Heteroacenes Bearing the Pyrimidine Scaffold: Synthesis, Photophysical and Electrochemical Properties

Article abstract of DOI:10.1002/ejoc.201501450

A convenient synthetic route to novel 7-substituted benzo[f]thieno[3,2-h]quinazoline and 8-substituted benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidine systems, bearing the fused pyrimidine ring, has been advanced. A commercially available 5-bromopyrimidine was used as the starting material to obtain various polycyclic systems through the sequence of nucleophilic aromatic substitution of hydrogen (the S_N^H reaction), Suzuki cross-coupling and oxidative photocyclization. Evidence for the structure of benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidines has been obtained by X-ray crystallographic analysis. Molecular orbital calculations (DFT), as well as redox and optical measurements for all new compounds have been performed. The data show that the reported polycyclic systems have potential for use in organic electronic applications. A convenient route to a new class of diazapyrene systems, bearing the fused pyrimidine ring, is presented along with their optoelectronic properties. The photophysical and electrochemical properties of these thienoazaacenes have been investigated by UV/Vis absorption and photoluminescence spectrophotometry. Cyclic voltammetry, and X-ray crystallography studies have also been performed.

Full text of DOI:10.1002/ejoc.201501450

DOI: 10.1002/ejoc.201501450
Full Paper
Azapyrenes
Heteroacenes Bearing the Pyrimidine Scaffold: Synthesis,
Photophysical and Electrochemical Properties
Egor V. Verbitskiy,*[a,b] Ekaterina M. Cheprakova,[a,b] Nadezhda I. Makarova,[c]
Igor V. Dorogan,[c] Anatoly V. Metelitsa,[c] Vladimir I. Minkin,[c,d] Pavel A. Slepukhin,[a,b]
Tatyana S. Svalova,[b] Alla V. Ivanova,[b] Alisa N. Kozitsina,[b] Gennady L. Rusinov,[a,b]
Oleg N. Chupakhin,[a,b] and Valery N. Charushin[a,b]
Abstract: A convenient synthetic route to novel 7-substituted Suzuki cross-coupling and oxidative photocyclization. Evidence
benzo[f]thieno[3,2-h]quinazoline and 8-substituted benzo[g,h]- for the structure of benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidines
dithieno[2,3-e:3′,2′-j]perimidine systems, bearing the fused pyr- has been obtained by X-ray crystallographic analysis. Molecular
imidine ring, has been advanced. A commercially available 5- orbital calculations (DFT), as well as redox and optical measure-
bromopyrimidine was used as the starting material to obtain ments for all new compounds have been performed. The data
various polycyclic systems through the sequence of nucleo- show that the reported polycyclic systems have potential for
H
philic aromatic substitution of hydrogen (the SN reaction), use in organic electronic applications.
Introduction
π-Conjugated polycyclic aromatic compounds and their hetero-
cyclic analogues have attracted enormous interest due to their
unique electronic and optoelectronic properties as well as their
potential applications in organic electronics.[1] In particular, aza-
pyrenes and their metal complexes are rather promising for the
construction of electroluminescent materials (Figure 1).[2] Unfor-
tunately, data concerning the effects of thiophene annulation
on azapyene systems are not available. On the other hand, sub-
stituted pyreno[4,5-b:10,9-b′]dithiophenes have been used suc-
cessfully as semiconductors in organic field-effect transistors
(Figure 1).[3]
Figure 1. Azapyrenes and pyrenes fused with thiophene rings.
In a continuation of our studies in the field of fused pyrimid-
ines, we wish to report the synthesis and characterization of
novel heteroacene systems (Figure 2), bearing the fused pyrim-
idine ring; namely, 7-substituted benzo[f]thieno[3,2-h]quin-
azoline (BTQ) and 8-substituted benzo[g,h]dithieno[2,3-e:3′,2′-
j]perimidines (BDP).
[a] Postovsky Institute of Organic Synthesis, Ural Branch, Russian Academy of
Sciences,
Figure 2. Chemical structures of benzo[f]thieno[3,2-h]quinazoline (BTQ) and
8-substituted benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidines (BDP).
S. Kovalevskoy Str. 20, Ekaterinburg, 620137, Russia
E-mail: Verbitsky@ios.uran.ru
www.ios.uran.ru
[b] Ural Federal University named after the First President of Russia B. N.
Eltsin,
Results and Discussion
Mira Str. 19, Ekaterinburg, 620002, Russia
Synthesis
[c] Institute of Physical and Organic Chemistry, Southern Federal University,
Stachki Av. 194/2, 344090 Rostov on Don, Russia
[d] Russia Southern Scientific Centre of the Russian Academy of Sciences,
Chekhov St. 41, 344006 Rostov on Don, Russia
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/ejoc.201501450.
It has been shown that 5-bromopyrimidine is an appropriate
starting material to incorporate the thienyl fragment at position
C(4) of the pyrimidine ring by using the methodology of nu-
H
cleophilic aromatic substitution of hydrogen (the SN reac-
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Scheme 1. Synthesis of 7-substituted benzo[f]thieno[3,2-h]quinazoline 5a–c.
tion).[4] It has also been established that 5-bromo-4-(het- character of the substituent R.[6] The moderate yields of
ero)arylpyrimidines react easily with a variety of (hetero)aryl- benzo[f]thieno[3,2-h]quinazolines 5a–c can be explained by the
substituted boronic acids under Pd-catalyzed microwave-as- poor solubility in acetonitrile of both the starting pyrimidines
sisted conditions.[5] 5-(4-R-phenyl)-4-(2-thienyl)pyrimidines 4a– 4a–c and the products 4b and 4d, as well as by radical-medi-
c, which are regarded as key synthetic intermediates for the ated side-reactions.
preparation of benzo[f]thieno[3,2-h]quinazoline systems 5a–c,
have been obtained by using the easily available 5-bromo-4-
(thiophen-2-yl)pyrimidine (2) (Scheme 1). The transformation of
2 into 5-aryl-4-thiophen-2-yl-substituted pyrimidines 4a–c is
similar to the microwave-assisted Suzuki cross-coupling reac-
tion, proceeding in dioxane/H2O mixture (4:3) (Scheme 1). The
structures of 4,5-di(hetero)aryl pyrimidines 4a and 4c have
been established unequivocally by X-ray crystallography analy-
sis (see Figures S1 and S2 in the Supporting Information).
Compounds 4a–c were subjected to oxidative photocycliza-
tion with iodine in acetonitrile without any other additives. The
reaction mixtures were irradiated at room temperature with a
UV lamp to cause photocyclization into benzo[f]thieno[3,2-
h]quinazolines 5a–c, which were obtained in moderate yields
(Scheme 1, Table 1). The progress of the photocyclization of
4a–c was monitored by GC–MS analysis. Samples were taken
from the reaction mixture at defined time intervals until the
starting pyrimidine 4a (4b or 4c) had been consumed. It should
be noted that reaction times increased in the order tBu < H <
CF3, which correlates with the enhanced electron-withdrawing
Attempts to react 5a–c with thiophene in CF3COOH with
subsequent oxidation to obtain the SN products 6a–c failed.
