3-Acyl-4-hydroxy-2(1H)-quinolones 5 are obtained by hydrolytic ring opening and subsequent decarboxylation from the corresponding pyrano[3,2-c]quinolin-2,5(6H)-diones 4, which in turn are easily obtained from 1:2 condensation of anilines 1 with diethyl malonate 2a or 1:1 condensation of diethyl alkyl- or arylmalonates 2b-e with 4-hydroxy-2(1H)-quinolones 3. Nitropyranoquinolinediones 6 furnish after ringopening 3-nitroacetyl-4-hydroxy-2(1H)quinolones 8. Pyranoquinolines 7 and 9 with acetyl- or aminosubstituents are hydrolyzed during basic ringopening to yield 5.
3-Acyl-4-hydroxy-2(1H)-quinolones 5 are obtained by hydrolytic ring opening and subsequent decarboxylation from the corresponding pyrano[3,2-c]quinolin-2,5(6H)-diones 4, which in turn are easily obtained from 1:2 condensation of anilines 1 with diethyl malonate 2a or 1:1 condensation of diethyl alkyl- or arylmalonates 2b-e with 4-hydroxy-2(1H)-quinolones 3. Nitropyranoquinolinediones 6 furnish after ringopening 3-nitroacetyl-4-hydroxy-2(1H)quinolones 8. Pyranoquinolines 7 and 9 with acetyl- or aminosubstituents are hydrolyzed during basic ringopening to yield 5.
A simple and effective method for the reduction of acyl substituted heterocyclic 1,3-dicarbonyl compounds to alkyl derivatives by zinc - acetic acid - hydrochloric acid
3-Acyl-4-hydroxy-2(1H)-quinolones (1a–k) were reduced in good yields (66–97%) to 3-alkyl-4-hydroxy-2(1H)-quinolinones (2a–k) using zinc powder (particle size <45 μm) in acetic acid/hydrochloric acid. This method could be transformed to 3-acetyl-4-hydroxy-coumarin (1l), 3-acetyl-4-hydroxy-2-pyranone (3a) and 3-acetyl-4-hydroxy-2(1H)-pyridinone (3b), which yielded the 3-ethyl derivatives 2l, 4a and 4b, respectively