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Comparative Screening of DalPhos/Ni Catalysts in C‐N Cross‐couplings of (Hetero)aryl Chlorides Enables Development of Aminopyrazole Cross‐couplings with Amine Base

Several focused reports have appeared over the past few years documenting the utility of nickel catalysts featuring newly developed DalPhos bisphosphine ligands for C-N cross-couplings of typically challenging (hetero)aryl chlorides with targeted NH nucleophiles. Herein, a more expansive and systematic competitive evaluation of this ligand family in N-arylation chemistry is provided involving primary (linear and branched) and secondary alkylamines, as well as a primary five-membered heteroarylamine (aminopyrazole), in combination with a diverse set of test electrophiles and bases (NaOtBu, K2CO3, DBU/NaTFA). In addition to providing optimal ligand/catalyst identification, and bringing to light methodology limitations (e.g., unwanted C-O cross-coupling with NaOtBu), our survey enabled the development of the first efficient catalyst system for heteroatom-dense C-N cross-coupling of aminopyrazoles and related nucleophiles with (hetero)aryl chlorides by use of an amine ‘dual-base’ system.

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