H
No traces of 4-thiophen-2-yl-7-R-benzo[f]thieno[3,2-h]quinaz-
olines 6a–c were observed in the reaction mixtures by GC–MS
analysis (Scheme 1). The low reactivity of polycyclic compounds
5a–c towards thiophene is probably due to the presence of the
electron-donating thiophene ring in the fused system.[5a]
To prepare 8-substituted benzo[gh]dithieno[2,3-e:3′,2′-j]per-
imidines 9a–c, we used another approach involving nucleo-
H
philic aromatic substitution of hydrogen (the SN reaction),
Suzuki cross-coupling, and oxidative photocyclization. As the
first step, 5-bromo-4,6-di(thiophen-2-yl)pyrimidine (7) was ob-
tained in high yield (70 %) by reacting 5-bromo-4-(thiophen-2-
yl)pyrimidine (2) with thienyllithium. The latter was prepared
according to a modified procedure[7] from thiophene and nBuLi.
Table 1. Oxidative photocyclization of 4,5-di(het)arylpyrimidines 4a–c and
4,5,6-tri(het)arylpyrimidines 8a–c.
Entry
Pyrimidine
R
Reaction time
[h]
Product
Isolated
yield [%]
1
2
3
4
5
6
4a
4b
4c
8a
8b
8c
H
30
25
70
130
30
150
5a
5b
5c
9a
9b
9c
43
49
72
18
51
32
tBu
CF3
H
tBu
CF3
Scheme 2. Synthesis of 8-substituted benzo[g,h]dithieno[2,3-e:3′,2′-j]perim-
idines 9a–c.
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The crystal structure of 7 was confirmed by X-ray diffraction corresponding 4,5,6-tri(hetero)arylpyrimidines 8a–c were ex-
analysis (see Figure S3).
posed to UV irradiation under similar reaction conditions
(Scheme 2, Table 1). It should be noted that this process pro-
ceeds as a double photocyclization; molecular ions coinciding
with molecular weights of intermediates 6a–c were not de-
tected in the reaction mixtures. Moreover, the structure 9b was
established unequivocally by X-ray diffraction analysis (see Fig-
ure 3).
According to the XRD data, compound 9b crystallized in the
centrosymmetric space group. The polycyclic system is planar
within limits of 0.05 Å. The lengths of C–C bonds in the polyaro-
matic system range from d(C19–C20) = 1.332(5) Å to d(C13–
C14) = 1.456(5) Å. For 9b, no herringbone structure is observed
and the arrangement of the molecules can basically be de-
scribed as a one-dimensional slipped-stack, with the interfacial
distances of adjacent molecules being 3.45 and 3.48 Å (see Fig-
ure 4). The molecules are packed in the plane nearest to [33
–18 6] Miller plane. No shortened contacts in the molecular
packing were observed.
Bromo compound 7 was further subjected to the Suzuki
cross-coupling reaction with 4-R-phenylboronic acids 3a–c un-
der microwave irradiation (170 °C, 20 min), thus leading to 5-(4-
R-phenyl)-4,6-di(thiophen-2-yl)pyrimidines 8a–c in good yields
(87–98 %) (see Scheme 2).
Finally, we prepared 8-substituted benzo[g,h]dithieno[2,3-
e:3′,2′-j]perimidines 9a–c in 32–51 % yields. To obtain 9a–c, the
Photophysical and Electrochemical Properties
The optical properties of 5-bromo-4,6-dithienylpyrimidine (7),
4,5,6-tri(hetero)arylpyrimidines 8a–c, and
8-substituted
benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidines 9a–c were investi-
gated by UV/Vis and photoluminescence (PL) spectroscopy in
CH2Cl2 solutions at room temperature. The data obtained are
summarized in Table 2 and are given in Figures 5, 6 and S4–S6
in the Supporting Information.
Figure 3. Mercury[8] representation of the X-ray crystal structure of 9b with
thermal ellipsoids of 50 % probability.
Table 2. UV/Vis and photoluminescence (PL) data.
Compound[a]
Absorption
Photoluminescence
[b]
λmax [nm]
Excitation λmax Emission
ΦF
(ε, 104
M
–1 cm–1
)
[nm]
λmax [nm]
7
340 (2.59),
278 (2.17)
336 (1.86),
276 (1.48)
336 (2.01),
276 (1.64)
336 (2.51),
276 (2.01)
381 (2.07),
361 (2.13),
302 (2.99),
254 (2.20)
387 (2.04),
367 (2.10),
303 (3.02),
257 (2.56)
380 (1.86),
361 (1.97),
305 (3.36),
257 (1.99)
–
–
–
8a
8b
8c
9a
337,
275
337,
275
337,
275
381,
362,
303,
254
387,
366,
303,
262
380,
360,
305,
262
396
405
388
0.07[c]
0.06[c]
0.05[c]
0.11[d]
383,
405,
428,
450[e]
389,
411,
434,
460[e]
381,
403,
426,
450[e]
9b
9c
0.13[d]
0.10[d]
[a] All spectra were recorded in CH2Cl2 solutions at room temperature
at c = 2.0 × 10–5 for UV/Vis spectra and at c = 2.0 × 10–5
(for 8a–c) to
2.0 × 10–6
(for 9a–c) for PL spectra. [b] Fluorescence quantum yield ( 10 %)
determined relative to quinine bisulfate in 0.05 H2SO4 as standard (ΦF
0.52).[9] [c] Excitation at 350 nm. [d] Excitation at 365 nm. [e] Shoulder.
M
M
Figure 4. Molecular packing for 9b in the plane [1 0 0] (a, top) and in the
plane [33 –18 6] (b, bottom). The interfacial distances are also given. Distan-
ces are in Å.
M
M
=
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roacenes 9a–c, have two structured long-wave absorption
bands with maxima in the regions of 361–367 (ε = 19700–
21300
M M
–1 cm–1) and 380–387 (18600–20700 –1 cm–1) nm
(Table 2). Several maxima in the UV spectra, resulting from vi-
bronic coupling of the π–π* transition (Figure 6, Figures S5 and
S6) is a common feature of azapyrenes, which have limited con-
formational disorder as a result of their fused structures.[10]
It has been found that compounds 9a–c exhibit photolumi-
nescent properties. The structured fluorescence band has three
peaks and shoulders at 381–389, 403–411, 426–434, and 450–
460 nm (Table 2, Figure 6, Figures S5 and S6). The electron-
withdrawing CF3 group causes a hypsochromic shift (1–2 nm)
of the absorption and fluorescence maxima (9c), whereas the
electron-donating tBu group causes a bathochromic shift
(6 nm) of the absorption and fluorescence maxima (9b) com-
pared with those of unsubstituted analogue 9a (Table 2).
The fluorescence efficiency of 9a–c (ꢀ = 0.1–0.13) is approxi-
mately two times higher than that for the parent 4,5,6-tri(het-
ero)arylpyrimidines 8a–c (ꢀ = 0.05–0.07) (Table 2). The most
probable reason for the increase in fluorescence quantum
yields is associated with an enhanced structural rigidity of the
polycondensed heteroaromatic molecules, which decreases the
probability of nonradiative processes due to limitations in the
molecular vibrational-rotational modes.
Figure 5. UV/Vis (1–3), fluorescence emission (λex = 335 nm) (4–6), and fluores-
cence excitation (λobs = 400 nm) (7–9) spectra of 8a–c in dichloromethane at
room temperature.
Cyclic voltammetry (CV) of benzo[g,h]dithieno[2,3-e:3′,2′-
j]perimidines 9a–c was performed to determine their redox po-
tentials (see Table 3). The cyclic voltammograms shown in Fig-
ures S7–S9 demonstrate the irreversible character of oxidation
of azapyrenes 9a–c. In addition, an increase in the oxidation
current peak on recycling appears to indicate the tendency of
these compounds to undergo polymerization (see Figures S10–
S12). Given that no cathodic behavior of azapyrenes 9a–c could
be recorded by CV, their excited state reduction potentials (cor-
responding to the LUMO energy levels) were calculated by add-
ing the energy gap Eg (estimated from the long-wavelength
absorption edge of the absorption spectra recorded in CH2Cl2
solution) to the HOMO energy values (Table 3).
