A novel approach toward the synthesis of azetidinones derivatives

Article abstract of DOI:10.1080/17415993.2011.601870

A convenient, efficient and inexpensive procedure for the synthesis of thieno[2,3-b]quinolines was devised. 3-Formyl-2-chloroquinoline 2a on treating with various substituted anilines 3a-e produced N-[(1E)-(2-chloroquinolin-3-yl) methylidene]anilines 4a-e

Full text of DOI:10.1080/17415993.2011.601870

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A novel approach toward the synthesis
of azetidinones derivatives
B. P. Nandeshwarappa a , S. Manjappa a & B. Kishore b
a Department of PG Studies and Research in Analytical Chemistry ,
U.B.D.T. College of Engineering, Davangere University ,
Davangere, Karnataka, 577 004, India
b Shanghai Key Laboratory of Chemical Biology, School of
Pharmacy , East China University of Science and Technology ,
Shanghai, 200 237, People's Republic of China
Published online: 23 Sep 2011.
To cite this article: B. P. Nandeshwarappa , S. Manjappa & B. Kishore (2011) A novel approach
toward the synthesis of azetidinones derivatives, Journal of Sulfur Chemistry, 32:5, 475-481, DOI:
10.1080/17415993.2011.601870
To link to this article: http://dx.doi.org/10.1080/17415993.2011.601870
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Journal of Sulfur Chemistry
Vol. 32, No. 5, October 2011, 475–481
A novel approach toward the synthesis of azetidinones
derivatives
B.P. Nandeshwarappaa*, S. Manjappaa and B. Kishoreb
aDepartment of PG Studies and Research in Analytical Chemistry, U.B.D.T. College of Engineering,
Davangere University, Davangere, Karnataka 577 004, India; bShanghai Key Laboratory of Chemical
Biology, School of Pharmacy, East China University of Science and Technology, Shanghai 200 237, People’s
Republic of China
(Received 8 May 2011; final version received 27 June 2011)
A convenient, efficient and inexpensive procedure for the synthesis of thieno[2,3-b]quinolines was devised.
3-Formyl-2-chloroquinoline 2a on treating with various substituted anilines 3a–e produced N-[(1E)-
(2-chloroquinolin-3-yl)methylidene]anilines 4a–e. The resulted compounds on further treatment with
chloroacetyl chloride gave substituted azetidinones 5a–e. These compounds are easily converted to
thieno[2,3-b]quinolines 6a–e by using sodium sulfide in ethanol. The structures of all the newly synthesized
compounds were elucidated on the basis of elemental analysis, IR, 1H NMR and mass spectral data.
R
N
N
Cl
Cl
O
5a–e (67–78%)
R
Na2S/C2H5OH
a. R=H
b. R=CH3
N
c. R=OCH3
d. R=Cl
O
N
S
e. R=NO2
6a–e (75–85%)
Keywords: azetidinones; 3-formyl-2-chloroquinoline; Schiff base; thieno[2,3-b]quinolines; sulfur
chemistry
1. Introduction
Quinolines and hetero-fused analogs have attracted great attention of medicinal and synthetic
chemists because of their presence in natural products and physiological activities (1). Thieno
*Corresponding author. Email: belakatte@gmail.com, nandu_bp@yahoo.co.in
ISSN 1741-5993 print/ISSN 1741-6000 online
© 2011 Taylor & Francis
http://dx.doi.org/10.1080/17415993.2011.601870
http://www.tandfonline.com

