Stereoselective Radical Cyclization Cascades Triggered by Addition of Diverse Radicals to Alkynes To Construct 6(5)–6–5 Fused Rings

Cascade radical cyclization of alkynyl
ketones with various carbon-
and heteroatom-centered radical precursors via a sequential radical
addition/1,5-H radical shift/5-exo-trig/radical cyclization
process was realized for the first time. This method provides a strategically
novel and step-economical protocol for diversity-oriented synthesis
of a wide range of carbocyclic and heterocyclic 6(5)–6–5
fused ring systems with three contiguous stereocenters, including
a quaternary carbon in high yields with excellent chemo- and diastereoselectivity.