1‐Phenyl‐1,2‐benziodoxol‐3‐(1<i>H</i>)‐one as Synthon for Phthalide Synthesis through Pd‐Free, Base‐Free, Sonogashira‐Type Coupling Cyclization Reaction

Abstract

Hypervalent iodine(III) five‐membered heterocycles have found broad application as atom‐transfer reagents for organic synthesis. Among them, 1‐phenyl‐1,2‐benziodoxol‐3‐(1 H )‐one is known as a traditional benzyne precursor, but no further synthetic applications have been reported. Herein, we report the first synthetic application of 1‐phenyl‐1,2‐benziodoxol‐3‐(1 H )‐one to the synthesis of phthalides by using only Cu I as catalyst. High selectivity and yields were achieved under mild reaction conditions with good functional group tolerance. During our investigations, the efficiency of different Cu I and Cu II catalysts under various reaction conditions were studied. The nature of the leaving group, the substituents on the substrate, and the temperature play an important role on both yield and selectivity. Moreover, a plausible mechanistic pathway for this transformation was proposed based on our observations and previous literature reports.