Danel, A.; Porębska, E.; Markiel, K.; Havrysh, O.; Kucharek, M.; Gut, A.; Uchacz, T. Multicomponent Synthesis of 4-Aryl-4,9-dihydro-1H-pyrazolo [3,4-b]quinolines Using L-Proline as a Catalyst—Does It Really Proceed? Molecules2023, 28, 7612.
Danel, A.; Porębska, E.; Markiel, K.; Havrysh, O.; Kucharek, M.; Gut, A.; Uchacz, T. Multicomponent Synthesis of 4-Aryl-4,9-dihydro-1H-pyrazolo [3,4-b]quinolines Using L-Proline as a Catalyst—Does It Really Proceed? Molecules 2023, 28, 7612.
Danel, A.; Porębska, E.; Markiel, K.; Havrysh, O.; Kucharek, M.; Gut, A.; Uchacz, T. Multicomponent Synthesis of 4-Aryl-4,9-dihydro-1H-pyrazolo [3,4-b]quinolines Using L-Proline as a Catalyst—Does It Really Proceed? Molecules2023, 28, 7612.
Danel, A.; Porębska, E.; Markiel, K.; Havrysh, O.; Kucharek, M.; Gut, A.; Uchacz, T. Multicomponent Synthesis of 4-Aryl-4,9-dihydro-1H-pyrazolo [3,4-b]quinolines Using L-Proline as a Catalyst—Does It Really Proceed? Molecules 2023, 28, 7612.
Abstract
Looking for effective synthetic methods for 1H-pyrazolo[3,4-b]quinolines preparation, we came across a procedure where in a three component reaction catalyzed by L-proline, 4-aryl-4,9-dihydro-1H-pyrazolo[3,4-b]quinolines are formed. These compounds can be easily oxidized to a fully aromatic system, which gave hope for a synthetic method that could replace e.g. Friedländer condensation, often used for this purpose, although severely limited by the availability of suitable substrates. However, after careful repetition of the procedures described in the publication, it turned out that the compounds described therein do not form at all. The actual compounds turned out to be 4,4-(phenylmethylene)-bis-(3-methyl-1-phenylpyrazol-5-oles). 4-Aryl-4,9-dihydro-1H-pyrazolo[3,4-b]quinolines were prepared by another method and used as standards to compare the products formed in the original procedure.
Chemistry and Materials Science, Organic Chemistry
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