REACTION OF SINGLET OXYGEN WITH ENOLIC TAUTOMERS OF 1-ARYL-2-METHYL 1,3-DIKETONES

The 1-(2',4',6'-trialkylphenyl)-2-methyl 1,3-diketones 6 exist in the enol form in solution, and on reaction with singlet oxygen in acetonit rile give products arising from hydrogen abstraction from both the eno lic hydroxy and the 2-methyl groups by the singlet oxygen; namely the 2-hydroperoxy 1,3-diketones 7, the 2-methylene 1,3-diketones 8 and the epoxy ketones 9, The 2-hydroperoxy 1,3-diketones 7 readily undergo de oxygenation by triphenylphosphine to give the 2-hydroxy 1,3-diketones 12, In the reaction of 6 in methanol or ethanol, the initially formed enedione 8 reacts with the solvent to give the corresponding Michael a dducts 10 and 11.