Substitution effects on the NMR and DFT studies of 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines

Full text of DOI:10.1002/mrc.4360

Letter - spectral assignments
Received: 24 March 2015
Revised: 18 August 2015
Accepted: 29 August 2015
Published online in Wiley Online Library: 22 September 2015
(wileyonlinelibrary.com) DOI 10.1002/mrc.4360
Substitution effects on the NMR and DFT studies
of 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines
Hamid R. Memarian* and Esmael Sanchooli
position on the 4- and 6-aryl rings is a comparison of the character-
Introduction
istic peaks of 1-NH, 3-NH, 4-CH, 5-CH and OCH protons, which are
3
1
13
Tetrahydropyrimidinone (THPMs) derivatives previously known as
,4-dihydropyimidine-2-(1H)-ones (DHPMs) exhibit a wide range
presented in Table 1. The IR, H NMR and C NMR are given in
Supporting Information.
3
[
1–3]
of biological activities and pharmaceutical properties.
There-
The results presented in Table 1 show that by changing the posi-
tion of the methoxy group on the phenyl ring attached to the
C4-atom of the heterocyclic ring from the 4- to 3- to 2-positions
(compounds 1b, 1c and 1d, respectively), the following peaks are
shifted to higher frequency, as described below:
fore, because of their importance various works are devoted to
the synthesis of these nitrogen containing heterocyclic
[4–6]
compounds.
In our previous studies, we were interested in elu-
cidating the parameters affecting the rate of thermal and photo-
chemical oxidation of some nitrogen containing heterocyclic
compounds, e.g. 1,4-dihydropyridines (DHPs),
[
7]
(i) The chemical shift of the methoxy group goes from 3.745, to
3.755 to 3.836 ppm, respectively.
(ii) The chemical shift of 4-H goes from 5.072, to 5.096 to
2-oxo-1,2,3,4-
[
8]
tetrahydropyrimidines (THPMs) and 2,3-dihydroquinazolinones
[9]
(
DHQZs). The results of experimental work concerning the steric
5.163ppm, respectively.
and electronic effects of the substituent on the light-induced
[
8]
[10]
(iii) The corresponding chemical shift of 5-H goes from 5.156,
5.208 to 5.401 ppm, respectively. Analysis of the AB part
oxidation,
studies
thermal oxidation
in the THPM system indicate that the electronic nature
and steric effect of the additional substituent, on the aryl ring at-
tached to the C -atom, influence the electron density of the hetero-
cyclic ring through the σ bond, while the same effects are observed
via conjugation of the C -substituent with the C double bond
¼C
Scheme 1). Consequently, the oxidative behavior of 5-substituted
and also computational
[
11,12]
(
5-H, 4-H) of the ABX system (5-H, 4-H, 3-H), using equations
[
16]
given in Table 2.3 of R. K. Harris, shows that chemical shift
of the 5-H proton goes from 5.156, to 5.208, and to
4
5
5
.401ppm, and chemical shift of the 4-H proton goes from
.072, to 5.096 and to 5.163 ppm, respectively. Furthermore,
5
5
6
(
the center of the AB part of the ABX system is shifted from
.114, to 5.153, and to 5.274ppm, respectively.
THPMs depends on the steric and electronic effects of the substitu-
ents on the 4- and 5-positions of the heterocyclic ring.
5
Recently, we have investigated the electronic effect of 4-substitution
on the tautomerism in 5-acetyl-2-methoxydihydropyrimidines based
These observations can be explained as follow:The methoxy
group on each position of the aryl ring behaves as an electron-
withdrawing substituent because of the inductive effect of the
oxygen atom in this group; while because of the participation of
one of its lone pairs in conjugation with the aromatic ring double
bonds, this group can act as an effective electron-donating group.
As the balance of these two effects, the methoxy group displays
the role of an electron-donating group, which decreases the HOMO
energy of the methoxy-substituted aryl ring. In contrast to the loca-
tion of this group on the 3-position, its presence on the 2- or
[
13]
on the NMR and computational DFT studies.
to these studies, we were interested in investigating these effects
In continuation
[
14,15]
in 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines (1a–g),
containing a methoxy group on the different positions of either
- or 6-aryl rings, especially on the chemical shifts of some charac-
4
teristic NMR peaks. For better observation of these effects by the
aryl substitution via σ- or π-interaction, especially the steric effect,
the heterocyclic ring does not contain any substituent on the
5
-position (Scheme 2).
