NHC / Cobalt Complex Catalyzed ortho-Functionalization of Pivalophenone Imines and following Cyanation

Yoshikai et al. have reported the ortho-selective functionalization of pivalophenone imines(1) and the subsequent chemical conversion of the imino group to a cyano group. According to their result, in the presence of a Grignard reagent, the NHC-cobalt complex (2), prepared from the precursor of NHC of 1,3-diisopropylimidazolinium tetrafluoroborate and cobalt(II) bromide, acts as a catalyst for the reaction of 1 with alkyl bromides, and the related ortho-alkylated products are given in good yield. This reaction can be applied for the ortho-selective arylation of 1 by selecting the appropriate NHC precursor and using aryl chlorides. In addition, the imino moiety of the given ortho-functionalized pivalophenone derivatives is chemically transformed into the cyano group by the treatment with di-tert-butyl peroxide or copper(II) diacetate/oxygen through the radical or oxidative pathway, which synthetic approach gives the ortho-functionalized benzonitriles.