Synthesis of tetracyclic 4H‐benzo[5,6]chromeno[3,4‐d]oxazoles via palladium‐catalyzed intramolecular direct heteroarylation

We report a palladium‐catalyzed intramolecular direct heteroarylation of oxazole tethered β‐naphthols to access corresponding tetracyclic 4H‐benzo[5,6]chromeno[3,4‐d]oxazoles. Various functional groups are well tolerated and furnished the desired products in good to excellent yields under the present reaction conditions. The scale‐up reaction and synthetic utility of the resulting molecules have been demonstrated. Moreover, UV/vis absorption and fluorescence emission properties have been evaluated for these polyheterocyclic compounds. An efficient method is disclosed for the synthesis of various tetracyclic 4H‐benzo[5,6]chromeno[3,4‐d]oxazoles from oxazole tethered β‐naphthols via intramolecular direct heteroarylation by employing a palladium catalyst. Furthermore, photophysical properties of the resulting molecules were evaluated by using UV/vis absorption and fluorescence spectroscopy.