4
-positions allows delocalization of the oxygen lone pair towards
the C -atom of the aryl ring directly attached to the C -atom of
the heterocyclic ring, i.e. the C -atom in the numbering Scheme 2.
1
4
8
This electron participation is illustrated in Scheme 4. In compound
Results and discussion
Compounds 1a–g were prepared by condensation of correspond-
ing chalcones with urea in the presence of NaH in dry THF under ar-
gon atmosphere (Scheme 3). These compounds were characterized
1
* Correspondence to: Hamid R. Memarian, Department of Chemistry, University of
Isfahan, 81746-73441 Isfahan, I. R. Iran. E-mail: memarian@sci.ui.ac.ir
by observation of the characteristic absorptions in the IR, H NMR,
13
C NMR and UV spectra. The best way to elucidate the possible ste-
ric and electronic effects of the methoxy group depending on its
Department of Chemistry, University of Isfahan, Isfahan, I. R. Iran
Magn. Reson. Chem. 2016, 54, 178–183
Copyright © 2015 John Wiley & Sons, Ltd.

NMR and DFT studies of 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines
Scheme 1. 2-Oxo-1,2,3,4-tetrahydropyrimidines.
Scheme 4. Participation of the oxygen lone pair in the CH
3
O group on the
Scheme 2. 5-Unsubstituted 2-oxo-1,2,3,4-tetrahydropyrimidines.
electron-density enhancement of the C -atom.
8
of its effective electron-donating character, the chemical shift of
the CH O group appears at lower frequency compared to those
3
on the 3- and 2-positions in the compounds 1c and 1d, respec-
tively. The electron-donating influence of the para-methoxyphenyl
group via the σ bond (C ―C bond) causes a shielding effect on the
8
4
4- and 5-hydrogens. Consequently, their resonances appear at
Scheme 3. Synthesis of 5-unsubstituted THPMs.
lower frequency compared to those in the parent compound 1a.
Because of the steric hindrance of the 2-methoxy group with the
heterocyclic ring in compound 1d, the group has only one possible
orientation for its methyl group allowing the participation of the
oxygen lone pairs in conjugation with the aromatic ring (1d-RS).
On the other hand, possible intramolecular hydrogen bonding with
the 3-NH moiety decreases its electron donating ability (1d-HB). For
these reasons, this group on the 2-position does not allow effective
participation of the oxygen lone pair to conjugate with the aryl
ring. Consequently, because of possible hydrogen bonding of the
oxygen lone pair of the methoxy group on this position, protons
of the methyl group resonance at higher frequency. The electron-
1
Table 1. Steric and electronic effects in the H NMR chemical shifts (δ,
ppm) of the characteristic peaks
a
1
X
Y
OCH
3
4-H
5-H
3-NH
1-NH
b
a
b
c
H
H
—
5.13
5.07
5.10
5.16
5.07
5.12
4.85
5.16
5.15
5.21
5.40
5.10
5.21
5.08
7.29–7.37
7.19
8.59
8.52
8.58
8.55
8.50
8.58
8.12
4-OCH
3-OCH
2-OCH
3
H 3.74
H 3.76
H 3.84
b
b
b
b
3
7.28–7.38
6.97–7.03
7.25–7.39
7.24–7.39
7.16
d
e
f
3
H
H
H
4-OCH
3-OCH
2-OCH
3
3.76
3.78
3.79
3
3
withdrawing effect of the 2-CH O group via the σ bond on the
4- and 5-hydrogens shifts their resonances to higher frequency
g
3
a
compared to that of the parent molecule 1a.
The observed electron-donating behavior of the para-
methoxyphenyl group on the 6-position of the heterocyclic ring
Appearance of this peak is affected by shaking the sample with D
because of the removal of the coupling with 3-ND.
2
O,
b
The corresponding signal is overlapped with the aromatic
hydrogens, and the integral ratio is decreased upon shaking the
(
compound 1e) increases the electron density on the C14-atom
attached to the C -atom of the heterocyclic ring (1e-RS.I), which
may also increase the electron population on the C -atom via
2
sample with D O, because of the H/D-exchange as is also
6
mentioned in the experimental section.
