9,10-Phenanthrenedione as Visible-Light Photoredox Catalyst: A Green Methodology for the Functionalization of 3,4-Dihydro-1,4-Benzoxazin-2-ones through a Friedel-Crafts Reaction

Abstract

A visible-light photoredox functionalization of 3,4-dihydro-1,4-benzoxazin-2-ones through a Friedel-Crafts reaction with indoles using an inexpensive organophotoredox catalyst is described. The reaction uses a dual catalytic system formed by a photocatalyst simple and cheap, 9,10-phenanthrenedione, and a Lewis acid, Zn(OTf)2. 5W white LEDs are used as visible-light source and oxygen from air as a terminal oxidant, obtaining the corresponding products with good yields. The reaction can be extended to other electron-rich arenes.

Organophotoredox 1,6-Addition of 3,4-Dihydroquinoxalin-2-ones to para-Quinone Methides Using Visible Light

“…First, we evaluated the reaction using Ru(bpy) 3 Cl 2 as photocatalyst (entry 1). With these conditions, we obtained 43 was used, while product 3aa was not observed when 9,10-phenanthrenedione 44,45 was tested (entry 4 and 5, respectively). Delightfully, we could quantify by 1 H NMR the expected product 3aa in 94% yield after 19 h of irradiation when Fukuzumi's photocatalyst ([Mes-Acr-Me][BF 4 ]) 46 was employed.…”