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, 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 heteronuclear NMR studies
using 15N-labeled amine complexes provide evidence for
the key acidifying effect of the cationic palladium center.