Solvent-free one-pot synthesis of spiro[indoline-3,4′(1h′)- pyrano-[2,3-c]pyrazol]-2-one derivatives by grinding

Article abstract of DOI:10.1080/00397911.2010.519449

The solvent-free one pot synthesis of spiropyranyl-oxindole in the presence of NaHCO₃ under grinding has been achieved. This process is simple, fast, efficient and environmentally benign. Copyright Taylor & Francis Group, LLC.

Full text of DOI:10.1080/00397911.2010.519449

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Solvent-Free One-Pot Synthesis of
Spiro[indoline-3,4′(1H′)-pyrano[2,3-
c]pyrazol]-2-one Derivatives by Grinding
Ying Liu a , Zhongjiao Ren a , Weiguo Cao a b , Jie Chen a , Hongmei
Deng c & Min Shao c
a Department of Chemistry, Shanghai University, Shanghai, P. R.
China
b State Key Laboratory of Organometallic Chemistry, Shanghai
Institute of Organic Chemistry, Chinese Academy of Sciences,
Shanghai, P. R. China
c Instrumental Analysis and Research Center, Shanghai University,
Shanghai, P. R. China
Accepted author version posted online: 08 Jul 2011.Version of
record first published: 22 Aug 2011.
To cite this article: Ying Liu, Zhongjiao Ren, Weiguo Cao, Jie Chen, Hongmei Deng & Min Shao (2011):
Solvent-Free One-Pot Synthesis of Spiro[indoline-3,4′(1H′)-pyrano[2,3-c]pyrazol]-2-one Derivatives by
Grinding, Synthetic Communications: An International Journal for Rapid Communication of Synthetic
Organic Chemistry, 41:24, 3620-3626
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Synthetic Communications1, 41: 3620–3626, 2011
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2010.519449
SOLVENT-FREE ONE-POT SYNTHESIS OF
SPIRO[INDOLINE-3,4’(1H’)-PYRANO-
[2,3-c]PYRAZOL]-2-ONE DERIVATIVES BY GRINDING
Ying Liu,1 Zhongjiao Ren,1 Weiguo Cao,1,2 Jie Chen,1
Hongmei Deng,3 and Min Shao3
1Department of Chemistry, Shanghai University, Shanghai, P. R. China
2State Key Laboratory of Organometallic Chemistry, Shanghai Institute of
Organic Chemistry, Chinese Academy of Sciences, Shanghai, P. R. China
3Instrumental Analysis and Research Center, Shanghai University, Shanghai,
P. R. China
GRAPHICAL ABSTRACT
Abstract The solvent-free one pot synthesis of spiropyranyl-oxindole in the presence of
NaHCO3 under grinding has been achieved. This process is simple, fast, efficient and envir-
onmentally benign.
Keywords Isatin; one pot; solvent-free; spiropyranyl-oxindole
INTRODUCTION
The spiro-oxindole framework represents an important structural motif in a
number of bioactive natural products and pharmaceuticals.[1] Recently, the synthesis
of heterocyclic spiro-oxindole compounds has attracted considerable attention
because the spiro-oxindole compounds containing the heterocyclic system showed
an increased spectrum of biological activities.[2] Pyran derivatives are known sub-
units in many natural products and biologically active compounds, as well as impor-
tant intermediates in organic synthesis.[3] Thus, it is expected that the resulting
compounds would show biological activity if the oxindole is joined to the pyran
Received February 26, 2008.
Address correspondence to Zhongjiao Ren or Weiguo Cao, Department of Chemistry, Shanghai
University, Shanghai 200444, China. E-mail: zjren@shu.edu.cn; wgcao@staff.shu.edu.cn
3620

