Tautomerism in 2-ketomethylquinolineazines

Article abstract of DOI:10.1016/j.molstruc.2012.05.034

A series of new azines were prepared in three steps. Structures of all compounds have been elucidated using spectroscopic methods and elemental analysis. Our studies show that in chloroform solution generally two tautomeric forms are in equilibrium. In some cases, one tautomer was the dominant species.

Full text of DOI:10.1016/j.molstruc.2012.05.034

Journal of Molecular Structure 1032 (2013) 138–146
Contents lists available at SciVerse ScienceDirect
Journal of Molecular Structure
journal homepage: www.elsevier.com/locate/molstruc
Tautomerism in 2-ketomethylquinolineazines
a
b
Hossein Loghmani-Khouzani a, , Alireza Minaeifar , Ryszard Gawinecki
⇑
a Department of Chemistry, University of Isfahan, Isfahan 81746-73441, Iran
b Department of Chemistry, University of Technology and Life Sciences, Seminaryjna 3, PL-85-326 Bydgoszcz, Poland
h i g h l i g h t s
"
"
"
"
"
Structure of a new series 2-ketomethylquinolineazines and identification of their tautomeric forms.
Strength intramolecular hydrogen bonding.
Different tautomers to be present in solutions.
Tauatomerism.
Azines.
a r t i c l e i n f o
a b s t r a c t
Article history:
A series of new azines were prepared in three steps. Structures of all compounds have been elucidated
using spectroscopic methods and elemental analysis. Our studies show that in chloroform solution gen-
erally two tautomeric forms are in equilibrium. In some cases, one tautomer was the dominant species.
Ó 2012 Elsevier B.V. All rights reserved.
Received 20 February 2012
Received in revised form 14 May 2012
Accepted 14 May 2012
Available online 29 May 2012
Keywords:
2-Ketomethylquinolines
2-Ketomethylquinolinehydrazones
Azines
Tautomerism
1. Introduction
ane (TMS) as an internal standard. Mass spectra were obtained on
GC/MS/DS Varient-Sinngan spectrometer (EI mode at 70 eV).
Azines are a class of compounds that undergo a wide variety of
chemical processes and have interesting chemical properties.
These compounds are also valuable intermediates for synthesis of
heterocyclic compounds [1], show biological activities including
antibacterial [2], antifungal [3] and antitumor [4], form complexes
with transition metals [5], and are used as nonlinear optical mate-
rials [6] and in designing of liquid crystals [7].
Elemental analysis was done on CHN-O-RAPID, Heraeus CHNS.
UV–VIS spectra were recorded on Shimadzu UV-160 spectropho-
tometer. All 2-ketomethylquinoines were characterized by com-
parison of their spectroscopic data (IR, 1H NMR) and melting
points with those of reported in the literature [8].
2.1. General procedure for synthesis of symmetrical 2-ketomethylquin
2. Experimental
olineazine (3a)
Melting points were obtained by a Stuart Scientific SMP2 appa-
ratus and are uncorrected. Yields refer to the isolated products and
all products were characterized by their physical and spectral data.
IR spectra were recorded on IR-435 Shimadzu spectrophotometer.
1H and 13C NMR (500 and 125 MHz) spectra were recorded on a
Bruker-Avance AQS 500 spectrometer in CDCl3 and tetramethylsil-
2-Ketoiminomethylquinolines 1a–1b, Scheme 2 were prepared
by following Rousel [8c] literature method. 1a was later used in
preparation of symmetrical azines 3a. 2-Ketoiminomethylquino-
line (1a) (2.0 mmol) was dissolved in the minimum amount of
ethanol and a drop of acetic acid and hydrazine monohydrate
(1.0 mmol) was added. Content of the reaction vessel was stirred
vigorously at 80 °C for 30 min. The reaction mixture was then
cooled and the white solid formed separated by filtration. The
crude product was purified by crystallization from ethanol.
⇑
Corresponding author. Tel.: +98 3116687411; fax: +98 3116689732.
E-mail address: loghmani_sh@hotmail.com (H. Loghmani-Khouzani).
0022-2860/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.molstruc.2012.05.034

H. Loghmani-Khouzani et al. / Journal of Molecular Structure 1032 (2013) 138–146
139
1, PhLi,ether, N2
2, R1COOR
CH3
1, NH2NH2,H2O
2, AcOH, EtOH
NH2
R1
N
AcOH, EtOH
R2COR3
R1
+
N
N
N
H
N
H
3, HCl (1M)
O
R1
2-A
N
2-B
NH2
2a, R1=Ph, 2b, R1=p-MePh, 2c, R1=p-MeOPh, 2d, R1= But
R1
R2
N N R3
N
H
N
N
H
R1
R2
R3
R1
R2
R3
N
N
N
N
3-A
3-B
3-C
Scheme 1. Synthesis of 2-ketomethylquinolineazines.
2.2. (Z)-3,3-Dimethyl-1-(quinolin-2(1H)-ylidene)butan-2-imine (1a)
2.6. (Z)-2-(2-Hydrazono-2-phenylethyl)quinoline (2a)
White needles; mp 100–102 °C; IR (KBr)
1530 cmꢀ1
m
: 3410, 1625, 1590,
White needles; mp 121–123 °C; IR (KBr)
m: 3340, 3135, 1630,
;
1H NMR (500 MHz, CDCl3): d 1.2 (s, 9H, CH3), 5.2 (s,
1614, 1595 cmꢀ1 1H NMR (500 MHz, CDCl3): d 4.30 (s, 2H, CH2),
;
1H, CH), 6.8–8.00 (m, 8H, C9H6N and 2NH).
6.5 (broad, 2H, NH2). 7.0–8.5 (m, 11H, C9H6N, C6H5).