5
delocalization of the negative charge (1e-RS.II). The latter contribu-
tion is only possible if the aryl ring can orient co-planar with
the C
6
¼C
5
double bond without any repulsion between its
1d, having the methoxy group on the 2-position, only a suitable
ortho-hydrogens and 1-NH and 5-CH moieties, known as ortho-
repulsion.
[
17,18]
upward orientation of this group allows the possible formation of
a hydrogen bond between its oxygen atom and the hydrogen
atom of the 3-NH group with a distance of 2.4514 Å (1d-HB). The
same hydrogen bond is also possibly formed in compound 1g,
but with the hydrogen atom of the 1-NH group with a distances
of 2.2179 Å. The DFT optimized structures of compounds 1d and
This leads to the shift of 5-H and also 4-H reso-
nances to lower frequency compared to that of the unsubstituted
compound 1a (Scheme 5 up-right). In contrast to this observation,
only the inductive effect (-I effect) of the methoxy group on the
meta-position causes a shift of 5-H resonance to higher frequency
compared to that of the unsubstituted compound 1a (Scheme 5
middle). In compound 1g, the presence of the methoxy group on
the 2-position of the 6-aryl ring in the suitable orientation may al-
low the formation of hydrogen bonding between the oxygen lone
1g, presented in Fig. 1, indicates also possible intramolecular hydro-
gen bonding in these molecules. The methoxy group on the para-
position of the C -aryl ring does not have any steric hindrance for
4
co-planar positioning with the aryl ring. Such alignment allows
participation of the methoxy lone pairs to conjugate with the aro-
matic ring (1b-RS, RS= resonance structure). Therefore, because
pairs and the N ―H moiety. In this case, the occurrence of a posi-
1
tive charge on the oxygen atom causes a shift of the CH protons
3
resonance to higher frequency compared to those of the 1e or 1f
Magn. Reson. Chem. 2016, 54, 178–183
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/mrc

H. R. Memarian and E. Sanchooli
Figure 1. DFT optimized structure of 1d (left) and 1g (right) showing the intramolecular hydrogen bonding between the oxygen atom of the methoxy group
and the hydrogen atom of 3-NH and 1-NH moieties, respectively.
is achieved by induction through the σ-bonds. Therefore, the
substituted aryl group will be considered as a σ-donor.
The proposed ortho-repulsion in the present study, which causes
incomplete co-planarity orientation of the 6-aryl ring towards the
heterocyclic ring is also observed in the x-ray crystal structure anal-
[
19]
ysis of the oxidized form of 1a. It is expected that for the forma-
tion of an effective hydrogen bond in compound 1g, the oxygen
1
atom of the methoxy group, H and N atoms should be in one plane
and even having all these three atoms on a straight line, which is
not observed in the optimized structure of this compound. That
means, a formation of a regular and planar hydrogen bond
6
-membered ring is not observed by this interaction. Orientation
of the 6-aryl ring with the heterocyclic ring denoted as
= N ―C ―C14―C15 dihedral angle supports the argument, that
a twisted 6-membered (or non-planar) ring is formed, which dis-
plays in the calculated γ dihedral angle of 44.6°. Therefore, because
γ
1
1
6
1
of the failure of an effective hydrogen bond between the 2-CH O
3
group on the 6-aryl ring and 1-NH, high frequency shift in the
1-NH peak is not observed.
To elucidate the proposed possible intramolecular hydrogen
bonding between the lone pair of the 2-CH O group with the 1-
NH and 3-NH moieties in compounds 1d and 1g, respectively,
3
Scheme 5. Participation of the oxygen lone pair in the CH
3
O group on the
electron-density enhancement of the C14- and C -atoms.
