Efficient late-stage synthesis of quaternary phosphonium salts from organothianthrenium salts photocatalysis.

Quaternary phosphonium salts (QPS) are significant structural motifs in drugs, materials, and catalysts. Here, a photoactivated approach for the selective late-stage synthesis of QPS utilizing organothianthrenium salts and tertiary phosphines is presented with high yields and broad functional group compatibility. Additionally, the synthetic utility of this protocol is demonstrated by generation of QPS C-H functionalization and its fluorescence confocal imaging of mitochondrial localization in cells.