2.7. (Z)-2-(2-Hydrazono-2-p-tolylethyl)quinoline (2b)
2.3. 1-Phenyl-2-(quinolin-2-yl)ethanimine (1b)
White needles; mp 152–154 °C; IR (KBr)
White needles; mp 105–107 °C; IR (KBr)
m: 3360, 3130, 1645,
m
: 3340, 1615, 1585,
1600, 1590 cmꢀ1 1H NMR (500 MHz, CDCl3): d 2.3 (s, 3H, CH3),
;
1530 cmꢀ1 1H NMR (500 MHz, CDCl3): d 5.8 (s, 1H, CH), 6.5–8.0
;
4.2 (s, 2H, CH2), 6.5 (broad, 2H, NH2), 7.0–8.2 (m, 10H, C9H6N, p-
C6H4).
(m, 13H, C9H6N, C9H5 and 2NH), 6.5 (broad, 2H, 2NH).
2.4. (1Z,2Z)-1,2-bis(3,3-Dimethyl-1-(quinolin-2-yl)butan-2-ylidene)
hydrazine (3a)
2.8. (Z)-2-(2-Hydrazono-2-(4-methoxyphenyl)ethyl)quinoline (2c)
White needles; mp 152–154 °C; IR (KBr)
m: 3365, 3130, 1635,
1605, 1590 cmꢀ1 1H NMR (500 MHz, CDCl3): d 3.8 (s, 3H, OCH3),
;
White needles; mp 174–176 °C; UV (nm) in choloroform; 317.0,
303.5, 278.5; IR (KBr) m ;
: 1615, 1590, 1570, 1555, 1500 cmꢀ1 1H
4.8 (s, 2H, CH2), 6.5 (broad, 2H, NH2), 6.5–8.5 (m, 10H, C9H6N, p-
NMR (500 MHz, CDCl3): d 1.03 (s, 18H, CH3), 4.27 (s, 4H, CH2),
7.44–8.12(m, 12H, ArAH). 13C NMR (125 MHz, CDCl3): 28.5 (CH3),
38.2 (C), 39.6 (CH2), 122.0, 126.1, 127.1, 127.8, 129.3, 129.6,
136.3, 148.3, 159.5, 165.5, 169.8 (ArAC); MS (EI, 70 eV) m/z (%):
450 [M]+, 393, 337, 225, 169, 143 (100%), 128, 57. Anal. Calcd.
For C30H34N4: C, 79.96; H, 7.60; N, 12.43. Found: C, 79.46; H,
7.41; N, 12.30.
C6H4).
2.9. (Z)-2-(2-Hydrazono-3,3-dimethylbutyl)quinoline (2d)
White needles; mp 105–107 °C; IR (KBr)
m: 3320, 3205, 1640,
1620, 1595 cmꢀ1 1H NMR (500 MHz, CDCl3): d 1.1 (s, 9H, CH3),
;
4.0 (s, 2H, CH2), 6.2 (broad, 2H, NH2), 7.0–8.2 (m, 6H, C9H6N).
2.5. General procedure for synthesis of 2-ketomethylquinolinehyd
razones (2a–2d)
2.10. General procedure for synthesis of unsymmetrical 2-ketomethyl
quinolineazines
2-Ketomethylquinoline (1.0 mmol) was dissolved in the mini-
mum amount of ethanol and a drop of acetic acid and hydrazine
monohydrate (2.0 mmol) was added. The mixture was stirred vig-
orously at 80 °C for about 6 h. Progress of the reaction was fol-
lowed by TLC (eluent:ethyl acetate/petroleum ether, 1:5). After
completion of reaction the mixture was cooled and the solid
formed separated by filtration. The crude product was purified by
crystallization from ethanol.
2-Ketomethylquinolinehydrazone (2.0 mmol) was dissolved in
the minimum amount of ethanol and a drop of acetic acid and alde-
hyde or ketone (2.0 mmol) was added. The mixture was stirred vig-
orously at 80 °C for the appropriate times (Table 1). Progress of the
reaction was followed by TLC (eluent:ethyl acetate/petroleum
ether, 1:5). After completion of reaction the mixture was cooled
and the solid formed separated by filtration. The crude product
was purified by crystallization from ethanol.
1, PhLi,ether, N2
2, R1CN
CH3
1, NH2NH2,H2O
2, AcOH, EtOH
But
N N
But
N
N
H
N
R1
3a-A
N
HN
1a, R1= But 1b, R1= Ph
Scheme 2. Synthesis of symmetrical azine.

140
H. Loghmani-Khouzani et al. / Journal of Molecular Structure 1032 (2013) 138–146
Table 1
The 2-ketomethylquinolineazines synthesized in this work.
R1
R2
N N R3
N
N
H
N
H
R1
R2
R3
R1
R2
R3
N
N
N
N
3-A
3-B
3-C
Com.
R1
R2
R3
mp (ꢀC)
Reaction times (min)
Yield (%)
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
t-Bu
Ph
p-MePh
Ph
P-MePh
Ph
p-MePh
t-Bu
p-MePh
Ph
t-Bu
Ph
P-MePh
Ph
p-MePh
t-Bu
Ph
p-MePh
t-Bu
t-Bu
Me
Me
H
H
H
H
H
Me
Me
Me
H
H
H
H
H
H
H
H
CH2(2-Qa)
Ph
Ph
Ph
Ph
174–176
148–150
133–135
127–129
160–162
186–188
187–189
163–165
131–133
160–162
113–115
138–140
193–195
201–203
184–186
155–157
162–164
167–169
129–131
360
360
360
360
360
30
70
75
75
75
75
90
90
90
85
85
80
85
85
90
90
90
90
90
90
p-NO2Ph
p-NO2Ph
p-NO2Ph
p-BrPh
p-BrPh
p-BrPh
p-ClPh
p-ClPh
o-NO2Ph
o-NO2Ph
o-NO2Ph
m-NO2Ph
m-NO2Ph
m-NO2Ph
30
30
300
300
300
300
300
300
30
30
30
30
30
a
Quinolinyl.
