Direct access to polycyclic imidazolium salts decarboxylative condensation of α-enaminones with proline

A new strategy for direct access to fully substituted polycyclic imidazolium salts, based on the interaction of α-enaminones with proline in the presence of variety of counter-ions, is reported. The developed open-flask operation is catalyst-, metal-, and Lewis acid-free green process, which requires no ion-exchange step, not limited to aryl substituents, and generally results in good yields and minimal formation of side products. A new catalyst-, metal-, and Lewis acid-free strategy for direct access to fully substituted polycyclic imidazolium salts, based on the interaction of α-enaminones with proline in the presence of a variety of counter-ions, is reported.