Conjugated diene-assisted allylic C-H bond activation: cationic Rh(I)-catalyzed syntheses of polysubstituted tetrahydropyrroles, tetrahydrofurans, and cyclopentanes from ene-2-dienes

An unprecedented diene-assisted transition-metal-catalyzed activation of allylic C-H bonds and their subsequent insertion into the alkene moieties of conjugated dienes is described. The C-H activation/alkene insertion has provided an efficient way to prepare polysubstituted tetrahydropyrroles, tetrahydrofurans and cyclopentanes with quaternary carbon centers and the studies have shown that allylic C-H activation and alkene insertion are reversible steps, whereas the reductive elimination step is irreversible.