JOURNAL OF CHEMICAL RESEARCH 2008
MAY, 287–288
RESEARCH PAPER 287
Synthesis of indolones and quinolones by reductive cyclisation of
o-nitroaryl acids using zinc dust and ammonium formate
Bhima Reddy Dinesha, A. Ramesha Babaa, K. Udaya Sankarb and D. Channe Gowdaa*
aDepartment of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore-570 006, Karnataka, India
bFood Engineering Department, Central Food Technological Research Institute, Mysore-570 013, India
A novel protocol for the synthesis of indolone and quinolone derivatives from o-nitroaryl acids was developed
using Zn and HCO2NH4 under supercritical fluid carbon dioxide (scCO2) medium. The process involves the reduction
of the nitro group to an amino group followed by in situ cyclisation.
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nature and the use of Fe and Sn results in the generation of
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transformations.7,8 In addition, aromatic nitro compounds
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the corresponding anilines.9ꢀ 7KHUHIRUHꢁꢀ ZHꢀ WKRXJKWꢀ WKDWꢀ WKHꢀ
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reactions10,11 because of its versatile properties like, (i)
solubilising immiscible reactants in a single supercritical phase
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phase to dense supercritical medium13 and extraction of
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larger surface area.
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A continuous increase in the temperature and pressure of
CO2 to a critical condition resulted in the formation of 2a.
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also acts as a medium for the reaction. As it can be seen in
Table 1, the reaction time, temperature and the pressure of
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does not stabilise in carbon dioxide and failed to keep up the
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indolones (2a–gꢆꢀ RUꢀ TXLQRORQHVꢀ ꢅ4a–dꢆꢀ ZLWKꢀ JRRGꢀ \LHOGVꢀ
(70–82%). In the case of oꢃQLWURFLQQDPLFꢀDFLGꢁꢀLWꢀLVꢀQRWꢀRQO\ꢀ
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methoxide are tolerated.
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HCO2NH4 under scCO2 protocol for the smooth reductive
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Table 1 Reduction of o-nitrophenyl acetic acid to 1,3-dihydro-
2-indolone under various conditionsa
Entry
P/MPa
T/h
T/˚C
Yieldb/%
1c
2c
3
0
0
1
1
30
50
50
50
50
50
50
0
Trace
24
Results and discussion
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ꢇꢁꢈꢃGLK\GURꢃꢉꢃLQGRORQHꢀ ꢅ2a) from oꢃQLWURSKHQ\ODFHWLFꢀ DFLGꢀ
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different temperature and pressure of CO2 (Table 1). In the
presence of CO2 at atmospheric pressure and temperature,
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8
0.5
1
4
8
56
5d
6
12
12
12
1
62
1
74
7e
1
15
ao-nitrophenyl acetic acid (10 mmol), zinc dust (20 mmol),
ammonium formate (20 mmol). bIsolated. cIn presence of
carbon dioxide. dWithout silica gel. eAddition of water as co-
solvent (2–3 ml).
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