Development of simple methods for the preparation of heterocycle-fused quinones and their application to the synthesis of natural products

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1H-Naphtho[2, 3-c]pyran-5, 10-dione derivatives, including a natural product (pentalongin), were generally synthesized in one-pot using a tandem conjugate addition-cyclization sequence between 2-(1-hydroxylkyl)-1, 4-naphthoquinones and enamines (or imines). The utility of this method was demonstrated in the synthesis of pyranonaphthoquinone antibiotics, (±)-eleutherin and (±)-isoeleutherin.The reaction of 2-hydroxy-1, 4-naphthoquinones with 0-fluoronitrobenzenes in the presence of KィイD22ィエD2COィイD23ィエD2 in DMSO gave 2-hydroxy-3-(2-nitroaryl)-1, 4-naphthoquinones in fair yields, which in turn were transformed into the corresponding 11H-benzo[a]carbazole-5, 6-dione and 5H-benzo[b]carbzole^6, 11-dione derivatives in good yields by catalytic hydrogenation over PtOィイD22ィエD2 in AcOEt, followed by exposure to air and then heating at reflux temperature.Naphtho[2, 3-b]thiophene-4, 9-quinones were generally synthesized in one-pot using a tandem conjugate addition-cyclization sequence between 2-[2 … More -(ethoxycarbonyl)-ethyl]thio-1, 4-naphthoquinone and enamines, derived from cyclic and acyclic ketones.The reaction of 4-hydroxy-2H-pyran-2-one derivatives with a range of alkenes or phenylacetylene in acetonitrile containing cerium(IV) ammonium nitrate (CAN) afforded the corresponding furo[3, 2-c]pyranone and/or furo[2, 3-b]pyranone derivatives. Similar treatment of 4-hydroxy-1-methylquinolin-2(1H)-one with alkenes or phenylacetylene in the presence of CAN gave furo[3, 2-c]quinolin-4(5H)-one derivatives.2-Acetyl-1, 4-naphthoquinone was treated with pyrrolidine (or morpholine) enamines, derived from cyclic and acyclic ketones, in DMF at room temperature for 24-72 h to afford 3, 4-distributed 1-pyrrolidino(or morpholino)-9, 10-anthraquinones. On the other hand, when the treatment of 2-acetyl-1, 4-naphthoquinone with enamines for 2 min was followed by addition of water and heating at 100℃ for 2 h, the corresponding 1-hydroxy-9, 10-naphthoquinone derivatives were obtained.The reaction of 1, 3-dimethylpyrimidine-2, 4, 6(1H, 3H, 5H)-trione with various alkenes or terminal alkynes in the presence of cerium(IV) ammonium nitrate (CAN) afforded the corresponding 5, 6-dihydrofuro[2, 3-d]pyrimidine-2, 4(1H, 3H)-diones or furo[2, 3-d]pyrimidine-2, 4(1H, 3H)-diones in moderate to good yields. Less