The synthesis and antimicrobial screening of some novel aza-imidoxy compounds as potential chemotherapeutic agents

Article abstract of DOI:10.1080/10426500500366970

Some novel azaimidoxy compounds viz. 2-{[(4-chlorophenyl)diazenyl]oxy}-1H -isoindole-1,3-(2H )-dione (Va), and 1-{[1-naphthyldiazenyl]oxy}pyrrolidine-2,5- dione (IVc), etc. have been synthesized by a simple diazotization reaction followed by a coupling with 2-hydroxy-1H -isoindole-1,3(2H )-dione (III)/1-hydroxypyrrolidine-2,5-dione (II) of corresponding aromatic primary amine derivatives at a suitable pH. A similar reaction with a [1,3]thiazolo[4,5- b ]pyridin-2-amine (VIII) lead us to some interesting results variable with a pH. The structure of all synthesized compounds has been established by IR, 1H NMR, and mass studies. These compounds have been screened for antimicrobial activities in order to evaluate the possibility of the derivatives to be used as potential chemotherapeutic agents. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/10426500500366970

Phosphorus, Sulfur, and Silicon, 181:1665–1673, 2006
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500500366970
The Synthesis and Antimicrobial Screening of Some
Novel Aza-Imidoxy Compounds as Potential
Chemotherapeutic Agents
Shilpi Jain
Devendra Prakash Nagda
G. L. Talesara
Department of Chemistry, M. L. Sukhadia University, Udaipur, India
Some novel azaimidoxy compounds viz. 2-{[(4-chlorophenyl)diazenyl]oxy}-1H-
isoindole-1,3-(2H)-dione (Va), and 1-{[1-naphthyldiazenyl]oxy}pyrrolidine-2,5-
dione (IVc), etc. have been synthesized by a simple diazotization reaction followed by
a coupling with 2-hydroxy-1H-isoindole-1,3(2H)-dione (III)/1-hydroxypyrrolidine-
2,5-dione (II) of corresponding aromatic primary amine derivatives at a suitable
pH. A similar reaction with a [1,3]thiazolo[4,5-b]pyridin-2-amine (VIII) lead us to
some interesting results variable with a pH. The structure of all synthesized com-
1
pounds has been established by IR, H NMR, and mass studies. These compounds
have been screened for antimicrobial activities in order to evaluate the possibility
of the derivatives to be used as potential chemotherapeutic agents.
Keywords Antimicrobial activities; azaimidoxy; coupling; diazotization; pH;
spectral studies
INTRODUCTION
Azoxy derivatives form a very interesting class of compounds because
of their significant biological (antibacterial, anticancer, antitubercu-
lous, and nematocidal) activities,1 and their chemistry is consequently
now receiving considerable attention. Azoxybacilin,2 an unusual amino
acid with an azoxy moiety, is active against a broad spectrum of
fungi, especially against mycelial fungi, such as Aspergillus. Similarly,
Received July 14, 2005; accepted August 29, 2005.
The authors are thankful to Head, Department of Chemistry, M. L. Sukahdia Univer-
sity, Udaipur, India, for providing the necessary laboratory facilities and the Microbial
Laboratory, Department of Botany, M. L. Sukahdia University, Udaipur, India, for the
antimicrobial evaluation; and Director, CDRI, Lucknow, for spectral measurements and
elemental analysis. Dr. Nagda is thankful to CSIR, New Delhi, for necessary financial
assistance.
Address correspondence to G. L. Talesara, M. L. Sukhadia University, Department of
Chemistry, Udaipur, (Raj.) 313001, India. E-mail: gtalesara@yahoo.com
1665

