Green synthesis of 1-(1,2,4-Triazol-4-yl)spiro[azetidine-2,3′-(3 H)indole]-2′,4′(1′ H)-diones as potential insecticidal agents

Article abstract of DOI:10.1002/jhet.1071

One pot green synthesis of 1-(1,2,4-triazol-4-yl)spiro[azetidine-2, 3′-(3H)-indole]-2′,4′(1′H)-diones was carried out by the reaction of indole-2,3-diones,4-amino-4H-1,2,4-triazole and acetyl chloride/chloroacetyl chloride in ionic liquid [bmim]PF₆ with/without using a catalyst. It was also prepared by conventional method via Schiff's bases, 3-[4H-1,2,4-triazol-4-yl]imino-indol-2-one. Further, the corresponding phenoxy derivatives were obtained by the reaction of chloro group attached to azetidine ring with phenols. The synthesized compounds were characterized by analytical and spectral (IR, ¹H NMR, ¹³C NMR, and FAB mass) data. Evaluation for insecticidal activity against Periplaneta americana exhibited promising results.

Full text of DOI:10.1002/jhet.1071

March 2013
Green Synthesis of 1-(1,2,4-Triazol-4-yl)spiro[azetidine-2,30-
315
(3H)indole]-20,40(10H)-diones as Potential Insecticidal Agents
*
Renuka Jain, Kanti Sharma, and Deepak Kumar
Department of Chemistry, University of Rajasthan, Jaipur 302 004, India
*
E-mail: profrjain@rediffmail.com
Received April 11, 2011
DOI 10.1002/jhet.1071
Published online 8 April 2013 in Wiley Online Library (wileyonlinelibrary.com).
One pot green synthesis of 1-(1,2,4-triazol-4-yl)spiro[azetidine-2,30-(3H)-indole]-20,40(10H)-diones was
carried out by the reaction of indole-2,3-diones,4-amino-4H-1,2,4-triazole and acetyl chloride/chloroacetyl
chloride in ionic liquid [bmim]PF6 with/without using a catalyst. It was also prepared by conventional method
via Schiff’s bases, 3-[4H-1,2,4-triazol-4-yl]imino-indol-2-one. Further, the corresponding phenoxy derivatives
were obtained by the reaction of chloro group attached to azetidine ring with phenols. The synthesized
1
compounds were characterized by analytical and spectral (IR, H NMR, 13C NMR, and FAB mass) data.
Evaluation for insecticidal activity against Periplaneta americana exhibited promising results.
J. Heterocyclic Chem., 50, 315 (2013).
INTRODUCTION
at room temperature have emerged. These have unique
properties such as wide liquid range, good solvency,
tunable polarity, high thermal stability, negligible vapor
pressure, and ease of recyclability and hence can be reused
as opposed to the traditional solvent catalyst systems.
Although few references [14–16] regarding synthesis of
azetidinone derivatives in ionic liquid are available but
synthesis of spiro [azetidine–indole] system in ionic liquid
has not been reported.
With a view to develop an efficient, economical, and
extremely fast procedure using green chemistry concept
1-(1,2,4-triazol-4-yl)spiro[azetidine-2,30-[3H]indole]-20-40
(10H)-diones 4 and 5 were synthesized by the reaction of
indole-2,3-diones 1, 4-amino-4H-1,2,4-triazole 2 and ace-
tyl chloride/chloroacetylchloride in ionic liquid [bmim]
PF6 with or without using catalyst for the first time by
the authors. Simultaneously, these were also prepared by
conventional method via Schiff’s bases [13,17], 3-[4H-
1,2,4-triazol-4-yl]-imino-indol-2-one 3 obtained by the
reaction of 1 and 2. In the second step, 3 were reacted with
acetyl chloride/chloroacetylchloride to give 4 and 5. Alter-
natively, the title compounds 4 and 5 have also been
prepared without isolating the Schiff’s bases and cyclized
in situ with acetyl chloride/chloro acetyl chloride.
