Palladium‐Catalyzed Dual Csp ² ─Csp ³ Bond Formation: A Versatile Platform for the Synthesis of Benzo‐Fused Heterocycles

Abstract Transition‐metal‐catalyzed transformations offer a powerful approach to rapidly synthesize complex benzo‐fused heterocycles, crucial for drug and material development. However, existing synthetic strategies face challenges such as limited functional group compatibility, reliance on complex ligands, and difficulties in controlling chemoselectivity with prefunctionalized substrates. Herein, a ligand‐free Pd(II)/Cu(I) catalytic system is presented that facilitates reactions between arylsulfonyl chlorides and unactivated olefins under mild conditions, enabling the efficient synthesis of saturated benzo‐fused six‐membered heterocycles. This streamlined strategy employs dual Csp ² ─Csp ³ bond formation, producing diverse N/O‐polyheterocycles and allowing late‐stage functionalization of bioactive molecules with excellent yields and high chemoselectivity. The key to the success of this reaction is the formation of high‐valent Ar‐Pd(III) intermediate, which drives the reaction through 1,2‐Pd migration and electrophilic C─H arylation. This unique reactivity pathway facilitates the formation of benzo‐fused heterocycles while effectively avoiding the β‐H elimination typically associated with Heck‐type reactions.