A singlet oxygen approach to oxaspirocycles

A method for the preparation of oxygen containing spirocycles using singlet oxygen is reported. A series of phenols were converted into the corresponding peroxy-cyclohexadienone derivatives by irradiation with visible light in the presence of a sensitizer and oxygen. The resulting peroxides could be converted into ether and lactone spirocycles in one or two steps. The synthesis of the oxaspirocycles from the phenols can also be performed in a one-pot fashion, avoiding the isolation of the peroxide intermediates.