Photooxygenation of 2-methylnaphtho[2,1-b]furan and 2-methylnaphtho[1,
2-b]furan was carried out in the presence of tetraphenylprophine as a
sensitizer at room temperature to give ortho-hydroxynaphthaldehydes in
good yields; when naphthodifurans (3, 4) were photooxygenated under s
imilar conditions, one or two of the furan rings were opened.