One-pot four-component synthesis of some novel octahydroquinolindiones using ZnO as an efficient catalyst in water

Article abstract of DOI:10.1016/j.tetlet.2012.09.053

ZnO has been shown to be an inexpensive, efficient, readily available, and mild catalyst for a one-pot fourcomponent synthesis of some novel octahydroquinolindione-3-carboxylic acid ethyl esters using diethylmalonate, dimedone, ammonium acetate, and appropriate aromatic aldehydes in water at reflux. ZnO acts as a recyclable heterogeneous catalyst to afford the products in excellent yield in short reaction duration.

Full text of DOI:10.1016/j.tetlet.2012.09.053

Tetrahedron Letters 53 (2012) 6306–6309
Contents lists available at SciVerse ScienceDirect
Tetrahedron Letters
journal homepage: www.elsevier.com/locate/tetlet
One-pot four-component synthesis of some novel octahydroquinolindiones
using ZnO as an efficient catalyst in water
Sadeq Hamood Saleh Azzam a, Aisha Siddekha a,b, M. A. Pasha a,
⇑
a Department of Studies in Chemistry, Central College Campus, Palace Road, Bangalore University, Bengaluru 560001, India
b Department of Chemistry, Smt. V.H.D. Central Institute of Home Science, Bengaluru 560001, India
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 12 June 2012
Revised 11 September 2012
Accepted 14 September 2012
Available online 21 September 2012
ZnO has been shown to be an inexpensive, efficient, readily available, and mild catalyst for a one-pot four-
component synthesis of some novel octahydroquinolindione-3-carboxylic acid ethyl esters using dieth-
ylmalonate, dimedone, ammonium acetate, and appropriate aromatic aldehydes in water at reflux.
ZnO acts as a recyclable heterogeneous catalyst to afford the products in excellent yield in short reaction
duration.
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Octahydroquinolindiones
Aromatic aldehydes
Dimedone/1,3-cyclohexadione
Ammonium acetate
Diethylmalonate
ZnO
Water
In recent years, the growing environmental concern in chemis-
try has turned the spotlight on multicomponent reactions as the
new trend in organic chemistry.1 Multicomponent reactions
(MCRs) are very important for the construction of many heterocy-
clic compounds,2 using this strategy many biologically active sub-
stances and natural products have been synthesized.3
The synthesis of nitrogen heterocycles is of great interest
because they constitute an important class of natural and synthetic
products, many of which exhibit useful biological activity and find
application in pharmaceutical preparations.4–7
The quinoline ring system is an important structural unit in
many naturally occurring alkaloids, therapeutics, and in the syn-
thetic analogues with interesting biological activities.8 Quinolines
are also very important for designing many pharmacologically
important compounds,9 due to their wide spectrum of biological
activities such as antimalarial, anti-bacterial, anti-asthmatic, anti-
hypertensive, anti-inflammatory, anti-platelet, and tyrokinase
PDGF-RTK inhibiting activities.10–12 Therefore, the development
of new and efficient methodologies for the synthesis of quinoline
ring system will be interesting in both synthetic organic and
medicinal chemistry.13 Methods for the synthesis of the quinoline
ring system have been developed and documented in the litera-
ture.14 However, most of these methods are not completely satis-
factory with regard to the yield and reaction conditions. Hence, a
simple and an efficient method for the synthesis of the quinolone
ring system is still in demand.
Recently, the heterogeneous catalysis has developed consider-
able interest in the various disciplines of science including organic
synthesis due to the prime advantage that, in most of the cases the
heterogeneous catalysts can be recovered with only minor change
in activity and selectivity so that they can be used in continuous
flow reactions.15 Heterogeneous catalysts have many advantages
over their homogeneous counterparts.
