Structures of branched oligophenylenes studied by NMR spectroscopy

Article abstract of DOI:10.1007/s11172-013-0323-7

A series of model cyclotrimers was studied by NMR spectroscopy using 2D COSY, HSQC, and HMBC correlations to establish the structures of branched oligophenylenes, whose branch-ing center is the 1,3,5-triphenyl-substituted benzene ring.

Full text of DOI:10.1007/s11172-013-0323-7

Russian Chemical Bulletin, International Edition, Vol. 62, No. 10, pp. 2234—2244, October, 2013
2234
Structures of branched oligophenylenes studied by NMR spectroscopy
I. A. Khotina, A. I. Kovalev, N. S. Kushakova, M. A. Babushkina, Yu. V. Vasil´ev, and A. S. Peregudov
A. N. Nesmeyanov Institute of Organoelement Compounds, Russian Academy of Sciences,
28 ul. Vavilova, 119991 Moscow, Russian Federation.
Fax: +7 (495) 135 5085. Eꢀmail: khotina@ineos.ac.ru
A series of model cyclotrimers was studied by NMR spectroscopy using 2D COSY, HSQC,
and HMBC correlations to establish the structures of branched oligophenylenes, whose branchꢀ
ing center is the 1,3,5ꢀtriphenylꢀsubstituted benzene ring.
Key words: branched oligophenylenes, cyclotrimers, Suzuki reaction, NMR spectroscopy,
2D correlations.
One of the most intensely developed areas of practical
state, can serve as an alternative for the development of
such photodiodes.16 However, problems on structure deꢀ
termination of chromophoric fragments and identificaꢀ
tion of the general structure of complicated aromatic sysꢀ
tems restrain the development of this promising trend.
This work is devoted to the NMR studies of the strucꢀ
tures of branched oligophenylenes, whose branching cenꢀ
ter is the 1,3,5ꢀtriphenylꢀsubstituted benzene ring.
The synthesis of branched oligophenylenes based on
1,3,5ꢀtris(pꢀbromophenyl)benzene (1) obtained by the
crossꢀcoupling in the presence of the nickel complexes
(Scheme 1) has earlier been described.17—19
use of conjugated polymers is the preparation of organic
lightꢀemitting diodes (OLED).1—3 At present, considerꢀ
able progress was achieved in using red4—6 and green7 disꢀ
plays based on both lowꢀmolecularꢀweight organic comꢀ
pounds and polymers. Rapt attention has recently been
given to the synthesis of polymers luminescing in the blue
region of the visible spectrum.8—15 However, obtaining of
efficient blue luminescence still remains to be a narrow
unit in the production of a polymerꢀbased fullꢀcolor diode.
Branched oligophenylenes having bright fluorescence in
the blue region, being both in solution and in the solid
Scheme 1
i. Ni0, Zn, DMF, 70 С, 6 h.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2234—2244, October, 2013.
1066ꢀ5285/13/6210ꢀ2234 © 2013 Springer Science+Business Media, Inc.