5
and their effects on the total energy content of the molecule, the
4
-aryl and 6-aryl rings are rotated around the C ―C8 and the
4
compound, in which the methoxy group is located on the para- or
meta-positions, respectively. On the other hand, as expected, delo-
calization of the oxygen lone pair of the 2-methoxy group in com-
pound 1g increases the electron density on the C14-atom (1g-RS.I)
C
14―C
6
single bonds starting from the optimized structure in com-
pounds 1d and 1g, respectively. The results indicate that by rota-
tion around the C ―C single bond in 1d¸ a non-planar hydrogen
4
8
bonded 6-membered ring is formed and the energy of the mole-
5
and possibly on the C -atom (1g-RS.II). Therefore, the shift of the
cule increases about 19.42 kJ/mol. In the case of compound 1g,
5-H resonance to lower frequency compared to that of 1a is quite
the rotation around the C14―C single bond leads to the formation
6
natural (Scheme 5 bottom). DFT studies on the optimized
structures of THPMs considered in the present study indicate that
because of the ortho-repulsion, the 6-aryl ring in these com-
of a planar hydrogen bonded 6-membered ring with an increase of
the energy about 9.33 kJ/mol. These results indicate that the forma-
tion of the possible intramolecular hydrogen bonds in both com-
pounds are not expected. Consequently, a high frequency shift in
the corresponding 3-NH and 1-NH protons in compounds 1d and
1g is not observed.
Cyclic voltammetric measurements of compounds considered in
the present study elucidate the significant electronic effect of the
3
CH O group on the para-position of either 4-aryl or 6-aryl rings
pounds is not completely co-planar with the C
6
¼C
5
double bond
regardless of the additional substituent on this ring. That means
that, owing to the observed ortho-repulsion, effective through-
conjugation of the oxygen lone pair in the methoxy group either
on the para- or ortho-position of the phenyl ring attached to the
C -atom of the heterocyclic ring towards the C -atom is not
6
5
possible. In these cases, because of the observed ortho-repulsion,
without any steric hindrance compared to that on the ortho-
position. This results in lower oxidation potentials of the para-
substituent compared to those of the ortho-substituent and even
the 4- or 2-CH OC H groups on the 6-position cannot increase
3
6 4
the electron population on the C -atom such electron donation
5
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Copyright © 2015 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2016, 54, 178–183

NMR and DFT studies of 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines
Table 2. The oxidation peak potential (Ep), versus ferrocene redox potential (0.583 V), obtained from cyclic voltammograms in acetonitrile for THPMs
(1a–g)
Compound
Ep
1a
1b
1c
1d
1e
1f
1g
1.274
1.154
1.204
1.248
1.165
1.245
1.181
Table 3. Selected bond length (Å) and torsion angle (°) corresponding to the B3LYP/6-31++G(d,p) optimized structures of 4,6-diaryl-2-oxo-1,2,3,4-
tetrahydropyrimidines (THPMs)
1
N
1
―C
2
C ―N
2
3
N ―C
3
4
C ―C
4
5
C ―C
5
6
N
1
―C
6
C ―O
2
7
C ―C
4
8
6
C ―C14
α
1
α
2
β
1
β
2
γ
1
γ
2
a
b
c
1.3889 1.3680 1.4680 1.5093 1.3462 1.4026 1.2290 1.5312 1.4837
1.3876 1.3714 1.4726 1.5125 1.3469 1.4017 1.2289 1.5246 1.4835
1.3878 1.3685 1.4687 1.5094 1.3461 1.4024 1.2295 1.5327 1.4835
1.3952 1.3656 1.4737 1.5049 1.3469 1.4029 1.2291 1.5357 1.4839
1.3874 1.3693 1.4698 1.5090 1.3467 1.4026 1.2294 1.5322 1.4814
1.3867 1.3716 1.4711 1.5115 1.3464 1.4012 1.2288 1.5273 1.4842
1.3896 1.3703 1.4685 1.5116 1.3476 1.4037 1.2295 1.5266 1.4867
2.5
ꢀ1.1
3.1
ꢀ52.1
ꢀ54.35
ꢀ51.3
68.5
71.2
67.5
ꢀ37.5
37.7
140.2
ꢀ140.8
140.5
ꢀ18.3
8.3
ꢀ1.8
ꢀ0.0
ꢀ2.4
2.7
72.4
ꢀ37.5
38.1
d
e
f
14.1
ꢀ167.3
67.4
ꢀ139.8
140.5
10.4
ꢀ56.4
ꢀ53.9
ꢀ54.0
ꢀ37.8
38.6
ꢀ16.8
ꢀ11.4
67.9
ꢀ139.7
ꢀ138.4
g
1.8
67.6
44.6
1 1 2 3 4 2 1 6 5 4 1 3 4 8 9 2 5 4 8 9 1 1 6 2 5 6
α = N ―C ―N ―C ; α = N ―C ―C ―C ; β = N ―C ―C ―C ; β = C ―C ―C ―C ; γ = N ―C ―C14―C15; γ = C ―C ―C14―C15
lower than those of the parent compound 1a. The electron-
donating ability of the para-methoxyphenyl group via the σ bond
eases the electrochemical oxidation of the heterocyclic ring. The
oxidation peak potentials are presented in Table 2.
