1016 (m), 962 (w), 941 (w),
876 (w), 806 (s), 785 (m), 692 (w). UV/Vis (CH2Cl2): max () = 328
nm (51500). Emission (CH2Cl2): max (Stokes shift) = 442 nm (7900
1076 (s), 1013 (m), 893 (w), 816 (s), 797 (m), 756 (m) 692 (w).
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UV/vis (CH2Cl2): max () 307 nm (43300). Emission (CH2Cl2): max
(Stokes shift) 445 nm (10100 cm-1). Quantum yield (CH2Cl2): f =
60 0.10. Anal. calcd. for C30H22Cl2O4S3 (613.6): C 58.72, H 3.61; Found:
C 58.53, H 3.55.
5 cm-1). Quantum yield (CH2Cl2): f
= 0.09. Anal. calcd. for
C32H28O4S3 (572.8): C 67.10, H 4.93; Found: C 66.99, H 5.01.
Diethyl 3,2'-5',3''-terthiophene-5,5''-bis(p-
(methoxycarbonyl)phenyl)-2,2''-dicarboxylate (6f)
Diethyl [2,2':4',2'':5'',3''':5''',2''''-quinquethiophene]-2''',5'-
dicarboxylate (6c)
According to the GP 393 mg (61 %) of 6f were obtained as orange
65 solid; decomposition at 173 °C. 1H NMR (500 MHz, CDCl3):  =
1.38 (t, ³J = 7.1 Hz, 6H), 3.94 (s, 6H), 4.36 (q, J = 7.1 Hz, 4H), 7.58
(s, 2H), 7.64 (s, 2H), 7.73 (d, J = 8.2 Hz, 4H), 8.09 (d, J = 8.2 Hz,
4H). 13C NMR (125 MHz, CDCl3):  = 14.4 (2 CH3), 52.4 (2 CH3),
61.6 (2 CH2), 126.1 (4 CH), 126.4 (2 Cquat), 128.20 (2 CH), 129.5 (2
70 CH), 130.4 (2 Cquat), 130.6 (4 CH), 137.1 (2 Cquat), 137.4 (2 Cquat),
140.5 (2 Cquat), 146.6 (2 Cquat), 161.8 (2 Cquat), 166.6 (2 Cquat). MALDI
MS: m/z (%) = 660 ([M], 75), 615 ([M] - C2H5O, 100). IR (KBr): ṽ
[cm-1] = 2982 (w), 2955 (w), 2359 (w), 2330 (w), 1717 (m), 1701
(m), 1605 (w), 1503 (w), 1447 (w), 1425 (w), 1410 (w), 1366 (w),
75 1315 (w), 1279 (m), 1233 (m), 1184 (m), 1101 (s), 1082 (m), 1067
(m), 1045 (m), 1016 (m), 961 (w), 934 (w), 883 (w), 847 (m), 824
(m), 768 (s), 735 (w), 692 (m), 656 (w). UV/vis (CH2Cl2): max () =
321 nm (55500). Emission (CH2Cl2): max (Stokes shift) = 449 nm
(8900 cm-1). Quantum yield (CH2Cl2): f = 0.10. Anal. calcd. for
80 C34H28O8S3 (660.8): C 61.80, H 4.27; Found: C 61.60, H 4.22.
According to the GP 312 mg (76 %) of 6c were obtained as yellow
10 solid; mp 141 °C. 1H NMR (500 MHz, CDCl3):  = 1.37 (t, J = 7.1
Hz, 6 H), 4.35 (q, J = 7.1 Hz, 4 H), 7.07 (dd, J = 5.0 Hz, J = 3.7 Hz, 2
H), 7.33 (m, 4 H), 7.35 (s, 2 H), 7.61 (s, 2 H). 13C NMR (125 MHz,
CDCl3):  = 14.3 (2 CH3), 61.2 (2 CH2), 124.2 (2 Cquat), 125.5 (2 CH),
126.4 (2 CH), 127.1 (2 CH), 128.2 (2 CH), 129.3 (2 CH), 135.8 (2
15 Cquat), 137.2 (2 Cquat), 140.2 (2 Cquat), 141.3 (2 Cquat), 161.7(2 Cquat).
MALDI MS m/z (%): 556 ([M], 88), 511 ([M] – C2H5O, 100). IR
(KBr): ṽ [cm-1] 2977 (w), 1710 (s), 1701 (s), 1655 (w), 1638 (w),
1551 (w), 1509 (w), 1474 (w), 1434 (m), 1387 (w), 1232 (s), 1104
(m), 1076 (m), 1019 (w), 805 (m), 758 (m), 733 (m), 690 (m). UV/vis
20 (CH2Cl2): max () = 344 nm (63800). Emission (CH2Cl2): max (Stokes
shift) 445 nm (6600 cm-1). Emission (film): max (Stokes shift) 481
nm (8300 cm-1). Emission (solid): max (Stokes shift) 512 nm (9500
cm-1). Quantum yield (CH2Cl2): f
26H20O4S5 (556.8): C 56.09, H 3.62; Found: C 56.17, H 3.76.
= 0.11. Anal. calcd. for
C
25 Diethyl 3,2'-5',3''-terthiophene-5,5''-bis(m-fluorophenyl)-
2,2''-dicarboxylate (6d)
Diethyl 3,2'-5',3''-terthiophene-5,5''-bis(cyclopropyl)-2,2''-
dicarboxylate (6g)
According to the GP 385 mg (68 %) of 6d were obtained as yellow
solid; mp 144 °C. 1H NMR (500 MHz, CDCl3):  = 1.39 (t, J = 7.1
Hz, 6H), 4.37 (q, J = 7.1 Hz, 4H), 7.04 – 7.11 (m, 2H), 7.33 – 7.47
30 (m, 6H), 7.50 (s, 2H), 7.63 (s, 2H). 13C NMR (125 MHz, CDCl3):  =
According to the GP 337 mg (74 %) of 6g were obtained as yellow
solid, mp 47 °C. 1H NMR (500 MHz, CDCl3):  = 0.79 – 0.84 (m,
85 4H), 1.07 – 1.11 (m, 4H), 1.33 (t, J = 7.1 Hz, 6H), 2.08 (ddd, J =
13.3, 8.4, 5.0 Hz, 2H), 4.29 (q, J = 7.1 Hz, 4H), 6.96 (s, 2H), 7.53 (s,
2H). 13C NMR (125 MHz, CDCl3):  = 10.9 (2 CH2), 11.8 (2 CH3),
14.4 (2 CH), 61.0 (4 CH2), 122.4 (2 Cquat), 127.1 (2 CH), 129.1 (2
CH), 137.6 (2 Cquat), 139.9 (2 Cquat), 154.1 (2 Cquat), 162.0 (2 Cquat).
