Aryl halides, cross coupling with alkylmetals

Alkyl halides other than aryl and vinyl halides do not readily undergo oxidative addition with Pd and must, in general, first be converted to alkylmetals. In this connection, however, a recent report on the Ni catalysed selective alkyl-alkyl cross-coupling with Ni(acac)2 and Lil in THF represents a significant breakthrough.34 In cases where the alkyl group contains a p-H atom, reduction of the organic halide via p-dehydropalladation reductive elimination can be a serious side-reaction (Scheme 11.6). 

Until recently, cross-coupling between alkylmetals and aryl, alkenyl, and alkynyl halides was achieved mostly with alkylcoppers. Over the past two decades, however, the Ni- or Pd-catalyzed reaction of alkylmetals with the unsaturated organic hahdes mentioned above has been developed as a viable alternative, as detailed in Sect. ni.2.II. The Cu-based methodology still remains highly competitive. So, it is advisable to consider both options for finding the method for a given case. 

A. Nickel Catalysis in the Cross Coupling of Aryl Halides with Alkylmetals. The Role of Arylalkylmckel(II) Species as Intermediated For the study of nickel catalysis in the formation of aralkanes, we employed the system consisting of aryl bromides and methyllithium or methylmagnesiiun bromide. 

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