Synthesis of 1,5-Diamino-Substituted 1,3-Dienes via Rhodium(II)-Catalyzed Tandem Reactions of 1-Cyclopropylethylarenes

Herein, (<i>E</i>,<i>E</i>)-1,5-diamino-1,3-dienes are stereoselectively synthesized from substituted aryl derivatives via a rhodium(II)-catalyzed C(sp³)-H functionalization involving a cascade of cyclopropane ring expansion, cyclobutene formation, cyclobutene to 1,3-diene conversion, and regioselective diamination. Mechanistic studies show this one-pot process proceeds through hydrogen atom transfer (HAT), radical-polar crossover (RPC), elimination, electrocyclic ring-opening, and radical addition, underscoring rhodium(II)'s role in radical-mediated catalysis beyond traditional rhodium(II) nitrenoid chemistry.