Solvent-free N-iodosuccinimide-promoted synthesis of spiroimidazolines from alkenes and amidines under ball-milling conditions

A novel N-iodosuccinimide-promoted intermolecular cyclization between alkenes and amidines has been demonstrated under solvent-free ball-milling conditions, affording a variety of spiroimidazolines with remarkable functional group tolerance and good to excellent yields. The present protocol features short reaction time, mild reaction conditions, high atom economy and feasibility of large-scale synthesis, providing an efficient and environmentally friendly access to spiroimidazolines.