Photoinduced ring transformation of pyrido-[1,2-b]pyridazinium-4-olate

Article abstract of DOI:10.1016/S0040-4020(01)85009-2

The photolytic behavior of the zwitterionic pyrido[1,2-b]pyridazinium-4- olate (1) was studied. A marked difference was observed depending on the wavelength used: irradiation with a light of λ>280 nm resulted in 3-phenyl- 5-(2-pyridyl)isoxazole (2) and 2-phenyl-3-(2-pyridylcarbonyl)azirine (3) as main products, while the use of light of λ<280 afforded 2-phenyl-5-(2- pyridyl)-oxazole (5) and 1-amino-1-phenyl-3-(2-pyridyl)prop-1-en-3-one (6) as main products. A mechanistic suggestion is provided.