HFIP promoted carbo-lactonisation as a new route to functionalised lactones

Abstract

We have been able to induce a series of lactonisation reactions of unsaturated acids using a carbocationic intermediate formed in situ. The transformation generates five and six membered lactone rings AND forms a new exocyclic C–C bond at the same time, thus removing the need for further derivatisation of typical lactonisation products (such as from iodo lactonisation). The reaction is operationally straightforward, does not employ any metals and utilises readily accessible alcohol and unsaturated acid substrates.