Chemistry and spectroscopy of cross-conjugated and pseudo-cross-conjugated quinolinium-ethynyl-benzoate mesomeric betaines

Article abstract of DOI:10.1515/znb-2018-0020

The three isomers 1-methylquinolinium-2-, 3-, and 4-ethynyl(phenyl-4-carboxylates) belong to two distinct types of heterocyclic mesomeric betaines. The quinolinium substituted in position 3 is a cross-conjugated mesomeric betaine (CCMB), whereas the quinolinium derivatives substituted in positions 2 and 4 are members of the class of pseudo-cross-conjugated mesomeric betaines (PCCMBs). While the charges are strictly separated within the common π-electron system of the CCMB according to the canonical formulae, the charges are effectively but not exclusively delocalized in the PCCMBs because cumulenoid resonance forms including electron sextet structures without external octet stabilization can be formed in accordance with the definition of PCCMBs. As a consequence, despite being closely related structures, the three isomers differ in their chemical and spectroscopic behaviors. Thus, on trying to hydrolyze the ester group of the methyl quinolinium-2-ethynyl-benzoate into the corresponding acid by subsequent treatment with sodium hydroxide in methanol and aqueous hydrochloric acid at pH 3, the acetal methyl 1,1-dimethoxy-2-(quinolinium-ylidene)ethyl]benzoate and the corresponding β-enamino carbonyl compound were formed, respectively. The corresponding acids of the 2- and 4-substituted quinolinium-ethynyl-benzoates were obtained by a modified procedure. On deprotonation, the resulting cross-conjugated quinolinium-3-ethynyl-benzoate betaine proved to be stable, whereas the corresponding pseudo-cross-conjugated quinolinium-2- and -4-ethynyl-benzoate betaines decomposed. Frontier orbital profiles were calculated, and IR and Raman spectra of the starting materials were measured and calculated to analyze the differences of CCMBs and PCCMBs of mesomeric betaines possessing triple bonds. A higher contribution of the cumulenoid resonance forms to the overall structure of the PCCMBs was determined.

Full text of DOI:10.1515/znb-2018-0020

Z. Naturforsch. 2018; aop
SCvhiateosmlaviBsattsrytys, FaranncdiscosJp. Reamcírterzo, Jusacn Coapsaydo,oJafn Cc.rNoamsyssl-ocanodnAnjduregasaStchemdidt*
and pseudo-cross-conjugated quinolinium-
ethynyl-benzoate mesomeric betaines
https://doi.org/10.1515/znb-2018-0020
and IR and Raman spectra of the starting materials were
measured and calculated to analyze the differences of
CCMBs and PCCMBs of mesomeric betaines possessing
triple bonds. A higher contribution of the cumulenoid res-
onance forms to the overall structure of the PCCMBs was
determined.
Received January 22, 2018; accepted February 19, 2018
Abstract: The three isomers 1-methylquinolinium-2-, 3-,
and 4-ethynyl(phenyl-4-carboxylates) belong to two dis-
tinct types of heterocyclic mesomeric betaines. The qui-
nolinium substituted in position 3 is a cross-conjugated
mesomeric betaine (CCMB), whereas the quinolinium Keywords: acetylenes; mesomeric betaines; N-heterocy-
derivatives substituted in positions 2 and 4 are members of clic carbenes; quinolinium-carboxylates.
the class of pseudo-cross-conjugated mesomeric betaines
(PCCMBs). While the charges are strictly separated within
the common π-electron system of the CCMB according to
the canonical formulae, the charges are effectively but
1 Introduction
not exclusively delocalized in the PCCMBs because cumu-
The chemistry of mesomeric betaines, such as their ability
lenoid resonance forms including electron sextet struc-
to undergo 1,3- or 1,4-dipolar cycloadditions [1] or to form
tures without external octet stabilization can be formed
N-heterocyclic carbenes (NHCs) [2–4], is governed by their
in accordance with the definition of PCCMBs. As a con-
type of conjugation. Recently, based on a matrix-connec-
sequence, despite being closely related structures, the
tivity analysis, Ramsden et al. identified five types of con-
three isomers differ in their chemical and spectroscopic
jugation present in mesomeric betaines, which led to the
behaviors. Thus, on trying to hydrolyze the ester group of
definition of five main classes and nine subclasses [4–7].
the methyl quinolinium-2-ethynyl-benzoate into the cor-
Generally, isomers allow studies on the chemical and spec-
responding acid by subsequent treatment with sodium
troscopic consequences of different types of conjugation
hydroxide in methanol and aqueous hydrochloric acid
present in structurally closely related compounds. As an
at pH 3, the acetal methyl 1,1-dimethoxy-2-(quinolinium-
example, 1-methylquinolinium-2-carboxylate 1 (Scheme 1)
ylidene)ethyl]benzoate and the corresponding β-enamino
[8], which is the defensive betaine of Photuris versicolor
carbonyl compound were formed, respectively. The cor-
fireflies [9–11], belongs to the class of pseudo-cross-con-
responding acids of the 2- and 4-substituted quinolin-
jugated heterocyclic mesomeric betaines (PCCMBs); the
ium-ethynyl-benzoates were obtained by a modified
same is true for the 1-methylquinolinium-4-carboxylate
procedure. On deprotonation, the resulting cross-conju-
3 [8]. By contrast, 1-methylquinolinium-3-carboxylate 2
gated quinolinium-3-ethynyl-benzoate betaine proved to
(benzotrigonelline, 3QB) [12–15] is a member of the class
be stable, whereas the corresponding pseudo-cross-con-
of cross-conjugated mesomeric betaines (CCMBs). A con-
jugated quinolinium-2- and -4-ethynyl-benzoate betaines
nectivity analysis shows the differences between these
decomposed. Frontier orbital profiles were calculated,
types of conjugation. As shown in representation III, the
delocalization of the negative and positive charges of the
CCMB 2 is restricted to odd and alternating hydrocarbon
*Corresponding author: Andreas Schmidt, Institute of Organic
fragments, respectively. Both partial structures are linked
via inactive, unstarred (o) positions through union bonds.
By contrast, the representations I and V of the PCCMBs
show starred positions (*) from which bonds to the nega-
tively charged partial structures are formed. Concerning
the anionic fragment, the inactive positions correspond to
nodal positions of the highest occupied molecular orbitals
(HOMOs). In CCMBs such as 2, this connectivity causes a
Chemistry, Clausthal University of Technology, Leibnizstrasse 6,
D-38678 Clausthal-Zellerfeld, Germany,
E-mail: schmidt@ioc.tu-clausthal.de
Sviatoslav Batsyts and Jan C. Namyslo: Institute of Organic
Chemistry, Clausthal University of Technology, Leibnizstrasse 6,
D-38678 Clausthal-Zellerfeld, Germany
Francisco J. Ramírez and Juan Casado: Department of Physical
Chemistry, Faculty of Sciences, University of Málaga, E-29071
Málaga, Spain
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ꢀꢀꢀꢁ
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ꢀS. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBs
*
*
o
O
O
o
o
O
C O
C
C
O
O
*
*
*
N
N
N
O
o
C
Me
O
O
Me
Me
O
O
1
I
II
N
*
N
N
N
R
C
O
o
*
*
R
o
R
R
o
*
o
VII
VIII
*
*
N
*
N
N
o
Me
Me
Me
Scheme 2:ꢀFormal replacement of carboxylate toward acetylenide
moieties.
