Simplifying Nickel(0) Catalysis: An Air-stable COD-free Nickel Precatalyst for the Internally-selective Benzylation of Terminal Alkenes

摘要

The synthesis and characterization of the air-stable nickel(II) complex trans-(PCy2Ph)2Ni(o-tolyl)Cl is described in conjunction with an investigation of its use for Mizoroki Heck-type, room temperature, internally-selective coupling of substituted benzyl chlorides with terminal alkenes. This reaction, which employs a terminal alkene as an alkenylmetal equivalent, provides rapid, convergent access to substituted allylbenzene derivatives in high yield and with regioselectivity greater than 95:5 in nearly all cases. The reaction is operationally simple, can be carried out on the bench-top with no purification or degassing of solvents or reagents, and requires no exclusion of air or water during setup. Synthesis of the precatalyst is accomplished through a straightforward procedure that employs inexpensive, commercially available reagents, requires no purification steps, and proceeds in high yield.