In continuation of our efforts to develop new methods for the
synthesis of biologically active heterocyclic compounds using
readily available, inexpensive, and environment friendly cata-
lysts,16–22 herein, we wish to report a mild and efficient method
for the synthesis23 of some novel 4-aryl-2,5-dioxo-1,2,3,4,5,6,7,8-
octahydroquinoline-3-carboxylic acid ethyl esters. This method
utilizes a one-pot four-component reaction of aromatic aldehydes,
diethyl malonate, dimedone/1,3-cyclohexadione, and ammonium
acetate in the presence of readily available, inexpensive, mild,
recyclable, and common laboratory chemical ZnO as a catalyst
(Scheme 1).
An initial study was performed by treating a mixture of anisal-
dehyde, diethyl malonate, dimedone, and ammonium acetate in
water without any catalyst similar to the reaction which was car-
ried out to get N-amino derivative of substituted quinoline-2,5-
dione as one of the intermediates in a multistep reaction,24 and
found that, the reaction was possible in water under reflux, and
the isolated yield after 8 h was low (45%, Table 2, entry 1). When
⇑
Corresponding author. Tel./fax: +91 80 22961337.
E-mail address: mafpasha@gmail.com (M.A. Pasha).
0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.tetlet.2012.09.053

S. H. S. Azzam et al. / Tetrahedron Letters 53 (2012) 6306–6309
6307
R
CHO
O
O
O
O
O
O
ZnO/H2O
Reflux
O
+
NH4OAc
+
+
R
O
O
N
O
H
5
1
2
3
4
Scheme 1. Synthesis of octahydroquinolindiones.
Table 1
Influence of various catalysts on the synthesis of octahydroquinolindiones
Table 3
Effect of solvent on the synthesis of octahydroquinolindiones
Entry
Catalysta
Time (h)
Yieldb(%)
Entry
Solvent (reflux)
Time(h)
Yielda (%)
1
2
3
4
5
6
AmberliteIR120 Hc
CeCl3
ZnCl2
K2CO3
Ba(OH)2
ZnO
13
12
10
6
6
2
20
30
35
40
70
90
1
2
3
4
EtOH
MeOH
CH3CN
H2O
4
5
6
2
65
70
55
90
a
Isolated yield.
a
b
c
30 mol %.
Isolated yield.
0.1 g.
Table 4
Synthesis of octahydroquinolindiones catalyzed by ZnO in water
Entry Aldehydes
Producta Time (h) Yieldb (%) Mp oC
the reaction was carried out with ammonium acetate (3 mmol),
the yield was again 45% (isolated yield) after 15 h (Table 2, entry
2). As the reaction requires a catalyst, we performed the reaction
using Amberlite IR-120H (0.1 g), 30 mol % acidic (CeCl3, ZnCl2,)
and basic catalysts (K2CO3, Ba(OH)2, ZnO). We found that, ZnO is
best in terms of yield and duration of reaction (Table 1, entry 6).
ZnO has earlier been shown to be a mild base and finds application
in organic synthesis.25
1
2
3
4
5
6
7
8
9
4-MeOC6H4CHO
3,4-(MeO)2C6H3CHO 5b
5a
2
90
85
87
90
88
86
ND
ND
40
145–147
160–163
230–232
168–170
173–175
238–240
—
2.5
2.5
2
2
2.5
2-HOC6H4CHO
3-NO2C6H4CHO
2-NO2C6H4CHO
4-ClC6H4CHO
HCHO
5c
5d
5e
5f
5g
5h
5ic
15
15
10
CH3CHO
3-NO2C6H4CHO
—
186–189
Further, studies were carried out to optimize the amount of cat-
alyst by using different amounts of ZnO (3, 5, 6, 7.5, 10, 15, and
30 mol %) and the results are presented in Table 2; we found that,
7.5 mol % of ZnO affords the product in 90% isolated yield. Increas-
ing the amount of catalyst did not improve the yield (Table 2).
It was noticed that, the reaction is also possible by ZnO in
refluxing EtOH, MeOH, and CH3CN; among the solvents used H2O
was found to be the best solvent as shown in Table 3.
