One-pot homo- and cross-coupling of diazanaphthalenes via C-H substitution: Synthesis of Bis- and Tris-diazanaphthalenes

Article abstract of DOI:10.1002/jhet.4111

The transition metal-free coupling reactions of unactivated diazanaphthalenes were studied using only lithium tetramethylpiperidine (LiTMP) reagent. Symmetrical and nonsymmetrical bis-diazanaphthalenes were synthesized in moderate to high yield by homo- and cross-coupling of related monomers. In addition, the single-step synthesis of diquinoxalino [2,3-a: 2', 3'c] phenazine and 2,2': 3', 2″ - terquinoxaline using the appropriate equivalent amount of LiTMP was performed. The products were characterized by means of NMR spectroscopy and HRMS spectrometry.

Full text of DOI:10.1002/jhet.4111

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One-Pot Homo- and Cross-Coupling of Diazanaphthalenes
via C-H Substitution: Synthesis of Bis- and Tris-
Diazanaphthalenes
Sefa Ucar, Arif Dastan*
Abstract: The transition metal-free coupling reactions of unactivated
Although these methods work well for a few derivatives, it is not
possible to synthesize many specific dimeric diazanaphthalenes
when 1,2-aminoaldehydes (or 1,2-diamines) and suitable
carbonyl compounds are used as starting materials.
diazanaphthalenes
were
studied
using
only
lithium
and
tetramethylpiperidine
(LiTMP)
reagent.
Symmetrical
nonsymmetrical bis-diazanaphthalenes were synthesized in
moderate to high yield by homo- and cross-coupling of related
monomers. In addition, the single-step synthesis of diquinoxalino
[2,3-a: 2', 3'c] phenazine and 2,2': 3', 2''- terquinoxaline using the
appropriate equivalent amount of LiTMP was performed. The
products were characterized by means of NMR spectroscopy and
HRMS spectrometry.
Introduction
Diazanaphthalenes are
heterocyclic aromatic
a
significant class of benzenoid
compounds. There are ten
diazanaphthalene derivatives in the isomeric structure (Figure 1)
and compounds derived from them have a wide range of
applications in material sciences[1] and medicinal chemistry[2]
and this has stimulated the discovery and development of novel
molecules based on diazanaphthalene and new synthetic
methods. On the other hand, dimeric diazanaphthalenes are
most widely used in coordination chemistry due to their
exceptional ligand capacity.[3] They have been extensively used
as versatile building blocks in the fields of analytical, photo-,
supra-, nano-, and macromolecular chemistry applications.[1d, 4]
For this reason, there has been tremendous interest in synthesis
of diazanaphthalene derivatives, especially dimeric forms of
these compounds.
Consequently, significant efforts have been made to develop
efficient methods for the synthesis of diazanaphthalenes and
their derivatives. There are some known methods in the
literature for the synthesis of dimeric diazanaphthalenes.
However, the numbers of known dimers are limited. The
traditional method relies on condensation of 1,2-aminoaldehydes
(or 1,2-diamines) with suitable carbonyl compounds.[1a, 3c, e, 4b, 5]
Figure 1. Diazanaphthalene derivatives in the isomeric structure
Another method for the synthesis of dimeric diazanaphthalenes
in the literature is coupling reactions using transition metal-
containing
catalysts
and
halogen-containing
starting
compounds.[6] For example, the first and sole synthesis of 2,2'-
bi-1,5-naphthyridine was achieved in 22% yield using Ni
(PPh3)2Br2 over 2-chloro-1,5-naphthyridine.[3b] Likewise, 1,1'-bi-
2,7-naphthyridine
was
synthesized
over
1-bromo-2,7-
naphthyridine, which was synthesized in several steps, in 49%
yield under Pd(OAc)2 catalysis.[3a] The use of transition metals,
low yields, and the synthesis of halogenated diazanaphthalenes
in several steps make the method useless. Generally, transition
metals are expensive and toxic to the environment. Removing
traces of transition metals from such dimers is challenging,
laborious, and expensive because of the extremely strong
metallic coordination. The disadvantages of condensation and
coupling reactions used in the synthesis of dimeric
diazanaphthalenes have led investigators to study more efficient
methods for the synthesis of related compounds. In this context,
further methods have been developed in which the unsubstituted
starting compounds are dimerized directly.[7] Quinoxaline and
cinnoline have been used in related studies, but the synthesis of
[a]
Sefa Uçar, Arif Daştan
Institution
Department of
Chemistry, Faculty of Sciences, Atatürk
University, Erzurum 25240, Turkey.
E-mail: adastan@atauni.edu.tr
Title(s), Initial(s), Surname(s) of Author(s)
Department
[b]
Institution
Address 2
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other diazanaphthalene dimers was not included. In some
reactions, although 2,2'-bi-quinoxaline was synthesized in high
yield, synthesis of 4,4'-bi-cinnoline was only achieved in 2.5%
yield (Scheme 1).[7b]
increased the efficiency of the reaction (Table 1, entry 7 and 9).
We changed bases, and we observed that the efficiency of
reaction decreased when n-BuLi replaced with t-BuLi (Table 1,
entry 8). Consequently, the optimized conditions entail the use
of TMPH with n-BuLi in THF at -78°C.
Table 1. Optimization of reaction conditions.[a]
entry
base 1
n-BuLi
t-BuLi
n-BuLi
n-BuLi
n-BuLi
n-BuLi
n-BuLi
t-BuLi
n-BuLi
base 2[b]
-
solvent
THF
Yield (%)[c]
n.d.
n.d.
n.d.
n.d.
n.d.
