2-aryl-l,2,3,4-tetrahydro-4-quinolone

Scheme 6.47 Synthesis of 2-aryl-l, 2,3,4-tetrahydro-4-quinolones via cyclization reaction on clay.

Aryl-l,2,3,4-tetrahydro-4-quinolones 348 can be dehydrogenated to the corresponding 4-quinolones 349 by using IBD-KOH/MeOH (94SC2167) (Scheme 89). Surprisingly, the expected product a-hydroxydimethylacetal 350 is not obtained. 

Alkoxy-2-arylquinolines 2-Aryl-l,2,3,4-tetrahydro-4-quinolones undergo dehydrogenation and O-methylation when treated with PhI(OTs)OH, HCIO, and HCjOMejj. 

Aminochalcones, which are readily available, provide easy access to 2-aryl-l,2,3,4-tetrahydro-4-quinolones in yet another solvent-free cydization reaction (internal Michael addition) using KIO clay under microwave irradiation conditions [179] the products are valuable precursors for medicinally important quinolones (Scheme 8.70). 

An easy access to 2-aryl-4-quinolone (85) has been achieved from 2-aryl-l,2,3,4-tetrahydro-4-quinolone (86) using hypervalent iodine as the oxidizing agent (Scheme 47) (94SC(24)2167). 

Singh, O.V., KapU, R.S. 1993. A new route to 2-aryM-quinolones via thallium(III) p-tol-ylsulphonate mediated oxidation of 2-aryl-l,2,3,4-tetrahydro-4-quinolones. Synthetic Communications 23 277-283. 

The oxidative aromatization of tetrahydro-5(l/f)-quinolinones and tetrahydropyrido [2,3-fif]pyrimidin-4(//)-one withpara-benzaldehydes as oxidants in NaOEt/EtOH results in the formation of the corresponding quinolone and aryl methanol because of the hydride transfer from tetrahydroquinoline to arylaldehydes during the oxidation process. The yield of the products basically depends on the substituents with -l-M effect attached to the para position of benzene rings connected to the 2- and 4-positions of the hydro-quinolinone moiety and substituents with -I effect attached to the aryl aldehydes. 

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