Photocyclization of Styrylpyrazines

Abstract

Irradiation of several 2-(β-arylvinyl) pyrazines at room temperature using a high pressure mercury lamp afforded aza-phenanthrenes in moderate yields. The ring closure of 2-[β-(3-pyridyl) vinyl] pyrazine (IIIb) occurred only at the 4-position of the pyridine ring, whereas 2-[β-(2-naphthyl) vinyl] pyrazine (IIIe) cyclized at the 1-position of the naphthalene ring. 2, 5-Distyrylpyrazine (VIa) and 2, 5-bis [β-(2-pyridyl) vinyl] pyrazine (VIb) were also irradiated in refluxing benzene to give dibenzo [a, h] phenazine (XVI) and dipyrido [3, 2-α : 3´, 2´-h] phenazine (XVII), respectively.