Figure 6. UV/Vis (1), fluorescence emission (λex = 365 nm) (2), and fluores-
cence excitation (λobs = 400 nm) (3) spectra of 9a in dichloromethane at
room temperature.
The positions of the observed maxima do not depend on
the substituent R in the phenyl moiety. The similarity of the
spectral characteristics of 4,5,6-tri(hetero)arylpyrimidines 8a–c
to those of 5-bromo-4,6-dithienylpyrimidine 7 can be attributed
to the nonplanar structure of compounds 8a–c caused by the
out-of-plane position of the 5-phenyl ring due to steric factors.
In contrast to 7, pyrimidines 8a–c show fluorescence in di-
chloromethane solution at room temperature with quantum
yields of 0.05–0.07 (Figure 5, Table 2). The observed fluores-
cence excitation spectra of 8a–c are in good agreement with
the absorption spectra. The position of the maxima for fluores-
cence bands of 5-(4-R-phenyl)-4,6-dithiophen-2-yl-pyrimidines
8a–c depends on the substituent R in the 5-phenyl moiety. The
electron-withdrawing CF3 group initiates a hypsochromic shift
(8 nm) of the fluorescence band maximum (8c), whereas incor-
poration of the electron-donating tBu group resulted in a bat-
Table 3. Electrochemical properties of benzo[g,h]dithieno[2,3-e:3′,2′-j]per-
imidines 9a–c.
onset[a]
calc
Entry
Pyrimidine Eox
EHOMO [eV] ELUMO
[eV][b]
Eg [eV][c]
1
2
3
9a
9b
9c
0.3
0.7
0.58
–4.92
–5.32
–5.20
–1.67
–2.12
–1.94
3.25
3.20
3.26
[a] Eoxonset: Onset oxidation potential (vs. Ag/AgCl reference electrode). [b]
calc
ELUMO
= EHOMO + Eg. [c] Energy gap estimated from the onset of the ab-
sorption spectra recorded in CH2Cl2 solution.
The optical band gap values of 3.20–3.26 eV for 9a–c appear
to be typical for similar semiconducting thienoacenes (e.g., the
optical band gaps of 3.33 eV for DTNN and 2.97 eV for
DTNQ).[11] LUMO levels calculated from the electrochemical
HOMO plus the optical band gap are –1.67 eV for 9a and
–2.12 eV for 9b. Thus, incorporation of tBu electron-donating
group leads to a much larger reduction in LUMO (0.69 eV) than
incorporation of the CF3 electron-acceptor substituent. More-
hochromic shift (9 nm) of the fluorescence band maximum (8b)
PI
relative to that of the unsubstituted analogue 8a (λmax
=
396 nm).
Compared with sterically nonrigid structures 8a–c, the prod- over, the presence of the CF3 group in the structure of aza-
ucts of their photocyclization, novel polycyclic aromatic hete- pyrenes increases the energy gap Eg. This finding suggests that
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the electron-acceptor content in structurally similar compounds
could lead to very low LUMO levels and may be a useful strat-
egy for the design of n-type semiconductors.
Computational Studies
Quantum chemical calculations have been performed to esti-
mate spectral properties of compounds 7, 8a–c, and 9a–c. The
predicted excitation energies (Table 4) indicate that variation of
substituents in 8a–c and 9a–c does not change significantly the
position of the longest wavelength absorption maxima. Com-
pared with the parent compounds 8a and 9a, calculations re-
veal a very weak bathochromic shift of the absorption maxima
for tBu substituted derivatives 8b and 9b, and a hypsochromic
shift for CF3-substituted derivatives 8c and 9c, which is in a
good agreement with the experimental data.
Figure 7. The frontier molecular orbitals of 7, 8a, 9a involved in the S0–S1
and S0–S2 transitions as calculated by the PCM-B3LYP/6-311+G(d,p) method
(0.03 a.u. contour threshold has been used).
Table 4. Excitation energy Eex [eV], oscillator strength f of the first three sin-
glet transitions, frontier orbital energies EHOMO, ELUMO [eV] and the energy
gap ΔE [eV] of compounds 7, 8a–c, and 9a–c according to TD PCM-B3LYP/
6-311+G** calculations in CH2Cl2 solution.
HOMO–2 of 8a–c contains contributions of π-orbitals of the 5-
phenyl substituent, whereas that of 7 includes π-orbitals of the
thiophene fragments (Figure 7).
Eex
f
EHOMO
ELUMO
ΔE
7
S0–S1
S0–S2
S0–S3
S0–S1
S0–S2
S0–S3
S0–S1
S0–S2
S0–S3
S0–S1
S0–S2
S0–S3
S0–S1
S0–S2
S0–S3
S0–S1
S0–S2
S0–S3
S0–S1
S0–S2
S0–S3
3.4925
3.8428
3.8857
3.5771
3.7191
3.8368
3.5553
3.6437
3.8415
3.5756
3.817
0.5063
0.0158
0.0415
0.6139
0.0014
0.0159
0.459
0.1442
0.0152
0.5808
0.0174
0.0129
0.2155
0.2757
0.0275
0.2505
0.2373
0.0481
0.2325
0.2079
0.0135
–6.59
–2.51
4.08
It has been established that structural relaxation of 8a–c in
the first singlet excited state is accompanied by a change of
the torsion angles between the planes of pyrimidine, thio-
phene, and phenyl fragments, since molecular structures of
these compounds become flatter (Figure S13). Similar structural
changes take place in the S1 state of 7 (Figure S14). At the
same time, the excited state relaxation of 9a–c is manifested in
changes in the bond lengths within the polycyclic structures
(Figure S15).
As expected, theoretically predicted energies of the HOMO,
the LUMO, and the energy gap (Table 4) differ from those that
were obtained experimentally, due to approximate character of
the exchange-correlation functional employed. Nevertheless,
the trends in the series of 9a–c, calculated theoretically and
determined experimentally, appear to be the same from a quali-
tative point of view.
8a
8b
8c
9a
9b
9c
–6.50
–6.47
–6.57
–6.37
–6.31
–6.58
–2.39
–2.37
–2.45
–2.61
–2.57
–2.77
4.11
4.10
4.12
3.76
3.74
3.81
3.836
3.3953
3.4169
3.7272
3.3517
3.3831
3.721
3.4188
3.4473
3.7112
Conclusions
According to the results obtained (Table 4, Figure 7), the
longest wavelength absorption band of 9a–c originates from
the two intense π–π* electronic transitions S0–S1 and S0–S2
with the main contribution of HOMO–LUMO and HOMO-1–
LUMO, respectively.
A convenient synthetic route to novel heteroacenes bearing the
fused pyrimidine ring has been advanced. A commercially avail-
able 5-bromopyrimidine was used to obtain various diazacyclo-
penta[l]phenanthrene and 8-substituted benzo[g,h]dithieno-
The most intense S0–S1 π–π* transition (HOMO–LUMO) gives [2,3-e:3′,2′-j]perimidine systems through the sequence of reac-
rise to a longest wavelength absorption peak in the absorption tions involving nucleophilic aromatic substitution of hydrogen
H
spectra of 8a–c. HOMO and LUMO molecular orbitals of 8a–c (the SN reaction), Suzuki cross-coupling, and oxidative photo-
are localized on the thiophene and pyrimidine fragments, and cyclization. X-ray crystallography data for novel azapyrenes and
practically do not include contribution from the phenyl substit- intermediate pyrimidines have also been obtained.
uent that is arranged perpendicular to them. The less intense
S0–S2 transitions (HOMO-2–LUMO) for these compounds may
be assigned to n–π* character.
