Reactions of 9-alkyl-3-aminocarbazoles with Ethyl-3-oxobutanoate and Identification of the Products Obtained

Article abstract of DOI:10.3390/11010072

The reactions in benzene of 9-alkyl-3-aminocarbazoles with ethyl-3-oxobutanoate yielded ethyl-3-[(9-alkyl-9H-carbazol-3-yl)amino]but-2- enoate condensation products or N-(9-ethyl-9H-carbazol-3-yl)-3-oxobutanamide acylation products. The condensation products were cyclized to the corresponding 4,7-dihydro-pyrido[2,3-c]-carbazol-1-ones upon heating in mineral oil at 240-250 °C. The structures of the synthesized compounds were investigated by IR, mass spectrometry, ¹H- and ¹³C-NMR spectroscopy and MM2 molecular mechanics and AM1 semi-empirical quantum mechanical methods.

Full text of DOI:10.3390/11010072

Molecules 2006, 11, 72–80
molecules
ISSN 1420-3049
http://www.mdpi.org
Reactions of 9-Alkyl-3-aminocarbazoles with Ethyl-3-oxo-
butanoate and Identification of the Products Obtained
Birute Sapijanskaite 1, Vytautas Mickevicius 1,† and Gema Mikulskiene 2,*
1
Department of Organic Chemistry, Kaunas University of Technology, Radvilenu pl. 19, LT-50254
Kaunas, Lithuania, Tel.: (+370) 37 456 561, Fax: (+370) 37 300 152, † E-mail:
vytautas.mickevicius@ktu.lt
2
Institute of Biochemistry, LT-08662 Vilnius, Mokslininku 12, Lithuania, Tel.: (+370) 5 272 9195,
Fax: (+370) 5 272 9196
*Author to whom correspondence should be addressed; E-mail: gemam@bchi.lt
Received: 17 March 2005; in revised form: 19 October 2005 / Accepted: 20 October 2005 / Published:
31 January 2006
Abstract: The reactions in benzene of 9-alkyl-3-aminocarbazoles with ethyl-3-oxobutanoate
yielded ethyl-3-[(9-alkyl-9H-carbazol-3-yl)amino]but-2-enoate condensation products or N-
(9-ethyl-9H-carbazol-3-yl)-3-oxobutanamide acylation products. The condensation products
were cyclized to the corresponding 4,7-dihydro-pyrido[2,3-c]-carbazol-1-ones upon heating
in mineral oil at 240-250 °C. The structures of the synthesized compounds were investigated
1
13
by IR, mass spectrometry, H- and C-NMR spectroscopy and MM2 molecular mechanics
and AM1 semi-empirical quantum mechanical methods.
Keywords: Condensation, intramolecular cyclization, substituted pyrido[2,3-c]carbazol-1-
ones, NMR spectra, molecular modeling.
Introduction
We have chosen to study the synthesis of carbazole ring-containing amino acids and their
derivatives for two main reasons: carbazole fragments are present in the structure of some alkaloids [1-
3] and carbazole ring-containing compounds usually exhibit semiconductor properties and are used in
electrography [4,5]. It was also expected that their combination with amino acid fragments would
enable the synthesis of new biologically active substances.

Molecules 2006, 11
73
The goal of this study was to clear up the peculiarities of the synthesis procedure and to investigate
the structural features of products obtained. It is known that in the reaction of aromatic amines with
ethyl-3-oxobutanoate two types of products can form: amides and condensation products – ethyl-β-
arylaminocrotonates [6], and that the direction of the reaction depends on the temperature and catalyst.
Results and Discussion
Reaction of 3-amino-9-ethylcarbazole (1b) with ethyl-3-oxobutanoate in refluxing toluene
provided only the acylation reaction product - N-(9-ethylcarbazol-3-yl)-3-oxobutanamide (3, Scheme
1). Addition of a catalytic amount of hydrochloric acid to the reaction solution led to the formation of a
mixture of two products – the amide 3 and the condensation product ethyl-3-[(9-ethylcarbazol-3-
yl)amino]-2-butenoate (2b) in a 1:4 ratio. Pure condensation products 2a-c were obtained by reaction
of amines 1a-c with ethyl-3-oxobutanoate in refluxing benzene in the presence of a catalytic amount of
hydrochloric acid with azeotropic separation of the water formed.