Branched oligophenylene structures
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 10, October, 2013
2235
The formed macromolecules contain biphenyl bridges
connecting the nodal trisubstituted benzene rings, termiꢀ
nal biphenyl groups, and unreacted bromophenyl groups.
In addition, the trisubstituted benzene rings can have difꢀ
ferent environments.
The use of H NMR spectroscopy in studying oligoꢀ
phenylenes is restrained because of overlapping of multiꢀ
plet signals.
In the 13С NMR spectrum of compound 2 (see Table 1),
the signal at 125.08 ppm (C(1)) corresponds to the tertiary
carbon atoms of the central benzene ring. The signals at
142.26 (C(2)) and 141.07 ppm (C(3)) can be assigned to
the quaternary carbon atoms of the central and peripheral
benzene rings, respectively. The C atoms of the external
benzene ring exhibit signals at 127.26 (C(4)), 129.75
(C(5)), and 127.44 ppm (C(6)).
1
The 1H and 13С NMR spectra of monomer 1 and model
compounds 2—6 were examined to assign the signals
of protons in the aromatic region of branched oligoꢀ
phenylenes.
The following compounds were chosen as models of
the main fragments of oligophenylenes: 1,3,5ꢀtris(pꢀ
bromophenyl)benzene (1),20 1,3,5ꢀtriphenylbenzene (2),21
1,3,5ꢀtris(pꢀdiphenylꢀ4´ꢀyl)benzene (3),22 1,3,5ꢀtris(1,3,5ꢀ
тtriphenylbenzenꢀ4´ꢀyl)benzene (4),23 and 1,3,5ꢀtrisꢀ
(4ꢀbromoꢀ1,1´ꢀdiphenylꢀ4´ꢀyl)benzene (5)24 (Scheme 2).
In the 1Н NMR spectrum of compound 1 (see Table 1),
the signals from protons of the central benzene ring can
unambiguously be assigned as a singlet at 7.70 ppm (H(1))
and the signals from the 1,4ꢀsubstituted benzene ring can
be assigned as a doublet at 7.62 ppm (H(5)) and a doublet
at 7.54 ppm (H(4)). In the spectrum of compound 1, the
signals from the Н(5) protons are downfield shifted (see
Table 1) compared to similar signals in the spectrum of
compound 2 and the signals of the H(1) and H(4) protons
are upfield shifted.
The 13С NMR spectrum of compound 1 (see Table 1)
exhibits signals at 125.19 ppm that can be assigned to the
tertiary carbon atom of the central 1,3,5ꢀtrisubstituted
benzene ring.
The signal assignment in the 13С NMR spectrum on
the basis of HSQC and HMBC experiments is unambiꢀ
guous (Fig. 1).
Scheme 2
The signal at 125.19 ppm (in HSQC) gives the correlaꢀ
tion peak with a singlet at 7.70 ppm and corresponds to
С(1). The signal at 122.32 ppm (in HSQC) unambiguousꢀ
ly belongs to the C(6) atoms directly bound to the broꢀ
mine atoms (calculated data:  122.32). However, signal
assignment in the HSQC spectrum for the С(4) and С(5)
carbon atoms is ambiguous. The calculations by the ACD/
CNMR DB additive scheme (solvent CDCl3) showed that
the 13С signals from the С(4) atoms ( 129.10) are in
a stronger field than the signals of the С(5) atom ( 132.26).
Since the difference in the calculated and experimental
data for these atoms is low (1 and 2 ppm, respectively),
HMBC data were required for the more exact assignment
of these signals (see Fig. 2). The signal at 139.82 ppm (see
Fig. 2) gives correlation peaks with a signal at 7.70 ppm,
which is a downfield part of the АA´ВB´ system and, thus,
this signal is assigned to С(3). Therefore, the signals at
7.62 and 7.54 ppm correspond to Н(5) and H(4), respectivꢀ
ely. According to these assignments, the signal at 129.10 ppm
is assigned to the C(4) atom, whereas the signal at 139.82 ppm
is attributed to the C(3) atom. The signal at 141.73 ppm
gives the correlation peak with the upfield АA´ВB´ system
of H(4) and is attributed to the С(2) atom.
i. HC(OEt)3, HCl, C6H6, 20 С, 4 h.
Compound 5 was used for the synthesis of model comꢀ
pound 6: 1,3,5ꢀ[tris(pꢀterphenylꢀ4ꢀyl)]benzene21 with terꢀ
phenyl branches. The latter was synthesized using a stanꢀ
dard procedure by the Suzuki reaction of compound 5
with phenylboronic acid.25,26
The corresponding signals in the NMR spectra for
compounds 1, 2, and 4 (and oligophenyl Pꢀ1) are presentꢀ
ed in Table 1. The assignment of chemical shifts for comꢀ
pounds 1 and 2 (see Table 1) is consistent with the pubꢀ
lished one.27
In the 1Н NMR spectrum of compound 2 (see Table 1),
the protons of the central benzene ring can be assigned as
a singlet at 7.81 ppm (H(1)), a doublet at 7.72 ppm (H(4)),
a triplet at 7.50 ppm (H(5)), and a triplet at 7.40 ppm
(H(6)).
Thus, the C atoms of the pꢀsubstituted benzene rings
of molecule 1 are characterized by signals at 129.10 (С(4)),
132.26 (С(5)), and 122.32 ppm (С(6)), and the latter signal
is assigned to the C atoms directly bound to the bromine
atoms, whereas the signals at 141.73 and 139.82 ppm
correspond to two quaternary carbon atoms of the benzꢀ
ene rings.

