The synthesis of 1,3-dipolar nitrone (I) and its thermochem. and photochem. reactions have been investigated. The intramol. cycloaddn. is regioselective and the cyclization products are II and III in roughly 2:1 ratio (total yield 80%). The thermochem. reaction under sunlamp light also produces the double bond migration product IV (18%). The photochem. reaction of I under irradiation at l ?02 nm gives oxaziridine V (78%), while under l ?70 nm the rearrangement product VI (15%) is obtained directly besides V (43%). Compound V is very reactive and undergoes an intramol. cycloaddn. reaction through I on heating.

Key words: PHOTOCHEMICAL REACTION, REACTION MECHANISM, NITROGEN HETEROCYCLICS, SELECTIVITY, FURAN P, REARRANGEMENT REACTION, OXIME, CYCLOADDITION REACTION, OXYGEN HETEROCYCLICS, ENERGY LEVELS