A Comparative Reactivity Survey of Some Prominent Bisphosphine Nickel(II) Precatalysts in C–N Cross-Coupling

The synthesis and
characterization of the new air-stable precatalyst
(L1)­Ni­(o-tol)Cl (C1; where L1 = JosiPhos CyPF-Cy) is reported, along with the results
of a comparative reactivity survey involving C1 and analogous
PAd-DalPhos- and DPPF-containing precatalysts (C2 and C3, respectively) in representative nickel-catalyzed C­(sp2)–N cross-coupling reactions. Precatalyst C1 was found to be competitive with, and in some cases complementary
to, C2 in the monoarylation of ammonia and primary alkylamines
with (hetero)­aryl chlorides, including in otherwise challenging room
temperature transformations. (Pseudo)­halide comparison studies involving
the cross-coupling of furfurylamine at room temperature revealed that
in contrast to C2 precatalyst C1 performs
less effectively with aryl bromides. Whereas C3 was found
to be ineffective for such transformations, this DPPF-derived precatalyst
proved superior to C1 and C2 in reactions
involving the secondary dialkylamine test substrate morpholine.