Stereoselective Radical Cascade Cyclizations of Unsaturated Epoxynitriles: Quadruple Radical Cyclization Terminated by a 4-exo Process onto Nitrile

Abstract

[EN]Radical cascade cyclizations of unsaturated epoxy­nitriles induced by titanocene chloride proceed in good yields and with excellent diastereoselectivities. From three to seven stereocenters were created by the reaction and a single isomeric product was obtained from most of the substrates examined. The relative configuration of the products is consistent with cyclization occurring via a chair-like transition state. The termination of the radical cascade reaction by 4-exo, 5-exo or 6-exo cyclization onto nitrile is remarkable.