We established a copper-catalyzed asymmetric alkynylation of the sp2 C–H bond of silylallenes, which was presented as an efficient method for the synthesis of enantioenriched skipped diynes with excellent enantioselectivity. The reaction was initiated by hydrogen atom abstraction of sp2 allenic C–H bonds, in which the resonance forms of allenic and propargylic radicals were chemo- and enantioselectively trapped by chiral alkynyl-Cu(II) species to deliver a variety of skipped diynes. The method features a broad substrate scope and robust functional group tolerance, accommodating both alkynyl silanes and boronic esters. This result is published in JACS. Congratulations Ping Zhao.

We disclosed a copper-catalyzed approach for the enantioselective allylic C(sp3)–H oxidation of terminal alkenes, facilitated by introducing a sterically bulky B2Im(C6F5)6 anion. Notably, a wide range of aryl-substituted terminal alkenes were used as limiting reagents, delivering various products with excellent enantioselectivity and regioselectivity (up to 99% ee, >20:1 b/l). Mechanistically, the bulky counteranion was found to be essential for achieving excellent enantioselective control and high catalytic efficiency. This result is published in JACS. Congratulations Yibo.

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.