Heterocyclic scaffolds represent the central frame work of
many biologically active compounds. Among the various
heterocyclic systems, indole holds a prominent position
because of its presence as a core unit in a number of
compounds possessing broad spectrum of biological activi-
ties [1]. Indole-2,3-dione derivatives act as anticancer [2]
and antihistaminic agents [3]. 1,2,4-Triazole with an extra
nitrogen atom behaves like pyridine so weakly basic and is
important as it is the basis of best modern agricultural fungi-
cides [4] as well as drugs for fungal diseases in humans. A
recent example of this is Pfizer’s fluconazole, the Schiff’s
base with isatin, which exhibits antimicrobial activity [5].
b-Lactams (azetidinones) are the key components of many
biologically active compounds such as penicillin and cepha-
losporin antibiotics [6–8] and show antibacterial [9], antifun-
gal [9], and anti-inflammatory [10] activities. These are also
used to inhibit cholesterol absorption [11].
The chemistry of spiro indoles in which an indole ring is
joined to nitrogen containing heterocycles at C-3 position
through a spiro carbon atom has aroused great interest due
to their physiological and biological activities [10]. Amongst
these spiro[azetidine-indole] are known to possess antimicro-
bial activity [12,13]. It was therefore, presumed that the title
molecules incorporating indole, azetidinone, and triazole moi-
eties would have enhanced biological properties. The investi-
gation further appeared interesting because the insecticidal
data on 2-azetidinones are scanty in the published reports.
In recent years, use of ionic liquids (ILs), which are
organic salts where ions do not pack well and remain liquid
Formation of Schiff’s bases was investigated in various sol-
vents, viz. glc. AcOH, ethanol-glc. AcOH, toluene-glc. AcOH,
and DMF [10,13]. It was observed that DMF was the best sol-
vent for this reaction with no need of catalyst and higher yield
was obtained. Further, the reaction with phenols resulted in nu-
cleophilic substitution of the -Cl group attached to azetidinone
ring to give the 3-phenoxy derivatives [18] (Scheme 1).
© 2013 HeteroCorporation

316
R. Jain, K. Sharma, and D. Kumar
Vol 50
RESULTS AND DISCUSSION
Azetidine derivatives prepared by either method have
same analytical and spectral data. The formation of Schiff’s
bases were characterized by IR spectrum, which show char-
acteristic C═N stretching vibration at 1620 cm–1 with the
disappearance of vibration at 1750 cm–1 (>C═O of isatin
Azetidine derivatives were prepared by two methods.
1. Conventional method
In this two procedures were used:
1
at C-3). In the H NMR spectrum, it shows disappearance
• Method A
of peak due to amino group of 4-amino-4H-1,2,4-triazole
observed from d 4.8 to 5.2 ppm. In 13C NMR, the
peaks appeared at d 148.0 (triazole C-3) and d 149.0
(triazole C-5) ppm besides the indoline carbon atoms.
The formation of Mannich bases from Schiff’s bases were
characterized by the disappearance of peak at 3200 cm–1 due
First, the Schiff’s bases were prepared and isolated
(70–80%) and in the second step, these were
reacted with acetyl chloride/chloroacetylchloride.
The yields were 50–60%.
• Method B
Schiff’s bases prepared by method A were not isolated
and acetyl chloride/chloroacetylchloride was added in
the same flask and refluxed further (65–70%).
1
to >NH of indole of Schiff’s bases in IR spectrum. In H
NMR, the peak at d 10–11 ppm (>NH) disappeared along
with the appearance of peak due to —CH2—N< at d 4.36
ppm (s, 2H, CH2). In 13C NMR characteristic >N—CH2N<,
signal belonging to the Mannich bases was observed at d
171.0 ppm. In the mass spectrum, it shows M+ at m/z 213 (3a).
Formation of azetidine derivatives by CH3COCl was
characterized by IR absorption band at 1690 cm–1 (COCH2
2. Ionic liquid mediated method
In this one pot synthesis indole-2,3-diones, 4-amino-4H-
1,2,4-triazole, and acetyl chloride/chloroacetylchloride
were heated in ionic liquid [bmim]PF6 for 2 h, with or
without the catalyst, Et3N. Yield is much better (90–95%) in
the presence of catalyst, which was (80–85%) without it.
1
of monocyclic b-lactam ring). In H NMR, characteristic
Scheme 1
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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Green Synthesis of 1-(1,2,4-Triazol-4-yl)spiro[azetidine-2,30-(3H)indole]-20,40(10H)-
317
diones as Potential Insecticidal Agents
peak appeared at d 2.2 ppm (s, 2H, CH2). 13C NMR
exhibited peaks at d 46.0 and 165.6 ppm for CH2CO and
CO of azetidinone ring. Further, in mass spectrum, peak
appeared at M+ at m/z 255 (4a).