90 MALDI MS: m/z (%) = 472 ([M], 75), 427 ([M] - C2H5O, 100). IR
(KBr): ṽ [cm-1] = 3082 (w), 2980 (w), 2936 (w), 2903 (w), 2870 (w),
1703 (m), 1549 (w), 1524 (w), 1477 (w), 1452 (m), 1435 (w), 1371
(m), 1229 (s), 1198 (m), 1186 (m), 1171 (m), 1094 (s), 1069 (m),
1022 (m), 962 (w), 937 (w), 941 (w), 874 (m), 829 (m), 808 (m), 760
95 (m), 719 (w), 694 (w), 665 (w), 640 (w). UV/vis (CH2Cl2): max () =
359 nm (21500). Emission (CH2Cl2): max (Stokes shift) = 440 nm
(5100 cm-1). Quantum yield (CH2Cl2): f = 0.08. Anal. calcd. for
C24H24O4S3 (472.6): C 60.99, H 5.12; Found: C 60.18, H 5.26.
2
14.4 (2 CH3), 61.5 (2 CH2), 113.3 (d, J = 23.0 Hz, 2 CH2), 116.0 (d,
2J = 21.2 Hz, 2 CH), 122.0 (d, 4J = 2.8 Hz, 2 CH), 125.9 (2 CH),
3
127.7 (2 CH), 129.5 (2 CH), 130.9 (d, 3J = 8.2 Hz, 2 CH), 135.1 (d, J
= 8.2 Hz, 2 Cquat), 137.5 (2 Cquat), 140.4 (2 Cquat), 146.7 (2 Cquat),
1
35 161.9 (2 Cquat), 162.3 (d, J = 247.1 Hz, 2 Cquat). MALDI MS: m/z (%)
= 580 ([M], 85), 535 ([M] - C2H5O, 100). IR (KBr): ṽ [cm-1] = 2988
(w), 2940 (w), 2901 (w), 2874 (w), 1717 (m), 1611 (w), 1586 (m),
1557 (w), 1533 (w), 1483 (w), 1468 (w), 1445 (m), 1431 (m), 1389
(w), 1354 (w), 1244 (s), 1188 (w), 1175 (m), 1160 (m), 1109 (m),
40 1076 (m), 1049 (w), 1016 (m), 997 (w), 964 (w), 845 (m), 831 (m),
804 (m), 772 (m), 756 (m), 706 (w), 677 (m). UV/vis (CH2Cl2): max
() = 305 nm (42300). Emission (CH2Cl2): max (Stokes shift) = 444
nm (10300 cm-1). Quantum yield (CH2Cl2): f = 0.07. Anal. calcd. for
C30H22F2O4S3 (580.7): C 62.05, H 3.82; Found: C 61.89, H 3.91.
General Procedure (GP) for the pseudo-five-component
100 Sonogashira alkynylation - Fiesselmann cyclocondensation of
2,5-diethynylthiophene (7) with acid chloride 1 to give
oligothiophenes 8
45 Diethyl 5,5''-bis(4-chlorophenyl)-[3,2':5',3''-terthiophene]-
2,2''-dicarboxylate (6e)
The TMS protected thiophene-2,5-dialkyne18 (277 mg, 1.00 mmol),
KOH (27 μL of a 0.5 m aqueous KOH solution) and dry MeOH
105 (5.4 mL) were successively placed in a reaction vessel under nitrogen
and exclusion of light at room temperature and stirred for 30 min.
After the addition of 5.4 mL of water the solution was extracted three
times with 50 mL n-hexane. The combined organic layers were dried
with anhydrous MgSO4 and the volatile components were removed
110 under reduced pressure. In the meantime Pd(PPh3)4 (92 mg,
0.08 mmol), CuI (30 mg, 0.16 mmol), and dry THF (2 mL) were
successively placed in another reaction vessel under nitrogen at room
According to the GP 399 mg (84 %) of 6e were obtained as orange
solid; decomposition at 130 °C. 1H NMR (500 MHz, CDCl3):  =
1.38 (t, J = 7.1 Hz, 6 H), 4.35 (q, J = 7.1 Hz, 4 H), 7.40 (d, J = 8.6
50 Hz, 4 H), 7.46 (s, 2 H), 7.59 (d, J = 8.6 Hz, 4 H), 7.63 (s, 2 H). 13C
NMR (125 MHz, CDCl3):  = 14.3 (CH3), 61.3 (CH2), 125.4 (Cquat),
127.2 (CH), 127.3 (CH), 129.3 (CH), 129.3 (CH), 131.4 (Cquat), 135.0
(Cquat), 137.3 (Cquat), 140.3 (Cquat), 146.7 (Cquat), 161.7 (Cquat). MALDI
MS m/z (%): 614 ([37Cl-35Cl-M], 100), 569 ([37Cl-35Cl-M] – C2H5O,
55 90). IR (KBr): ṽ [cm-1] 2982 (w), 1715 (s), 1682 (m), 1555 (w), 1489
(m), 1468 (w), 1429 (m), 1269 (m), 1240 (s), 1182 (m), 1094 (s),
6
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Page 7 of 11
Organic & Biomolecular Chemistry
temp and stirred for 5 min. After the addition of the acid chloride 1
(w), 1468 (w), 1433 (m), 1366 (m), 1260 (s), 1225 (m), 1188 (m),
50 1155 (w), 1107 (m), 1072 (m), 1022 (m), 935 (w), 90V3ie(wwA),rt8ic6le6O(nwli)n,e
833 (m), 799 (m), 781 (m), 758 (m), 718 (w), 667 (m), 631 (w).
UV/vis (CH2Cl2): max () = 396 nm (42200). Emission (CH2Cl2): max
(Stokes shift) = 449 nm (3000 cm-1), 472 nm. Anal. calcd. for
(3.00 mmol) and triethylamine (223 mg, 2.20 mmol) the previously
deprotected 2,5-diethynylthiophene (7) was dissolved in 8 mL of
THF and added dropwise over 15 min (for experimental details see
5 Table 3). The reaction mixture was stirred for another 4 h at room
temp. Then, ethanol (2 mL), ethyl 2-mercapto acetate (3) (300 mg,
2.50 mmol), and DBU (533 mg, 3.50 mmol) were successively added
and the solution was stirred for 20 h at 70 °C. For workup, the
volatile components were removed under reduced pressure. The crude
10 product was extracted three times with a mixture of CH2Cl2 and
aqueous 1M HCl. The combined organic layers were dried with
anhydrous MgSO4, absorbed on celite®, and purified by automated
column chromatography on fine silica gel (n-hexane/THF, gradient:
20 % to 35 %, 15 column volumes, 100 g) to give the compounds 8 as
15 yellow to orange solids. Further purification can easily be achieved
by recrystallization from ethanol.
