N-Heterocyclic Carbenes: Organocatalysts with Moderate Nucleophilicity but Extraordinarily High Lewis Basicity
Angew. Chem. 2011, 123, 7047-7052, 2011, 123, 7047-7052 published on 28.06.2011
Angew. Chem. Int. Ed.
Unique organocatalysts: Arduengo's carbenes 1 and 2 are 103 times more nucleophilic than the Enders carbene 3, which attacks electrophiles with similar rates as diazabicyclo[5.4.0]undecene (DBU) and 4-(dimethylamino)pyridine (DMAP). The unique organocatalytic activities of 1–3 are explained by their extraordinarily high Lewis basicities, which exceed those of PPh3, DBU, and DMAP by more than 100 kJ mol−1.