Microwave-assisted, facile route to 1H-pyrazolo[3,4-b]quinolines

Abstract

Aromatic aldehydes have been reported to react with 5-anilinopyrazoles in the presence of ZnCl 2 to give the corresponding benzylidenopyrazoles. In this paper evidence is given that the corresponding products are, in fact, 1H-pyrazolo [3,4-b]quinolines. This observation opens a novel route to these compounds. They show a blue emission in the solid state and, therefore, they are useful blue luminophores for electroluminescent devices. The synthetic procedure reported in the literature was significantly modified and improved by application of microwave heating. In our modified synthesis the reaction time was reduced from the usual 5 to 8 h to 5 to 7 min and the reaction products were formed without contamination.

Multicomponent Synthesis of 4-Aryl-4,9-dihydro-1H-pyrazolo[3,4-b]quinolines Using L-Proline as a Catalyst—Does It Really Proceed?

“…The author reported in the publication that he obtained two derivatives of this kind. However, later research by Tomasik et al showed that the actual products formed in this reaction were 1H-pyrazolo [3,4-b]quinolines 7 [32].…”

“…However, later research by Tomasik et al showed that the actual products formed in this reaction were 1H-pyrazolo[3,4-b]quinolines 7[32].…”

1H-Pyrazolo[3,4-b]quinolines: Synthesis and Properties over 100 Years of Research

“…The syntheses described by Michaelis were repeated, and the chemical structures of the compounds that were obtained were analysed by using 1 H NMR spectroscopy. It turned out that the structure of Michaelis 134 did not correspond to any of the compounds that he received, but that it did match the pyrazoloquinolines of 65 [87].…”

“…The syntheses described by Michaelis were repeated, and the chemical structures of the compounds that were obtained were analysed by using 1 H NMR spectroscopy. It turned out that the structure of Michaelis 134 did not correspond to any of the compounds that he received, but that it did match the pyrazoloquinolines of 65 [87]. In 1911, Michaelis heated 5-N-arylamino-1,3-disubstituted pyrazoles 132 with some aromatic aldehydes 133 in the presence of anhydrous ZnCl 2 and obtained compounds to which he assigned a structure 134 (Scheme 37) [1].…”

Synthesis and characterization of some heterocyclic including oxazoles,Thiazoles, Pyridazines, phthalizines and Pyrazoles with evaluating of biological activity.

“…Reaction of acid hydrazide and its derivatives reacted with ethylaceto acetate or acetyl acetone or diethyl malonate produced pyrazole derivatives (13) .…”