Although previous studies have shown that ocyclic beta,gamma-unsaturat
ed oximes and oxime ethers do not undergo the aza-di-pi-methane (ADPM)
rearrangement, the 2-methyl-4,4-diphenyl-2-vinylbut-3-enal oxine 5a,
its methyl ether 5b and the 2,2,4,4-tetraphenylbut-3-enal oxime 14 giv
e the corresponding cyclopropyl derivatives 8a. 8b and 15 by the ADPM
path, in a reaction that is controlled by the stability of the interme
diate 1,3-biradical.