Photocatalytic\nTricyclization of Enediynes for the\nSynthesis of Chromenoquinolines in Continuous Flow

A photocatalyzed radical-initiated tricyclization of\nenediynes\nwas developed to synthesize a range of hitherto unknown sulfonated\nchromenoquinolines with moderate to excellent yields under continuous\noperational conditions. The reaction mechanism involves a complex\nseries of steps including alkyl radical capture by sulfur dioxide\n(SO<sub>2</sub>), radical addition, 6-<i>exo</i>-<i>dig</i>/6-<i>exo</i>-<i>dig</i>/6-<i>endo</i>-<i>trig</i> tricyclization, and single electron\ntransfer (SET). This cascade of reactions results in the direct formation\nof a pentacyclic framework structure, along with the creation of up\nto three new rings and five chemical bonds in a single step. This\nphotocatalytic protocol exhibits a diverse substrate scope, remarkable\ntolerance to functional groups, and scalable adaptability.