2.11. 2-((Z)-2-Phenyl-2-((Z)-2-(1-phenyllidene)hydrazinyl)vinyl)
quinoline (3b)
(125 MHz, CDCl3): 39.4 (CH2), 97.0 (CH), 121.5, 126.4, 126.9,
127.9, 128.1, 128.3, 128.8, 128.9, 129.1, 129.2, 129.3, 129.9,
130.7, 131.3, 134.9, 137.1, 137.5, 148.3, 148.7, 160.7, 165.6 (ArAC);
MS (EI, 70 eV) m/z (%): 349 [M]+, 245, 230, 221, 169, 156, 143
(100%), 129, 104, 91, 77, 51. Anal. Calcd. For C24H19N3: C, 81.49;
H, 5.48; N, 12.02. Found: C, 81.65; H, 5.48; N, 11.69.
White needles; mp 148–150 °C; UV (nm) in chloroform; 433,
300, 300; IR (KBr)
m ;
: 3250, 1620, 1595, 1550, 1505 cmꢀ1 1H
NMR (500 MHz, CDCl3): d 2.64 (s, 3H, CH3), 5.55 (s, 1H, CH),
7.16–7.92 (m, 16H, ArAH), 13.94 (s, 1H, NH). 13C NMR (125 MHz,
CDCl3): 14.3 (CH3), 98.7 (CH), 123.1, 124.5, 125.2, 125.7, 125.9,
126.8, 126.9, 127.7, 127.8, 128.1, 128.4, 128.5, 128.5, 129.6,
129.7136.8, 138.9, 143.9, 147.1, 153.1158.3, 158.9 (ArAC); MS
(EI, 70 eV) m/z (%): 363 [M]+, 348, 245, 230, 221, 169, 156, 143,
128, 118, 103, 91, 77 (100%), 57. Anal. Calcd. For C25H21N3: C,
81.61; H, 5.82; N, 11.56. Found: C, 81.11; H, 5.84; N, 11.30.
2.14. 2-((Z)-2((Z)-2-Benzylidenhydrazinyl)-2-p-tolylvinyl)quinoline
(3e)
White needles; mp 160–162 °C; UV (nm) in chloroform; 431,
303; IR (KBr)
m ;
: 3200, 1622, 1590, 1540, 1500 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 2.37 (s, 1.5H, CH3), 2.48 (s, 1.5H, CH3), 4.99
(s, 1.0H, CH2), 5.55 (s, 0.5H, CH), 7.15–8.20 (m, 15H, ArAH),
14.55 (s, 0.5H, NH). 13C NMR (125 MHz, CDCl3): 21.8 (CH3), 21.9
(CH3), 39.2 (CH2), 97.8 (CH), 121.5, 122.2, 124.8, 126.9, 127.3,
127.9, 128.2, 128.8, 129.0, 129.6, 129.8, 129.9, 131.4, 135.6,
137.0, 140.9, 147.4, 148.4, 158.9, 160.4, 165.6 (ArAC); MS (EI,
70 eV) m/z (%): 363 [M]+, 285, 259, 245,169,156,143 (100%), 118,
104, 91, 77, 44. Anal. Calcd. For C25H21N3: C, 82.61; H, 5.82; N,
1156. Found: C, 82.34; H, 5.82; N, 11.46.
2.12. 2-((Z)-2-((Z)-2-(1-Phenylethylidene)hydrazniyl)-2-p-tolylvinyl)
quinoline (3c)
White needles; mp 133–135 °C; UV (nm) in chloroform; 437,
300; IR (KBr)
m ;
: 3300, 1620, 1590, 1550, 1500 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 2.29 (s, 1H, CH3, tautomer B), 2.33(s, 2H,
CH3, tautomer A), 2.42 (s, 1H, CH3, tautomer B), 2.64 (s, 2H, CH3,
tautomer A), 4.71 (s, 1.2H, CH2), 5.55 (s, 0.4H, CH), 7.15–8.00 (m,
15H, ArAH), 13.94 (broad, 0.4H, NH)7. 13C NMR (125 MHz, CDCl3):
14.0 (CH3), 15.8 (CH3), 21.5 (CH3), 21.7 (CH3), 38.9 (CH2), 98.4 (CH),
121.2, 123.0, 125.9, 126.7, 126.8, 126.9, 127.4, 127.6, 128.0, 128.4,
129.2, 129.5, 129.7, 134.3, 138.4, 139.0, 140.1, 153.2, 158.5, 158.9,
159.0 (ArAC); MS (EI, 70 eV) m/z (%): 377 [M]+, 362, 244, 235, 169,
156, 143, 128, 104, 77, 44 (100%). Anal. Calcd. For C26H23N3: C,
82.27; H, 6.14; N, 11.13. Found: C, 82.31; H, 6.12; N, 11.14.
