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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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Published in: | Molecular diversity 2017-05, Vol.21 (2), p.283-291 |
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Main Authors: | , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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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 |
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ISSN: | 1381-1991 1573-501X |
DOI: | 10.1007/s11030-016-9719-2 |