Metal- and photocatalyst-free C3–H functionalization of quinoxalin-2(1 <i>H</i> )-ones enabled by electron donor–acceptor complex photoactivation

A straightforward, metal- and photocatalyst-free method for the C3-arylation and alkylation of quinoxalin-2(1<i>H</i>)-ones has been developed. This protocol exploits the photoactivation of electron donor-acceptor (EDA) complexes between quinoxalinones and boronic acids, facilitated by <i>p</i>-toluenesulfonic acid. The reaction proceeds under mild conditions (violet LED irradiation, air atmosphere) and exhibits broad substrate scope, accommodating a wide range of quinoxalinones and (hetero)aryl/alkyl boronic acids to deliver the products in moderate to excellent yields. Mechanistic studies confirm the involvement of a radical pathway and the critical role of the EDA complex. The practicality of this method is demonstrated by its scalability and successful late-stage functionalization of drug-like molecules.