Sterically and Electronically Controlled C–H Functionalization
Arenes and heteroarenes are key substructures in pharmaceuticals yet certain substitution patterns are underrepresented due to lack of reliable synthetic methods. Selective C–H functionalization of substituted benzenes and pyridines is an attractive and potentially direct method to expand molecular space. Our laboratory has developed classes of pincer-ligated cobalt(I) catalysts that promote the selective C(sp2)–H borylation of various substituted arenes and pyridines. Depending on the electronic properties and rigity of the pincer, the C(sp2)–H oxidative addition and hence site of functionalization is either under kinetic or thermodynamic control. For fluorinated arenes, the thermodynamic site is ortho while the kinetic is meta. Examples of switchable selectivity have also been discovered where the rate of arene functionalization versus isomerization determines the reaction outcome. In more recent work, highly active cobalt catalysts have been discovered that enable the site selective C–H borylation of common arenes that have indistinguishable C(sp2)–H bond strengths. Emphasis will be devoted to reaction mechanism and applications in synthesis.
~Coffee/tea will be served prior to the lecture~
Hosted by Professor Kate Waldie