To demonstrate the generality of this method, we performed all
further reactions using ZnO (7.5 mol %) in water at reflux, and
found that, ZnO can efficiently catalyze the reaction between dime-
done, diethyl malonate, ammonium acetate, and different aromatic
aldehydes to afford excellent yield of the desired products within
2–2.5 h. When we carried out the reaction using aliphatic
aldehydes, there was no product formation even after 15 h (Table
4, entries 7,8). We also examined the use of 1,3-cyclohexandione
instead of dimedone (Table 4, entry 9) and found that, the reaction
a
All isolated products are new and were characterized by IR, 1H NMR, 13C NMR
spectral and CHN analyses.
b
Isolated yields.
c
1,3-cyclohexandione (0.1 mmol) was used instead of dimedone.
works but the isolated yield after 10 h is only 40%. From Table 4, it
is clear that, the method is equally effective for both electron with-
drawing and electron donating aromatic aldehydes.
In recent years, Raman spectroscopy has been proved to be a
valuable tool in the investigation of structure of complex mole-
cules of biological interest.26 Recently, we have reported the vibra-
tional studies on 6-amino-4-(40-methoxyphenyl)-5-cyano-3-
methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole.27
To determine the configuration of C15 (C4) and C16 (C3) in 4-
(20-nitrophenyl)-7,7-dimethyl-2,5-dioxo-1,2,3,4,5,6,7,8-octahydro-
quinoline-3-carboxylic acid ethyl ester (5e), the vibrational
frequencies were calculated and the scaled values were compared
with experimental FT-IR and FT-Raman spectral values for both cis-
and trans- isomers to find the structure of 5e. It is found that, the
observed and the calculated frequencies of e,e0-trans- isomer are
found to be in good agreement for the important functional groups
as shown in Table 5. These frequency calculations were carried out
on the optimized structure of 5e using the program available in the
GAUSSIAN software.28–30
Table 2
Optimization of the amount of ZnO
Entry ZnO
mol %
Amount of H2O Amount of NH4OAc
Time
(h)
Yielda
(%)
(ml)
(mmol)
1
2
3
4
5
6
7
8
9
10
0
0
3
3
5
6
7.5
10
10
10
10
10
10
10
10
10
10
10
2
3
2
2
2
2
2
2
2
2
8
15
15
3
3
2
2
2
2
2
45
45
60
50
60
75
90
90
90
89
The optimized geometry of 5e and the numbering system is
given in Figure 1. From the density functional theory (DFT) calcu-
lations we found that, the configuration of C15 (C4) and C16 (C3)
in 5e is ee0-trans.
The possibility of recycling the catalyst was then examined.
After completion of the reaction (2–2.5 h), the contents were
filtered and dichloromethane (10 ml) was added to the residue,
15
30
a
Isolated yield.

6308
S. H. S. Azzam et al. / Tetrahedron Letters 53 (2012) 6306–6309
Table 5
Comparison of some important computed and experimental vibrational frequencies of cis- and trans-5e
Serial no.
Functional group
Calculated frequency
m
cmꢀ1 trans
Exptl. FT-IRa
m
cmꢀ1
Exptl. FT-Ramana
m
cmꢀ1
Calculated frequency m
cmꢀ1 cis
1
2
3
4
C@O(pyridine)
C@O (Ester)
C15-H19 (str)
C16-H50 (str)
1618
1718
2921
2973
1617
1721
2922
2961
1616
1723
2916
2952
1715
1697
2949
3018
a
(FT-IR and FT-Raman spectra are available as supplementary data).
Figure 1. Optimized structure of 5e.
