Related Experiment Video
Updated: Aug 5, 2026

A Two-Step Protocol for Umpolung Functionalization of Ketones Via Enolonium Species
Published on: August 16, 2018
Copper-catalyzed three-component radical annulation-trifunctionalization of enynones to indenes
Peng-Cheng Xu1,2, Yu-Ting Wang1, Xu Teng3
1School of Safety Science and Engineering, Changzhou University, Changzhou, Jiangsu 213164, P. R. China. zhd0513@cczu.edu.cn.
Abstract:
A copper-catalyzed radical annulation-trifunctionalization of enynones with Togni's reagent and H2O affords trifunctionalized indenes in moderate to good yields. The ligand plays a triple role as a Cu-coordinating agent, a Brønsted base, and a proton shuttle. This method features broad substrate scope, good functional-group tolerance, and high efficiency in ring formation and bond construction, while also being compatible with natural-product frameworks and allowing facile post-synthetic modification.
More Related Videos
Related Concept Videos
Cyclohexenones via Michael Addition and Aldol Condensation: The Robinson Annulation
[4+2] Cycloaddition of Conjugated Dienes: Diels–Alder Reaction
Radical Reactivity: Intramolecular vs Intermolecular
Radical Reactivity: Nucleophilic Radicals
Synthesis of α-Substituted Carbonyl Compounds: The Stork Enamine Reaction
Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

![Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2FCDNSource%2Fteasers%2F60786.jpg&w=3840&q=50)