Milanpreet Kaur and Jeffrey Van Humbeck* Department of Chemistry, University of Calgary, Alberta, Canada Research in the field of C-H functionalization has modified the way chemists approach the synthesis of natural products and medicinally relevant synthetic molecules. However, there has been a noticeable challenge in 1) Carrying competitive C-H functionalization when several sites of comparable reactivity are present. 2) Accessing many possible reactive sites within such a substrate. Our research group is working on addressing these challenges by developing a novel C-H amination strategy for heterocyclic substrate using a dual catalytic system - consisting of transition metal Lewis acid and an organic hydrogen atom transfer (HAT) catalyst. This dual catalytic system possesses the ability to convert C-H bond to C-O and C-N bonds, where the site of the reaction is para to the site of the binding of a metal catalyst. Previous studies have demonstrated that this strategy has a very high selectivity for aromatic N-heterocyclic substrates when they are compared against all-carbon aromatics. Our current work is working towards a more challenging problem: Can we develop a catalytic system that 1) can synthesize complex substrates under mild conditions; 2) can selectively activate one heterocycle in the presence of a second heterocycle. Ideally, we aim to create complementary catalysts systems that allow for selective functionalization of either heterocycle in the pair. Our preliminary results reveal that our new catalytic system 1) offers a lot of advantages over previously used aminating reagent; 2) can lead to activation of C-H bonds in different heterocyclic substrates and is impacted by the specific catalyst combination (copper source, ligand and HAT), and that in the case of particular heterocycle pairs (e.g. heterocycles with vs. without metal chelating groups) selectivity for either component of the pair can be achieved.

New radical strategy for site selective C-H functionalization in azaheterocycles

ACS Fall 2021

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