Unprecedented formal ‘2+2’ addition of allene to CO2 promoted by [RhCl(C2H4)(PiPr3)]2: direct synthesis of the four membered lactone α-methylene-β-oxiethanone. The intermediacy of [RhH2Cl(PiPr3)]2: theoretical aspects and experiments

In this paper the reaction of allene with carbon dioxide is discussed, using [RhCl(C2H4)(PiPr3)]2 as catalyst. An unprecedented formal ‘2+2’ allene–CO2 reaction to afford a four-membered lactone is described. The influence of the temperature and pressure on the reaction of allene and CO2 is highlighted. The role of addition of hydrogen to the reaction system, as modulator of the products distribution is discussed. The behavior of the catalyst [RhCl(C2H4)(PiPr3)]2 towards H2 is also described and the structure of the resulting Rhhydride species inferred through a theoretical study.