IV
2
III
O
C
O
O
O
o
*
*
o
o
o
acetylenides are formal ethenediylidene (diatomic carbon,
C2) adducts of quinolin-2-, 3-, and 4-ylidene, respectively.
In continuation of our interest in mesomeric betaines
[41], NHCs [42, 43], and triple bonds in mesomeric
betaines [34, 36, 37], we report here the syntheses, charac-
terization, and vibrational spectroscopic investigations of
4-[(1-methylquinolinium-2-, 3- and 4-yl)ethynyl]benzoates
to elucidate the role of conjugation on their chemical and
spectroscopic properties.
*
*
N
*
N
N
o
Me
Me
Me
VI
3
V
Scheme 1:ꢀThree isomers of 1-methylquinolinium-carboxylates
belonging to two distinct classes of compounds, i.e. pseudo-cross-
conjugated heterocyclic mesomeric betaines (PCCMBs) and cross-
conjugated heterocyclic mesomeric betaines (CCMBs).
π-electronic charge separation in the ground state as sym-
bolized by the dashed line [1–3, 16, 17]. The distinct types
of conjugation translate into chemical properties in such 2 Results and discussion
a way that PCCMBs are versatile precursors of normal
classical NHCs (II, VI) which they form on the extrusion The target molecules 9a–c were prepared in four
of heterocumulenes such as carbon dioxide. Numerous steps including two Sonogashira–Hagihara couplings
examples of thermal decarboxylation of the PCCMBs (Scheme 3). First, we prepared methyl 4-ethynylbenzoate
pyridinium-2-carboxylates [18–22], quinolinium-2-carbox- 6 following the literature [44–46] starting from 4 via 5 [44,
ylates [20, 23], and other ring systems [24–30] have been
reported in the literature. The observation that 2-imino-
carboxylate partial structures decarboxylate can be traced
MEBYNOL,
Pd(PPh3)2Cl2
CuI, NEt3
OH
Me
Me
back to at least the last third of the 19th century [31–33]
and thus seem to be at the dawn of the history of NHCs
[2] long before the term “pseudo-cross-conjugation” was
defined [1]. By contrast, CCMBs are formally composed
of remote, nonclassical NHCs IV, which form under very
vigorous reaction conditions, if at all [2, 3]. Thus, from a
synthetic viewpoint – in contrast to PCCMBs – CCMBs are
not suitable precursors of NHCs.
The insertion of triple bonds into the π-conjugated
system of mesomeric betaines of pyridine derivatives
offers additional perspectives to the study of the types of
conjugation and their consequences for synthetic chemis-
try [34, 35], carbene chemistry [36, 37], or materials chem-
istry [38–40]. Thus, formal replacement of the carboxylate
group by acetylenic groups gives quinolinium-acety-
lenides, from which mesomeric structures of vinylidene
carbenes can be drawn (Scheme 2). While – as mentioned
above – quinolinium-carboxylates can be regarded as
MeOOC
Br
MeOOC
4
5 (90%)
KOH, K3PO4,
toluene
COOMe
Pd(PPh3)2Cl2,
CuI, NEt3
MeOOC
N
X
6 (92%)
N
8a: 2-yl (66%)
8b: 4-yl (78%)
8c: 3-yl (85%)
7a: X = Cl
7b: X = Br
7c: X = Br
Me2SO4,
toluene
COOMe
9a: 2-yl (98%)
9b: 4-yl (97%)
9c: 3-yl (91%)
MeOSO3
N
Me
Scheme 3:ꢀSynthesis of 2-, 3-, and 4-[4-(methoxycarbonyl)phenyl)
carbon dioxide adducts of NHCs, the corresponding ethynyl]-1-methylquinolinium salts.
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S. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBsꢂ
47, 48] in very good yield. Next we prepared methyl 4-(qui- spectroscopy, while the exocyclic enamine carbon atom
nolin-2-ylethynyl) benzoate 8a by Sonogashira–Hagihara of the β-enaminocarbonyl chromophore resonated at
coupling of methyl 4-ethynylbenzoate 6 with 2-chloroqui- δꢀ=ꢀ115.5 ppm. No traces of the tautomers 13 and 14 were
noline in the presence of 10% catalyst in 66% yield. Fol- seen in the spectra. The carboxylic proton is not detected
1
lowing these conditions, 8b and 8c were prepared in 78% by H NMR spectroscopy under these conditions, but the
and 85% yields starting from 4- and 3-bromoquinolines IR spectra of 12 show an absorption of the C=O group at
−1
7b,c. Methylations of 8a–c were carried out using dime- 1638 cm , whereas the corresponding betaines absorb in
−1
thyl sulfate in toluene, and the salts 9a–c were formed in the region 1570–1580 cm [34]. On addition of an acid to
almost quantitative to very good yields (98%, 97%, and the solution of 12 in [D6]DMSO, all resonance frequencies
91%, respectively).
shifted downfield, presumably due to the protonation of
As the acid-catalyzed hydrolyses failed, the saponi- the carbonyl oxygen atom.
fication of 9a–c was performed under basic conditions.
The triple bond remained intact if the saponification
While the reaction of the potential cross-conjugated of 8a,b was performed before carrying out the N-meth-
system 9c with excess NaOH in a methanol–water mixture ylation (Scheme 5). Thus, the N-methylation of the acids
followed by acidification with HCl gave the acid 10c in 15a,b is accomplished in almost quantitative yields to give
very good yield, the application of the reaction condi- the salts 10a,b as water-soluble solids.
tions to the potential pseudo-cross-conjugated system
Deprotonation of the 3-substituted quinolinium salt
9a resulted in a transformation of the triple bond and the 10c to give the cross-conjugated mesomeric betaine 16c
formation of the compounds 11 and 12 (Scheme 4). The was successful when triethylamine in methanol was used
former compound precipitated before the acidification of as base [34]. The 2- and 4-substituted derivatives 10a,b
the reaction mixture in 26% yield and could be filtered off. decomposed on treatment with a series of bases which
The N-methyl signal of acetal 11, which is soluble in we applied as part of a base screening (NEt3 in MeOH;
diethyl ether, shifted from δꢀ=ꢀ4.79 ppm (9a) in [D6]DMSO NEt3 in [D6]DMSO; proton sponge in [D6]DMSO, LiHMDS
to δꢀ=ꢀ3.20 ppm in CDCl3, indicating the loss of a positive in [D3]MeCN). Consequently, the PCCMBs 16a,b could not
1
charge. The H NMR shifts of the two equivalent methoxy be isolated. The marked difference between the isomers
groups and of the ester group are δꢀ=ꢀ3.12 ppm and 16a,b and 16c is that the former PCCMBs can be repre-
1
δꢀ=ꢀ3.89 ppm, respectively. The H NMR spectrum of 12 – sented by the cumulenoid canonical formula (Scheme 6).
which possesses the β-enaminocarbonyl chromophore – A precondition and characteristic feature is the formu-
shows a signal of the methyl group at δꢀ=ꢀ3.74 ppm, which lation of mesomeric forms that possess electron sextet
is an intermediate value between those of the salt 9a and structures without external octet stabilization, as shown
the acetal 11. Characteristically, the signal of the carbonyl [1–3]. By contrast, no canonical structures possessing
carbon atom was detected at δꢀ=ꢀ184.6 ppm in 13C NMR cumuleoid groups can be formulated for the CCMB 16c.