C
32H28O4S3 (572.8): C 67.10, H 4.93; Found: C 67.06, H 5.04.
55 Diethyl 2,3'-5',2''-5'',2'''-4''',2''''-quinquethiophene-2',5'''-
dicarboxylate (8c)
According to the GP 398 mg (84 %) of 8c were obtained as orange
solid; mp 174 °C. 1H NMR (500 MHz, CDCl3):  = 1.36 (t, J = 7.1
Hz, 6H), 4.33 (q, J = 7.1 Hz, 4H), 7.10 (dd, J = 5.1 Hz, J = 3.7 Hz,
60 2 H), 7.24 (s, 2 H), 7.30 (s, 2 H), 7.40 (dd, J = 5.1 Hz, J = 1.0 Hz,
2 H), 7.61 (dd,
NMR (125 MHz, CDCl3):  = 14.4 (2 CH3), 61.5 (2 CH2), 124.9 (2
quat), 126.4 (2 CH), 126.9 (2 CH), 127.3 (2 CH), 127.8 (2 CH),
J
=
3.7 Hz,
J
=
1.0 Hz, 2 H). 13C
C
129.3 (2 CH), 135.9 (2 Cquat), 136.5 (2 Cquat), 140.4 (2 Cquat), 140.8 (2
65 Cquat), 161.7 (2 Cquat). MALDI MS: m/z (%) = 556 ([M], 100).
IR (KBr): ṽ [cm-1] = 3092 (w), 2984 (w), 2928 (w), 2907 (w), 1709
(s), 1676 (s), 1547 (w), 1479 (w), 1462 (w), 1443 (s), 1422 (s), 1373
(m), 1310 (w), 1340 (w), 1273 (s), 1248 (s), 1233 (s), 1175 (w), 1125
(w), 1107 (s), 1078 (S), 1067 (m), 1043 (m), 1022 (w), 1011 (w), 856
70 (w), 818 (m), 799 (s), 756 (m), 683 (s), 658 (w). UV/vis (CH2Cl2):
max () = 397 nm (35300). Emission (CH2Cl2): max (Stokes shift) =
450 nm (3000 cm-1), 472 nm. Anal. calcd. for C26H20O4S5 (556.8):
C 56.09 H 3.62; Found: C 55.89 H 3.91.
Table 3 Experimental details for the synthesis of the oligothiophenes
8.
entry
acid chloride 1
oligothiophene 8
[mg] (mmol)
[mg] (yield)
1
2
3
4
5
6
440 (3.00) of 1a
464 (3.00) of 1b
314 (3.00) of 1c
476 (3.00) of 1d
590 (3.00) of 1e
362 (3.00) of 1f
411 (74 %) of 8a
269 (47 %) of 8b
398 (84 %) of 8c
322 (57 %) of 8d
526 (83 %) of 8e
307 (61 %) of 8f
Diethyl 2,2'-5',2''-terthiophene-4,4''-bis(p-fluorophenyl)-5,5''-
Diethyl 2,2'-5',2''-terthiophene-4,4''-bis(p-tbutylphenyl)-5,5''-
75 dicarboxylate (8d)
20 dicarboxylate (8a)
According to the GP 322 mg (57 %) of 8d were obtained as yellow
solid; mp 193 °C. 1H NMR (500 MHz, CDCl3):  = 1.27 (t, J = 7.1
Hz, 6H), 4.25 (q, J = 7.1 Hz, 4H), 7.13 (s, 2H), 7.08 – 7.12 (m, 4H),
7.25 (s, 2H), 7.43 – 7.50 (m, 4H) 13C NMR (125 MHz, CDCl3):  =
80 14.3 (2 CH3), 61.3 (2 CH2), 114.9 (d, 4 CH), 126.0 (2 Cquat), 126.3 (2
CH), 127.9 (2 CH), 131.1 (d, 4 CH), 131.4 (d, 2 Cquat), 136.7 (2 Cquat),
140.7 (2 Cquat), 148.3 (2 Cquat), 161.8 (2 Cquat), 163.8 (2 Cquat). MALDI
MS: m/z (%) = 580 ([M], 100). IR (KBr): ṽ [cm-1] = 3071 (w), 3001
(w), 2980 (w), 2934 (w), 2874 (w), 2361 (w), 2330 (w), 1713 (m),
85 1678 (m), 1601 (w), 1528 (w), 1499 (m), 1476 (w), 1435 (m), 1425
(m), 1377 (m), 1327 (w), 1287 (m), 1263 (s), 1234 (m), 1223 (m),
1188 (w), 1159 (m), 1123 (m), 1096 (m), 1076 (m), 1020 (m), 957
(w), 934 (w), 822 (m), 799 (m), 787 (m), 758 (m). UV/vis (CH2Cl2):
max () = 395 nm (30800). Emission (CH2Cl2): max (Stokes shift) =
90 449 nm (3000 cm-1), 470 nm. Anal. calcd. for C30H22F2O4S3 (580.7):
C 62.05, H 3.82; Found: C 61.91, H 4.08.
According to the GP 411 mg (74 %) of 8a were obtained as orange
solid; mp 185 °C. 1H NMR (500 MHz, CDCl3):  = 1.27 (t, J = 7.1
Hz, 6H), 1.37 (s, 18H), 4.26 (q, J = 7.1 Hz, 4H), 7.17 (s, 2H), 7.24 (s,
2H), 7.44 (s, 8H). 13C NMR (125 MHz, CDCl3):  = 14.3 (2 CH3),
25 31.5 (6 CH3), 34.8 (2 Cquat), 61.2 (2 CH2), 125.0 (4 CH), 125.5 (2
Cquat), 126.2 (2 CH), 128.2 (2 CH), 129.0 (4 CH), 132.5 (2 Cquat),
136.8 (2 Cquat), 140.5 (2 Cquat), 149.5 (2 Cquat), 151.3 (2 Cquat), 161.9
(2 Cquat). MALDI MS: m/z (%) = 657 ([M], 100). IR (KBr): ṽ [cm-1] =
3063 (w), 2955 (m), 2922 (m), 2853 (m), 2687 (w), 1709 (m), 1614
30 (w), 1510 (w), 1466 (m), 1433 (m), 1362 (m), 1256 (s), 1221 (m),
1202 (m), 1190 (m), 1126 (m), 1101 (m), 1074 (m), 1049 (m), 1022
(m), 970 (w), 905 (m), 870 (w), 822 (m), 783 (s), 760 (m), 746 (m),
729 (w), 706 (w), 689 (w), 671 (w), 631 (w). UV/vis (CH2Cl2): max
() = 398 nm (30900). Emission (CH2Cl2): max (Stokes shift) = 449
35 nm (2900 cm-1), 472 nm. Anal. calcd. for C38H40O4S3 (656.9): C
69.48, H 6.14; Found: C 69.87, H 6.60.
