Photochemical electrocyclization of the indolinylphenylethenes involving a C-N bond formation.

[reaction: see text] A novel oxidative photodehydrocyclization of indolinylphenylethenes to a polycyclic heteroaromatic cation with good yields was described. Starting from the trans derivative, the phototransformation is a multistep process. The process includes two photochemical reactions and a trans-cis isomerization reaction, followed by an 1-aza-1,3,5-hexatrienic electrocyclic reaction involving the formation of a C-N bond. The cyclized product gives the stable heteroaromatic cations from hydride elimination with oxygen from air or iodine.