476 B.P. Nandeshwarappa et al.
derivatives are known to exhibit an array of biological activities including analgesic and
anti-inflammatory activities (2–6). It is evident from the literature that thieno derivatives are
well known for their varied biological activities such as high affinity selective 5-HT1A receptor
ligands (7), potential antihypertensive agents (8), molluscicidal and larvicidal activities (9, 10),
anticonvulsant activity (11), antibacterial activity (12), and cholesterol inhibition activity (13, 14).
Substituted 2-azetidinones are an important class of compound for their importance in β-lactam
antibiotic synthesis (15–17). β-Lactam drugs in heterocycles are still the most widely prescribed
antibioticsusedinmedicine(18).Thediscoveryofpenicillin2-azetidinone-basedheterocycleshas
been one of the main classes of drugs with wide therapeutic activities viz. anticonvulsant (19),
anti-inflammatory (20), antibacterial (21), herbicidal (22) and also functioning as an enzyme
inhibitor (23), and they are effective on central nervous system disorders (24).
The conversion of aryl quinolines into thieno[2,3-b]quinolines is of vital importance in synthetic
organic chemistry. Thieno[2,3-b]quinolines are prepared via their corresponding halogenated
derivatives. A survey of the literature reveals that there are numerous methods (25–28) for the
construction of thieno quinolines. Such procedures are obviously accompanied by poor yields,
undesired side products, vigorous reaction conditions, long reaction times, expensive or toxic
reagents and tedious work-up. Therefore, there is still a need to introduce new methods and
inexpensive reagents for such functional group transformations. In this communication, we wish
to report an efficient and inexpensive method for the synthesis of thieno[2,3-b]quinolines starting
fromaneasilyaccessibledichlorosubstratebyareactionwithsodiumsulfideinethanolmediawith
a quantitative yield under remarkably soft conditions.We also determined that the best results were
achieved using sodium sulfide. The constructions of the thieno ring by using Na2S in ethanol media
were proven to be a useful procedure. In continuation of our program directed toward studies on
sulfur chemistry (29–33)and synthesisof new potentiallybioactivemolecules, wewish to examine
thefeasibilityandefficiencyofthisapproachtosynthesizesomenewthieno[2,3-b]quinolines.This
new method fulfills the need for a medicinal, bioorganic, industrial cost-effective and commercial
method for the synthesis of quinoline-based sulfur compounds.
2. Results and discussions
In this contribution, we focus our attention on the fast and efficient synthesis of thieno quinoline
derivatives. Initially, thekeyintermediate3-formyl-2-chloroquinoline 2awaspreparedfromeasily
available acetanilide by the reported method (Scheme 1) (34).
The Schiff bases 4a–e were prepared from compound 2a by reaction with various aromatic
aldehydes 3a–e in the presence of a catalytic amount of acetic acid in absolute ethanol. The IR
spectrum of 4a exhibits an absorption band at 1623.50 cm−1 and the 1H NMR exhibits multiplets
at δ 7.10–8.50 ppm for 10 protons and as imine protons at δ 9.01 ppm confirming its structure.
At the same time, we focussed our attention on the synthesis of azetidinones 5a–e. The com-
pounds 4a–e were made to react with chloro acetyl chloride and triethylamine in dioxane. The
structural analysis of the newly synthesized molecule 5a includes IR, 1H NMR and mass spec-
tral investigations. The IR spectra of the compound revealed sharp strong absorption bands at
1735.81 cm−1 for the azetidinone ring. The 1H NMR spectrum exhibited multiplets in the region
between 7.26 and 8.50 ppm for 10 aromatic protons. The two protons in the azetidinone ring,
− − − −
− −
−
i.e. N CH C and C CH Cl are found to resonate as doublets at δ 4.91 and δ 5.71 ppm,
respectively. The structure was further confirmed by mass spectral studies. It gave a molecular ion
peak at m/z 343 (M+) which corresponds to the molecular formula C18H12Cl2N2O (Scheme 1).
The spectral details for all the synthesized compounds are given in Section 3 and are in agreement
with the assigned structures.

Journal of Sulfur Chemistry 477
O
CH3
H2N
DMF/POCl3
H
+
NH
O
N
Cl
R
1a
3a–e
2a
C2H5OH / H+
R
N
N
Cl
4a–e (70–75%)
ClCOCH2Cl
Triethy amine
R
Dioxane
N
N
Cl
Cl
O
5a–e (67–78%)
R
Na2S/C2H5OH
N
O
N
R = H, CH3, OCH3, Cl, NO2
S
6a–e (75–85%)
Scheme 1. General synthetic procedure for the synthesis of azetidinones derivatives.
Very interestingly, the reactions of 5a–e with sodium sulfide in ethanol underwent ring
cyclization to give thieno quinolines 6a–e. As we expected, the 1H NMR spectrum of 5a exhib-
ited two peaks at δ 4.96 ppm and δ 5.89 ppm for the two protons present in the azetidinone ring
− − − −
− −
−
( N CH C and S CH ). The aromatic protons resonate as multiplets at δ 7.35–8.60 ppm.
The structure was further confirmed by recording its mass spectra. Also, Beilstein’s test confirms
the absence of chlorine.
3. Experimental
IR spectra were taken on a Perkin Elmer 157 Infrared spectrophotometer. The 1H NMR spectra
(300 MHz) were recorded on a Bruker supercon FT NMR instrument using TMS as the internal
standard and mass spectra on a Jeol JMS-D 300 mass spectrometer operating at 70 eV. Melting
points were determined in open capillary tubes and are uncorrected. Purity of the compounds was
checked by TLC on silica gel and they were purified by column chromatography.