Table 1
Insecticidal activity of the synthesized compounds against Periplaneta
americana (KD value in min).
Time (min)
Formation of azetidine derivatives by ClCOCH2Cl was
characterized by IR absorption band at 1705 cm–1 (CO
mononcyclic b-lactam ring) and 750–780 cm–1 (C—Cl
Compound
1% (conc.)
2% (conc.)
3a
3b
3c
3d
3e
3f
3g
3h
3i
4a
4b
4c
4d
4e
5a
5b
5c
5d
5e
5f
10
7
6
9
10
9
7
6
4
6
8
7
6
8
9
8
5
4
8
8
7
4
3
6
7
8
6
6
5
1
group) and H NMR signal at d 4.35 ppm (s, 1H, CH).
13C NMR shows peaks at d 167.2 ppm and d 127.0 ppm
for >C═O and CH—Cl of azetidinone ring. Further, in
the mass spectrum it shows M+ at m/z 289.5 (5a).
Since the —Cl group attached to azetidinone ring is very
reactive and on reacting with phenols, it gave phenoxy
derivative. The formation of phenoxy derivative was con-
firmed by IR spectrum which show peak at 750–780 cm−1
(for C—Cl group) disappeared and bands at 1225–1200 and
1075–1020 cm−1 appears for C—O—C asymmetrical and
9
10
10
11
7
6
11
9
9
6
5
8
9
10
8
9
7
1
symmetrical stretching, respectively. In the H NMR, the
CH-Cl signal (d 4.35 ppm) shifted downfield for —OCH—
O—R (d 4.81 ppm). 13C NMR shows peak at d 158.9 ppm
for >CH—OR. Mass spectrum shows M+ at (m/z) 392 (6a).
INSECTICIDAL ACTIVITY
6a
6b
Std
For insecticidal activity [19, 20], Periplaneta americana
was taken and where 1 and 2% solutions of prepared com-
pounds were injected in the abdominal region of the cockroach
with the help of microsyringe. At the time of death, the anten-
nae become motionless, the appendages shrunk, and folded
toward central side and the cockroach lay dorsally, which
was noted as KD (knock down) value. The KD value of syn-
thesized heterocyclic derivatives was compared with control
drug (cypermethrin). Results have been recorded in Table 1.
It was observed that compounds having fluoro and
chloro group exhibited better insecticidal activity (KD
value is 3–5 min) in comparison to standard drug (KD
value is 5–7 min). Rest of the compounds have significant
to moderate activity (KD value is 6–11 min).
Std – cypermethrin.
1
(cm–1). The H NMR spectra and 13C NMR spectra have been
recorded on JEOL 300 MHz in DMSO-d6/CDCl3. Chemical
shifts (d) are given in ppm. The mass spectra were recorded on
JEOL SX 102 (FAB). Elemental analyses were performed at
Central Drug Research Institute, Lucknow, India. Commercially
available (ACROS) ionic liquid [bmim]PF6 was used for the
reactions.
Indole-2,3-diones 1. These were prepared by following the
published report method [21,22].
Conventional method for the synthesis of 3a-3i, 4a–4e, and
5a–5f
CONCLUSION
• Method A
In conclusion, the presented method (ILs) provided an
environmental friendly, efficient, and convenient proce-
dure to synthesize azetidinones in the presence of Et3N
and [bmim]PF6 avoiding the use of a large amount of
organic solvents. Further, nucleophilic substitution reac-
tion of –Cl group of azetidinone ring was carried out using
various phenols. Some of the synthesized compounds may
be developed as good insecticidal agents.
1. 3-[4H-1,2,4-Triazol-4-yl]-imino-indol-2-one (3a)
Equimolar quantities (0.01 mol) of indole-2,3-dione and 4-
amino-4H-1,2,4-triazole were dissolved in DMF (5 mL) [13,23].