56
1
2
3
4
5
6
7
8
9
-
THF
DIPA
t-BuOK
PPR
THF
THF
Scheme 1. Method for the synthesis of bis-diazanaphthalenes
THF
TMPH
TMPH
TMPH
TMPH
Et2O
Similarly, in the synthesis carried out with Grignard reagent,
2,2':3',2''-terquinoxaline was also synthesized in very low
yield.[7a] A similar process was first used in the dimerization of
1,8-naphthyridine and 2,2'-bi-1,8-naphthyridine was synthesized
in 69% yield.[8] Recently, a new and efficient method for the
homocoupling reactions of inactivated electron-deficient aza
arenes has been published by Da and co-workers.[9] In this
Et2O/THF
THF
85
94
THF
99
[a] General conditions (unless otherwise specified): 5 (0.38 mmol), base 1
(0.46 mmol), base 2 (0.5 mmol), solvent (10.0 mL), -78°C (2h), rt (12 h). [b]
DIPA is diisopropylamine, t-BuOK is potassium tert-butoxide, PPR is
piperidine and TMPH is 2,2,6,6-tetramethylpiperidine, respectively. [c]
Isolated yield. (n.d.= No detected any trace of target molecule).
method,
they
used
TMPMgCl
together
with
tetramethylethylenediamine (TMEDA) (1.0 equiv.) as an additive.
The present paper describes modification of the method of Da
and co-workers[9] without using any additive and the effective
synthesis of new and known bis-diazanaphthalenes. In the
present study, LiTMP was freshly prepared in situ by reaction of
2,2,6,6-tetramethylpiperidine (TMPH) with n-BuLi before the C-H
substitution reaction, and it was used for the coupling of
electron-deficient unactivated diazanaphthalenes.
Synthesis of Dimeric Diazanaphthalenes
Composed of the Same Units
The reaction of isomeric diazanaphthalene derivatives (1-6) with
LiTMP resulted in the formation of homocoupling products (11-
16) in 45-99% yields depending on the structures of the
monomers as shown in Table 2. As seen in table 2, the reaction
yields of dimer is change between 45-99%. This difference is
mainly related to count of the active C-H atoms on monomers.
Generally, C-H atoms at α position of nitrogen is more active
both for nucleophilic attach and C-H activation. Compound 2
has one type active α hydrogen atom, and statically one type
dimer is possible, and the yield of dimer is quite higher. Whereas
monomers 1 and 3 have more unidentical active α C-H and, thus
statistically formation of many kind of by-products is possible.
Monomer 5 has also two different active C-H carbon. Formation
of only one product in 99% yield show that product via C-H atom
between two nitrogen atoms in compound 5 is not favorable due
Results and Discussion
In this work, lithium 2,2,6,6-tetramethylpiperidine (LiTMP) was
used for the C-H substitution reaction to obtain heteroaromatic
dimers and trimers. LiTMP was produced in a reaction flask by
treatment of n-BuLi with TMP. First, we conducted an
optimization study adopting quinazoline (5) as a model substrate
(Table 1). Initially, the reaction was carried out with n-BuLi or t-
BuLi in THF at -78 °C. No any trace of product formation was
observed under these conditions (Table 1, entry 1 and 2). We
observed the reaction doesn’t work by mixing of DIPA, t-BuOK
or PPR with n-BuLi. (Table 1, entry 3, 4 and 5). The using of
TMPH with n-BuLi in Et2O gave the desired product, 15, in %56
yield (Table 1, entry 6). The using of THF instead of Et2O
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to crowded four adjacent nitrogen atoms in the possible products. and proton Hd (‘Hd) was about 8.0 Hz. The coupling constant
Dimerization via β C-H atom in compound 6 approve this
hypothesis.
between visually interacting He (‘He) and Hf (‘Hf) was about 5.5
Hz. In such systems, it is clear that the coupling constant
between hydrogen atoms close to electronegative atoms
decreases with inductive effect. These generalizations related to
chemical shift values and coupling constants played an
important role in determining the absolute structures of other
diazanaphthalene dimers synthesized in the present study.
Table 2. Reactions of diazanaphthalenes (1-6) with LiTMP
Scheme 2. Coupling constants of protons in diazanaphthalene rings.
The dimeric product resulting from the reaction of 1,8-
naphthyridine (2) with LiTMP is understood to be symmetrical
1
from the number of signals observed in the H- (5 signal) and
13C-NMR (8 signal) spectra. In this case, there are three different
possible structures (2-2’-, 3,3’-, or 4,4’-bi-1,8-naphthyridine) for
the dimeric compound. When the coupling constants of the
product were examined, the value was found to be 8.4 Hz. This
proves that the structure is strictly 2,2'-bi-1,8-naphthyridine (12).
If the compound were 3,3'-bi-1,8-naphthyridine, the coupling
constant would be about 1.5-2 Hz, and it were 4,4'-bi-1,8-
naphthyridine, the value would be about 4-6 Hz. The absolute
structure of 1,1'-2,6-naphthyridine (13) resulting from the
reaction of 2,6-naphthyridine (3) with LiTMP was determined
[a] Isolated yield. No side product was detected.
The structure of 8,8'-bi-1,7-naphthyridine (11) obtained from the
reaction of 1,7-naphthyridine (1) with LiTMP was elucidated by
means of NMR spectroscopy. The five different signals observed
1
based on the observation of one singlet signal in the H-NMR
spectrum. The structures of 1,1’-2,7-naphthyridine (14)[3a], 4,4’-
biquinazoline (15)[10], and 4,4'-bicinnoline (16)[7b] were confirmed
by comparing the available spectra with the literature data.
The reaction of 1,6-naphthyridine (7) with LiTMP led to the
formation of symmetrical and nonsymmetrical dimers by the
activation of nonidentical positions in the monomer as shown in
Scheme 3. When the corresponding protons were paired with
the signals observed in the 1H-NMR spectrum of dimer 18, it was
clearly determined that the vicinal coupling constant between Hx
and Hy protons (Scheme 3) was 8.7 Hz. This value indicates that
the structure is as shown in Scheme 3.