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Khotina et al.
Table 1. Signal assignment in the 1Н and 13С NMR spectra of compounds 1—3 and Pꢀ1
Comꢀ
pound

1Н
13С
1
2
3
7.70 (Н(1)); 7.54 (d, Н(4));
7.62 (d, Н(5))
125.19 (С(1)); 141.73 (С(2)); 139.82 (С(3));
129.10 (С(4)); 132.26 (С(5)); 122.32 (С(6))
125.08 (С(1)); 142.26 (С(2)); 141.07 (С(3));
127.26 (С(4)); 129.75 (С(5)); 127.44 (С(6))
125.0—125.4 (С(1), С(8), С(10));
7.81 (Н(1)); 7.72 (d, Н(4));
7.50 (t, Н(5)); 7.41 (t, Н(6))
7.88 (Н(8)); 7.84 (Н(10));
7.75 (Н(11)); 7.52 (Н(12));
7.43 (Н(13))
140.66 (С(2)); 142.50 (С(9)); 140.52 (С(3));
141.15 (С(14))
Pꢀ1
7.89 (Н(1), Н(16)), Н(17));
7.78 (Н(20)); 7.56—7.62 (Н(4));
7.63—7.66 (Н(5))
125.0 (С(1)); 141.4 (С(2)); 140.0 (С(3));
128.9 (С(4)); 132.0 (С(5)); 122.0 (С(6))
The representative of the second generation of pheꢀ
nylene dendrimers, viz., tridecaphenyl (4) (cyclotrimer
with 13 benzene rings), was synthesized by the acetylation
of 1,3,5ꢀtriphenylbenzene (2) via the Friedel—Crafts reꢀ
action to form [1ꢀ(4ꢀacetylphenyl)ꢀ3,5ꢀdiphenyl]benzene
followed by cyclocondensation. In this model compound,
the protons of two different types of 1,3,5ꢀtrisubstituted
benzene rings have different environments and, hence, sevꢀ
eral signals from these protons should appear in the specꢀ
trum. Differences in the 13С NMR spectrum should also
be expected.
In the 1H NMR spectrum of compound 4 (see Fig. 2, а),
the signals from the protons and carbon atoms of the
aromatic АA´ВB´X system can easily be assigned. The
protons of the external benzene rings are characterized by
a doublet at 7.75 ppm (Н(11)) and triplets at 7.52 (Н(12))
and 7.43 ppm (Н(13)).
The HSQC and HMBC correlations (see Fig. 3) make
it possible to assign all signals in the 1Н (see Fig. 2, а) and
13С (see Fig. 2, b) NMR spectra of compound 4.
Based on the HMBC spectrum (see Fig. 3, b), the
signal at 142.71 ppm can be assigned to C(9) due to the
single correlation with H(11). The signal at 141.35 ppm
corresponds to the C(14) atom because of its correlation
The NMR spectra of compound 4 are shown in
Figs 2 and 3.

