Ar ange of cyclopropyl-fused N-tosyl piperidines have been synthesised ands hown to undergo ring-opening isomerisation on treatment with platinum(II) catalysts. The products can have either an endo-cyclic or exo-cyclic double bond. The selectivity is influenced by reaction temperature, solventa nd, most significantly,t he catalyst. Am echanism in-volvingC ÀCb ond activation and b-hydride eliminationi s proposed. When b-hydride elimination is blocked, as tereospecific platinum-driven Wagner-Meerwein shift is observed.