Metalloradical Activation of In Situ-Generated α-Alkynyldiazomethanes for Asymmetric Radical Cyclopropanation of Alkenes.
Metalloradical Activation of In Situ-Generated α-Alkynyldiazomethanes for Asymmetric Radical Cyclopropanation of Alkenes.
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DOI：
10.1021/jacs.1c13154
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发表时间：
2022-02-09
影响因子：
15
通讯作者：
Zhang, X. Peter
中科院分区：
文献类型：
--
作者：
Ke, Jing;Lee, Wan-Chen Cindy;Wang, Xiaoxu;Wang, Yong;Wen, Xin;Zhang, X. Peter
在Co（II）基金属自由基催化剂（MRC）催化烯烃不对称环丙烷化反应中，由磺酰腙在碱存在下原位生成的α-炔基重氮甲烷可作为有效的亲金属自由基试剂。以D2-对称手性氨基卟啉2，6-DiMeO-QingPhyrin为最佳支持配体，Co（II）基金属自由基体系在室温下可有效活化不同的α-炔基重氮甲烷，进行多种烯烃的高度不对称环丙烷化反应.该催化自由基方法提供了一种通用的合成工具，立体选择性建设炔基环丙烷在高产率与高的非对映选择性和对映选择性。结合计算和实验研究提供了几条支持Co（II）催化的烯烃环丙烷化反应的分步自由基机理的证据，该反应涉及一个独特的α-金属自由基中间体，该中间体与α-Co（III）-炔丙基自由基和γ-Co（III）-联烯基自由基的两种共振形式相关。所得到的对映体富集的炔基环丙烷，如展示与几个立体特异性的转换，可以作为有价值的手性积木立体选择性的有机合成。
α-Alkynyldiazomethanes, generated in situ from the corresponding sulfonyl hydrazones in the presence of a base, can serve as effective metalloradicophiles in Co(II)-based metalloradical catalysis (MRC) for asymmetric cyclopropanation of alkenes. With D2-symmetric chiral amidoporphyrin 2,6-DiMeO-QingPhyrin as the optimal supporting ligand, the Co(II)-based metalloradical system can efficiently activate different α-alkynyldiazomethanes at room temperature for highly asymmetric cyclopropanation of a broad range of alkenes. This catalytic radical process provides a general synthetic tool for stereoselective construction of alkynyl cyclopropanes in high yields with high both diastereoselectivity and enantioselectivity. Combined computational and experimental studies offer several lines of evidence in support of the underlying stepwise radical mechanism for the Co(II)-catalyzed olefin cyclopropanation involving a unique α-metalloradical intermediate that is associated with two resonance forms of α-Co(III)-propargyl radical and γ-Co(III)-allenyl radical. The resulting enantioenriched alkynyl cyclopropanes, as showcased with several stereospecific transformations, may serve as valuable chiral building blocks for stereoselective organic synthesis.
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影响因子：
15
作者：
Das, Sandip Kumar;Roy, Satyajit;Chattopadhyay, Buddhadeb
通讯作者：
Chattopadhyay, Buddhadeb
影响因子：
15
作者：
Chan, Yun Wai;Chan, Kin Shing
通讯作者：
Chan, Kin Shing
影响因子：
4.5
作者：
Chirila A;Gopal Das B;Paul ND;de Bruin B
通讯作者：
de Bruin B
影响因子：
1.8
作者：
Davies, HML;Boebel, TA
通讯作者：
Boebel, TA
通过 Cu(i)/CPA 协同催化对烷基自由基进行催化对映选择性去对称官能化
影响因子：
37.8
作者：
Cheng, Yong-Feng;Liu, Ji-Ren;Liu, Xin-Yuan
通讯作者：
Liu, Xin-Yuan