Photo-induced tandem cyclization of 3-iodoflavones with electron rich five-membered heteroarenes

Vinyl radicals were generated from 3-iodoflavones under a mercury lamp and tandem cyclization reactions occurred with five-membered heteroarenes entailing two consecutive C-C bond formations to synthesize benzo[e] chromeno[2,3-g] indol-13(1H)-one derivatives. The tandem cyclization reactions worked in acetonitrile without any additives such as transition metals, ligands and oxidants, giving rise to a broad variety of novel polycyclic xanthone frameworks in good yield under mild and environmentally friendly reaction conditions.