Fluorinated alcohol directed formation of dispiro-1,2,4,5-tetraoxanes by hydrogen peroxide under acid conditions

The oxidative system MTO/30%H2O2/HBF4/fluorous alcohol is promising for the selective synthesis of biologically important antimalarial dispiro-1,2,4,5-tetraoxanes by direct acid-catalysed cyclisation of various 4-substituted cyclohexanones (, R=Me, Et, tBu, Ph, COOEt, CF3). The role of the substitutent at the 4-position was important in the selectivity of formation of tetraoxane (, TO) with respect to hexaoxonane (, HO). By the use of fluorinated alcohols and under the right reaction conditions, tetraoxanes were selectively formed and synthesised in 46–86% isolated yield from 4-substituted cyclohexanones .