Pyrazolo quinolines, formation

Pyrazolo[3,4-Z)]pyridines, the 7-chloro-6-fluoro-2,4-dimethylquinoline and its mercapto-thiadiazolyl or oxadiazolyl quinolines 21 were prepared via Diels-Alder reaction conversion of methyl 2-(3-oxo-3-phenylpropenylamino)benzoate into 3-benzoyl-l.S -quinolin-4-one 22 . A mixture of aniline derivatives and malonic ester gave a variety of 3-aryl-4-hydroxyquinolin-2(l//)-ones 23. Condensation of isatins with ketones afforded quinoline-4-carboxylic acids. 2-Aryl-l,2,3,4-tetrahydro-4-quinolinones 22 and carbazolylquinolone were also prepared. The substitution of 2-chloroquinoline gave the 2-substituted quinolines. Basic alumina has catalyzed the C-C bond formation between 2-hydroxy-1,4-naphthoquinone and 2-chloroquinoline derivative to give 21. Reaction of organic halides with 8-hydroxyquinolines gave the respective ethers. The azodye derivatives of 21 were prepared in the absence of solvent. Silica gel catalyzed the formation of 2-ketomethylquinolines from reaction of 2-methylquinolines with acyl chlorides. 

Pyrazolo[3,4-fo]quinolines and pyrazolo[3,4-c]pyrazoles have been synthesized by microwave irradiation of j5-chlorovinylaldehydes and hydrazines in the presence of p-toluenesulfonic acid (PTSA) under solvent-free conditions (Scheme 8.30) [92] via hydrazone formation and sequential cyclization. 

Cyclocondensation takes place on reacting 6-nitroquinoline with substituted hydrazones 69 (Scheme 34) in the presence of NaH in DMF, thus giving rise to 3-aryl-l(3)H-pyrazolo[3,4-f]quinolines 70 and/or 3-aryl[1.2.4]triazino[6,5-f] quinolines 71 [63, 64]. Yields are varied from low to moderate, while the direction of the reaction depends mainly on the structure of hydrazones electron-donating groups in the benzene ring of hydrazones favor the triazine ring formation. 

In 2006, Fadda et al. reported the piperidine-catalyzed reaction of l-chloro-3,4-dihydronaphthalene-2-carboxalde-hyde 53 with pyrazole 52 and malonodinitrile 21 to provide an access to a chromeno[2,3-c]pyrazole 55 at high temperatures (Scheme 13.17) [28]. Exchange of the piperidine catalyst by an excess of ammonium acetate led to the formation of a pyrazolo[3,4-b]quinoline derivative 54 instead. 

Yet another multicomponent domino reaction assisted by MW irradiation has been developed for the rapid and regi-oselective synthesis of highly functionalized benzo[/i]pyrazolo[3,4-l ]quinolines and their derivatives [63] (Scheme 41). A mechanism explaining the formation of this compoxmd has been proposed by the autifors (Scheme 40). The resulting benzoquinoline products have been successfully converted into quinoxaline-fused benzo[/i]isoxazolo[5,4-l7]quinolines by reacting with benzene-l,2-diamine xmder MW irradiation. 

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