Visible light-mediated synthesis of quinazolines from 1,2-dihydroquinazoline 3-oxides

A series of quinazolines were synthesized in good to excellent yields by exposing 1,2-dihydroquinazoline 3-oxides to visible light in acetonitrile without the presence of any external sensitizers. The only exception was the 2-(p-nitrophenyl)-substituted substrate, which is insensitive to visible light. This compound could be first oxidized to quinazoline 3-oxide via ruthenium-catalyzed visible light photoredox catalysis, and followed by treating with PCl3 to yield the corresponding quinazoline. The mechanisms of these visible light-mediated reactions were proposed.