Site-Selective Copper-Catalyzed Azidation of Benzylic C–H Bonds

Suh, S.-E.; Chen, S.-J.; Mandal, M.; Guzei, I. A.; Cramer, C. J.; Stahl, S. S.
J. Am. Chem. Soc. 2020, 142, 11388 (doi:10.1021/jacs.0c05362).

Site selectivity represents a key challenge for non-directed C–H functionalization, even when the C–H bond is intrinsically reactive. Here, we report a copper-catalyzed method for benzylic C–H azidation of diverse molecules. Experimental and density functional theory studies suggest the benzyl radical reacts with a Cu^II-azide species via a radical-polar crossover pathway. Comparison of this method with other C–H azidation methods highlights the unique site-selectivity of this method, and conversions of the benzyl azide products into amine, triazole, tetrazole, and pyrrole functional groups highlight the broad utility of this method for target molecule synthesis and medicinal chemistry.