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(sp³)-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.