A Diels-Alder strategy for the building of imidazo[4,5-g]quinoline-4,9-dione derivatives

Benzimidazole-4,7-diones 3a and 3b were synthesized and submitted to hetero Diels–Alder reactions with azadienes 4 and 5 to afford imidazo[4,5-g]quinoline-4,9-diones 6–9. The structure of the latter was assigned by X-ray diffraction, 1H NMR NOE DIFF experiments or by a molecular dynamics study. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)