1. NaOH (10 eq.),
MeOH/H2O
2. HCl (pH = 3)
COOH
X
O
O
9a, c
OH
OMe
1. NaOH, MeOH/H2O
2. HCl (pH=1)
N
NaOH (10 eq.),
MeOH/H2O
Me
N
N
10c (X = Cl, 92%)
8a: 2-yl
8b: 4-yl
15a: 97%
15b: 88%
OMe
O
HCl (pH = 3)
COOMe
Me2SO4,
toluene
N
N
MeO
Me
Me
O
O
O
X
COOH
12 (70%)
11
OH
bases
O
OH
N
N
N
N
Me
Me
Me
Me
COO
COO
10a (X = MeSO4, 83%)
10b (X = MeSO4, 86%)
16a,b
13
14
Scheme 4:ꢀResults of the hydrolyses of the esters 9a, c.
Scheme 5:ꢀSynthesis of the acids 10a,b.
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ꢀꢀꢀꢁ
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ꢀS. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBs
etc.
N
N
Me
Me
O
O
O
O
16a
O
O
O
O
O
O
O
O
etc.
N
N
N
N
Me
CH3
O
CH3
O
CH3
O
Me
Me
Me
O
O
O
16b
128.7
132.2
131.5
O
O
133.4
132.1
133.1
105.2
86.0
106.5
84.3
93.5
85.9
CH3
N
N
Me
N
N
CH3
16c
CH3
Scheme 6:ꢀTitle betaines and some canonical formulae.
sites for positive charges
Fig. 1:ꢀLUMO profiles of salts 9a–c (above) and charge distribution
according to the mesomeric structures. Some characteristic 13C NMR
signals are given in red.
We performed spectroscopic examinations and calcu-
lations to gain insight into the bond situation of the start-
ing materials and of the target betaines. The triple bonds
of the esters 8a–c do not absorb light on IR irradiation.
The calculated HOMO–LUMO topologies are similar in the contrast to the neutral compounds 8a–c, the triple bonds
−1
three isomers 8a–c. Both orbitals are widely delocalized of the salts 9a–c absorb at 2206, 2209, and 2227 cm ,
throughout the molecules. The bandgap was calculated respectively. Moreover, the triple bond of the 3-substi-
to be 3.8–3.9 eV. On methylation of 8a–c to the quinolin- tuted isomer causes an absorption peak of small intensity,
ium salts 9a–c, the HOMO–LUMO gap changed to 3.1–3.2 whereas the other isomers give peaks of medium intensity
eV in the 2-substituted (9a) and 4-substituted isomer (Fig. 2).
(9b) and to 2.7 eV in the 3-substituted isomer (9c). The
Experimental and theoretical Raman spectra of
orbital topology sets the 3-substituted isomer apart from the cations 9a–c are included in Fig. 3. The 6-311g(d,p)
the other (Fig. 1). While the HOMO is widely delocalized basis set, within the frame of the density functional
throughout the molecule and comparable to that of the theory (DFT) at the b3lyp level, was used to calculate
other isomers, the LUMO atomic orbital coefficients reflect the Raman spectra, which are successfully compared
the charge distribution of the positive charge according to with the experimental ones. The most intense band in
the canonical formula and also translate into characteris- all the spectra is assigned to the stretching vibration of
tic 13C NMR chemical shifts. Thus, as a consequence of the the C≡C bond. The experimental wavenumbers provide
substitution via an unstarred position of the quinolinium us useful information about the conjugation length
(c.f. Scheme 1), the LUMO of 9c is essentially located in the along the wire connecting the two aromatic moieties
quinolinium ring, whereas it is also located in the phenyl in these adducts. The ν(C≡C) vibration is shifted from
−1
ring by conjugation via the triple bond in the pseudo- 2229 cm in the potential cross-conjugated isomer 9c
−1
cross-conjugated isomers 9a,b.
to 2206 and 2212 cm in the potential pseudo-cross-
The difference between the 2-/4-substituted and the conjugated isomers 9a and 9b, respectively. The pos-
3-substituted isomer is also visible in the IR spectra: in sibility of the cumulenoid canonical formula in 9a and
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S. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBsꢂ
Fig. 2:ꢀExperimental IR spectra of the cations 9a (2-yl, red line), 9b (4-yl, green line), and 9c (3-yl, black line)
9b withdraws electronic density from the triple bond to
the adjacent single bonds. In consequence, this bond
becomes weaker than in 9c, for which no cumulenoid
forms can be proposed. This is fully compatible with the
molecular orbital (MO) topologies. The HOMOs of the
three isomers are clearly bonding in the C≡C triple bond.
However, the LUMOs of 9a and 9b are antibonding,
while in 9c this orbital is nonbonding. The calculated
wavenumbers also support the spectral results. The
−1
ν(C≡C) mode was predicted at 2269, 2265, and 2295 cm
for 9a, 9b, and 9c, respectively. The shift between 9c
−1
(3-yl) and 9a (2-yl), 26 cm , is close to the experimen-
−1
tal value of 23 cm . However, a greater deviation is pre-
−1
dicted when comparing the calculated (30 cm ) and the
−1
experimental (17 cm ) shift in 9b (4-yl). In our opinion,
this is caused by the intermolecular interactions exist-
ing in solid samples, which are absent in our theoreti-
cal model. The smaller downshift measured in 9b would
indicate a more intense π-stacking interaction than in
the other two isomers, which decreased the contribu-
tion of the two aromatic moieties to the electronic con-
jugation along the wire. Thus, the cumulenoid form
would be less favored than in the pseudo-cross-conju-
gated isomer 9a. In order to provide a more quantita-
tive description of the contribution of the cumulenoid
canonical formula in these adducts, we used the same
theoretical approach to calculate the ν(C≡C) wave-
number of H3C–C≡C–CH3 and H2C=C=C=CH2 as models
of pure triple bond and cumulene systems. They were
−1
predicted at 2365 and 2205 cm , respectively. The cal-
−1
culated shift, 160 cm , was then taken as a measure of
Fig. 3:ꢀExperimental (red lines) and b3lyp/6-311g(d,p) (blue lines)
Raman spectra of cations 9a (2-yl, bottom panel), 9b (4-yl, upper
panel), and 9c (3-yl, middle panel)
the difference between the two pure forms. By compar-
ing it with the experimental shifts, the contribution of
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6ꢀ ꢀS. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBs
the cumulenoid formula in 9a and 9b is quantified as
14–15% and 10–11%, respectively.
a
b
The theoretical spectra allow us to compare the
bending modes associated with the triple bond. This
requires an unambiguous assignment of the involved
vibrations, which is easily accessible from the calculated
normal modes. In 9c (3-yl), the in-plane bending vibra-
Me
−1
tion, δ(C≡C), was predicted at 603 cm , whereas the out-
−1
of-plane mode was calculated at 557 cm . Both vibrations
16c
involve the whole wire connecting the two aromatic moie-
ties, so that they have to be sensitive to the conjugation.
For bending vibrations, a wavenumber upshift should be
expected with increasing conjugation. The wavenumbers
sites for positive charges
sites for negative charges
sites for positive and negative
charges in the canonical forms
Fig. 5:ꢀCharge distribution according to the mesomeric structures
and HOMO (a) and LUMO (b) of 16c.
−1
calculated for these modes are 621 and 567 cm for 9a
−1
(2-yl) and 613 and 563 cm for 9b (4-yl). These data are in
agreement with the ν(C≡C) wavenumber shifts and with
the observed difference between the two pseudo-cross- with findings concerning other CCMBs [1–3] (Fig. 5). The
conjugated isomers.