Experimental
5-Unsubstituted 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines con-
sidered in the present study were synthesized by the procedure de-
scribed below. Melting points were determined on a Stuart Scientific
SMP2 apparatus and are not corrected. IR spectra were recorded
from KBr-discs on a Jasco FT/IR-6300 spectrometer. The H and
NMR spectra (DMSO-d ) were recorded on Bruker Avance III 400
The electronic nature of the heterocyclic ring is not only depen-
dent on the electron donation of the substituted 4- and 6-aryl rings,
but also depends on the extent of the contribution of the lone pairs
on the N - and N -atoms in conjugation with the C ¼C and C ¼O
1
13
C
1
3
6
5
2
7
6
double bonds. The DFT-optimized selected geometric parameters,
including bond lengths and torsion angles, Table 3, show clearly
that the 4-aryl and especially 6-aryl rings are not completely co-
planar with the heterocyclic ring. The extent of deviation from the
co-planar orientation of the 4- or 6-aryl rings, measured by the β1
and β or γ and γ angles, respectively, are also partially dependent
spectrometers at 400.133 and 100.62 MHz at room temperature.
1
The H NMR spectra are reported as follows: chemical shifts, [multi-
plicity, number of protons, coupling constants J (Hz) and
assignment]. UV spectra were taken with Shimadzu UV-160
spectrometer.
2
1
2
on the inner-ring dihedral angles α
electronic nature of the heterocyclic ring is also affected by the de-
localization of the N and N lone pairs towards the C and
¼C
¼O double bonds. Cross delocalization of the N lone pair to-
wards the C and C ¼O double bonds is in competition with
¼C
the effective conjugation of the 6-aryl ring and the C double
¼C
bond. Because of the observed ortho-repulsion, conjugation of
the 6-aryl ring and the C double bond is not effective, which
¼C
is supported by the calculated γ and γ dihedral angles. Therefore,
effective through-conjugation of the oxygen lone pair of the
methoxy group on the 2- and 4-positions towards the C -atom is
not expected. Comparatively, shorter N ―C bond lengths in these
compounds than the N ―C bond lengths indicate that the N lone
pair is more delocalized with the C double bond than with the
¼O
¼C double bond. This can be attributed to the greater electron
affinity of the carbonyl group (C ) compared to that of the
¼O
¼C double bond.
1 2
and α . This means that the
Cyclic voltammetry measurements
For these measurement solutions with concentrations of 1 mM of
THPMs and 50mM of tetrabutylammonium perchlorate in acetoni-
trile were prepared. The CV measurements were performed using
SAMA 500 Potentio/Galvanostat. All electrochemical experiments
were carried out in a conventional three-electrode system at room
temperature. A silver electrode, a large area Pt plate (99.99%), and a
glass carbon electrode (GCE) were used as reference, counter, and
working electrodes, respectively.
1
3
6
5
C
2
7
1
6
5
2
7
6
5
6
5
1
2
5
1
2
Synthesis of 5-unsubstituted 3,4-dihydropyrimidin-2(1H)-ones
(1a–g)
1
6
1
2
7
To a NaH suspension in dry THF (1mmol in 6 ml) under argon atmo-
sphere were added 1 mmol of appropriate chalcone and 1.2 mmol
of urea. The mixture was heated at 75 °C in oil bath for 15–30 min,
then was cooled and quenched with water. The solid products were
separated and recrystallized from ethanol.
C
6
5
2
7
C
6
5
Conclusion
4,6-Diphenyl-2-oxo-1,2,3,4-tetrahydropyrimidine (1a)
In this work the steric and electronic effects of the methoxy substitu-
tion on the chemical shift of some characteristic peaks in H NMR spec-
M.p. 233–235 °C (Dec.). IR (KBr): ν = 3334, 3224, 3086, 2917, 1685,
1488, 1448, 1333, 1255, 1155, 970, 759 cm . H NMR (400MHz
1
ꢀ1
1
tra of 5-unsubstituted 4,6-diaryl-2-oxo-1,2,3,4-tetrahydropyrimidines
were investigated. DFT studies on these compounds support the
results of the experimental works.