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S. Jain et al.
valanimycin, which is a naturally occurring azoxy compound, shows
good antibiotic and antibacterial activity. In addition to this, valan-
imycin also exhibits potent antitumor activity against in vitro cell cul-
tures of mouse leukemia L1210, P388/S, and P388/ADR.3−9 As part of
our studies aimed at the simple and efficient synthesis of heterocyclic
compounds possessing phthalimidoxy, imidoxy, or aminooxy moieties,
and in continuation of our work,10−13 it seemed interesting to synthe-
size some novel azoxy compounds associated with a imidoxy moiety. In
this article, we report the synthesis of novel azaimidoxy compounds of
aromatic amines, and sulfur-containing five-membered fused hetero-
cyclic system, and the confirmation of structures of resulting products
by spectroscopic data. The newly synthesized azamidoxy compounds
appear to be a promising substrate for biological activity evaluation.
RESULTS AND DISCUSSION
All the synthesized compounds are well supported by their spectral
data.
In the present investigation, the diazotization of primary aromatic
amines (I) was carried out with NaNO2 and HCl at 0–5◦C, then a di-
azotized product was coupled with imidoxy [2-hydroxy-1H-isoindole-
1,3(2H)-dione (III)/1-hydroxypyrrolidine-2,5-dione (II)] compounds be-
tween 4–5 pH. The coupled compound was characterized by the absence
of a NH2 peak at 3450–3560 cm−1 and a OH peak at 2700–3300 cm−1 in
IR spectra, which was present in a precursor primary aromatic amine
and imidoxy compound, respectively. The product was also confirmed
by the absence of a NH2 peak at δ 4–5 in 1H NMR spectra (Scheme 1).
In order to synthesize sulfur-containing five-membered fused aro-
matic heterocyclic azaimidoxy compounds, the diazotization and cou-
pling reaction of [1,3]thiazolo[4,5-b]pyridine-2-amine (VIII) has been
carried out (Scheme 2). It was prepared by a cyclization reaction of 1-
pyridin-2-ylthiourea (VII) in the presence of a Br2 and CHCl3 and was
confirmed by the presence of a C N peak at 1646 cm−1 in its IR spec-
trum. [1,3]thiazolo[4,5-b]pyridin-2-amine (VIII) was also diazotized by
its reaction with NaNO2 and HCl at 0–5◦C, but unlike primary aromatic
amines, its coupling reaction did not occur in an acidic pH. During its di-
azotization and coupling reaction with imidoxy compounds, many inter-
esting and important product variations have been obtained (Table 1)
when the pH of a reaction was modified. Various results at different pH
are discussed:
1. A coupled product was never obtained in an acidic pH.
2. A coupled azaimidoxy product was obtained when the pH was main-
tained between 8–10.

Novel Aza-imidoxy Compounds
1667
SCHEME 1
SCHEME 2

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S. Jain et al.
TABLE I Spectral Characterization
Coupled product obtained at
pH 8–10
Product obtained at pH 10–12
1. Due to the chromophoric
effect of N N group, UV
obtain at higher wavelength,
i.e., 435 nm.
1. A UV band was obtained at
lower wavelength, i.e.,
340 nm.
2. An IR peak of N N group
2. An IR peak of N N was not
obtained.
was obtain at 1566 cm−1
.
3. A diazonium fragment peak
at 163 was obtained in mass
spectra.
3. A diazonium fragment peak
was absent.
3. Above pH 8–10, a normal coupled aza compound was obtained with
the evolution of N2.
4. In a highly basic medium, the thiazole ring breaks with the evolution
of N2, and colloidal sulfur precipitates out.
Lastly, the presence of a C O peak at 1700–1711 cm−1 and the absence
of an OH peak at 2700–3300 cm−1 also confirmed the formation of the
final compounds. 2-hydroxy-1H-isoindole-1,3(2H)-dione has been pre-
pared by the reported method,14 while 1-hydroxypyrrolidine-2,5-dione
has been purchased by commercial resources.
ANTIMICROBIAL SCREENING
All synthesized azaimidoxy compounds were screened for their antibac-
terial and antifungal activities using amicacin and flucanazole, respec-
tively, as reference compounds. The test organisms used for antibacte-
rial studies were Escherichia coli, Proteus vulgaris, Klebsiella pneumo-
nia, Pseudomonas aeruginosa, and Staphylococcus aureus. Aspergillus
fumigatus and Candida albicans were used for antifungal studies. The
cup or well method developed by Collee and colleagues15 has been fol-
lowed. The results have been tabulated in the form of inhibition zones
and activity index (Table II). Although all the compounds show less

