Highly monodispersed PEG-stabilized Ni nanoparticles: Proficient catalyst for the synthesis of biologically important spiropyrans

Article abstract of DOI:10.1071/CH11444

A convenient and efficient synthesis of biologically and pharmacologically important spiropyrans from the condensation of malononitrile, 1,3-dicarbonyl compounds and ninhydrin/acenaphthequinone/isatin has been reported using recyclable heterogeneous polyethylene glycol (PEG)-stabilized Ni nanoparticles in ethylene glycol. This new protocol affords products in high yields and less reaction time.

Full text of DOI:10.1071/CH11444

CSIRO PUBLISHING
Aust. J. Chem. 2012, 65, 314–319
Full Paper
http://dx.doi.org/10.1071/CH11444
Highly Monodispersed PEG-stabilized Ni Nanoparticles:
Proficient Catalyst for the Synthesis of Biologically
Important Spiropyrans
A B
,
A
Jitender M. Khurana
and Sneha Yadav
A
Department of Chemistry, University of Delhi, Delhi 110007, India.
Corresponding author. Email: jmkhurana1@yahoo.co.in
B
A convenient and efficient synthesis of biologically and pharmacologically important spiropyrans from the condensation
of malononitrile, 1,3-dicarbonyl compounds and ninhydrin/acenaphthequinone/isatin has been reported using recyclable
heterogeneous polyethylene glycol (PEG)-stabilized Ni nanoparticles in ethylene glycol. This new protocol affords
products in high yields and less reaction time.
Manuscript received: 22 November 2011.
Manuscript accepted: 17 January 2012.
Published online: 24 February 2012.
of aldehydes with barbituric acids,[26] o-phenylenediamine and
2-aminobenzothiazole[27] in ethylene glycol. We have also
reported the Knoevenagel condensation followed by cascade
enol lactonization using arylidene Meldrum’s acid and active
methylenes catalyzed by PEG-stabilized Ni nanoparticles in
ethylene glycol.[28] In continuation of our efforts to explore the
catalytic applications of Ni nanoparticles in organic synthesis,
we wish to report a novel and highly efficient protocol for the
synthesis of spiro-fused pyran derivatives using Ni nanoparti-
cles as catalyst.
Introduction
Spiro compounds represent an important class of naturally
occurring substances known for their biological properties.[1,2]
Among them, spiropyrans have attracted strong interest owing
to their potential activity as hypertensive and analgesic agents[3]
and applications to industrial fields.[4] Oxindole derivatives are
known to possess biological activities, such as potent inhibition
of monoamine oxidase in human urine and rat tissues,[5] inhi-
bition of several enzymes such as acetylcholinesterase[6] and
atrial natriuretic peptide-stimulated guanylate cyclase, and
potent antagonist of in vitro receptor binding by atrial natriuretic
peptide,[7] besides possessing a wide range of central nervous
system activities.[8] The spirooxindole system is the core
structure of many pharmacological agents and natural alka-
loids.[9–11] On the other hand, ninhydrin is a unique tricarbonyl
compound that is widely used in biochemical and medical set-
tings for the analysis of amino acids.[12]
In recent years, a variety of synthetic methodologies for
constructing spiro-fused pyran derivatives via multi-component
condensation reactions have been reported.[13–17] Each of the
known procedures for the synthesis of spiropyrans has its merits
and demerits but the development of facile, greener and eco-
nomical synthetic routes is still essential. Owing to the high
surface area to volume ratio, metal nanoparticles have proved to
be very efficient catalysts in comparison to the traditional
catalysts. Ni nanoparticles, in particular, have gained much
attention over the decade owing to their ease of preparation,
high reaction yields and recyclability. Ni nanoparticles over-
come the shortcoming of recyclability of homogeneous nickel
catalysts thereby behaving as efficient heterogeneous catalysts.
Pioneering work using Ni nanoparticles includes selective
hydrogenation,[18] C-C coupling namely Suzuki coupling,[19]
Heck reaction,[20] Nigeshi coupling,[21] Kumada coupling,[22]
Mizoroki-Heck coupling,[23] and other Ni nanoparticle-
catalyzed reactions.[24,25] Recently, we have reported PVP-
stabilized Ni0 nanoparticle-catalyzedKnoevenagel condensation
Results and Discussion
We report, herein, the synthesis of a variety of spiro-2-amino-
4H-pyrans, spiroacenaphthylenes and spirooxindoles by the
one-pot condensation of ninhydrin/acenaphthequinone/isatin
with malononitrile and a variety of a-methylene carbonyl
compounds in the presence of Ni nanoparticles in ethylene
glycol at room temperature.
