Electrochemical Palladium-Catalyzed Oxidative Sonogashira Carbonylation of Arylhydrazines and Alkynes to Ynones

Abstract

Oxidative carbonylation using carbon monoxide has evolved as an attractive tool to valuable carbonyl-containing compounds, while mixing CO with a stoichiometric amount of a chemical oxidant especially oxygen is hazardous and limits its application in scale-up synthesis. By employing anodic oxidation, we developed an electrochemical palladium-catalyzed oxidative carbonylation of arylhydrazines with alkynes, which is regarded as an alternative supplement of the carbonylative Sonogashira reaction. Combining an undivided cell with constant current mode, oxygen-free conditions avoids the explosion hazard of CO. A diversity of ynones are efficiently obtained using accessible arylhydrazines and alkynes under copper-free conditions. A possible mechanism of the electrochemical Pd(0)/Pd­(II) cycle is rationalized based upon cyclic voltammetry, kinetic studies, and intermediates experiments.

Photochemical and electrochemical C–N borylation of arylhydrazines

“…For electrochemical borylation, phenyl radical A is formed via the oxidation of 3 on the anode with the aid of n Bu 4 NI. 34 The formation of product 2a from phenyl radical A is consistent with that of the photochemical process. Hydrogen gas evolves from hydrogen protons on the cathode.…”

Electrochemical Site-Selective Alkylation of Azobenzenes with (Thio)Xanthenes

“…In recent years, electrochemical synthesis has received increasing attention for its powerful ability to forge chemical bonds, presumably due to the advantages of no external stoichiometric chemical oxidants or reductants and milder conditions over the conventional approaches [ 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 , 40 ]. As a result, we speculate that electrochemistry maybe provides a unique opportunity to facilitate the functionalization of azobenzene.…”

Multicomponent reactions and photo/electrochemistry join forces: atom economy meets energy efficiency

“…A further methodology for the electrochemical palladiumcatalyzed synthesis of ynones through a Sonogashira carbonylation mechanism was presented this year. 257 Wu and Zeng et al demonstrated the possibility to achieve the carbonylation of alkynes and arylhydrazines in an undivided cell with constant current mode, without the need for external oxidants or oxygen. A carbon felt anode and a graphite rod cathode under 1.5 mA current were employed, leading to a range of valuable ynones.…”