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|Title: ||Synthesis of novel pyrazolo[3,4-b]quinolinebisphosphonic acids and an unexpected intramolecular cyclization and phosphonylation reaction|
|Authors: ||Teixeira, António P. S.|
Teixeira, Fátima C.
Curto, M. João M.
Duarte, M. Teresa
|Issue Date: ||Feb-2021|
|Publisher: ||The Royal Society of Chemistry|
|Citation: ||Fátima C. Teixeira, Carla Lucas, M. João M. Curto, Vânia André, M. Teresa Duarte and António P. S. Teixeira, Synthesis of novel pyrazolo[3,4-b]quinolinebisphosphonic acids and an unexpected intramolecular cyclization and phosphonylation reaction, Org. Biomol. Chem., 2021, 19, 2533-2545.
|Abstract: ||Novel pyrazolo[3,4-b]quinoline α-ketophosphonic and hydroxymethylenebisphosphonic acid compounds
were synthesized using diﬀerent methodologies, starting from 2-chloro-3-formylquinoline 1. New phosphonic
acid compounds were obtained as N-1 derivatives with a side chain with 1 or 3 (n = 1 or 3) methylene
groups. All phosphonic acid compounds and their corresponding ester and carboxylic acid precursors
were fully characterized, and their structures elucidated by spectroscopic data, using NMR techniques
and infrared and high-resolution mass spectroscopy. During the process to obtain the N-1 substituted
derivative with two methylene groups (n = 2) in the side chain, an unexpected addition–cyclization
cascade reaction was observed, involving the phosphonylation of an aromatic ring and the formation of a
new six-member lactam ring to aﬀord a tetracyclic ring system. This was an unexpected result since other
pyrazolo[3,4-b]quinoline derivatives and all corresponding pyrazolo[3,4-b]pyridine derivatives already prepared, under similar experimental conditions, did not undergo this reaction. This domino reaction occurs with diﬀerent phosphite reagents but only aﬀords the six-member ring. The spectroscopic data allowed the identiﬁcation of the new synthesized tetracyclic compounds and the X-ray diﬀraction data of compound 11 enabled the conﬁrmation of the proposed structures.|
|Appears in Collections:||CQE - Publicações - Artigos em Revistas Internacionais Com Arbitragem Científica|
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