Mn(III)-based oxidative free-radical cyclizations of alkenyl Meldrumʹs acids

Oxidative cyclization of unsaturated Meldrumʹs acids can be carried out at temperatures as low as −30°C. The rate-determining step is cyclization of the enolate to the alkene ( to and ) rather than enolization, which is the rate-determining step with dimethyl 4-pentenylmalonate (). While cyclization of gives mainly cyclopentanes, cyclization of Meldrumʹs acids provides a versatile route to cyclohexenes.