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A highly efficient synthesis of 4H-pyrano[2,3-c]pyrazoles has been completed using four-component cyclocondensation of hydrazine monohydrate/phenyl hydrazine, ethyl acetoacetate, aldehydes, and malononitrile in the presence of L-proline and room-temperature ionic liquids.
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Khurana et al. (2011) studied this question.
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