1
in the H-NMR spectrum of the product and the eight different
signals observed in the 13C-NMR spectrum reveal that the
product has a symmetrical structure. In these reaction conditions,
there are six different possibilities for the open structure of the
molecule. The fact that no proton resonating as a singlet is
observed in the 1H-NMR spectrum clearly indicates that the
binding occurs at the 8-8’- position, because the only proton that
can resonate as a singlet in the relevant skeleton is attached to
carbon atom number eight. The result of the analysis performed
by HRMS spectroscopy is also compatible with the
recommended dimeric structure.
1
When the H-NMR spectra of 1,7-naphthyridine (1) and 8-8’-bi-
1,7-naphthyridine (11) are examined in detail, it is seen that all
protons bound to carbon atoms adjacent to electronegative
nitrogen atoms in the molecule resonate in lower areas than the
others because of the inductive effect of nitrogen atoms. The
protons Ha, Hc (‘Hc) and He (‘He) are bound to carbon atoms
adjacent to the nitrogen atoms and all of their signals are in the
area below around 8.5 ppm. Another remarkable detail about the
same spectra is the coupling constants between protons. The
coupling constant of proton Hb (‘Hb) with proton Hc (‘Hc), which
bonded the carbon that is close to the nitrogen atom, was about
4.0 Hz. However, the coupling constant between proton Hb (‘Hb)
Scheme 3. Reaction of 1,6-naphthyridine with LiTMP.
1,5-Naphthyridine (9) and phthalazine (10) could not be
dimerized with LiTMP. In 1,5-naphthyridine (9), the reason for
the failure of the reaction is not that 1,5-naphthyridine (9) and
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LiTMP do not react, but the resulting litho 1,5-naphthyridine
cannot participate in 1,5-naphthyridine, which should act as an
electrophile. As a matter of fact, as explained below, cross-
dimerization reactions of 1,5-naphthyridine (9) with some other
diazanaphthalene derivatives were performed and the products
were obtained. The reaction of phthalazine (10) under different
conditions resulted in the formation of a viscous black crude
product each time. 1H-NMR analysis of this content revealed that
all the phthalazine signals disappeared. However, none of the
products formed could be isolated, despite the use of many
different separation techniques.
Table 3. Synthesis of cross-dimerization products
The reaction of quinoxaline (8) with LiTMP under different
conditions resulted in the formation of
a dimer (19), a
noncyclized trimer (20), and a cyclized trimer (21) in good yields
as shown in Scheme 4.
[a] The side products were homodimers. [b] The side products were 4,8-
di(1,8-naphthyridin-2-yl)-1,5-naphthyridine (15%) (29) and 2,2'-bi(1,8-
naphthyridine) (10%) (12). [c] The side products were 3-(1,8-naphthyridin-2-
yl)-2,2'-biquinoxaline (30) and homodimers.
The results of the studies on the synthesis of dimeric
diazanaphthalene dimers consisting of the same units were of
great benefit in determining the structures of the cross-
dimerization products. These results indicate which position of
the diazanaphthalene rings is active under the respective
reaction conditions. It was therefore understood at which
position the rings were attached in the cross dimers. In
addition, the coupling constants extracted from the product’s
1H-NMR spectra proved the accuracy of the structures. In
particular, since the self-dimerization reaction of 1,5-
naphthyridine does not work, it is thus determined which
position is active in the cross-dimerization reactions, to wit
where binding occurs. For example, it was understood from
the coupling constant of 4.2 Hz that the 1,5-naphthyridine unit
was bonded at carbon 4 in dimer 22, which was formed by the
reaction of 1,5-naphthyridine (9) with quinazoline (5) (Table 3,
Entry 1). Since it is known that carbon 4 of the quinazoline
unit is also active, it turns out that the absolute structure is 4-
(1,5-naphthyridin-4-yl) quinazoline (22). As in this example, in
all other cross-dimerization products containing 1,5-
naphthyridine units, the coupling was at carbon four. The lack
of self-dimerization of 1,5-naphthyridine positively affected the
regioselectivity in cross-dimerization reactions. The procedure
was modified to ensure this situation. LiTMP was first reacted
with 1,5-naphthyridine and then the other diazanaphthalene
derivative was reacted.
Scheme 4. Reaction of quinoxaline with LiTMP.
Synthesis of Dimeric Diazanaphthalenes
Composed of Different Units
Finally, cross-dimerization reactions were studied and the
targeted diazanaphthalene dimers were successfully obtained in
30-70% yields by cross-coupling reactions as shown in Table 3.
As expected in the reactions, dimeric diazanaphthalenes
composed of the same units were formed as side products.
Furthermore, noncyclized trimers (27, 30) were formed from the
reactions of 1,8-naphthyridine (2) with 1,5-naphthyridine (9)
(Table 3, Entry 5) and quinoxaline (8) (Table 3, Entry 7).
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The synthesis of homo-dimer 15 was attempted on a gram
scale, where 1.5 g of quinazoline (5) was successfully
converted into the 15 (1.48 g, 99% yield, Scheme 5). This
result clearly demonstrates the practical applicability of the
developed methodology.
halogen-containing starting compounds or transition metal-
containing catalysts were needed. The oxidation of the products
obtained was carried out with air oxygen. In addition to dimeric
products, some non-cyclized and cyclized trimers were also
synthesized successfully.
Experimental Section
General Information
All reactions were performed under an argon or nitrogen atmosphere.
Solvents were dried according to the established procedures prior to use.
Reactions were monitored by thin layer chromatography (TLC) / or 1H
NMR spectroscopy, column chromatography purifications were carried
out using silica gel. All reagents were purchased from commercial
corporations unless otherwise stated. LiTMP was freshly prepared from
n-BuLi and TMPH (2,2,6,6-tetramethylpiperidine). The high‐resolution
mass spectrometry (HRMS) analysis was carried out using an
atmospheric pressure chemical ionization‐time of flight (APCI‐TOF) mass
spectrometer. 1H and 13C NMR spectra were recorded with
tetramethylsilane as an internal stan-dard at ambient temperature with
Bruker and Varian 400 MHz instruments at 400 MHz for 1H NMR and 100
MHz for 13C NMR spectroscopy. Apparent splitting is given in all cases in
ppm and coupling constants J in Hz. While quinoxaline, phthalazine and
Scheme 5. Scale-Up experiment for the synthesis of 15.
