Synthesis and photooxygenation of angular furocoumarins: isopsedopsoralen and allopsoralen

Abstract Synthesis of 9-methyl-1-phenyl-7 H-furo [3, 2-f] chromen-7-one and 4, 9-dimethyl-3-
phenyl-7 H-furo [2, 3-f] chromen-7-one as angular furocoumarin derivatives were carried out 
through Williamson reaction of hydroxycoumarins with phenacyl bromide followed by 
cyclization in polyphosphoric acid. The photooxygenation of synthesized furocoumarins in 
the presence of tetraphenylporphine as singlet oxygen sensitizer at room temperature gave 
the photo-cleaved product, o-benzoylhydroxy derivatives, through [2+ 2] cycloaddition of  ...