Effect of Tether Length on Ti(III)-Mediated Cyclization of Epoxyalkenes and Unsaturated Epoxyketones

Abstract

The chemo- and regioselectivity of the radical cyclization induced by titanocene chloride of a series of epoxyalkenes and another of unsaturated epoxyketones are investigated. 5-Exo and 6-exo cyclizations are the main processes with epoxyalkenes. 3-Exo and 4-exo cyclizations onto the carbonyl group and 6-exo and 8-endo onto the carbon-carbon double bond are the preferred processes with epoxyenones. A tandem reaction, 6-exo onto C=C, followed by a 3-exo onto C=O, and a disfavored 5-endo cyclization onto C=C are reported.