We propose following general reaction mechanism for the
homo-coupling of 5 as illustrated in scheme 6 in the light of
literature. [7]
quinazoline were commercially available, 1,5-[11], 1,6-[12], 1,7-[13], 1,8-[12]
,
2,6-[13], 2,7-[13] naphthyridines and cinnoline[14] were synthesized using
the literature methods.
General Procedure for coupling reactions
LiTMP was freshly prepared from n-BuLi in hexane (2.5 M solution) and
TMPH (2,2,6,6-tetramethylpiperidine). Under an argon atmosphere, at -
10 ºC, TMPH was introduced into a dry two-necked round-bottom flask
and n-BuLi in hexane were added. THF was introduced. The mixture was
cooled to -78ºC by liquid nitrogen-acetone cooling system and stirred for
10 min. Then the diazanaphthalene was added slowly at -78ºC as a THF
solution. The reaction mixture was vigorously stirred for 2h. The mixture
was allowed to warm to r.t. and stirred for overnight under an argon
atmosphere. After completion of the reaction, THF were concentrated in
vacuum to give the crude product. The resulting product was purified by
silica gel column chromatography or crystallization.
Scheme 6. Proposed reaction mechanism.
Diazanaphthalene A and Diazanaphthalene B were added as a mixture
on LiTMP in cross-dimerization reactions (Table 2, Entry 2,6 and 7). If
one of the monomers is 1,5-naphthyridine (Table 2, Entry 1,3,4 and 5), it
is added first, stirred for 1 h at -78°C, then the other derivative is
introduced.
Quinazoline (5) is lithiated to form I first. The lithiated quinazoline I is then
added to the non-lithiated quinazoline (5) to form intermediate II. Finally,
homo-dimer 15 is formed as a result of aromatization with help of air
oxygen.
8,8'-Bi(1,7-naphthyridine) (11):
The product 11 was prepared according to general procedure using
TMPH (100.0 mmL, 0.6 mmol), n-BuLi (220.0 mmL, 0.55 mmol) and 1,7-
naphthyridine (65.0 mg, 0.5 mmol). After column chromatography
(CH2Cl2/MeOH, 95:5), the product was obtained as a white solid (30.0
mg, 45%; m.p. = 113-115 °C). 1H NMR (400 MHz, CDCl3) δ 8.85 (dd, J =
4.1, 1.6 Hz, 1H), 8.81 (d, J = 5.6 Hz, 1H), 8.24 (dd, J = 8.4, 1.6 Hz, 1H),
7.82 (d, J = 5.6 Hz, 1H), 7.56 (dd, J = 8.4, 4.1 Hz, 1H). 13C NMR (101
Conclusions
We have described an efficient and convenient method for the
synthesis of homo- and cross- dimeric diazanaphthalenes. All
syntheses were performed by low temperature reaction of the
aromatic ring with LiTMP. No other additives were used; no
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MHz, CDCl3) δ 160.2, 151.7, 143.1, 142.8, 134.9, 131.8, 124.9, 120.8.
HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for C16H11N4 259.0984; found
259.0981.
The product 16 was prepared according to general procedure using
TMPH (157.0 mmL, 0.92 mmol), n-BuLi (340.0 mmL, 0.85 mmol) and
cinnoline (100.0 mg, 0.77 mmol). After column chromatography
(CH2Cl2/MeOH, 49:1), the product was obtained as a black solid (65.0
mg, 65%; m.p. = 235 °C; Lit.[7b] m.p.= 235-236 ºC). 1H NMR (400 MHz,
CDCl3) δ 9.37 (s, 2H), 8.75 (d, J = 8.6 Hz, 2H), 8.02 – 7.90 (m, 2H), 7.78
– 7.66 (m, 2H), 7.47 (d, J = 8.5 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ
150.4, 144.5, 132.5, 131.3, 130.7, 128.0, 124.6, 124.0. HRMS (APCI‐
TOF) (m/z): [M + H]+ calcd for C16H11N4 259.0984; found 259.0975.
2,2'-Bi(1,8-naphthyridine) (12):
The product 12 was prepared according to general procedure using
TMPH (0.4 mL, 2.3 mmol), n-BuLi (0.9 mL, 2.1 mmol) and 1,8-
naphthyridine (250.0 mg, 1.9 mmol). After column chromatography
(EtOAC/MeOH, 9:1), the product was obtained as a brown solid (225.0
mg, 90%; m.p. = 250-251 °C; Lit.[5a] m.p. =250 ºC). 1H NMR (400 MHz,
MeOD) δ 9.18 (d, J = 4.2 Hz, 2H), 9.10 (d, J = 8.7 Hz, 2H), 8.68 (d, J =
8.7 Hz, 2H), 8.59 (d, J = 7.9 Hz, 2H), 7.75 (dd, J = 7.9, 4.2 Hz, 2H). 13C
NMR (101 MHz, CDCl3) δ 158.6, 155.8, 154.0, 138.0, 137.0, 123.5,
122.6, 121.1. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for C16H11N4
259.0984; found 259.0920.