Branched oligophenylene structures
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 10, October, 2013
a
2237
1
5
4

6
1
125
130
135
140
4
5
7.70
1
7.65
7.60
7.55

b
4
5

138
139
140
141
142
3
2
7.75
7.70
7.65
7.60
7.55
7.50

Fig. 1. Part of the HSQC spectrum (a) and the part of the HMBC spectrum (b) for compound 1.
with H(12) and with two other aromatic protons at 7.88 and
7.84 ppm attributed to H(8) and H(10), respectively. Thus,
among unassigned signals from the Н(1), Н(4), and Н(5)
protons, the singlet signal at 7.96 ppm can be for H(1) only.
Two other signals of nonꢀquaternary carbon atoms
merge into one signal at 128.09 ppm (see Fig. 3, а), and
the signals from the corresponding protons are in the range
 7.80—7.90, i.e., they belong to C(4) and С(5). As for the

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Khotina et al.
a
4, 5, 8
12
11
1
10
13
8.0
7.9
7.8
7.5
7.4

12
b
11
4, 5
13
8
14
9
7
2
6
10
3
1
142
140
130
128
126

Fig. 2. 1Н (а) and 13C (b) NMR spectra for compound 4.
signals for the quaternary carbon atoms at 140.52 and
140.66 ppm, they can be assigned to C(3) and C(2), reꢀ
spectively, on the basis of their HMBC correlations (see
Fig. 3, b).
The signal from C(3) correlates with the signal from
H(1) at 7.96 ppm and with the H(5) signal at 7.88 ppm.
The signal of the quaternary carbon atom at 42.25 ppm
(С(7)) correlates with the Н(4) and Н(8) signals ( ~7.89),
and the signal at 142.00 ppm (С(6)) correlates with the
Н(5) signal (see Fig. 2, b).
The signal at 140.52 ppm (С(2)) shows the correlation
with the signal from the Н(4) proton only. Finally, these
correlations make it possible to assign the signal at
7.84 ppm to H(10).
The 1H NMR spectra of compounds 3 and 6 were also
analyzed. The signal assignment is shown in Fig. 4. In the
1Н NMR spectrum of compound 6, compared to the specꢀ
trum of compound 3 (see Fig. 4), two AB quadruplets at
7.75, 7.79 and 7.83, 7.87 ppm assigned to the Н(25),
Н(24), Н(23), and Н(22) protons are observed instead of
one AB quadruplet at 7.77 and 7.84 ppm corresponding to
the Н(7) and Н(8) protons. In addition, the singlet signal
of protons of the phentriyl fragment exhibits the downꢀ
field shift.
Branched model oligophenylene was synthesized by
the polycondensation of 1,3,5ꢀtris(4ꢀbromophenyl)benzꢀ
ene (1) together with bromobenzene at the molar ratio
1 : 2.5 in a DMF solution in the presence of the zeroꢀ
valent Ni complex. It was expected that the synthesis at
this ratio of components would give lowꢀmolecularꢀweight
oligophenylene, in the NMR spectra of which the signals
of protons and carbon atoms would be resolved.

Branched oligophenylene structures
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 10, October, 2013
2239
4, 5, 8
a
12
1
11
13
10

8
125
126
127
128
129
1
10
11
13
4, 5
12
7.9
7.8
7.7
7.6
7.5

b

140
141
142
143
7.9
7.8
7.7
7.6
7.5

Fig. 3. Part of the HSQC spectrum (a) and the part of the HMBC spectrum (b) for compound 4.
1
1
The Н and 13C NMR spectra of branched oligopheꢀ
In the complicated Н NMR spectrum of oligopheꢀ
nylene Pꢀ1 (see Fig. 5), the characteristic triplet signals of
the mꢀ, oꢀ, and pꢀprotons Н(11) ( 7.67), Н(12) ( 7.48),
and Н(13) ( 7.38) of the terminal phenyl groups can be
assigned with high reliability. The ratio of integral intensiꢀ
nylene are presented in Figs 5 and 6, respectively. The
signals from protons in the NMR spectra of oligophenylene
Pꢀ1 were assigned due to a comparison with the spectra of
monomer 1 and model compounds 2—6.