Catalyst Characterization
The average size of Ni nanoparticles was found to be 7 nm
through transmission electron microscopy (TEM) (Fig. 1a) and
XRD analysis (Fig. 1b). Energy dispersive X-ray (EDAX) data
(Fig. 1c) and the XRD pattern confirmed the metallic nature of
Ni nanoparticles. As per the X-ray diffraction plot, the peaks at
2y ¼ 44.58, 51.88 and 76.48, corresponding to the (111), (200)
and (222) lattice planes respectively, clearly indicate the pres-
ence of pure elemental Ni with face-centred cubic (FCC)
structure. The size from the XRD data was calculated to be
6.9 nm and is consistent with TEM results.
Ni Nanoparticle-catalyzed Synthesis of Spiropyrans
Ni nanoparticle dispersion in ethylene glycol was used as
such for the reactions. We investigated the condensation
of ninhydrin (1a, 1 equiv.), malononitrile (1.1 equiv.) and
Journal compilation Ó CSIRO 2012
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Ni Nanoparticle-catalyzed Synthesis of Spiropyrans
315
(a)
resulted in the formation of corresponding spiroacenaphthylene
(5a) and spirooxindole (6a) in high yields under the same
reaction conditions. Ethylene glycol served as a suitable solvent
for these transformations. Based on the solubility difference of
the products and starting materials, the products separated
readily from the reaction mixture upon completion, thereby
facilitating their easy isolation simply by filtration. Subse-
quently, the reactions of ninhydrin, acenaphthequinone and
isatin with malononitrile and various 1,3-dicarbonyl compounds
gave the corresponding spiro-2-amino-4H-pyrans, spir-
oacenaphthylenes and spirooxindoles (Chart 1) in high yields.
All results have been summarized in Table 1.
10 nm
(b)
Catalyst Role Justification
The role of Ni nanoparticles was elucidated by a control
experiment which was conducted with ninhydrin (1 equiv.),
malononitrile (1.1 equiv.) and dimedone (1 equiv.) in ethylene
glycol in the absence of Ni nanoparticles. This resulted in the
formation of 4a after 7 h with only 55 % yield. Also low yields
were obtained when the reaction was carried out with Ni2þ salt
alone in ethylene glycol at room temperature, whereas when the
reaction was carried out in the presence of a catalytic amount of
NaBH4, a mixture of products was obtained. The nanoparticles
were isolated from the ethylene glycol dispersion, washed with
absolute ethanol several times and redispersed in ethylene gly-
col. This dispersion was then used for carrying out the reaction
between 1a, 2 and 3a. The reaction resulted in formation of 4a in
90 % yield in 8–10 min. The reaction was also attempted with Ni
powder (size ,150 micron) in ethylene glycol. The reaction
was only 62 % complete even after 8 h of stirring. The results
have been recapitulated in Table 2.
200
(111)
150
100
(200)
50
(222)
0
30
40
50
60
70
80
2θ
(c)
Recyclability of Catalyst
Label A: Chlorite (Nrm. % ϭ 38.86, 20.96, 34.83, 1.14, 3.84, 0.28)
The catalyst could be recycled simply by solvent extraction of
the product several times from the reaction mixture using ethyl
acetate, becuase it was completely immiscible with ethylene
glycol at room temperature. Upon sonication, the ethylene
glycol layer containing the Ni nanoparticles could be reused for
the subsequent cycles. The relationship between the number of
cycles of the reaction and the catalytic activity in terms of yields
is presented in Fig. 2a. It was found that the catalyst retained
optimum activity until four cycles after which a drop in yield
was observed. The plausible reason for this could be the
decreased stability of the nanoparticles with subsequent recy-
cling which resulted in diminished catalytic activity owing to
agglomeration of nanoparticles, as shown in Fig. 2b.
Ni
Ni
Ni
C
Cu
Ni
O
N
Mechanism
Cu
8.00
A rational mechanism for the formation of the spiropyrans via
tandem Knoevenagel-cyclo-condensation is outlined in
Scheme 1. The reaction occurs via initial formation of Knoe-
venagel condensate (I) from ninhydrin (1a) and malononitrile
(2), which reacts with dimedone (3a) and subsequently cyclizes
to afford the desired product 4a after proton transfer and
tautomerization.
