Phosphomolybdic acid (PMA) and phosphotungstic acid (PTA) efficiently catalyze the addition of H2O2 to β-diketones to form bridged 1,2,4,5-tetraoxanes. These reactions are not accompanied by the formation of monocyclic peroxides containing hydroxy and hydroperoxide groups or polymeric peroxides. The use of these catalysts made it possible to obtain bridged tetraoxanes from easily oxidizable benzoylacetone derivatives and α-unsubstituted β-diketones. The syntheses are scaled up to ten grams. The resulting peroxides can be easily isolated from the reaction mixture by column chromatography. The yield of tetraoxanes depends on the structure of β-diketone and varies from 12 to 83%. NMR monitoring of two bridged 1,2,4,5-tetraoxanes synthesis was carried out.