The reaction mixture was refluxed for 6 h and then kept at room
temperature overnight. The resultant solid was washed with etha-
nol, dried, and recrystallized from ethanol–water mixture to give
the Schiff’s bases, orange in color yield 80%; m.p. 230ꢀC; IR
(KBr cm–1) vmax: 3320 (>NH), 1650 (CONH), 1620 (C═N);
1H NMR (300 MHz, CDCl3 + DMSO-d6), d ppm: 6.95–7.48
(m, 4H, Ar-H), 8.25 (s, 2H, -CH of triazole), 9.02 (br, 1H,
>NH); 13C NMR (75 MHz, CDCl3 + DMSO-d6), d ppm:
121.6–137.8 (aromatic carbons), 148.0 (C-3 triazole), 149.0 (C-
5 triazole), 164.2 (>C═N), 168.2 (>C═O); MS (m/z): 213
(M+), Anal. Calcd. for C10H7N5O; C, 56.34; H, 3.29; N, 32.86,
Found C, 56.38; H, 3.34; N, 32.82%.
EXPERIMENTAL
Melting points are uncorrected and were taken in open glass
capillaries using Gallenkamp melting point apparatus. The IR
spectra were recorded on a 800S SHIMADZU IR spectrometer
in KBr pellets and band positions are reported in wave numbers
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

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R. Jain, K. Sharma, and D. Kumar
Vol 50
Table 2
Physical and analytical data of the compounds synthesized.
Yield (%)
Analysis % Calcd. (Found)
H N
Compd.
No.
Mol.
34formula
M.P.
(ꢀC)
X
R
R1
Conv.
IL
C
3a
3b
3c
3d
3e
3f
H
5-Cl
5-F
H
H
H
H
H
H
–
–
–
–
–
–
–
–
80
75
73
76
72
77
70
74
–
–
–
–
–
–
–
–
C
10H7N5O
230
192
187
195
146
178
211
237
56.34 (56.38) 3.29 (3.34)
48.48 (48.45) 2.42 (2.47)
51.94 (51.90) 2.59 (2.62)
58.14 (58.11) 3.96 (4.01)
67.32 (67.36) 4.29 (4.31)
57.78 (57.81) 5.18 (5.14)
60.40 (60.44) 6.04 (6.09)
61.94 (61.91) 5.81 (5.85)
32.86 (32.82)
28.28 (28.29)
30.30 (30.33)
30.83 (30.87)
23.10 (23.14)
31.11 (31.15)
28.19 (28.24)
27.09 (27.11)
C10H6N6OCl
C10H6N5OF
C11H9N5O
C17H13N5O
C13H14N6O
C15H18N6O
C16H18N6O
CH3
CH2Ph
CH2NMe2
CH2NEt2
3g
3h
H
H
H2CN
3i
H
H
5-Cl
5-F
H
H
H
5-Cl
5-F
H
COCH3
H
H
H
CH3
CH2NMe2
–
–
–
–
–
–
–
–
–
–
–
–
79
70
65
62
66
64
69
70
65
62
64
61
–
–
C12H9N6O2
C12H9N5O2
205
154
208
182
158
164
138
282
112
108
90
56.47 (56.46) 3.53 (3.57)
56.47 (56.44) 3.53 (3.49)
49.74 (49.72) 2.76 (2.74)
49.74 (49.70) 2.93 (2.90)
52.75 (52.74) 4.09 (4.11)
57.69 (57.71) 5.12 (5.09)
49.74 (49.70) 2.76 (2.80)
44.44 (44.48) 2.16 (2.14)
46.83 (46.80) 2.27 (2.30)
51.40 (51.44) 3.29 (3.24)
60.08 (60.12) 3.69 (3.66)
51.95 (51.99) 4.33 (4.29)
55.10 (55.14) 3.06 (3.05)
66.49 (66.44) 3.78 (3.80)
27.45 (27.41)
27.45 (27.43)
24.18 (24.20)
25.64 (25.68)
26.02 (26.06)
26.92 (26.88)
24.15 (24.18)
21.60 (21.55)
22.76 (22.81)
23.06 (23.03)
18.44 (18.46)
24.24 (24.21)
21.42 (21.47)
17.63 (17.62)
4a
4b
4c
4d
4e
5a
5b
5c
5d
5e
5f
95
94
90
94
92
90
92
93
94
90
92
92
90
C12H8N5O2Cl
C12H8N5O2F
C13H11N5O2
C15H16N6O2
C12H8N5O2Cl
C12H7N5O2Cl2
C12H7N5O2ClF
C13H10N5O2Cl
C19H14N5O2Cl
C15H15N6O2Cl
C18H12N6O5
C22H15N5O3
H
H
H
CH3
CH2Ph
CH2NMe2
H
H
H
H
H
118
181
190
6a
6b
4-O2NC6H4-
2–Naphthyl-
H
–
122.1–138.2 (aromatic carbons), 127.0 (CH-Cl), 148.0 (C-3 triazole),
149.0 (C-5, triazole), 165.4 (ClCH-CO), 169.3 (NHCO); MS (m/z):
