Hydrosilane-Mediated Electrochemical Reduction of Amides

Abstract

Electrochemical reduction of amides was achieved by using a hydrosilane without any toxic or expensive metals. The key reactive ketyl radical intermediate was generated by cathodic reduction. Continuous reaction with anodically generated silyl radicals or zinc bromide resulted in chemoselective deoxygenation to give the corresponding amines.

General Concepts and Recent Advances in the Electrochemical Transformation of Chloro‐ and Hydrosilanes

“…Electrochemical conversion of silanes to silanones via a HAT reaction and subsequent oxidation to the silyl cation with consecutive reduction of an amide to an amine as suggested by Chiba and co-workers (top), reaction equation and conditions (bottom, BBD = boron-doped diamond). [170] Scheme 34. Electrochemical HAT mediated oxidation of hydrosilanes to silanols as suggested by Zhang and co-workers (top), reaction equation, conditions, and yield range of some relevant representatives of the electrochemical conversion (bottom, RVC = reticulated vitreous carbon).…”

“…In reference to the reductive synthesis of the Si − O bond to silanones, an oxidative approach is known. Via the hydrosilane mediated electrochemical reduction of amides to amines, the respective Si=O bond is formed as a consecutive reaction [170] . PhSiH 3 is converted to the silyl radical via a bromide mediator with a HAT reaction.…”

“… Electrochemical conversion of silanes to silanones via a HAT reaction and subsequent oxidation to the silyl cation with consecutive reduction of an amide to an amine as suggested by Chiba and co‐workers (top), reaction equation and conditions (bottom, BBD=boron‐doped diamond) [170] …”

“…Via the hydrosilane mediated electrochemical reduction of amides to amines, the respective Si=O bond is formed as a consecutive reaction. [170] PhSiH 3 is converted to the silyl radical via a bromide mediator with a HAT reaction. In parallel, the reduction of the amide occurs, to generate the respective SiÀ C bond via recombination.…”

A guide to organic electroreduction using sacrificial anodes

“…In 2021, the Chiba group reported a hydrosilane-mediated electroreduction of amides under mild reaction conditions (Scheme 37). 70 The reaction is initiated by the cathodic reduction of amide 192 to form radical anion species 194 , followed by SET to generate ketyl radical 195 . Upon trapping by the in situ produced Lewis acid ZnBr 2 , the iminium cation intermediate 196 is reduced by phenylsilane to afford hemiaminal 198 .…”