Novel photo-rearrangement of 1,5-di(p-methoxyphenyl)-6,7-dioxabicyclo[3.2.2]nonane through an O-neophyl-type 1,2-aryl shift: evidence for a 1,6-dioxyl diradical intermediate

Photolysis and thermolysis of 1,5-diaryl-6,7-dioxabicyclo[3.2.2]nonane 1a–c (a: Ar=p-MeOC6H4, b: Ar=p-MeC6H4, c: Ar=Ph) were investigated. (p-Methoxyphenyl)-substituted 1a underwent a novel photo-initiated O-neophyl-type 1,2-aryl shift to afford 1-(p-methoxyphenyl)oxy-5-(p-methoxyphenyl)-8-oxabicyclo[3.2.1]octane 7a along with a small amount of 1-(p-methoxyphenyl)-3-(2-(4′-methoxyphenyl)tetrahydrofuran-2-yl)propan-1-one 4a through an 1,6-dioxyl diradical intermediate, while the thermolysis mainly afforded the 1,5-di(p-methoxyphenyl)pentan-1,5-dione 5a and 1,4-di(p-methoxyphenyl)butan-1,4-dione 8a.