Photoredox Ni-Catalyzed Selective Coupling of Organic Halides and Oxalates to Esters via Alkoxycarbonyl Radical Intermediates

Abstract

A new approach for radical cross coupling of organic halides and oxalates toward esters has been developed via photoredox nickel dual catalysis. This method has been demonstrated for transformation of a wide range of aryl, heteroaryl, alkenyl, and alkyl bromides to various esters under mild conditions. Notably, fluoro-, chloro-, or iodo-substituent on the aryl bromides remains after the coupling reaction, which has been applied for the easy synthesis of drug molecules from simple aryl dihalides. Mechanistic studies indicate that an (alkoxycarbonyl)Ni(I) species might be generated via oxidation of Ni(0) species with an alkoxycarbonyl radical intermediate. Selective alkoxycarbonyl radical coupling over decarboxylative alkyl radical coupling is achieved here.

Pairing Iron and Nickel Catalysis for Electrochemical Esterification of Aryl Halides with Carbazates

“…For example, the groups of Wang and Doyle independently reported photoredox nickel catalysis for the formylation of aryl halides using diethoxyacetic acid and 1,3-dioxolane as the radical formylating reagent precursors, respectively. Quite recently, Xia and co-workers demonstrated the use of alkoxyacyl radicals, generated by photochemical oxidation of oxalates, for photoredox nickel-catalyzed esterification of aryl halides (Scheme B) …”

“…Quite recently, Xia and co-workers demonstrated the use of alkoxyacyl radicals, generated by photochemical oxidation of oxalates, for photoredox nickel-catalyzed esterification of aryl halides (Scheme 1B). 8 Electroorganic synthesis has recently become a rapidly blossoming field of research for redox transformations using inexpensive electric current as a traceless redox agent in a sustainable manner. 9 In essence, electrochemical reaction is always an overall redox-neutral reaction system, and the spatial separation between the anode and cathode, the innate feature of electrochemistry, offers unique opportunities to exploit redox-neutral reactions that would otherwise be challenging to accomplish in a conventional reaction flask setting.…”

Free Carboxylic Acids: The Trend of Radical Decarboxylative Functionalization

“…Li and co‐workers utilized the acyl radicals generated from decarboxylation of keto acids to achieve the synthesis of aryl ketones (Scheme 8a) [32] . In 2022, the group of Xia developed an esterification of aryl halides via the decarboxylative coupling with potassium hemioxalates (Scheme 8b) [33] . The work by Xie and co‐workers added a new entry, thioester, to the toolbox.…”

“…[32] In 2022, the group of Xia developed an esterification of aryl halides via the decarboxylative coupling with potassium hemioxalates (Scheme 8b). [33] The work by Xie and co-workers added a new entry, thioester, to the toolbox. An efficient decarboxylative synthesis of ketones from carboxylic acids and thioesters was devised via Ir/Ni dual catalysis (Scheme 8c).…”

Photoinduced, Silver(I)-Mediated Synthesis of Ester-Substituted Fused Quinazolinones via Cascade Alkoxycarbonylation/Cyclization of Heterocycles Bearing Unactivated Alkenes

“…As illustrated in Scheme , in general, alkoxycarbonyl radicals A can be generated from the corresponding selenides, xanthates, carbazates, oxalates, , and alkyl formates in the presence of toxic tin compounds, an initiator, metal catalysts, oxidants, and peroxides (Scheme a). Recently, Wu, Fu, and Xia disclosed a novel strategy for the generation of alkoxycarbonyl radicals from oxalate derivatives under photoredox catalysis , (Scheme b). A common reaction mode involving alkoxycarbonyl radicals is their addition to unsaturated bonds to generate alkyl radicals, which undergo radical trapping, oxidation, coupling, and other transformations. , However, alkoxycarbonyl radicals have not been used extensively in intermolecular cascade reactions to synthesis complex targets .…”