Electro‐Mechanochemical Atom Transfer Radical Cyclizations using Piezoelectric BaTiO ₃

Abstract

The formation and regeneration of active Cu ^I species is a fundamental mechanistic step in copper‐catalyzed atom transfer radical cyclizations (ATRC). Typically, the presence of the catalytically active Cu ^I species in the reaction mixture is secured by using high Cu ^I catalyst loadings or the addition of complementary reducing agents. In this study it is demonstrated how the piezoelectric properties of barium titanate (BaTiO ₃) can be harnessed by mechanical ball milling to induce electrical polarization in the strained piezomaterial. This strategy enables the conversion of mechanical energy into electrical energy, leading to the reduction of a Cu ^II precatalyst into the active Cu ^I species in copper‐catalyzed mechanochemical solvent‐free ATRC reactions.

Abstract

Squeezing electrons by milling: Macroscopic mechanical forces transduced by ball milling are capable of inducing electrical polarization in piezoelectric BaTiO ₃. The electropotential of the strained piezoelectric material was harvested to trigger the reduction of a Cu ^II complex into an active Cu ^I catalyst for mechanochemical solvent‐free ATRC reactions.