Figure 2. Reusability of ZnO in the synthesis of octahydroquinolindiones.
the catalyst was filtered and washed with dichloromethane and
recycled five times. From the Figure 2, it can be seen that, in the
first four runs the activity was more or less maintained but after
the fourth run it starts decreasing, which is due to loss of the cat-
alyst during recovery and the recovered amount of catalyst is
0.025, 0.024, 0.023, 0.022, and 0.020 g and the respective isolated
yields for the five runs is found to be 90%, 89%, 87%, 85%, and 78%.
In conclusion, we have developed a new, rapid, and efficient
method for the synthesis of 4-aryl-2,5-dioxo-1,2,3,4,5,6,7,8-octa-
hydroquinoline-3-carboxylic acid ethyl esters by a one-pot four
component reaction of aromatic aldehydes, diethyl malonate,
dimedone/1,3-cyclohexadione, and ammonium acetate using ZnO
as an efficient, mild, and heterogeneous catalyst which could be re-
used for at least five times. The reaction is facile, simple, and envi-
ronment-friendly.
Umapathy, Professor, Dept. of IPC, IISc., Bangalore for the FT-IR,
FT-Raman spectra, for the vibrational spectroscopic studies and
DTF calculations. Authors also acknowledge the financial assis-
tance by the VGST, Dept. of Science & Technology, Government of
Karnataka for the CESEM Award Grant No. 24 (2010–2011).
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.tetlet.2012. 09.053.
References and notes
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Acknowledgments
One of the authors, S.H.S.A gratefully acknowledges the Sana
University, Yemen for a fellowship. The authors also thank Dr. S.

S. H. S. Azzam et al. / Tetrahedron Letters 53 (2012) 6306–6309
6309
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NH); 13C NMR (100 MHz, CDCl3): d 190.9 (C@O), 179.8 (NC@O), 160.0 (OC@O),
147.4 (NC@C), 130.8, 122.8, 119.3, 116.2, 111.2, 110.8 (all ArC), 110.8 (OC–
C@C), 61.8 (O–CH2), 56.2 (O–CH3), 56.1 (O–CH3), 47.5 (O@C–CH–C@O), 47.5
(CH2), 46.8 (CH2), 32.7 (C@C–CH), 31.7 (>C<), 30.4, 27.5 (CH3), 17.8 (CH3); Anal.
Calcd for C22H27N1O6: C, 65.82; H, 6.78; N, 3.49%. Found: C, 65.82; H, 6.782; N,
3.49%.
5c: Mp 230–232 °C; IR (KBr):
1668 (s), 1615 (vs), 1517 (s), 1448 (s), 1375 (vs), 1244 (s), 1135 (vs), 1037 (s)
cmꢀ1 1H NMR (400 MHz, CDCl3): d 1.11 (s, 6H, 2Me), 1.23 (t, J = 5.2 Hz, 3H,
m 3433 (br), 3232 (br), 2954 (s), 1734 (s), 1705 (s),
;
7. Swinbourne, J. F.; Hunt, H. J.; Klinkert, G. Adv. Heterocycl. Chem. 1987, 23, 103.
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Me), 2.35 (s,2H, CH2), 2.40 (s, 2H, CH2), 3.93 (q, J = 7.2 Hz, 2H, CH2), 4.07 (d,
J = 7.2 Hz,1H, CH), 4.57 (s, 1H, OH), 5.28 (d, J = 7.2 Hz, 1H, CH), 6.99 (d,
J = 5.6 Hz, 1H, Ph), 7.13 (d, J = 5.6 Hz, 1H, Ph),7.37 (d, J = 7.6 Hz, 1H, Ph), 7.41 (d,
J = J = 7.6 Hz, 1H, Ph), 10.49 (br, 1H, NH); 13C NMR (100 MHz, CDCl3): d 201.5
(C@O), 187.1 (NC@O), 169.1 (OC@O), 151.5 (NC@C), 128.4, 128.0, 125.0, 124.7,
118.7, 116.2 (all ArC), 111.4 (OC–C@C), 50.3 (O–CH2), 43.6 (O@C–CH–C@O),
42.0 (CH2), 31.4 (CH2), 30.4 (C@C–CH), 29.6 (>C<), 28.2, 26.8 (CH3), 17.1 (CH3);
Anal. Calcd for C20H23N1O5: C, 67.21; H, 6.49; N, 3.92%. Found: C, 67.20; H,
6.461; N, 3.91%.