Diethyl 2,2'-5',2''-terthiophene-4,4''-bis(tbutyl)-5,5''-
dicarboxylate (8e)
Diethyl 2,2'-5',2''-terthiophene-4,4''-bis(p-tolyl)-5,5''-
dicarboxylate (8b)
According to the GP 526 mg (83 %) of 8e were obtained as yellow
95 solid; decomposition at 126 °C. 1H NMR (500 MHz, CDCl3):  =
1.38 (t, J = 7.1, 6 H), 1.49 (s, 18 H), 4.32 (q, J = 7.1, 4 H), 7.17 (d, J
= 1.8, 4 H). 13C NMR (125 MHz, CDCl3):  = 14.4 (2 CH3), 30.3 (6
CH3), 35.2 (2 Cquat), 61.3 (2 CH2), 125.7 (2 Cquat), 125.8 (2 CH),
126.1 (2 CH), 136.8 (2 Cquat), 139.4 (2 Cquat), 159.5 (2 Cquat), 162.0 (2
100 Cquat). MALDI MS: m/z (%) = 504 ([M], 100). IR (KBr): ṽ [cm-1] =
2959 (w), 2947 (w), 2907 (w), 2870 (w), 1699 (m), 1526 (w), 1460
(w), 1447 (w), 1412 (m), 1391 (m), 1362 (m), 1248 (m), 1391 (m),
1362 (m), 1248 (m), 1231 (s), 1206 (m), 1159 (m), 1115 (w), 1067
(s), 1013 (m), 941 (m), 858 (w), 835 (m), 785 (m), 762 (m), 675 (m).
According to the GP 269 mg (47 %) of 8b were obtained as orange
40 solid; mp 149 °C. 1H NMR (500 MHz, CDCl3):  = 1.28 (t, J = 7.1
Hz, 6H), 2.41 (s, 6H), 4.25 (q, J = 7.1 Hz, 4H), 7.15 (s, 2H), 7.24 (s,
2H), 7.23 (d, J = 9.4 Hz, 4H), 7.39 (d, J = 8.0 Hz, 4H). 13C NMR
(125 MHz, CDCl3):  = 14.3 (2 CH3), 21.5 (2 CH3), 61.2 (2 CH2),
125.5 (2 Cquat), 126.2 (2 CH), 128.1 (2 CH), 128.7 (4 CH), 129.2 (4
45 CH), 132.5 (2 Cquat), 136.8 (2 Cquat), 138.2 (2 Cquat), 140.5 (2 Cquat),
149.6 (2 Cquat), 161.9 (2 Cquat). MALDI MS: m/z (%) = 572 ([M],
100). IR (KBr): ṽ [cm-1] = 3078 (w), 3024 (w), 2980 (w), 2918 (w),
2857 (w), 2718 (w), 1715 (m), 1682 (m), 1616 (w), 1545 (w), 1512
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Journal Name, [year], [vol], 00–00 | 7

Organic & Biomolecular Chemistry
Page 8 of 11
UV/vis (CH2Cl2): max () = 395 nm (42000). Emission (CH2Cl2): max
(Stokes shift) = 451 nm (3100 cm-1), 473 nm. Anal. calcd. for
26H20O4S5 (556.8): C 61.87, H 6.39; Found: C 61.91, H 6.39.
Cquat), 135.6 (2 Cquat), 139.1 (2 Cquat), 148.7 (2 Cquat), 149.1 (2 Cquat),
162.2 (2 Cquat). MALDI MS: m/z (%) = 566 ([M], 100).VIieRw(AKrtBiclre):Oṽnline
[cm-1] = 2963 (w), 2901 (w), 2857 (w), 2361 (w), 1800 (w), 1715
55 (m), 1607 (w), 1551 (w), 1495 (w), 1443 (m), 1350 (w), 1246 (m),
1231 (m), 1207 (m), 1184 (m), 1128 (m), 1103 (m), 1080 (m), 1043
(m), 1018 (m), 962 (w), 895 (w), 827 (w), 812 (s), 795 (m), 760 (m),
692 (w). UV/vis (CH2Cl2): max () = 318 nm (42000). Emission
(CH2Cl2): max (Stokes shift) = 396 nm (6200 cm-1). Anal. calcd. for
60 C34H30O4S2 (566.7): C 72.06, H 5.34; Found: C 70.25, H 5.14.
C
Diethyl 2,2'-5',2''-terthiophene-4,4''-bis(cyclopropyl)-5,5''-
dicarboxylate (8f)
5
According to the GP 307 mg (61 %) of 8f were obtained as yellow
solid; mp 142 °C. 1H NMR (500 MHz, CDCl3):  = 0.60-0.90 (m,
3
4 H), 1.00-1.10 (m, 4 H), 1.38 (t, J = 7.1 Hz, 6 H), 2.90-3.10
(m, 2 H), 4.35 (q, 3J = 7.1 Hz, 4 H), 6.59 (s, 2 H), 7.13 (s,
Diethyl 3,3'-(1,4-phenylene)bis(5,5'-(2-thienyl)-2,2'-
carboxylate) (10b)
10 2 H). 13C NMR (125 MHz, CDCl3):  = 10.5 (4 CH2), 10.9 (2 CH),
14.5 (2 CH3), 61.0 (2 CH2), 121.4 (2 CH), 125.0 (2 Cquat), 125.9 (2
CH), 136.7 (2 Cquat), 140.9 (2 Cquat), 154.2 (2 Cquat), 162.9 (2 Cquat).
MALDI MS: m/z (%) = 472 ([M], 100). IR (KBr): ṽ [cm-1] = 3063
(w), 2990 (w), 2938 (w), 2903 (w), 1697 (m), 1670 (m), 1547 (m),
15 1524 (w), 1476 (w), 1443 (m), 1383 (m), 1364 (w), 1342 (m), 1281
(m), 1227 (s), 1186 (m), 1113 (w), 1084 (s), 1051 (m), 1016 (m), 974
(m), 862 (m), 802 (s), 760 (m), 689 (w), 654 (m). UV/vis (CH2Cl2):
max () = 395 nm (41300). Emission (CH2Cl2): max (Stokes shift) =
446 nm (2900 cm-1), 470 nm. Anal. calcd. for C24H24O4S3 (472.6): C
20 60.99, H 5.12; Found: C 60.75, H 5.03.
