Transition-Metal-Free Synthesis of Fused Quinazolinones by Oxidative Cyclization of N-Pyridylindoles.

An unprecedented synthesis of fused quinazolinones from N-pyridylindoles under oxidative conditions using a combination of (diacetoxyiodo)benzene and K2S2O8 is reported. The reaction is metal-free, has a broad substrate scope, is operationally simple with short reaction time, and provides 11H-pyrido[2,1-b]quinazolin-11-one derivatives in moderate to high yields. It is believed to proceed via an in situ generated 2-hydroxy-1-(pyridin-2-yl)indolin-3-one as the key reaction intermediate, which undergoes a C-C bond cleavage to produce an electrophilic C-3 site in N-pyridyl indole. Subsequent nucleophilic attack by pyridyl nitrogen results in its cyclization.