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5d: Mp 168–170 °C; IR (KBr):
1615 (vs), 1527 (s), 1448 (s), 1377 (vs), 1336 (vs)1253 (s), 1166 (s), 1022 (s)
cmꢀ1 1H NMR (400 MHz, CDCl3): d 1.11 (s, 6H, 2Me), 1.23 (t, J = 5.2 Hz, 3H,
m 3433 (br), 2960 (s),1737(s), 1705 (s), 1668 (s),
;
Me), 2.35 (s,2H, CH2), 2.40 (s, 2H, CH2), 4.09 (q, J = 6.0 Hz, 2H, CH2), 4.38 (d,
J = 6 Hz,1H, CH), 5.54 (d, J = 7.2 Hz,1H, CH), 7.40–7.44 (m, 2H, Ph), 8.00–8.04
(m, 2H, Ph), 10.96 (s, 1H, NH); 13C NMR (100 MHz, CDCl3): d 191.3 (C@O), 180.9
(NC@O), 159.1 (OC@O), 137.5 (NC@C), 137.5, 132.5, 131.8, 130.0, 127.8, 124.6
(all ArC), 115.1 (OC–C@C), 57.8 (O–CH2), 47.3 (O@C–CH–C@O), 46.7 (CH2), 32.3
(CH2), 30.5 (C@C–CH), 29.0 (>C<), 28.6, 26.0 (CH3), 15.1 (CH3); Anal. Calcd for
C20H22N2O6: C, 62.17; H, 5.74; N, 7.25%. Found: C, 62.17; H, 5.741; N, 7.25%.
5e: Mp 173–175 °C; IR (KBr):
1615 (vs), 1523 (vs), 1448 (s), 1388 (s), 1367(s), 1238 (s), 1135 (vs), 1058 (s)
cmꢀ1 1H NMR (400 MHz, CDCl3): d 1.11 (s, 6H, 2Me), 1.23 (t, J = 5.2 Hz, 3H,
m 3433 (br), 2960 (s),1730 (s), 1705 (s), 1668 (s),
;
Me), 2.35 (s,2H, CH2), 2.40 (s, 2H, CH2), 4.09 (q, J = 6.0 Hz, 2H, CH2), 4.45 (d,
J = 6.8 Hz,1H, CH), 6.05 (d, J = 6.8 Hz, 1H, CH), 7.24 (d, J = 7.6 Hz, 1H, Ph), 7.03
(d, J = 7.6 Hz, 1H, Ph), 7.44 (d, J = 8.0 Hz, 1H, Ph), 7.47 (d, J = 8.0 Hz, 1H, Ph),
10.86 (s, 1H, NH); 13C NMR (100 MHz, CDCl3): d 191.6 (C@O), 178.1 (NC@O),
161.8 (OC@O), 148.8 (NC@C), 141.1, 133.3, 129.5, 122.7, 121.5, 115.2 (all ArC),
115.2 (OC–C@C), 54.8 (O–CH2), 47.4 (O@C–CH–C@O), 46.8 (CH2), 32.3 (CH2),
31.9 (C@C–CH), 30.1 (>C<), 27.6, 26.1 (CH3), 16.2 (CH3); Anal. Calcd for
C
20H22N2O6: C, 62.17; H, 5.74; N, 7.25%. Found: C, 62.17; H, 5.741; N, 7.24%.