Novel Aza-imidoxy Compounds
1669
TABLE II The Results of Antimicrobial Studies of Azaimidoxy
Compounds. Zone of Growth Inhbition (mm) (Activity Index)#
Antifungal activity
Antibacterial activity (300 µg/mL)
Org. I
Org. II
Compound
no.
Org. I Org.II Org.III Org. IV Org. V 50 ppm 100 ppm 50 ppm 100 ppm
IVa
IVb
IVc
IVd
Va
Vb
Vc
Vd
IX
13(0.61) 20(1.00) 19(0.82) 13(0.61) 8(0.34) 18(1.28) 26(1.18) 16(1.33) 20(1.25)
12(0.57) 12(0.60) 14(0.60) 15(0.71) 13(0.56) 14(1.00) 19(0.86) 12(1.00) 17(1.06)
15(0.71) 5(0.25) 15(0.65) 4(0.19) 4(0.17) 13(0.92) 23(1.04) 12(1.00) 16(1.00)
10(0.47) 15(0.75) 8(0.34) 16(0.76) 15(0.65) 16(1.14) 21(0.95) 10(0.83) 12(0.75)
12(0.57) 15(0.75) 9(0.39) 18(0.85) 7(0.30) 16(1.14) 23(1.04) 12(1.00) 14(0.87)
13(0.61) 18(0.90) 17(0.73) 17(0.80) 6(0.26) 18(1.28) 20(0.90) 11(0.91) 15(0.93)
12(0.57) 9(0.45) 15(0.65) 6(0.28) 14(0.60) 17(1.21) 23(1.04) 10(0.83) 14(0.87)
14(0.66) 13(0.65) 14(0.60) 9(0.42) 15(0.65) 15(1.07) 19(0.86) 12(1.00) 17(1.06)
9(0.42) 6(0.30) 8(0.34) 8(0.38) 18(0.78) 18(1.28) 23(1.04) 14(1.16) 16(1.00)
13(0.61) 12(0.60) 7(0.30) 8(0.38) 16(0.69) 17(1.21) 22(1.00) 16(1.33) 20(1.25)
X
Standard
21
20
23
21
23
14
22
12
16
#(Activity index)-Inhibition zone of the sample/Inhibition zone of the standard.
For antibacterial activity, Org. I = Escherichia coli, Org. II = Staphylococcus aureus,
Org. III = Proteus vulgaris, Org. IV = Klebsiella pneumonia, and Org. V =
Pseudomonas aeruginosa. Standard used = Amicacin.
For antifungal activity, Org. I = Aspergillus fumigatus and Org. II = Candida
albicans. Standard used = Fluconazole.
to moderate activity against bacteria but possess very strong activ-
ity against fungi, which reveals that azaimidoxy compounds are better
antifungal agents as compared to antibacterial.
EXPERIMENTAL
Melting points of all synthesized compounds were determined in an
open capillary tube and are uncorrected. IR spectra (KBr) and 1H NMR
spectra (CDCl3) were recorded on a Perkin-Elmer 1800 spectrophotome-
ter and DRX-300 (300 MHz) spectrophotometer using TMS as an inter-
nal standard, respectively, and mass spectra were recorded on a Jeol
SX-102 (FAB) spectrometer. The purity of compounds was checked by
elemental analysis and also by TLC using silica gel “G” as an adsorbent,
and visualization was accomplished by iodine.
The Synthesis of 2-{[(4-Chlorophenyl)diazenyl]oxy}-1H-
isoindole-1,3-(2H)-dione (Va)
4-chloroaniline (0.01 mole) was dissolved in 5N HCl and cooled. An
ice-cold solution of NaNO2 (0.01 mole) in water was added gradually,

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S. Jain et al.
maintaining a temperature between 0–5◦C. A cooled solution of 2-
hydroxy-1H-isoindole-1,3(2H)-dione in diluted NaOH was added to a
diazotized reaction mixture between 0–5◦C and a pH between 4–5. The
reaction mixture was stirred on a water bath for some time, and a
resulting solid was filtered, washed with ethanol, and recrystallised
from benzene. Yield (80%), m.p. 214◦C (found: N, 13.80 C14H8N3O3Cl
requires:13.93; νmax : 3104 (Ar H), 1736 (CO N CO), 1133 (N O),
1539 (N N), 710 (C Cl) cm−1; δ(ppm): 7.2–7.4 (8H, m, ArH); m/z (%):
301 (27.3) [M+.], 162 (12.2), 155 (100), 146 (25.5), 139 (45.1), 111 (59.0).
Other compounds (Vb–Vd) were also synthesized in a similar way
with a slight variation in the concentration of HCl required to dissolve
the substituted aniline.
2-{[(4-Methylphenyl)diazenyl]oxy}-1H-isoindole-1,
3-(2H)-dione (Vb)
Yield (75%), m.p. 162◦C (found: N, 14.80 C15H11N3O3 requires:
14.94%);νmax : 3090 (Ar H), 2973 (CH3), 1730 (CO N CO), 1120
(N O), 1520 (N N) cm−1; δ: 7.0–7.3 (8H, m, ArH), 2.4 (3H, s, CH3);
m/z (%): 281 (22.7) [M+.], 162 (11.9), 146 (20.8), 135 (100), 119 (32.5),
91 (39.9).
2-{[1-Naphthyldiazenyl]oxy}-1H-isoindole-1,3-(2H)-dione (Vc)
Yield (62%), m.p. 181◦C (found: N, 13.15 C18H11N3O3 requires:13.24%);
νmax: 3088 (Ar H), 1725 (CO N CO), 1123 (N O), 1524 (N N) cm−1
;
δ: 7.0–7.2 (8H, m, ArH); m/z (%): 317 (30.2) [M+.], 171 (100), 162 (13.4),
155 (32.2), 146 (22.7), 127 (52.3).
2-{[(4-Nitrophenyl)diazenyl]oxy}-1H-isoindole-1,3-
(2H)-dione (Vd)
Yield (64%), m.p. 155◦C (found: N, 17.88 C14H8N4O5 requires:
17.92%);νmax : 3106 (Ar H), 1740 (CO N CO), 1540 and 1350 (NO2),
1140 (N O), 1542 (N N) cm−1; δ (8.1 (2H, d, Ar H near NO2), 7.2 (6H,
m, ArH); m/z (%): 312 (35.9) [M+.], 166 (100), 162 (16.6), 150 (41.6), 146
(20.9), 122 (60.1).
Compounds (IVa–IVd) were synthesized similarly like (Va), but 1-
hydroxypyrrolidine-2,5-dione(II) was used instead of 2-hydroxy-1H-
isoindole-1,3(2H)-dione(III).
1-{[(4-Chlorophenyl)diazenyl]oxy}pyrrolidine-2,5-dione (IVa)
Yield (74%), m.p. 194◦C (found: N, 14.82 C10H8N3O3Cl requires:
14.92%);νmax : 3020 (Ar H), 2890 (CH2), 1705 (CO N CO), 1072

