Synthesis of Methylene γ-lactones Using Carbon Dioxide

Abstract

Many industrial processes generate the greenhouse gas, carbon dioxide, as a byproduct. Carbon dioxide can be captured and recycled by using it in organic synthesis to prepare beneficial compounds. The goal of this project is to develop a new method of synthesizing methylene γ-lactones using CO2-metal complexes. Many gamma lactones are biologically active, and their synthesis is of importance to pharmaceutical and other industries. Allenes can react with a transition metal-CO2 complex. It is proposed that a titanium metal complex prepared with an aldehyde will bind to an allene, and a seven-membered ring forms as CO2 is inserted at the titanium-carbon bond. Subsequent intramolecular rearrangement affords a methylene γ-lactone when the oxygen atom associated with the organic substrate acts as a nucleophile and cleaves the titanium-oxygen bond. Recapturing carbon dioxide emission and using it in organic synthesis is a potential method for reducing the release of a harmful greenhouse gas into the environment, and a way to recycle carbon that would be wasted otherwise