Photocatalytic Functionalization of Dihydroquinoxalin‐2‐Ones with Pyrazolones

A visible-light photoredox functionalization of 3,4-dihydro-quinoxalin-2-ones with pyrazolones using an inexpensive organophotoredox catalyst is described. The reaction uses 9,10-phenanthrenedione as photocatalyst, a very simple and cheap photocatalyst, a HP single Blue LED (455 nm) as visible-light source and oxygen from air as terminal oxidant, obtaining the corresponding acetylated pyrazoles with good yields. The reaction can be extended to other nitrogen heterocycles such as 5-aminopyrazoles with good results.