Novel Aza-imidoxy Compounds
1671
(N O), 1560 (N N), 720 (C Cl) cm−1; δ: 7.2–7.4 (4H, m, ArH), 2.2 (4H,
s, CH2); m/z (%): 253 (32.9) [M+.], 155 (100), 139 (41.9), 114 (15.7), 111
(64.2), 98 (20.2).
1-{[(4-Methylphenyl)diazenyl]oxy}pyrrolidine-2,5-dione (IVb)
Yield (70%), m.p. 178◦C (found: N, 17.85 C11H11N3O3 requires:18.02%);
νmax : 3010 (Ar H), 2970 (CH3), 2880 (CH2), 1689 (CO N CO), 1020
(N O), 1540 (N N) cm−1; δ: 7.1 (4H, m, ArH), 2.6 (3H, s, CH3), 2.2 (4H,
s, CH2); m/z (%): 233 (27.6) [M+.], 135 (100), 119 (41.4), 114 (20.2), 98
(26.2), 91 (44.9).
1-{[1-Naphthyldiazenyl]oxy}pyrrolidine-2,5-dione (IVc)
Yield (62%), m.p. 220◦C (found: N, 14.02 C14H11N3O3 requires. 14.12%)
νmax: 3015 (Ar H), 2885 (CH2), 1700 (CO N CO), 1040 (N O), 1550
(N N) cm−1; δ: 7.1–7.2 (7H, m, ArH), 2.1 (4H, s, CH2); m/z (%): 269
(34.3) [M+.], 171 (100), 155 (21.5), 127 (39.7), 114 (12.8), 98 (20.9).
1-{[(4-Nitrophenyl)diazenyl]oxy}pyrrolidine-2,5-dione (IVd)
Yield (60%), m.p. 174◦C (found: N, 20.04 C10H8N4O5 requires: 21.21%);
νmax : 3040 (Ar H), 2890 (CH2), 1720 (CO N CO), 1520 and 1310
(NO2), 1060 (N O), 1560 (N N) cm−1; δ (ppm): 8.0 (4H, m, ArH), 2.3
(4H, s, CH2); m/z (%): 264 (22.3) [M+.], 166 (100), 150 (35.6), 122 (57.9),
114 (11.4), 98 (21.9).
The Synthesis of 1-Pyridin-2-ylthiourea (VII)
2-Amino pyridine (0.01 mole) was dissolved in 1N HCl, and ammonium
thiocaynate was added with stirring. The reaction mixture was refluxed
for 6 h, and an excess of solvent was removed by reduced pressure.
A yellow brown solid obtained was recrystallised from alcohol. Yield
(64%), m.p. 182◦C (found: N, 27.12 C6H7N3S requires: 27.43%); νmax
:
3380 (NH2), 3312 (NH), 3010 (Ar H), 1664 (C N), 1580, 1500 (C C),
1262 (C N), 1212 (C S) cm−1; δ (ppm): 7.3 (4H, m, ArH), 7.8 (1H, s,
NH), 7.2 (2H, s, NH2); m/z (%): 153 (42.3) [M+.], 136 (100), 78 (35.9).
The Synthesis of [1,3]thiazolo[4,5-b]pyridin-2-amine (VIII)
1-Pyridine-2-ylthiourea (0.01 mole) in CHCl3 was cyclized in the pres-
ence of Br2 in CHCl3 via refluxing on a water bath for 8–10 h. The
solvent was removed under reduced pressure, thus, a yellow solid ob-
tained was recrystallized from a chloroform methanol mixture. Yield
(57%), m.p. 228◦C (found: N, 27.62 C5H5N3S requires: 27.79%); νmax
:

