Breaking the Base Barrier: An Electron-Deficient Palladium Catalyst Enables the Use of a Common, Soluble Base in C–N Coupling
Due to the low intrinsic acidity of amines, palladium-catalyzed C–N cross-coupling has been plagued continuously by the necessity to employ strong, inorganic, and/or insoluble bases. To surmount the many practical obstacles associated with these reagents, we utilized a commercially available, dialkyl triarylmonophosphine-supported palladium catalyst that facilitates a broad range of C–N coupling reactions in the presence of weak, soluble bases. The mild and general reaction conditions show extraordinary tolerance for even highly base-sensitive functional groups. Additionally, insightful het-eronuclear NMR studies using 15N-labeled amine complexes provide evidence for the key acidifying effect of the cationic palladium center.Due to the low intrinsic acidity of amines, palladium-catalyzed C–N cross-coupling has been plagued continuously by the necessity to employ strong, inorganic, and/or insoluble bases. To surmount the many practical obstacles associated with these reagents, we utilized a commercially available, dialkyl triarylmonophosphine-supported palladium catalyst that facilitates a broad range of C–N coupling reactions in the presence of weak, soluble bases. The mild and general reaction conditions show extraordinary tolerance for even highly base-sensitive functional groups. Additionally, insightful het-eronuclear NMR studies using 15N-labeled amine complexes provide evidence for the key acidifying effect of the cationic palladium center.