The direct catalytic functionalization of C-H bonds, an ubiquitous motif in organic molecules, represents a paradigm shift in the standard logic of organic synthesis. One of the major challenges to render this approach synthetically useful is to control the site-selectivity because most organic molecules exhibit several similar aliphatic C-H bonds.
The functionalization of aliphatic C-H bond mediated by photoredox catalysis is a highly active field of research. To date, state-of-the-art site-selective methods in this field rely on substrate control which are inherently restricted to the functionalization of a single C-H bond within the substrate backbone. The innovative aspect of this research program is to target catalyst control to allow the site-selective functionalization of several different C-H bonds of a single substrate. Through this approach, we wish to go beyond the challenging problem of site-selectivity to enable site-divergent functionalizations. Such a breakthrough would provide a new tool for a flexible and streamlined access to molecular complexity from chemical feedstocks.
To achieve our objectives, we plan to develop novel bifunctional catalysts incorporating one moiety able to engage into dynamic non-covalent interactions with the substrate and another functional group able to perform Hydrogen Atom Transfer (HAT) processes. These two functional groups are connected by an inert spacer which will position the HAT unit in proximity to a particular C-H bond of the substrate, thus controlling site-selectivity for the C-H activation event. By varying the nature of the spacer, we expect to selectively functionalize several different positions of linear alkyl chains possessing almost undistinguishable methylene C-H bonds.
Overall, BICACH aims at using simple bifunctional organocatalysts and light energy to trigger highly challenging C-H functionalization processes. In addition, it offers a unique training to the ER with broad future research perspectives.
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