LUMO of 16c is located in the quinolinium ring, similar to
According to the calculation, the LUMO of the unsta- its precursor 9c.
ble PCCMBs 16a,b is located in the entire π-electron
system and the HOMO possesses its largest coefficients
in the carboxylate group, in the phenyl ring, in the triple
3 Conclusions
bond, as well as in the quinolinium ring (Fig. 4). In con-
trast, the CCMB 16c possesses a HOMO that is essentially
located in the carboxylate group. The connection via a
nodal (unstarred) position (c.f. Scheme 1) causes an inter-
ruption of the π-conjugation here, and this is in agreement
The classification system and the connectivity analy-
sis of the three isomers 1-methylquinolinium-2-, 3-, and
4-ethynyl(phenyl-4-carboxylate) lead to the conclusion
that the 2- and 4-isomers belong to the class of PCCMB,
whereas the 3-isomer is a CCMB. The distinct types of
conjugation translate into different spectroscopic and
chemical behaviors. Marked differences of the frontier
orbital profiles were calculated. Vibrational spectroscopy
proved that the pseudo-cross-conjugated systems display
a higher degree of contribution of cumulenoid resonance
forms to the overall electronic structure.
a
b
Me
16a
4 Experimental section
The reactions were carried out under an inert atmosphere
in oven-dried glassware. Nuclear magnetic resonance
(NMR) spectra were measured with a Bruker Avance
1
III 600 MHz NMR spectrometer. H NMR spectra were
recorded at 600 MHz and 13C NMR spectra at 150 MHz,
with the solvent peak used as the internal reference. Mul-
tiplicities are described by using the following abbrevia-
tions: sꢀ=ꢀsinglet, dꢀ=ꢀdoublet, tꢀ=ꢀtriplet, qꢀ=ꢀquartet, and
mꢀ=ꢀmultiplet, and the signal orientations in DEPT (dis-
tortionless enhancement by polarization transfer) experi-
ments were described as follows: oꢀ=ꢀno signal; +ꢀ=ꢀup
(CH, CH3). The numberings such as 2-H, 2′-H, etc. refer
Me
16b
sites for positive charges
sites for negative charges
sites for positive and negative
charges in the canonical forms
Fig. 4:ꢀCharge distribution according to the mesomeric structures
and HOMOs (a) and LUMOs (b) of 16b.
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S. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBsꢂ
to the quinolinium and benzoic acid rings, respectively. 4.1.2 Methyl 4-(quinolin-4-ylethynyl)benzoate (8b)
The attenuated total reflection infrared (ATR-IR) spectra
1
were obtained on a Bruker Alpha spectrometer in the Yellow solid (447.7 mg, 78%). M. p. 120°C. H NMR
−1
range 400–4000 cm . Mass spectra were measured with (600.35 MHz, CDCl3, 25°C): δꢀ=ꢀ8.93 (d, Jꢀ=ꢀ4.2 Hz, 1H, 2-H),
an Agilent LCMSD series HP 1100 with APIES (ESIMS). 8.35 (d, Jꢀ=ꢀ8.4 Hz, 1H, 8-H), 8.18 (d, Jꢀ=ꢀ8.4 Hz, 1H, 5-H),
High-resolution mass spectra (HRMS) were obtained 8.11–8.09 (m, 2H, 3′-H, 5′-H), 7.79 (ddd, Jꢀ=ꢀ1.4, 6.9, 8.3, 1H,
with a Bruker Impact II, a Bruker Daltonik Tesla-Fourier 6-H), 7.74–7.72 (m, 2H, 2′-H, 6′-H), 7.66 (ddd, Jꢀ=ꢀ1.4, 6.9, 8.3,
transform-ion cyclotron resonance mass spectrometer, or 1H, 7-H), 7.61 (d, Jꢀ=ꢀ4.2 Hz, 1H, 3-H), 3.96 (s, 3H, COOCH3)
a Waters Micromass LCT with direct inlet. Melting points ppm. 13C NMR (150.96 MHz, CDCl3, 25°C): δꢀ=ꢀ166.5 (o,
were determined in a Büchi apparatus, and are uncor- COO), 149.6 (+, C-2), 147.9 (o, C-8a), 132.1 (+, C-2′, C-6′), 130.7
rected. Yields are not optimized.
(o, C-4′), 130.4 (+, C-7), 129.9 (+, C-8), 129.6 (o, C-4), 127.8
(o, C-4a), 127.7 (+, C-6), 126.9 (o, C-1′), 126.0 (+, C-5), 123.9
(+, C-3), 97.1 (o, C-Ph), 87.8 (o, C-quinoline), 52.3 (+, CH3)
ppm. IR (ATR): νꢀ=ꢀ3055, 2954, 2846, 1947, 1721, 1602, 1577,
1499, 1435, 1404, 1307, 1273, 1194, 1172, 1108, 1015, 959, 870,
4.1 General procedure for the preparation
of the methyl 4-(quinolinylethynyl)
benzoates (8a–8c).
−1
854, 763, 691, 594, 525, 499, 458, 443 cm . MS (ESI): m/z
+
(%)ꢀ=ꢀ288.1 (100) [Mꢀ+ꢀH] . HRMS [(+)-ESI]: m/zꢀ=ꢀ310.0837
+
A mixture of the corresponding 2-chloroquinoline (7a: (calcd. 310.0839 for C19H13NNaO2, [Mꢀ+ꢀNa] ).
327.2 mg, 2 mmol, 100 mol%; 7b: 416.1 mg, 2 mmol,
100 mol%; 7c: 416.1 mg, 2 mmol, 100 mol%), Pd(PPh3)2Cl2
(14 mg, 0.02 mmol, 1 mol%), and CuI (7.6 mg, 0.04 mmol, 4.1.3 Methyl 4-(quinolin-3-ylethynyl)benzoate (8c)
2 mol%) was suspended in dry triethylamine (7 mL)
1
with stirring. Then, methyl 4-ethynylbenzoate 5 (352 mg, Brownish solid (487.9 mg, 85%). M. p. 139°C. H NMR
2.2 mmol, 110 mol%) in dry triethylamine was added drop- (600.35 MHz, CDCl3, 25°C): δꢀ=ꢀ9.00 (d, Jꢀ=ꢀ2.2 Hz, 1H, 2-H),
wise at ambient temperature. The resulting solution was 8.33 (d, Jꢀ=ꢀ2.2 Hz, 1H, 4-H), 8.11 (d, Jꢀ=ꢀ8.6 Hz, 1H, 8-H), 8.06
then stirred at reflux temperature until complete conver- (ddd, Jꢀ=ꢀ1.4, 2.0, 8.3 Hz, 2H, 3′-H, 5′-H), 7.81 (d, Jꢀ=ꢀ8.6 Hz,
sion, as monitored by thin layer chromatography (TLC). 1H, 5-H), 7.74 (ddd, Jꢀ=ꢀ1.5, 6.8, 8.6 Hz, 1H, 7-H), 7.65 (ddd,
The mixture was then allowed to cool to room temperature Jꢀ=ꢀ1.4, 2.0, 8.3 Hz, 2H, 2′-H, 4′-H), 7.58 (ddd, Jꢀ=ꢀ1.5, 6.8,
and the trimethylamine was removed in vacuo. The result- 8.6 Hz, 1H, 6-H), 3.94 (s, 3H, COOCH3) ppm. 13C NMR
ing residue was finally purified by column chromatogra- (150.96 MHz, CDCl3, 25°C): δꢀ=ꢀ166.4 (o, COO), 152.0 (+,
phy (petroleum ether–ethyl acetate).