4.00
12.00
16.00
20.00
24.00
Fig. 1. (a) TEM image of PEG-stabilized Ni nanoparticles. (b) X-ray
diffraction pattern of PEG-Ni nanoparticles. (c) EDAX data of PEG-Ni
nanoparticles.
dimedone (1 equiv.) in the presence of Ni nanoparticles dis-
persed in ethylene glycol by varying reaction conditions. It was
observed that 4a was formed in 7 min in 93 % yield using a
catalytic amount of Ni nanoparticles in ethylene glycol [2 mL of
dispersion (0.0235 wt % Ni)/0.1 g ninhydrin] at room tempera-
ture. Condensations of malononitrile and dimedone with ace-
naphthequinone (1b) or isatin (1c) in place of ninhydrin (1a) also
Conclusions
In conclusion, we have successfully developed a novel and
efficient method for the synthesis of diverse spiropyrans through
a three-component one-pot reaction catalyzed by PEG-
stabilized Ni nanoparticles. The protocol offers advantages such

316
J. M. Khurana and S. Yadav
O
NC NH2
O
O
CN
CN
Ni nps
O
ϩ
ϩ
Ethylene glycol
rt
O
O
O
O
3
1a
2
4a–l
O
H2N
NC
O
CN
CN
Ni nps
O
ϩ
ϩ
Ethylene glycol
O
rt
1b
3
2
5a–h
H2N
O
O
CN
CN
Ni nps
NC
ϩ
ϩ
O
Ethylene glycol
rt
N
O
H
O
N
H
1c
2
3
6a–f
O
O
O
S
O
OH
OH
Et
Et
O
N
N
N
N
ϭ
O
O
O
O
O
O
O
O
O
O
O
3
3b
3a
3c
3d
3e
3f
3g
O
O
O
O
O
O
HN
NH
OH
N
O
N
O
H
O
O
O
O
O
3j
3h
3i
3k
3m
3l
Chart 1. PEG-stabilized Ni nanoparticle-catalyzed synthesis of spiropyrans.
Table 1. PEG-Ni nanoparticle-catalyzed synthesis of spiropyrans 4, 5, and 6
Sr. No.
1
1,3-dicarbonyl
Product
Time [min]
Yield [%]
mp [8C][13–17]
1.
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1a
1b
1b
1b
1b
1b
1b
1b
1b
1c
1c
1c
1c
1c
1c
3a
3b
3c
3d
3e
3f
4a
4b
4c
4d
4e
4f
7
5
93
90
89
91
92
92
90
89
91
90
89
88
93
89
93
92
90
90
94
94
92
92
90
89
91
88
290–292 (.300)[13b]
270–272
280–285 (.300)[13b]
290–295[17]
2.
3.
5
4.
10
10
8
5.
258–260
235–237 (242–244)[13a]
6.
7.
3g
3h
3i
4g
4h
4i
15
12
10
12
15
20
10
10
8
230–235
8.
255–260*
9.
290–295 (250–252)[13a]
280–282 (282–282)[13a]
275–277 (.300)[13b]
220–225
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
3j
4j
3k
3l
4k
4l
3a
3b
3d
3e
3f
5a
5b
5c
5d
5e
5f
270 (268–270)[16]
275–280
290–295
280–282 (.300)[13b]
180–185
5
12
8
3g
3h
3i
260–265
5g
5h
6a
6b
6c
6d
6e
6f
8
270–272 (.300)[16]
250–255 (298)[16]
295–300 (290–292)[14]
275–280*
6
3a
3b
3d
3e
3f
5
10
10
20
8
280–282 (278–280)[14a]
220–225 (230)[14b]
205–210 (221)[14b]
260–265 (295)[17b]
3m
20
*Compound known but mp reported for first time.

Ni Nanoparticle-catalyzed Synthesis of Spiropyrans
317
Table 2. Reactions validating the involvement of Ni nanoparticles
for the synthesis of 4a
were recorded on a JEOL JNM ECX-400P (400 MHz) spec-
trometer with DMSO-d6 as the solvent and TMS as the internal
standard. IR spectra were recorded on a Perkin-Elmer FT-IR
SPECTRUM-2000. Mass spectra were recorded on JEOL-
AccuTOF JMS–T100 mass spectrometer having a DART
source. Melting points were recorded on a Tropical Labequip
apparatus and are uncorrected.