In summary, it is noteworthy that all compounds studied can
be regarded as potential organic semiconductors; however, ad-
ditional modifications are required to improve their characteris-
Analogous electronic transitions determine the longest tics. Planned syntheses will develop long-chain push-pull com-
wavelength absorption band of 5-bromo-4,6-dithienylpyrim- pounds on the basis of a benzo[g,h]dithieno[2,3-e:3′,2′-j]per-
idine 7. However, molecular orbitals of 7 and 8a–c involved imidine ring system with stronger donating- and electron-with-
in these transitions have noticeable differences. In particular, drawing groups, attached to C(8) position.
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counter electrode were employed. The measurements were per-
formed in anhydrous CH2Cl2 solution containing the sample com-
pound (2 mM) and tetrabutylammonium perchlorate (0.1 M) as the
Experimental Section
General: All reagents and solvents were obtained from commercial
sources and dried by using standard procedures before use. 5-
Bromo-4-(thien-2-yl)pyrimidine (2) was prepared according to a re-
ported method.[5a] The solvents (1,4-dioxane and H2O) for the mi-
crowave-assisted Suzuki cross-coupling reaction were deoxygen-
ated by bubbling argon for 1 h.
1H, 19F, and 13C NMR spectra were recorded with Bruker DRX-400
and Avance-500 instruments using Me4Si and C6F6 as an internal
standards. Elemental analysis was conducted with a Eurovector EA
3000 automated analyzer. Melting points were determined with
Boetius combined heating stages and were not corrected.
supporting electrolyte at a scan rate of 100 mV/s. The potential
of the reference electrode was calibrated by using the ferrocene/
ferrocenium redox couple (Fc/Fc+), which has a known oxidation
potential of +5.1 eV vs. vacuum for ferrocene.[14] The HOMO energy
values were estimated from the onset potentials (Eoxonset) of the
first oxidation event according to Equation (1) where E1/2(Fc/Fc+) is
the half-wave potential of the Fc/Fc+ couple against the Ag/AgCl
electrode.
onset
EHOMO [eV] = –[Eox
– E1/2(Fc/Fc+) + 5.1]
(1)
The GC–MS analysis of all samples was carried out with an Agilent
GC 7890A MS 5975C Inert XL EI/CI GC–MS spectrometer with a
quadrupole mass-spectrometric detector with electron ionization
(70 eV) and scan over the total ionic current in the range m/z 20–
1000 and a quartz capillary column HP-5MS (30 m × 0.25 mm, film
thickness 0.25 mm). Helium served as a carrier gas, the split ratio
of the flow was 1:50, and the consumption through the column
was 1.0 mL min–1; the initial temperature of the column was 40 °C
(storage 3 min), programming rate was 10 °C min–1 to 290 °C (stor-
age 20 min), the temperature of the evaporator, source, quadrupole,
and transition chamber was 250, 230, 150, and 280 °C, respectively.
Solutions of the samples with a concentration of 3–4 mg mL–1 were
prepared in THF. Samples of 1 mL of the obtained solutions were
analyzed.
Electron absorption spectra were obtained with an Agilent 8453
spectrophotometer, fluorescence spectra were obtained with a Var-
ian Cary Eclipse fluorescence spectrophotometer. UV/Vis and fluo-
rescence spectra were recorded in CH2Cl2 solutions at room temper-
ature at c = 2.0 × 10–5
M
using standard 1 cm quartz cells. Fluores-
cence quantum yield ( 10 %) was determined relative to quinine
bisulfate in 0.05
H2SO4 as standard (ΦF = 0.52).[9]
M
UV/Vis spectra were recorded for 2 × 10–5
toluene and acetonitrile
solutions with a Varian Cary 100 spectrophotometer. Photolumines-
cent spectra were recorded for 1 × 10–6
toluene and acetonitrile
M
M
solutions with a Varian Cary Eclipse fluorescence spectrophotome-
ter.
IR spectra of samples (solid powders) were recorded with a Spec-
trum One Fourier transform IR spectrometer (Perkin–Elmer)
equipped with a diffuse reflectance attachment (DRA) in the fre-
quency range 3300–450 cm–1. Spectrum processing and band in-
tensity determination were carried out with the software supplied
with the spectrometer.
Flash-column chromatography was carried out with Lancaster silica
gel 0.040–0.063 mm (230–400 mesh), eluting with ethyl acetate/
hexane. The progress of reactions and the purity of compounds
were monitored by TLC analysis on Sorbfil plates (Russia); the spots
were visualized with UV light (λ = 254 or 365 nm).
Microwave experiments were carried out in a Discover unimodal
microwave system (CEM, USA) with a working frequency of
2.45 GHz; the power of microwave radiation ranged from 0 to
300 W. The reactions were carried out in a 10 mL reaction tube
with a hermetic Teflon cork. The temperature of the reaction was
monitored with an inserted IR sensor by measuring the external
surface of the reaction vessel.
Computational Methods: Geometry optimizations of compounds
7, 8a–c, and 9a–c in the ground state were performed with the
B3LYP hybrid functional[15] and 6-311+G** basis set using the
GAUSSIAN 09 suite.[16] Salvations effects were accounted for with
the use of the PCM model[17] with the solvent parameters of di-
chloromethane (ε = 8.93). The vertical excitation energies of the
singlet–singlet transition and optimized structures of 7, 8a–c, and
9a–c in the S1 state were calculated within the TDDFT methodology
at the same level of theory.
The light source used for the photochemical reactions was a Hano-
via medium pressure mercury lamp (PC 451050/805221).
Suitable crystals of 4a, 4c, and 7 were selected and XRD analyses
were performed with an Xcalibur diffractometer on standard proce-
dure (Mo-Kα graphite-monochromated irradiation, ω-scanning with
1° steps). The empirical absorption correction was applied. Using
Olex2,[12] the structure was solved with the SHELXS[13] structure
solution program and refined with the SHELXL[13] refinement pro-
gram using full-matrix least-squares on F2 method in anisotropic
approximation for non-hydrogen atoms. Crystal data and data col-
lection parameters are summarized in Table S1 (see the Supporting
Information).
General Procedure for the Syntheses of 5-(4-R-phenyl)-4-(2-thi-
enyl)pyrimidines 4a–c: A solution of K2CO3 (346 mg, 2.5 mmol) in
H2O (3 mL) was added to a mixture of 5-bromo-4-thiophen-2-yl-
pyrimidine (2) (121 mg, 0.5 mmol), phenylboronic [4-tert-butylphen-
ylboronic acid or 4-(trifluoromethyl)phenylboronic] acid (0.6 mmol)
and Pd(PPh3)4 (29 mg, 5 mol-%) in 1,4-dioxane (4 mL). The resulting
mixture was irradiated in a microwave apparatus at 170 °C (250 W)
for 20 min. The solvent was then distilled off in vacuo, and the
residue was purified by flash column chromatography (hexane/
ethyl acetate, 1:3) to afford the desired cross-coupling products (4a,
4b, and 4c).