5,5'-Bi(1,6-naphthyridine) (17) and 2,5'-Bi(1,6-
naphthyridine) (18):
The products 17 and 18 were prepared according to general procedure
using TMPH (0.41 mL, 2.4 mmol), n-BuLi (0.87 mL, 2.2 mmol) and 1,6-
naphthyridine (520.0 mg, 4.0 mmol). After column chromatography
(CH2Cl2/MeOH, 19:1), in the firs fraction, the product 18 was obtained as
a white solid (88.0 mg, 17%; m.p. = 259-261 °C). 1H NMR (400 MHz,
CDCl3) δ 9.48 (d, J = 8.7 Hz, 1H), 9.40 (s, 1H), 9.15 (dd, J = 4.2, 1.7 Hz,
1H), 8.93 (d, J = 5.9 Hz, 1H), 8.86 (d, J = 5.9 Hz, 1H), 8.53 (d, J = 8.7 Hz,
1H), 8.48 (d, J = 8.7 Hz, 1H), 8.07 (d, J = 6.0 Hz, 1H), 8.05 (d, J = 6.0 Hz,
1H), 7.62 (dd, J = 8.7, 4.2 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 161.6,
156.5, 154.7, 152.8, 151.6, 149.5, 147.5, 145.6, 136.6, 136.5, 124.2,
123.7, 123.1, 122.9, 122.7, 122.3. HRMS (APCI‐TOF) (m/z): [M + H]+
calcd for C16H11N4 259.0984; found 259.0984. In the second fraction, the
product 17 was obtained as a white solid (72.0 mg, 14%; m.p. = ˃˃
300 °C). 1H NMR (400 MHz, CDCl3) δ 9.15 (dd, J = 4.2, 1.5 Hz, 1H), 8.94
(d, J = 5.9 Hz, 1H), 8.44 (d, J = 8.6 Hz, 1H), 8.11 (d, J = 5.9 Hz, 1H), 7.51
(dd, J = 8.6, 4.2 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 157.6, 154.9,
151.5, 145.3, 135.6, 123.4, 123.0, 122.9. HRMS (APCI‐TOF) (m/z): [M +
H]+ calcd for C16H11N4 259.0984; found 259.0979.
1,1'-Bi(2,6-naphthyridine) (13):
The product 13 was prepared according to general procedure using
TMPH (315.0 mmL, 1.85 mmol), n-BuLi (675.0 mmL, 1.7 mmol) and 2,6-
naphthyridine (200.0 mg, 1.55 mmol). After crystallization (CH2Cl2/EtOH,
95:5), the product was obtained as a white solid (143.0 mg, 72%; m.p. =
˃˃ 300 °C). 1H NMR (400 MHz, CDCl3) δ 9.48 (d, J = 0.8 Hz, 2H), 8.93 (d,
J = 5.7 Hz, 2H), 8.68 (d, J = 6.0 Hz, 2H), 7.98 (d, J = 5.7 Hz, 2H), 7.86 (d,
J = 6.0 Hz, 2H). 13C NMR (101 MHz, CDCl3) δ 156.0, 152.3, 145.3, 143.4,
131.4, 129.6, 120.2, 118.7. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for
C16H11N4 259.0984; found 259.0990.
1,1'-Bi(2,7-naphthyridine) (14):
2,2'-Biquinoxaline (19):
The product 14 was prepared according to general procedure using
TMPH (160.0 mmL, 0.95 mmol), n-BuLi (340.0 mmL, 0.85 mmol) and
2,7-naphthyridine (100.0 mg, 0.77 mmol). After column chromatography
(CH2Cl2/MeOH, 9:1), the product was obtained as a white solid (62.0 mg,
The product 19 was prepared according to general procedure using
TMPH (0.45 mL, 2.7 mmol), n-BuLi (0.92 mL, 2.3 mmol) and quinoxaline
(500.0 mg, 3.85 mmol). After column chromatography (EtOAc/hexane,
3:7), the product was obtained as a yellow solid (220.0 mg, 45%; m.p. =
293-295 °C; Lit.[7e] m.p.= 293-295 ºC). 1H NMR (400 MHz, CDCl3) δ
10.14 (s, 2H), 8.30 – 8.24 (m, 2H), 8.24 – 8.19 (m, 2H), 7.89 – 7.82 (m,
4H). 13C NMR (101 MHz, CDCl3) δ 148.6, 144.3, 142.9, 141.7, 130.9,
130.6, 130.0, 129.5. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for
C16H11N4 259.0984; found 259.0921.
1
62%; m.p. = ˃˃ 300 °C). H NMR (400 MHz, CDCl3) δ 9.47 (s, 1H), 8.92
(d, J = 5.7 Hz, 1H), 8.78 (d, J = 5.7 Hz, 1H), 7.84 (d, J = 5.7 Hz, 1H), 7.79
(d, J = 5.7 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 157.6, 152.5, 146.9,
145.5, 139.7, 123.0, 120.1, 119.3. HRMS (APCI‐TOF) (m/z): [M + H]+
calcd for C16H11N4 259.0984; found 259.0927.
4,4'-Biquinazoline (15):
2,2':3',2''-Terquinoxaline (20):
The product 15 was prepared according to general procedure using
TMPH (2.5 mL, 15.0 mmol), n-BuLi (5.5 mL, 14.0 mmol) and quinazoline
(1.5 g, 11.5 mmol). After crystallization (EtOAc), the product was
obtained as a white solid (1.48 g, 99%; m.p. = 210 °C; Lit.[10] m.p. = 210-
The product 20 was prepared according to general procedure using
TMPH (0.92 mL, 5.4 mmol), n-BuLi (2.0 mL, 5.0 mmol) and quinoxaline
(500.0 mg, 3.85 mmol). After column chromatography (EtOAc/hexane,
1:4), in the firs fraction, the product 19 was obtained (50.0 mg, 10%). In
the second fraction the product 20 was obtained as a orange solid (400.0
mg, 80%; m.p. = 234 °C; Lit.[15] m.p.= 234-235 ºC). 1H NMR (400 MHz,
CDCl3) δ 9.63 (s, 2H), 8.33 (AA’ part of AA’BB’ system, 2H), 8.14 (d, J =
8.1 Hz, 2H), 7.94 (BB’’ part of AA’BB’ system, 2H), 7.73 (t, J = 7.6 Hz,
2H), 7.59 (t, J = 7.6 Hz, 2H), 7.51 (d, J = 8.1 Hz, 2H). 13C NMR (101 MHz,
CDCl3) δ 151.5, 150.3, 146.0, 141.9, 141.5, 141.1, 131.8, 130.7, 130.4,
129.9, 129.5, 129.3. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for
C24H14N6 387.1358; found 387.1281.
