Cross Coupling of Aryl Halides and Grignard Reagents

The Kumada cross coupling reaction is a highly atom economical coupling of Grignards with aryl or unsaturated halides catalysed by palladium and other metals.  A recent report from the group of Knochel (Malolkakes G et al, Ang Chem Int Ed, 2009, 48, 205-9) shows that with functionalised Grignards coupling can occur with aryl bromides and that this reaction proceeds via radical intermediates.  The Grignards must be made via exchange reactions (using iPr MgCl·LiCl) and not direct magnesiation for this reaction to work well.  It is suggested the process proceeds via radical intermediates.

PEPPSI is 1,3 bis [(2,6-diisopropylphenyl) imidazol-2-ylidine]-(3-chloro pyridyl) palladium (II) chloride