CCDC 1436740 (for 4a), 1436737 (for 4c), 1436739 (for 7), and
1436738 (for 9b) contain the supplementary crystallographic data
for this paper. These data can be obtained free of charge from The
Cambridge Crystallographic Data Centre.
5-Phenyl-4-(thiophen-2-yl)-pyrimidine (4a): Yield 93 %; pale-yel-
1
low solid; m.p. 104–106 °C. H NMR (500 MHz, CDCl3): δ = 6.81 (dd,
J = 3.8, 0.7 Hz, 1 H, H-3′), 6.86 (dd, J = 5.0, 3.8 Hz, 1 H, H-4′), 7.34–
7.39 (m, 2 H, Ph), 7.41 (dd, J = 5.0, 0.7 Hz, 1 H, H-5′), 7.47–7.52 (m,
Cyclic voltammetry was carried out with a Metrohm Autolab
PGSTAT128N potentiostat with a standard three-electrode configu- 3 H, Ph), 8.55 (s, 1 H, H-6), 9.12 (s, 1 H, H-2) ppm. 13C NMR (126 MHz,
ration. Typically, a three-electrode cell equipped with a platinum
working electrode, a Ag/AgCl reference electrode with two mem-
CDCl3): δ = 128.02, 128.79, 129.12, 129.16, 130.29, 130.81, 130.91,
136.29, 141.78, 156.25, 157.35, 158.20 ppm. GC: tR = 22.74 min. MS:
branes (the interior volume contents KCl saturated water solution; m/z (%) = 238 (100) [M+]. C14H10N2S (238.31): calcd. C 70.56, H 4.23,
exterior volume 0.1
M
LiClO4 in CH2Cl2), and a glassy carbon rod
N 11.75; found C 70.36, H 4.30, N 11.71.
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© 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

Full Paper
5-(4-tert-Butylphenyl)-4-(thiophen-2-yl)-pyrimidine (4b): Yield 7.95–7.98 (m, 2 H, H-6 or H-7 and H-2 or H-3), 8.09 (d, J = 5.3 Hz, 1
1
78 %; beige solid; m.p. 126–128 °C. H NMR (500 MHz, CDCl3): δ = H, H-2 or H-3), 8.64 (s, 1 H, H-4), 8.85 (d, J = 8.7 Hz, 1 H, H-6 or H-
1.43 (s, 9 H, tBu), 6.86–6.90 (m, 2 H, thienyl), 7.30 (d, J = 8.1 Hz, 2 7), 9.46 (s, 1 H, H-8), 10.08 (s, 1 H, H-10) ppm. 13C NMR (126 MHz,
3
H, Ph), 7.42 (d, J = 4.6 Hz, 1 H, thienyl), 7.52 (d, J = 8.1 Hz, 2 H, Ph), CDCl3): δ = 96.11, 119.28, 121.89 (q, JC,F = 4.0 Hz, CF3), 122.89,
8.56 (s, 1 H, H-6), 9.12 (s, 1 H, H-2) ppm. 13C NMR (126 MHz, CDCl3): 123.08, 123.36 (q, 3JC,F = 3.7 Hz, CF3), 123.61, 125.06, 128.51, 129.21,
δ = 31.36, 34.78, 126.07, 128.03, 128.76, 130.19, 130.74, 130.97, 130.08, 130.34, 130.60, 132.01, 136.26, 140.62, 149.25, 154.51,
133.23, 141.98, 152.08, 156.34, 157.18, 158.39 ppm. GC: tR
=
157.06 ppm. 19F NMR (470.5 MHz, CDCl3): δ = 99.48 (s, CF3) ppm.
25.44 min. MS: m/z (%) = 294 (100) [M+]. C18H18N2S C: calcd. 73.43,
IR (DRA): ν = 489, 496, 573, 629, 655, 679, 688, 705, 742, 759, 801,
˜
H 6.16, N 9.51; found C 73.59, H 6.36, N 9.63.
831, 841, 911, 929, 994, 1014, 1081, 1117, 1154, 1183, 1268, 1288,
1302, 1328, 1342, 1385, 1401, 1427, 1446, 1456, 1488, 1519, 1554,
4-(Thiophen-2-yl)-5-(4-trifluoromethylphenyl)pyrimidine (4c):
Yield 95 %; pale-yellow solid; m.p. 125–127 °C. 1H NMR (500 MHz,
CDCl3): δ = 6.82 (dd, J = 3.8, 0.8 Hz, 1 H, H-3′), 6.92 (dd, J = 5.0,
3.8 Hz, 1 H, H-4′), 7.46 (dd, J = 5.0, 0.8 Hz, 1 H, H-5′), 7.54 (d, J =
1580, 1628, 1786, 1819, 1911, 3054, 3087, 3110 cm–1. GC: tR
=
25.09 min. MS: m/z (%) = 304 (100) [M+]. C15H7F3N2S (304.29): calcd.
C 59.21, H 2.32, N 9.21; found C 59.11, H 2.49, N 9.10.
8.1 Hz, 2 H, Ph), 7.78 (d, J = 8.1 Hz, 2 H, Ph), 8.55 (s, 1 H, H-6), 9.17
Synthesis of 5-Bromo-4,6-di(thiophen-2-yl)pyrimidine (7): Thi-
enyllithium was prepared by adding nBuLi (1.6 M in hexane,
27.25 mL, 43.6 mmol) to thiophene (4.3 mL, 54.5 mmol) in diethyl
ether (50 mL) at –10 °C. The reaction mixture was stirred at 0 °C for
4 h. This solution was maintained at –30 °C while a solution of 5-
1
(s, 1 H, H-2) ppm. 13C NMR (126 MHz, CDCl3): δ = 123.89 (d, JC,F
=
4
272.5 Hz), 126.18 (q, JC,F = 3.7 Hz), 128.19, 129.60, 129.71, 130.76,
2
130.86, 131.11 (q, JC,F = 32.7 Hz), 140.12, 141.26, 156.21, 157.88,
158.01 ppm. 19F NMR (470.5 MHz, CDCl3): δ = 99.10 (s, CF3) ppm.
GC: tR = 22.14 min. MS: m/z (%) = 306 (100) [M+]. C15H9F3N2S bromo-4-thiophen-2-yl-pyrimidine (2) (1.315 g, 5.45 mmol) was
(306.30): calcd. C 58.82, H 2.96, N 9.15; found C 58.71, H 2.90, N added slowly with stirring during 10 min. The resulting mixture was
9.09.
stirred for 18 h at room temperature, then the reaction was
quenched at 0 °C with stirring with a solution of K3Fe(CN)6 (3.589 g,
10.9 mmol) in water (100 mL). The resulting mixture was stirred for
6 h at room temperature, the precipitate formed was filtered off,
washed with H2O and air dried. The residue was purified by flash
column chromatography (hexane/ethyl acetate, 1:3) to afford 7,
yield (1.233 g, 70 %); yellow powder; m.p. 129–131 °C1. 1H NMR
(500 MHz, CDCl3): δ = 7.20 (dd, J = 5.1, 3.9 Hz, 2 H, H-4′), 7.62 (dd,
J = 5.1, 1.0 Hz, 2 H, H-5′), 8.37 (dd, J = 3.9, 1.0 Hz, 2 H, H-5′), 8.93
(s, 1 H, H-2) ppm. 13C NMR (126 MHz, CDCl3): δ = 112.00, 127.87,
General Procedure for the Syntheses of 7-Substituted
Benzo[f]thieno[3,2-h]quinazolines 5a–c: To a solution of 4a, 4b
or 4c (1 mmol) in MeCN (150 mL) was added iodine (0.037 g,
0.14 mmol). The reaction mixture was irradiated at room tempera-
ture using a UV lamp for an appropriate time (see Table 1, entries
1–3). The solvent was then distilled off in vacuo, and the residue
was dissolved in CHCl3, washed with aqueous Na2S2O3, water, and
brine, dried with anhydrous Na2SO4 and the solvents evaporated.