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Khotina et al.
a
1
8
7
11
7.70
11
12
7.50
12
13
7.90
7.80
7.60
7.40

b
1
24
25
22
23
13
7.90
7.80
7.70
7.60
7.50
7.40

Fig. 4. 1Н NMR spectra for model compounds 3 (а) and 6 (b).
7, 8
1
12
20
22—25
11
13
4, 5
16, 17
7.90
7.85
7.80
7.75
7.70
7.65
7.60
7.55
7.50
7.45
7.40

Fig. 5. 1Н NMR spectrum of oligophenylene Pꢀ1.
12
11
7, 8
2, 3, 9, 14, 10, 15
5
13
1
6
142 141 140
Fig. 6. 13C NMR spectrum of oligophenylene Pꢀ1.
130
125

ties is 2 : 2 : 1. These signals almost coincide with signals
of the same groups of model compounds 3, 4, and 6. The
COSY spectrum of Pꢀ1 (Fig. 7) confirms that the assignꢀ
ment of signals from the H(11)—Н(13) protons is valid.
The 1Н NMR spectrum (see Fig. 5) exhibits three sinꢀ
glets at 7.89 ppm, which characterize the protons of the
1,3,5ꢀsubstituted benzene ring, namely, Н(1), Н(16), and
Н(17), differed by the environment of the ring. The COSY

Branched oligophenylene structures
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2241

7.4
7.5
7.6
7.7
7.8
7.9
7.9
7.8
7.7
7.6
7.5
7.4

Fig. 7. COSY spectrum of oligophenylene Pꢀ1.
spectrum (see Fig. 7) clearly shows that the protons of the
trisubstituted benzene ring also characterize the singlet at
7.78 ppm (crossꢀpeak). A comparison shows that the sigꢀ
nal from the Н(1) proton in the spectrum of compound 2
is detected at 7.8 ppm, whereas the signal of the same
Н(1) proton in the spectrum of compound 1 (tribromoꢀ
substituted monomer) is observed at 7.7 ppm. It can be
assumed that in the spectrum of the polymer the signal
from the phentriyl proton Н(20) is localized in the closest
vicinity to the bromine atoms and appears at 7.78 ppm,
unlike the signals at 7.89 ppm that belong to other phenꢀ
triyl protons.
The COSY spectrum exhibits spin systems of the same
type for oligophenylene Pꢀ1 and for the monomer 1 with
the terminal bromine atoms. For example, the components
of the АA´ВB´ system at 7.65/7.64 and 7.62/7.61 ppm are
clearly seen. The both components have spinꢀspin couꢀ
pling constants J = 8.5 Hz. The second system is at
7.65/7.63 and 7.59/7.58 ppm with J = 8.4 Hz. The chemꢀ
ical shifts and spinꢀspin coupling constants are consistent
with similar values for compound 1. Thus, the part of the
spectrum in the region  7.55—7.65 is assigned to signals
from the H(4) and H(5) protons localized in the nearest
vicinity of the terminal bromine groups.
sponding protons. Another, more intense 13С signal is obꢀ
served at 127.89 ppm and correlates with multiplet signals
at 7.81 and 7.74 ppm. A comparison with the spectra of
compounds 1 and 3 indicates that the signals at 7.81 ppm
belongs to the protons of the phenylene groups, namely,
Н(5) and Н(4), as in compound 3. Thus, the signals from
the C(7) and С(8) atoms can be considered assigned. Based
on the similarity of the chemical environment of these
protons in positions 22—25, we can conclude that the
corresponding signals from carbon C(22)—C(25) can overꢀ
lap with the С(7) and С(8) signals in the 13С NMR specꢀ
trum. The signals centered at 7.66 ppm are assigned to the
protons of the bromosubstituted phenylene groups (proꢀ
tons Н(4) and Н(5) in compound 1 and oligophenylene
Рꢀ1) and correlate with the С(5) signal at 132.02 ppm in the
13С NMR spectrum. Thus, some signals at 7.55—7.65 ppm
are assigned to the H(4) and H(5) protons situated in the
nearest vicinity to the terminal bromine atoms (see Table 1).
The HSQC spectrum includes other correlations as
well: the signals centered at 125.22 ppm correlate with
those at 7.92/7.81 ppm assigned, most probably, to the
protons Н(1), Н(16), and Н(17) of the trisubstituted benꢀ
zene rings.
The HMBC spectrum (Fig. 9) of oligophenylene Pꢀ1
resembles similar spectra of the model compounds. The
signal at 140.60 ppm correlates with the signals of triplets
of the phenyl groups and can be assigned to С(14). The
same multiplet signal from the carbon atom also correꢀ
lates with the signals of protons at 7.69 (H(11)), 7.75
(Н(22), Н(23)) and 7.82 ppm (H(7), Н(8)). The signals
The COSY experiment also shows that the part of the
1Н NMR spectrum at 7.75 and 7.85 ppm characterizes the
protons of the pꢀsubstituted benzene rings.
The HSQC spectrum (Fig. 8) clearly shows correlaꢀ
tions of signals from the C(13), C(12), and C(11) carbon
atoms at 127.67, 129.08, and 127.30 ppm with the correꢀ

