Hydrogen‐Atom‐Transfer‐Initiated Radical/Polar Crossover Annulation Cascade for Expedient Access to Complex Tetralins

A radical/polar crossover annulation between allyl-substituted arenes and electron-deficient alkenes is described. Cobalt-catalyzed hydrogen atom transfer (HAT) facilitates tandem radical C−C bond formation that generates functionalized tetralin products in the face of potentially problematic hydrofluorination, hydroalkoxylation, hydrogenation, alkene isomerization, polymerization reactions. The reactions proceed under mild conditions tolerate many functional groups, leading to a broad substrate scope. This powerful ring-forming reaction very quickly assembles complex tetralins are formal largely infeasible Diels–Alder cycloadditions styrenes.