According to the GP 208 mg (38 %) of 10b were obtained as white
solid; decomposition at 199 °C. 1H NMR (500 MHz, CDCl3):  =
65 1.30 (t, J = 7.1 Hz, 6 H), 4.27 (q, J = 7.1 Hz, 4 H), 7.10 – 7.05 (m, 2
H), 7.21 (s, 2 H), 7.32 (d, J = 4.4 Hz, 4 H), 7.55 (s, 4 H). 13C NMR
(125 MHz, CDCl3):  = 14.3 (2 CH3), 61.2 (2 CH2), 125.3 (2 Cquat),
125.4 (2 CH), 126.3 (2 CH), 127.8 (2 CH), 128.3 (2 CH), 128.9 (4
CH), 135.4 (2 Cquat), 136.3 (2 Cquat), 141.6 (2 Cquat), 149.0 (2 Cquat),
70 162.0 (2 Cquat). MALDI MS: m/z (%) = 550 ([M], 100). IR (KBr): ṽ
[cm-1] = 3387 (w), 3111 (w), 3073 (w), 2974 (w), 2928 (w), 2853 (w),
1715 (m), 1557 (w), 1497 (w), 1449 (m), 1423 (m), 1368 (m), 1260
(s), 1227 (m), 1198 (m), 1155 (w), 1126 (m), 1105 (m), 1074 (s),
1049 (m), 1020 (m), 910 (w), 847 (m), 808 (m), 758 (m), 685 (s), 658
General Procedure (GP) for the pseudo-five-component
Sonogashira alkynylation - Fiesselmann cyclocondensation of
terephthaloyl dichloride (9) with alkyne 2 to give
oligothiophenes 10
75 (m). UV/vis (CH2Cl2): max ()
(CH2Cl2): max (Stokes shift) = 408 nm (6000 cm-1). Anal. calcd. for
34H30O4S2 (566.7): C 61.06, H 4.03; Found: C 61.26, H 4.28.
= 328 nm (43200). Emission
25 Pd(PPh3)4 (92 mg, 0.08 mmol) and CuI (30 mg, 0.16 mmol) were
successively placed in the reaction vessel under nitrogen at room
temp. After the addition of terephthaloyl dichloride (9) (203 mg,
1.00 mmol), the alkyne 2 (3.00 mmol) and triethylamine (5 mL) the
reaction mixture was stirred at 90 °C for 1 h (for experimental details
30 see Table 4). Then, ethanol (2 mL), THF (2 mL), ethyl 2-mercapto
acetate (3) (300 mg, 2.50 mmol), and DBU (533 mg, 3.50 mmol)
were successively added at 0 °C and the solution was stirred for 20 h
and allowed to come to room temp. For workup, the volatile
components were removed under reduced pressure. The crude product
35 was extracted three times with a mixture of CH2Cl2 and aqueous 1M
HCl. The combined organic layers were dried with anhydrous
MgSO4, absorbed on celite®, and purified by automated column
chromatography on fine silica gel (n-hexane/THF, gradient: 20 % to
35 %, 15 column volumes, 100 g) to give the compounds 10 as
40 yellow to orange solids. Further purification can easily be achieved
by recrystallization from ethanol.
C
General Procedure (GP) for the pseudo-five-component
Sonogashira alkynylation - Fiesselmann cyclocondensation of
80 1,4-diethynyl benzene (11) with acid chloride 1 to give
oligothiophenes 12
Pd(PPh3)4 (92 mg, 0.08 mmol), CuI (30 mg, 0.16 mmol), and dry
THF (10 mL) were successively placed in the reaction vessel under
nitrogen at room temp and stirred for 5 min. After the addition of 1,4-
85 diethynyl benzene (9) (126 mg, 1.00 mmol), the respective acid
chloride 1 (3.00 mmol) and triethylamine (223 mg, 2.20 mmol) the
reaction mixture was stirred at 80 °C for 4 h (for experimental details
see Table 5). Then, ethanol (2 mL), ethyl 2-mercapto acetate (3)
(300 mg, 2.50 mmol), and DBU (533 mg, 3.50 mmol) were
90 successively added and the solution was stirred for another 20 h at
80 °C. For workup, the volatile components were removed under
reduced pressure. The crude product was extracted three times with a
mixture of CH2Cl2 and aqueous 1M HCl. The combined organic
layers were dried with anhydrous MgSO4, absorbed on celite®, and
95 purified by automated column chromatography on fine silica gel (n-
hexane/THF, gradient: 20 % to 45 %, 15 column volumes, 100 g) to
give the compounds 12 as yellow to orange solids. Further
purification can easily be achieved by recrystallization from ethanol.
Table 4 Experimental details for the synthesis of the oligothiophenes
10.
entry
alkyne 2
oligothiophene 10
[mg] (mmol)
[mg] (yield)
1
2
232 (3.00) of 2b
324 (3.00) of 2c
269 (49 %) of 10a
208 (38%) of 10b
Table 5 Experimental details for the synthesis of the oligothiophenes
100 12.
Diethyl 3,3'-(1,4-phenylene)bis(5,5'-p-tolylthiophene-2,2'-
45 carboxylate) (10a)
entry
acid chloride 1
oligothiophene 12
[mg] (mmol)
[mg] (yield)
According to the GP 269 mg (49 %) of 10a were obtained as white
solid; decomposition at 228 °C. 1H NMR (500 MHz, CDCl3):  =
1.30 (t, J = 7.1 Hz, 6H), 2.40 (s, 6H), 4.28 (q, J = 7.1 Hz, 4H), 7.21 –
7.26 (m, 4H), 7.32 (s, 2H), 7.52 – 7.61 (m, 8H). 13C NMR (125 MHz,
50 CDCl3):  = 14.3 (2 CH3), 21.4 (2 CH3), 61.1 (2 CH2), 125.6 (2 Cquat),
126.1 (4 CH), 127.1 (2 CH), 128.8 (4 CH), 129.9 (4 CH), 130.6 (2
1
2
464 (3.00) of 1b
440 (3.00) of 1c
227 (40 %) of 12a
421 (79%) of 12b
8
| Journal Name, [year], [vol], 00–00
This journal is © The Royal Society of Chemistry [year]

Page 9 of 11
Organic & Biomolecular Chemistry
Table 6 Experimental details for the synthesis of the oligothiophenes
Diethyl 2,2'-(1,4-phenylene)bis(4,4'-p-tolylthiophene-5,5'-
carboxylate) (12a)
View Article Online
13 and 14.