C-2), 147.0 (o, C-8a), 138.7 (+, C-4), 131.7 (+, C-2′, C-4′), 130.4
(+, C-8), 130.0 (o, C-4′), 129.7 (+, C-3′, C-5′), 129.5 (+, C-7),
127.7 (+, C-5), 127.5 (+, C-6), 127.3 (o, C-4a), 127.2 (o, C-1′),
116.9 (o, C-3), 91.8 (o, C-quinoline), 89.5 (o, C-Ph), 52.3 (+,
4.1.1 Methyl 4-(quinolin-2-ylethynyl)benzoate (8a)
CH3) ppm. IR (ATR): 3017, 1716, 1276, 1098, 953, 905, 855,
1
−1
Brownish solid (378.8 mg, 66%). M. p. 132°C. H NMR 767, 742, 697, 480 cm . MS (ESI): m/z (%)ꢀ=ꢀ287.3 (100)
+
(600.35 MHz, CDCl3, 25°C): δꢀ=ꢀ8.17 (d, Jꢀ=ꢀ8.5 Hz, 1H, 4-H), [M] . HRMS [(+)-ESI]: m/zꢀ=ꢀ288.1022 (calcd. 288.1025 for
+
8.15 (d, Jꢀ=ꢀ8.7 Hz, 1H, 8-H), 8.06–8.04 (m, 2H, 3′-H, 5′-H), C19H14NO2, [Mꢀ+ꢀH] ).
7.82 (dd, Jꢀ=ꢀ1.2, 8.1 Hz, 1H, 5-H), 7.75 (ddd, Jꢀ=ꢀ1.5, 6.9, 8.4 Hz,
1H, 7-H), 7.73–7.71 (m, 2H, 2′-H, 6′-H), 7.62 (d, Jꢀ=ꢀ8.5 Hz,
1H, 3-H), 7.57 (ddd, Jꢀ=ꢀ1.5, 6.9, 8.4 Hz, 1H, 6-H), 3.93 (s,
4.2 General procedure for the preparation
of the methyl benzoate-substituted
quinolinium salts (9a–9c) and the
corresponding carboxylic acids
(10a–10b)
3H, COOCH3) ppm. 13C NMR (150.96 MHz, CDCl3, 25°C):
δꢀ=ꢀ166.6 (o, COO), 148.2 (o, C-8a), 143.1 (o, C-2), 136.6 (+,
C-4), 132.3 (+, C-2′, C-6′), 130.6 (o, C-4′), 130.5 (+, C-7), 129.7
(+, C-3′, C-5′), 129.4 (+, C-8), 127.7 (+, C-5), 127.6 (+, C-6), 127.4
(o, C-4a), 126.8 (o, C-1′), 124.4 (+, C-3), 91.8 (o, C-quinoline),
89.2 (o, C-Ph), 52.4 (+, CH3) ppm. IR (ATR): νꢀ=ꢀ2946, 2847,
1943, 1712, 1591, 1496, 1436, 1306, 1275, 1175, 1106, 1012, Methyl 4-(quinolin-2-ylethynyl)benzoates (8a: 287 mg,
−1
859, 829, 788, 767, 748, 697, 625, 504, 479 cm . MS (ESI): 1 mmol, 100 mol%; 8b: 287 mg, 1 mmol, 100 mol%;
+
m/z (%)ꢀ=ꢀ293.1 (100) [M] . HRMS [(+)-ESI]: m/zꢀ=ꢀ288.1028 8c: 287 mg, 1 mmol, 100 mol%; 15a: 273 mg, 1 mmol,
+
(calcd. 288.1019 for C19H14NO2, [Mꢀ+ꢀH] ).
100 mol%; 15b: 273 mg, 1 mmol, 100 mol%) were
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8ꢀ ꢀS. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBs
+
dissolved in anhydrous toluene (6 mL) containing one (100) [M] . HRMS [(+)-ESI]: m/zꢀ=ꢀ302.1192 (calcd. 302.1170
+
drop of nitrobenzene, respectively. Then dimethyl sulfate for C20H16NO2, [M] ).
(0.24 mL, 2.5 mmol, 250 mol%) was added with stirring.
The resulting mixtures were stirred at reflux temperature
over a period of 3 h. Thereafter, the reaction mixtures were 4.2.3 3-((4-(Methoxycarbonyl)phenyl)ethynyl)-1-
cooled and the crude products were filtered off, washed
with ethyl acetate (3ꢀ×ꢀ10 mL), and dried.
methylquinolinium methylsulfate (9c).
Brown solid (375.8 mg, 91%). M.p. 220°C. 1H NMR
(600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ9.91 (d, Jꢀ=ꢀ1.2 Hz, 1H,
2-H), 9.54 (s, 1H, 4-H), 8.55 (d, Jꢀ=ꢀ9.0 Hz, 1H, 8-H), 8.46
(d, Jꢀ=ꢀ9.0 Hz, 1H, 5-H), 8.33 (ddd, Jꢀ=ꢀ1.3, 7.0, 9.0 Hz, 1H,
6-H), 8.14–8.07 (m, 3H, 7-H, 2′-H, 6′-H), 7.83 (ddd, Jꢀ=ꢀ1.5,
4.2.1 2-[(4-(Methoxycarbonyl)phenyl)ethynyl]-1-
methylquinolinium methylsulfate (9a)
Gray solid (404.7 mg, 98%). M.p. 185°C (decomp.). 1H NMR 1.9, 8.2 Hz, 2H, 3′-H, 5′-H), 4.66 (s, 3H, NCH3), 3.90 (s, 3H,
(600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ9.27 (d, Jꢀ=ꢀ8.3 Hz, 1H, COOCH3), 3.37 (s, 3H, CH3SO4) ppm. 13C NMR (150.96 MHz,
4-H), 8.62 (d, Jꢀ=ꢀ9.0 Hz, 1H, 8-H), 8.48 (d, Jꢀ=ꢀ8.1 Hz, 1H, [D6]DMSO, 25°C): δꢀ=ꢀ165.4 (o, COO), 152.2 (+, C-2), 148.3
3-H), 8.46 (d, Jꢀ=ꢀ6.2 Hz, 1H, 5-H), 8.32 (ddd, Jꢀ=ꢀ1.6, 7.2, (+, C-4), 137.5 (o, C-8a), 136.3 (+, C-7), 132.1 (+, C-2′, C-6′),
8.8 Hz, 1H, 7-H), 8.15 (d, Jꢀ=ꢀ8.3 Hz, 2H, 3′-H, 5′-H), 8.10 (d, 130.7 (+, C-6), 130.5 (o, C-4a), 130.4 (+, C-5), 129.7 (+, C-3′,
Jꢀ=ꢀ8.3 Hz, 2H, 2′-H, 6′-H) 8.07 (t, Jꢀ=ꢀ7.6 Hz, 1H, 6-H), 4.79 C-5′), 128.7 (o, C-4′), 125.2 (C-1′), 119.3 (+, C-8), 116.2 (o, C-3),
(s, 3H, NCH3), 3.91 (s, 3H, COOCH3), 3.37 (s, 3H, CH3SO4) 93.5 (o, C-Ph), 85.9 (o, C-quinoline), 52.8 (+, CH3SO4), 52.5
13
ppm. C NMR (150.96 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ165.3 (o, (+, COOCH3), 45.5 (+, NCH3) ppm. IR (ATR): νꢀ=ꢀ1721, 1278,
COO), 145.6 (+, C-4), 140.3 (o, C-2), 139.4 (o, C-8a), 136.2 (+, 1240, 1215, 1170, 1097, 1057, 1005, 866, 766, 729, 696, 607,
−1
+
C-7), 133.4 (+, C-2′, C-6′), 132.2 (o, C-4′), 130.3 (+, C-5), 129.7 574 cm . MS (ESI): m/z (%)ꢀ=ꢀ302.1 (100) [M] . HRMS [(+)-
+
(+, C-6, C-3′, C-5′), 128.6 (o, C-4a), 126.3 (+, C-3), 123.3 (o, ESI]: m/zꢀ=ꢀ302.1183 (calcd. 302.1181 for C20H16NO2, [M] ).