SPIRO[INDOLINE-3,40(1H0)-PYRANO-[2,3-c]PYRAZOL]-2-ONE DERIVATIVES
3621
system through a spiro carbon atom at C-3. In connection with an ongoing synthesis
program, we are interested in the development of new route for the preparation of
spiropyranyl-oxindole.
With the present growing concern about controlling environmental pollution,
the design of an environmentally friendly chemical processes has attracted consider-
able interest in organic synthesis. The organic solvents are high in the list of harmful
chemicals because they are used in huge amounts and are usually volatile liquids that
are difficult to contain. In recent years, the solvent-free reaction under grinding con-
ditions, developed by Tanaka and Toda,[4] has generated great interests. Numerous
successful reactions widely used in a variety of organic syntheses have been
reported.[5] The advantages of this methodology are high efficiency, mild conditions,
operational simplicity, low cost, and environmental acceptability. The one-pot pro-
cess is one of the most efficient and economical methods for construction of complex
molecules from simple and available starting materials without having to spend time
and resources on the isolation and purification of intermediates.[6]
In continuation of our research devoted to organic reactions under solvent-free
conditions,[5b] here we report a solvent-free, one-pot procedure for the synthesis of
spiropyranyl-oxindoles from isatins, malononitrile, and 2-pyrazolin-5-ones in the
presence of NaHCO3 (Scheme 1).
The base plays a crucial role in this reaction because the formation of
spiropyranyl-oxindole involves Knoevenagel condensation and Michael addition
reaction. First we tested K2CO3 as the base. In the initial experiment, the mixture
of 1a (2 mmol), malononitrile 2 (2.2 mmol), 3a (2.2 mmol), and K2CO3 (6 mmol)
was ground at room temperature. After the starting materials were consumed, the
expected 4a was obtained in 70% yield after 5 min, but some dark by-products were
produced. These by-products reduced the yield and increased the difficulty of separ-
ation and purification. We thought that these side reactions resulted from K2CO3.
When the reaction was carried out with NaHCO3 as the base instead of K2CO3
for 7 min under the same conditions, the yield of 4a was 81%.
To investigate the scope and limitation of this process, various isatins and
2-pyrazolin-5-ones were examined under the same conditions. In all cases, the
reaction proceeded smoothly to afford corresponding spiropyranyloxindoles in good
to excellent yields. The results are shown in Table 1.
The structures of compounds 4a–k were confirmed by 1H NMR, Infrared (IR),
elementary analysis, and x-ray (4e).
A plausible mechanism for this process may probably involve the following key
steps (Scheme 2).
Scheme 1. Preparation of product 4.

3622
Y. LIU ET AL.
Figure 1. X-ray structure of compound 4e.
The arylidenemalononitriles A is formed via Knoevenagel condensation reac-
tion of isatins with malononitrile using NaHCO3 as the base. Compound B is given
through Michael addition in which 1-phenyl-3-methyl-5-pyrazolone 3 (employed as
nucleophile) attacks arylidenemalononitriles A. Then the intramolecular nucleophilic
addition reaction, involving the hydroxyl group and the cyano group in compound
C, takes place, and the imine D is generated. The spiro compounds 4 is obtained
from imine D.
In conclusion, we have developed a solvent-free, one-pot procedure for syn-
thesis of spiro[indoline-3,40(10H)-pyrano[2,3-c]pyrazol]-2-one. Its advantages are
short reaction times, good yields, operational simplicity, and environmental
acceptability.
Table 1. Solvent-free one-pot synthesis of spiropyranyloxindole 4a–k
Reaction
time (min)
Entry
R1
R2
R3
Yield (%)
1
2
H
Cl
Ph
Ph
Ph
H
CH3
CH3
CH3
CH3
CH3
CH3
CH3
Ph
7
7
7
7
7
7
7
7
7
7
7
81 (4a)
70 (4b)
80 (4c)
92 (4d)
86 (4e)
95 (4f)
82 (4g)
87 (4h)
90 (4i)
95 (4j)
89 (4k)
3
NO2
H
4
5
Cl
Br
H
6
H
7
NO2
H
H
8
H
9
Cl
Br
H
Ph
Ph
10
11
H
NO2
H
Ph

SPIRO[INDOLINE-3,40(1H0)-PYRANO-[2,3-c]PYRAZOL]-2-ONE DERIVATIVES
3623
Scheme 2. Mechanism for the formation of product 4.
EXPERIMENTAL
All reagents and solvents were obtained from commercial sources and were
used without purification. All melting points were uncorrected. Melting points were
determined on a WRS-1 digital melting-point apparatus made by Shanghai Physical
Instrument Factory (SPOIF), China. Infrared (IR) spectra were measured in KBr on
1
a PE-580B spectrometer. H NMR spectra were recorded on a Bruker AM-500,
using dimethylsulfoxide (DMSO) as solvent and tetramethylsilane (TMS) as internal
reference. Elemental analyses were measured an the Elementar Vario EL III. X-ray
crystal data were collected with a Bruker Smart Apex2 CCD.
General Procedure for Preparing Spiro[indoline-3,4’(1’
H)-pyrano[2,3-c]pyrazol]-2-one Derivatives
A mixture of isatin 1 (2 mmol), malononitrile 2 (145 mg, 2.2 mmol),
2-pyrazolin-5-one 3 (2.2 mmol), and NaHCO3 (504 mg, 6 mmol) was ground at room
temperature with a glass mortar and pestle. The reaction was monitored by
thin-layer chromatography (TLC). The precipitate is collected by suction filtration
and washed with water. The product 4 was recrystallized from ethanol and dried
under room temperature.
Selected Data
6’-Amino-5’-cyano-3’-methyl-1’-phenylspiro[indoline-3,4’(1’H)-pyrano-
[2,3-C]pyrazole]-2-one (4a). Mp 219–220 ꢀC, lit. mp 220 ꢀC.[7] 1H NMR
(500 MHz, DMSO) d 1.54 (s, 3H, CH3), 6.93–6.95 (m, 1H, Ar-H), 7.01–7.04 (m,
0
1H, Ar-H), 7.17–7.19 (m, 1H, Ar-H), 7.27–7.30 (m, 1H, Ar-H), 7.33–7.37 (m, 1H,
Ar-H), 7.50–7.54 (m, 2H, Ar-H), 7.59 (s, 2H, NH2), 7.78–7.80 (m, 2H, Ar-H),
10.75 (s, 1H, NH). IR (potassium bromide) 3460, 3174, 2195, 1700, 1653 cmꢁ1
.

