Fused Seven-Membered Carbocycle Construction through Electrochemical Relay Cyclization

Seven-membered carbocycles, which are frequently associated with relevant biological activities, can be found in nature and drugs in ever-increasing numbers. Radical cascade addition of 1,n-enynes-like substrates is one of the most important and efficient strategies for the synthesis of this valuable skeleton with structural diversity and complexity. Herein, we describe an electrooxidative radical-mediated synthesis of dibenzocycloheptanes from ortho-ethynyl-substituted biaryls and tertiary C(sp³)-H containing reactants. The chemo- and regioselective addition of in situ generated carbon radical onto the alkynyl moieties triggers a desired reaction cascade, resulting in the formation of three new C-C bonds. This approach provides a step-economical regime for the facile assembly of a wide range of polycyclic products containing a 6-7-5 system. This green strategy features a good substrate scope, mild conditions, and high efficiency under ferrocene-mediated electrochemical oxidation conditions.