Irradiation of 2-phenyl-1,3-oxazepine (I) with 300 or 350 nm light afforded 3-phenyl-2-oxa-4-azabicyclo[3,2,0]hepta-3,6-diene (II), whereas irradiation of (II) with 250 nm light caused ring opening to give (I).
用300或350 nm的光照射2-苯基-1,3-氧杂氮杂平(I),得到3-苯基-2-氧杂-4-
氮杂双环[3,2,0]庚-3,6-二烯(II),而用250 nm的光照射(II),则开环得到(I)。