C-1′), 119.6 (+, C-8), 106.5 (o, C-Ph), 84.3 (o, C-quinoline),
52.7 (+, CH3SO4), 52.6 (+, OCH3), 42.9 (+, NCH3) ppm. IR
4.2.4 2-[(4-Carboxyphenyl)ethynyl]-1-
(ATR): νꢀ=ꢀ3090, 3066, 2950, 2206, 2066, 1976, 1714, 1594,
methylquinolinium methylsulfate (10a)
1576, 1520, 1435, 1354, 1221, 1106, 1058, 1004, 831, 770, 732,
−1
694, 609, 577, 498, 465, 428 cm . MS (ESI): m/z (%)ꢀ=ꢀ302.1
Yellow solid (331.5 mg, 83%). M.p. 177°C (decomp.). 1H NMR
(600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ9.26 (d, Jꢀ=ꢀ8.7 Hz, 1H,
+
(100) [M] . HRMS [(+)-ESI]: m/zꢀ=ꢀ302.1170 (calcd. 302.1170
+
for C20H16NO2, [M] ).
4-H), 8.61 (d, Jꢀ=ꢀ8.9 Hz, 1H, 8-H), 8.50 (d, Jꢀ=ꢀ8.3 Hz, 1H, 5-H),
8.47 (d, Jꢀ=ꢀ8.7 Hz, 1H, 3-H), 8.32 (ddd, Jꢀ=ꢀ1.6, 7.1, 8.8 Hz, 1H,
7-H), 8.13 (d, Jꢀ=ꢀ8.7 Hz, 2H, 3′-H, 5′-H), 8.07 (d, Jꢀ=ꢀ8.5 Hz, 2H,
4.2.2 4-[(4-{Methoxycarbonyl}phenyl)ethynyl]-1-
2′-H, 6′-H) 8.07 (t, Jꢀ=ꢀ7.6 Hz, 1H, 6-H), 4.79 (s, 3H, NCH3), 3.37
methylquinolinium methylsulfate (9b)
(s, 3H, CH3SO4) ppm. 13C NMR (150.96 MHz, [D6]DMSO, 25°C):
δꢀ=ꢀ166.3 (o, COO), 145.6 (+, C-4), 140.4 (o, C-2), 139.4 (o, C-8a),
Yellow solid (400.6 mg, 97%). Mp. 199°C. 1H NMR
136.2 (+, C-7), 133.5 (o, C-4′), 133.3 (+, C-2′, C-6′), 130.4 (+, C-5),
(600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ9.52 (d, Jꢀ=ꢀ6.2 Hz, 1H,
129.7 (+, C-6), 129.6 (+, C-3′, C-5′), 128.6 (o, C-4a), 126.3 (+, C-3),
2-H), 8.78 (d, Jꢀ=ꢀ8.2 Hz, 1H, 5-H), 8.57 (d, Jꢀ=ꢀ8.2 Hz, 1H,
122.8 (o, C-1′), 119.6 (+, C-8), 106.8 (o, C-Ph), 84.1 (o, C-quino-
8-H), 8.41 (d, Jꢀ=ꢀ6.2 Hz, 1H, 3-H), 8.35 (ddd, Jꢀ=ꢀ1.5, 7.1,
line), 52.7 (+, CH3SO4), 42.9 (+, NCH3) ppm. IR (ATR): νꢀ=ꢀ2944,
8.7 Hz, 1H, 7-H), 8.16 (ddd, Jꢀ=ꢀ1.5, 7.1, 8.7 Hz, 1H, 6-H), 8.13–
2220, 1717, 1635, 1609, 1521, 1489, 1407, 1387, 1334, 1171, 1057,
8.11 (m, 2H, 3′-H, 5′-H), 8.06–8.05 (m, 2H, 2′-H, 6′-H), 4.64
−1
994, 866, 842, 746, 689, 659, 612, 575, 471, 427 cm . MS (ESI):
(s, 3H, NCH3) 3.91 (s, 3H, COOCH3), 3.37 (s, 3H, CH3SO4)
+
m/z (%)ꢀ=ꢀ288.1 (100) [M] . HRMS [(+)-ESI] m/zꢀ=ꢀ288.1031
13
ppm. C NMR (150.96 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ165.4 (o,
+
(calcd. 288.1014 for C19H14NO2, [M] ).
COO), 149.5 (+, C-2), 138.4 (o, C-8a), 137.9 (o, C-4), 135.8 (+,
C-7), 133.1 (+, C-2′, C-6′), 130.9 (+, C-6), 129.6 (+, C-3′, C-5′),
128.4 (o, C-4a), 127.9 (+, C-5), 124.6 (+, C-3), 124.4 (o, C-1′), 4.2.5 4-[(4-Carboxyphenyl)ethynyl]-1-methylquinolinium
119.8 (+, C-8), 105.2 (o, C-Ph), 86.0 (o, C-quinoline), 52.8 (+,
CH3SO4), 52.6 (+, COOCH3), 45.5 (+, NCH3) ppm. IR (ATR):
methylsulfate (10b)
1
νꢀ=ꢀ3081, 2943, 2829, 2209, 1943, 1718, 1604, 1527, 1435, 1403, Yellow solid (343.5 mg, 86%). M.p. 195°C (decomp.). H
1275, 1220, 1103, 1059, 1011, 863, 808, 784, 768, 727, 694, NMR (600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ9.51 (d, Jꢀ=ꢀ5.8 Hz,
−1
645, 608, 577, 551, 466, 428 cm . MS (ESI): m/z (%)ꢀ=ꢀ302.1 1H, 2-H), 8.78 (d, Jꢀ=ꢀ8.1 Hz, 1H, 5-H), 8.56 (d, Jꢀ=ꢀ8.8 Hz,
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ꢂ9
S. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBsꢂ
1H, 8-H), 8.40 (d, Jꢀ=ꢀ6.1 Hz, 1H, 3-H), 8.35 (t, Jꢀ=ꢀ7.7 Hz, 4.3.2 4-(Quinolin-4-ylethynyl)benzoic acid (15b)
1H, 7-H), 8.16 (t, Jꢀ=ꢀ7.7 Hz, 1H, 6-H), 8.10 (d, Jꢀ=ꢀ7.9 Hz, 2H,
3′-H, 5′-H), 8.03 (d, Jꢀ=ꢀ8.3 Hz, 2H, 2′-H, 6′-H), 4.63 (s, 3H, Gray solid (240.2 mg, 88%). M.p. 274°C. 1H NMR
NCH3), 3.37 (s, 3H, CH3SO4) ppm. 13C NMR (150.96 MHz, (600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ13.27 (m, 1H, COOH),
[D6]DMSO, 25°C): δꢀ=ꢀ166.5 (o, COO), 149.5 (+, C-2), 138.4 8.97 (d, Jꢀ=ꢀ4.4 Hz, 1H, 2-H), 8.39 (dd, Jꢀ=ꢀ0.8, 8.3 Hz, 1H,
(o, C-8a), 138.0 (o, C-4), 135.8 (+, C-7), 132.9 (o, C-4′), 131.0 5-H), 8.11 (d, Jꢀ=ꢀ8.3 Hz, 1H, 8-H), 8.05–8.04 (m, 2H, 3′-H,
(+, C-6), 129.8 (+,C-3′, C-5′), 128.5 (o, C-4a), 128.0 (+, C-5), 5′-H), 7.90–7.88 (m, 2H, 2′-H, 6′-H), 7.87 (ddd, Jꢀ=ꢀ1.5, 6.8,
124.6 (o, C-1′), 124.0 (+, C-3), 119.9 (+, C-8), 105.6 (o, C-Ph), 8.2 Hz, 1H, 7-H), 7.80 (d, Jꢀ=ꢀ4.4 Hz, 1H, 3-H), 7.78 (ddd,
85.8 (o, C-quinoline), 52.8 (+, CH3SO4), 45.5 (+, NCH3) ppm. Jꢀ=ꢀ1.2, 6.9, 8.1 Hz, 1H, 6-H) ppm. 13C NMR (150.96 MHz,
IR (ATR): νꢀ=ꢀ2207, 1706, 1615, 1604, 1572, 1531, 1403, 1370, [D6]DMSO, 25°C): δꢀ=ꢀ166.6 (o, COO), 150.2 (+, C-2), 147.5
1256, 1195, 1108, 1054, 997, 872, 837, 751, 676, 610, 578, 484, (o, C-8a), 132.1 (+, C-2′, C-6′), 131.5 (o, C-4′), 130.4 (+, C-7),
−1
+
432 cm . MS (ESI): m/z (%)ꢀ=ꢀ288.0 (100) [M] . HRMS [(+)- 129.7 (+,C-8, C-3′, C-5′), 127.7 (+, C-6), 126.6 (o, C-4a), 125.6
+
ESI]: m/zꢀ=ꢀ288.1023 (calcd. 288.1014 for C19H14NO2, [M] ).
