Friedländer condensation of 1H‐pyrazolin‐5‐ones with O‐aminobenzaldehydes. Synthesis of 1H‐pyrazolo[3,4‐B]quinolines

Abstract

All the possible 1‐ and 3‐monomethyl, monophenyl, dimethyl, diphenyl, and methylphenyl‐1H‐pyrazolin‐5‐ones have been condensed with o‐aminobenzaldehyde. In some cases (but not all) 1‐H‐pyrazolo[3,4‐b]quinolines (10) are formed together with a variety of other products. The balance between formation of hydrazone 11 and the ring‐closed 10 is discussed, as is the formation of other products obtained in these condensations.

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

“…This method provides a convenient synthesis of 4-substituted-1H-pyrazolo [3,4-b]quinoline derivatives which otherwise would be available with difficulty using a classical Friedländer synthesis 13 .…”

Some spirobiindane based 1H-pyrazolo [3,4-b] quinoline chromophore as novel chromophore for light-emitting diodes

“…The alternative way of the synthesis is heating of 2 with 6-fluorosubstituted pyrazoloquinolines 6a-d in the presence of anhydrous K 2 CO 3 in an NMP. The unsubstituted 1H-pyrazolo [3,4-b] quinolines 6i-l, their 6-phenoxy derivatives 6e-h, and fluoro-derivatives 6a-d were prepared in similar way according to the literature procedures [24][25][26].…”

The synthesis of 4-aryl-1H-pyrazolo[3,4-b]quino­lines by cyclization of 4-arylidenepyrazolin-5-ones with anilines

“…Thus, this synthesis appears to be very convenient for preparation of 4-arylpyrazolo [3,4-b]quinolines. 2 Friedländer condensation as an alternative route to such compounds involves 2-aminobenzophenones and pyrazolin-5-ones, 3,4 however availability of 2-aminobenzophenones limits the range of applicability of this reaction.…”