2,4,6-Tris(4-methoxyphenyl)pyrylium tetrafluoroborate

2,4,6-Tris(4-methoxyphenyl)pyrylium tetrafluoroborate can be used to catalyze the stereoselective synthesis of C₂-symmetric cyclobutane alkene dimers via photo-induced electron transfer. This method can be employed for the total synthesis of lignans such as magnosalin, endiandrin A and pellucidin A. It can also catalyze photoinduced electron transfer (PET) to initiate radical-cation Diels-Alder reactions.