289.5 (M+), Anal. Calcd. for C12H8N5O2Cl: C, 49.74; H, 2.76; N,
24.15. Found: C, 49.70; H, 2.80; N, 24.18%.
Compounds 3b–3i have been prepared similarly, their physical
and analytical data are recorded in Table 2.
2. 1-(1,2,4-Triazole-4-yl)spiro[azetidine-2,30(3H)indole]-
20,40-(10H)-diones (4a)
Compounds 5b–5f have been prepared, similarly, their physi-
To a solution of Schiff’s base (0.01 mol) in DMF (10 mL), acetyl
chloride [24] (0.01 mol) and triethylamine (0.01 mol) were added
and the reaction mixture was stirred at room temperature for 24 h.
The reaction mixture was poured into ice cold water and liberated
compounds were extracted with chloroform. Solvent was evapo-
rated under reduced pressure and recrystallized with ethyl acetate
to give 4a in 60% yield, m.p. 154ꢀC; IR(KBr cm–1) vmax: 3380
(>NH), 1660 (C═O, azetidine), 1630 (CONH); 1H NMR
(300 MHz, CDCl3 + DMSO-d6), d ppm: 3.21(s, 2H, CH2CO),
6.50–7.55 (m, 4H, Ar-H), 8.01 (s, 2H, ═CH), 9.23 (br, 1H, >NH);
13C NMR (75 MHz, CDCl3 + DMSO-d6), d ppm: 86.5 (spiro C-3),
46.8 (CH2CO), 121.8–138.5 (aromatic carbons), 148.0 (C-3,
triazole), 149.0 (C-5, triazole), 165.6 (CH2CO)), 168.0 (NHCO);
MS (m/z): 255 (M+), Anal. Calcd. for C12H9N5O2: C, 56.47; H,
3.53; N, 27.45. Found: C, 56.44; H, 3.49; N, 27.43%.
cal and analytical data are recorded in Table 2.
• Method B
A mixture of indole-2,3-dione (0.01 mol) and 4-amino-4H-
1,2,4-triazole (0.01 mol) was refluxed in DMF (10 mL) for 2 h
with few molecular sieves 4A0 size to absorb a theoretical amount
of the water formed. On cooling of the mixture, acetyl chloride/
chloroacetylchloride (0.01 mol) and Et3N (0.01 mol) were added
and the resultant mixture refluxed further for 2 h. The reaction
mixture was cooled, poured into ice cold water, and liberated
compound was extracted with chloroform. Solvent was evapo-
rated under reduced pressure and recrystallized by ethyl acetate
or purified by column chromatography over silica gel using
ethylacetate/benzene = 3:7 as an eluent yield 65–70%. Com-
pounds 4b–4e and 5b–5f have been prepared, similarly, their
physical and analytical data are the same as in method A.
Compounds 4b–4e have been prepared, similarly, their physi-
cal and analytical data are recorded in Table 2.
3. 3-Chloro-1-(1,2,4-triazole-4-yl)spiro[azetidine-2,30(3H)
indole]- 20,40-(10H)-diones (5a)
IONIC LIQUID MEDIATED ONE POT
It was prepared similarly as 4a taking 3a and chloroacetylchloride
yield 60%, m.p. 138ꢀC. IR (KBr cm–1) vmax: 3290 (>NH), 1705
(C═O, azetidine), 1690 (CONH), 780 (C-Cl); 1H NMR (300 MHz,
CDCl3 + DMSO-d6), d ppm: 4.35 (s, 1H, CH-Cl), 6.95–7.81 (m,
4H, ArH), 8.21 (s, 2H, ═CH, triazole), 9.02 (s, 1H, >NH); 13C
NMR (75 MHz, CDCl3 + DMSO-d6), d ppm: 86.8 (spiro C-3),
SYNTHESIS OF 4a–4e AND 5a–5f
A mixture of indole-2,3-dione (0.01 mol), 4-amino-4H-
1,2,4-triazole (0.01 mol), and ionic liquid [bmim]PF6
(5 mL) were taken in a round-bottomed flask and heated
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Green Synthesis of 1-(1,2,4-Triazol-4-yl)spiro[azetidine-2,30-(3H)indole]-20,40(10H)-
319
diones as Potential Insecticidal Agents
at 60–70ꢀC under N2 protection [16] for 1 h. On cooling at
room temperature (after 15 min) acetyl chloride/
chloroacetylchloride (0.01 mol) and triethylamine (0.01
mol) were injected and stirred for 15 min at room temper-
ature thereafter, the temperature was raised to 60ꢀC and the
mixture was stirred further for 2 h. The progress of the re-
action was monitored by TLC. After completion of reac-
tion, the mixture was extracted with ether (6 ꢁ 10 mL).