Sr. No.
Reaction conditions
Time
Yield [4a, %]
1.
2.
3.
4.
Ethylene glycol (EG) alone
NiCl2ꢂ6H2O alone in EG
NaBH4 alone in EG
7 hA
55
58
–
7 hA
6 hB
Isolated Ni nanoparticles
redispersed in EG
10 min
90
Preparation of Ni Nanoparticles
5.
Ni powder (size ,150 micron)
8 hA
62
Ni nanoparticles were prepared by a modified polyol method as
reported in literature.[28] To a 2 ꢀ 10ꢁ4 M solution of
NiCl2ꢂ6H2O (0.0048 g) in ethylene glycol (100 mL) placed in a
250 mL round bottom flask fitted with a reflux condenser, PEG
4000 (0.024 g, Ni2þ:PEG: 1:5 wt %) was added. The mixture
was stirred until complete dissolution of PEG. The solution was
heated in an oil bath maintained at 1208C. At this temperature,
0.36 g NaBH4 was added to the solution. The system was
maintained under magnetic stirring at 1208C for 2 h. The sample
for TEM analysis was obtained by the addition of acetone to the
Ni nanoparticles dispersion in ethylene glycol, followed by
centrifugation (6000 rpm). The particles, so obtained, were
washed free of any residual components using ethanol. Subse-
quently, a drop of methanol dispersion of Ni nanoparticles was
placed on a carbon coated Cu grid (mesh size 300). A sample for
the X-ray diffraction study was obtained by depositing a thin
coating of the isolated Ni nanoparticles (dispersed in absolute
ethanol) onto a glass plate followed by vacuum drying.
AIncomplete reaction.
BMixture of products; no 4a observed.
(a)
Recyclability of Ni nanoparticles
100
80
60
40
20
0
General Procedure for the Synthesis of Spiropyrans
1
2
3
4
5
Ninhydrin/acenaphthequinone/isatin (1 equiv.), malononitrile
(1.1 equiv.), 1,3-dicarbonyl compound (1 equiv.) and a well
stirred dispersion of Ni nanoparticles in ethylene glycol [2 mL of
dispersion (0.0235 wt % Ni)/0.1 g 1a/1b/1c] was added to a
50 mL round bottom flask. The mixture was stirred at room
temperature. The reaction progress was monitored by thin col-
umn chromatography (TLC), using petroleum ether/ethyl
acetate (6:4) as eluent. All the reactions were complete in
10–15 min. Upon completion, 15 mL water was added to the
reaction mixture and the solid product was filtered at the pump,
washed with water, dried and recrystallized from hot ethanol.
The products were identified by spectral data.
Number of cycles
(b)
2-Amino-7-methyl-10,30,5-trioxo-10,30,5,6,7,8-
hexahydrospiro[chromene-4,20-indene]-3-
carbonitrile 4b
20 nm
Mp 2708C (dec.). nmax (KBr)/cmꢁ1 3365, 3299, 3181, 2969,
2195, 1713, 1676, 1642, 1420, 1365, 1216, 1051. dH (400 MHz,
DMSO-d6) 8.03–7.99 (m, 4H, Ar-H), 7.65 (s, 2H, NH2), 2.71–
2.66 (m, 1H), 2.56–2.54 (m, 1H), 2.31–2.22 (m, 2H), 2.13–2.07
(m, 1H), 1.01 (s, 3H). dC (100 MHz, DMSO-d6) 19.88, 27.55,
33.85, 43.10, 51.83, 53.08, 110.61, 116.85, 123.10, 123.16,
136.62, 140.47, 140.59, 159.83, 167.49, 196.04, 199.70,
199.78. m/z (ESI) 335.1 [MþH]þ.
Fig. 2. (a) Recyclability of Ni nanoparticles: plot of yield (%) of 4a versus
number of cycles. (b) TEM image of Ni nanoparticles obtained after five
cycles.
as high yields, mild reaction conditions and an environmentally
benign procedure. Moreover, the nanocatalysts are stable to
leaching and can be reused without significantly affecting the
yields.
