The　observation　of　an　unexpected　oxidative　rearrangement　coupling　reaction　led　to　the　development　of　a　novel　method　for　the　efficient　functionalization　of　tetrahydro-β-carbolines　(THβCs).　The　treatment　of　THβCs　with　photogenerated　singlet　oxygen　(1O2)　afforded　unstable　dioxetanes,　which　underwent　further　transformation　to　form　new　bonds　in　the　presence　of　trifluoroacetic　acid.　This　operationally　simple　protocol　exhibits　broad　functional-group　tolerance　and　is　suitable　for　the　late-stage　functionalization　of　complex　druglike　molecules.　©　2017　Wiley-VCH　Verlag　GmbH　&　Co.　KGaA,　Weinheim.