2.15. 2-((Z)-2((Z)-4-Nitrobenzylidene)hydrazinyl)-2-phenyvinyl)
quinoline (3f)
White needles; mp 186–188 °C; UV (nm) in chloroform; 449,
385, 303, 265.5; IR (KBr)
m ;
: 3200, 1622, 1590, 1540, 1505 cmꢀ1
1H NMR (500 MHz, CDCl3): d 4.92 (s, 0.3H, CH2), 5.64 (s, 0.7H,
CH), 7.22–8.20 (m, 15H, ArAH), 14.76 (s, 0.7H, NH). 13C NMR
(125 MHz, CDCl3): 39.0 (CH2), 100.2 (CH), 123.3, 124.4, 125.9,
126.9, 127.4, 128.0, 128.2, 128.9, 129.3, 129.4, 129.7, 130.1,
136.2, 136.3, 137.3, 142.2, 147.2, 147.5, 158.5, 165.0 (ArAC); MS
(EI, 70 eV) m/z (%): 394 [M]+, 245, 230, 169, 149, 143 (100%), 129,
104, 77, 57, 44. Anal. Calcd. For C24H18N4O2: C, 73.08; H, 4.16; N,
14.20. Found: C, 72.70; H, 4.62; N, 14.17.
2.13. 2-((Z)-2((Z)-2-Benzylidenhydrazinyl)-2-phenylvinyl)quinoline
(3d)
White needles; mp 127–129 °C; UV (nm) in chloroform; 431,
303; IR (KBr)
m ;
: 3200, 1622, 1590, 1560, 1540, 1500 cmꢀ1 1H
NMR (500 MHz, CDCl3): d 5.02 (s, 1.4H, CH2), 5.55 (s, 0.2H, CH),
7.18–8.20 (m, 17H, ArAH), 14.95 (s, 0.2H, NH). 13C NMR

H. Loghmani-Khouzani et al. / Journal of Molecular Structure 1032 (2013) 138–146
141
2.16. 2-((Z)-2((Z)-4-Nitrobenzylidene)hydrazinyl)-2-p-tolylyvinyl)
quinoline (3g)
1.3H, CH3), 2.32(s, 1.7H, CH3), 4.19 (s, 0.8H, CH2), 5.52 (s, 0.6H,
CH), 7.20–8.05 (m, 10H, ArAH), 15.18 (s, 0.6H, NH). 13C NMR
(125 MHz, CDCl3): 15.2 (CH3), 15.3 (CH3), 28.9 (CH3), 30.1(CH3),
36.7 (C), 38.6 (C), 39.7 (CH2), 94.0 (CH), 120.1, 123.8, 124.3,
127.4, 128.5, 159.2, 165.8 (ArAC); MS (EI, 70 eV) m/z (%): 374
[M]+, 246, 225, 169, 149, 156, 143 (100%), 103, 76, 69, 57, 44. Anal.
Calcd. For C22H22N4 O2: C, 71.06; H, 5.83; N, 14.38. Found: C, 70.57;
H, 5.92; N, 14.96.
White needles; mp 187–189 °C; UV (nm) in chloroform; 451,
386, 312, 300, 266; IR (KBr)
m: 3200, 1622, 1590, 1540,
1505 cmꢀ1 1H NMR (500 MHz, CDCl3): d 2.37 (s, 0.75H, CH3),
;
2.49 (s, 2.25H, CH3), 4.92 (s, 0.4H, CH2), 5.55 (s, 0.8H, CH), 7.20–
8.25 (m, 14H, ArAH), 14.78 (s, 0.8H, NH). 13C NMR (125 MHz,
CDCl3): 19.9 (CH3), 21.8 (CH3), 39.4 (CH2), 99.6 (CH), 121.2,
123.3, 124.4, 125.3, 126.9, 127.4, 128.0, 128.4, 128.9, 129.4,
129.6, 130.1, 133.4, 136.1, 137.2, 139.3, 142.3, 147.5, 152.4,
157.3, 158.5 (ArAC); MS (EI, 70 eV) m/z (%): 408 [M]+, 244, 149,
156, 143 (100%), 129, 118, 91. Anal. Calcd. For C25H20N4 O2: C,
73.51; H, 4.94; N, 13.72. Found: C, 73.05; H, 4.98; N, 13.65.
2.21. 2-((Z)-2-((E)-(4-Cholorobenzylidene)hydrazono)-2-phenylethyl)
quinoline (3l)
White needles; mp 138–140 °C; UV (nm) in chloroform; 311,
303; IR (KBr)
m ;
: 1615, 1595, 1560, 1530, 1500 cmꢀ1 1H NMR
2.17. 2-((Z)-3,3-Dimethyl-2-((Z)-2-(4-nitrobenzylidene)hydrazinyl)
but-1-enyl)quinoline (3h)
(500 MHz, CDCl3): d 4.99 (s, 2H, CH2), 7.30–8.17 (m, 15H, ArAH).
13C NMR (125 MHz, CDCl3): 39.4 (CH2), 121.4, 126.4, 127.2,
127.9, 128.3, 128.9, 129.4, 129.5, 129.9, 130.1, 130.8, 133.4,
137.1, 137.4, 138.5, 158.6, 159.2, 165.8 (ArAC); MS (EI, 70 eV) m/
z (%): 385 [M + 2]+, 383 [M]+, 245, 230, 169, 143 (100%), 104, 77,
51. Anal. Calcd. For C24H18N3 Cl: C, 75.01; H, 4.73; N, 10.95. Found:
C, 74.96; H, 4.75; N, 10.92.
White needles; mp 163–165 °C; UV (nm) in chloroform; 460,
382, 361, 310; IR (KBr) m ;
: 3200, 1625, 1595, 1520 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 1.31 (s, 6H, CH3), 1.56 (s, 3H, CH3), 4.36 (s,
1.4H, CH2), 5.52 (s, 0.3H, CH), 7.20–8.35 (m, 10H, ArAH), 15.18
(s, 0.3H, NH). 13C NMR (125 MHz, CDCl3): 28.2 (CH3), 29.4 (CH3),
38.1 (C) 39.0 (CH2), 94.0 (CH), 120.1, 123.8, 124.3, 127.4, 128.5
(ArAC); MS (EI, 70 eV) m/z (%): 374 [M]+, 246, 225, 169, 158, 157,
156, 149, 143 (100%), 103, 76, 69, 57, 44. Anal. Calcd. For
2.22. 2-((Z)-2-((E)-(4-Cholorobenzylidene)hydrazono)-2-p-tolylethyl)
quinoline (3m)
C22H22N4 O2: C, 71.06; H, 5.83; N, 14.38. Found: C, 70.57; H,
5.92; N, 14.96.
