Selective transformation of 3-acetyl-5-aryl-2-methylfurans using photooxygenation

The photooxyenation of 3-acetyl-5-aryl-2-methylfurans was carried out in ac etonitrile through a dry air stream in the presence of Rose Bengal to give 2,2-diacetyl-3-aroyloxiranes via the corresponding endo-peroxide intermedia te. while the 3-acetyl-1-aryl-2-pentene-1,4-diones were formed when the rea ction mixture was poured into water after the photooxygenation. The direct irradiation of 3-acetyl-5-aryl-2-methylfurans using UV light through a dry air stream afforded the 3-acetyl-1-aryl-2-hydroxy-2-pentene-1,4-diones.