According to the GP 227 mg (40 %) of 12a were obtained as orange
solid; decomposition at 198 °C. 1H NMR (500 MHz, CDCl3):  =
5 1.29 (t, J = 7.1 Hz, 6H), 2.41 (s, 6H) , 4.27 (q, J = 7.1 Hz, 4H) , 7.24
(d, J = 7.8 Hz, 4H) , 7.33 (s, 2H), 7.41 (d, J = 8.0 Hz, 4H), 7.70 (s,
4H). 13C NMR (125 MHz, CDCl3):  = 14.3 (2 CH3), 21.5 (2 CH3),
61.1 (2 CH2), 126.2 (2 Cquat), 126.8 (4 CH), 127.9 (2 CH), 128.7 (4
CH), 129.2 (4 CH), 132.9 (2 Cquat), 133.7 (2 Cquat), 138.1 (2 Cquat),
10 147.2 (2 Cquat), 149.7 (2 Cquat), 162.1 (2 Cquat). MALDI MS: m/z (%) =
567 ([M], 100). IR (KBr): ṽ [cm-1] = 3341 (w), 2980 (w), 2907 (w),
2864 (w), 2722 (w), 2357 (w), 2320 (w), 1678 (s), 1614 (w), 1497
(m), 1435 (m), 1412 (m), 1371 (m), 1352 (m), 1269 (s), 1242 (m),
1211 (m), 1184 (w), 1155 (w), 1132 (w), 1111 (w), 1072 (s), 1011
15 (m), 964 (m), 949 (w), 876 (m), 837 (s), 829 (m), 810 (s), 785 (m),
760 (m), 723 (w), 703 (m), 677 (w), 602 (w). UV/vis (CH2Cl2): max
() = 361 nm (43000). Emission (CH2Cl2): max (Stokes shift) = 404
nm (2900 cm-1), 425 nm. Anal. calcd. for C34H30O4S2 (566.7): C
72.06, H 5.34; Found: C 71.88, H 5.26.
dibromo
oligothiophene
[mg] (yield)
entry
oligothiophene
[mg] (mmol)
NBS
[mg] (mmol)
1
2
4430 (13.80) of 4a
278 (0.50) of 6c
7370 (41.40)
267 (1.50)
6060 (92 %) of 13
279 (78 %) of 14
Diethyl 5,5''-dibromo-2,2'-4',2"-terthiophene-5'-
60 carboxylate (13)
According to the GP 6060 mg (92 %) of 13 were obtained as white
solid; mp 105 °C. 1H NMR (500 MHz, CDCl3):  = 1.36 (t, J = 7.1
Hz, 3 H), 4.33 (q, J = 7.1 Hz, 2 H), 6.99-7.06 (m, 3 H), 7.15 (s, 1 H),
7.32 (d, J = 3.9 Hz, 1 H). 13C NMR (125 MHz, CDCl3):  = 14.4
65 (CH3), 61.6 (CH2), 113.6 (Cquat), 114.4 (Cquat), 124.7 (Cquat), 125.8
(CH), 126.8 (CH), 129.5 (CH), 130.0 (CH), 131.2 (CH), 137.2 (Cquat),
137.4 (Cquat), 139.7 (Cquat), 140.5 (Cquat), 161.7 (Cquat). EI MS (70 eV):
m/z (%) = 482 (9), 481 (11), 480 ([81Br-81Br-M]+, 60), 479 (19), 478
([81Br-79Br-M]+, 100), 477 (11), 476 ([79Br-79Br-M]+, 49), 452 (11),
70 450 (19), 448 (9), 435 ([81Br-81Br-M]+ - C2H5O, 10), 433 ([81Br-79Br-
M]+ - C2H5O, 17), 431 ([79Br-79Br-M]+ - C2H5O, 8), 408 (24), 407 (7),
406 (42), 404 (22), 400 (10), 399 (10), 398 (9), 397 (9), 371 (12), 369
(11), 354 (13), 353 (6), 352 (11), 343 (6), 341 (7), 327 (8), 326 (13),
325 (10), 324 (11), 281 (9), 279 (6), 246 (8), 245 (13), 244 (6), 233
75 (6), 201 (19), 188 (6), 186 (9), 138 (19), 123 (7), 122 (6), 101 (6),
100 (7), 93 (7), 69 (7). IR (KBr): ṽ [cm-1] = 3132 (w), 3094 (w), 2994
(w), 2913 (w), 2872 (w). 1707 (s), 1553 (m), 1510 (m), 1479 (m),
1454 (m), 1425 (m), 1366 (m), 1252 (s), 1233 (s), 1204 (m), 1179
(w), 1155 (w), 1103 (s), 1074 (m), 1053 (w), 1018 (m), 970 (m), 878
80 (m), 826 (m), 804 (s), 773 (s), 758 (m), 733 (w), 716 (w), 658 (m),
635 (w). UV/vis (CH2Cl2): max () = 319 nm (62600), 346 nm
(71200). Emission (CH2Cl2): max (Stokes shift) = 423 nm (5300 cm-
1). Anal. calcd. for C15H10Br2O2S3 (478.2): C 37.67, H 2.11; Found: C
37.70, H 2.27.
20 Diethyl 2,2'-(1,4-phenylene)bis(4,4'-(2-thienyl)-5,5'-
carboxylate) (12b)
According to the GP 421 mg (79 %) of 12b were obtained as orange
solid; decomposition at 181 °C. 1H NMR (500 MHz, CDCl3):  =
1.37 (t, J = 7.1 Hz, 6 H), 4.34 (q, J = 7.1 Hz, 4 H), 7.40 (dd, J = 5.1,
25 1.1 Hz, 2 H), 7.11 (dd, J = 5.1, 3.7 Hz, 2 H), 7.47 (s, 2 H), 7.62 (dd, J
= 3.6, 1.1 Hz, 2 H), 7.70 (s, 4 H). 13C NMR (125 MHz, CDCl3):  =
14.4 (2 CH3), 61.4 (2 CH2), 125.7 (2 Cquat), 126.7 (2 CH), 126.8 (4
CH), 127.3 (2 CH), 127.7 (2 CH), 129.2 (2 CH), 133.5 (2 Cquat),
136.3 (2 Cquat), 140.9 (2 Cquat), 147.0 (2 Cquat), 161.9 (2 Cquat). MALDI
30 MS: m/z (%) = 550 ([M], 100). IR (KBr): ṽ [cm-1] = 3109 (w), 2976
(w), 2934 (w), 2851 (w), 2667 (w), 1715 (m), 1555 (w), 1504 (w),
1449 (m), 1425 (m), 1410 (m), 1279 (w), 1242 (s), 1188 (m), 1157
(w), 1130 (w), 1103 (m), 1078 (m), 1045 (m), 1020 (m), 962 (w), 854
(m), 824 (s), 795 (m), 758 (m), 694 (s), 660 (m), 625 (w). UV/vis
35 (CH2Cl2): max () = 347 nm (37300). Emission (CH2Cl2): max
(Stokes shift) = 408 nm (4300 cm-1), 428 nm. Anal. calcd. for
C28H22O4S4 (550.7): C 61.06, H 4.03; Found: C 61.06, H 4.26.
