Catalytic atom-transfer radical cyclization by copper/bipyridine species encapsulated in polysiloxane gel

Abstract

Novel polysiloxane gel, in which CuCl/bipyridine species are immobilized, is prepared by treatment of polymethylhydrosiloxane with 4,4′-bis[(2-propenyl)oxy]-2,2′-bipyridine and 1,5-hexadine in the presence of Karstedt′s catalyst followed by addition of CuCl. This polysiloxane gel acts as a reusable catalyst in the atom-transfer radical cyclization of α-halogenated acetamide derivatives in high turnover numbers without allowing leakage of the metal species.