Electrochemical Synthesis of Bisindolylmethanes from Indoles and Ethers

Abstract

An electrochemical bisindolylation of ethers was developed. Carried out under ambient conditions and in the absence of any chemical oxidants, this reaction exhibits a broad substrate scope and good functional group compatibility.

Recent Advances in the Electrochemical Synthesis and Functionalization of Indole Derivatives

“…Huang and co‐workers reported an efficient electrochemical synthesis of bisindolylmethanes 67 from indoles and ethers with LaCl 3 as the catalyst (Scheme ) . The electrochemically generated indole radical cation 69 might undergo a single‐electron transfer process with ether giving a new alkyl radical 70 , which is further trapped by indole to ultimately form the monoindolylated intermediate 72 .…”

Stereoselective synthesis of sulfur-containing β-enaminonitrile derivatives through electrochemical Csp3–H bond oxidative functionalization of acetonitrile

“…Particularly, the indirect electrolysis, in which a redox catalyst is utilized as the electron shuttle, achieves higher energy efficiency and different selectivity 34–43 . In continuation of our interest in the development of electrochemical methods to organic synthesis 44–47 , herein, we report the electrochemical C(sp 3 )–H bond oxidative functionalization of acetonitrile mediated by potassium iodide to synthesize sulfur-containing β-enaminonitrile derivatives highly efficiently in one pot (Fig. 1b).…”

Electrochemical Generation and Use in Organic Synthesis of C‐, O‐, and N‐Centered Radicals

“…a) Li's intermolecular anodic cross‐coupling of xanthenes with azoles [130] . b) Huang's synthesis of bis‐indolylmethanes from indoles and ethers [132] . *No data available to calculate current density.…”

“…Recently, an extension to this work describes the cross‐coupling product between xanthenes and the ketones alpha position [131] . The electrochemical synthesis of bis‐indolylmethanes ( 194 ) can be done from indoles ( 189 ) and cyclic and lineal ethers ( 190 ), through a radical chain reaction initiated in the anode by the N ‐methylindole anodic oxidation (Scheme 20b) [132] . In this reaction, it was proposed that the radical‐cation reaction obtained ( 191 ) acts as a redox mediator, oxidizing the ether and yielding an electrophilic alkyl radical ( 192 ), which undergoes radical substitution reaction with N ‐methylindole after a second electron transfer to the electrode.…”