White needles; mp 194–196 °C; UV (nm) in chloroform; 313,
300; IR (KBr)
m: ;
1622, 1585, 1570, 1550 cmꢀ1 1H NMR
2.18. 2-((Z)-2((Z)-2-(1-Bromophenyl)ethylidene)hydrazinyl)-2-
phenylvinyl)quinoline (3i)
(500 MHz, CDCl3): d 2.36 (s, 3H, CH3), 4.93 (s, 2H, CH2), 7.20–8.10
(m, 14H, ArAH). 13C NMR (125 MHz, CDCl3): 21.8 (CH3), 39.4
(CH2), 121.4, 126.4, 127.2, 127.9, 128.3, 128.9, 129.4, 129.5,
129.9, 130.1, 130.8, 133.4, 137.1, 137.4, 138.5, 158.9, 159.2, 165.8
(ArAC); MS (EI, 70 eV) m/z (%): 399 [M + 2]+, 397 [M]+, 169, 143
(100%), 115, 69, 44. Anal. Calcd. For C25H20N3 Cl: C, 75.46; H,
5.07; N, 10.56. Found: C, 75.96; H, 4.95; N, 10.95.
White needles; mp 131–133 °C; UV (nm) in chloroform; 434,
300; IR (KBr)
m ;
: 3300, 1630, 1595, 1570, 1560 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 2.36 (s, 2H, CH3), 2.65 (s, 1H, CH3), 4.72 (s,
1.4H, CH2), 5.63 (s, 0.3H, CH), 7.27–8.13 (m, 15H, ArAH), 14.08
(broad, 0.3H, NH). 13C NMR (125 MHz, CDCl3): 14.3(CH3), 15.7
(CH3), 39.5 (CH2), 99.4 (CH), 121.5, 126.4, 127.2, 127.6, 127.9,
128.0, 128.1, 128.7, 129.3, 129.9, 130.3, 131.8, 131.9, 136.9,
147.4, 148.4, 158.5, 159.6, 159.7 (ArAC); MS (EI, 70 eV) m/z (%):
443 [M]+, 441, 301, 299, 245, 230, 198, 196, 157, 156, 143
(100%), 103, 77, 51, 44. Anal. Calcd. For C25H20N3Br: C, 67.88; H,
4.56; N, 9.5. Found: C, 67.46; H, 6.64; N, 9.43.
2.23. 2-((Z)-2-((Z)-2-(2-(4-Nitrobenzylidene)hydrazinyl)-2-phenylvi
nyl)quinoline (3n)
White needles; mp 201–203 °C; UV (nm) in chloroform; 440,
401, 303; IR (KBr)
m ;
: 3300, 1622, 1590, 1570, 1540, 1510 cmꢀ1
1H NMR (500 MHz, CDCl3): d 4.90 (s, 0.14H, CH2), 5.60 (s, 0.93H,
CH), 7.21–8.70 (m, 15H, ArAH), 14.84 (s, 0.93H, NH). 13C NMR
(125 MHz, CDCl3): 39.0 (CH2), 100.0 (CH), 123.1, 125.2, 125.5,
125.8, 127.6, 127.8, 128.1, 128.7, 129.1, 129.7, 130.3, 130.9,
133.4, 135,4, 136.1, 136.6, 147.2, 147.6, 152.4, 158.4 (ArAC); MS
(EI, 70 eV) m/z (%): 394 [M]+, 348, 225, 169, 156, 143 (100%), 103,
46. Anal. Calcd. For C24H18N4 O2: C, 73.08; H, 4.60; N, 14.10. Found:
C, 73.32; H, 4.95; N, 13.58.
2.19. 2-((Z)-2((Z)-2-(1-Bromophenyl)ethylidene)hydrazinyl)-2-
p-tolylvinyl)quinoline (3j)
White needles; mp 160–162 °C; UV (nm) in chloroform; 437,
300; IR (KBr)
m ;
: 3300, 1625, 1590, 1540, 1500 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 2.37 (s, 2H, CH3), 2.38 (s, 1H, CH3), 2.48 (s,