DMSO-d6): δ = 5.13 (dd, J = 2.4Hz, 4.4 Hz, 4-H), 5.16 (brd d,
J = 4.4Hz, 5-H), 7.29–7.37 (m, 9H, aromatic H and N ―H), 7.51–
3
1
7.54 (m, 2H, aromatic H), 8.59 ppm (s, 1H, N1―H). H NMR
Magn. Reson. Chem. 2016, 54, 178–183
Copyright © 2015 John Wiley & Sons, Ltd.
wileyonlinelibrary.com/journal/mrc

H. R. Memarian and E. Sanchooli
(
5
400 MHz DMSO-d6+ D O): δ = 3.96 (s, HOD), 5.13 (d, J = 4.4 Hz, 4-H),
6-(4-Methoxyphenyl)-4-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine
(1e)
2
.16 (d, J = 4.4Hz, 5-H), 7.29–7.37 (m, 8H, aromatic H), 7.51–
13
7
.54 ppm (m, 2H, aromatic H). C NMR (100 MHz DMSO-d6):
), 98.72 (C ), 125.31, 126.20, 127.20, 128.36, 128.48,
28.53, 134.04, 135.42, 145.15, 153.53 (CO). UV (CHCl
log ε) = 279.4 nm (3.50), 243.6 (3.49).
M.p. 205–207 °C (Dec.). IR (KBr): ν = 3330, 3222, 3079, 2931, 2836,
δ = 54.95 (C
1
(
4
5
ꢀ
1
1
688, 1608, 1517, 1480, 1455, 1295, 1256, 1182, 1029, 827 cm .
3
): λmax
1
H NMR (400 MHz DMSO-d6): δ = 3.76 (s, 3H, OCH ), 5.07 (brd d,
3
J = 4.4Hz, 4-H), 5.10 (observe that d, J = 4.4 Hz, 5-H), 6.90 (d,
J = 8.8Hz, 2H, aromatic H), 7.25–7.39 (m, 6H, aromatic H and
N ―H), 7.47 (d, J = 9.2Hz, 2H, aromatic H), 8.50 ppm (s, 1H,
4
-(4-Methoxyphenyl)-6-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine
3
1
N
1
―H). H NMR (400MHz DMSO-d6+ D
2
O): δ = 3.71 (s, 3H, OCH
3
),
(1b)
4.06 (s, HOD), 5.08–5.10 (observe that m, 2H, 4-H, 5-H), 6.90 (d,
M.p. 194–196 °C. IR (KBr): ν = 3384, 3245, 3114, 2952, 1672, 1609,
J = 7.6Hz, 2H, aromatic H), 7.24–7.36 (m, 5H, aromatic H),
ꢀ
1
1
13
1508, 1463, 1297, 1241, 1165, 1035, 844, 749 cm
. H NMR
7
.40 ppm (d, J = 7.6Hz, 2H, aromatic H). C NMR (100 MHz
(400 MHz DMSO-d6): δ = 3.74 (s, 3H, OCH ), 5.07 (brd d, J = 4.4Hz,
3
DMSO-d6): δ = 54.57 (C ), 55.08 (OCH ), 97.66 (C ), 113.86, 125.98,
4
3
5
4
-H), 5.15 (brd d, J =4.4 Hz, 5-H), 6.93 (d, J = 8.8 Hz, 2H, aromatic
H), 7.19 (s, 1H, N ―H), 7.26 (d, J =8.4 Hz, 2H, aromatic H), 7.35–
.38 (m, 3H, aromatic H), 7.53 (dd, J = 2.0Hz, 8.0Hz, 2H, aromatic
126.51, 127.42, 128.65, 134.43, 144.66, 154.11 (CO), 159.44
3
(
C-OCH ) ppm. UV (CHCl ): λmax (log ε) = 280.6 nm (3.43), 245.4 (3.5).
