6-Exo-dig cyclization/dearomatization cascade towards N–O fused spiro polyheterocycles

Abstract

Herein, we present a metal-free cascade cyclization of alkyne-tethered N-alkoxybenzamides for the construction of structurally novel polyheterocycles. By using a hypervalent iodine(III) reagent, diverse N–O fused spiro polyheterocycles are generated in good to high yields via a 6-exo-dig cyclization/dearomatization process. This approach features ambient reaction temperature, short reaction times, broad substrate scope and easy handling procedures. Importantly, preliminary antifungal activity studies suggest that N–O fused spiro polyheterocycles display good activities towards crop and forest pathogenic fungi, one of which shows 93.3% antifungal activity towards C. chrysosperma, which is much better than the positive control.