Intramolecular cyclizations of compounds 2a-c were carried out in mineral oil at 240-250°C. The
reaction according to the synthesis methods of described in literature [7] took 15-20 min, giving
compounds 4a-c in quite moderate yields of 46-69%. Prolonged reaction times led to decreased yields
of the products.
1H-, 13C-NMR spectra and INEPT 13C-NMR experiments proved the structure of the compounds
obtained. The assignment of the resonances in the NMR spectra was based on chemical shift theory
[8,9] and signal intensity arguments, multiplicities and comparison with structurally related
compounds [10-16]. The carbon atoms are identified following the arbitrary numbering given in
Scheme 1. The results of NMR studies are presented in Table 1.
The spectral lines intrinsic to the carbazolyl and butenoate fragment have been observed in the 13C-
NMR spectra of compounds 2a-c. Changes of solvent and the 9N-substituents in the carbazolyl moiety
resulted in weak changes of the chemical shifts of carbon resonances, therefore the structural features
of the side chain were studied in more detail. The chemical shifts of the double bond of the butenoate
moiety were successfully calculated using the additivity rules of substituent influence on the double
bond. It was noticed that the double bond in compounds 2a-c is quite polarized due to the different
electronic effects of the substituents present [8,9]. The C-11 atom of the double bond adjacent to the
NHR group is strongly deshielded and resonates approximately at 160 ppm. The signal of the C-12
atom of the double bond adjacent to the COOCH2CH3 group is observed much further upfield –
approximately at 84 ppm.
Compound 3 is distinguished by the characteristic fragments of the side chain moiety, which were
specifically reflected in its 13C-NMR spectra. The resonances of the aliphatic carbons of the COCH3
and COCH2CO fragments and the resonances of both CO group carbons in the downfield region
reliably confirmed the formation of compound 3.

Molecules 2006, 11
74
Scheme 1
+
NH2
CH3COCH2COOC2H5
N
R
1a-c
H
H
N
N
12
11
5
13
4
CH3
O
3
10
6
5
a
C2H5
4 a
O
O
2
7
CH3
O
9
8
1a
a
1
8
N
N
R
C2H5
3
2a-c
to
12
CH3
11
13
10
O
NH
4
5
3
6
5
a
4
a
2
7
9
8
1a
a
1
N
8
R
4a-c
a: R=CH3, b: R=C2H5, c: R=C3H7
Compounds 4a-c were obtained by cyclization of the butenoate fragment. Particular attention was
paid to the structure determination of the cyclization products. The 13C-NMR spectra of compounds
4a-c were assigned on the basis of the model spectrum of 2-methyl-4-quinolone [17]. The respective
changes to the spectral information of this compound using the chemical shift additivity rules enabled
us to evaluate the chemical shifts of the carbons of the formed ring and its influence on carbazolyl
fragment moiety, which is adjacent to the newly formed cycle. The C-11 atom of the double bond
adjacent to the NH group in the cyclic compounds 4a-c is more shielded (146.5 ppm), and the C-12
atom of double bond is more deshielded (108.5 ppm), respectively, in comparison with the chemical
shifts of the corresponding carbons in acyclic compounds 2a-c.