2H, CH3), 2.59 (s, 1H, CH3), 4.72 (s, 1.4H, CH2), 5.62 (s, 0.3H, CH),
7.22–8.0 (m, 14H, ArAH), 14.08 (broad, 0.3H, NH). 13C NMR
(125 MHz, CDCl3): 14.9 (CH3), 15.7 (CH3), 20.0 (CH3), 22.1 (CH3),
39.0 (CH2), 98.0 (CH), 121.48, 126.4, 127.2, 127.6, 127.9, 128.0,
128.1, 128.7, 129.3, 129.8, 130.3, 131.8, 131.9, 136.9, 147.4,
148.4, 158.5, 159.6, 159.7, 160.1, 167.5, 169.7 (ArAC); MS (EI,
70 eV) m/z (%): 457 [M]+, 455, 315, 313, 198, 196, 157, 156, 155,
143 (100%), 44. Anal. Calcd. For C26H22N3Br: C, 68.43; H, 4.86; N,
9.21. Found: C, 68.49; H, 4.19; N, 9.20.
2.24. 2-((Z)-2-((Z)-2-(4-Nitrobenzylidene)hydrazinyl)-2-p- tolylvinyl)
quinoline (3o)
White needles; mp 184–186 °C; UV (nm) in chloroform; 438,
303; IR (KBr)
m ;
: 3300, 1625, 1590, 1570, 1540, 1510 cmꢀ1 1H
NMR (500 MHz, CDCl3): d 2.37(s, 0.45H, CH3), 2.48 (s, 2.55H,
CH3), 4.90 (s, 0.28H, CH2), 5.60 (s, 0.86H, CH), 7.10–8.20 (m, 14H,
ArAH), 14.87 (s, 0.86H, NH). 13C NMR (125 MHz, CDCl3): 21.8
(CH3), 39.0 (CH2), 99.7 (CH), 123.1, 125.2, 125.4, 127.6, 127.8,
128.2, 128.6, 128.9, 129.6, 130.3, 133.4, 136.1, 136.8, 152.2,
158.6. (ArAC); MS (EI, 70 eV) m/z (%): 408 [M]+, 362, 225, 169,
156, 143 (100%), 103, 46. Anal. Calcd. For C24H18N4 O2: C, 73.51;
H, 4.94; N, 13.72. Found: C, 72.91; H, 4.72; N, 14.17.
2.20. 2-((Z)-2-((Z)-2-(1-(4-Bromophenyl)ethylidene)hydrazinyl)-3,3-
dimethylbut-1-enyl)quinoline (3k)
White needles; mp 113–115 °C; UV (nm) in chloroform; 442,
335, 323, 300; IR (KBr)
m ;
: 3200, 1630, 1600, 1540 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 1.31 (s, 4H, CH3), 1.61(s, 5H, CH3), 2.19 (s,

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H. Loghmani-Khouzani et al. / Journal of Molecular Structure 1032 (2013) 138–146
2.25. 2-((Z)-3,3-Dimethyl-2-((Z)-2-(2-nitrobenzylidene)hydrazinyl)
but-1-enyl)quinoline (3p)
0.7H, CH2), 5.60 (s, 0.65H, CH), 7.20–8.35 (m, 14H, ArAH), 14.72
(s, 0.65H, NH). 13C NMR (125 MHz, CDCl3): 21.8 (CH3), 39.5
(CH2), 99.0 (CH), 121.7, 123.1, 123.2, 125.2, 127.3, 128.9, 129.6,
130.1, 135.9, 137.4, 154.2, 158.4, 165.2 (ArAC); MS (EI, 70 eV) m/
z (%): 408 [M]+, 259, 244, 169, 150, 149, 143 (100%), 128, 91, 76,
44. Anal. Calcd. For C25H20N4 O2: C, 73.51; H, 4.94; N, 13.72. Found:
C, 72.98; H, 5.02; N, 13.54.
White needles; mp 155–157 °C; UV (nm) in chloroform; 450,
400, 312, 300; IR (KBr) m ;
: 3300, 1625, 1595, 1570, 1510 cmꢀ1 1H
NMR (500 MHz, CDCl3): d 1.30 (s, 1.8H, CH3), 1.56 (s, 7.2H, CH3),
4.38 (s, 0.4H, CH2), 5.50 (s, 0.8H, CH), 7.16–8.30 (m, 10H, ArAH),
15.3(s, 0.8H, NH). 13C NMR (125 MHz, CDCl3): 28.7 (CH3), 29.9
(CH3), 36.5 (C) 38.9 (C), 39.5 (CH2), 94.8 (CH), 121.3, 123.6, 124.8,
125.2, 125.5, 126.3, 127.4, 127.5, 127.7, 128.3, 130.2, 1314, 133.4,
133.8, 135.8, 147.5, 152.8, 158.6, 158.8, 159.7 (ArAC); MS (EI,
70 eV) m/z (%): 374 [M]+, 335, 285, 196, 169, 156, 143 (100%),
128, 91, 77, 51. Anal. Calcd. For C22H22N4 O2: C, 70.57; H, 5.92; N,
14.96. Found: C, 70.17; H, 5.64; N, 14.49.
2.28. 2-((Z)-3,3-Dimethyl-2-((Z)-2-(3-nitrobenzylidene)hydrazinyl)
but-1-enyl)quinoline (3s)
White needles; mp 129–131 °C; UV (nm) in chloroform; 430,
317, 281; IR (KBr)
m: 3300, 1630, 1600, 1580, 1570, 1550,
1515 cmꢀ1 1H NMR (500 MHz, CDCl3): d 1.34 (s, 3H, CH3), 1.57
;
(s, 6H, CH3), 4.37 (s, 0.66H, CH2), 5.47 (s, 0.67H, CH), 7.10–8.40
(m, 10H, ArAH), 15.10 (broad, 0.67H, NH). 13C NMR (125 MHz,
CDCl3): 28.7 (CH3), 29.9 (CH3), 36.6 (C), 38.9 (C), 39.7 (CH2), 94.2
(CH), 121.3, 121.5, 122.8, 123.9, 125.1, 126.3, 127.3, 127.8, 127.9,
129.3, 129.9, 131.5, 133.7, 133.8, 135.8, 136.6, 147.0, 154.8,
158.9, 160.0, 175.5 (ArAC); MS (EI, 70 eV) m/z (%): 374 [M]+, 226,
225, 169, 149, 143 (100%), 128, 57. Anal. Calcd. For C22H22N4 O2:
C, 70.57; H, 5.92; N, 14.97. Found: C, 70.03; H, 5.90; N, 14.97.
