Transient Formation of Hydrogen Tetraoxide from Hydrogen Peroxide with Bis(trifluoroacetoxyiodo)benzene: A Chemical Generator of Singlet Oxygen For Organic Synthesis

Abstract

Decomposition of hydrogen tetraoxide, produced by the reaction of hydrogen peroxide with bis(trifluoroacetoxyiodo) benzene, generates singlet molecular oxygen. Oxidation of typical organic substrates in an organic solvent through [4+2] cycloaddition and ene reactions have been carried out on a preparative scale.

Key words

hypervalent Iodine - hydrogen tetraoxide - singlet oxygen - oxygenation - peroxide

References

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General Procedure for Oxidation of α-terpinene(1) with PIFA-H₂O₂ System:
To a solution of 1 (1 mmol)and 35% hydrogen peroxide (6 mmol) in 10 mL of solvent as given in Table [1] at 10 °C was added NaHCO₃ (10 mmol). Then, a freshly prepared solution of PIFA (2.5 mmol relative to 1) in 15 mL of solvent was added over 2-3 h. The suspension was filtered and solvent removed under reduced pressure (5 °C/50 mbar). The residue was extracted with CH₂Cl₂ (2 × 20 mL) and washed with saturated NaHCO₃ (10 mL), and with water (20 mL).The organic layer was dried over MgSO₄ and the solvent was removed at reduced pressure (5 °C/50 mbar). The conversions and product ratios were determined by ¹H NMR analysis directly on the crude mixture in the presence of dimethyl phthalate as internal standard. The products were purified on a silica gel column (40 g) by eluting with hexane-diethyl ether (95:5). First fractions gave iodo-benzene. Further elution afforded ascaridole 2 as a colorless oil.