(+, C-5), 125.5 (o, C-1′), 124.1 (+, C-3), 97.4 (o, C-Ph), 87.1 (o,
C-quinoline) ppm. IR (ATR): νꢀ=ꢀ2207, 1703, 1606, 1583,
1499, 1417, 1403, 1391, 1307, 1272, 1167, 1016, 893, 858, 813,
−1
4.3 Typical procedure for the preparation of
4-(quinolinethynyl)benzoic acids (15a,b)
and 3-((4-carboxyphenyl)ethynyl)-
757, 685, 608, 573, 537, 505, 471, 438 cm . MS (ESI): m/z
+
(%)ꢀ=ꢀ274.0 (100) [Mꢀ+ꢀH] . HRMS [(+)-ESI]: m/zꢀ=ꢀ274.0867
+
(calcd. 274.0863 for C18H12NO2, [Mꢀ+ꢀH] ).
1-methylquinolinium chloride (10c)
4.3.3 3-[(4-Carboxyphenyl)ethynyl]-1-methylquinolinium
chloride (10c)
Methyl 4-(quinolin-2-ylethynyl)benzoate (8a: 287 mg,
1 mmol, 100 mol%), or methyl 4-(quinolin-4-ylethynyl)
benzoate (8b: 287 mg, 1 mmol, 100 mol%), or 3-((4-(meth-
oxycarbonyl)phenyl)ethynyl)-1-methylquinolinium
methylsulfate (9c: 413 mg, 1 mmol, 100 mol%) was dis-
solved in methanol (6 mL) and then NaOH (400 mg,
10 mmol, 1000 mol%) in water (3 mL) was added with
stirring. The resulting mixture was stirred overnight. The
solution was acidified (pH 1) and then concentrated in
vacuo. The precipitating crude product was filtered off
and washed with methanol (10 mL) and water (3ꢀ×ꢀ5 mL).
After stirring overnight, the solution was acidified (pH 3)
and then concentrated in vacuo, and the crude product
was purified by column chromatography with CHCl3–
MeOH as eluent. The product was obtained as a brown
1
solid (297.8 mg, 92%). M.p. 98°C. H NMR (600.35 MHz,
[D6]DMSO, 25°C): δꢀ=ꢀ9.98 (d, Jꢀ=ꢀ1.2 Hz, 1H, 2-H), 9.55 (s,
1H, 4-H), 8.55 (d, Jꢀ=ꢀ9.0 Hz, 1H, 8-H), 8.47 (d, Jꢀ=ꢀ9.0 Hz,
1H, 5-H), 8.32 (ddd, Jꢀ=ꢀ1.3, 6.9, 9.0 Hz, 1H, 7-H), 8.10 (t,
Jꢀ=ꢀ9.0 Hz, 1H, 6-H), 8.06 (ddd, Jꢀ=ꢀ1.5, 1.9, 8.3 Hz, 2H, 3′-H,
5′-H), 7.79 (ddd, Jꢀ=ꢀ1.5, 1.9, 8.3 Hz, 2H, 2′-H, 6′-H), 4.67 (s,
3H, CH3) ppm. 13C NMR (150.96 MHz, [D6]DMSO, 25°C):
δꢀ=ꢀ166.5 (o, COO), 152.2 (+, C-2), 148.2 (+, C-4), 137.4 (o,
4.3.1 4-(Quinolin-2-ylethynyl)benzoic acid (15a)
Yellow solid (264.8 mg, 97%). M.p. 181°C. 1H NMR C-9), 136.2 (+, C-7), 131.9 (+, C-2′, C-6′), 131.8 (o, C-4′), 130.6
(600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ8.50 (d, Jꢀ=ꢀ8.3 Hz, 1H, (+, C-6), 130.4 (+, C-5), 129.8 (+, C-3′, C-5′), 128.7 (o, C-4a),
4-H), 8.05 (d, Jꢀ=ꢀ7.8 Hz, 1H, 5-H), 8.05 (d, Jꢀ=ꢀ8.2 Hz, 1H, 124.7 (o, C-1′), 119.2 (+, C-8), 116.3 (o, C-3), 93.7 (o, C-Ph),
8-H), 8.03 (d, Jꢀ=ꢀ8.5 Hz, 2H, 3′-H, 5′-H) 7.85 (ddd, Jꢀ=ꢀ1.4, 6.9, 85.6 (o, C-quinoline), 45.4 (+, CH3) ppm. IR (ATR): νꢀ=ꢀ3031,
8.4 Hz, 1H, 7-H), 7.82–7.80 (m, 3H, 3-H, 2′-H, 6′-H), 7.69 (ddd, 2211, 1695, 1596, 1543, 1520, 1353, 1273, 1253, 1158, 1012,
−1
Jꢀ=ꢀ1.2, 6.9, 8.1 Hz, 1H, 6-H) ppm. 13C NMR (150.96 MHz, [D6] 770, 748, 694, 626, 478, 434 cm . MS (ESI): m/z (%)ꢀ=ꢀ288.0
+
DMSO, 25°C): δꢀ=ꢀ166.6 (o, COO), 147.3 (o, C-8a), 142.0 (o, (100) [M] . HRMS [(+)-ESI]: m/zꢀ=ꢀ288.1022 (calcd. 288.1025
+
C-2), 137.2 (+, C-4), 132.1 (+, C-2′, C-6′), 131.5 (o, C-4′), 130.7 for C19H14NO2, [M] ).