In order to gain further insight about the cyclization of butenoate fragment the 1H-NMR spectra of
the carbazole fragments were investigated in detail. The hydrogen resonances of this moiety in
compounds 2a-c were completely and unambigously assigned by the concerted examination of their
chemical shifts and spin-spin couplings. It is important to note that all hydrogen resonances of the
fragment mentioned above were reliably distinguished by their characteristic splittting patterns. Spin-
spin couplings over three (3JHCCH) bonds were derived for all hydrogens of the carbazole fragment with

Molecules 2006, 11
75
the exception of the H-4 atom. The narrow multiplicty induced by the detectable long-range – over
four bond coupling (4JHCCCH) was observed for all hydrogens of the carbazole fragment with the
exception of the H-1 atom. The formation of compounds 4a-c from 2a-c led to changes in the chemical
shifts and multiplicities of some of the hydrogen atoms. For instance, the disappearance of the narrow
splitting doublet resonating at 8 ppm and attributed to H-4 was detected, notwithstanding the fact that
the doublet with three bond splitting attributed to H-2 was found to resonate in almost the same place.
The chemical shifts of the resonances of H-6, H-7, H-8, which were remote from the changes in the
molecule were less perturbed. The largest alternation in the chemical shift occurred for the H-5 atom.
A singlet corresponding to the CH group hydrogen of the side chain double bond is seen at 4.7
ppm for compounds 2a-c, though for compounds 4a-c it appears at 6.1 ppm after ring formation. The
singlet of the CH3 group hydrogens of the acyclic chain is observed at 1.9 ppm, but the one in the ring
is at 2.4 ppm. Finally, compounds 4a-b have no ester group, whose characteristic triplet and
quadruplet were observed at 1.1 ppm and 4.1 ppm, respectively, in the spectra of compounds 2a-c. The
proton of the NH group in cycle is also more deshielded. It resonates at 11.6 ppm, whereas the signal
of the proton of the NH group of the acyclic chain in compounds 2a-c is at 10.4 ppm.
The data obtained from computer molecular modeling are in reasonable agreement with the NMR
findings. The models of molecules of studied compounds were optimized to the total steric energy
(Figure 1) by MM2 molecular mechanics and AM1 semi-empirical quantum mechanical methods. The
computer molecular models demonstrated the turn of side chain towards the carbazole ring for
compounds 2a-c, but the preference of the side chain for the straight structure in compound 3.
Figure 1. View of optimized to the total steric energy molecular models of compounds 2b, 3 and 4b
2b (E = 14.42 kcal/mol)
3 (E = 3.69 kcal/mol)
4b (E = 14.81 kcal/mol)
Extended Hückel partial charges derived from the optimized models of compounds 2a-c revealed
more negative C-4 (-O.144 a. v) and H-4 (0.023 a.v.) atoms in comparison ones with C-2 (-0.122 a.v.)
and H-4 (0.031 a. v.) of compounds 4a-c. This fact was one more argument for the cyclization onto the
C-4 atom, with no participation of the carbazole ring C-2 atom. The close contact perceived between
the CO group oxygen of the new heterocycle and the H-5 atom of the carbazole ring related to the
deshielding of H-5 atom in compounds 4a-c.

Molecules 2006, 11
76
Conclusions
It was determined that, depending on the reaction conditions, 9-alkyl-3-aminocarbazoles upon
reaction with ethyl-3-oxobutanoate formed acylation or condensation products, whose intramolecular
cyclization at 240-250 °C took place onto the 4-position of the carbazole ring providing substituted
pyrido[2,3-c]carbazol-1-ones. Taking into consideration that carbazoles are structurally similar to
benzenes, the synthesized compounds were successfully studied by NMR spectra using the substituent
effect rules as for benzenes. The results obtained during the NMR investigation fully substantiated the
structural distinctions of studied compounds. Computer molecular modeling data supported the
findings deduced from the 13C-NMR and the 1H-NMR spectra.
Experimental
General
1H- and 13C-NMR spectra were recorded on a Bruker AC 250-P (250 MHz), Bruker DRX 500 (500
MHz) and Varian Unity Inova 300 MHz spectrometers operating in Fourier transform mode with TMS
as an internal standard. The IR spectra were measured on a Perkin-Elmer Spectrum GX FT-IR system.