1
212 ºC). H NMR (400 MHz, CDCl3) δ 9.55 (s, 2H), 8.23 (d, J = 8.4 Hz,
2H), 8.00 (t, J = 7.7 Hz, 2H), 7.93 (d, J = 8.4 Hz, 2H), 7.64 (t, J = 7.7 Hz,
2H). 13C NMR (101 MHz, CDCl3) δ 163.5, 154.1, 151.4, 134.6, 129.1,
128.6, 126.4, 123.5. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for
C16H11N4 259.0984; found 259.0933.
4,4'-Bicinnoline (16):
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Diquinoxalino[2,3-a:2',3'-c]phenazine (21):
2-(1,5-Naphthyridin-4-yl)quinoxaline (25):
The product 21 was prepared according to general procedure using
TMPH (1.6 mL, 9.2 mmol), n-BuLi (3.55 mL, 8.85 mmol) and quinoxaline
(500.0 mg, 3.85 mmol). After crystallization (MeOH), the product was
obtained as a green solid (450.0 mg, 90%; m.p. = ˃˃ 300 °C). 1H NMR
(400 MHz, CDCl3) δ 8.70 (AA’ part of AA’BB’ system, 6H), 8.06 (BB’ part
of AA’BB’ system, 6H). 13C NMR (101 MHz, CDCl3) δ 143.8, 143.8, 132.5,
130.9. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for C24H12N6 385.1202;
found 385.1199.
The product 25 was prepared according to general procedure using
TMPH (0.78 mL, 4.6 mmol), n-BuLi (1.7 mL, 4.25 mmol), 1,5-
naphthyridine (500.0 mg, 3.85 mmol) and quinoxaline (500.0 mg, 3.85
mmol). After column chromatography (Et2O/EtOAc, 9:1), in the first
fraction roduct 19 was obtained (100.0 mg, 10%). In the second fraction
the product 25 was obtained as a white solid (400.0 mg, 40%; m.p. =
1
205 °C). H NMR (400 MHz, CDCl3) δ 9.77 (s, 1H), 9.21 (d, J = 4.3 Hz,
1H), 9.06 (dd, J = 4.1, 1.6 Hz, 1H), 8.55 (dd, J = 8.5, 1.6 Hz, 1H), 8.25 (d,
J = 4.3 Hz, 1H), 8.21-8.23 (m, 2H), 7.88 – 7.81 (m, 2H), 7.75 (dd, J = 8.5,
4.1 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 151.5, 151.4, 150.5, 148.0,
144.5, 143.6, 142.6, 141.9, 141.4, 137.9, 130.5, 130.2, 129.8, 129.3,
125.0, 124.6. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for C16H11N4
259.0984; found 259.0991.
4-(1,5-Naphthyridin-4-yl)quinazoline (22):
The product 22 was prepared according to general procedure using
TMPH (0.78 mL, 4.6 mmol), n-BuLi (1.7 mL, 4.25 mmol), 1,5-
naphthyridine (500.0 mg, 3.85 mmol) and quinazoline (500.0 mg, 3.85
mmol). After column chromatography (Et2O/EtOAc, 1:1), in the first
fraction roduct 15 was obtained (149.0 mg, 15%). In the second fraction
the product 22 was obtained as a white solid (446.5 mg, 45%; m.p. =
4-(1,8-Naphthyridin-2-yl)-1,5-naphthyridine
(26):
1
169-170 °C). H NMR (400 MHz, CDCl3) δ 9.51 (s, 1H), 9.20 (d, J = 4.2
The product 26 was prepared according to general procedure using
TMPH (0.78 mL, 4.6 mmol), n-BuLi (1.7 mL, 4.25 mmol), 1,5-
naphthyridine (500.0 mg, 3.85 mmol) and 1,8-naphthyridine (500.0 mg,
3.85 mmol). After column chromatography (CH2Cl2/MeOH, 24:1), in the
first fraction the product 26 was obtained as a white solid (350.0 mg,
35%; m.p. = 206-207 °C). 1H NMR (400 MHz, CDCl3) δ 9.20 (dd, J = 4.2,
2.0 Hz, 1H), 9.18 (d, J = 4.5 Hz, 1H), 9.05 (dd, J = 4.1, 1.7 Hz, 1H), 8.59
(d, J = 8.4 Hz, 1H), 8.54 (dd, J = 8.5, 1.7 Hz, 1H), 8.44 (d, J = 4.5 Hz, 1H),
8.36 (d, J = 8.4 Hz, 1H), 8.31 (dd, J = 8.2, 2.0 Hz, 1H), 7.72 (dd, J = 8.5,
4.1 Hz, 1H), 7.57 (dd, J = 8.2, 4.2 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ
158.5, 156.2, 153.9, 151.5, 150.9, 145.1, 144.5, 141.6, 138.0, 136.8,
136.3, 126.1, 125.6, 124.2, 122.6, 122.5. HRMS (APCI‐TOF) (m/z): [M +
H]+ calcd for C16H11N4 259.0984; found 259.0993. In the second fraction
the product 29 was obtained as a white solid (110.0 mg, 15%; m.p. =
˃˃300 °C; Lit.[3c] m.p. = ˃˃ 300 ºC). 1H NMR (400 MHz, CDCl3) δ 9.22 (d,
J = 4.3 Hz, 1H), 9.21 (dd, J = 4.1, 1.9 Hz, 1H), 8.60 (d, J = 8.4 Hz, 1H),
8.46 (d, J = 4.3 Hz, 1H), 8.39 (d, J = 8.4 Hz, 1H), 8.33 (dd, J = 8.1, 1.9
Hz, 1H), 7.59 (dd, J = 8.1, 4.1 Hz, 1H). 13C NMR (could not be obtained
because of poor solubility). HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for
C24H15N6 387.1358; found 387.1365. In the third fraction product 12 was
obtained (100.0 mg, 10%).