478 B.P. Nandeshwarappa et al.
3.1. Preparation of 3-formyl-2-chloroquinoline (4a)
The Vilsmeier reagent was prepared by adding 24 ml (0.031 mol) of N, N-dimethylformamide
to a round-bottom flask in an ice-cold condition (0–5◦C) under constant stirring. To this flask,
36 ml (0.38 mol) of phosphorus oxychloride was added dropwise over a period of half-an-hour
and the resultant mixture was stirred for a further hour. The appropriate acetanilide 1a (1 g) was
then added to the Vilsmeier reagent and stirred for another half-an-hour and the reaction mixture
was refluxed on a water bath for 4–6 h. After the reaction was completed (TLC monitoring),
the reaction mixture was poured onto 500 g of crushed ice under constant manual stirring. After
neutralization with sodium hydroxide solution, the precipitate (80%, 1.52 g) obtained was filtered,
washed well with water, dried and recrystallized using ethyl acetate.
3.2. Preparation of Schiff base (4a)
3-Formyl-2-chloroquinoline 2a (0.01 mol), aniline (0.01 mol) 3a and a catalytic amount of acetic
acid were taken in ethanol (20 ml) and heated to reflux for 3–4 h. After the completion of the
reaction (TLC), the reaction mixture was poured onto crushed ice; the solid mass thus separated
out was filtered, washed with water and dried to give the desired compound 4a. Similarly, the
compounds 4b–e were prepared in 70–75% yields.
3.2.1. N-[(1E)-(2-Chloroquinolin-3-yl)methylidene]aniline (4a)
1
Solid, 73%; mp 186◦C; H NMR (300 MHz, DMSO-d6) δ (ppm): 7.10–8.50 (10H, m, Ar-H),
9.01 (1H, s, N = CH); IR (KBr) ν (cm−1): 1623.50. [M+], 266. Calcd. (%) for C16H11ClN2: C,
−
72.05; H, 4.16; N, 10.50. Found: C, 72.35; H, 4.27; N, 10.37.
3.2.2. N-[(1E)-(2-Chloroquinolin-3-yl)methylidene]-4-methylaniline (4b)
Solid, 73%; mp 194◦C; 1H NMR (300 MHz, DMSO-d6) δ (ppm): 2.60 (3H, s, CH3), 7.12–8.60
(9H, m, Ar-H); 9.03 (1H, s, N = CH), IR (KBr) ν (cm−1): 1622.60. [M+], 280. Calcd. (%) for
−
C17H13ClN2: C, 72.73; H, 4.67; N, 9.98. Found: C, 72.54; H, 4.43; N, 9.77.
3.2.3. N-[(1E)-(2-Chloroquinolin-3-yl)methylidene]-4-methoxyaniline (4c)
◦
1
−
Solid, 75%; mp 175 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 3.94 (3H, s, OCH3), 7.13–
8.45 (9H, m, Ar-H); 9.02 (1H, s, N = CH), IR (KBr) ν (cm−1): 1623.50. [M+], 296. Calcd. (%)
−
for C17H13ClN2O: C, 68.81; H, 4.42; N, 9.44. Found: C, 68.58; H, 4.37; N, 9.18.
3.2.4. 4-Chloro-N-[(1E)-(2-chloroquinolin-3-yl)methylidene]aniline (4d)
Solid, 71%; mp 204◦C; 1H NMR (300 MHz, DMSO-d6) δ (ppm): 7.25–8.65 (9H, m, Ar-H); 9.03
(1H, s, N = CH), IR (KBr) ν (cm−1): 1622.70. [M+], 301. Calcd. (%) for C16H10Cl2N2: C,
−
63.81; H, 3.35; N, 9.30. Found: C, 63.52; H, 3.49; N, 9.17.
3.2.5. N-[(1E)-(2-Chloroquinolin-3-yl)methylidene]-4-nitroaniline (4e)
Solid, 70%; mp 215◦C; 1H NMR (300 MHz, DMSO-d6) δ (ppm): 7.26–8.48 (9H, m, Ar-H); 9.04
(1H, s, N = CH), IR (KBr) ν (cm−1): 1622.90. [M+], 311. Calcd. (%) for C16H10ClN3O2:
−
C, 61.65; H, 3.23; N, 13.48. Found: C, 61.45; H, 3.34; N, 13.36.