Silica gel plates (Silufol UV-254) were used for analytical tlc. Mass spectral data were obtained on
Waters (Micromass) ZQ 2000 Spectrometer. Physical properties, analytical data and yields of the
prepared compounds are given in Table 2. The molecular modeling of the studied compounds was
carried out using Chem 3D Ultra 9.0 [18].
Ethyl-3-[(9-methyl-9H-carbazol-3-yl)amino]but-2-enoate (2a). A mixture of 3-amino-9-methyl-
carbazole (1a, 7.85 g, 0.04 mol), benzene (100 mL), ethyl-3-oxobutanoate (7.6 mL, 0.06 mol) and
hydrochloric acid (0.5 mL) was refluxed for 5 h with azeotropic separation of the water formed. The
benzene was evaporated under reduced pressure and the residue was poured into hexane (100 mL) and
was kept cold for crystallization. The precipitate was filtered, washed with hexane and recrystallized
from hexane.
Ethyl-3-[(9-ethyl-9H-carbazol-3-yl)amino]but-2-enoate (2b) was obtained from 3-amino-9-ethyl-
carbazole 1b (15 g, 0.07 mol) in the same way as described for 2a. MS (m/z): 323.2 [M++1].
Ethyl-3-[(9-propyl-9H-carbazol-3-yl)amino]but-2-enoate (2c) was obtained from 3-amino-9-
propylcarbazole 1c (15 g, 0.07 mol) in the same way as described for 2a.
N-(9-ethyl-9H-carbazol-3-yl)-3-oxobutanamide (3). The reaction mixture of 3-amino-9-ethylcarba-
zole (1b, 2.1 g, 0.01 mol), ethyl-3-oxobutanoate (3.79 mL, 0.03 mol) and toluene (25 mL) was
refluxed for 2 h and was kept in cold for crystallization. The precipitate formed was filtered off,
washed with hexane and recrystallized from toluene.

Molecules 2006, 11
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3,7-Dimethyl-4,7-dihydro-1H-pyrido[2,3-c]carbazol-1-one (4a). A mixture of compound 2a (2 g,
0.006 mol) and mineral oil (15 mL) was heated at 240-250 °C for 20 min, then cooled down to 20 °C
and diluted with hexane. The precipitate formed was filtered off, washed with hexane and
recrystallized from dioxane.
7-Ethyl-3-methyl-4,7-dihydro-1H-pyrido[2,3-c]carbazol-1-one (4b) was obtained from compound
2b (1 g, 0.003 mol) in the same way as described for 4a. The product formed was purified by column
chromatography (Silikagel L 40/100, eluent: acetone). MS (m/z): 277.2 [M++1].
3-Methyl-7-propyl-4,7-dihydro-1H-pyrido[2,3-c]carbazol-1-one (4c) was obtained from compound
2c (4 g, 0.01 mol) in the same way as described for 4a. The product formed was purified by column
chromatography (Silikagel L 40/100, eluent: acetone).
Table 1. Spectroscopic data of the prepared compounds (NMR: δ, ppm; J, Hz; IR: cm-1)
IR
1H-NMR (solvent)
13C-NMR (solvent)
(KBr tabl.)
(CD3)2CO): 1.24 (t, 3H, J3 = 7.1, COOCH2CH3),
1.97 (s, 3H, CCH3), 3.92 (s, 3H, NCH3), 4.11 (q, 2H,
J = 7.1, COOCH2CH3), 4.67 (s, 1H, CH=), 7.21 (td,
1H, J3 = 6.8, J3 = 7.9, J4 = 1.3, Ar-6C-H), 7.30 (dd,
1H, J3 = 8.6, J4 = 2.0, Ar-2C-H), 7.48 (td, 1H, J3 =
6.8, J3 = 8.2, J4 = 1.3, Ar-7C-H), 7.53 (d, 1H, J3 =
8.6, Ar-1C-H), 7.54 (dd, IH, J = 8.2, J = 1.3, Ar-8C-
H), 7.98 (d, 1H, J4 = 2.0, Ar-4C-H), 8.17 (dd 1H, J3 =
7.9, J4 = 1.3, Ar-5C H), 10.48 (s, 1H, NH).
