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连续可见光光致活和钯催化促进对映选择性[4+2]环加成反应。

Sequential Visible-Light Photoactivation and Palladium Catalysis Enabling Enantioselective [4+2] Cycloadditions.

机构信息

Hubei International Scientific and Technological Cooperation Base of Pesticide and Green Synthesis, Key Laboratory of Pesticide & Chemical Biology, Ministry of Education, College of Chemistry, Central China Normal University , 152 Luoyu Road, Wuhan, Hubei 430079, People's Republic of China.

State Key Laboratory for Oxo Synthesis and Selective Oxidation, Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences , Lanzhou 730000, People's Republic of China.

出版信息

J Am Chem Soc. 2017 Oct 18;139(41):14707-14713. doi: 10.1021/jacs.7b08310. Epub 2017 Oct 10.

Abstract

Catalytic asymmetric cycloadditions of reactive ketene intermediates provide new opportunities for the production of chiral heterocyclic molecules. Though known for over 100 years, ketenes still remain underexplored in the field of transition-metal (TM)-catalyzed asymmetric cycloadditions because (1) ketenes, as highly electron-deficient species, are possibly unstable to low-valence TMs (i.e., decarbonylation or aggregation) and (2) the conventional thermal synthesis of ketenes from acyl chlorides and amines may be incompatible with TM catalysis (i.e., reactive acyl chloride and amine hydrochloride byproducts). Herein, we detail the unprecedented asymmetric [4+2] cycloaddition of vinyl benzoxazinanones with a variety of ketene intermediates via sequential visible-light photoactivation and palladium catalysis. It is well demonstrated that the traceless and transient generation of ketenes from α-diazoketones through visible-light-induced Wolff rearrangement is important for the success of present cycloaddition. Furthermore, chiral palladium catalysts with a new, chiral hybrid P, S ligand enable asymmetric cycloaddition with high reaction selectivity and enantiocontrol.

摘要

反应性烯酮中间体的催化不对称环加成为手性杂环分子的生产提供了新的机会。尽管烯酮已经存在了 100 多年,但由于 (1) 烯酮作为高度缺电子的物种,可能对低价过渡金属(即脱羰或聚集)不稳定,以及 (2) 酰氯和胺的传统热合成可能与 TM 催化不兼容(即反应性酰氯和胺盐酸盐副产物),因此,在过渡金属(TM)催化的不对称环加成中,烯酮仍然未得到充分探索。在此,我们详细描述了通过连续可见光光活化和钯催化,乙烯苯并恶嗪酮与各种烯酮中间体的前所未有的不对称 [4+2] 环加成。很好地证明了通过可见光诱导的 Woff 重排从α-重氮酮中痕量且瞬态生成烯酮对于本环加成的成功是重要的。此外,具有新型手性杂化 P,S 配体的手性钯催化剂能够实现具有高反应选择性和对映体控制的不对称环加成。

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