New multicomponent domino reaction on water: highly diastereoselective synthesis of spiro[indoline-3,4′-pyrazolo[3,4-b]pyridines] catalyzed by NaCl
作者:Anshu Dandia、Ashok kumar Laxkar、Ruby Singh
DOI:10.1016/j.tetlet.2012.03.136
日期:2012.6
A direct and efficient approach for the preparation of medicinally promising pyrazolopyridinyl spirooxindoles has been developed through a sequential one-pot, three-component reaction of easily available isatin, alpha-cyanoacetic ester or malononitrile, and 5-amino-3-methylpyrazole catalyzed by sodium chloride in water. Desired products were obtained in high to excellent yields using a simple workup procedure. The product synthesized using alpha-cyanoacetic ester showed high diastereoselectivity in which the stereochemistry of major diastereomer was confirmed by X-ray diffraction analysis. The present green synthesis shows attractive characteristics such as the use of water as the reaction medium, one pot conditions, short reaction period, easy workup/purification, and reduced waste production, without use of any acid or metal promoters. (C) 2012 Elsevier Ltd. All rights reserved.
Regioselective, one-pot, multi-component, green synthesis of substituted benzo[<i>c</i>]pyrazolo[2,7]naphthyridines
An efficient and environmentally benign synthetic protocol has been developed for the synthesis of benzo[c]pyrazolo[2,7]naphthyridine derivatives through regioselective multi-component “on-water” reaction of isatin, malononitrile and 3-aminopyrazole. The Knoevenagel condensation of isatin with malononitrile resulted in the formation of arylidene, which subsequently underwent Michael addition with 3-aminopyrazole