(CD3)2CO): 14.96 (COOCH2CH3),
20.18 (CCH3), 29.48 (NCH3), 58.80
(COOCH2CH3), 85.09 (CH=), 109.80
(Ar-C-8), 109.89 (Ar-C-1), 118.01 (Ar-C-
4), 119.71 (Ar-C-6), 121.22 (Ar-C-5),
123.17 (Ar-C-5a), 123.78 (Ar-C-4a),
124.77 (Ar-C-2), 126.92 (Ar-C-7), 131.73
(Ar-C-3), 139.91 (Ar-C-1a), 142.52 (Ar-
C-8a), 161.26 (C=), 170.94 (CO).
3250(NH),
1656(CO).
2a
3
4
(d6-DMSO): 13.63 (NCH2CH3), 14.49
(COOCH2CH3), 19.76 (CCH3), 36.99
(NCH2CH3), 57.90 (COOCH2CH3), 83.93
(C=), 109.13 (Ar-C-8), 109.25 (Ar-C-1),
116.99 (Ar-C-4), 118.65 (Ar-C-6), 120.64
(Ar-C-5), 121.86 (Ar-C-5a), 122.42 (Ar-
C-4a), 123.57 (Ar-C-2), 125.98 (Ar-C-7),
130.21 (Ar-C-3), 137.37 (Ar-C-1a),
140.03 (Ar-C-8a), 160.29 (C=), 169.48
(CO).
(d6-DMSO): 1.22 (t, 3H, J = 7.1, COOCH2CH3), 1.32
(t, 3H, J = 7.1, NCH2CH3), 1.96 (s, 3H, CCH3),
4.08 (q, 2H, J = 7.1, COOCH2CH3), 4.43 (q, 2H, J =
7.1, NCH2CH3), 4.68 (s, 1H, CH=), 7.19 (td, 1H, J3 =
7.4, J3 = 7.6, J4= 1.3, Ar-6C-H), 7.29 (dd, 1H, J3 =
8.6, J4 = 2.0, Ar-2C-H), 7.46 (td, 1H, J3 = 6.6, J3 =
7.4, J4 = 1.3, Ar-7C-H), 7.58 (d, 1H, J3 = 8.6, Ar-1C-
H), 7.59 (dd, 1H, J3 = 6.6, J3 = 1.3, Ar-8C-H), 8.02
(d, 1H, J4 = 2.0, Ar-4C-H), 8.18 (dd, 1H, J3 = 7.6, J4
=1.3, Ar-5C-H), 10.38 (s, 1H, NH).
3267(NH),
1652(CO).
2b
(CDCl3): 11.82 (NCH2CH2CH3), 14.68
(COOCH2CH3), 20.29 (CCH3), 22.34
(NCH2CH2CH3), 44.78 NCH2CH2CH3),
58.60 (COOCH2CH3), 84.22 (C=), 108.79
(Ar-C-8), 108.93 (Ar-C-1), 117.79 (Ar-C-
4), 118.93 (Ar-C-6), 120.39 (Ar-C-5),
122.37 (Ar-C-5a), 122.99 (Ar-C-4a),
124.26 (Ar-C-2), 126.04 (Ar-C-7), 130.70
(Ar-C-3), 138.58 (Ar-C-1a), 141.05 (Ar-
C-8a), 160.76 (C=), 170.61 (CO).
(CDCl3): 0.98 (t, 3H, J=7.5, COOCH2CH3), 1.31 (t,
3H, J = 6.9, NCH2CH2CH3), 1.89 − 1.92 (m, 2H,
NCH2CH2CH3), 1.94 (s, 3H, CCH3), 4.18 (q, 2H, J =
7.5, COOCH2CH3), 4.26 (q, 2H, J = 6.9,
3257(NH),
1651(CO).