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Khotina et al.
1
22—25
11
7, 8
4, 5
12
13

124
126
128
130
132
134
1
11
7, 8
13
5
7.9
7.8
7.7
7.6
7.5
7.4

Fig. 8. HSQC spectrum of oligophenylene Pꢀ1.
7, 8
22—25
1
12
20
11
4, 5
16, 17

139
3, 15, 19
140
141
142
9, 14, 20, 21
10, 18
7.9
Fig. 9. HMBC spectrum of oligophenylene Pꢀ1.
7.8
7.7
7.6
7.5

from the C(20) and C(21) atoms are partially overlapped
with the signals of C(14) and С(9). The signals from the
C(10) and С(15) atoms at 142.26 ppm are similar to the
signals from C(6) and С(7) of compound 5 and correlate
with the signals of the Н(7) and Н(8) protons. The signals
from the C(19) and С(18) atoms are, most likely, at 139.90

Branched oligophenylene structures
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 10, October, 2013
2243
current for 2 h. The formed precipitate was filtered off, washed
with acetone and alcohol, and recrystallized from chloroform.
1,3,5ꢀTris(pꢀbromophenꢀ4´ꢀyl)benzene (1).21 A roundꢀbotꢀ
tom flask (200 mL) was charged with 4ꢀbromoacetophenone
(12.18 g, 60 mmol), benzene (60 mL), and ethyl orthoformate
ester (13.47 mL, 79.5 mmol) at ~20 С. Gaseous HCl was passed
through the reaction mixture for 2 h with vigorous stirring. The
solution gained a brownꢀred color within the first hour, and
a precipitate began to form. After the end of the reaction, the
precipitate was filtered off, washed with acetone and alcohol,
and dried for 12 h in vacuo (0.133 Pa) at ~20 С and purified
using column chromatography on silica gel (chloroform as an
eluent). The yield was 5.11 g (47%), pale yellow crystals,
m.p. 267—270 С. Found (%): С, 53.48; Н, 3.08; Br, 43.48.
С24Н15Br3. Calculated (%): С, 53.03; Н, 2.76; Br, 44.19.
1Н NMR (600 MHz, CDCl3), : 7.72 (s, 1 Н); 7.63 (d, 2 Н,
J = 8.5 Hz); 7.56 (d, 2 Н, J = 8.5 Hz). MS (EI), m/z: 542.2 [M]+.
Compounds 2—5 were obtained similarly.
and 140.10 ppm and correlate with the signals from the
protons Н(16), Н(17), and Н(22) (С(19)) and Н(23)
(С(18)).
Based on the signal assignment of protons of model
compound 6, we can say more exactly that the signals in
the 1Н NMR spectrum at 7.75—7.82 ppm characterize
the Н(22)—Н(25) protons.
The ratio of the major fragment of Pꢀ1 was calculated
by the integration of the 1Н NMR spectrum. The integral
intensity of protons of the bromosubstituted rings towards
the sum of integral intensities of signals from all protons is
~1.2 : 10, i.e., oligophenylene Pꢀ1 contains a significant
part of phenyl groups.
Since the biphenyl bridging group includes eight proꢀ
tons of the Н(22)—Н(25) type and each terminal biphenyl
group contains four protons of the Н(7) and Н(8) type,
the ratio of these groups can be calculated from the inteꢀ
gral intensities as ~1 : 2.
1,3,5ꢀTriphenylbenzene (2).20 The yield was 62%, m.p. 175 С.
Found (%): С, 94.21; Н, 5.76. С24Н18. Calculated (%): С, 94.12;
Н, 5.88.
Thus, we succeeded to determine signals from the
bridging groups appeared due to the polymer formation
reaction and to distinguish signals from the biphenyl groups
in the NMR spectrum of oligophenylene Pꢀ1. These reꢀ
sults provide the possibility of further studying the strucꢀ
tures of branched oligoꢀ and polyphenylenes containing
various substituents.
1,3,5ꢀTris(pꢀdiphenylꢀ4´ꢀyl)benzene (3) was purified using
column chromatography (silica gel, chloroform, Rf = 0.8). The
yield was 52%, white powder, m.p. 240—242 С. Found (%):
С, 94.43; Н, 5.57. С42Н30. Calculated (%): С, 94.38; Н, 5.62.
1Н NMR (600 MHz, CDCl3), : 7.92 (s, 3 Н); 7.84 (d, 6 Н,
J = 8.3 Hz); 7.76 (d, 6 Н, J = 8.3 Hz); 7.70 (d, 6 Н, J = 7.2 Hz);
7.51 (t, 6 Н, J = 7.7 Hz); 7.40 (t, 3 Н, J = 7.4 Hz). MS (EI), m/z:
534.7 [M]+.
Experimental
