Catalyst‐Free Decarboxylation of Carboxylic Acids and Deoxygenation of Alcohols by Electro‐Induced Radical Formation

Abstract

Electro‐induced reduction of redox active esters and N‐phthalimidoyl oxalates derived from naturally abundant carboxylic acids and alcohols provides a sustainable and inexpensive approach to radical formation via undivided electrochemical cells. The resulting radicals are trapped by an electron‐poor olefin or hydrogen atom source to furnish the Giese reaction or reductive decarboxylation products, respectively. A broad range of carboxylic acid (1°, 2°, and 3°) and alcohol (2° and 3°) derivatives are applicable in this catalyst‐free reaction, which tolerated a diverse range of functional groups. This method features simple operation, is a sustainable platform, and has broad application.

Ynonylation of Acyl Radicals by Electroinduced Homolysis of 4-Acyl-1,4-dihydropyridines

“…We envisioned that an electrochemical generation of acyl and carbamoyl radicals might be a new activation mode for the preparation of more complex ynones with much milder conditions and broader functional group tolerance . Electrochemistry, which enables a wide application of radical generation under milder conditions, can generate highly reactive intermediates under an applied potential without experiencing an excited state, such as alkene functionalization, cyclization, bond construction (C–N, C–O, C–C), and other diverse reactions . Despite this progress, the electrochemical construction of C sp 2 (O)–C sp bonds remains elusive.…”

Direct decarboxylative Giese reactions

“…Wang and co-workers have recently reported using electrochemistry for the indirect DGR of NHPI esters, which proceeds through a reductive decarboxylation mechanism. 152…”

Radical Deoxyfunctionalisation Strategies

“…In 2020, Wang and co-workers developed an electro-mediated decarboxylative and deoxygenative Giese-type reaction, using N-phthalimidoyl oxalates as radical precursors (Scheme 15). [27] Upon electrochemical reduction via reticulated vitreous carbon (RVC) electrode, these redox-active esters (RAEs) are coupled with a wide range of Michael acceptors. Whilst the reaction provides the targeted products from tertiary N-phthalimidoyl oxalates at room temperature, a slight increase of voltage and temperature is required for reactions with secondary and primary derivatives.…”