85 Diethyl 5,5''''-dibromo-2,2'-4',2''-5'',3'''-5''',2''''-
quinquethiophene-5',2'''-dicarboxylate (14)
According to the GP 279 mg (78 %) of 14 were obtained as yellow
solid; decomposition at 187 °C. 1H NMR (500 MHz, CDCl3):  =
1.37 (t, J = 7.1 Hz, 6 H), 4.34 (q, J = 7.1 Hz, 4 H), 7.03 (d, J = 3.9
90 Hz, 2 H), 7.06 (d, J = 3.9 Hz, 2 H), 7.27 (s, 2 H), 7.59 (s, 2 H). 13C
NMR (125 MHz, CDCl3): δ = 14.4 (2 CH3), 61.5 (2 CH2), 113.5 (2
Cquat), 124.8 (2 Cquat) 125.7 (2 CH), 127.3 (2 CH), 129.6 (2 CH),
131.2 (2 CH), 137.2 (2 Cquat), 137.3 (2 Cquat), 140.3 (2x 2 Cquat), 161.7
(2 Cquat). MALDI MS: m/z (%) = 719 ([M], 5), 718 ([81Br-81Br-M],
95 20), 717 ([M], 40), 716 ([81Br-79Br-M], 85), 715 ([M], 60), 714
([79Br-79Br-M], 100), 713 ([M], 30), 712 ([M], 40), 673 ([81Br-81Br-
M] - C2H5O, 6), 672 ([M] - C2H5O, 8), 671 ([81Br-79Br-M] - C2H5O,
45), 670 ([M] - C2H5O, 20), 669 ([79Br-79Br-M] - C2H5O, 70), 668
([M] - C2H5O, 5), 667 ([M] - C2H5O, 30), 663 ([M] - C2H5O, 15). IR
100 (KBr): ṽ [cm-1] = 2980 (w), 2934 (w), 2909 (w), 2872 (w), 2357 (w),
1709 (m), 1674 (m), 1557 (m), 1508 (m), 1474 (m), 1447 (m), 1435
(m), 1423 (m), 1379 (m), 1366 (m), 1250 (s), 1231 (s), 1177 (m),
1103 (m), 1076 (m), 1042 (m), 1018 (m), 970 (m), 878 (m), 864 (m),
829 (m), 804 (m), 779 (s), 756 (m), 714 (w), 687 (w), 662 (m), 635
General Procedure (GP) for the bromination to give
oligothiophenes 13 and 14
40 A Schlenk vessel was charged with oligothiophene 4a12 or 6c
(1.00 equiv) and N-bromosuccinimide (3.00 equiv). Then acetic acid
(3.35 mL per 1.00 mmol oligothiophene 4a or 6c) and chloroform
(3.35 mL per 1.00 mmol oligothiophene 4a or 6c) were added and the
resulting solution was stirred for 12 h at room temp under exclusion
45 of light (for experimental details see Table 6). When the reaction
mixture became too viscous, additional solvent was added in the
same ratio. For workup, the reaction mixture was extracted three
times with a mixture of CH2Cl2 and saturated aqueous NaHCO3. The
combined organic layers were dried with anhydrous MgSO4 and the
50 solvent was removed at reduced pressure. Oligothiophene 13 was
further purified by recrystallization from ethanol. Oligothiophene 14
was absorbed on celite®, and purified by automated column
chromatography on fine silica gel (n-hexane/THF, gradient: 20 % to
30 % in 10 column volumes, 100 g). Further purification can easily
55 be achieved by recrystallization from hexane/THF 1/1.
105 (m). UV/vis (CH2Cl2): max ()
= 349 nm (49300). Emission
(CH2Cl2): max (Stokes shift) = 446 nm (6200 cm-1). Anal. calcd. for
C26H18Br2O4S5 (714.6): C 43.70, H 2.54; Found: C 43.47, H 2,72.
This journal is © The Royal Society of Chemistry [year]
Journal Name, [year], [vol], 00–00 | 9

Organic & Biomolecular Chemistry
Page 10 of 11
General Procedure (GP) for the Sonogashira coupling of the
brominated oligothiophene 13 and 14 with ethyl heptynoic
acid to give oligothiophene substrates 15 and 16
96.2 (2 Cquat), 124.6 (2 Cquat), 125.2 (2 CH), 125.2 (2 CH), 127.3 (2
CH), 129.5 (2 CH), 132.2 (2 Cquat), 135.8 (2 Cquat), 13V7i.e3w(A2rtCiclqeuaOt)n,line
140.3 (2 Cquat), 140.8 (2 Cquat), 161.8 (2 Cquat), 173.5 (2 Cquat). EI MS
55 (70 eV): m/z (%) = 862 (27), 861 ([M]+, 36), 860 (77), 815 (15), 710
(30), 709 (40), 708 (100), 663 (14), 295 (17), 294 (23), 287 (14), 281
(14), 275 (15), 269 (17), 260 (17), 88 (15), 85 (15), 69 (14), 57 (17),
55 (27), 45 (13), 44 (31), 43 (23), 41 (23). IR (KBr): ṽ [cm-1] = 2976
(w), 2934 (w), 2905 (w), 2868 (w), 2837 (w), 1730 (s), 1707 (s),
60 1682 (m), 1557 (m), 1510 (m), 1478 (m), 1460 (m), 1427 (m), 1373
(m), 1352 (m), 1271 (m), 1252 (s), 1231 (s), 1175 (s), 1148 (m), 1105
(s), 1074 (m), 1022 (m), 937 (w), 864 (w), 801 (s), 756 (m), 650 (m).
UV/vis (CH2Cl2): max () = 366 nm (65400). Emission (CH2Cl2): max
(Stokes shift) = 447 nm (5100 cm-1). Anal. calcd. for C44H44O8S5
65 (861.1): C 61.37, H 5.15; Found: C 61.22, H 5.15.
