Mu. Bhaskar et al., DDQ OXIDATION OF 9,10-DIHYDRO-5H-PHENANTHROPYRANS, Indian journal of chemistry. Sect. B: organic chemistry, including medical chemistry, 32(9), 1993, pp. 975-977
Methyl ethers and acetyl derivatives of 9,10-dihydro-5H-phenanthro[4,
5-b, c, d]pyrans are converted in to the corresponding dihydrophenanth
ropyran-5-ones or phenanthropyran-5-ones using varying amounts of DDQ
in refluxing benzene.