Recent advances in electrooxidative radical transformations of alkynes

During the past few years,electrochemical oxidative reactions through radical intermediates have emerged as an environmentally-benign,powerful platform for the facile formation of C–E(E=C,N,S,Se,O and Hal)bonds through singleelectron-transfer(SET)processes at the electrodes.Functionalized unsaturated molecules and unusual structural motifs can,for instance,be directly constructed under exceedingly mild reaction conditions through initial radical attack onto alkynes.This minireview highlights the recent advances in electrooxidation in radical reactions until June 2022,with a particular focus on radical additions onto alkynes.

Electrolyser design controls position-divergent C–H carboxylation

In recent years,molecular electrochemistry has undergone a remarkable renaissance to surface as a sustainable strategy for organic synthesis and catalysis,gaining considerable momentum by the use of renewable forms of energy[1,2].Modern organic electrochemistry has the unique power to control chemo-,regio-,and position-selectivities through the judicious choice of the electrode material,the applied potential or an additional catalyst,among others[1,2].Despite the major advances in molecular electrochemistry,these approaches continue to predominantly rely on non-renewable fossil resources.

Bifurcated Rhodaelectro-catalyzed C−H Activation for the Synthesis of Pyrroles and Lactones

While electrocatalyzed alkyne annulations of arenes represent a powerful strategy for the assembly of heteroaromatic motives,electrochemical C(sp2)−H activations of alkenes remain scarce.Herein,a strategy for the rhodaelectro-catalyzed function-alization of enamides is presented for the efficient construction of pyrroles using electricity as a sustainable oxidant.Moreover,the tuning of the solvent system allowed a fascinating switch in chemoselectivity,which is not possible with traditionally used chemical oxidants,giving rise to lactone architectures.The rhoda-electrocatalysis features a broad scope as well as high regio-and chemoselectivities.

过渡金属催化的区域选择性芳烃C—H键氧化生成C—O键（英文）

近年来过渡金属催化的芳烃直接C—H氧化反应取得了重要进展,该策略被用于多种酚类化合物的制备.反应体系使用的过渡金属催化剂包括钯、铜、钌、铱等;氧化剂包括高价碘化合物、过硫酸盐、氧气等.此前已有多篇综述就特定的过渡金属或氧化剂参与的C—H氧化反应进行了详尽的讨论.本综述着重探讨过渡金属催化的邻、间、对位选择性的芳烃C—H氧化反应,并试图阐释上述区域选择性的产生机制,其中包括导向基团的螯合辅助作用、配体控制、底物自身因素等.在讨论部分提出了过渡金属催化的芳烃C—H氧化反应中存在的问题以及影响该策略发展应用的可能限制因素.

Cobaltaelectro-Catalyzed C—H Acyloxylation

Cobaltaelectrocatalysis set the stage for sustainable C—H acyloxylations in biomass-derived γ-valerolactone as a renewable solvent. The sustainable electrocatalysis regime featured ample scope, along with high levels of chemo- and position-selectivity.

Rhodaelectro-Catalyzed C–H and C–C Activation

Rhodium(III)catalysis has set the stage for a plethora of oxidative C–H functionalizations over the last decade,which have predominantly employed stoichiometric amounts of toxic and expensive metal oxidants,such as silver(I)salts.In the meantime,electrosynthesis has emerged as an increasingly viable alternative for expensive and toxic oxidants.Recently,significant momentum has been achieved with the merger of electrocatalysis with organometallic C–H activation.However,user-friendly and robust rhodaelectro-catalysis has until very recently proven elusive for oxidative C–H activations.This minireview highlights the current knowledge and recent advances of electrooxidation in rhodium-catalyzed C–H or C–C activations,with a topical focus on contributions from the Ackermann group through July 2020.

Nickela-electrocatalyzed sulfide and phosphine oxygenations with water

Molecular electrochemistry has emerged as an environmentally-friendly platform.While major recent momentum was gained in electrocatalyzed bond activations by earth-abundant 3 d transition metals[1],cost-effective nickela-electrocatalysis continuous to be underdevelopment for electrocatalysis[2].Nickel is an essential component of metalloproteins involved in catalytic aerobic oxygenation processes,for which nickel-dioxygen species were proposed as the key catalytic species[3].

Scalable Rhodaelectro-Catalyzed Expedient Access to Seven-Membered Azepino[3,2,1-hi]indoles via [5+2] C-H/N-H Annulation

We report the establishment of a rhodaelectrocatalyzed[5+2]N-H/C-H oxidative annulation of alkynes by 7-arylindoles,enabling the synthesis of seven-membered azepino[3,2,1-hi]indoles using electricity as the sole oxidant.The reaction could be scaled up to gram-scale by flow-electrocatalysis.Two key rhodium(Ⅲ)intermediates were isolated and fully characterized.Cyclovoltammetric analysis,X-ray photoelectron spectroscopy studies,and density functional theory calculations are suggestive of a rhodium(Ⅲ-Ⅳ-Ⅱ-Ⅲ)manifold.