A
25 mL Schlenk vessel was charged with Pd(PPh3)4 (58 mg,
5 0.08 mmol), CuI (19 mg, 0.10 mmol), PPh3 (26 mg, 0.10 mmol) and
1.00 mmol of the brominated oligothiophene 13 or 14 (for
experimental details see Table 8). Then THF (5 mL), NEt3 (304 mg,
3.00 mmol) and ethyl heptynoate (463 mg, 3.00 mmol) was added
and the resulting solution was stirred for 12 h at 60 °C. For the
10 synthesis of compound 16 a five times higher amount of THF was
used and the reaction was stirred for 24 h. For workup, the reaction
mixture was absorbed on celite®, and purified by automated column
chromatography on fine silica gel (n-hexane/THF, gradient: 25 % to
35 % in 10 column volumes, 100 g).
15 Table 8 Experimental details for the synthesis of the oligothiophenes
15 and 16.
Notes and references
a Lehrstuhl für Organische Chemie, Institut für Organische Chemie und
Makromolekulare Chemie, Heinrich-Heine-Universität Düsseldorf,
Universitätsstraße 1, D-40225, Düsseldorf, Germany. Fax: ++49 (0)211
70 8114324; Tel: ++49 (0)211 8112298; E-mail: ThomasJJ.Mueller@uni-
duesseldorf.de
entry
dibromo oligothiophene
[mg] (mmol)
oligothiophene
[mg] (yield)
1
2
478 (1.00) of 13
715 (1.00) of 14
460 (96 %) of 15
850 (99 %) of 16
† Electronic Supplementary Information (ESI) available: Spectra (1H
NMR, 13C NMR, UV/vis, fluorescence) of compounds 6, 8, 10 and 12-16.
Diethyl 5,5''-bis(7-ethoxy-7-oxohept-1-ynyl)-2,2'-4',2''-
terthiophene-5'-carboxylate (15)
75 1 S. Gronowitz, In “Thiophene and Its Derivatives”, Part 1, S.
Gronowitz, ed, Wiley & Sons, New York, 1985, 88.
According to the GP 460 mg (96 %) of 15 were obtained as yellow
1
2
Canagliflozin: E. C. Chao, Drugs of the Future, 2011, 36, 351; DS-1:
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20 solid; mp 75 °C. H NMR (500 MHz, CDCl3):  = 1.26 (t, J = 7.1 Hz,
6 H), 1.34 (t, J = 7.1 Hz, 3 H), 1.56 – 1.72 (m, 4 H), 1.72 – 1.79 (m, 4
H), 2.35 (t, J = 7.3 Hz, 4 H), 2.47 (m, 4 H), 4.14 (q, 3J = 7.1 Hz, 4
H), 4.31 (q, J = 7.1 Hz, 2 H), 7.03 (d, J = 3.8 Hz, 1 H), 7.07 (d, J =
3.9 Hz, 1 H), 7.11 (d, J = 3.8 Hz, 1 H), 7.20 (s, 1 H), 7.42 (d, J = 3.9
25 Hz, 1 H). 13C NMR (125 MHz, CDCl3):  = 14.4 (3 CH3), 19.7 (2
CH2), 24.4 (2 CH2), 28.0 (2 CH2), 34.0 (2 CH2), 60.5 (CH2), 61.5 (2
CH2), 95.3 (2 Cquat), 96.3 (2 Cquat), 125.2 (CH), 127.1 (CH), 129.1
(CH), 131.2 (CH), 132.2 (CH), 135.7 (2 Cquat), 136.1 (Cquat), 140.0 (2
Cquat), 140.9 (2 Cquat), 161.7 (Cquat), 173.5 (2 Cquat). EI MS (70 eV):
30 m/z (%) = 626 (21), 625 ([M]+, 39), 624 (100), 581 (9), 580 (18), 579
(49), 578 (15), 551 (11), 536 (8), 509 (10), 491 (9), 478 (10), 477
(21), 231 (13), 218 (9), 217 (9), 203 (10), 197 (8), 196 (10), 195 (8),
191 (8), 183 (9), 171 (12), 145 (9). IR (KBr): ṽ [cm-1] = 2976 (w),
2934 (w), 2903 (w), 2870 (w), 2220 (w), 1728 (w), 1705 (m), 1555
35 (w), 1506 (w), 1470 (w), 1447 (w), 1418 (w), 1368 (w), 1312 (w),
1252 (s), 1229 (s), 1177 (m), 1103 (s), 1071 (m), 1047 (w), 1020 (m),
945 (w), 876 (w), 829 (w), 810 (w), 787 (s), 756 (m), 735 (w), 662
(w). UV/vis (CH2Cl2): max () = 340 nm (33200), 363 nm (34000).
Emission (CH2Cl2): max (Stokes shift) = 442 nm (4900 cm-1). Anal.
40 calcd. for C33H36O6S3 (624.8): C 63.43, H 5.81; Found: C 63.34, H
6.08.
80
85
3
R. Otero, J. M. Gallego, A. L. Vázquez de Parga , N. Martín and R.
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105
110
115
4
5
Diethyl 5,5''''-bis(7-ethoxy-7-oxohept-1-ynyl)-2,2'-4',2''-
5'',3'''-2''',2''''-quinquethiophene-5',2'''-dicarboxylate (16)
According to the GP 850 mg (99 %) of 16 were obtained as orange
1
45 solid; mp 68 °C. H NMR (500 MHz, CDCl3):  = 1.26 (t, J = 7.1 Hz,
6 H), 1.36 (t, J = 7.1 Hz, 6 H), 1.72 – 1.61 (m, 4 H), 1.87 – 1.73 (m, 4
H), 2.36 (t, J = 7.3 Hz, 4 H), 2.48 (t, J = 6.9 Hz, 4 H), 4.14 (q, J = 7.1
Hz, 4 H), 4.34 (q, J = 7.1 Hz, 4 H), 7.04 (d, J = 3.8 Hz, 2 H), 7.14 (d,
J = 3.8 Hz, 2 H), 7.30 (s, 2 H), 7.58 (s, 2 H). 13C NMR (125 MHz,
50 CDCl3):  = 14.4 (2 CH3), 14.4 (2 CH3), 19.7 (2 CH2), 24.4 (2 CH2),
28.0 (2 CH2), 34.0 (2 CH2), 60.5 (2 CH2), 61.5 (2 CH2), 74.0 (2 Cquat),
10 | Journal Name, [year], [vol], 00–00
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Page 11 of 11
Organic & Biomolecular Chemistry
3378; C. Waldauf, P. Schilinsky, M. Perisutti, J. Hauch and C. J.
Brabec, Adv. Mater., 2003, 15, 2084.
Fiesselmann and F. Thoma, Chem. Ber., 1956, 89, 1907; H.
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