3
3
7
1
H), 8.52 ppm (s, 1H, N
δ = 3.70 (s, 3H, OCH ), 3.93 (s, HOD), 5.07 (d, J = 4.4Hz, 4-H), 5.16
d, J= 4.8 Hz, 5-H), 6.91 (d, J =8.4 Hz, 2H, aromatic H), 7.24 (d,
J = 8.4 Hz, 2H, aromatic H), 7.31–7.36 (m, 3H, aromatic H),
1 2
―H). H NMR (400 MHz DMSO-d6 + D O):
3
6-(3-Methoxyphenyl)-4-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine
(1f)
(
13
M.p. 176–178 °C. IR (KBr): ν = 3341, 3226, 3086, 2949, 2833, 1689,
7
.47 ppm (d, J = 6.8Hz, 2H, aromatic H). C NMR (100 MHz
DMSO-d6): δ = 54.35 (C ), 55.09 (OCH ), 98.96 (C ), 113.86, 125.30,
27.47, 128.36, 134.06, 134.12, 135.17, 135.27, 137.29, 153.42 (CO),
58.50 (C-OCH ) ppm. UV (CHCl ): λmax (log ε) = 279.4 nm (3.50),
43.6 (3.49).
ꢀ
1 1
1
609, 1487, 1451, 1283, 1049, 972, 775 cm . H NMR (400MHz
DMSO-d6): δ = 3.78 (s, 3H, OCH ), 5.12 (m, 1H, 4-H), 5.21 (brd s, 1H,
-H), 6.88–6.91 (m, 1H, aromatic H), 7.08–7.11 (m, 2H, aromatic H),
.24–7.39 (m, 7H, aromatic H and N ―H), 8.58 ppm (s, 1H, N ―H).
O): δ = 3.73 (s, 3H, OCH ), 4.03 (s,
4
3
5
3
1
1
2
5
7
3
3
3
1
1
H NMR (400 MHz DMSO-d6+ D
2
3
HOD), 5.12 (d, J = 4.4 Hz, 4-H), 5.23 (d, J = 4.8Hz, 5-H), 6.90 (dd,
J = 2.0Hz, 8.4 Hz, 1H, aromatic H), 6.99 (brd s, 1H, aromatic H), 7.05
4
-(3-Methoxyphenyl)-6-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine
(
d, J= 8.0Hz, 1H, aromatic H), 7.24–7.38 ppm (m, 6H, aromatic H).
(1c)
1
3
C NMR (100MHz DMSO-d6): δ = 54.93 (C ), 55.07 (OCH ), 98.86
4
3
M.p. 196–197 °C. IR (KBr): ν = 3393, 3330, 3222, 3085, 2932, 1687, 1604,
(C5), 110.32, 114.58, 117.63, 126.22, 127.19, 128.52, 129.40, 135.27,
ꢀ
1 1
1
488, 1319, 1269, 1148, 1051, 765 cm . H NMR (400 MHz DMSO-d6):
δ =3.76 (s, 3H, OCH ), 5.10 (dd, J= 2.0 Hz, 4.4 Hz, 4-H), 5.21 (brd d,
J= 4.0 Hz, 5-H), 6.85 (dd, J= 2.0 Hz, 8.0 Hz, 1H, aromatic H), 6.91 (m,
H, aromatic H), 6.94 (d, J= 7.6 Hz, 1H, aromatic H), 7.28–7.38 (m, 5H,
aromatic H and N ―H), 7.52 (dd, J= 1.6 Hz, 7.6 Hz, 2H, aromatic H),
.58 ppm (s, 1H, N
s, 3H, OCH ), 3.98 (s, HOD), 5.10 (d, J= 4.8 Hz, 4-H), 5.21 (d, J=4.8Hz,
-H), 6.83 (dd, J= 2.0 Hz, 8.0 Hz, 1H, aromatic H), 6.86 (brd s, 1H, aro-
matic H), 6.91 (d, J= 8.0 Hz, 1H, aromatic H), 7.27–7.40 (m, 4H, aromatic
1
35.39, 135.45, 145.12, 153.46 (CO), 159.20 (C-OCH ) ppm. UV
3
3
(
CHCl ): λ
(log ε) = 277.2 nm (3.71), 250 (3.22).
max
3
1
3
6-(2-Methoxyphenyl)-4-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine
(1g)
1
8
(
5
1 2
―H). H NMR (400 MHz DMSO-d6 +D O): δ =3.71
3
M.p. 174–176 °C. IR (KBr): ν = 3337, 3234, 3084, 3026, 2916, 2840,
ꢀ
1
1
704, 1601, 1492, 1462, 1431, 1283, 1244, 1149, 1023, 760 cm .
