Synthesis, crystal structure and antimalarial activity of novel 1,2,5,6-tetraoxacycloalkanes from 2,3-dihydroperoxy-2-phenylnorbornane

Photooxygenation of 2-phenylnorbornene 1 in the presence of 30% aqueous hydrogen peroxide in acetonitrile afforded the labile 1,2-bis-hydroperoxide 3 which could be cycloalkylated to provide the tricyclic peroxides 5, albeit in low yield, on treatment with silver oxide and a 1,ω-diiodoalkane. Trimethylsilylation of 3, followed by TMSOTf-catalyzed cyclocondensation with carbonyl compounds led to the formation of the tricyclic peroxides 8 containing a 1,2,4,5-tetroxepane structure. The structures of two novel tricyclic peroxides 5a and 8a were unambiguously determined by the X-ray crystallographic analysis.