Directing aryl-I versus Aryl-Br bond activation by nickel via a ring walking process.
Activation of a strong aryl-Br bond of a halogenated vinylarene by nickel(0) is demonstrated in the presence of aryl-I containing substrates. eta2-Coordination of Ni(PEt3)2 to the C=C moiety of halogenated vinylarenes is kinetically preferable and is followed by an intramolecular aryl-halide bond activation process. This "ring-walking" process is quantitative and proceeds under mild reaction conditions in solution. Mechanistic studies indicate that the metal insertion into the aryl-halide bond is not the rate-determining step. The reaction obeys first-order kinetics in the eta2-coordination complexes with almost identical activation parameters for Br and I derivatives. The ring-walking process is kinetically accessible as shown by density functional theory (DFT) calculations at the PBE0/SDB-cc-pVDZ//PBE0/SDD level of theory.
Zenkina
Olena V
OV
Departments of Organic Chemistry and Chemical Research Support, The Weizmann Institute of Science, 76100 Rehovot, Israel.
Karton
Amir
A
Freeman
Dalia
D
Shimon
Linda J W
LJ
Martin
Jan M L
JM
van der Boom
Milko E
ME