... Tetrahedron Letters. ... a Cat.: I 2 0.1 mmol; co-solvent: EtOH 1.0 mL (2.0 vol.%). ... 1). In the case of the reaction of 2a, increasing the mole fraction of CO 2 by increasing density of CO 2 under constant volume can contribute to a shift in the equilibrium (Path A in Scheme 2) in favor of ...