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 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.
Lácová
Margita
M
Department of Organic Chemistry, Faculty of Natural Sciences, Comenius University, SK-842 15 Bratislava, Slovakia. lacova@fns.uniba.sk
Puchala
Agnieszka
A
Solcanyova
Eva
E
Lac
Jan
J
Kois
Pavol
P
Chovancova
Jarmila
J
Rasala
Danuta
D
D000588:Amines / Q000737:chemistry; D002864:Chromogranins / Q000737:chemistry* / Q000494:pharmacology; D002867:Chromones / Q000737:chemistry*; D003374:Coumarins; D008826:Microbial Sensitivity Tests; D011720:Pyrazoles / Q000138:chemical synthesis* / Q000494:pharmacology; D011725:Pyridines / Q000138:chemical synthesis* / Q000494:pharmacology; D011743:Pyrimidines / Q000138:chemical synthesis* / Q000494:pharmacology
D000588:Amines; D002864:Chromogranins; D002867:Chromones; D003374:Coumarins; D011720:Pyrazoles; D011725:Pyridines; D011743:Pyrimidines; C502480:formylchromone; C030123:coumarin