Bronsted and Lewis Acid-Catalyzed Diverse Functionalization of Indenoquinoxaline-11-Propargyl Alcohols: Synthesis of 4-Indeno-quinoxalinylidene-2,3-diarylcyclobutenone, 1,2-Dimethoxy-2-Aryl-ethylideneindenoquinoxaline, and 2-Methoxy-1-phenyldiaza-benzocyclopentafluorenes

An efficient unprecedented synthesis of indenoquinoxaline-appended cyclobutenone derivatives has been developed from the reaction of indenoquinoxaline-11-propargyl alcohols using I2/BF3. OEt2 as a reagent system. On the other hand, the reaction using the combination of TMOF/p-TSA and I2/ TMOF/p-TSA as the reagent system afforded 1,2-dimethoxy-2-arylethylidene indenoquinoxaline and 2-methoxyphenyl diazabenzo-cyclopentafluorene, respectively. A plausible reaction mechanism is provided for the formation of all the products. All the compounds are characterized by spectroscopic data including single-crystal X-ray diffraction analysis.