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Issue 4, 2013
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Ionic liquid promoted spiroannulation via hetero-Michael addition and intramolecular heterocyclisation

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Abstract

A sequential efficient method for the synthesis of novel spiro-5-thiazolidin-2-one-indolo[1,5]benzothiazepine from readily available isatin, 4-thioxothiazolidin-2-one and 2-aminothiophenol is reported. The synthesis involves formation of N-methyl-3-(2-oxo-4-thioxothiazolidinon-5-ylidene)-1,3-dihydro indol-2-one by [bmIm]OH promoted Knoevenagel condensation of 4-thioxo-2-thiazolidinone with isatin. The Knoevenagel product on ionic liquid promoted thia-Michael addition with 2-aminothiophenol and intramolecular cyclocondensation yielded the title compounds with high atom economy. The ionic liquid, [bmIm]OH was recovered completely and recycled thrice for the synthesis with no appreciable decrease in the efficiency of the process. The whole sequence of reactions proceeded with quantitative transformation of reactants into spiro [1,5]benzothiazepine at ambient temperature. The sequential reaction pathway is supported by the isolation of the thia-Michael adduct of the knoevenagel product with 2-aminothiophenol and quantitative conversion of the adduct into the final products under the same reaction conditions.

Graphical abstract: Ionic liquid promoted spiroannulation via hetero-Michael addition and intramolecular heterocyclisation

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Article information


Submitted
23 Nov 2012
Accepted
05 Feb 2013
First published
06 Feb 2013

New J. Chem., 2013,37, 1258-1263
Article type
Paper

Ionic liquid promoted spiroannulation via hetero-Michael addition and intramolecular heterocyclisation

I. R. Siddiqui, Shireen, S. Shamim, A. A. H. Abumhdi, M. A. Waseem, A. Srivastava, Rahila and A. Srivastava, New J. Chem., 2013, 37, 1258
DOI: 10.1039/C3NJ41070F

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