70-Amino-10,30-dimethyl-1,20,3,40-tetraoxo-
1,10,20,3,30,40-hexahydrospiro[indene-2,50-pyrano[2,3-
d]pyrimidine]-60-carbonitrile 4e
Experimental
Mp 2608C (dec.). nmax (KBr)/cmꢁ1 3381, 3292, 3195, 2194,
1749, 1694, 1386, 1193. dH (400 MHz, DMSO-d6) 8.05–8.04
(m, 4H, Ar-H), 7.97 (s, 2H, NH2), 3.37 (s, 3H), 3.00 (s, 3H).
dC (100 MHz, DMSO-d6) 199.74, 160.47, 159.47, 153.08,
149.55, 140.45, 137.01, 123.32, 116.38, 85.64, 53.25, 52.08,
29.82, 28.78. m/z (ESI) 365.1 [MþH]þ.
All the chemicals used were of research grade and were used
without further purification. Transmission electron microscopy
for size and morphology characterization was obtained on
TECNAI G2 U-TWIN (300 kV) and JEOL 2100-F (200 kV)
instruments. X-ray diffraction pattern was obtained on a
1
BRUKER D8 diffractometer. H NMR and 13C NMR spectra

318
J. M. Khurana and S. Yadav
PEG
Ni
O
O
O
PEG
O
O
Ni
CN
CN
N
ϩ
(I)
CN
H
1a
2
O
O
O
O
PEG-Ni nps
3a
N
HN
N
NC
N
O
HO
NC
O
NC
O
O
O
HO
NC
O
OH
O
PEG-Ni nps
O
O
O
O
O
O
PEG-Ni nps
H2N
O
NC
O
O
O
4a
Scheme 1. Plausible mechanistic pathway for the PEG-Ni nanoparticle-catalyzed synthesis of spiropyrans.
2-Amino-10,30,5-trioxo-10,30,6,7-tetrahydro-5H-spiro
[cyclopenta[b]pyran-4,20-indene]-3-carbonitrile 4g
20-Amino-70-methyl-2,50-dioxo-2H,50H-spiro
[acenaphthylene-1,40-pyrano[4,3-b]pyran]-30-
carbonitrile 5c
Mp 230–2358C. nmax (KBr)/cmꢁ1 3500, 3363, 2924, 2196,
1745, 1714, 1673, 1592, 1342, 1263. dH (400 MHz, DMSO-d6)
8.11–8.04 (m, 4H, Ar-H), 7.90 (s, 2H, NH2), 2.90–2.89 (m, 2H,
CH2), 2.42–2.39 (m, 2H, CH2). dC (100 MHz, DMSO-d6)
200.50, 198.84, 198.47, 179.64, 161.64, 140.85, 140.23,
137.53, 136.62, 123.58, 123.43, 117.13, 113.45, 111.40,
76.00, 52.52, 51.79, 32.92, 30.36, 25.53. m/z (ESI) 307.2
[MþH]þ.
Mp 2908C (dec.). nmax (KBr)/cmꢁ1 3473, 3340, 2725, 2186,
1738, 1699, 1633, 1463, 1418, 1360, 1231. dH (400 MHz,
DMSO-d6) 8.32–8.30 (m, 1H, Ar-H), 7.99–7.97 (m, 3H,
Ar-H), 7.86–7.82 (m, 1H, Ar-H), 7.69–7.66 (m, 1H, Ar-H),
7.52 (s, 2H, NH2), 6.41 (s, 1H), 2.22 (s, 3H, CH3). dC (100 MHz,
DMSO-d6) 203.43, 163.92, 160.60, 159.90, 158.60, 141.91,
141.05, 132.09, 131.34, 129.76, 128.97, 128.62, 125.02,
121.91, 120.72, 117.22, 99.21, 98.04, 57.92, 50.90, 19.28. m/z
(ESI) 356 [M]þ.
Ethyl 20-amino-30-cyano-60-methyl-1,3-dioxo-1,3-
dihydrospiro[indene-2,40-pyran]-50-carboxylate 4l
70-Amino-10,30-dimethyl-2,20,40-trioxo-10,20,30,40-
tetrahydro-2H-spiro[acenaphthylene-1,50-pyrano[2,3-d]
pyrimidine]-60-carbonitrile 5d
Mp 2208C (dec.). nmax (KBr)/cmꢁ1 3334, 3176, 2926, 2192,
1659, 1429, 1275, 1166, 1089, 1013; dH (400 MHz, DMSO-d6)
7.95–7.94 (m, 2H, Ar-H), 7.88–7.66 (m, 2H, Ar-H), 7.74 (s, 2H,
NH2), 4.22–4.13 (m, 2H), 2.22 (s, 3H), 1.32 (t, J 7.32, 3H). dC
(100 MHz, DMSO-d6) 193.43, 167.94, 166.71, 163.25, 142.52,
137.12, 135.70, 132.72, 124.97, 124.54, 119.44, 116.99, 105.54,
67.68, 59.83, 53.37, 14.00, 13.84. m/z (ESI) 338 [M]þ.