1,3,5ꢀTris(1,3,5ꢀtriphenylbenzeneꢀ4´ꢀyl)benzene (4). The
yield was 21.7%, m.p. 118 С. Found (%): С, 94.73; Н, 5.22.
С78Н54. Calculated (%): С, 94.55; Н, 5.45.
pꢀBromoacetophenone, pꢀiodoacetophenone (Aldrich, 98%),
aluminum(III) chloride (Aldrich, 99.9%), phenylboronic acid
(Merck), 2,2´ꢀbipyridyl (bpy) (Aldrich, 99%), and zinc dust
(Aldrich, 98%, <10 m) were used without additional purificaꢀ
tion. Nickel(II) chloride was dried for 8 h in a dry HCl flow at
600 С. Triphenylphosphine (Aldrich, 99%) was purified by reꢀ
crystallization from hexane and dried for 12 h in vacuo (0.133 Pa).
Solvents were dried under the corresponding reagents and
distilled under argon prior to use. The Niꢀcatalyzed polyꢀ
condensation was carried out in Schlenk tubes in a dry argon
atmosphere. The catalysts were added in an argon flow. TLC on
Silufol UVꢀ254 plates were used to monitor the reaction course
and purity of isolated products. Column chromatography was
carried out using silica gel (Aldrich, 70—230 mesh).
1,3,5ꢀTris(4´´ꢀbromodiphenylꢀ4´ꢀyl)benzene (5) was purified
using column chromatography (silica gel, benzene—ethanol
(12 : 1), Rf = 0.9) followed by recrystallization from a dioxane—
ethanol (20 : 1) mixture. The yield was 42%, white powder, m.p.
279 С. Found (%): С, 65.48; Н, 3.16; Br, 31.36. С42Н27Br3.
1
Calculated (%): С, 65.34; Н, 3.50; Br, 31.11. Н NMR (600
MHz, CDCl3), : 7.90 (s, 3 Н); 7.83 (d, 6 Н, J = 8.2 Hz); 7.72
(d, 6 Н, J = 8.2 Hz); 7.63 (d, 6 Н, J = 8.4 Hz); 7.56 (d, 6 Н,
J = 8.4 Hz). MS (EI), m/z: 773.5 [M]+.
1,3,5ꢀTris[(pꢀterphenyl)ꢀ4´´´ꢀyl]benzene (6).20 A Schlenk
tube was evacuated several times and filled with argon. Then,
compound 5 (0.463 g, 0.6 mmol), phenylboronic acid (0.366 g,
3.0 mmol), freshly distilled THF and DMSO (8 and 0.8 mL,
respectively), and 2 М aqueous К2СО3 (0.8 mL) were placed
into the tube. The Schlenk tube was evacuated several times, and
Pd[PPh3]4 (0.029 g, 0.025 mmol) was added. The synthesis was
performed in an argon atmosphere at 60 С for 48 h. After the
end of the reaction, the solution was extracted with chloroform
and washed with 2 М HCl and water, dried over calcium chloride,
and evaporated on a rotary evaporator. The product was purified
using column chromatography (silica gel, chloroform, Rf = 0.9).
The yield was 0.052 g (11%), white powder, m.p. 282 С. Found (%):
С, 94.05; Н, 5.95. С60Н42. Calculated (%): С, 94.36; Н, 5.64.
1Н NMR (600 MHz, CDCl3), : 7.95 (s, 3 Н); 7.88 (d, 6 Н,
J = 8.2 Hz); 7.83 (d, 6 Н, J = 8.2 Hz); 7.80 (d, 6 Н, J = 8.2 Hz); 7.75
(d, 6 Н, J = 8.2 Hz); 7.70 (d, 6 Н, J = 7.7 Hz); 7.51 (t, 6 Н,
J = 7.6 Hz); 7.40 (t, 3 Н, J = 7.4 Hz). MS (EI), m/z: 762.6 [M]+.
Oligophenylene Pꢀ1. A Schlenk tube was preliminarily alꢀ
ternately evacuated five times and filled with argon. Then 1,3,5ꢀtriꢀ
To obtain dry deoxygenated argon, it was passed through
three consequently connected columns packed with Al2O3, catꢀ
alyst, and molecular sieves (pore size ~4Å).
1
The H and 13С NMR spectra and 2D COSY, HSQC, and
HMBC correlations were recorded on a Bruker AMꢀ600 pulse
spectrometer (working frequency 600.12 MHz) with the Fourier
transform and broadꢀband spinꢀspin proton decoupling. Soluꢀ
tions of the samples in deuterated chloroform were used. Chemꢀ
ical shifts were measured relatively to hexamethyldisiloxane
(HMDS,
 1.94) with an accuracy of 0.01 ppm, and spinꢀspin
coupling constants (J) were measured with an accuracy of 0.1 Hz.
According to published data,19 cyclotrimers 1—5 were synꢀ
thesized by the cyclocondensation of the corresponding acetylꢀ
aromatic compounds in a solution of dry benzene at 20 С at the
molar concentration of the starting monoacetyl compound in
the presence of triethyl orthoformate (1.2 mol) passing the HCl