Hz, 1H), 8.87 (dd, J = 4.2, 1.4 Hz, 1H), 8.56 (dd, J = 8.6, 1.4 Hz, 1H),
8.18 (d, J = 8.5 Hz, 1H), 7.98 – 7.89 (m, 1H), 7.78 (d, J = 4.2 Hz, 1H),
7.71 (dd, J = 8.6, 4.2 Hz, 1H), 7.55 – 7.47 (m, 1H), 7.45 (d, J = 8.0 Hz,
1H). 13C NMR (101 MHz, CDCl3) δ 166.1, 154.6, 151.65, 151.0, 150.4,
144.4, 144.2, 141.9, 137.8, 134.1, 128.9, 127.9, 127.0, 124.9, 124.7,
124.5. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for C16H11N4 259.0984;
found 259.0999.
4-(Quinoxalin-2-yl)quinazoline (23):
The product 23 was prepared according to general procedure using
TMPH (0.35 mL, 1.9 mmol), n-BuLi (0.70 mL, 1.8 mmol), quinoxaline
(100.0 mg, 0.77 mmol) and quinazoline (100.0 mg, 0.77 mmol). After
column chromatography (Et2O/hexane, 3:7), in the first fraction roduct 23
1
was obtained as a white solid (140.0 mg, 70%; m.p. = 197 °C). H NMR
(400 MHz, CDCl3) δ 9.79 (s, 1H), 9.53 (s, 1H), 9.15 (d, J = 8.5 Hz, 1H),
8.25 – 8.29 (m, 2H), 8.18 (d, J = 8.5 Hz, 1H), 7.99 (t, J = 7.7 Hz, 1H),
7.93 – 7.86 (m, 2H), 7.76 (t, J = 7.7 Hz, 1H). 13C NMR (101 MHz, CDCl3)
δ 161.5, 154.3, 151.9, 150.6, 146.3, 142.4, 141.0, 134.1, 131.3, 130.7,
130.0, 129.5, 129.1, 128.7, 127.5, 123.2. HRMS (APCI‐TOF) (m/z): [M +
H]+ calcd for C16H11N4 259.0984; found 259.0927. In the second fraction
the product 15 was obtained (30.0 mg, 15%).
4-(1,8-Naphthyridin-2-yl)quinazoline (27):
The product 27 was prepared according to general procedure using
TMPH (0.3 mL, 1.75 mmol), n-BuLi (0.65 mL, 1.6 mmol), 1,8-
naphthyridine (150.0 mg, 1.15 mmol) and quinazoline (150.0 mg, 1.15
mmol). After column chromatography (EtOAc), in the first fraction product
15 was obtained (75.0 mg, 25%). In the second fraction the product 27
4-(2,6-Naphthyridin-1-yl)-1,5-naphthyridine
(24):
1
The product 24 was prepared according to general procedure using
TMPH (0.6 mL, 3.5 mmol), n-BuLi (1.32 mL, 3.3 mmol), 1,5-naphthyridine
(330.0 mg, 2.5 mmol) and 2,6-naphthyridine (330.0 mg, 2.5 mmol). After
column chromatography (CH2Cl2/EtOH, 19:1), in the first fraction roduct
24 was obtained as a white solid (230.0 mg, 35%; m.p. = 181-183 °C). 1H
NMR (400 MHz, CDCl3) δ 9.44 (s, 1H), 9.20 (d, J = 4.2 Hz, 1H), 8.91 (d,
J = 5.8 Hz, 1H), 8.85 (dd, J = 4.2, 1.7 Hz, 1H), 8.56 (dd, J = 8.5, 1.7 Hz,
1H), 8.55 (d, J = 5.9 Hz, 1H), 7.94 (d, J = 5.9 Hz, 1H), 7.80 (d, J = 4.2 Hz,
1H), 7.70 (dd, J = 8.5, 4.2 Hz, 1H), 7.22 (d, J = 5.8 Hz, 1H). 13C NMR
(101 MHz, CDCl3) δ 157.2, 152.3, 151.5, 151.1, 145.5, 144.7, 144.2,
144.1, 142.2, 137.8, 130.5, 129.8, 125.3, 124.8, 119.8, 119.2. HRMS
(APCI‐TOF) (m/z): [M + H]+ calcd for C16H11N4 259.0984; found 259.0996.
In the second fraction the product 13 was obtained (32.0 mg, 5%).
was obtained as a white solid (105.0 mg, 35%; m.p. = 159 °C). H NMR
(400 MHz, CDCl3) δ 9.49 (s, 1H), 9.45 (d, J = 8.5 Hz, 1H), 9.26 (dd, J =
4.2, 2.0 Hz, 1H), 8.56 (d, J = 8.5 Hz, 1H), 8.47 (d, J = 8.5 Hz, 1H), 8.34
(dd, J = 8.2, 2.0 Hz, 1H), 8.15 (d, J = 8.5 Hz, 1H), 7.97 (ddd, J = 8.5, 7.0,
1.2 Hz, 1H), 7.75 (ddd, J = 8.5, 7.0, 1.2 Hz, 1H), 7.63 (dd, J = 8.2, 4.2 Hz,
1H). 13C NMR (101 MHz, CDCl3) δ 162.8, 159.5, 155.1, 154.4, 154.1,
151.9, 138.3, 137.1, 134.0, 128.8, 128.6, 128.5, 123.4, 123.2, 123.2,
122.9. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for C16H11N4 259.0984;
found 259.0927. In the third fraction product 12 was obtained (15.0 mg,
5%).
