Synthesis of two quinolines from one substrate: The beginning of regulating the duality of free radicals

Poly-substituted quinolines are scaffolds with diverse applications as pharmaceuticals, agrochemicals, electroluminescent materials, and dyestuffs. Herein, we present an effective scheme for the green synthesis of two multiply substituted quinoline derivatives from a singular substrate via regulating free-radical duality. Photo-catalytically generated imine radicals can undergo intramolecular Michael addition (nucleophilic 1,4-addition) to produce 3,4-disubstituted quinolines via a novel rearrangement in the presence of an inorganic base. Alternatively, they can react via an intramolecular anti-Michael addition (electrophilic 1,3-addition) in the presence of an organic base to furnish 2,3-disubstituted quinolines. The high-atom economy, good yields, mild reaction condition, simple experimental setup of this methodology, will prompt the development of Poly-substituted quinolines and other heterocycles synthesis via using intramolecular Michael addition and anti-Michael addition of free radicals. Moreover, our results suggests the theory that the electrophilic / nucleophilic bias of free radicals is determined by their structure is incomplete, the electrophilic/nucleophilic bias can be regulated by altering the reaction conditions, which can improve the efficiency of divergent synthesis.