Journal of Sulfur Chemistry 479
3.3. Preparation of azetidinones (5a)
In a typical example, triethyl amine (0.01 mol) in 5 ml of dioxane was added to chloroacetyl
chloride (0.01 mol) in 5 ml of dioxane cooled to 0◦C. To this mixture, Schiff’s base 4a (0.01 mol)
in 5 ml of dioxane was added and refluxed for 6 h. After the completion (monitored by TLC),
the reaction mixture was poured onto ice-cold water to give a solid, which was filtered and
dried. This crude product was purified by column chromatography on silica gel (eluent: ethyl
acetate:petroleum ether). Similarly, the compounds 5b–e were prepared in 67–78% yields.
3.3.1. 3-Chloro-4-(2-chloroquinolin-3-yl)-1-phenylazetidin-2-one (5a)
◦
1
− −
−
Solid, 70%; mp 219 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 4.91 (1H, s, N CH C),
5.71 (1H, s, Cl CH C = O), 7.26–8.50 (10H, m, Ar-H); IR (KBr) ν (cm−1): 1735.81 (C = O
azetidinone), [M+], 343. Calcd. (%) for C18H12Cl2N2O: C, 62.99; H, 3.52; N, 8.16. Found: C,
62.88; H, 3.64; N, 8.41.
−
−
3.3.2. 3-Chloro-4-(2-chloroquinolin-3-yl)-1-(4-methylphenyl)azetidin-2-one (5b)
◦
1
−
Solid, 73%; mp 210 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 2.60 (3H, s, CH3), 4.87 (1H,
s, N CH C), 5.89 (1H, s, Cl CH C = O), 7.20–8.49 (9H, m, Ar-H); IR (KBr) ν (cm−1):
1735.61 (C = O azetidinone), [M+], 357. Calcd. (%) for C19H14Cl2N2O: C, 63.88; H, 3.95; N,
7.84. Found: C, 63.78; H, 3.85; N, 7.62.
− −
−
−
−
3.3.3. 3-Chloro-4-(2-chloroquinolin-3-yl)-1-(4-methoxyphenyl)azetidin-2-one (5c)
◦
1
−
Solid, 78%; mp 229 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 3.90 (3H, s, OCH3), 4.92 (1H,
s, N CH C), 5.79 (1H, s, Cl CH C = O), 7.23–8.42 (9H, m, Ar-H); IR (KBr) ν (cm−1):
1738.61 (C = O azetidinone), [M+], 377. Calcd. (%) for C19H14Cl2N2O2: C, 61.14; H, 3.78; N,
7.51. Found: C, 61.24; H, 3.49; N, 7.39.
− −
−
−
−
3.3.4. 3-Chloro-1-(4-chlorophenyl)-4-(2-chloroquinolin-3-yl)-1-(4-methoxyphenyl)azetidin-2-
one (5d)
◦
1
− −
−
Solid, 67%; mp 235 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 4.79 (1H, s, N CH C),
5.70 (1H, s, Cl CH C = O), 7.29–8.55 (9H, m, Ar-H); IR (KBr) ν (cm−1): 1738.41 (C = O
azetidinone), [M+], 373. Calcd. (%) for C18H11Cl3N2O: C, 57.25; H, 2.94; N, 7.42. Found: C,
57.39; H, 2.83; N, 7.29.
−
−
3.3.5. 3-Chloro-4-(2-chloroquinolin-3-yl)-1-(4-nitrophenyl)azetidin-2-one (5e)
◦
1
− −
−
Solid, 78%; mp 245 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 4.70 (1H, s, N CH C),
5.68 (1H, s, Cl CH C = O), 7.34–8.60 (9H, m, Ar-H), IR (KBr) ν (cm−1): 1738.47 (C = O
azetidinone), [M+], 388. Calcd. (%) for C18H11Cl2N3O3: C, 55.69; H, 2.86; N, 10.82. Found: C,
55.58; H, 2.68; N, 10.69.
−
−
−
3.4. Preparation of thieno quinolines (6a)
A mixture of azetidinones 4a (0.01 mol) and sodium sulfide (0.01 mol) was refluxed for 10 min on
a water bath in ethanol (50 ml). The compound 5a precipitated out as a yellow crystalline solid.

