Metal‐Free Bicyclization for the Construction of N−O Fused Tetracyclic Isoquinolones

Abstract A hypervalent iodine‐mediated bicyclization of N‐alkoxybenzamides for the synthesis of polyheterocycles is reported. Through metal‐free strategy, various N−O fused tetracyclic isoquinolones are synthesized in moderate to good yields at room temperature. The tetracyclic isoquinolones show good fluorescent properties, with maximum emission wavelength ranging from 442 to 459 nm. Notably, preliminary antifungal activity investigations indicate that N−O fused tetracyclic isoquinolones show good activities towards crop and forest pathogenic fungi. One of them exhibits 75.9 % antifungal activity towards C. chrysosperma , which is much better than the positive control.