The substituent effects on the reactivities and the regioselectivities of the title reactions were examined by chromatog. methods. On irradiation by a Hg lamp at l ?02 nm, nitrones, e.g., CHPh:N(O)(CH2)3CH:CH2, gave oxaziridine I. I rearranged further to BzNH(CH2)3CH:CH2 (II) at l ?70 nm. Upon heating, II was transformed back to the nitrone and subsequently cyclized to give III and IV.

Key words: PHOTOCHEMICAL REACTION, SELECTIVITY, PHENYLACRYLIC ACID, OXIME, CYCLOADDITION REACTION, ELECTRONIC EFFECT, MOLECULAR ORBITAL THEORY, TRANSITION STATE THEORY, THERMOCHEMISTRY, SUBSTITUENT EFFECT, STYRENE P, NITRONE