[4+4] Photodimerization of Anthracene Derivatives: Recent Synthetic Advances and Applications

The [4+4] photodimerizations of anthracene and its derivatives have been extensively studied for over a century. This classic photochemical reaction features broad substrate scope, user-friendly operation, and controllable reversibility. However, the synthetic applications of anthracene photodimerizations have been underdeveloped thus far, largely because of stereoisomer separation and solubility problems of the dianthracene products. Considering that the dianthracene products display unique molecular rigidity and geometry, further studies to improve the synthetic utility of anthracene photodimerizations should be warranted. This review summarizes the representative works of anthracene photodimerizations since the beginning of the 21st century, highlighting the synthetic. advances to improve the reaction regio- and enanto-selectivity, as well as the synthetic applications toward functional organic molecules and molecular machines.