Substrate-Controlled Copper-Catalyzed Regiodivergent Carboarylation-Ring Closure of Alkynyl Benzylphosphonates with Diaryliodonium Salts

Herein, we report a copper-catalyzed, substrate-controlled regiodivergent carboarylation-ring closure of alkynyl benzylphosphonates with diaryliodonium salts. This protocol provides access to a range of 1,2-oxaphosphepine 2-oxides and phosphaisocoumarins in moderate to good yields from the same class of substrates. The electronic nature of the substituent on the alkyne moiety plays a key role in controlling regioselectivity: alkynyl benzylphosphonates bearing electron-donating groups selectively afford 1,2-oxaphosphepine 2-oxides, whereas substrates bearing electron-withdrawing groups furnish the corresponding phosphaisocoumarins.