Synergistic Tetrabutylammonium Decatungstate/Persulfate Photocatalysis in Pure Water: A Platform for Diversifying Unactivated Alkenes Into N‐Heterocycles

A photocatalytic strategy for the synthesis of N‐heterocycles under mild conditions using water as the reaction medium is described. Leveraging a synergistic tetrabutylammonium decatungstate (TBADT)/Na 2 S 2 O 8 catalytic system in the presence of PEG‐600 under near‐UV irradiation, this method enables the decarboxylative cyclization of oxalamic acids with unactivated alkenes, providing efficient access to 3‐substituted indolines, tetrahydroquinolines, and dihydroquinolinones. Mechanistic studies indicate that TBADT effectively drives the decarboxylation of oxalamic acids under light to generate the key carbamoyl radical. This protocol features mild conditions, operational simplicity, and broad substrate scope, and its utility is demonstrated through the late‐stage diversification of theophylline and a gram‐scale preparation.