Direct C–H bond functionalization has emerged as one of the most powerful and practical strategies for the modification of drug molecules. We have recently disclosed a Cu/NFAS (NFAS = N-fluoroalkyl sufonamide) catalytic system that exhibits high site-, regio-, and enantioselectivity for the direct cyanation of allylic C–H bonds. Here, we present a mechanistic investigation of this catalyst system, including the elucidation of side reactions involved in the transformation. This work focuses on an in-depth analysis of the catalytic cycle based on kinetic studies by NMR spectroscopy and characterization of the catalyst speciation by EPR and UV–vis spectroscopy. These studies indicate that a fraction of NFAS is sacrificed to the side reactions of the Cu(II)-bounded N-centered radical (Cu(II)–NCR) species for the generation of silylated sulfonamides and (CN)₂. The data also show a great dependence of the reaction yield and selectivity (hydrogen atom abstraction or HAA over side reactions) on the structure of the Cu(II)–NCR species. Kinetic studies and DFT calculations further reveal that oxidation of the CuCN species by NFAS, HAA process, and cyanation of Cu(II)–NCRs with TMSCN have comparable energy barriers, which collectively determine the rate of the overall C–H cyanation reaction. This result is published in JACS. Congratulations Jiayuan Li.

Methods for direct enantioselective oxidation of C(sp3)–H bonds will revolutionize the preparation of chiral alcohols and their derivatives. We present a copper-based biomimetic catalytic system that achieves highly efficient asymmetric sp3 C–H oxidation with C–H substrates as the limiting reagent. A Cu(II)-bound tert-butoxy radical is responsible for the site-selective C–H bond cleavage,  which resembles the active site of copper-based enzymes for C–H oxidation. The developed method has been successfully accomplished with good  functional group compatibility and exceptionally high site- and enantioselectivity, which is applicable for the late-stage oxidation of  bioactive compounds. This result is published in Nat. Catal. Congratulations Honggang Zhang.