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Urea/thiourea: efficient, inexpensive and reusable catalysts for the synthesis of pyrazole derivatives with 2-iminothiazolidin-4-one and 2,4-thiazolidinediones under solvent-free conditions

An efficient and green synthesis of pyrazolyl-2,4-thiazolidinediones/pyrazolyl-2-iminothiazolidine-4-ones 7 ( a – j ) has been developed using urea/thiourea as catalyst. Two methods (A and B) have been introduced for the synthesis of these compounds. Method A performed well for the condensation of p...

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Bibliographic Details
Published in:Molecular diversity 2017-05, Vol.21 (2), p.283-291
Main Authors: Konkala, Veera Swamy, Dubey, Pramod Kumar
Format: Article
Language:English
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Summary:An efficient and green synthesis of pyrazolyl-2,4-thiazolidinediones/pyrazolyl-2-iminothiazolidine-4-ones 7 ( a – j ) has been developed using urea/thiourea as catalyst. Two methods (A and B) have been introduced for the synthesis of these compounds. Method A performed well for the condensation of pyrazole-4-carboxaldehydes 4 ( a – e ) with 2-iminothiazolidin-4-one 5a and with 2,4-thiazolidinedione 5b at 110 ∘ C for 16–20 min to furnish (Z)-5-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)thiazolidine-2,4-diones 7 ( a – j ) in excellent yields. In method B, the pyrazole-4-carboxaldehydes 4 ( a – e ) were condensed with urea/thiourea at 110 ∘ C for 10 min to give key intermediates 6 ( a – j ) which were later condensed with 5a and 5b to afford 7 ( a – j ) via the elimination of urea/thiourea rather than the formation of a Biginelli product. These two protocols are inexpensive, eco-friendly and high yielding to provide the final products. Graphical Abstract The synthesis of compound 7f
ISSN:1381-1991
1573-501X
DOI:10.1007/s11030-016-9719-2