A blue-light-promoted carbon-carbon double bondisomerization in the absence of any photoredox catalyst is reported. It provides rapid access to a series of quinolines in good to excellent yields under simple aerobic conditions. The protocol is direct, catalyst-free and operationally convenient.
A novel method for the regioselective C2-chlorination of heterocyclic N-oxides has been developed. PPh3/Cl3CCN were used as chlorinating reagents and the desired N-heterocyclic chlorides were obtained smoothly in satisfactory yields. The reactions proceeded in a highly efficient and selective manner across a broad range of substrates demonstrating excellent functional group tolerance. In addition,
A novel approach was developed for the dehydrogenative etherification homocoupling of heterocyclicN-oxides in the presence of silver oxide and PyBroP. Various substrates were well tolerated and the desired products were obtained in moderate to good yields. Generally, this reaction features excellent functional group compatibility, broad substrate scope and good regioselectivity.
Cobalt-Catalyzed Cross-Coupling Reactions of Heterocyclic Chlorides with Arylmagnesium Halides and of Polyfunctionalized Arylcopper Reagents with Aryl Bromides, Chlorides, Fluorides and Tosylates
A range of aromatic organocopper or organomagnesium compounds undergo smooth cross-coupling reactions with aryl bromides, chlorides, fluorides and tosylates, leading to polyfunctionalized aromatics or heterocycles in the presence of cobalt salts (5-7.5 mol%) as catalysts. Very mild reaction conditions are needed and, in the case of cross-coupling with organocopper compounds, Bu4NI (1 equiv) and 4-fluorostyrene (20 mol%) are essential as promoters for successful couplings.
Importance of Two-Electron Processes in Fe-Catalyzed Aryl-(hetero)aryl Cross-Couplings: Evidence of Fe<sup>0</sup>/Fe<sup>II</sup> Couple Implication
作者:Vincent Wowk、Lidie Rousseau、Guillaume Lefèvre
DOI:10.1021/acs.organomet.1c00338
日期:2021.10.11
We demonstrate in this work that two drastically distinct mechanisms can be involved in aryl-(hetero)aryl Fe-mediated cross-couplings between Grignard reagents and organic halides, depending on the nature of the latter. (Hetero)aryl electrophiles, which easily undergo one-electron reduction, can be involved in a FeII/FeIII coupling sequence featuring an in situ generated organoiron(II) species, akin
我们在这项工作中证明了两种截然不同的机制可能涉及格氏试剂和有机卤化物之间的芳基-(杂)芳基 Fe 介导的交叉偶联,具体取决于后者的性质。(杂)芳基亲电试剂很容易进行单电子还原,可以参与 Fe II / Fe III偶联序列,其特征是原位生成的有机铁 (II) 物质,类似于它们的脂肪族类似物。另一方面,不易被还原的底物可以被由预催化剂还原形成的瞬态 Fe 0物质激活。在这种情况下,耦合机制依赖于涉及 Fe 0 /Fe II 的双电子基本步骤氧化还原对并通过氧化加成/还原消除顺序进行。Hammett 分析表明,对于被吸电子基团取代的亲电试剂,这两个基本步骤都更快。对于显示平均氧化能力的亲电试剂,本文讨论的两种机制可以同时涉及。证明上述双电子机制的可行性,还首次表征了在催化相关条件下通过双电子氧化加成到(杂)芳基卤化物上形成的高自旋有机铁(II)中间体。这些结果得到了顺磁1 H NMR、动力学监测和密度泛函理论