D. Armesto et al., A STUDY ON THE SCOPE OF THE PHOTOCHEMICAL 1,3-MIGRATION OF OXIMINO GROUPS IN BETA,GAMMA-UNSATURATED OXIMES AND OXIMES DERIVATIVES, Journal of the Chemical Society. Perkin transactions. I, (1), 1996, pp. 107-113
While the aza-di-pi-methane rearrangement is the normal photoreactive
behaviour of beta,gamma-unsaturated imines and oxime acetates, the res
ults obtained in this study show that 1,3-migrations of acetoxyimino g
roups in beta,gamma-unsaturated oxime acetates takes place only when a
ll the parameters are correct. The rearrangement takes place when ther
e is a quaternary carbon separating the two pi-systems and when one of
the radical centres in the intermediate cyclobutyl 1,4-biradical is s
tabilized by conjugation with a phenyl ring. Suppression of the free r
otor effect also helps to promote the reaction. These criteria are ful
filled in compounds 1a and 7a. The reaction was extended to the beta,g
amma-unsaturated oximes 1b and 7b where again the 1,3-migration of the
oximino group took place.