(+, C-7), 129.7 (+, C-3′, C-5′), 128.3 (+, C-8), 128.1 (+, C-5),
127.7 (+, C-6), 127.1 (o, C-4a), 125.4 (o, C-1′), 124.4 (+, C-3) 91.4
(o, C-quinoline), 88.6 (o, C-Ph) ppm. IR (ATR): νꢀ=ꢀ2209, 4.4 Reaction of 9a with NaOH to prepare the
1932, 1715, 1625, 1602, 1590, 1501, 1484, 1405, 1384, 1332,
quinolones (11, 12)
1205, 1176, 1153, 1117, 1018, 963, 906, 874, 856, 843, 827,
−1
765, 755, 685, 659, 621, 556, 522, 468 cm . MS (ESI): m/z 2-[(4-(Methoxycarbonyl)phenyl)ethynyl]-1-methylquino-
+
(%)ꢀ=ꢀ274.0 (100) [Mꢀ+ꢀH] . HRMS [(+)-ESI]: m/zꢀ=ꢀ274.0855 linium methylsulfate (9a: 413 mg, 1 mmol, 100 mol%) was
+
(calcd. 274.0863 for C18H12NO2, [Mꢀ+ꢀH] ).
dissolved in methanol (6 mL) and then NaOH (400 mg,
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10ꢀ ꢀS. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBs
10 mmol, 1000 mol%) in water (3 mL) was added with
stirring. The resulting mixture was stirred overnight. The
precipitated solid was filtered off and washed with metha-
nol and water to give 11 (94.9 mg, 26%). The solution was
acidified (pH 1) and then concentrated in vacuo, and the
crude product was purified by column chromatography
with CHCl3–MeOH as eluent to give 12 (213.5 mg, 70%).
References
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1
Deep green solid (94.9 mg, 26%). M.p. 131°C. H NMR
(600.35 MHz, CDCl3, 25°C): δꢀ=ꢀ7.99 (d, Jꢀ=ꢀ8.6 Hz, 2H, 3′-H,
5′-H), 7.70 (d, Jꢀ=ꢀ8.8 Hz, 2H, 2′-H, 6′-H), 7.18 (ddd, Jꢀ=ꢀ1.5, 7.3,
8.6 Hz, 1H, 7-H), 7.01 (dd, Jꢀ=ꢀ1.5, 7.3 Hz, 1H, 5-H), 6.83 (d,
Jꢀ=ꢀ8.3 Hz, 1H, 8-H), 6.77 (td, Jꢀ=ꢀ0.9, 7.4 Hz, 1H, 6-H), 6.68
(d, Jꢀ=ꢀ10.0 Hz, 1H, 3-H), 6.49 (d, Jꢀ=ꢀ9.8 Hz, 1H, 4-H), 4.46 [11] A. Schmidt, Adv. Heterocycl. Chem. 2003, 85, 67–171.
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(s, 1H, vinylic H), 3.89 (s, 3H, COOCH3), 3.20 (s, 3H, NCH3),
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3.13 (s, 6H, OCH3) ppm. 13C NMR (150.96 MHz, CDCl3, 25°C):
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δꢀ=ꢀ167.2 (o, COO), 148.6 (o, C-1′), 142.4 (o, C-8a), 141.9 (o,
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(+, C-5), 127.47 (+, C-4), 127.3 (+,C-2′, C-6′), 122.0 (o, C-4a),
120.7 (+, C-3), 119.3 (+, C-6), 111.9 (+, C-8), 103.1 (o, CH3OC-
OCH3), 97.1 (+, vinylic C), 52.1 (+, COOCH3), 48.6 (+, OCH3),
34.0 (+, NCH3) ppm. IR (ATR): νꢀ=ꢀ2996, 2936, 2899, 2826,
1722, 1638, 1576, 1434, 1273, 1143, 1104, 1063, 1050, 1018,
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−1
959, 902, 859, 807, 732, 714, 564, 459 cm . MS (ESI): m/z
+
(%)ꢀ=ꢀ366.1 (100) [Mꢀ+ꢀH] . HRMS [(+)-ESI]: m/zꢀ=ꢀ366.1710 [18] A. R. Katritzky, R. Awartani, R. C. Patel, J. Org. Chem. 1982, 47,
+
498–502.
(calcd. 366.1700 for C22H24NO4, [Mꢀ+ꢀH] ).
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ethenolate (12)
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1
Orange solid (213.5 mg, 70%). M.p. 202°C (decomp.). H
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NMR (600.35 MHz, [D6]DMSO, 25°C): δꢀ=ꢀ9.06 (d, Jꢀ=ꢀ9.6 Hz,
1H, 4-H), 8.00 (d, Jꢀ=ꢀ8.3 Hz, 2H, 3′-H, 5′-H), 7.96 (d,
Jꢀ=ꢀ8.5 Hz, 2H, 2′-H, 6′-H), 7.73 (d, Jꢀ=ꢀ5.3 Hz, 1H, 3-H), 7.72
(d, Jꢀ=ꢀ4.3 Hz, 1H, 8-H), 7.66 (dd, Jꢀ=ꢀ1.6, 7.8 Hz, 1H, 5-H), 7.61
(ddd, Jꢀ=ꢀ1.5, 7.2, 8.7 Hz, 1H, 7-H), 7.28 (m, 1H, 6-H), 6.10 (s,
1H, vinylic H), 3.74 (s, 3H, NCH3) ppm. 13C NMR (150.96 MHz,
[D6]DMSO, 25°C): δꢀ=ꢀ184.6 (o, CO), 153.1 (o, C-2), 144.6 (o,
C-1′), 139.8 (o, C-8a), 137.6 (o, C-4′), 134.3 (+, C-3), 131.2 (+,
C-7), 129.0 (+,C-3′, C-5′), 128.3 (+, C-5), 126.6 (+, C-2′, C-6′),
123.0 (o, C-4a), 122.7 (+, C-6), 121.2 (+, C-4), 115.5 (+, C-8),
90.1 (+, vinylic C), 35.2 (+, NCH3) ppm. IR (ATR): νꢀ=ꢀ3449,
3284, 1632, 1607, 1593, 1548, 1508, 1487, 1433, 1392, 1358,
−1
1344, 1208, 1110, 1060, 995, 900, 828, 736, 566, 433 cm .
[31] C. Böttinger, Liebigs Ann. Chem. 1881, 208, 122–141.
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+
MS (ESI): m/z (%)ꢀ=ꢀ306.0 (100) [Mꢀ+ꢀH] . HRMS [(+)-ESI]:
+
m/zꢀ=ꢀ328.0931 (calcd. 328.0939 for C19H15NNaO3, [Mꢀ+ꢀNa] ). [33] R. Breslow, J. Am. Chem. Soc. 1958, 80, 3719–3726.
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S. Batsyts et al.: Chemistry and spectroscopy of CCMBs and PCCMBsꢂ
ꢂ11
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Z. Naturforsch.ꢂ
ꢂ2018 | Volume x | Issue x(b)
Graphical synopsis
a
b
Sviatoslav Batsyts, Francisco J. Ramírez,
Juan Casado, Jan C. Namyslo
and Andreas Schmidt
Chemistry and spectroscopy of cross-
conjugated and pseudo-cross-conjugated
quinolinium-ethynyl-benzoate mesomeric
betaines
https://doi.org/10.1515/znb-2018-0020
Z. Naturforsch. 2018; x(x)b: xxx–xxx
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