The organic extract was washed with 5% Na2CO3 (40
mL) and water (40 mL), dried with anhydrous magnesium
sulfate and evaporated in vacuo. The residual product was
purified by recrystallization from AcOEt/cyclohexane or
by column chromatography (silica gel, 200–300 mes, elu-
ent, cyclohexane/AcOEt = 4:1) to give 4a–4e, 5a–5f in
90–95% yield. The ionic liquid layer was washed with wa-
ter (3 ꢁ 5 mL) and kept for 2 h at 80–85ꢀC under reduced
pressure. The ionic liquid was reused for further synthesis
of other compounds.
(m/z): 392 (M+). Anal. Calcd. for C18H12N6O5: C,
55.10; H, 3.06; N, 21.42. Found: C, 55.14; H, 3.05; N,
21.47%. Compound 6b was prepared, similarly, its data
are recorded in Table 2.
Acknowledgments. Authors are grateful to UGC, New Delhi,
India for granting Research Award to Kanti Sharma and to
CSIR, New Delhi, India for granting JRF to Deepak Kumar.
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Recovery of the ionic liquid. An attempt was made to
recover the ionic liquid. After completion of the reaction,
the reaction mixture was poured into ice water, and the
product was filtered-off. The filtrate was extracted with
ethyl acetate to recover unreacted reactants, and the
aqueous layer was subjected to evaporation of water to
get viscous liquid, which on cooling, gave the ionic
liquid. The recovered ionic liquid was reused for two
more cycles of the same cyclocondensation and found to
act satisfactorily.
3-p-Nitrophenoxy-1-(1,2,4-triazol-4-yl)spiro[azetidine-2,30
[3H]indole-20,40(10H)]-dione (6a). An equimolar (0.002
mol) mixture of 5a and p-nitrophenol in ionic liquid
[bmim]PF6 (5 mL) containing Et3N (0.003 mol) was
refluxed for 2 h. The progress of reaction was checked
by TLC. After completion of reaction it was worked up
as described for 5a, yield 92% m.p. 181ꢀC; IR (KBr
cm–1) vmax: 3310 (>NH), 1700 (C═O, azetidine), 1680
(CONH), 1355 (NO2 of phenyl), 1255 (C-O-C,
asymmetrical stretching), 1075 (C-O-C, symmetrical
[20] Shay, P. N.; Lionel, E. W. C.; Fung, Y. P.; Yan, H.;
Manjunath, R. K.; Shuit, H. H. Pestic Sci 1998, 54, 261.
[21] Schmidt, M. S.; Reverdito, A. M.; Kremanchuzky, L.; Perillo,
I. A.; Blanco, M. M. Molecules 2008, 13, 831.
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2001, 12, 273.
[23] Jeyachandran, M.; Ramesh, P. Indian J Heterocycl Chem
2009, 19, 195.
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37, 1094.
1
stretching); H NMR (300 MHz, CDCl3 + DMSO-d6), d
ppm: 4.81 (s, 1H, -O-CH-OR), 6.85–7.83 (m, 8H, ArH),
8.32 (s, 2H, ═CH, triazole); 9.30 (s, 1H, >NH); 13C
NMR (75 MHz, CDCl3 + DMSO-d6), d ppm: 90.2
(spiro C-3), 122.2–138.9 (aromatic carbons), 148.0 (C-3
of triazole), 149.0 (C-5, triazole), 158.9 (-O-CH-
OC6H4NO2), 165.6 (-O-CH-CO), 169.8 (>NHCO); MS
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet