Synthesis, Fe(II)-induced degradation, and antimalarial activities of 1,5-diaryl-6,7-dioxabicyclo[3.2.2]nonanes: Direct evidence for nucleophilic O-1,2-aryl shifts

1,5-Diaryl-6,7-dioxabicyclo[3.2.2]nonanes 1a-d (1a: Ar=p-FC₆H₄, 1b: Ar=Ph, 1c: Ar=p-MeC₆H₄, 1d: Ar=p-MeOC₆H₄) were prepared by a modified method of photo-electron transfer oxygenation, and the reactions of 1 with FeBr₂ were investigated under various conditions. The Fe(II)-induced degradation of 1 afforded various rearrangement products and fragmentation products through competitive single electron transfer (SET) and Lewis acid pathways. Direct evidence for the O-1,2-aryl shift was obtained by the isolation of rearrangement products, 1-aryloxy-5-aryl-8-oxabicyclo[3.2.1]octanes 8. The degradation mechanism was proposed and the in vitro antimalarial activities were also evaluated.