2.26. 2-((Z)-2-((Z)-2-(3-Nitrobenzylidene)hydrazinyl)-2-phenylvinyl)
quinoline (3q)
White needles; mp 162–164 °C; UV (nm) in chloroform; 425,
300; IR (KBr)
m ;
: 3300, 1622, 1580, 1560, 1540 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 4.93 (s, 0.26H, CH2), 5.60 (s, 0.87H, CH),
7.20–8.32 (m, 15H, ArAH), 14.70 (broad, 0.87H, NH). 13C NMR
(125 MHz, CDCl3): 39.0 (CH2), 99.5 (CH), 121.7, 123.1, 123.2,
125.3, 125.8, 127.4, 128.0, 128.2, 129.2, 129.7, 129.8, 130.1,
131.8, 136.1, 137.4, 158.5. (ArAC); MS (EI, 70 eV) m/z (%): 394
[M]+, 245, 230, 169, 149, 143 (100%), 104, 77, 44. Anal. Calcd. For
C24H18N4 O2: C, 73.08; H, 4.60; N, 13.20. Found: C, 72.64; H,
4.66; N, 14.06.
3. Results and discussion
New azines studied in the present paper have been synthesized
in three steps. At first, a series of 2-ketomethylquinolines have
been prepared using literature methods.[8] Tautomerism in this
group of compounds have been well worked out by several inves-
tigators.[9,10] In the next step 2-ketomethylquinolines in reaction
with hydrazine in ethanol solution and a drop of acetic acid as a
catalyst were converted to 2-ketomethylquinolinehydrazones
(2a–2d) in good to high yields (70–95%). Four of these intermedi-
ates (Scheme 1, R1 = Ph, p-MeC6H4, p-MeOC6H4, But) were isolated
and their structures have been determined by spectroscopic
2.27. 2-((Z)-2-((Z)-2-(3-Nitrobenzylidene)hydrazinyl)-2-p-
tolylylvinyl)quinoline (3r)
White needles; mp 167–169 °C; UV (nm) in chloroform; 427,
303; IR (KBr)
m ;
: 3250, 1622, 1580, 1560, 1540 cmꢀ1 1H NMR
(500 MHz, CDCl3): d 2.38 (s, 1H, CH3), 2.50 (s, 2H, CH3), 4.96 (s,
Table 2
Some 1H and 13C NMR, UV and IR, data of 2-ketomethylquinolineazines.
Comp.
1H NMR (CDCl3) (ppm)
13C NMR (CDCl3) (ppm)
IR (cmꢀ1, KBr disk)
UV (nm, in ethanol)
A:B ratio in CDCl3
kmax
CH
CH2
NH
CH
CH2
C@C
N@C
NAHa
C@C
C@N
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
–
4.27
–
–
–
39.6
–
165.5
158.3
158.9
160.7
160.4
158.5
157.3
157.0
159.6
167.5
160.6
159.2
158.9
158.4
158.6
158.8
158.5
162.0
160.0
169.8
158.9
159.0
165.6
165.6
165.0
158.5
158.0
159.7
169.7
168.8
165.8
165.8
–
–
1590
1595
1590
1590
1590
1590
1590
1595
1595
1590
1600
1595
1585
1590
1590
1595
1580
1580
1600
1615
1620
1620
1622
1622
1622
1622
1625
1615
1625
1630
1615
1622
1622
1625
1625
1622
1622
1630
317
433
437
431
449
449
451
460
434
437
442
311
313
440
438
450
425
427
430
100:0
0:100
66:34
79:21
50:50
35:65
20:80
67:33
63:37
72:28
40:60
100:0
100:0
7:93
5.55
5.55
5.55
5.55
5.64
5.55
5.52
5.63
5.62
5.52
–
13.94
13.94
14.95a
14.55
14.76
14.78
15.18
14.08
14.08
14.08
–
98.7
98.4
97.0
97.8
100.2
99.6
94.0
99.4
98.0
94.0
–
3250
3300
3300
3200
3200
3200
3200
3300
3300
3300
–
4.71
5.02
4.99
4.92
4.92
4.36
4.72
4.72
4.19
4.99
4.93
4.90
4.90
4.38
4.93
4.90
4.37
38.9
39.4
39.2
39.0
39.4
39.0
39.5
39.0
39.7
39.4
39.4
–
–
–
–
–
5.60
5.60
5.50
5.60
5.60
5.47
14.84a
14.87
15.33
14.70
14.84
15.10
100.0
99.7
94.8
99.5
99.0
94.2
3300
3300
3300
3300
3250
3300
b
b
–
–
15:85
19:81
13:87
24:76
40:60
38.9
39.0
39.5
39.7
159.7
–
165.2
175.5
a
Broad.
b
Not appeared due to low concentration.

H. Loghmani-Khouzani et al. / Journal of Molecular Structure 1032 (2013) 138–146
143
the presence a drop of acetic acid (as a catalyst) to give unsymmet-
rical azines (Scheme 1). The reaction, completion time, yield and
structure of the compounds are given in Table 1.
For comparison, a symmetrical azine was also prepared via a
different route as shown in Scheme 2.
Following our previous work [11], we focused on the structure
of a new series of 2-ketomethylquinolineazines, particular by
focusing on identification of their tautomers.
H
N
C4-H
C3-H
H
H
H
O
R
N
H
R
O
A (Ketone form)
B (Enaminone form)
UV, IR and NMR spectroscopy were used to determine the struc-
ture of the compounds. It was found that this group of compounds
could be classified into three main categories, based on their tauto-
meric forms. Thus, in chloroform solution compounds 3a, 3l and
3m are exclusively in the form 3-A. On the other hand, compound
3b exist entirely in the form 3-B. Finally derivatives 3c–3k and 3n–
3s were found to exist as mixtures of both forms ð3-A¡3-BÞ. The
concentration ratio of the two tautomers at equilibrium, A:B (in
chloroform solutions) are reported in Table 2.