The residue was purified by flash column chromatography (EtOAc/
hexane, 1:3) to afford the desired benzo[f]thieno[3,2-h]quinazoline
systems.
131.37, 132.52, 141.51, 155.28, 159.15 ppm. IR (DRA): ν = 460, 577,
˜
616, 627, 644, 714, 747, 776, 839, 860, 913, 963, 975, 1024, 1043,
1055, 1066, 1086, 1107, 1161, 1198, 1225, 1266, 1304, 1317, 1348,
1364, 1375, 1423, 1450, 1476, 1520, 1536, 1649, 1746, 1820, 1917,
2172, 2322, 2389, 2475, 2628, 2847, 2926, 3035, 3088, 3103,
3127 cm–1. GC: tR = 26.88 min. MS: m/z (%) = 322 (100) [M+; 79Br],
324 (100) [M+; 81Br]. C12H7BrN2S2 (323.22): calcd. C 44.59, H 2.18, N
8.67; found C 44.40, H 2.35, N 8.44.
Benzo[f]thieno[3,2-h]quinazoline (5a): Yield 43 %; beige solid;
m.p. 199–201 °C. H NMR (500 MHz, CDCl3): δ = 7.66–7.79 (m, 2 H,
Ph), 7.86 (d, J = 5.3 Hz, 1 H, H-2 or H-3), 7.88 (d, J = 5.3 Hz, 1 H, H-
2 or H-3), 8.29–8.35 (m, 1 H, Ph), 8.63–8.38 (m, 1 H, Ph), 9.38 (s, 1
H, H-8), 9.99 (s, 1 H, H-10) ppm. 13C NMR (126 MHz, CDCl3): δ =
120.14, 122.67, 123.14, 124.58, 126.82, 127.33, 128.66, 128.87,
1
General Procedure for the Syntheses of 5-(4-R-phenyl)-4,6-
Di(thiophen-2-yl)pyrimidines 8a–c: A solution of K2CO3 (346 mg,
2.5 mmol) in H2O (3 mL) was added to a mixture of 5-bromo-4,6-
dithiophen-2-yl-pyrimidine (7) (162 mg, 0.5 mmol), phenylboronic
[4-tert-butylphenylboronic acid or 4-(trifluoromethyl)phenylboronic]
acid (0.6 mmol) and Pd(PPh3)4 (29 mg, 5 mol-%) in 1,4-dioxane
(4 mL). The resulting mixture was irradiated in a microwave appara-
tus at 170 °C (250 W) for 20 min. The solvent was then distilled off
in vacuo, and the residue was purified by flash column chromatog-
raphy (hexane/ethyl acetate, 1:3) to afford the desired cross-cou-
pling products 8a, 8b, and 8c.
131.30, 135.01, 141.26, 148.61, 153.98, 156.13 ppm. IR (DRA): ν =
˜
486, 579, 623, 637, 667, 704, 735, 768, 792, 804, 819, 897, 915, 941,
996, 1013, 1044, 1071, 1115, 1147, 1209, 1270, 1336, 1393, 1404,
1423, 1446, 1458, 1486, 1509, 1551, 1566, 1579, 1612, 1661, 1744,
2853, 2924, 3069, 3101 cm–1. GC: tR = 26.09 min. MS: m/z (%) = 236
(100) [M+]. C14H8N2S (236.29): calcd. C 71.16, H 3.41, N 11.86; found
C 71.26, H 3.21, N 11.79.
7-tert-Butylbenzo[f]thieno[3,2-h]quinazoline (5b): Yield 49 %;
pale-yellow solid; m.p. 174–176 °C. 1H NMR (500 MHz, CDCl3): δ =
1.50 (s, 9 H, tBu), 7.80 (d, J = 8.5 Hz, 1 H, H-6 or H-7), 7.87 (d, J =
5.2 Hz, 1 H, H-2 or H-3), 8.05 (d, J = 5.2 Hz, 1 H, H-2 or H-3), 8.32 (s,
1 H, H-4), 8.62 (d, J = 8.5 Hz, 1 H, H-6 or H-7), 9.36 (s, 1 H, H-8), 9.98
(s, 1 H, H-10) ppm. 13C NMR (126 MHz, CDCl3): δ = 31.34, 35.17,
120.15, 120.44, 122.51, 123.11, 124.49, 125.57, 128.81, 131.00,
5-Phenyl-4,6-di(thiophen-2-yl)pyrimidine (8a): Yield 87 %; off-
white solid; m.p. 216–218 °C. 1H NMR (500 MHz, CDCl3): δ = 6.48
(dd, J = 3.9, 0.7 Hz, 2 H, H-3′), 6.82 (dd, J = 5.0, 3.9 Hz, 2 H, H-4′),
7.35 (dd, J = 7.4, 1.9 Hz, 2 H, Ph), 7.37 (dd, J = 5.0, 0.7 Hz, 2 H, H-5′
), 7.57–7.62 (m, 3 H, Ph), 9.07 (s, 1 H, H-2) ppm. 13C NMR (126 MHz,
CDCl3): δ = 125.64, 127.99, 129.40, 129.90, 130.23, 130.40, 131.04,
134.94, 141.55, 148.39, 151.97, 153.82, 155.81 ppm. IR (DRA): ν =
˜
503, 576, 610, 629, 684, 728, 799, 828, 847, 890, 906, 942, 993, 1012,
1073, 1103, 1114, 1160, 1202, 1215, 1259, 1332, 1342, 1344, 1360,
1396, 1422, 1453, 1482, 1510, 1550, 1577, 1618, 1659, 1811, 2865,
2903, 2950, 3045, 3068 cm–1. GC: tR = 28.63 min. MS: m/z (%) = 292
(100) [M+]. C18H16N2S (292.40): calcd. C 73.94, H 5.52, N 9.58; found
C 73.80, H 5.36, N 9.47.
136.42, 142.71, 156.84, 157.69 ppm. IR (DRA): ν = 450, 503, 555, 569,
˜
590, 620, 637, 680, 708, 752, 775, 793, 811, 856, 923, 957, 970, 994,
1004, 1042, 1051, 1073, 1087, 1117, 1162, 1186, 1226, 1236, 1275,
1297, 1343, 1379, 1410, 1430, 1445, 1489, 1536, 1576, 1627, 1751,
1813, 1897, 1969, 2327, 3020, 3077, 3119 cm–1. GC: tR = 28.76 min.
MS: m/z (%) = 320 (100) [M+]. C18H12N2S2 (320.43): calcd. C 67.47, H
7-(Trifluoromethyl)benzo[f]thieno[3,2-h]quinazoline (5c): Yield
1
72 %; beige solid; m.p. 248–250 °C. H NMR (500 MHz, CDCl3): δ = 3.77, N 8.74; found C 67.69, H 3.67, N 8.59.
