Photocatalytic Pyridine Synthesis with Enaminones and TMEDA under Metal-Free Conditions.

Reported herein is a new photocatalytic annulation for the synthesis of 2,3,4,6-tetrasubstituted pyridines with enaminones and N,N,N',N '-tetramethyl ethylenediamine (TMEDA). The photocatalytic reactions take place without requiring a transition metal reagent and provide products with broad scope. The methyl in TMEDA acts as the carbon source in pyridine ring construction, and BrCF 2 CO 2 Et plays the role of the terminal oxidant for free radical quenching.