5f: Mp 238–240 °C; IR (KBr): 3431 (br), 2956 (s),1734 (s), 1704 (s), 1668 (s),
1615 (vs), 1498 (s), 1396 (s), 1257 (s), 1135 (s), 1020 (s),827 (vs) cmꢀ1 1H NMR
22. Aatika, N.; Pasha, M. A. J. Saudi Chem. Soc. 2011, 15, 55.
m
23. General procedure:
A
mixture of aldehyde (1 mmol), diethyl malonate
;
(1 mmol), ZnO (0.025 g, 7.5 mol %) and water (10 ml) was refluxed for
30 min; dimedone/I,3-cyclohehadione (1 mmol) and ammonium acetate
(2 mmol) were then added to the reaction mixture and refluxed for the
remaining time (Table 4). The crude product thus separated was filtered and
washed with water, The dried solid residue was treated with dichloromethane
and filtered to get ZnO which could be reused. The filtrate was then evaporated
to get the desired solid 4-aryl-7,7-dimethyl-2,5dioxo-1,2,3,4,5,6,7,8-
octahydroquinoline-3-carboxylic acid ethyl ester which was subjected to
silica gel column chromatography [silica gel G, 100–200 mesh] to get the pure
product.
(400 MHz, CDCl3): d 1.11 (s, 6H, 2Me), 1.23 (t, J = 5.2 Hz, 3H, Me), 2.55 (s,2H,
CH2), 2.67 (s, 2H, CH2), 3.98 (q, J = 6 Hz, 2H, CH2), 4.16 (d, J = 7.2 Hz, 1H, CH),
5.48 (d, J = 7.2 Hz, 1H, CH), 7.00–7.02 (m, 2H, Ph), 7.21–7.23 (m, 2H, Ph), 10.87
(br, 1H, NH); 13C NMR (100 MHz, CDCl3): d 191.4 (C@O), 176.9 (NC@O), 160.9
(OC@O), 148.8 (NC@C), 131.4, 129.9, 128.8, 128.6, 117.8, 110.2 (all ArC), 110.2
(OC–C@C), 55.8 (O–CH2), 47.5 (O@C–CH–C@O), 46.8 (CH2), 32.8 (CH2),
31.8(C@C–CH), 30.1 (>C<), 30.1, 27.8 (CH3), 18.8 (CH3); Anal. Calcd for
C
20H22ClN1O4: C, 63.91; H, 5.90; N, 3.73%. Found: C, 63.91; H, 5.901; N, 3.72%.
5i: Mp 186–189 °C; IR (KBr): 3437 (br), 2958 (s),1730 (s), 1705 (s), 1667 (s),
1612 (vs), 1489 (s), 1386 (s), 1267 (s), 1138 (s), 1027 (s),824 (vs) cmꢀ1 1H NMR
m
;
The yields and Mps of all the products are presented in Table 4, and the
structures were confirmed by 1H NMR, 13C NMR spectral and CHN analyses.
Spectral data:
(400 MHz, DMSO-d6): d 1.24 (t, J = 7.2 Hz, 3H, 1Me), 1.89 (qn, J = 5.2 Hz, 2H,
CH2), 2.19 (t, J = 6.0 Hz, 2H, CH2), 3.34 (t, J = 8.0 Hz, 2H, CH2), 3.92 (d, J = 8.0 Hz,
1H, CH), 4.24 (q, J = 6 Hz, 2H, CH2), 4.99 (d, J = 8.0 Hz, 1H, CH), 5.48 (d,
J = 7.2 Hz, 1H, CH), 7.00–7.02 (m, 2H, Ph), 7.21–7.23 (m, 2H, Ph), 10.87 (br, 1H,
NH); 13C NMR (100 MHz, DMSO-d6): d 195.7 (C@O), 183.7 (NC@O), 168.7
(OC@O), 148.3 (NC@C), 152.9, 140.2, 135.2, 134.8, 131.6, 126.0 (all ArC), 112.4
(OC–C@C), 62.6 (O–CH2), 57.0 (O@C–CH–C@O), 36.5 (CH2), 33.7 (CH2), 27.2
(C@C–CH), 21.6 (CH2), 14.8 (CH3); Anal. Calcd for C20H22N2O6: C, 60.33; H, 5.06;
N, 7.82%. Found: C, 60.33; H, 5.o56; N, 7.83%.