Mp 280–2828C. nmax (KBr)/cmꢁ1 3404, 3323, 3192, 2960,
2192, 1713, 1679, 1491, 1382, 1189. dH (400 MHz, DMSO-d6)
8.42–8.19 (m, 1H, Ar-H), 7.95 (s, 2H, NH2), 7.83 (s, 1H, Ar-H),
7.65–7.53 (m, 4H, Ar-H), 3.41 (s, 3H, CH3), 2.90 (s, 3H, CH3).
20-Amino-70-methyl-2,50-dioxo-50,60,70,80-tetrahydro-
2H-spiro[acenaphthylene-1,40-chromene]-30-
carbonitrile 5b
70-Amino-10,30-diethyl-2,40-dioxo-20-thioxo-10,20,30,40-
tetrahydro-2H spiro[acenaphthylene-1,50-pyrano[2,3-d]
pyrimidine]-60-carbonitrile 5e
Mp 2708C (dec.). nmax (KBr)/cmꢁ1 3352, 3195, 2194, 1740,
1657, 1459, 1213. dH (400 MHz, DMSO-d6) 8.26–8.23 (m, 1H,
Ar-H), 7.93–7.91 (m, 2H, Ar-H), 7.81–7.80 (m, 1H, Ar-H),
7.64–7.62 (m, 1H, Ar-H), 7.40–7.38 (m, 1H, Ar-H), 7.30 (s, 2H,
NH2), 2.74–2.65 (m, 1H, CH2), 2.57–2.54 (m, 1H, CH2), 2.26–
2.14 (m, 2H, CH2), 2.04–1.98 (m, 1H, CHCH3), 0.99 (s, 3H,
CH3). dC (100 MHz, DMSO-d6) 203.69, 203.54, 195.36, 165.92,
165.31, 158.73, 143.24, 140.44, 131.45, 129.77, 128.90, 128.48,
124.53, 121.44, 121.36, 120.03, 119.90, 117.55, 112.78, 112.60,
58.01, 51.02, 43.94, 34.37, 34.16, 27.43, 20.07, 19.91. m/z (ESI)
357.1 [MþH]þ.
Mp 180–1858C (dec.). nmax (KBr)/cmꢁ1 3303, 3134, 2924,
2726, 2210, 1720, 1684, 1623, 1464, 1377, 1281, 1113.
dH (400 MHz, DMSO-d6) 8.31–8.29 (m, 1H, Ar-H), 7.98–7.96
(m, 3H, Ar-H), 7.86–7.82 (m, 1H, Ar-H), 7.73 (s, 2H, NH2),
7.63–7.61 (m, 1H, Ar-H), 4.67–4.56 (m, 2H, CH2CH3),
4.16–4.05 (m, 2H, CH2CH3), 1.37–1.34 (m, 3H, CH2CH3),
0.94–0.91 (m, 3H, CH2CH3). dC (100 MHz, DMSO-d6)
202.83, 174.33, 157.85, 157.51, 151.98, 141.84, 140.67,
131.98, 131.50, 129.78, 128.93, 128.52, 124.95, 121.77,
121.03, 116.73, 92.84, 57.90, 51.44, 45.00, 42.81, 12.58,
10.99. m/z (ESI) 431.2 [MþH]þ.

Ni Nanoparticle-catalyzed Synthesis of Spiropyrans
319
20-Amino-2,50-dioxo-60,70-dihydro-2H,50H-spiro
[acenaphthylene-1,40-cyclopenta[b]pyran]-30-
carbonitrile 5f
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Mp 2608C (dec.). nmax (KBr)/cmꢁ1 3324, 3296, 2725, 2190,
1749, 1713, 1669, 1586, 1377, 1345, 1236, 1160. dH (400 MHz,
DMSO-d6) 8.34–8.32 (m, 1H, Ar-H), 8.00–7.97 (m, 2H, Ar-H),
7.88–7.84 (m, 1H, Ar-H), 7.71–7.68 (m, 1H, Ar-H), 7.57 (s, 2H,
NH2), 7.48–7.46 (m, 1H, Ar-H), 2.87–2.86 (m, 2H, CH2), 2.34–
2.33 (m, 2H, CH2). dC (100 MHz, DMSO-d6) 202.98, 200.10,
177.79, 160.60, 141,35, 140.71, 132.30, 131.28, 129.81, 129.06,
128.71, 125.05, 122.02, 121.05, 117.66, 115.78, 62.72, 56.98,
50.91, 33.07, 30.62, 25.03. m/z (ESI) 329.1 [MþH]þ.
