Visible-Light-Initiated Oxidative Coupling of Indole and Active Methylene Compounds Using Eosin Y as a Photocatalyst

Abstract

A novel, efficient, mild, and inexpensive photocatalytic approach has been established for the visible-light-initiated oxidative coupling of indole and active methylene compounds using atmospheric air and water as an oxidant in the presence of Eosin Y to give 3-methyleneindolin- 2-ones. In this work, only one molecule of malononitrile, ethyl acetoacetate, or dimedone reacts with one molecule of indole, but, in contrast, two molecules of barbituric acid react with one molecule of indole. The essential features of this approach are metal-free reaction, high yield of the products, no side product, and use of renewable energy sources. © 2022. Thieme. All rights reserved.