3624
Y. LIU ET AL.
6’-Amino-5’-cyano-3’-methyl-1’-phenylspiro[5-choro-indoline-3,4’(1’H)-
pyrano[2,3-C]pyrazole]-2-one (4b). Mp 223–224 ꢀC, lit. mp 230–232 ꢀC.[8] 1H
NMR (500 MHz, DMSO) d 1.59 (s, 3H, CH3), 6.95–6.97 (m, 1H, Ar-H),
7.33–7.37 (m, 3H, Ar-H), 7.51–7.54 (m, 2H, Ar-H), 7.65 (s, 2H, NH2), 7.77–7.79
(m, 2H, Ar-H), 10.90 (s, 1H, NH). IR (potassium bromide) 3367, 3186, 2204,
1706, 1658 cmꢁ1
.
6’-Amino-5’-cyano-3’-methyl-1’-phenylspiro[5-nitro-indoline-3,4’(1’H)-
pyrano[2,3-C]pyrazole]-2-one (4c). Mp 219–220 ꢀC, lit. mp 226–228 ꢀC.[8] 1H
NMR (500 MHz, DMSO) d 1.59 (s, 3H, CH3), 7.17–7.18 (m, 1H, Ar-H),
7.35–7.38 (m, 1H, Ar-H), 7.51–7.54 (m, 2H, Ar-H), 7.73 (s, 2H, NH2), 7.79–7.81
(m, 2H, Ar-H), 8.22–8.28 (m, 2H, Ar-H), 11.48 (s, 1H, NH). IR (potassium bromide)
3377, 3189, 2206, 1711, 1658 cmꢁ1
.
6’-Amino-5’-cyano-3’-methylspiro[indoline-3,4’(1’H)-pyrano[2,3-C]-
pyrazole]-2-one (4). Mp 279–280 ꢀC, lit. mp 275 ꢀC.[7] 1H NMR (500 MHz,
DMSO) d 1.53 (s, 3H, CH3), 6.89–6.91 (m, 1H, Ar-H), 6.98–7.04 (m, 2H, Ar-H),
7.23–7.26 (m, 3H, Ar-H, NH2), 10.60 (s, 1H, NH), 12.29 (s, 1H, NH). IR (potassium
bromide) 3459, 3175, 2195, 1700, 1654 cmꢁ1
.
6’-Amino-5’-cyano-3’-methylspiro[5-choro-indoline-3,4’(1’H)-pyrano-
[2,3-C]pyrazole]-2-one (4e). Mp 239–240 ꢀC, lit. mp 230–232 ꢀC.[8] 1H NMR
(500 MHz, DMSO) d 1.58 (s, 3H, CH3), 6.92–6.93 (m, 1H, Ar-H), 7.13–7.14 (m,
1H, Ar-H), 7.29–7.31 (m, 3H, Ar-H, NH2), 10.76 (s, 1H, NH), 12.35 (s, 1H, NH).
IR (potassium bromide) 3346, 3136, 2182, 1714, 1644 cmꢁ1
.
6’-Amino-5’-cyano-3’-methylspiro[5-bromo-indoline-3,4’(1’H)-pyrano-
1
[2,3-C]pyrazole]-2-one (4f). Mp 282–283 ꢀC. H NMR (500 MHz, DMSO) d 1.58
(s, 3H, CH3), 6.87–6.89 (m, 1H, Ar-H), 7.23–7.24 (m, 1H, Ar-H), 7.32 (s, 2H, NH2),
7.42–7.44 (m, 1H, Ar-H), 10.78 (s, 1H, NH), 12.35 (s, 1H, NH). IR (potassium bro-
mide) 3391, 3138, 2181, 1713, 1642 cmꢁ1. Anal. calcd. for C15H10BrN5O2: C, 48.41;
H, 2.71; N, 18.82. Found: C, 48.71; H, 2.81; N, 18.45.
6’-Amino-5’-cyano-3’-methylspiro[5-niro-indoline-3,4’(1’H)-pyrano[2,3-
1
C]pyrazole]-2-one (4g). Mp 270–271 ꢀC; H NMR (500 MHz, DMSO) d 1.58 (s,
3H, CH3), 7.13–7.15 (m, 1H, Ar-H), 7.43 (s, 2H, NH2), 7.91–7.92 (m, 1H, Ar-H),
8.23–8.25 (m, 1H), 11.37 (s, 1H, NH), 12.41 (s, 1H, NH); IR (potassium bromide)
3450, 3322, 2193, 1731, 1644 cmꢁ1. Anal. calcd. for C15H10N6O4: C, 53.26; H,
2.98; N, 24.84. Found: C, 53.36; H, 3.01; N, 24.49.
6’-Amino-5’-cyano-3’-phenylspiro[indoline-3,4’(1’H)-pyrano[2,3-C]-
1
pyrazole]-2-one (4h). Mp 219–220 ꢀC. H NMR (500 MHz, DMSO) d 6.73–6.75
(m, 1H, Ar-H), 6.79–6.81 (m, 2H, Ar-H), 6.89–6.92 (m, 1H, Ar-H), 7.03–7.05 (m,
1H, Ar-H), 7.14–7.18 (m, 3H, Ar-H), 7.24–7.27 (m, 3H, Ar-H, NH2), 10.49 (s,
1H, NH), 12.89 (s, 1H, NH). IR (potassium bromide) 3384, 3239, 2186, 1705,
1651 cmꢁ1. Anal. calcd. for C20H13N5O2: C, 67.60; H, 3.69; N, 19.71. Found: C,
67.31; H, 3.74; N, 19.95.
6’-Amino-5’-cyano-3’-phenylspiro[5-choro-indoline-3,4’(1’H)-pyrano[2,3-
1
C]pyrazole]-2-one (4i). Mp 247–249 ꢀC. H NMR (500 MHz, DMSO) d 6.73–6.75

