Cocatalytic Activity of the Furfuryl and Oxanorbornane-Substituted Guanidines in the Aldol Reaction Catalyzed by ()-Proline.

This work investigated the cocatalytic activity of recently prepared guanidinium salts containing an oxanorbornane subunit in an ()-proline-catalyzed aldol reaction. The activity was interpreted by the diastereoselectivity of the reaction (/ ratio) and for the most interesting polycyclic guanidinium salt, the enantioselectivity of the reaction was determined. The results indicated a negative impact on the oxanorbornane unit if present as the flexible substituent.