1
13
H NMR (400 MHz DMSO-d6): δ = 3.79 (s, 3H, OCH ), 4.85 (brd d,
3
H), 7.46 ppm (dd, J= 1.6 Hz, 6.4 Hz, 2H, aromatic H). C NMR (100 MHz
DMSO-d6): δ = 54.78 (C ), 55.00 (OCH ), 98.59 (C ), 111.95, 112.34,
18.27, 125.31, 128.36, 128.48, 129.65, 133.98, 134.04, 135.37, 135.48,
J = 4.0Hz, 4-H), 5.08 (brd d, J = 4.0Hz, 5-H), 6.92 (t, J = 7.6Hz, 1H, ar-
4
3
5
omatic H), 7.04 (d, J = 8.4Hz, 1H, aromatic H), 7.16 (s, N ―H), 7.23–
3
1
1
7
.38 (m, 7H, aromatic H), 8.12 ppm (s, 1H, N ―H). H NMR (400 MHz
1
146.73, 153.45 (CO), 159.42 (C-OCH ) ppm. UV (CHCl ): λ
(log ε)
max
3
3
2 3
DMSO-d6 + D O): δ = 3.76 (s, 3H, OCH ), 3.85 (s, HOD), 4.89 (d,
J = 4.4Hz, 4-H), 5.09 (d, J = 4.4 Hz, 5-H), 6.92 (t, J = 7.6 Hz, 1H, aro-
=
283.2 nm (3.58), 245 (3.81).
matic H), 7.02 (d, J = 8.4Hz, 1H, aromatic H), 7.21–7.36 ppm (m, 7H,
1
3
aromatic H). C NMR (100 MHz DMSO-d6): δ = 55.03 (C
(
1
4
), 55.47
), 111.49, 120.21, 123.90, 126.33, 127.14, 128.47,
29.33, 129.88, 134.13, 134.24, 145.28, 152.95, 153.00 (CO), 156.74
) ppm. UV (CHCl ): λmax (log ε) = 281.4nm (3.66), 250 (3.48).
4
-(2-Methoxyphenyl)-6-phenyl-2-oxo-1,2,3,4-tetrahydropyrimidine
3 5
OCH ), 100.08 (C
(1d)
M.p. 211–213 °C. IR (KBr): ν = 3330, 3212, 3092, 2934, 2837, 1686,
(
C-OCH
3
3
ꢀ
1 1
1
(
4
592, 1480, 1329, 1285, 1242, 1106, 1026, 756 cm
400 MHz DMSO-d6): δ = 3.84 (s, 3H, OCH ), 5.16 (brd d, J = 4.4Hz,
-H), 5.40 (brd d, J = 4.4Hz, 5-H), 6.97–7.03 (m, 3H, aromatic H and
. H NMR
3
Acknowledgements
We are thankful to the Research Council and Office of Graduate
Studies of the University of Isfahan for their financial support.
N ―H),7.25–7.37 (m, 5H, aromatic H), 7.49 (dd, J= 1.6Hz, 7.6Hz,
3
1
2
H, aromatic H), 8.55 ppm (s, 1H, N ―H). H NMR (400 MHz
1
DMSO-d6+ D O): δ = 3.80 (s, 3H, OCH ), 3.92 (s, HOD), 5.16 (d,
2
3
J = 4.8 Hz, 4-H), 5.38 (d, J = 4.4Hz, 5-H), 6.95–7.01 (m, 2H, aromatic
H), 7.23–7.37 (m, 5H, aromatic H), 7.43 ppm (d, J = 6.8Hz, 2H, aro- References
1
3
matic H). C NMR (100 MHz DMSO-d6): δ = 49.37 (C ), 55.46
4
[
1] G. C. Ravnyak, S. D. Kimball, B. Beyer, G. Cucinotta, J. D. DiMarco,
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OCH ), 97.57 (C ), 110.91, 120.55, 125.22, 126.25, 128.24, 128.35,
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Copyright © 2015 John Wiley & Sons, Ltd.
Magn. Reson. Chem. 2016, 54, 178–183

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Magn. Reson. Chem. 2016, 54, 178–183
Copyright © 2015 John Wiley & Sons, Ltd.
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