SPIRO[INDOLINE-3,40(1H0)-PYRANO-[2,3-c]PYRAZOL]-2-ONE DERIVATIVES
3625
(m,1H, Ar-H), 6.85–6.87 (m, 2H, Ar-H), 7.13–7.14 (m, 1H, Ar-H), 7.19–7.22 (m, 3H,
Ar-H), 7.27–7.29 (m, 1H, Ar-H), 07.35 (s, 2H, NH2), 10.66 (s, 1H, NH), 12.94 (s, 1H,
NH). IR (potassium bromide) 3400, 3229, 2186, 1712, 1643 cmꢁ1. Anal. calcd. for
C20H12ClN5O2: C, 61.63; H, 3.10; N, 17.97. Found: C, 61.51; H, 3.11; N, 18.10.
6’-Amino-5’-cyano-3’-phenylspiro[5-bromo-indoline-3,4’(1’H)-pyrano-
[2,3-C]pyrazole]-2-one (4j). Mp 258–259 ꢀC. 1H NMR (500 MHz, DMSO) d
6.69–6.71 (m,1H, Ar-H), 6.85–6.86 (m, 2H, Ar-H), 7.19–7.34 (m, 7H, Ar-H, NH2),
10.66 (s, 1H, NH), 12.95 (s, 1H, NH). IR (potassium bromide) 3398, 3143, 2188,
1714, 1639 cmꢁ1. Anal. calcd. for C20H12BrN5O2: C, 55.32; H, 2.79; N, 16.13.
Found: C, 54.95; H, 2.85; N, 16.31.
6’-Amino-5’-cyano-3’-phenylspiro[5-niro-indoline-3,4’(1’H)-pyrano[2,3-
C]pyrazole]-2-one (4k). Mp 212–213 ꢀC. 1H NMR (500 MHz, DMSO) d 6.84–6.85
(m, 2H, Ar-H), 6.90–6.92 (m, 1H, Ar-H), 7.18–7.21 (m, 2H, Ar-H), 7.26–7.29 (m,
1H, Ar-H), 7.27–7.29 (m, 1H, Ar-H), 7.46 (s, 2H, NH2), 7.90 (s, 1H), 8.10 (s, 1H,
NH), 13.00 (s, 1H, NH). IR (potassium bromide) 3225, 2194, 1726, 1631 cmꢁ1. Anal.
calcd. for C20H12N6O4: C, 60.00; H, 3.02; N, 20.99. Found: C, 59.69; H, 3.10; N,
20.61.
ACKNOWLEDGMENTS
Thanks go to the National Natural Science Foundation of China (Nos.
20872088 and 21072126) and the Leading Academic Discipline Project of Shanghai
Municipal Education Commission (Grant No. J50102) for financial support.
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