Hiyama Reactions of Activated and Unactivated Secondary Alkyl Halides Catalyzed by a Nickel/Norephedrine Complex

摘要

We recently reported that a nickel/bathophenanthroline-based catalyst accomplishes Hiyama couplings of unactivated secondary alkyl electrophiles for the first time [Eq. (1), DMSO=dimethyl sulfoxide]. Although this represented a step forward in the expansion of the scope of metal-catalyzed cross-coupling reactions, it was not an ideal solution from at least three standpoints: First, the yields of the Hiyama reactions were moderate (60-82 %); second, the method was not generally effective for activated secondary alkyl halides; and third, only bipyridine-type ligands that lack a substituent ortho to the nitrogen atom furnished useful catalysts (that is, bathophenanthroline, 1,10-phenanthroline, and 2,2'-bipyridine, but not neocuproine).