Copper- and Visible-Light-Catalyzed Cascade Radical Cyclization of N-Propargylindoles with Cyclic Ethers

Abstract

An efficient visible-light-assisted, copper-catalyzed tandem radical cyclization of N-propargylindoles with cyclic ethers is established. A series of 2-oxoalkyl-9H-pyrrolo[1,2-a]indol-9-ones with potential biological activities were synthesized in moderate yields by using a dual catalytic system with copper acetate as a transition metal catalyst and eosin Y as a visible light catalyst. The investigation of reaction mechanism shows that it goes through a cascade oxoalkyl radical addition, cyclization, and oxidation process.

Difunctionalization of Dienes, Enynes and Related Compounds via Sequential Radical Addition and Cyclization Reactions

“…In 2022, Du and coworkers developed photoredox radical cyclization of N -propargylindoles for the synthesis of 2-substituted 9 H -pyrrolo-[1,2- a ]indol-9-ones. The photo reaction of N -propargylindoles and cyclic ethers in MeCN at 80 °C in the presence TBHP and dual catalysts Cu(OAc) 2 and Eosin Y give product 82 in moderate yields ( Scheme 82 ) [ 93 ]. The proposed mechanism suggests that a THF radical, generated from the reaction of THF with TBHP and the catalysts, adds to the carbon triple bonds of N -propargylindoles followed by 5- exo cyclization to give intermediate M-48 .…”

Cu-Catalyzed, electron-relayed three-component synthesis of 2-alkenylbenzothiazoles with cathodic ammonia evolution

“…13 The synthesis of 2-substituted benzothiazoles by electrochemical methods can offer new avenues to access natural products and drug molecules. With our persistent interest in green organic synthesis and considering the green characteristics of electrochemical synthesis, 14,15 we report herein a highly atom-economical, multicomponent reaction of 2-aminothiophenols, aldehydes and malononitrile to prepare 2-alkenyl-substituted benzothiazoles through dual electrochemical synthesis and catalysis of transition metals (Scheme 1d).…”