Advances in regioselective functionalization of 9-phenanthrenols

9-Hydroxyphenanthrene is an important derivative of phenanthrene, which has been used in the fields of organic synthesis, material chemistry, and pharmaceutical chemistry. Phenanthrene is the second most abundant polycyclic aromatic hydrocarbon in coal tar and can be used for large-scale preparation of 9-hydroxyphenanthrene. Due to the lack of strategies, regioselective functionalization of 9-hydroxyphenanthrene is very challenging, especially on C1–C8 sites. In order to promote the application of phenanthrene, this review summarizes the methods for regioselective functionalization of 9-hydroxyphenanthrene and its ether derivatives on different sites. The corresponding reaction mechanisms are introduced in detail. We also provide the reaction characteristics of 9-hydroxyphenanthrene, and we offer our views on the challenges and the future research direction of 9-hydroxyphenanthrene.