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  • Copper‐Catalyzed Enantiocon...
    Su, Xiao‐Long; Ye, Liu; Chen, Ji‐Jun; Liu, Xiao‐Dong; Jiang, Sheng‐Peng; Wang, Fu‐Li; Liu, Lin; Yang, Chang‐Jiang; Chang, Xiao‐Yong; Li, Zhong‐Liang; Gu, Qiang‐Shuai; Liu, Xin‐Yuan

    Angewandte Chemie, January 4, 2021, Volume: 133, Issue: 1
    Journal Article

    The development of enantioconvergent cross‐coupling of racemic alkyl halides directly with heteroarene C(sp2)−H bonds has been impeded by the use of a base at elevated temperature that leads to racemization. We herein report a copper(I)/cinchona‐alkaloid‐derived N,N,P‐ligand catalytic system that enables oxidative addition with racemic alkyl bromides under mild conditions. Thus, coupling with azole C(sp2)−H bonds has been achieved in high enantioselectivity, affording a number of potentially useful α‐chiral alkylated azoles, such as 1,3,4‐oxadiazoles, oxazoles, and benzodoxazoles as well as 1,3,4‐triazoles, for drug discovery. Mechanistic experiments indicated facile deprotonation of an azole C(sp2)−H bond and the involvement of alkyl radical species under the reaction conditions. The use of a cinchona‐alkaloid‐derived N,N,P‐ligand leads to the direct enantioconvergent coupling of racemic alkyl bromides with azole C(sp2)−H bonds by copper catalysis. The key to success is the ligand‐enabled facile oxidative addition at approximately room temperature that suppresses product racemization at elevated temperature. This method provides a range of enantioenriched α‐chiral alkylated azoles.