480 B.P. Nandeshwarappa et al.
The mixture was poured onto cold water (500 ml); the resulting solid product 5a was collected
by filtration, washed with ethanol, dried and recrystallized from ethyl acetate. Similarly, the
compounds 4b–e were prepared in 75–85% yields.
3.4.1. 1-Phenyl-2a, 7b-dihydroazeto[2ꢀ,3ꢀ:4,5]thieno[2,3-b]quinoline (6a)
◦
1
− −
−
Solid, 77%; mp 238 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 4.96 (1H, s, N CH C), 5.89
(1H, s, S CH ), 7.35–8.60 (9H, m, Ar-H); IR (KBr) ν (cm−1): 1735.78 (C = O azetidinone),
[M+], 304. Calcd. (%) for C18H12N2OS: C, 71.03; H, 3.97; N, 9.20; S, 10.54. Found: C, 71.23;
H, 3.83; N, 9.40; S, 10.72.
− −
−
3.4.2. 1-(4-Methylphenyl)-2a,7b-dihydroazeto[2ꢀ,3ꢀ:4,5]thieno[2,3-b]quinoline (6b)
◦
1
−
Solid, 80%; mp 242 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 2.60 (3H, s, CH3), 4.85 (1H,
s, N CH C), 5.78 (1H, s, S CH ), 7.37–8.50 (9H, m, Ar-H); IR (KBr) ν (cm−1): 1735.66
(C = O azetidinone), [M+], 318. Calcd. (%) for C19H14N2OS: C, 71.67; H, 4.43; N, 8.80; S,
10.07. Found: C, 71.49; H, 3.27; N, 8.69; S, 10.19.
− −
−
− −
−
3.4.3. 1-(4-Methoxyphenyl)-2a,7b-dihydroazeto[2ꢀ,3ꢀ:4,5]thieno[2,3-b]quinoline (6c)
◦
1
−
Solid, 85%; mp 269 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 3.90 (3H, s, OCH3), 4.85
(1H, s, N CH C), 5.68 (1H, s, S CH ), 7.29–8.45 (9H, m, Ar-H); IR (KBr) ν (cm−1):
1738.64 (C = O azetidinone), [M+], 334. Calcd. (%) for C19H14N2O2S: C, 68.24; H, 4.22; N,
8.38; S, 9.59. Found: 68.12, H, 4.39; N, 8.26; S, 9.44.
− −
−
− −
−
3.4.4. 1-(4-Chlorophenyl)-2a, 7b-dihydroazeto[2ꢀ,3ꢀ:4,5]thieno[2,3-b]quinoline (6d)
◦
1
− −
−
Solid, 78%; mp 275 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 4.80 (1H, s, N CH C), 5.73
(1H, s, S CH ), 7.34–8.55 (9H, m, Ar-H); IR (KBr) ν (cm−1): 1738.61 (C = O azetidinone),
[M+], 338. Calcd. (%) for C18H11ClN2OS: C, 63.81; H, 3.27; N, 8.27; S, 9.46. Found: C, 63.69;
H, 3.12; N, 8.15; S, 9.34.
− −
−
3.4.5. 1-(4-Nitrophenyl)-2a,7b-dihydroazeto[2ꢀ,3ꢀ:4,5]thieno[2,3-b]quinoline (6e)
◦
1
− −
−
Solid, (75%); mp. 285 C; H NMR (300 MHz, DMSO-d6) δ (ppm): 4.68 (1H, s, N CH C),
5.70 (1H, s, S CH ), 7.30–8.60 (9H, m, Ar-H). IR (KBr) ν (cm−1): 1738.64 (C = O azetidi-
none), [M+], 349. Calcd. (%) for C18H11N3O3S: C, 61.88; H, 3.17; N, 12.03; S, 9.18. Found: C,
61.74; H, 3.34; N, 12.24; S, 9.36.
− −
−
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