Synthesis of Indolo[1,2-a]quinoxalines and 2-Arylquinazolinones by Oxidative Aromatization from Aromatic Aldehydes or Benzyl Alcohols

Abstract We report a simple protocol for the synthesis of heterocyclic indoloquinoxalines and 2-naphthylquinazolinones by an oxidative aromatization from aromatic aldehydes or benzyl alcohols. For aromatic aldehydes, a diphenyl hydrogen phosphate/Cu(OTf)2/t-BuOOH system delivered the products in high yields (73–93%). From benzyl alcohols, a Fe(NO3)3·9H2O/(2,2,6,6-tetramethylpiperidin-1-yl)oxyl/air system was effective, and the products were obtained in moderate to high yields (51–75%). The indolo[1,2-a]quinoxaline compounds displayed fluorescence emission bands at 501–533 nm. Moreover, intramolecular hydrogen bonding was vital for the free rotation of the aryl–aryl bond in ortho-hydroxyindolo[1,2-a]quinoxalines.