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

Molecules

Margita Lผová²  Agnieszka Puchala³  Eva Solლnyova⁴  Jan Lac¹  Pavol Koiš²  Jarmila Chovancová² 

[1] EML Research, Villa-Bosch, Germany;Department of Organic Chemistry Faculty of Natural Sciences, Comenius University, Slovakia;Institute of Chemistry, Swietokrzyska Academy, Poland;Institute of Chemistry, Faculty of Natural Sciences, Comenius University, Slovakia

关键词: 4-Oxo-4H[1]benzopyrane;    Coumarin;    Pyrazole;    Rearrangement;    Enamine;    Microwave irradiation;   

DOI  :  10.3390/10070809

来源: mdpi

【 摘 要 】

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.

【 授权许可】

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