Li Xiaofang, Yuan Mingbin, Chen Fan, Huang Zhonghou, Qing Feng-Ling, Gutierrez Osvaldo, Chu Lingling
State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, College of Chemistry, Chemical Engineering and Biotechnology, Center for Advanced Low-Dimension Materials, Donghua University, Shanghai 201620, China.
Department of Chemistry and Biochemistry, University of Maryland, College Park, MD 20742, USA.
Chem. 2023 Jan 12;9(1):154-169. doi: 10.1016/j.chempr.2022.09.020. Epub 2022 Oct 14.
The development of efficient catalytic multicomponent reactions (MCRs) is highly sought-after in chemical synthesis. However, catalytic asymmetric MCRs, particularly involving radical species, remain largely underdeveloped due to the exceptionally high reactivity of open-shell radical species. Herein, we report a metallaphotoredox-catalyzed asymmetric three-component method to access a diverse array of enantio-enriched α-alkenyl phosphonates from readily available vinyl phosphonates, alkenyl halides, and alkyl trifluoroborates under mild conditions. This operationally simple and redox-neutral protocol exhibits broad substrate scope and excellent chemo-, regio-, stereo-, and enantioselectivity. Furthermore, by simple modification of the triplet energy of the photocatalyst employed, both enantio-enriched and α-alkenyl phosphonates can be divergently accessed. Detailed computational and experimental studies were undertaken to elucidate the mechanism and origin of the observed reactivity and selectivity, which support a radical cascade sequence with α-phosphonate controlling the trajectory of radical capture by a chiral tetrahedral alkenyl nickel(II) species in the enantioselectivity-determining step.
高效催化多组分反应（MCRs）的开发在化学合成中备受关注。然而，催化不对称MCRs，特别是涉及自由基物种的反应，由于开壳层自由基物种的反应活性极高，在很大程度上仍未得到充分发展。在此，我们报道了一种金属光氧化还原催化的不对称三组分方法，该方法能在温和条件下，从易得的乙烯基膦酸酯、卤代烯烃和烷基三氟硼酸盐出发，制备出多种对映体富集的α-烯基膦酸酯。这种操作简单且氧化还原中性的方法具有广泛的底物范围以及出色的化学、区域、立体和对映选择性。此外，通过简单改变所用光催化剂的三线态能量，可以不同地获得对映体富集的α-烯基膦酸酯。我们进行了详细的计算和实验研究，以阐明所观察到的反应性和选择性的机理及来源，这支持了一种自由基级联序列，即在对映选择性决定步骤中，α-膦酸酯控制手性四面体烯基镍（II）物种捕获自由基的轨迹。