5a: Mp 145–147 °C; IR (KBr):
m
3384 (br), 2958 (s), 1734 (s), 1704 (s), 1668 (s),
1615 (vs), 1508 (s), 1448 (s), 1375 (vs), 1245 (vs), 1173 (vs), 1033 (s) cmꢀ1
;
1H
NMR (400 MHz, CDCl3): d 1.11 (s, 6H, 2Me), 1.23 (t, J = 5.2 Hz, 3H, Me), 2.55
(s,2H, CH2), 2.67 (s, 2H, CH2), 3.53 (s, 3H, CH3), 3.98 (q, J = 6.0 Hz, 2H, CH2), 4.15
(d, J = 7.2 Hz,1H, CH), 5.82 (d, J = 7.2 Hz,1H, CH), 7.00–7.02 (m, 2H, Ph), 7.21–
7.23 (m, 2H, Ph), 10.87 (br, 1H, NH); 13C NMR (100 MHz, CDCl3): d 190.9 (C@O),
181.8 (NC@O), 158.0 (OC@O), 139.2 (NC@C), 130.2, 128.2, 127.2, 116.2, 114.1,
112.2 (all ArC), 112.2 (OC–C@C), 55.6 (O–CH2), 52.8 (O–CH3), 47.5 (O@C–CH–
C@O), 46.9 (CH2), 41.2 (CH2), 32.4 (C@C–CH), 31.8 (>C<), 30.2, 27.8 (CH3), 18.8
(CH3); Anal. Calcd for C21H25N1O5: C, 67.91; H, 6.78; N, 3.77%. Found: C, 67.91;
H, 6.782; N, 3.77%.
24. Dieter, E.; Ayhan, S. D. Tetrahedron Lett. 1987, 28, 3795.
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26. (a)Spectroscopy of Biological Systems, Advances in Spectroscopy, 13; Clark, R. J. H.,
Hester, R. E., Eds.; Wiley: Chichester, 1986; (b) Proceedings of the XVI
International Conference on Raman Spectroscopy, Wiley: Chichester, 1998.; (c)
Abraham, J. P.; Joe, I. H.; George, V.; Nielsen, O. F.; Jayakumar, V. S. Spectrochim.
Acta, Part A 2003, 59, 193.
5b: Mp 160-163 °C; IR (KBr):
m
3398 (br), 2962 (s), 1733(s), 1705 (s), 1668 (s),
1615 (vs), 1514 (s), 1448 (s), 1375 (vs), 1240 (vs), 1147 (vs), 1027 (s) cmꢀ1
;
1H
NMR (400 MHz, CDCl3): d 1.11 (s, 6H, 2Me), 1.23 (t, J = 5.2 Hz, 3H, Me), 2.35
(s,2H, CH2), 2.40 (s, 2H, CH2), 3.76 (s, 3H, CH3), 3.84 (s, 3H, CH3), 3.98 (q,
J = 5.2 Hz, 2H, CH2), 4.15 (d, J = 7.2 Hz,1H, CH), 5.48 (d, J = 7.2 Hz,1H, CH), 6.61
(s, 1H, Ph), 6.62 (d, J = 8.0 Hz, 1H, Ph), 6.76 (d, J = 8.0 Hz, 1H, Ph), 10.99 (s, 1H,
27. Aisha, S.; Aatika, N.; Pasha, M. A. Spectrochim. Acta, Part A 2011, 81, 431.
28. Frisch, M. J. et al Gaussian 09, Revision A. 02; Gaussian: Wallingford CT, 2009.
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30. Lee, C.; Yang, W.; Parr, R. G. Phys. Rev. 1988, B37, 785.