2244
Russ.Chem.Bull., Int.Ed., Vol. 62, No. 10, October, 2013
Khotina et al.
(pꢀbromophenyl)benzene (2) (1.086 g, 2 mmol) and the catalytic
system containing NiCl2 (0.012 g, 0.1 mmol), Ph3P (0.052 g,
0.2 mmol), bpy (0.015 g, 0.1 mmol), and Zn (0.392 g, 6.0 mmol)
were loaded. The Schlenk tube was evacuated once more and
filled with argon, and freshly distilled DMF (5 mL) was added in
an argon countercurrent. The reaction was carried out in argon
at 70 С with vigorous stirring. In 10 min, the reaction mixture
gained a redꢀbrown color, indicating the in situ formation of the
catalytic Ni0 complex. In 30 min after the beginning of the reacꢀ
tion, freshly distilled bromobenzene (0.63 mL, 0.06 mmol) was
added to the reaction solution, and the reaction was continued
for 2 h more. After the end of the reaction, the solution was
extracted with chloroform, the catalyst was filtered off, and the
filtrate was evaporated on a rotary evaporator (before precipitaꢀ
tion). The product was precipitated to methanol, filtered off,
washed with 2 М HCl and methanol, and dried for 13 h in vacuo
(0.133 Pa) at ~20 С. A light beige powder was obtained.
Found (%): Br, 21.98.
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Received September 5, 2012;
in revised form July 29, 2013