3-Formylchromones IV. The rearrangement of 3-formylchromone enamines as a simple, facile route to novel pyrazolo[3,4-b]pyridines and the synthetic utility of the latter

One-pot and facile preparations of 6-(2-hydroxy-5-R-benzoyl)-4-methyl-2-R1- pyrazolo[3,4-b]pyridines 4a-o are described, using the reaction of 3-formyl chromones 1 with 5-amino-1-R1-pyrazoles 2. An enamine-intermediate 2-ethyloxy-6-R-3-(3-methyl-1- phenylpyrazol-5-ylaminomethylene)chroman-4-one 3 wa...

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Published in:Molecules (Basel, Switzerland) Switzerland), 2005-08, Vol.10 (7), p.809-821
Main Authors: Lácová, Margita, Puchala, Agnieszka, Solcanyova, Eva, Lac, Jan, Kois, Pavol, Chovancova, Jarmila, Rasala, Danuta
Format: Article
Language:English
Subjects:
4-Oxo-4Hbenzopyrane
Amines - chemistry
Chromogranins - chemistry
Chromogranins - pharmacology
Chromones - chemistry
Coumarin
Coumarins
Enamine
Ethanol
Microbial Sensitivity Tests
Microwave irradiation
Pyrazole
Pyrazoles - chemical synthesis
Pyrazoles - pharmacology
Pyridines - chemical synthesis
Pyridines - pharmacology
Pyrimidines - chemical synthesis
Pyrimidines - pharmacology
Rearrangement
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Summary:One-pot and facile preparations of 6-(2-hydroxy-5-R-benzoyl)-4-methyl-2-R1- pyrazolo[3,4-b]pyridines 4a-o are described, using the reaction of 3-formyl chromones 1 with 5-amino-1-R1-pyrazoles 2. An enamine-intermediate 2-ethyloxy-6-R-3-(3-methyl-1- phenylpyrazol-5-ylaminomethylene)chroman-4-one 3 was isolated at lower temperatures. Acyloxy-derivatives 5 of compounds 4 were obtained by acylation with acid chlorides or acid anhydrides. Coumarins 6 substituted at the 3- and 4-positions were prepared from the pyrazolo[3,4-b]pyridines 4 by condensation reactions and hydrazones 7 were formed from their reaction with 2,4-dinitrophenyl hydrazine. Reactions under microwave irradiation proceeded significantly faster and with high yields.
ISSN:1420-3049
1420-3049
DOI:10.3390/10070809