Typical cis-s-cis enaminone C@O and C@C vibrations (KBr disc)
for 2-ketomethyquinolines at 1632 and 1585 cmꢀ1 have been ear-
lier reported [8].
The infrared data of 2-ketomethylquinolineazines reported in
Table 2 show that in the solid state all the compounds were found
to be exclusively in the 3-B or 3-C forms. Most of the entries in Ta-
ble 2 (except 3a, 3l and 3m) show a band around 1620 cmꢀ1 for the
C@N stretching vibration. Moreover, spectra of these compounds
show a broad band around 3300 cmꢀ1 for the NAH stretching
Scheme 3. Tautomeric forms for 2-ketomethylquinolines.
methods. Infrared spectra of these compounds (KBr discs) show
strong absorption bands around 3360 and 3130 cmꢀ1 for ANH2
of primary amines. The compounds also show a strong absorption
around 1645–1630 cmꢀ1 for C@N vibrations.
The 1H NMR data of these compounds (in chloroform solution)
show a broad line at 6.2–6.5 ppm for the ANH2 and another singlet
(CH2) in the aliphatic region around 4.0–4.8 ppm. Integrations of
these signals confirm there are two protons present in each group.
There was no signal around 14.0 ppm corresponding to possible
enamine-imine form 2-B (Scheme 1). From these observations
we conclude that the 2-ketomethylquinolinehydrazones exist
exclusively in the imine form 2-A (Scheme 1).
In the third step 2-ketomethylquinolinehydrazones were trea-
ted with different aldehyde and ketone in ethanol solution and in
Fig. 1. 1H NMR spectrum of compound 3b in deuterochlorform solution.

144
H. Loghmani-Khouzani et al. / Journal of Molecular Structure 1032 (2013) 138–146
Fig. 2. 1H NMR spectrum of compound 3g in deuterochloroform solution.
mode. These data correspond to those of the similar azines have
been earlier reported.[12] Position of the low field NAH signal in
the 1H NMR spectra is expected to be a measure of the strength
of the intramolecular hydrogen bonding.
The IR spectra confirm that in the solid state, the compounds
are exclusively in the conjugated forms 3-B or 3-C.
Typical absorption UV band kmax (nm) in ethanol for 2-ketom-
ethylquinolines (R = Ph) has been observed at 459 nm.[13] The
UV spectral absorption data of the azines in chloroform solution
are given in Table 2. These data show two types of absorption
bands. For compounds 3a, 3l and 3m, these absorption bands are
located at 317, 311 and 313 nm, respectively (conjugation does
not extend on the side and quinoline ring). Thus, only the form
3-A is present there. On the other hand, in the spectra of the other
compounds studied, these absorption bands are observed around
425–460 nm which show that conjugation between the side chain
and quinoline ring does take place, so they may be in the form 3-B
or 3-C.
Moreover, existence of the forms 3-B or 3-C is proved by the
NAH signal at d 13.94 which arises as a result of strong intramolec-
ular hydrogen bonding between NAH proton and nitrogen in both
forms. Tautomeric forms were also observed for the other 3c–3k
and 3n–3s compounds. Tautomeric ratios were calculated for these
compounds from the relative integrals of the signals of vinylic pro-
ton and methylene protons. These compounds also revealed broad
downfield signals due to the NAH proton around d 13.94–15.33 of
the conjugated form 3-B or 3-C. It should be mentioned that the
two doublets in the 6.7–7.9 and 7.6–8.1 ppm regions (C3AH and
C4AH protons of the quinoline ring, respectively) exist exclusively
in the enaminone form (B). The assignments of these doublets have
already been reported by Mondelli and Merllini [9] (Scheme 3).
However, for all azines which may have tautomeric forms (Scheme
2), these doublets did not appear. From these observations, we
concluded that the compounds exist exclusively in the form 3-B.
Obviously, substitution has effect on tautomeric ratio, but due to
the limited number of samples we cannot draw a definite final con-
clusion. For comparison, 1H NMR spectra of each category (3b, 3g
and 3l) are presented in Figs. 1–3.
The 1H NMR data of the azines studied are presented in Table 2.
Typical 1H NMR lines of the CH2 and CH groups of the correspond-
ing 2-ketomethylquinolines in chloroform solution have been re-
ported at d 4.04–4.75 ppm.[8] These 1H NMR data of the azines
are presented in Table 2. These 1H NMR data for compounds 3a,
3l and 3m in chloroform show a singlet at d 4.27, 4.99 and
4.93 ppm, respectively. Integration of these signals was exactly
proportional to two protons and there was no other signal for
the vinylic proton and the NAH proton due to the formation of
the second tautomeric forms 3-B or 3-C. There is a singlet corre-
sponding to the vinylic proton at d 5.55 in which this signal inte-
grated to one proton only, the methylene protons is missing.
Some important 13C NMR chemical shifts of the compounds
studied are given in Table 2. These data show that there are sig-
nals around 38.8–39.7 and 94.0–100.0 ppm for the methylene and
vinylic carbons, respectively. Low field signal at 158.9 ppm in the
spectrum of compound 3b which is found to be exclusively in the
form B can be assigned to the quaternary carbon C@N. Moreover,
the signal near 98.7 ppm can be attributed to the vinylic carbon
atom. Since, no signal is detected around 38 ppm for the second
tautomeric forms. Signals of the methylene carbons in the spectra
of compounds 3a, 3l and 3m were observed at 39.5 ppm. None of

H. Loghmani-Khouzani et al. / Journal of Molecular Structure 1032 (2013) 138–146
145
Fig. 3. 1H NMR spectrum of compound 3l in deuterochloroform solution.
the spectra for these compounds show the signal for the vinylic
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