Eur. J. Org. Chem. 2016, 1420–1428
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Full Paper
5-(4-tert-Butylphenyl)-4,6-di(thiophen-2-yl)pyrimidine
(8b): 2866, 2904, 2958, 3079, 3104 cm–1. GC: tR = 48.91 min. MS: m/z
Yield 89 %; pale-yellow solid; m.p. 150–152 °C. 1H NMR (500 MHz,
CDCl3): δ = 1.46 (s, 9 H, tBu), 6.50 (d, J = 3.4 Hz, 2 H, thienyl), 6.83
(dd, J = 4.7, 4.2 Hz, 2 H, thienyl), 7.26 (d, J = 8.2 Hz, 2 H, Ph), 7.39
(d, J = 5.0 Hz, 2 H, thienyl), 7.62 (d, J = 8.2 Hz, 2 H, Ph), 9.08 (s, 1 H,
H-2) ppm. 13C NMR (126 MHz, CDCl3): δ = 31.49, 34.93, 125.76,
127.11, 127.94, 129.36, 130.33, 131.01, 133.25, 142.85, 153.05,
(%) = 372 (100) [M+]. C22H16N2S2 (372.50): calcd. C 70.94, H 4.33, N
7.52; found C 70.70, H 4.47, N 7.38.
8-(Trifluoromethyl)benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidine
1
(9c): Yield 32 %; yellow solid; m.p. 332–334 °C. H NMR (500 MHz,
CDCl3): δ = 8.08 (d, J = 5.2 Hz, 2 H), 8.29 (d, J = 5.2 Hz, 2 H), 8.92
(s, 2 H, H-7 and H-9), 9.74 (s, 1 H, H-2) ppm. 13C NMR (126 MHz,
156.71, 157.87 ppm. IR (DRA): ν = 505, 520, 558, 596, 634, 713, 740,
˜
3
CDCl3): δ = 111.82, 119.71 (d, JC,F = 3.6 Hz, CF3), 122.23, 123.56,
755, 798, 809, 837, 860, 968, 997, 1027, 1046, 1060, 1085, 1118,
1165, 1199, 1226, 1245, 1279, 1367, 1383, 1403, 1428, 1462, 1470,
1519, 1536, 1649, 1746, 1813, 1921, 2330, 2865, 2901, 2961, 3028,
3067, 3103 cm–1. GC: tR = 34.09 min. MS: m/z (%) = 376 (100) [M+].
128.03, 129.74, 132.34, 136.69, 141.51, 150.94, 156.72 ppm. 19F NMR
(470.5 MHz, CDCl3): δ = 100.74 (s, CF3) ppm. IR (DRA): ν = 482, 521,
˜
563, 640, 678, 701, 734, 749, 771, 810, 835, 882, 924, 975, 997, 1005,
1087, 1104, 1126, 1164, 1209, 1266, 1314, 1338, 1382, 1442, 1474,
1496, 1545, 1567, 1579, 1669, 1766, 2925, 3065, 3085 cm–1. GC: tR =
34.66 min. MS: m/z (%) = 384 (100) [M+]. C19H7F3N2S2 (384.39): calcd.
C 59.37, H 1.84, N 7.29; found C 59.58, H 1.68, N 7.38.
C22H20N2S2 (376.53): calcd. C 70.18, H 5.35, N 7.44; found C 70.18,
H 5.39, N 7.45.
4,6-Di(thiophen-2-yl)-5-(4-trifluoromethylphenyl)pyrimidine
(8c): Yield 98 %; off-white solid; m.p. 200–201 °C. 1H NMR (500 MHz,
CDCl3): δ = 6.48 (dd, J = 3.9, 0.9 Hz, 1 H, H-3′), 6.86 (dd, J = 5.1,
3.9 Hz, 1 H, H-4′), 7.41 (dd, J = 5.1, 0.9 Hz, 1 H, H-5′), 7.52 (d, J =
8.0 Hz, 2 H, Ph), 7.86 (d, J = 8.0 Hz, 2 H, Ph), 9.10 (s, 1 H, H-2) ppm.
13C NMR (126 MHz, CDCl3): δ = 122.82, 124.32, 124.99, 127.11 (q,
3JC,F = 3.6 Hz, CF3), 128.08, 130.79, 130.92, 131.63, 131.89, 140.41,
142.21, 157.27, 157.56 ppm. 19F NMR (470.5 MHz, CDCl3): δ = 99.30
Supporting Information (see footnote on the first page of this
article): UV/Vis, 1H, 19F and 13C NMR spectra for new compounds,
and detailed information (Table S1) concerning crystal structures of
compounds 4c, 5a, and 7 on the basis of the X-ray analysis.
Acknowledgments
(s, CF3) ppm. IR (DRA): ν = 479, 504, 556, 590, 609, 619, 637, 684,
˜
This work was supported by Government of the Russian Federa-
tion (contract number 02.A03.21.0006, Act 211) , the Ural
Branch of the Russian Academy of Sciences (project numbers
15-21-3-6 and 15-21-3-9), the Russian Foundation for Basic Re-
search (research project numbers 14-03-01017-A, 14-03-00479-
A, and 14-03-31040-mol_a). N. I. Makarova, I. V. D., A. V. M., and
V. I. M. would like to acknowledge financial support for the
absorption, fluorescence and quantum chemical studies from
the Ministry of Education and Science of Russian Federation
within the framework of the State Assignment for Research
(project number 1895).
714, 737, 761, 811, 839, 852, 865, 922, 954, 967, 999, 1023, 1047,
1068, 1078, 1105, 1122, 1137, 1159, 1185, 1238, 1299, 1327, 1361,
1384, 1403, 1434, 1498, 1539, 1614, 1686, 1822, 1928, 2322, 3083,
3123 cm–1. GC: tR = 27.53 min. MS: m/z (%) =388 (100) [M+].
C19H11F3N2S (356.36): calcd. C 58.75, H 2.85, N 7.21; found C 58.80,
H 2.79, N 7.24.
General Procedure for the Syntheses of 8-Substituted Benzo-
[g,h]dithieno[2,3-e:3′,2′-j]perimidines 9a–c: To a solution of 5-(4-
R-phenyl)-4,6-dithiophen-2-yl-pyrimidine (8a, 8b or 8c) (1 mmol) in
MeCN (150 mL) was added iodine (0.074 g, 0.28 mmol). The reaction
mixture was irradiated at room temperature using a UV lamp for
the appropriate time (see Table 1, entries 4–6). The solvent was
then distilled off in vacuo, and the residue was dissolved in CHCl3,
washed with aqueous Na2S2O3, water, and brine, dried with anhy-
drous Na2SO4 and the solvents evaporated. The residue was purified
by flash column chromatography (EtOAc/hexane, 1:3) to afford the
desired benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidine systems.
Keywords: Nitrogen heterocycles · Sulfur heterocycles ·
Polycycles · Cyclization · Nucleophilic substitution · UV/Vis
spectroscopy
Benzo[g,h]dithieno[2,3-e:3′,2′-j]perimidine (9a): Yield 18 %;
beige solid; m.p. >350 °C. 1H NMR (500 MHz, CDCl3): δ = 8.02 (d,
J = 5.2 Hz, 2 H), 8.22 (t, J = 7.8 Hz, 1 H, H-8), 8.27 (d, J = 5.2 Hz, 2
H), 8.75 (d, J = 7.8 Hz, 2 H, H-7 and H-9), 9.72 (s, 1 H, H-2) ppm. 13C
NMR (126 MHz, CDCl3): δ = 112.48, 123.59, 123.62, 127.70, 127.89,
128.46, 128.56, 131.65, 131.91, 132.10, 132.17, 135.60, 142.10,
[1] For selected reviews, see: a) M. D. Watson, A. Fechtenkötter, K. Müllen,
Chem. Rev. 2001, 101, 1267–1300; b) J. E. Anthony, Chem. Rev. 2006, 106,
5028–5048; c) J. Wu, W. Pisula, K. Müllen, Chem. Rev. 2007, 107, 718–747;
d) J. Wu, Curr. Org. Chem. 2007, 11, 1220–1240; e) X. Feng, W. Pisula, K.