2-Amino-7-methyl-20,5-dioxo-5,6,7,8-tetrahydrospiro
[chromene-4,30-indoline]-3-carbonitrile 6b
Mp 275–2808C (dec.). nmax (KBr)/cmꢁ1 3307, 3159, 2964,
2194, 1725, 1655, 1602, 1470, 1330, 1216, 1062. dH (400 MHz,
DMSO-d6) 10.29 (s, 1H, NH), 7.11 (s, 2H, NH2), 7.03–7.00 (m,
1H, Ar-H), 6.88–6.85 (m, 1H, Ar-H), 6.78–6.75 (m, 1H, Ar-H),
6.67–6.65 (m, 1H, Ar-H), 2.57–2.52 (m, 1H, CH2), 2.38–2.31
(m, 1H, CH2), 2.17–2.08 (m, 2H, CH2), 1.97–1.87 (m, 1H,
CHCH3), 0.89 (s, 3H, CH3). dC (100 MHz, DMSO-d6) 194.95,
178.15, 178.09, 165.49, 164.91, 158.72, 142.03, 134.55, 134.46,
128.17, 123.23, 123.08, 121.67, 117.39, 111.59, 111.38, 109.18,
62.44, 57.46, 46.87, 44.29, 34.40, 34.16, 27.38, 20.03, 19.99.
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70-Amino-10,30-diethyl-2,40-dioxo-20-thioxo-10,20,30,40-
tetrahydrospiro[indoline-3,50-pyrano[2,3-d]pyrimidine]-
60-carbonitrile 6e
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Mp 2058C. nmax (KBr)/cmꢁ1 3435, 3345, 2921, 2208, 1722,
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(s, 1H, NH), 7.65 (s, 2H, NH2), 7.19–7.21 (m, 2H, Ar-H), 6.81–
6.91 (m, 2H, Ar-H), 4.52–4.63 (m, 2H, CH2CH3), 4.16–4.18 (m,
2H, CH2CH3), 1.31 (s, 3H, CH2CH3), 1.02 (s, 3H, CH2CH3). dC
(100 MHz, DMSO-d6) 177.18, 174.32, 158.00, 157.21, 151.99,
142.13, 133.06, 128.75, 124.08, 121.93, 116.65, 109.41, 92.11,
69.82, 57.25, 47.61, 45.19, 42.63, 12.62, 11.23. m/z (ESI) 396.1
[MþH]þ.
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2-Amino-20,5,10-trioxo-5,10-dihydrospiro[benzo[g]
chromene-4,30-indoline]-3-carbonitrile 6f
Mp 260–2658C. nmax (KBr)/cmꢁ1 3394, 3347, 2926, 2207,
1733, 1668, 1635, 1344, 1200. dH (400 MHz, DMSO-d6) 10.68
(s, 1H, NH), 8.06–8.04 (m, 1H, Ar-H), 7.85–7.80 (m, 3H, Ar-H),
7.56 (s, 2H, NH2), 7.22–7.17 (m, 2H, Ar-H), 6.91–6.86 (m, 2H,
Ar-H). dC (100 MHz, DMSO-d6) 181.86, 177.61, 176.42,
158.66, 150.48, 141.72, 134.88, 134.53, 130.58, 130.33,
128.91, 126.29, 126.04, 124.29, 122.00, 119.46, 117.03,
109.63, 62.82, 56.89, 48.06.
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Supplementary Material
Copies of 1H and 13C NMR spectra of compounds 4b, 4e, 4g, 4l,
5b, 5c, 5e, 5f and 6f are available on the Journal’s website.
Acknowledgements
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doi:10.1002/EJOC.200800729
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S10562-010-0376-2
Sneha is thankful to CSIR, New Delhi, India for the award of Junior and
Senior Research Fellowship.
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J.TETLET.2011.05.032
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