Metal-free radical haloazidation of benzene-tethered 1,7-enynes leading to polyfunctionalized 3,4-dihydroquinolin-2(1H)-ones

A new cascade three-component haloazidation of benzene-tethered 1,7-enynes for the formation of biologically interesting azidylated 3,4-dihydroquinolin-2(1H)-ones has been achieved under mild and metal-free conditions using TMSN₃ as a N₃ source and NIS (or NBS or NCS) as a halogen source. The reaction pathway involves in situ-generated azidyl radical-triggered α,β-conjugated addition/6-exo-dig cyclization/radical coupling sequence, resulting in successive multiple bond-forming events, including carbon-nitrogen, carbon-carbon, and carbon-halogen bonds to rapidly construct complex heterocyclic molecules. Furthermore, the resulting products would be useful building blocks in the discovery of lead compounds and other biologically interesting N₃-containing heterocycles.