Transition metal catalyzed cross-coupling reactions are one of the most important tools available to synthetic chemists for the construction of substituted aromatics. An atom and step economical approach is to make direct use of C-H bonds as latent functional groups. These can be activated through chelation assisted transition metal insertion to form cyclometallated intermediates and then functionalized catalytically.Achieving site selectivity in aromatic C-H functionalization reactions still remains a major challenge. A common approach is to utilise cyclometallated intermediates to facilitate the formation of ortho-substituted products via oxidative addition of new coupling partners. Examples of direct meta C-H functionalization however are considerably fewer. One approach to access these products is to exploit similar cyclometallated intermediates to activate remote C-H bonds for SEAr type reactivity. Figure 1. <img src='https://acs-archive-assets2.s3.amazonaws.com/241nm/uploads/72523_glutaminationabstractimage.jpg' alt='' />Following our successful meta-selective C-H bond sulfonation of 2-phenylpyridine, our efforts have been focused on expanding the scope of this interesting reactivity. Through an in-depth mechanistic study exploring the nature of the organometallic species involved, we are beginning to identify the key components that favour meta selective SEAr type reactivity over ortho-selective oxidative addition pathways. This work is informing us for our development of new meta-selective C-H functionalization reactions and our goal of generating new selective catalysts.

Controlling site selectivity in C-H functionalization reactions

248th National Meeting (2014)

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