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[2] a) S. Kobayashi, M. Ueno, R. Suzuki, H. Ishitani, H.-S. Kim and Y. Wataya,
J. Org Chem. 1999, 64, 6833-6841; b) K. M. Wildeboer-Andrud and K.
E. Stevens, Pharmacol. Biochem. Behav 2011, 100, 17-24.
[3] a) E. C. Glazer and Y. Tor, Angew. Chem. 2002, 114, 4194-4198; b) C. M.
Fitchett and P. J. Steel, Polyhedron 2007, 26, 400-405; c) A. N. Singh
and R. P. Thummel, Inorg. Chem. 2009, 48, 6459-6470; d) T. Brietzke,
W. Mickler, A. Kelling and H.-J. Holdt, Dalton Trans. 2012, 41, 2788-
2797; e) D. L. Ashford, C. R. Glasson, M. R. Norris, J. J. Concepcion, S.
Keinan, M. K. Brennaman, J. L. Templeton and T. J. Meyer, Inorg.
Chem. 2014, 53, 5637-5646.
2-(1,8-Naphthyridin-2-yl)quinoxaline (28):
The product 28 was prepared according to general procedure using
TMPH (1.0 mL, 5.75 mmol), n-BuLi (2.15 mL, 5.4 mmol), 1,8-
naphthyridine (500.0 mg, 3.85 mmol) and quinoxaline (500.0 mg, 3.85
mmol). After column chromatography (EtOAc/hexane, 4:1), in the first
fraction product 19 was obtained (59.0 mg, 12%). In the second fraction
the product 28 was obtained as a white solid (300.0 mg, 30%; m.p. =
290-291 °C). 1H NMR (400 MHz, CDCl3) δ 10.38 (s, 1H), 9.22 (dd, J =
4.2, 1.9 Hz, 1H), 8.93 (d, J = 8.5 Hz, 1H), 8.42 (d, J = 8.5 Hz, 1H), 8.30
(dd, J = 8.1, 1.9 Hz, 1H), 8.18-8.24 (m, 2H), 7.88 – 7.76 (m, 2H), 7.58 (dd,
J = 8.1, 4.2 Hz, 1H). 13C NMR (101 MHz, CDCl3) δ 157.8, 155.8, 154.2,
149.4, 144.9, 143.0, 141.7, 138.2, 137.1, 130.7, 130.3, 129.9, 129.5,
123.3, 122.8, 120.4. HRMS (APCI‐TOF) (m/z): [M + H]+ calcd for
C16H11N4 259.0984; found 259.0997. In the third fraction the product 30
was obtained as a white solid (60.0 mg, 8%; m.p. = 230-232 °C). 1H NMR
(400 MHz, CDCl3) δ 9.69 (s, 1H), 8.92 (dd, J = 4.3, 2.0 Hz, 1H), 8.43 (d, J
= 8.3 Hz, 1H), 8.37 (d, J = 8.3Hz, 1H), 8.36 – 8.32 (m, 1H), 8.30 – 8.26
(m, 1H), 8.24 (dd, J = 8.1, 2.0 Hz, 1H), 8.10 (d, J = 8.5 Hz, 1H), 7.95 –
7.88 (m, 2H), 7.70 – 7.64 (m, 1H), 7.50-7.54 (m, 1H), 7.46 – 7.40 (m, 2H).
13C NMR (101 MHz, CDCl3) δ 160.4, 155.0, 153.8, 152.5, 151.3, 150.3,
145.9, 141.7, 141.3, 141.0, 141.0, 137.8, 136.7, 131.3, 131.1, 130.1,
129.8, 129.7, 129.5, 129.3, 129.2, 122.8, 122.4, 122.1. HRMS (APCI‐
TOF) (m/z): [M + H]+ calcd for C24H15N6 387.1358; found 387.1384. In the
fourth fraction product 12 was obtained (49.0 mg, 10%).
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Mater. 2017, 29, 3971-3979; b) W.-H. Wu, M.-J. Huang, Q. Zeng, W.-R.
Xian, W.-M. Liao and J. He, Inorganic Chemistry Communications 2019,
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C. C. Cheng and S. J. Yan, Org. React. 2004, 28, 37-201; d) S.
Goswami, A. C. Maity, H. K. Fun and S. Chantrapromma, Eur. J. Org.
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Dong, G. C. Clososki, S. H. Wunderlich, A. Unsinn, J. Li and P. Knochel,
Chemistry–A European Journal 2009, 15, 457-468; e) A. Sharma, D.
Vachhani and E. Van der Eycken, Org. Lett. 2012, 14, 1854-1857; f) D.
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Acknowledgements
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[9] W. W. Xie, Y. Liu, R. Yuan, D. Zhao, T. Z. Yu, J. Zhang and C. S. Da,
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Authors are indebted to the TUBITAK (project NO: KBAG-
216Z168) for financial supports.
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Keywords: diazanaphthalene • naphthyridine • C-H
substitution • bi-naphthyridine • benzodiazine
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2000, p.
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Entry for the Table of Contents (Please choose one layout)
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The transition metal-free coupling
reactions of unactivated
Research Assistant Sefa Uçar
Prof. Dr. Arif Daştan*
diazanaphthalenes were studied
using only lithium
Page No. – Page No.
tetramethylpiperidine (LiTMP)
reagent. Symmetrical and
nonsymmetrical bis-
diazanaphthalenes were
synthesized by homo- and cross-
coupling of related monomers.
One-Pot Homo- and Cross-
Coupling of Diazanaphthalenes
via C-H Substitution: Synthesis
of Bis- and Tris-
Diazanaphthalenes
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Graphical abstract
One-Pot Homo- and Cross-Coupling of Diazanaphthalenes via C-H Substitution: Synthesis of Bis- and Tris-
Diazanaphthalenes
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