1672
S. Jain et al.
3410 (NH2), 3016 (Ar H), 1646 (C N), 1586 (C C), 1268 (C N), 850
(C S C) cm−1; δ: 7.7 (2H, s, NH2), 7.2 (3H, m, ArH); m/z (%): 151 (31.4)
[M+.], 135 (100), 103 (65.8), 77 (42.7).
The Synthesis of 2-{[[1,3]thiazolo[4,5-b]pyridin-2-
yldiazenyl]oxy}-1H-isoindole-1,3(2H)-dione (IX)
[1,3]thiazolo[5,4-b]pyridine-2-amine (0.01 mole) was dissolved in dil
HCl. An ice-cold solution of NaNO2 (0.01 mole) in water was added
gradually, maintaining temperature between 0–5◦C. A cooled solution
of 2-hydroxy-1H-isoindole-1,3(2H)-dione in diluted NaOH was added
to a diazotized reaction mixture between 0–5◦C and pH between 8–10.
The reaction mixture was kept for some time, and a resulting solid was
filtered. An orange solid obtained was recrystallized from CHCl3. Yield
(52%), m.p. > 300◦C (found: N, 21.42 C14H7N5O3S requires: 21.53%);
νmax: 3069 (Ar H), 1711 (C O), 1646 (C N), 1566 (N N), 1088 (N O)
cm−1; δ: 7.2–7.4 (7H, m, ArH); m/z (%): 325 (15.9) [M+.], 179 (100), 163
(35.6), 146 (22.3), 135 (52.4), 77 (15.7).
1-{[[1,3]Thiazolo[4,5-b]pyridin-2-yldiazenyl]oxy}-
Pyrrolidine-2,5-dione (X)
It is synthesized in similar manner in which compound (IX) was syn-
thesized but 1-hydroxypyrrolidine-2,5-dione(II) was used for coupling
instead of 2-hydroxy-1H-isoindole-1,3(2H)-dione(III). Yield (55%), m.p.
> 300◦C (found: N, 25.90 C10H7N5O3S requires: 25.23%); νmax: 3062
(Ar H), 2880 (CH2), 1700 (C O), 1675 (C N), 1565 (N N), 1020 (N O)
cm−1; δ: 7.3 (3H, m, ArH), 2.3 (4H, s, CH2); m/z (%): 277 (28.1) [M+.],
179 (100), 163 (31.8), 135 (47.3), 98 (25.7), 77 (20.7).
2-([1,3]Thiazolo[4,5-b]pyridin-2-yloxy)-1H-isoindole-
1,3(2H)-dione (XI)
Prepared similarly as compound (IX) with a slight change in pH, i.e., be-
tween pH 10–12. Yield (42%), m.p. 273◦C (found: N, 13.80 C14H7N3O3S
requires: 14.13%); νmax : 3060 (Ar H), 1710 (C O), 1640 (C N), 1082
(N O) cm−1; δ: 7.2 (7H, m, ArH); m/z (%): 297 (32.9) [M+.], 151 (100),
135 (58.6), 146 (32.9), 77 (18.9).
1-([1,3]Thiazolo[4,5-b]pyridin-2-yloxy)pyrrolidine-2,5-
dione (XII)
Prepared similarly as compound (X) with a slight change in pH, i.e. be-
tween pH 10–12. Yield (51%), m.p. 254◦C (found: N, 16.65 C10H7N3O3S
requires: 16.86%); νmax : 3052 (Ar H), 2884 (CH2), 1710 (C O), 1645

Novel Aza-imidoxy Compounds
1673
(C N), 1073 (N O) cm−1; δ: 7.2 (3H, m, ArH), 2.2 (4H, s, CH2); m/z (%):
249 (25.8) [M+.], 151 (100), 135 (40.9), 98 (28.7), 77 (19.6).
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