3
NCH2CH2CH3), 4.69 (s, 1H, CH=), 7.21 (dd, 1H, J =
8.2, J4 = 2.0, Ar-2C-H), 7.22 (td, 1H, J3 = 7.6, J3 =
8.2, J4 = 1.3, Ar-6C-H), 7.34 (dd, 1H, J3 = 6.9, J4 =
1.3, Ar-8C-H), 7.40 (d, 1H, J3 = 8.2, Ar-1C-H),
2c
7.47 (td, 1H, J3 = 8.2, J3 = 6.9, J4 = 1.3, Ar-7C-H),
7.83 (d, 1H, J4 = 2.0, Ar-4C-H), 8.03 (dd, 1H, J3 =
7.6, J4 = 1.3, Ar-5C-H), 10.38 (s, 1H, NH).

Molecules 2006, 11
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Table 1. Cont.
(CDCl3): 14.06 (NCH2CH3), 31.45
(COCH3), 37.81 (NCH2CH3), 50.30
(COCH2CO), 108.71 (Ar-C-8), 108.79
(Ar-C-1), 113.26 (Ar-C-4), 119.01 or
119.86 (Ar-C-6), 119.01 or 119.86 (Ar-C-
2), 120.96 (Ar-C-5), 122.99 (Ar-C-5a),
123.21 (Ar-C-4a), 126.12 (Ar-C-7),
129.60 (Ar-C-3), 137.55 (Ar-C-1a),
140.66 (Ar-C-8a), 163.93 (NHCO),
205.54 (COCH3).
(CDCl3): 1.41 (t, 3H, J = 7.2, NCH2CH3), 2.36 (s,
3H, COCH3), 3.65 (s, 2H, COCH2), 4.32 (q, 2H, J =
7.2, NCH2CH3), 7.23 (td, 1H, J3 = 7.0, J3 = 7.8, J4 =
1.1, Ar-6C-H), 7.31 (d, 1H, J3 = 8.7, Ar-1C-H),
7.40 (dd, 1H, J3 = 8.2, J4 = 1.1, Ar-8C-H), 7.49 (td,
1H, J3 = 8.2, J3 = 7.0, J4 = 1.1, Ar-7C-H), 7.55 (dd,
1H, J3 = 8.7, J4 = 2.0, Ar-2C-H), 8.08 (dd, 1H, J3 =
7.8, J4 = 1.1, Ar-5C-H), 8.36 (d, 1H, J4 = 2.0, Ar-4C-
H), 9.23 (s, 1H, NH).
3276(NH),
1721(CO),
1640(CO).
3
(d6-DMSO): 2.41 (s, 3H, CCH3), 3.97 (s, 3H, NCH3), (d6-DMSO): 18.87 (CCH3), 29.01
3267(NH),
1623(CO).
6.09 (CH=), 7.18 (td, 1H, J3 = 7.1, J3 = 8.2, Ar-6C-
(NCH3), 108.60 (CH=), 109.93 (Ar-C-1),
3
3
109.93 (Ar-C-8), 114.72 (Ar-C-2), 116.57
(Ar-C-4), 117.91 (Ar-C-6), 121.04 (Ar-C-
4a), 121.04 (Ar-C-5a), 122.75 (Ar-C-5),
125.28 (Ar-C-7), 128.90 (Ar-C-3), 136.33
(Ar-C-1a), 140.70 (Ar-C-8a), 146.68
(C=), 177.97 (CO).
H), 7.46 (td, 1H, J = 8.2, J = 7.1, Ar-7C-H), 7.60 (d,
1H, J3 = 8.2, Ar-8C-H), 7.69 (d, 1H, J3 = 8.9, Ar-1C-
H), 8.02 (d, 1H, J3 = 8.9, Ar-2C-H), 9.94 (d, 1H, J3 =
8.2, Ar-5C-H), 11.69 (s, 1H, NH).
4a
(d6-DMSO): 13.91 (NCH2CH3), 18.89
(CH3), 36.86 (NCH2CH3), 108.52 (CH=),
3281(NH),
1619(CO).
