Quinoline-5,8-diones reactivity

Tu and co-workers [101] reported the synthesis of a series of novel pyrimido [5,4-6][4, 7]phenanthroline-9,11(7/7,8/7,10/7,12//)-diones 55 via a microwave-assisted three-component reaction of barbituric acid, an aldehyde and quinolin-6-amine in DMF without any catalyst. The results suggest that aldehydes bearing electron-withdrawing groups have higher reactivity providing higher yields in shorter reaction times (Scheme 41). 

Although 1-aza-l,3-dienes are somewhat reluctant to undergo [4+2] cycloadditions, a,3-unsaturated l drazones show increased reactivity with electrophilic dienophiles. behaving as 1-amino-l-aza-l,3-dienes. For example, the M-dimethylhydrazone derived from methacrolein gives a high yield of 3-methylbenzo[g]quinolin-5,10-dione (62) via the adduct (61) on reaction with an excess of naphtho-1,4-quinone (B. Serckx-Poncin, A.-M. Hesbain-Frisque and L. Ghosez, Tetrahedron Letters, 1982, 3261). 

Edmont D, Chenault J (2003) 8-Fluoro-4-hydroxy-l//-[l,2,4]triazino[4,5-a]-quinoline-l,6(2//)"dion - synthesis and reactivity. J Heterocycl Chem 40 789-793... 

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