Radical‐Enabled Bicyclization Cascades of Oxygen‐Tethered 1,7‐Enynes Leading to Skeletally Diverse Polycyclic Chromen‐2‐ones

Catalytic bicyclization cascades of oxygen‐tethered 1,7‐enynes with simple cycloalkanes or aryl sulfonhydrazides have been established via subsequent multiple C‐C bond‐forming events from alkynyl/alkenyl functions, delivering a series of densely functionalized tetracyclic chromen‐2‐ones in a functional‐group‐compatible manner. In the former, Fe‐catalyzed spiro‐bicyclization involves radical addition, 6‐exo‐dig cyclization, H‐abstraction and 5‐endo‐trig cyclization sequences under mild conditions, resulting in new spiro‐fused cyclopenta[ c ]chromen‐2‐ones via dual α , α ‐C(sp 3 )‐H abstractions. The latter enables in‐situ sulfonylation and desulfonylation of oxygen‐tethered 1,7‐enynes to realize the construction of multiple C‐C bonds, thereby leading to the formation of naphtho[2,3‐ c ]chromen‐6‐ones.