278 RESEARCH PAPER
MAY, 278–279
JOURNAL OF CHEMICAL RESEARCH 2008
Sulfamic acid catalysed one-pot three-component condensation for the
synthesis of 1,4-dihydropyrano[2,3-c]pyrazoles
Sandeep V. Shindea, Wamanrao N. Jadhava, Jeevan M. Kondreb, Sumit V. Gampawarb and
Nandkishor N. Karadeb*
aDnyanopasak College, Parbhani 431 401, Maharashtra, India
bSchool of Chemical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431 606, Maharashtra, India
A clean and simple synthesis of 6-amino-4-aryl-3-methyl-1-phenyl-1,4-dihydropyrano[2,3-c]pyrazole-5-carbonitriles
was accomplished in good to excellent yields via the one-pot three component condensation of 3-methyl-1-phenyl-
2-pyrazolin-5-one, an aromatic aldehyde, and malononitrile catalysed by sulfamic acid in ethanol.
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intermediates due to their biological and pharmacological
properties such as antibacterial, molluscicidal, anthelminitic,
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also a structural unit of a number of natural products.11-13
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emerged as a useful acid imparting high regio- and chemo-
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one-pot three-component condensation of malononitrile, an
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Scheme 1 1,4-Dihydropyrano[2,3-c]pyrazoles.
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three component condensation to form the corresponding
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the references reported. For example, the IR spectra for 4a
exhibited sharp bands at 3471, 3257 cm–1 due to NH2 and
2198 cm–1 due to CN. The 1H NMR spectrum of 4a exhibited
a characteristic peak at G = 4.62 ppm for H-4 and a broad
singlet peak at G = 6.71 ppm due to the NH2 group.
A tentative reaction mechanism for the three-component
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to the above stirred reaction mixture at room temperature,
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stirring of the reaction mixture for 3–5 h did not result in the
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* Correspondent. E-mail: nnkarade2007@rediffmail.com