Electrochemical Deoxygenative Barbier-Type Reaction

Abstract

An effective deoxygenative C­(sp3)–C­(sp3) bond formation reaction is achieved through electrochemical reduction of alcoholic phosphates or sulfonates with aldehydes or ketones. Alcohol derivatives of phosphates undergo single-electron reduction under electrochemical conditions followed by a spontaneous cleavage of the C–O bond with the exothermic loss of phosphate resulting in an alkyl radical species. Subsequently, radical intermediates are further reduced to carbanions at the cathode, which are in situ trapped by carbonyl compounds, thus accomplishing a deoxygenative Barbier-type reaction.

Recent advances in electrochemical deoxygenation reactions of organic compounds

“…Hence, in 2022 Tian and Wang's group developed an electrochemical deoxygenation Barbier reaction under simple reaction conditions and high functional group tolerance using the phosphate derivative of alcohols (Scheme 12). 43 The reactions work well for various substituted benzaldehyde allyl aldehydes and aliphatic aldehydes. It is interesting to note that aromatic cyclic ketones and acetophenones are also compatible with this reaction.…”

Electrosynthetic C−O Bond Activation in Alcohols and Alcohol Derivatives

“…[41,[201][202][203] Recently, Tian and Wang and co-workers demonstrated that aliphatic phosphate esters can undergo electrochemical deoxygenative C(sp 3 )À C(sp 3 ) couplings with aldehydes and ketones to furnish alcohol products. [204] Mechanistically, it was proposed that dissociative electron transfer to the phosphate ester furnishes an aliphatic radical that undergoes a second electron transfer to form the carbanion. This species would attack the carbonyl carbon of the coupling partner in a Barbier-like sequence and form the alcohol upon protonation.…”

“…The cleavage was postulated to proceed via two initial single‐electron transfers to the phosphate ester to afford a phosphate anion and a carbanion, followed by protonation of the latter to afford the hydrocarbon product [41, 201–203] . Recently, Tian and Wang and co‐workers demonstrated that aliphatic phosphate esters can undergo electrochemical deoxygenative C(sp 3 )−C(sp 3 ) couplings with aldehydes and ketones to furnish alcohol products [204] . Mechanistically, it was proposed that dissociative electron transfer to the phosphate ester furnishes an aliphatic radical that undergoes a second electron transfer to form the carbanion.…”

Electrosynthetic C−O Bond Activation in Alcohols and Alcohol Derivatives

“…[ 41 , 201 , 202 , 203 ] Recently, Tian and Wang and co‐workers demonstrated that aliphatic phosphate esters can undergo electrochemical deoxygenative C(sp 3 )−C(sp 3 ) couplings with aldehydes and ketones to furnish alcohol products. [204] Mechanistically, it was proposed that dissociative electron transfer to the phosphate ester furnishes an aliphatic radical that undergoes a second electron transfer to form the carbanion. This species would attack the carbonyl carbon of the coupling partner in a Barbier‐like sequence and form the alcohol upon protonation.…”