Efficient construction of 3-arylquinolin-4(1 H )-ones via in situ Meinwald rearrangement/intramolecular reductive cyclization of 2′-nitrochalcone epoxides
An efficient method for construction of 3-arylquinolin-4(1H)-ones via in situ Meinwald rearrangement/intramolecular reductive cyclization of 2′-nitrochalcone epoxides has been developed. The practical approach is of excellent functional groups compatibility with as high as 98% yield under mild reaction conditions. Trapping and NMR analysis about the key intermediates of the transformation provided
An unprecedented TfOH-promoted tandem ring-closure-aryl-migration of 2′-amino chalcone epoxide leading to 3-aryl-4(1H)-quinolones (azaisoflavones) was achieved. The outcome of the reaction was confirmed by NMR analysis and rationalized through the intermediacy of a phenonium ion. This synthetic protocol furnishes azaisoflavones straightforwardly from simple starting materials under mild conditions.
Fabrication of a synthetic azaisoflavone skeleton from 2'-nitrochalcone was done using oxidative rearrangement with a hypervalent iodine reagent. A key intermediate compound, aminoacetal, was prepared from readily available 2'-nitrochalcone via a PhI(OH)OTs-mediated rearrangement, followed by reduction of the nitro group. A variety of azaisoflavones were obtained in moderate to high yields by treatment of the intermediate compound under acidic conditions.