A Rearrangement of 4-Phenylbenzo[d]oxazoles to Phenanthridin-4-ols

A new approach was developed for the synthesis of phenanthridin-4-ols and 4-hydroxyphenanthridin-6(5H)-one derivatives in 43-89% yields based on the AlCl3-mediated rearrangement of available 4-phenylbenzo[d]oxazoles and 4-phenyl-1,3-benzoxazol-2(3H)-one. The quantum chemical calculations were used to describe the mechanism and predict the thermodynamic parameters of the reaction under study.