(d6-DMSO): 1.28 (t, 3H, J = 7.2, NCH2CH3), 2.45 (s,
3H, CCH3), 4.52 (q, 2H, J = 7.2 NCH2CH3),
6.05 (s, 1H, CH=), 7.14 (t, 1H, J3 = 7.5, J3 = 8.2, Ar-
6C-H), 7.42 (t, 1H, J3 = 7.5, J3 = 8.2, Ar-7C-H),
109.95 (Ar-C-1), 109.95 (Ar-C-8), 114.67
(Ar-C-2), 116.62 (Ar-C-4), 117.93 (Ar-C-
6), 121.19 (Ar-C-4a), 121.19 (Ar-C-5a),
7.59 (d, 1H, J3 = 8.2, Ar-8C-H), 7.65 (d, 1H, J3 = 8,8,
Ar-1C-H), 8.02 (d, 1H, J3 = 8.8, Ar-2C-H), 9.90 (d,
1H, J3 = 8.2, Ar-5C-H), 11.65 (s, 1H, NH).
4b
122.93 (Ar-C-5), 125.29 (Ar-C-7),
129.10 (Ar-C-3), 136.34 (Ar-C-1a),
139.58 (Ar-C-8a), 146.58 (C=),
177.97 (CO).
(d6-DMSO): 11.31 (NCH2CH2CH3),
18.84 (CH3), 22.09 (NCH2CH2CH3),
43.53 (NCH2CH2CH3), 108.98 (CH=),
109.93 or 109.99 (Ar-C-1), 109.93 or
109.99 (Ar-C-8), 114.94 (Ar-C-2), 116.56
(Ar-C-4), 117.88 (Ar-C-6), 121.11 (Ar-C-
5a), 121.11 (Ar-C-4a), 122.78 (Ar-C-5),
125.23 (Ar-C-7), 129.03 (Ar-C-3),
136.32 (Ar-C-1a), 140.13 (Ar-C-8a),
146.51 (C=), 177.98 (CO).
3283(NH),
1643(CO).
(d6-DMSO): 0.85 (t, J = 7.2, 3H, NCH2CH2CH3),
1.75 − 1.82 (m, 2H, NCH2CH2CH3), 2.37 (s, 3H,
CCH3), 4.55 (t, J = 7.2, 2H, NCH2CH2CH3),
6.04 (s, 1H, CH=), 7.13 (t, 1H, J3 = 7.6, J3 = 8.2,
Ar-6C-H), 7.41 (t, 1H, J3 = 7.6, J3 = 8.2, Ar-7C-
H), 7.60 (d, 1H, J3 = 8.2, Ar-8C-H), 7.64 (d, 1H,
J3 = 8.8, Ar-1C-H), 8.03 (d, 1H, J3 = 8.8, Ar-2C-
H), 9.90 (d, 1H, J3 = 8.2, Ar-5C-H),
4c
11.63 (s, 1H, NH).
Table 2. The physical, analytical and yield data of the studied compounds
Elemental analysis data
m. p.
Molecular
Yield
(Calculated / Found) %
(°C)
Formula
(%)
C
H
N
2a 130 – 131
C19H20N2O2
C20H22N2O2
C21H24N2O2
C18H18N2O2
74.00 / 74.08
74.51 / 74.46
74.97 / 74.71
73.45 / 73.34
6.54 / 6.48
6.88 / 7.09
7.19 / 7.24
6.16 / 6.37
9.08 / 8.96
8.69 / 8.43
8.33 / 8.43
9.52 / 9.45
80.0
83.0
76.0
73.0
2b 134 – 135
2c
3
77 – 78
157 – 158

Molecules 2006, 11
79
Table 2. Cont.
77.84 / 77.63
4a
C17H14N2O
C18H16N2O
C19H18N2O
5.38 / 5.10
5.84 / 5.82
4.59 / 4.62
10.68 / 10.45
10.14 / 10.09
9.81 / 9.92
63.0
46.0
69.0
>330
4b 254 – 256
4c 274 – 275
78.24 / 78.20
79.90 / 79.86
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