Müllen, Pure Appl. Chem. 2009, 81, 2203–2224; f) C. Li, M. Liu, N. G.
Pschirer, M. Baumgarten, K. Müllen, Chem. Rev. 2010, 110, 6817–6855; g)
T. M. Figueira-Duarte, K. Müllen, Chem. Rev. 2011, 111, 7260–7314; h) K.
Takimiya, S. Shinamura, I. Osaka, E. Miyazaki, Adv. Mater. 2011, 23, 4347–
4370; i) T. Jin, J. Zhao, N. Asao, Y. Yamamoto, Chem. Eur. J. 2014, 20,
3554–3576, and references cited therein.
150.43, 155.86 ppm. IR (DRA): ν = 467, 574, 626, 656, 738, 748, 768,
˜
798, 828, 839, 859, 885, 962, 1006, 1091, 1119, 1173, 1233, 1274,
1325, 1338, 1356, 1428, 1456, 1491, 1559, 1580, 1636, 1666, 1728,
1763, 1805, 1878, 1940, 2344, 2852, 2923, 2963, 3017, 3063, 3084,
3093 cm–1. GC: tR = 39.91 min. MS: m/z (%) = 316 (100) [M+].
C18H8N2S2 (316.39): calcd. C 68.33, H 2.55, N 8.85; found C 68.56, H
2.71, N 8.99.
[2] a) I. V. Borovlev, O. P. Demidov, Chem. Heterocycl. Compd. 2003, 39, 1417–
1442; b) T. Shaefer, T. Eichenberger, K. Badon, A. Ricci, N. Chebotareva,
W. O. Patent 2010006890, 2010; c) T. Shaefer, K. Badon, W. O. Patent
2010031738, 2010.
[3] a) J.-I. Park, B. L. Lee, J. W. Chung, U. S. Patent 20120168726, 2012; b) J.-
I. Park, B. L. Lee, J. W. Chung, U. S. Patent 20120168729, 2012.
8-tert-Butylbenzo[g,h]dithieno[2,3-e:3′,2′-j]perimidine (9b):
Yield 51 %; pale-yellow solid; m.p. 298–300 °C. 1H NMR (500 MHz,
CDCl3): δ = 1.67 (s, 9 H, tBu), 7.96 (d, J = 4.7 Hz, 2 H), 8.22 (d, J =
4.7 Hz, 2 H), 8.70 (s, 2 H, H-7 and H-9), 9.60 (s, 1 H, H-2) ppm. 13C
NMR (126 MHz, CDCl3): δ = 31.92, 35.71, 112.14, 118.37, 120.73,
123.42, 127.48, 131.27, 135.25, 142.06, 149.91, 151.02, 155.38 ppm.
[4] For selected reviews on nucleophilic aromatic substitution of hydrogen:
a) O. N. Chupakhin, V. N. Charushin, H. C. van der Plas, Nucleophilic Aro-
matic Substitution of Hydrogen, Academic Press, New York, San Diego,
1994, p. 367; b) V. N. Charushin, O. N. Chupakhin, Pure Appl. Chem. 2004,
76, 1621–1632; c) V. N. Charushin, O. N. Chupakhin, Mendeleev Commun.
2007, 17, 249–254; d) M. Makosza, K. Wojciechowski, Chem. Rev. 2004,
104, 2631–2666; e) M. Makosza, Chem. Soc. Rev. 2010, 39, 2855–2868; f)
V. N. Charushin, O. N. Chupakhin, in: Topics in Heterocyclic Chemistry, vol.
IR (DRA): ν = 461, 488, 563, 672, 726, 750, 761, 814, 832, 850, 871,
˜
973, 986, 997, 1005, 1030, 1091, 1137, 1210, 1250, 1318, 1332, 1350,
1383, 1394, 1435, 1472, 1496, 1542, 1563, 1581, 1612, 1740, 1963,
Eur. J. Org. Chem. 2016, 1420–1428
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Full Paper
5 (Eds.: V. N. Charushin, O. N. Chupakhin), Springer International Publish-
ing, Switzerland, 2013, p. 1–50; g) M. Makosza, K. Wojciechowski, in:
Topics in Heterocyclic Chemistry, vol. 5 (Eds.: V. N. Charushin, O. N. Chu-
pakhin), Springer International Publishing, Switzerland, 2013, p. 51–105.
[5] a) E. V. Verbitskiy, E. M. Cheprakova, P. A. Slepukhin, M. I. Kodess, M. A.
Ezhikova, M. G. Pervova, G. L. Rusinov, O. N. Chupakhin, V. N. Charushin,
Tetrahedron 2012, 68, 5445–5452; b) E. V. Verbitskiy, G. L. Rusinov, V. N.
Charushin, O. N. Chupakhin, E. M. Cheprakova, P. A. Slepukhin, M. G.
Pervova, M. A. Ezhikova, M. I. Kodess, Eur. J. Org. Chem. 2012, 6612–6621.
[6] F. B. Mallory, C. W. Mallory, Photocyclization of Stilbenes and Related Mol-
ecules, in: Organic Reactions, John Wiley & Sons, Hoboken, New York,
1984, vol. 30, p. 151.
[7] L. Strekowski, R. Watson, J. Org. Chem. 1986, 51, 3226–3228.
[8] Mercury 3.3, available from http://www.ccdc.cam.ac.uk/mercury/.
[9] S. R. Meech, D. Phillips, J. Photochem. 1983, 23, 193–217.
[10] R. S. Sanchez-Carrera, M. C. R. Delgado, C. C. Ferron, R. M. Osuna, V.
Hernandez, J. T. L. Navarrete, A. Aspuro-Gazik, Org. Electron. 2010, 11,
1701–1712.
[14] C. M. Cardona, W. Li, A. E. Kaifer, D. Stockdale, G. C. Bazan, Adv. Mater.
2011, 23, 2367–2371.
[15] a) A. D. Becke, Phys. Rev. A 1988, 38, 3098–100; b) C. Lee, W. Yang, R. G.
Parr, Phys. Rev. B 1988, 37, 785–789.
[16] M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R.
Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nak-
atsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng,
J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa,
M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Mont-
gomery Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers,
K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K. Raghavachari,
A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M.
Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo,
R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli,
J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth,
P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B.
Foresman, J. V. Ortiz, J. Cioslowski, D. J. Fox, Gaussian 09, revision D.01,
Gaussian, Inc., Wallingford CT, 2009.
[17] J. Tomasi, B. Mennucci, R. Cammi, Chem. Rev. 2005, 105, 2999–3093.
[11] H. T. Black, S. Liu, V. S. Ashby, Org. Lett. 2011, 13, 6492–6495.
[12] O. V. Dolomanov, L. J. Bourhis, R. J. Gildea, J. A. K. Howard, H. Puschmann,
J. Appl. Crystallogr. 2009, 42, 339–341.
Received: November 17, 2015
[13] G. M. Sheldrick, Acta Crystallogr., Sect. A 2008, 64, 112–122.
Published Online: February 8, 2016
Eur. J. Org. Chem. 2016, 1420–1428
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